JP3804812B2 - Method for producing insulating varnish - Google Patents
Method for producing insulating varnish Download PDFInfo
- Publication number
- JP3804812B2 JP3804812B2 JP09629997A JP9629997A JP3804812B2 JP 3804812 B2 JP3804812 B2 JP 3804812B2 JP 09629997 A JP09629997 A JP 09629997A JP 9629997 A JP9629997 A JP 9629997A JP 3804812 B2 JP3804812 B2 JP 3804812B2
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- Prior art keywords
- resin
- copper foil
- adhesive film
- whisker
- thickness
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 239000002966 varnish Substances 0.000 title claims description 35
- 238000004519 manufacturing process Methods 0.000 title claims description 11
- 229920005989 resin Polymers 0.000 claims description 86
- 239000011347 resin Substances 0.000 claims description 86
- 238000000034 method Methods 0.000 claims description 11
- 239000000835 fiber Substances 0.000 claims description 9
- 239000004677 Nylon Substances 0.000 claims description 4
- 229920001778 nylon Polymers 0.000 claims description 4
- 239000000919 ceramic Substances 0.000 claims description 3
- 239000010410 layer Substances 0.000 description 110
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 89
- 239000002313 adhesive film Substances 0.000 description 78
- 239000011889 copper foil Substances 0.000 description 69
- 238000005530 etching Methods 0.000 description 41
- 238000012360 testing method Methods 0.000 description 40
- 239000011521 glass Substances 0.000 description 39
- 239000003822 epoxy resin Substances 0.000 description 34
- 229920000647 polyepoxide Polymers 0.000 description 34
- 239000004744 fabric Substances 0.000 description 31
- 230000007797 corrosion Effects 0.000 description 29
- 238000005260 corrosion Methods 0.000 description 29
- IISBACLAFKSPIT-UHFFFAOYSA-N bisphenol A Chemical compound C=1C=C(O)C=CC=1C(C)(C)C1=CC=C(O)C=C1 IISBACLAFKSPIT-UHFFFAOYSA-N 0.000 description 28
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 21
- 229920002799 BoPET Polymers 0.000 description 21
- 229910052802 copper Inorganic materials 0.000 description 20
- 239000010949 copper Substances 0.000 description 20
- 239000004593 Epoxy Substances 0.000 description 18
- 229920003986 novolac Polymers 0.000 description 18
- 238000005553 drilling Methods 0.000 description 15
- 238000007731 hot pressing Methods 0.000 description 14
- 239000000758 substrate Substances 0.000 description 13
- 238000005452 bending Methods 0.000 description 12
- 239000011810 insulating material Substances 0.000 description 12
- 239000012790 adhesive layer Substances 0.000 description 11
- 238000009413 insulation Methods 0.000 description 11
- OJMOMXZKOWKUTA-UHFFFAOYSA-N aluminum;borate Chemical compound [Al+3].[O-]B([O-])[O-] OJMOMXZKOWKUTA-UHFFFAOYSA-N 0.000 description 10
- 230000008569 process Effects 0.000 description 10
- 230000003746 surface roughness Effects 0.000 description 10
- 238000000465 moulding Methods 0.000 description 9
- 238000000576 coating method Methods 0.000 description 8
- 238000007772 electroless plating Methods 0.000 description 8
- 230000035939 shock Effects 0.000 description 8
- 229910000679 solder Inorganic materials 0.000 description 8
- 239000002253 acid Substances 0.000 description 7
- 239000003795 chemical substances by application Substances 0.000 description 7
- 238000005336 cracking Methods 0.000 description 7
- 239000002904 solvent Substances 0.000 description 7
- PXKLMJQFEQBVLD-UHFFFAOYSA-N bisphenol F Chemical compound C1=CC(O)=CC=C1CC1=CC=C(O)C=C1 PXKLMJQFEQBVLD-UHFFFAOYSA-N 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 6
- 238000012545 processing Methods 0.000 description 6
- SMQUZDBALVYZAC-UHFFFAOYSA-N salicylaldehyde Chemical compound OC1=CC=CC=C1C=O SMQUZDBALVYZAC-UHFFFAOYSA-N 0.000 description 6
- 239000007787 solid Substances 0.000 description 6
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 description 5
- 239000012298 atmosphere Substances 0.000 description 5
- 238000011049 filling Methods 0.000 description 5
- 239000011229 interlayer Substances 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 238000002156 mixing Methods 0.000 description 5
- ULKLGIFJWFIQFF-UHFFFAOYSA-N 5K8XI641G3 Chemical compound CCC1=NC=C(C)N1 ULKLGIFJWFIQFF-UHFFFAOYSA-N 0.000 description 4
- 230000000903 blocking effect Effects 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 239000007822 coupling agent Substances 0.000 description 4
- 238000005520 cutting process Methods 0.000 description 4
- 239000003085 diluting agent Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 4
- 238000013001 point bending Methods 0.000 description 4
- -1 zircoaluminum Chemical compound 0.000 description 4
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 3
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 239000004020 conductor Substances 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- 230000001771 impaired effect Effects 0.000 description 3
- 238000003475 lamination Methods 0.000 description 3
- 239000005011 phenolic resin Substances 0.000 description 3
- 229920000139 polyethylene terephthalate Polymers 0.000 description 3
- 239000005020 polyethylene terephthalate Substances 0.000 description 3
- 229920001187 thermosetting polymer Polymers 0.000 description 3
- JYEUMXHLPRZUAT-UHFFFAOYSA-N 1,2,3-triazine Chemical compound C1=CN=NN=C1 JYEUMXHLPRZUAT-UHFFFAOYSA-N 0.000 description 2
- XQUPVDVFXZDTLT-UHFFFAOYSA-N 1-[4-[[4-(2,5-dioxopyrrol-1-yl)phenyl]methyl]phenyl]pyrrole-2,5-dione Chemical compound O=C1C=CC(=O)N1C(C=C1)=CC=C1CC1=CC=C(N2C(C=CC2=O)=O)C=C1 XQUPVDVFXZDTLT-UHFFFAOYSA-N 0.000 description 2
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 2
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000000805 composite resin Substances 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- QGBSISYHAICWAH-UHFFFAOYSA-N dicyandiamide Chemical compound NC(N)=NC#N QGBSISYHAICWAH-UHFFFAOYSA-N 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000003365 glass fiber Substances 0.000 description 2
- 150000004820 halides Chemical class 0.000 description 2
- LNEPOXFFQSENCJ-UHFFFAOYSA-N haloperidol Chemical compound C1CC(O)(C=2C=CC(Cl)=CC=2)CCN1CCCC(=O)C1=CC=C(F)C=C1 LNEPOXFFQSENCJ-UHFFFAOYSA-N 0.000 description 2
- RAXXELZNTBOGNW-UHFFFAOYSA-N imidazole Natural products C1=CNC=N1 RAXXELZNTBOGNW-UHFFFAOYSA-N 0.000 description 2
- 238000010030 laminating Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000013508 migration Methods 0.000 description 2
- 230000005012 migration Effects 0.000 description 2
- 229920003192 poly(bis maleimide) Polymers 0.000 description 2
- 229920001721 polyimide Polymers 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 230000003014 reinforcing effect Effects 0.000 description 2
- 238000007788 roughening Methods 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- MCTWTZJPVLRJOU-UHFFFAOYSA-N 1-methyl-1H-imidazole Chemical compound CN1C=CN=C1 MCTWTZJPVLRJOU-UHFFFAOYSA-N 0.000 description 1
- XNWFRZJHXBZDAG-UHFFFAOYSA-N 2-METHOXYETHANOL Chemical compound COCCO XNWFRZJHXBZDAG-UHFFFAOYSA-N 0.000 description 1
- QTWJRLJHJPIABL-UHFFFAOYSA-N 2-methylphenol;3-methylphenol;4-methylphenol Chemical compound CC1=CC=C(O)C=C1.CC1=CC=CC(O)=C1.CC1=CC=CC=C1O QTWJRLJHJPIABL-UHFFFAOYSA-N 0.000 description 1
- VPWNQTHUCYMVMZ-UHFFFAOYSA-N 4,4'-sulfonyldiphenol Chemical compound C1=CC(O)=CC=C1S(=O)(=O)C1=CC=C(O)C=C1 VPWNQTHUCYMVMZ-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- JPVYNHNXODAKFH-UHFFFAOYSA-N Cu2+ Chemical compound [Cu+2] JPVYNHNXODAKFH-UHFFFAOYSA-N 0.000 description 1
- 239000004640 Melamine resin Substances 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- NTIZESTWPVYFNL-UHFFFAOYSA-N Methyl isobutyl ketone Chemical compound CC(C)CC(C)=O NTIZESTWPVYFNL-UHFFFAOYSA-N 0.000 description 1
- UIHCLUNTQKBZGK-UHFFFAOYSA-N Methyl isobutyl ketone Natural products CCC(C)C(C)=O UIHCLUNTQKBZGK-UHFFFAOYSA-N 0.000 description 1
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 229920001665 Poly-4-vinylphenol Polymers 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 239000006087 Silane Coupling Agent Substances 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 125000002723 alicyclic group Chemical group 0.000 description 1
- 150000001413 amino acids Chemical class 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 229910001431 copper ion Inorganic materials 0.000 description 1
- 229930003836 cresol Natural products 0.000 description 1
- 239000003431 cross linking reagent Substances 0.000 description 1
- 239000004643 cyanate ester Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 125000005442 diisocyanate group Chemical group 0.000 description 1
- NJLLQSBAHIKGKF-UHFFFAOYSA-N dipotassium dioxido(oxo)titanium Chemical compound [K+].[K+].[O-][Ti]([O-])=O NJLLQSBAHIKGKF-UHFFFAOYSA-N 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000010292 electrical insulation Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 239000003063 flame retardant Substances 0.000 description 1
- WJRBRSLFGCUECM-UHFFFAOYSA-N hydantoin Chemical compound O=C1CNC(=O)N1 WJRBRSLFGCUECM-UHFFFAOYSA-N 0.000 description 1
- 229940091173 hydantoin Drugs 0.000 description 1
- 150000004678 hydrides Chemical class 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 239000012948 isocyanate Substances 0.000 description 1
- 150000002513 isocyanates Chemical class 0.000 description 1
- ZFSLODLOARCGLH-UHFFFAOYSA-N isocyanuric acid Chemical compound OC1=NC(O)=NC(O)=N1 ZFSLODLOARCGLH-UHFFFAOYSA-N 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 1
- 235000019341 magnesium sulphate Nutrition 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000006082 mold release agent Substances 0.000 description 1
- 150000002903 organophosphorus compounds Chemical class 0.000 description 1
- AFEQENGXSMURHA-UHFFFAOYSA-N oxiran-2-ylmethanamine Chemical compound NCC1CO1 AFEQENGXSMURHA-UHFFFAOYSA-N 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229920006267 polyester film Polymers 0.000 description 1
- 239000009719 polyimide resin Substances 0.000 description 1
- 150000003242 quaternary ammonium salts Chemical class 0.000 description 1
- 239000011342 resin composition Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 150000003512 tertiary amines Chemical class 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 229920006337 unsaturated polyester resin Polymers 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
- 229910052882 wollastonite Inorganic materials 0.000 description 1
- 239000010456 wollastonite Substances 0.000 description 1
- 239000008096 xylene Substances 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Landscapes
- Production Of Multi-Layered Print Wiring Board (AREA)
- Laminated Bodies (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Paints Or Removers (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、絶縁ワニスの製造方法に関するものである。
【０００２】
【従来の技術】
プリント配線板は、通常、銅箔とプリプレグを積層、熱圧成形して得た銅張積層板に回路加工して得られる。
また、多層プリント配線板は、これれらのプリント配線板同士をプリプレグを介して熱圧成形するか又は、これれらのプリント配線板と銅箔とをプリプレグを介して熱圧成形して一体化して得た内層回路入り多層銅張積層板の表面に回路を形成して得られる。
【０００３】
プリント配線板用のプリプレグには、従来、ガラスクロスに樹脂を含浸・乾燥し、樹脂を半硬化状態にしたガラスクロスプリプレグが用いられ、多層プリント配線板には、該ガラスクロスプリプレグの他に、特開平６−２００２１６号公報や特開平６−２４２４６５号公報に記載されているような、ガラスクロスを用いないプリプレグであるフィルム形成能を有する樹脂を半硬化状態にした接着フィルムや、特開平６−１９６８６２号公報に記載されているような、接着フィルムを銅箔の片面に形成した銅箔付き接着フィルムが使用されている。
なお、ここでいうフィルム形成能とは、プリプレグの搬送、切断及び積層等の工程中において、樹脂の割れや欠落等のトラブルを生じにくく、その後の熱圧成形時に層間絶縁層が内層回路存在部等で異常に薄くなったり層間絶縁抵抗低下やショートというトラブルを生じにくい性能を意味する。
【０００４】
【発明が解決しようとする課題】
近年、電子機器の小型軽量化、高性能化、低コスト化が進行し、プリント配線板には高密度化、薄型化、高信頼性化、低コスト化が要求されている。
高密度化のためには、微細配線が必要であり、そのためには表面の平坦性が良好でかつ、寸法安定性が良好でなくてはならない。さらに微細なスルーホールやインターステーシャルバイアホール（ＩＶＨ）が必要であり、ドリル加工性、レーザ穴加工性が良好であることが要求されている。表面の平坦性を良好にするためには、多層化積層成形時の樹脂の流動性を高くする必要があり、これにはエポキシ樹脂等の熱硬化性樹脂の適用が望ましい。
【０００５】
ところが、エポキシ樹脂は、成形前の段階の分子量が低いために高い流動性を示しており、シート状の絶縁材料を形成する性質を有していない。そこで、従来はガラスクロス等の補強基材に絶縁樹脂を含浸させたプリプレグをあらかじめ作製し、これを絶縁層に用いてきたが、従来のプリプレグでは上記の要求への対応が困難になってきた。
現在、プリプレグ用に一般的に使用されているガラスクロスは、その厚みが薄くなるに従いヤーン（ガラス繊維束）同士の間の隙間が大きくなる。そのため、厚みが薄いクロスほど目曲がり（ヤーンが曲がったり、本来直角に交差すべき縦糸と横糸が直角でなく交差する現象）が発生しやすくなる。この目曲がりが原因となり、熱圧成形後に異常な寸法変化やそりを生じやすくなる。さらに薄いガラスクロスほどヤーン間の隙間が大きいためプリプレグの繊維の体積分率が低くなるため層間絶縁層の剛性が低下する。そのため外層の回路を加工した後の部品実装工程等においてたわみが大きくなりやすく問題となっている。
現在、一般に使用されているガラスクロスで最も薄いのは３０μmのクロスであり、これを使用したプリプレグの厚さは４０μm程度になる。これ以上にプリプレグの厚さを薄くするために、樹脂分を減らすと内層回路の凹凸への樹脂による穴埋め性が低下しボイドが発生する。またこれ以上にガラスクロスを薄くするとクロス自体の強度が低下するためガラスクロスに樹脂を含浸する工程でガラスクロスが破断しやすなりプリプレグの製造が困難になる。さらに、これらのガラスクロスを使用したプリプレグを用いて作製した多層プリント配線板は、小径ドリル加工時に偏在するガラスクロスによって芯ぶれがしやすく、ドリルを折りやすい。また、ガラス繊維の存在のため、レーザによる穴あけ性が悪く、内層回路の凹凸が表面に現れやすく表面平坦性が悪い。したがって、現状のガラスクロス基材のプリプレグを使用しては、高まる多層プリント配線板の高密度化、薄型化の要求に対応出来ない状況にある。
【０００６】
一方、ガラスクロスのないプリプレグである接着フィルムや銅箔付き接着フィルムは、厚さをより薄くでき、小径ドリル加工性、レーザ穴加工性及び表面平坦性に優れる。しかしながら、これらのプリプレグで作製した多層プリント配線板は、外層絶縁層にガラスクロス基材がないため、剛性が極めて低い。この剛性の低さは、高温下において極めて顕著であり、部品実装工程においてたわみが生じやすく、ワイヤーボンディング性も極めて悪い。また外層絶縁層にガラスクロス基材がなく熱膨張係数が大きいため実装部品との熱膨張の差が大きく、実装部品との接続信頼性が低く、加熱冷却の熱膨張収縮によるはんだ接続部にクラックや破断が起こり易い等多くの問題を抱える。したがって、現状のガラスクロスのないプリプレグである接着フィルムや銅箔付き接着フィルムを使用しては、高まる多層プリント配線板の高密度化、薄型化の要求に対応出来ない状況にある。
【０００７】
そこで、従来のプリプレグでは解決できない多層プリント配線板に対する高密度化、薄型化、高信頼性化、低コスト化という課題を解決するための新規絶縁材料として、ガラスクロス等の基材を含まず、形状保持のための電気絶縁性ウイスカーを絶縁樹脂中に分散させることにより得られるワニスをキャリア基材に流延して得られるシート状の絶縁材料が有効であることを見出してきた。
【０００８】
しかし、電気絶縁性ウイスカーは乾燥状態で凝集する性質が有り、電気絶縁性ウイスカーを絶縁樹脂中に分散させるためには、特殊な混練設備が必要であったり、電気絶縁性ウイスカーの表面処理を適切に行うことが必要になるが、そのような対策を施しても電気絶縁性ウイスカーの凝集体を皆無にすることができないという課題があった。
【０００９】
また、多層プリント配線板において、内層回路充填性確保のために絶縁層の厚さを内層回路の厚さ以上に設定しているが、多層プリント配線板の全体厚を薄くするためには、絶縁性を確保できる範囲で可能な限り薄くすることが望まれているので、絶縁層の厚さを２５〜１００μｍとするのが通常であり、最低でも２５μｍとしている。ところで、電気絶縁性のウイスカーの凝集体のサイズ（長さ）は、市販のものを平均長さ３０μｍと指定して購入したときに、長いものは５０μｍを超え、中には３００μｍを超えるものもあった。このような電気絶縁性ウイスカーを用いたシート状絶縁材料を多層配線板に適用した場合には、その長い電気絶縁性のウイスカーや、前記の凝集した電気絶縁性のウイスカーを含んだワニスを用いることとなり、導体間に、長い電気絶縁性のウイスカーや電気絶縁性ウイスカーの凝集体が接触し、ＣＡＦ（Ｃｏｎｄｕｃｔｉｖｅ Ａｎｏｄｉｃ Ｆｉｌａｍｅｎｔ）に類似した絶縁不良を起こすという課題がある。
【００１０】
本発明は、電気絶縁性に優れた絶縁ワニスの製造方法を提供することを目的とする。
【００１１】
【課題を解決するための手段】
本発明の絶縁ワニスの製造方法は、電気絶縁性ウイスカーを含む樹脂ワニスをフィルタを通して精製することを特徴とする。
【００１２】
この電気絶縁性ウイスカーには、セラミックウイスカーで、該ウイスカーの平均直径、０．３〜３．０μｍの範囲にあり、平均長さが３〜５０μｍであるものを用いることが好ましく、この場合に、フィルタには、その空隙が、５０〜１００μｍであるものを用いることが好ましく、Ｔｙｌｅｒの１７０〜２７０メッシュのものを用いることがより好ましい。
【００１３】
【発明の実施の形態】
（ウィスカー）
本発明に用いるウィスカーとしては、電気絶縁性のセラミックウィスカーであり、弾性率が２００ＧＰａ以上であるものが好ましく、２００ＧＰａ未満では、多層プリント配線板としたときに十分な剛性が得られない。
【００１４】
ウィスカーの種類としては、例えば、硼酸アルミニウム、ウォラストナイト、チタン酸カリウム、塩基性硫酸マグネシウム、窒化けい素、α−アルミナの中から選ばれた１以上のものを用いることができる。その中でも、硼酸アルミニウムウィスカーは、弾性率が約４００ＧＰａとガラスよりも遥かに高く、熱膨張係数も小さく、しかも比較的安価である。この硼酸アルミニウムウィスカーを用いた本発明のプリプレグを使用して作製したプリント配線板は、従来のガラスクロスを用いたプリント配線板よりも、常温及び高温下における剛性が高く、ワイヤーボンディング性に優れ、電気信号の伝達特性に優れ、熱膨張係数が小さく、寸法安定性にすぐれる。したがって、本発明に用いるウィスカーの材質としては、硼酸アルミニウムが最適である。
【００１５】
ウィスカーの平均直径は、０．３μｍ未満であると樹脂ワニスへの混合が難しくなるとともに塗工作業性が低下し、３μｍを超えると表面の平坦性に悪影響がでるとともにウィスカーの微視的な均一分散性が損なわれる。したがって、ウィスカーの平均直径は０．３μｍ〜３μｍの範囲が好ましい。さらに同様の理由と塗工性が良い（平滑に塗りやすい）ことから平均直径は、０．５μｍ〜１μｍの範囲がより好ましい。このような直径のウィスカーを選択することにより、従来のガラスクロスを基材としたプリプレグを使用するよりも表面平坦性に優れたプリント配線板を得ることができる。
【００１６】
またウィスカーの平均長さは、平均直径の１０倍以上であることが好ましい。１０倍未満であると、繊維としての補強効果が僅かになると同時に、後述するウィスカーの樹脂層中での２次元配向が困難になるため、配線板にしたときに十分な剛性が得られない。しかしウィスカーが長すぎる場合は、ワニス中への均一分散が難しくなる、塗工性が低下する。
【００１７】
また、ある一つの導体回路間と接触したウィスカーが他の導体回路と接触する確率が高くなり、繊維に沿って移動する傾向にある銅イオンのマイグレーションによる回路間短絡事故を起こす可能性があるという問題がある。従ってウィスカーの平均長さは５０μm以下が好ましい。このような長さのウィスカーを使用した本発明の絶縁材料を用いて作製したプリント配線板は、従来のガラスクロスを基材にしたプリプレグを使用したプリント配線板よりも耐マイグレーション性に優れる。
【００１８】
またプリント配線板の剛性及び耐熱性をさらに高めるのに、シランカップリング剤で表面処理したウィスカーを使用することも有効である。カップリング剤で表面処理したウィスカーは、樹脂との濡れ性、結合性がすぐれ剛性及び耐熱性を向上させることができる。このとき使用するカップリング剤は、シリコン系、チタン系、アルミニウム系、ジルコニウム系、ジルコアルミニウム系、クロム系、ボロン系、リン系、アミノ酸系等の公知のものを使用できる。
【００１９】
（樹脂）
本発明で使用する樹脂は、従来のガラスクロスを基材としたプリプレグに使用されている樹脂及びガラスクロス基材を含まない接着フィルムあるいは銅箔付き接着フィルムに使用されている熱硬化性樹脂を使用することが出来る。ここでいう樹脂とは、樹脂、硬化剤、硬化促進剤、カップリング剤（必要に応じて）、希釈剤（必要に応じて）を含むものを意味する。
【００２０】
従来のガラスクロスを基材としたプリプレグに使用されている樹脂は、それ単独では、フィルム形成能がないため、銅箔の片面に塗工により接着剤層として形成し、加熱により溶剤除去し樹脂を半硬化した場合、搬送、切断及び積層等の工程中において、樹脂の割れや欠落等のトラブルを生じやすく、その後の熱圧成形時に層間絶縁層が内層回路存在部等で異常に薄くなり層間絶縁抵抗の低下やショートというトラブルを生じやすかったため、従来、銅箔付き接着フィルム用途に使用することが困難であった。
【００２１】
しかし、本発明では、樹脂中にはウィスカーが分散され、該樹脂はウィスカーにより補強されているため、本発明の樹脂とウィスカーからなるプリプレグ層にはフィルム形成能が発現し、搬送、切断及び積層等の工程中において、樹脂の割れや欠落等のトラブルを生じにくく、またウィスカーが存在するため熱圧成形時の層間絶縁層が異常に薄くなる現象も発生を防止できる。
【００２２】
また従来接着フィルムや銅箔付き接着フィルムに使用されている樹脂を用いることも効果的である。これらの樹脂は、高分子量成分等を含むことにより、樹脂単独でもフィルム形成能があるが、本発明によりウィスカーをその樹脂中に分散することにより、いっそうフィルム形成能が高められ取扱性が向上し、さらに絶縁信頼性もより高めることが可能となる。またウィスカーの分散によりフィルム形成能を高めた分だけ高分子量成分の添加量を減らすことも可能であり、それによって樹脂の耐熱性や接着性等を改善できる場合もある。
【００２３】
樹脂の種類としては、例えばエポキシ樹脂、ビスマレイミドトリアジン樹脂、ポリイミド樹脂、フェノール樹脂、メラミン樹脂、けい素樹脂、不飽和ポリエステル樹脂、シアン酸エステル樹脂、イソシアネート樹脂またはこれらの種々の変性樹脂類が好適である。この中で、プリント配線板特性上、特にビスマレイミドトリアジン樹脂、エポキシ樹脂が好適である。そのエポキシ樹脂としては、ビスフェノールＡ型エポキシ樹脂、ビスフェノールＦ型エポキシ樹脂、ビスフェノールＳ型エポキシ樹脂、フェノールノボラック型エポキシ樹脂、クレゾールノボラック型エポキシ樹脂、ビスフェノールＡノボラック型エポキシ樹脂、サリチルアルデヒドノボラック型エポキシ樹脂、ビスフェノールＦノボラック型エポキシ樹脂、脂環式エポキシ樹脂、グリシジルエステル型エポキシ樹脂、グリシジルアミン型エポキシ樹脂、ヒダントイン型エポキシ樹脂、イソシアヌレート型エポキシ樹脂、脂肪族環状エポキシ樹脂及びそれらのハロゲン化物、水素添加物、及び前記樹脂の混合物が好適である。なかでもビスフェノールＡノボラック型エポキシ樹脂またはサリチルアルデヒドノボラック型エポキシ樹脂は耐熱性に優れ好ましい。
【００２４】
（硬化剤）
このような樹脂の硬化剤としては、従来使用しているものが使用でき、樹脂がエポキシ樹脂の場合には、例えばジシアンジアミド、ビスフェノールＡ、ビスフェノールＦ、ポリビニルフェノール、フェノールノボラック樹脂、ビスフェノールＡノボラック樹脂及びこれらのフェノール樹脂のハロゲン化物、水素化物等を使用できる。なかでも、ビスフェノールＡノボラック樹脂は耐熱性に優れ好ましい。
この硬化剤の前記樹脂に対する割合は、従来使用している割合でよく、樹脂１００重量部に対して、２〜１００重量部の範囲が好ましく、さらには、ジシアンジアミドでは、２〜５重量部、それ以外の硬化剤では、３０〜８０重量部の範囲が好ましい。２重量部未満では、十分な硬化が得られず、１００重量部を超えると、余剰の硬化剤が残存し、硬化物の電気特性等を低下させるおそれがある。
【００２５】
（硬化促進剤）
硬化促進剤としては、樹脂がエポキシ樹脂の場合、イミダゾール化合物、有機リン化合物、第３級アミン、第４級アンモニウム塩などを使用する。
この硬化促進剤の前記樹脂に対する割合は、従来使用している割合でよく、樹脂１００重量部に対して、０．０１〜２０重量部の範囲が好ましく、０．１〜１０重量部の範囲がより好ましい。０．０１重量部未満であると、硬化が著しく遅くなり、２０重量部を超えると、硬化反応の制御ができないほど硬化速度が大きくなる。
【００２６】
（希釈剤）
本発明の熱硬化性樹脂は、溶剤で希釈して樹脂ワニスとして使用することもできる。このような溶剤には、アセトン、メチルエチルケトン、トルエン、キシレン、メチルイソブチルケトン、酢酸エチル、エチレングリコールモノメチルエーテル、メタノール、エタノール、Ｎ,Ｎ−ジメチルホルムアミド、Ｎ,Ｎ−ジメチルアセトアミド等を使用できる。
この希釈剤の前記樹脂に対する割合は、従来使用している割合でよく、樹脂１００重量部に対して１〜２００重量部の範囲が好ましく、３０〜１００重量部の範囲がさらに好ましい。１重量部未満であると、希釈剤としての効果がなく、２００重量部を超えると、樹脂組成物の粘度が低すぎて、銅箔やキャリアフィルムに塗布するのが困難となる。
【００２７】
（その他の配合剤）
さらに本発明においては、樹脂中に上記した各成分の他に、必要に応じて従来より公知のカップリング剤、充填材、難燃剤等を適宜配合してもよい。
【００２８】
（樹脂とウィスカーの割合）
樹脂への電気絶縁性ウィスカーの配合量は、樹脂固形分１００重量部に対し５重量部未満であるとこのプリプレグは切断時に樹脂が細かく砕けて飛散しやすくなる等の取り扱い性が悪くなるとともに配線板にしたときに十分な剛性が得られない。一方ウィスカーの配合量が３５０重量部以上であると、熱圧成形時の内層回路の穴埋め性や回路間への樹脂充填性が損なわれ、熱圧成形後のウィスカー複合樹脂層中にボイドやかすれが発生しやすくなり、配線板特性を損なう恐れがある。したがって、ウィスカーの配合量は、樹脂固形分１００重量部に対し５〜３５０重量部が好ましい。さらに、内層回路の穴埋め性や回路間への樹脂充填性に優れ、なおかつ、製造した配線板が従来のガラスクロス使用のプリプレグを用いて製造した配線板と比較し、同等または同等以上の剛性と寸法安定性とワイヤボンディング性を持つことが出来る理由から、ウィスカーの配合量は、樹脂固形分１００重量部に対し３０〜２３０重量部であることがより好ましい。
【００２９】
（キャリアフィルム）
本発明において絶縁層であるウィスカー複合樹脂層（Ｂステージ状態）をその片面に形成する対象であるキャリアフィルムとしては、銅箔、アルミ箔等の金属箔、ポリエステルフィルム、ポリイミドフィルム、あるいは前記金属箔及びフィルムの表面を離型剤により処理したものを使用する。
【００３０】
（ウィスカーの配向）
本発明の電気絶縁性ウィスカーとＢステージ状態の樹脂とから構成される絶縁材料の中のウィスカーは、２次元配向に近い状態（ウィスカーの軸方向が絶縁材料層の形成する面と平行に近い状態）にさせることが好ましい。具体的には、半硬化状態の樹脂中にある全ウィスカーの７０％以上のウィスカーの繊維軸を、絶縁材料の面方向に対して±３０度以内の方向に配向させることが好ましい。このようにウィスカーを配向させることにより、本発明の絶縁材料は良好な取り扱い性が得られると同時に配線板にしたときに高い剛性と良好な寸法安定性及び表面平坦性が得られる。
【００３１】
（塗工方式）
上記のようにウィスカーを配向させるには、前述した好ましい範囲の繊維長のウィスカーを使用すると同時に、銅箔にウィスカーを配合した樹脂ワニスを塗工する際に、ブレードコータ、ロッドコータ、ナイフコータ、スクイズコータ、リバースロールコータ、トランスファロールコータ等の銅箔と平行な面方向にせん断力を負荷できるかあるいは、銅箔の面に垂直な方向に圧縮力を負荷できる塗工方式を採用すればよい。
【００３２】
（作用）
本発明の絶縁ワニスの製造方法は、フィルタのメッシュサイズの適正化により、規定サイズ以上の電気絶縁性ウイスカー凝集体を分別するもので、電気絶縁性ウイスカーを複合化させた絶縁材料に電気絶縁性ウイスカーの凝集体が混入することを絶縁ワニスの段階で抑制し、絶縁材料の絶縁信頼性を高めることができる。
【００３３】
また、本発明の絶縁材料を使用して作製した絶縁層は、基材がガラスよりレーザに対し被加工性が良好でしかも微細なウィスカーであるため、従来のガラスクロスプリプレグを使用した絶縁層では困難であったレーザ穴あけが容易にできる。そのため、直径１００μm以下の小径のインターステーシャルバイアホール（ＩＶＨ）が容易に作製可能となり、プリント配線板の回路を微細化でき、電子機器の高密度化、高性能化に大きく貢献できる。
【００３４】
【実施例】
実施例１
（絶縁ワニス）
ビスフェノールＡノボラック型エポキシ樹脂（分子量：１２００、エポキシ当量；２０６）を７０重量部と、ビスフェノールＡノボラック樹脂（分子量：６００、水酸基当量；１１８）を３０重量部と、２−エチル−４−メチルイミダゾールを０．５重量部と、メチルエチルケトンを７０部からなる樹脂ワニスに、平均直径０．８μｍ、平均繊維長２０μｍの硼酸アルミニウムウィスカーを、樹脂固形分１００重量部に対し９０重量部になるように配合し、硼酸アルミニウムウィスカーがワニス中に均一に分散するまで撹拌した。これを、２００メッシュのナイロンフィルタに通過させて５０μｍ以上のサイズのウイスカーの凝集体を分別除去した。
【００３５】
（接着フィルム）
５０μｍ以上のウイスカー凝集体を分別除去した絶縁ワニスを、厚さ１８μｍの銅箔と厚さ５０μｍのポリエチレンテレフタレート（以下、ＰＥＴという。）フィルムにナイフコータにて塗工し、温度１５０℃で１０分間加熱乾燥して、溶剤を除去するとともに、樹脂を半硬化して、接着層の厚さが５０μｍと１００μｍの２種類の銅箔付き接着フィルムと、接着層の厚さが５０μｍと１００μｍの２種類のＰＥＴフィルム付き接着フィルムを作製し、ＰＥＴフィルム付き接着フィルムからＰＥＴフィルムを剥離して、ウィスカー体積分率が３０％でウィスカーと半硬化状態にあるエポキシ樹脂からなる、厚さが５０μｍの接着フィルムと１００μｍの接着フィルムを作製した。
作製した銅箔付き接着フィルムは、カッターナイフ及びシャーにより、樹脂の飛散等なくきれいに切断でき、接着フィルム同士のブロッキングも発生せず、良好な取扱性であった。また、 ＰＥＴフィルムに塗工して作製した接着フィルムは、ＰＥＴフィルムの剥離時や通常の取り扱い時に割れる等のトラブルはなく、またカッターナイフ及びシャーにより、樹脂の飛散等なくきれいに切断でき、接着フィルム同士のブロッキングも発生せず、良好な取扱性であった。
【００３６】
（電食試験）
つぎに、厚さ０．８ｍｍのガラスエポキシ両面銅張積層板の銅箔の不要な箇所をエッチング除去し、電食試験の内層面の電極となるパターンを形成し、この上下に上記で作製した接着層の厚さが５０μｍの銅箔付き接着フィルムを、接着フィルムが電食試験の内層面の電極となるパターンと接するように重ね合せて積層し、１７０℃、２．５ＭＰａ，６０分の条件で熱圧成形した。得られた積層板の銅箔の不要な箇所をエッチング除去して、内層の電極となる電食試験パターンの位置に相当する部分に、外層の電極となるパターンを形成し、電食試験片を得た。この内層と外層の電極間に５０Ｖの電圧を印加し、８５℃、８５％ＲＨの雰囲気下で１０００時間経過後の絶縁抵抗値を測定した結果、１０9Ω以上の良好な値を示し、接着フィルムが耐電食性に優れていることを確認した。
（曲げ弾性率）
また、作製した厚さ１００μｍの接着フィルムの上下に、厚さ１８μｍの片面粗化銅箔を、該粗化面が接着フィルムに向き合うように積層し、１７０℃、２．５ＭＰａ、６０分の条件で熱圧成形した。得られた銅張積層板の銅箔をエッチング除去し、曲げ弾性率を三点曲げで測定したところ２０ＧＰａ（銅箔なし、たてよこ平均）であった。
（穴あけ精度）
また、ドリルのすべり量を、直径０．３ｍｍのドリルを用いて、この銅張積層板を１０枚重ねて穴あけしたときの最上板と最下板の穴位置のずれ量として測定したところ、２０μｍ以下であった。
【００３７】
（多層プリント配線板）
この銅張積層板の銅箔の不要な箇所をエッチング除去して回路を形成し、その両面に先に作製した厚さ５０μｍの本発明の接着フィルムを重ね、そのさらに外側に厚さ１８μｍの片面粗化銅箔を粗化面が接着フィルムに向き合うように積層し、１７０℃、２．５ＭＰａ、６０分の条件で熱圧成形し、内層回路入り多層銅張積層板を作製した。
この内層回路入り多層銅張積層板の表面粗さを、触針式表面粗さ計にて測定したところ、測定箇所がその直下に内層回路のある部分とない部分とを含む長さ２５ｍｍの一直線上の外層表面で、内層回路のある部分とない部分の段差の１０点平均は、３μｍ以下であり、回路加工に支障のない良好な表面平坦性を有していた。
さらにこの内層回路入り多層銅張積層板の表面銅箔の所定位置に、エッチングにより直径７５μｍの穴をあけ、その穴に住友重機械工業(株)製インパクトレーザを用いて穴あけを行い、過マンガン酸によるデスミア処理を行い、無電解めっきを行った後、エッチングレジストパターンを形成し、不要な銅をエッチング除去して回路を形成した。
この多層プリント配線板の両面に、再び厚さ５０μｍの接着フィルムを、そのさらに外側に厚さ１８μｍの片面粗化銅箔を粗化面が接着フィルムに向き合うように積層し、１７０℃、２．５MPa、６０分の条件で熱圧成形し、内層回路入り多層銅張積層板を作製し、所定位置にエッチングにより直径７５μｍの穴をあけ、その穴に住友重機械工業(株)製インパクトレーザを用いて穴あけを行い、過マンガン酸によるデスミア処理を行い、無電解めっきを行った後、エッチングレジストパターンを形成し、不要な銅をエッチング除去することにより回路を形成した。以上の工程をくり返して、１０層プリント配線板を作製した。
【００３８】
（多層プリント配線板の試験）
この多層プリント配線板の一部を切り取り、その熱膨張率と曲げ弾性率を測定した。熱膨張率はＴＭＡにて、曲げ弾性率は、ＤＭＡの曲げモードにて測定した。たてよこ方向の平均の熱膨張係数は、１０ｐｐｍ／℃（常温下）であり、たてよこ方向の平均の曲げ弾性率は常温下で６０ＧＰａ、高温下（２００℃）で４０ＧＰａであった。また、バーコル硬度計による表面硬度は、常温下で６５、高温下（２００℃）で５０であった。
（ワイヤボンディング性）
さらに、この１０層プリント配線板の一部にベアチップを実装し、ワイヤボンディングで表面回路と接続した。ワイヤボンディング条件は、超音波出力を１Ｗ、超音波出力時間を５０μｓ、ボンド荷重を１００ｇ、ワイヤボンディング温度を１８０℃としたところ、良好にワイヤボンディングできた。
（熱衝撃試験）
また、この１０層プリント配線板に寸法８×２０ｍｍのＩＣチップ（ＴＳＯＰ）をはんだを介して表面回路と接続し、このＩＣチップ（ＴＳＯＰ）を実装した基板を、−６５℃で３０分と１５０℃で３０分の環境に晒すことを１サイクルとする熱衝撃試験で評価したところ、２,０００サイクル後もはんだ接続部に断線等の不良は発生していなかった。またこの基板の内部のインターステーシャルバイアホールを含む回路の導通試験を行ったが断線等のトラブルの発生はなかった。
【００３９】
実施例２
（ワニス）
サリチルアルデヒドノボラック型エポキシ樹脂（分子量：１０００、エポキシ当量；１８０）を７０重量部と、ビスフェノールＡノボラック樹脂（分子量：７００、水酸基当量；１１８）を３０重量部と、硬化促進剤としてＮ−メチルイミダゾールを０．５重量部と、メチルエチルケトンを７０重量部からなる樹脂ワニスに、平均直径０．８μｍ、平均繊維長２０μｍの硼酸アルミニウムウィスカーを、樹脂固形分１００重量部に対し、９０重量部配合し、硼酸アルミニウムウィスカーがワニス中に均一に分散するまで撹拌した。
これを、２００メッシュのナイロンフィルタを通過させて５０μｍ以上のサイズのウイスカーの凝集体を分別除去した。
【００４０】
（接着フィルム）
上記５０μｍ以上のウイスカー凝集体を分別除去した絶縁ワニスを、厚さ１８μｍの銅箔と厚さ５０μｍのＰＥＴフィルムにナイフコータにて塗工し、温度１５０℃で１０分間加熱乾燥して、溶剤を除去するとともに、樹脂を半硬化して、接着層の厚さが５０μｍと１００μｍの２種類の銅箔付き接着フィルムと、接着層の厚さが５０μｍと１００μｍの２種類のＰＥＴフィルム付き接着フィルムを作製し、ＰＥＴフィルム付き接着フィルムからＰＥＴフィルムを剥離除去して、ウィスカー体積分率が３０％でウィスカーと半硬化状態にあるエポキシ樹脂からなる、厚さが５０μｍと１００μｍの２種類の接着フィルムを作製した。
作製した銅箔付き接着フィルムは、カッターナイフ及びシャーにより、樹脂の飛散等なくきれいに切断でき、接着フィルム同士のブロッキングも発生せず、良好な取扱性であった。また、ＰＥＴフィルムに塗工して作製した接着フィルムは、ＰＥＴフィルムの剥離時や通常の取り扱い時に割れる等のトラブルはなく、またカッターナイフ及びシャーにより、樹脂の飛散等なくきれいに切断でき、接着フィルム同士のブロッキングも発生せず、良好な取扱性であった。
【００４１】
（電食試験）
つぎに、厚さ０．８ｍｍのガラスエポキシ両面銅張積層板の銅箔の不要な箇所をエッチング除去し、電食試験の内層面の電極となるパターンをエッチングにより作製し、この上下に、上記で作製した接着層の厚さ５０μｍの銅箔付き接着フィルムを接着フィルムが電食試験の内層面の電極となるパターンと接するように重ね合せて積層し、１７０℃、２．５ＭＰａ、６０分の条件で熱圧成形した。得られた積層板の、内層の電極となる電食試験パターンの位置に合わせた部分に外層の電極となるパターンをエッチングで作製し、電食試験片を得た。この内層と外層の電極間に５０Ｖの電圧を印加し、８５℃、８５％ＲＨの雰囲気下で１０００時間経過後の絶縁抵抗値を測定した結果、１０9Ω以上の良好な値を示し、接着フィルムが耐電食性に優れていることを確認した。
（曲げ弾性率）
また、 作製した厚さ１００μｍの接着フィルムの上下に厚さ１８μｍの片面粗化銅箔を、該粗化面が接着フィルムに向き合うように積層し、１７０℃、２．５MPa、６０分の条件で熱圧成形した。得られた銅張積層板の銅箔をエッチング除去し、曲げ弾性率を三点曲げで測定したところ２０ＧＰａ（銅箔なし、たてよこ平均）であった。
（穴あけ精度）
また、ドリルのすべり量を、直径０．３ｍｍのドリル用いて、この銅張積層板を１０枚重ねて穴明けしたときの最上板と最下板の穴位置のずれ量として測定したところ、２０μm以下であった。
【００４２】
（多層プリント配線板）
この銅張積層板の銅箔の不要な箇所をエッチング除去して回路を形成し、その両面に、先に作製した厚さ５０μｍの接着フィルムを重ね、そのさらに外側に厚さ１８μｍの片面粗化銅箔を粗化面が接着フィルムに向き合うように積層し、１７０℃、２．５ＭＰａ、６０分の条件で熱圧成形し、内層回路入り多層銅張積層板を作製した。
この内層回路入り多層銅張積層板の表面粗さを触針式表面粗さ計にて測定したところ、測定箇所がその直下に内層回路のある部分とない部分とを含む長さ２５mmの一直線上の外層表面で、内層回路のある部分とない部分の段差の１０点平均は、３μm以下であり、回路加工に支障のない良好な表面平坦性を有していた。
さらにこの内層回路入り多層銅張積層板の表面銅箔の所定位置にエッチングにより直径７５μｍの穴をあけ、その穴に住友重機械工業(株)製インパクトレーザを照射して穴あけを行い、過マンガン酸によるデスミア処理を行い、無電解めっきを行った後、エッチングレジストパターンを形成して不要な銅をエッチング除去して回路を形成した。
この多層プリント配線板の両面に、再び上記の厚さ５０μｍの接着フィルムを重ね、そのさらに外側に厚さ１８μｍの片面粗化銅箔を粗化面が接着フィルムに向き合うように積層し、１７０℃、２．５ＭＰａ、６０分の条件で熱圧成形し、内層回路入り多層銅張積層板を作製し、所定位置にエッチングにより直径７５μｍの穴をあけ、その穴に住友重機械工業(株)製インパクトレーザを用いて穴あけを行い、過マンガン酸によるデスミア処理を行い、無電解めっきを行った後、エッチングレジストパターンを形成し、不要な銅をエッチング除去して、回路を形成した。前記工程をくり返して、１０層プリント配線板を作製した。
【００４３】
（多層プリント配線板の試験）
この多層プリント配線板の一部を切り取り、その熱膨張率と曲げ弾性率を測定した。熱膨張率はＴＭＡにて、曲げ弾性率は、ＤＭＡの曲げモードにて測定した。たてよこ方向の平均の熱膨張係数は、１０ｐｐｍ／℃（常温下）であり、たてよこ方向の平均の曲げ弾性率は常温下で６０ＧＰａ、高温下（２００℃）で５０ＧＰａであった。また、バーコル硬度計による表面硬度は、常温下で６５、高温下（２００℃）で５５であった。
（ワイヤボンディング性）
さらに、この１０層プリント配線板の一部にベアチップを実装し、ワイヤボンディングで表面回路と接続した。ワイヤボンディング条件は、超音波出力を１Ｗ、超音波出力時間を５０μｓ、ボンド荷重を１００ｇ、ワイヤボンディング温度を１８０℃としたところ、良好にワイヤボンディングできた。
（熱衝撃試験）
また、この１０層プリント配線板に寸法８×２０ｍｍのＩＣチップ（ＴＳＯＰ）をはんだを介して表面回路と接続し、このＩＣチップ（ＴＳＯＰ）を実装した基板を−６５℃で３０分と１５０℃で３０分の環境に晒すことを１サイクルとする熱衝撃試験で評価したところ、２０００サイクル後もはんだ接続部に断線等の不良は発生していなかった。またこの基板の内部のインターステーシャルバイアホールを含む回路の導通試験を行ったが断線等のトラブルの発生はなかった。
【００４４】
比較例１
（ワニス）
ビスフェノールＡノボラック型エポキシ樹脂（分子量：１２００、エポキシ当量：２０６）を７０重量部と、ビスフェノールＡノボラック樹脂（分子量：７００、水酸基当量：１１８）を３０重量部と、２−エチル−４メチルイミダゾールを０．５重量部と、メチルエチルケトンを７０重量部からなる樹脂ワニスに、平均直径が０．８μｍ、平均繊維長が２０μｍの硼酸アルミニウムウィスカーを、樹脂固形分１００重量部に対し９０重量部になるように配合し、硼酸アルミニウムウィスカーがワニス中に均一に分散するまで撹拌した。
（接着フィルム）
この絶縁ワニスを、２００メッシュのナイロンフィルタを通過させずに、厚さ１８μｍの銅箔と厚さ５０μｍのＰＥＴフィルムにナイフコータにて塗工し、温度１５０℃で１０分間加熱乾燥して、溶剤を除去するとともに、樹脂を半硬化して、接着層の厚さが５０μｍと１００μｍの２種類の銅箔付き接着フィルムと、接着層の厚さが５０μｍと１００μｍの２種類のＰＥＴフィルム付き接着フィルムを作製し、ＰＥＴフィルム付き接着フィルムからＰＥＴフィルムを剥離により除去して、ウィスカー体積分率が３０％でウィスカーと半硬化状態にあるエポキシ樹脂からなる、厚さが５０μｍと１００μｍの接着フィルムを作製した。
作製した銅箔付き接着フィルムは、カッターナイフ及びシャーにより、樹脂の飛散等なくきれいに切断でき、接着フィルム同士のブロッキングも発生せず、良好な取扱性であった。また、ＰＥＴフィルムに塗工して作製した接着フィルムは、ＰＥＴフィルムの剥離時や通常の取り扱い時に割れる等のトラブルはなく、またカッターナイフ及びシャーにより、樹脂の飛散等なくきれいに切断でき、接着フィルム同士のブロッキングも発生せず、良好な取扱性であった。
【００４５】
（電食試験）
つぎに、厚さ０．８ｍｍのガラスエポキシ両面銅張積層板の銅箔の不要な箇所をエッチング除去して、電食試験の内層面の電極となるパターンを形成し、この上下に上記で作製した絶縁層の厚さ５０μｍの接着フィルムを、接着フィルムが電食試験の内層面の電極となるパターンと接するように重ね合せ、さらに厚さ１８μｍの片面粗化銅箔を該粗化が接着フィルムに向き合うように積層し、１７０℃、２．５ＭＰａ、６０分の条件で熱圧成形した。得られた積層板の、内層の電極となる電食試験パターンの位置に相当する部分に、不要な銅箔をエッチング除去して外層の電極となるパターンを形成し、電食試験片を得た。この内層と外層の電極間に５０Ｖの電圧を印加し、８５℃、８５％ＲＨの雰囲気下で経時変化を追跡した結果、２５０時間後の絶縁抵抗値が１０9Ω未満となり、接着フィルムが耐電食性に劣っていることがわかった。
（曲げ弾性率）
作製した厚さ１００μｍの接着フィルムの上下に厚さ１８μｍの片面粗化銅箔を該粗化が接着フィルムに向き合うように積層し、１７０℃、２．５ＭＰａ、６０分の条件で熱圧成形した。得られた銅張積層板の銅箔をエッチング除去し、曲げ弾性率を三点曲げで測定したところ２０ＧＰａ（銅箔なし、たてよこ平均）であった。
（穴あけ精度）
また、ドリルのすべり量を、直径０．３ｍｍのドリルを用いてこの銅張積層板を１０枚重ねて穴あけしたときの最上板と最下板の穴位置のずれ量として測定したところ、２０μｍ以下であった。
【００４６】
（多層プリント配線板）
この銅張積層板の銅箔の不要な箇所をエッチング除去し、回路を形成し、その両面に、先に作製した厚さ５０μｍの接着フィルムを重ね、そのさらに外側に厚さ１８μｍの片面粗化銅箔を粗化面が接着フィルムに向き合うように積層し、１７０℃、２．５ＭＰａ、６０分の条件で熱圧成形し、内層回路入り多層銅張積層板を作製した。
この内層回路入り多層銅張積層板の表面粗さを触針式表面粗さ計にて測定したところ、測定箇所がその直下に内層回路のある部分とない部分とを含む長さ２５mmの一直線上の外層表面で、内層回路のある部分とない部分の段差の１０点平均は、３μｍ以下であり、回路加工に支障のない良好な表面平坦性を有していた。さらにこの内層回路入り多層銅張積層板の表面銅箔の所定位置にエッチングにより直径７５μｍの穴をあけ、その穴に住友重機械工業(株)製インパクトレーザを用いて穴あけを行い、過マンガン酸によるデスミア処理を行い、無電解めっきを行った後、エッチングレジストパターンを形成し、不要な銅をエッチング除去して回路を形成した。
この多層プリント配線板の両面に、再び上記の厚さ５０μｍの接着フィルムを重ね、そのさらに外側に厚さ１８μｍの片面粗化銅箔を粗化面が接着フィルムに向き合うように積層し、１７０℃、２．５ＭＰａ、６０分の条件で熱圧成形し、内層回路入り多層銅張積層板を作製し、その銅箔の所定位置にエッチングにより直径７５μｍの穴をあけ、その穴に住友重機械工業(株)製インパクトレーザを用いて穴あけを行い、過マンガン酸によるデスミア処理を行い、無電解めっきを行った後、エッチングレジストパターンを形成して不要な銅をエッチング除去して回路を形成した。以上の工程をくり返して、１０層プリント配線板を作製した。
（多層プリント配線板の試験）
この多層プリント配線板の一部を切り取り、その熱膨張率と曲げ弾性率を測定した。熱膨張率はＴＭＡにて、曲げ弾性率は、ＤＭＡの曲げモードにて測定した。たてよこ方向の平均の熱膨張係数は、１０ｐｐｍ／℃（常温下）であり、たてよこ方向の平均の曲げ弾性率は常温下で６０ＧＰａ、高温下（２００℃）で４０ＧＰａであった。また、バーコル硬度計による表面硬度は、常温下で６５、高温下（２００℃）で５０であった。
（ワイヤボンディング性）
さらに、この１０層プリント配線板の一部にベアチップを実装し、ワイヤボンディングで表面回路と接続した。ワイヤボンディング条件は、超音波出力を１Ｗ、超音波出力時間を５０μｓ、ボンド荷重を１００ｇ、ワイヤボンディング温度を１８０℃としたところ、良好にワイヤボンディングできた。
（熱衝撃試験）
また、この１０層プリント配線板に寸法８×２０ｍｍのＩＣチップ（ＴＳＯＰ）を、はんだを介して表面回路と接続し、このＩＣチップ（ＴＳＯＰ）を実装した基板を、−６５℃で３０分と１５０℃で３０分の環境に晒すことを１サイクルとする熱衝撃試験で評価したところ、２０００サイクル後もはんだ接続部に断線等の不良は発生していなかった。
またこの基板の内部のインターステーシャルバイアホールを含む回路の導通試験を行ったが断線等のトラブルの発生はなかった。
【００４７】
比較例２
（プリプレグ）
ビスフェノールＡノボラック型エポキシ樹脂（分子量：１２００、エポキシ当量：２０６）を７０重量部と、ビスフェノールＡノボラック樹脂（分子量：７００、水酸基当量：１１８）を３０重量部と、２−エチル−４−メチルイミダゾールを０．５重量部と、メチルエチルケトンを７０重量部からなる樹脂ワニスを、厚さ５０μｍと１００μｍのガラスクロスに含浸塗工し、温度１５０℃で１０分間加熱乾燥して、溶剤を除去するとともに、樹脂を半硬化し、ガラスクロスと半硬化状態にあるエポキシ樹脂からなる、厚さが７０μｍと１２０μｍのガラスエポキシプリプレグを作製した。
作製したプリプレグは、カッターナイフ及びシャーによる切断時に樹脂が飛散した。
【００４８】
（電食試験）
つぎに、厚さ０．８ｍｍのガラスエポキシ両面銅張積層板の銅箔の不要な箇所をエッチング除去して、電食試験の内層面の電極となるパターンを形成し、この上下に、上記絶縁層の厚さ５０μｍのエポキシプリプレグと厚さ１８μｍの片面粗化銅箔をエポキシプリプレグが電食試験の内層面の電極となるパターンと接するように重ね合せて積層し、１７０℃、２．５ＭＰａ、６０分の条件で熱圧成形した。得られた積層板の、内層の電極となる電食試験パターンの位置に合わせた部分に外層の電極となるパターンをエッチングで作製し、電食試験片を得た。この内層と外層の電極間に５０Ｖの電圧を印加し、８５℃、８５％ＲＨの雰囲気下で１０００時間経過後の絶縁抵抗値を測定した結果、１０9Ω以上の良好な値を示し、エポキシプリプレグの降下物が耐電食性に優れていることを確認した。
（曲げ弾性率）
作製した厚さ１２０μｍのガラスエポキシプリプレグの上下に、厚さ１８μｍの片面粗化銅箔を該粗化面がプリプレグに向き合うように積層し、熱圧成形した。得られた銅張積層板の銅箔をエッチング除去し、曲げ弾性率を三点曲げで測定したところ８ＧＰａ（銅箔なし、たてよこ平均）であった。
（穴あけ精度）
また、直径０．３ｍｍのドリルにてこの銅張積層板を１０枚重ねて穴あけしたときの最上板と最下板の穴位置のずれ量を測定したところ５０μm以上あった。
【００４９】
（多層プリント配線板）
この銅張積層板に回路加工を施して内層回路板を作製し、その両面に先に作製した厚さ５０μmのガラスエポキシプリプレグを、そのさらに外側に厚さ１８μmの片面粗化銅箔を粗化面がプリプレグに向き合うように積層し、１７０℃、２．５ＭＰａ、６０分の条件で熱圧成形し、内層回路入り多層銅張積層板を作製した。
この内層回路入り多層銅張積層板の表面粗さを触針式表面粗さ計にて測定したところ、測定箇所がその直下に内層回路のある部分とない部分とを含む長さ２５mmの一直線上の外層表面で、内層回路のある部分とない部分の段差の１０点平均は、８μｍ以上あった。
さらにこの内層回路入り多層銅張積層板の表面銅箔の所定位置にエッチングにより直径７５μｍの穴をあけ、その穴へ住友重機械工業(株)製インパクトレーザを用いて穴あけを試みたが、ガラス部分が除去できなかった。
【００５０】
比較例３
（接着フィルム）
重量平均分子量が５０，０００の高分子量エポキシ重合体を５０重量部と、ビスフェノールＡ型エポキシ樹脂（分子量：１２００、エポキシ当量：２０６）をを５０重量部と、高分子量エポキシ重合体の架橋剤としてフェノール樹脂マスク化ジイソシアネートを０．２当量と、硬化剤として、２−エチル−４−メチルイミダゾールを０．５重量部からなる熱硬化性樹脂を、厚さ１８μｍの銅箔と厚さ５０μｍのＰＥＴフィルムにナイフコータにて塗工し、温度１５０℃で１０分間加熱乾燥して溶剤を除去するとともに、樹脂を半硬化して、接着層の厚さが５０μｍの銅箔付き接着フィルムと、接着層の厚さが５０μｍのＰＥＴフィルム付き接着フィルムを作製し、ＰＥＴフィルム付き接着フィルムからＰＥＴフィルムを剥離除去して、半硬化状態にあるエポキシ樹脂からなる、厚さが５０μｍの接着フィルムを作製した。
作製した接着フィルムは、ＰＥＴフィルムの剥離時や通常の取り扱い時に割れる等のトラブルはなく、またカッターナイフ及びシャーにより、樹脂の飛散等なくきれいに切断できたが、プリプレグ同士のブロッキングが発生し、取扱性が悪かった。
【００５１】
（電食試験）
つぎに、厚さ０．８ｍｍのガラスエポキシ両面銅張積層板の銅箔の不要な箇所をエッチング除去して、電食試験の内層面の電極となるパターンを形成し、この上下に上記で作製した絶縁層の厚さ５０μｍの銅箔付き接着フィルムを接着フィルムが電食試験の内層面の電極となるパターンと接するように重ね合せて積層し、１７０℃、２．５ＭＰa、６０分間の条件で熱圧成形した。得られた積層板の銅箔の不要な箇所をエッチング除去して、内層の電極となる電食試験パターンの位置に合わせた部分に外層の電極となるパターンを作製し、電食試験片を得た。この内層と外層の電極間に５０Ｖの電圧を印加し、８５℃、８５％ＲＨの雰囲気下で１０００時間経過後の絶縁抵抗値を測定した結果、１０9Ω以上の良好な値を示し、接着フィルムが耐電食性に優れていることを確認した。
【００５２】
（多層プリント配線板）
比較例１で作製した内層回路板の両面に前記の厚さ５０μｍの接着フィルムを、そのさらに外側に厚さ１８μｍの片面粗化銅箔を粗化面が接着フィルムに向き合うように積層し、熱圧成形し内層回路入り多層銅張積層板を作製した。
この内層回路入り多層銅張積層板の表面粗さを触針式表面粗さ計にて測定した。測定箇所はその直下に内層回路のある部分とない部分とを含む長さ２５mmの一直線上の外層表面とした。内層回路のある部分とない部分の段差の１０点平均は、３μm以下であり、回路加工に支障のない良好な表面平坦性であった。
【００５３】
さらにこの内層回路入り多層銅張積層板の表面銅箔の所定位置をエッチング除去することにより直径７５μmの穴をあけ、その穴に住友重機械工業(株)製インパクトレーザを用いて穴あけを行い、過マンガン酸によるデスミア処理を行い、無電解メッキを行った後、エッチングレジストパターンを焼き付け現像して作成し、不要な銅をエッチング除去して外層回路を形成した。
この多層プリント配線板の両面に、前記の厚さ５０μｍの接着フィルムを、そのさらに外側に厚さ１８μｍの片面粗化銅箔を粗化面が接着フィルムに向き合うように積層し、１７０℃、２．５MPa、６０分間の条件で熱圧成形し、内層回路入り多層銅張積層板を作製し、その外層銅箔の所定位置をエッチング除去することにより直径７５μｍの穴をあけ、その穴に住友重機械工業(株)製インパクトレーザを用いて穴あけを行い、過マンガン酸によるデスミア処理を行い、無電解メッキを行った後、エッチングレジストパターンを焼き付け現像して形成し、不要な銅をエッチング除去することにより外層回路を形成した。前記工程をくり返して１０層プリント配線板を作製した。
【００５４】
（多層プリント配線板の試験）
この多層プリント配線板の一部を切り取り、その熱膨張率と曲げ弾性率を測定した。熱膨張率はＴＭＡにて、曲げ弾性率は、ＤＭＡの曲げモードにて測定した。たてよこ方向の平均の熱膨張係数は、３０ｐｐｍ／℃（常温下）であり、たてよこ方向の平均の曲げ弾性率は常温下で２０ＧＰａ、高温下（２００℃）で１０ＧＰａであった。また、バーコル硬度計による表面硬度は、常温下で３０、高温下（２００℃）下で１０であった。
（ワイヤボンディング性）
さらに、この１０層プリント配線板の一部にベアチップを実装し、ワイヤボンディングで表面回路と接続した。ワイヤボンディング条件は、超音波出力を１Ｗ、超音波出力時間を５０μｓ、ボンド荷重を１００ｇとした。ワイヤボンディング温度を１００℃に下げてもワイヤのはがれが発生した。
（熱衝撃試験）
また、この１０層プリント配線板に寸法８mm×２０ｍｍのＴＳＯＰ半導体チップを、はんだを介して表面回路と接続し、このＴＳＯＰ実装基板を−６５℃で３０分と１５０℃で３０分の環境に晒すことを１サイクルとする熱衝撃試験で評価したところ、１００サイクル前後ではんだ接続部に断線不良を発生した。また、この基板の内部のインターステーシャルバイアホールを含む回路の導通試験を行ったところ断線箇所があった。
【００５５】
【発明の効果】
本発明の絶縁ワニスの製造方法により、電気絶縁性ウイスカーを複合化させた接着フィルムに電気絶縁性ウイスカーの凝集体が混入することを絶縁ワニスの段階で抑制することが可能となり、接着フィルムの絶縁信頼性を高めることができる。本発明にしたがって製造した絶縁ワニスを用いて得られた接着フィルムは、電気絶縁性ウイスカーの添加によりエポキシ樹脂をシート状に形成することができたもので、これを使用したプリント配線板は、表面が平坦で回路加工性が良く、剛性が高いため実装信頼性が高く、表面硬度が高いためワイヤボンド性が良く、熱膨張係数が小さいため寸法安定性が良くなる。したがって、多層プリント配線板の高密度化、薄型化、高信頼性化、低コスト化に多大の貢献をする。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an insulating varnish.
[0002]
[Prior art]
The printed wiring board is usually obtained by processing a circuit on a copper-clad laminate obtained by laminating a copper foil and a prepreg and hot pressing.
In addition, the multilayer printed wiring board is formed by hot pressing these printed wiring boards through a prepreg, or by hot press forming these printed wiring boards and a copper foil through a prepreg. It is obtained by forming a circuit on the surface of a multilayer copper-clad laminate containing an inner layer circuit obtained by converting the circuit.
[0003]
Conventionally, a glass cloth prepreg obtained by impregnating and drying a glass cloth with a resin and making the resin semi-cured is used for the prepreg for the printed wiring board. In addition to the glass cloth prepreg, the multilayer printed wiring board includes: As described in JP-A-6-200216 and JP-A-6-242465, an adhesive film in which a resin having film forming ability which is a prepreg not using a glass cloth is made into a semi-cured state, An adhesive film with a copper foil in which an adhesive film is formed on one side of a copper foil as described in JP-A-196862 is used.
In addition, the film forming ability here is less likely to cause trouble such as cracking or missing of the resin during the process of transporting, cutting, and laminating the prepreg, and the interlayer insulating layer is the inner layer circuit existing portion at the subsequent hot press molding. It means the performance that is less likely to cause trouble such as abnormal thinning, interlayer insulation resistance drop and short circuit.
[0004]
[Problems to be solved by the invention]
In recent years, electronic devices have been reduced in size, weight, performance, and cost, and printed wiring boards are required to have higher density, thinner thickness, higher reliability, and lower cost.
In order to increase the density, fine wiring is necessary. For this purpose, the surface must have good flatness and good dimensional stability. Furthermore, a fine through hole and an interstitial via hole (IVH) are required, and drilling workability and laser hole workability are required to be good. In order to improve the flatness of the surface, it is necessary to increase the fluidity of the resin at the time of multilayer lamination molding, and it is desirable to apply a thermosetting resin such as an epoxy resin.
[0005]
However, the epoxy resin exhibits high fluidity because of its low molecular weight before molding, and does not have the property of forming a sheet-like insulating material. Therefore, in the past, a prepreg obtained by impregnating a reinforcing substrate such as a glass cloth with an insulating resin was prepared in advance, and this was used for an insulating layer. However, it has been difficult to meet the above requirements with the conventional prepreg. .
Currently, the glass cloth generally used for prepregs has a larger gap between yarns (glass fiber bundles) as its thickness is reduced. For this reason, the thinner the cloth is, the more likely it is to bend (a phenomenon in which the yarn is bent or the warp and the weft that should intersect at right angles do not intersect at right angles). Due to this bend, abnormal dimensional changes and warpage are likely to occur after hot pressing. Further, the thinner the glass cloth, the larger the gap between the yarns, and the lower the volume fraction of the prepreg fibers, so the rigidity of the interlayer insulating layer decreases. For this reason, there is a problem that the deflection is likely to increase in the component mounting process after the circuit of the outer layer is processed.
At present, the thinnest glass cloth generally used is a 30 μm cloth, and the thickness of a prepreg using this is about 40 μm. If the resin content is reduced in order to reduce the thickness of the prepreg more than this, the hole filling property by the resin to the unevenness of the inner layer circuit is lowered and a void is generated. Further, if the glass cloth is made thinner than this, the strength of the cloth itself is lowered, so that the glass cloth is easily broken in the step of impregnating the glass cloth with the resin, making it difficult to produce the prepreg. Furthermore, the multilayer printed wiring board produced using the prepreg using these glass cloths is likely to run out of the core due to the glass cloth that is unevenly distributed during the small-diameter drilling process, and the drill is easy to fold. Further, due to the presence of glass fiber, the drilling ability by laser is poor, and the irregularities of the inner layer circuit tend to appear on the surface, and the surface flatness is poor. Therefore, the current glass cloth base material prepreg cannot meet the increasing demand for higher density and thinner multilayer printed wiring boards.
[0006]
On the other hand, the adhesive film which is a prepreg without a glass cloth and the adhesive film with copper foil can be made thinner, and is excellent in small diameter drilling workability, laser hole workability and surface flatness. However, since the multilayer printed wiring board produced with these prepregs has no glass cloth substrate in the outer insulating layer, the rigidity is extremely low. This low rigidity is extremely remarkable at high temperatures, and is likely to bend in the component mounting process, and the wire bonding property is extremely poor. In addition, there is no glass cloth substrate in the outer insulating layer, and the thermal expansion coefficient is large. And many problems such as easy breakage. Therefore, the use of an adhesive film that is a prepreg without a glass cloth or an adhesive film with copper foil cannot meet the increasing demand for higher density and thinner multilayer printed wiring boards.
[0007]
Therefore, as a new insulating material to solve the problems of high density, thinning, high reliability, and low cost for multilayer printed wiring boards that cannot be solved by conventional prepreg, it does not include a substrate such as glass cloth, It has been found that a sheet-like insulating material obtained by casting a varnish obtained by dispersing electrically insulating whiskers for maintaining a shape in an insulating resin onto a carrier substrate is effective.
[0008]
However, electrical insulating whiskers have the property of agglomerating in the dry state, and in order to disperse the electrical insulating whiskers in the insulating resin, special kneading equipment is necessary or the surface treatment of the electrical insulating whiskers is appropriate. However, there is a problem that even if such measures are taken, the aggregate of electrically insulating whiskers cannot be eliminated.
[0009]
In addition, in multilayer printed wiring boards, the thickness of the insulating layer is set to be equal to or greater than the thickness of the inner layer circuit to ensure the inner layer circuit fillability. To reduce the overall thickness of the multilayer printed wiring board, insulation is required. Since it is desired to make it as thin as possible within a range that can ensure the properties, the thickness of the insulating layer is usually 25 to 100 μm, and at least 25 μm. By the way, the size (length) of the aggregates of electrically insulating whiskers is over 50 μm for long ones when the average length is specified as 30 μm and some of them exceed 300 μm. there were. When a sheet-like insulating material using such an electric insulating whisker is applied to a multilayer wiring board, use a varnish containing the long electric insulating whisker or the agglomerated electric insulating whisker. Thus, there is a problem in that long electrically insulating whiskers or aggregates of electrically insulating whiskers are brought into contact between conductors, resulting in an insulation failure similar to CAF (Conductive Anodized Filament).
[0010]
An object of this invention is to provide the manufacturing method of the insulating varnish excellent in electrical insulation.
[0011]
[Means for Solving the Problems]
The method for producing an insulating varnish of the present invention is characterized in that a resin varnish containing electrically insulating whiskers is purified through a filter.
[0012]
The electrically insulating whisker is preferably a ceramic whisker having an average diameter of the whisker in the range of 0.3 to 3.0 μm and an average length of 3 to 50 μm. It is preferable to use a filter having a gap of 50 to 100 μm, and more preferably a Tyler 170 to 270 mesh.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
(Whisker)
The whisker used in the present invention is an electrically insulating ceramic whisker and preferably has an elastic modulus of 200 GPa or more. If it is less than 200 GPa, sufficient rigidity cannot be obtained when a multilayer printed wiring board is used.
[0014]
As the types of whiskers, for example, one or more selected from aluminum borate, wollastonite, potassium titanate, basic magnesium sulfate, silicon nitride, and α-alumina can be used. Among them, the aluminum borate whisker has an elastic modulus of about 400 GPa, which is much higher than that of glass, has a small thermal expansion coefficient, and is relatively inexpensive. The printed wiring board produced using the prepreg of the present invention using this aluminum borate whisker has higher rigidity at room temperature and high temperature than the conventional printed wiring board using glass cloth, and has excellent wire bonding properties. Excellent electrical signal transmission characteristics, low thermal expansion coefficient, and excellent dimensional stability. Therefore, aluminum borate is the most suitable material for the whisker used in the present invention.
[0015]
When the average diameter of the whisker is less than 0.3 μm, mixing with the resin varnish becomes difficult and the coating workability is deteriorated. When it exceeds 3 μm, the flatness of the surface is adversely affected and the whisker is microscopically uniform. Dispersibility is impaired. Therefore, the average diameter of the whisker is preferably in the range of 0.3 μm to 3 μm. Furthermore, the average diameter is more preferably in the range of 0.5 μm to 1 μm because of the same reason and good coatability (easy to apply smoothly). By selecting whiskers having such a diameter, it is possible to obtain a printed wiring board having a surface flatness superior to that of using a prepreg based on a conventional glass cloth.
[0016]
Moreover, it is preferable that the average length of a whisker is 10 times or more of an average diameter. If it is less than 10 times, the reinforcing effect as a fiber becomes small, and at the same time, it becomes difficult to perform two-dimensional orientation in a resin layer of a whisker, which will be described later, so that sufficient rigidity cannot be obtained when a wiring board is formed. However, if the whisker is too long, uniform dispersion in the varnish becomes difficult, and coatability is lowered.
[0017]
In addition, there is a high probability that whiskers that are in contact with one conductor circuit will be in contact with other conductor circuits, and there is a possibility of causing a short circuit accident due to migration of copper ions that tend to move along the fiber. There's a problem. Therefore, the average length of whiskers is preferably 50 μm or less. A printed wiring board produced using the insulating material of the present invention using such length whiskers is superior in migration resistance to a printed wiring board using a prepreg based on a conventional glass cloth.
[0018]
In order to further increase the rigidity and heat resistance of the printed wiring board, it is also effective to use whiskers that are surface-treated with a silane coupling agent. Whisker surface-treated with a coupling agent has excellent wettability and bondability with the resin, and can improve rigidity and heat resistance. As the coupling agent used at this time, known ones such as silicon, titanium, aluminum, zirconium, zircoaluminum, chromium, boron, phosphorus, and amino acid can be used.
[0019]
(resin)
The resin used in the present invention is a resin used for a prepreg based on a conventional glass cloth and a thermosetting resin used for an adhesive film not containing a glass cloth base or an adhesive film with a copper foil. Can be used. The resin here means a resin, a curing agent, a curing accelerator, a coupling agent (if necessary), and a diluent (if necessary).
[0020]
Since the resin used for the prepreg based on the conventional glass cloth is not capable of forming a film by itself, it is formed as an adhesive layer on one side of the copper foil by coating, and the solvent is removed by heating to remove the resin. When semi-cured, problems such as resin cracking and chipping are likely to occur during processes such as conveyance, cutting and lamination, and the interlayer insulation layer becomes abnormally thin at the inner layer circuit existing part etc. during subsequent hot pressing. Conventionally, it has been difficult to use for an adhesive film with a copper foil because troubles such as a decrease in insulation resistance and a short circuit are likely to occur.
[0021]
However, in the present invention, since the whisker is dispersed in the resin and the resin is reinforced by the whisker, the prepreg layer composed of the resin of the present invention and the whisker exhibits film forming ability, and is conveyed, cut and laminated. During the process, troubles such as cracking or missing of the resin are unlikely to occur, and the presence of whiskers can prevent the phenomenon that the interlayer insulating layer becomes abnormally thin during hot pressing.
[0022]
It is also effective to use a resin conventionally used for adhesive films and adhesive films with copper foil. These resins contain a high molecular weight component and the like, so that the resin alone has a film forming ability. However, by dispersing the whisker in the resin according to the present invention, the film forming ability is further improved and the handling property is improved. In addition, the insulation reliability can be further improved. It is also possible to reduce the amount of high molecular weight component added by increasing the film-forming ability by dispersing whiskers, which may improve the heat resistance and adhesiveness of the resin.
[0023]
As the resin type, for example, epoxy resin, bismaleimide triazine resin, polyimide resin, phenol resin, melamine resin, silicon resin, unsaturated polyester resin, cyanate ester resin, isocyanate resin or various modified resins thereof are suitable. It is. Among these, bismaleimide triazine resin and epoxy resin are particularly preferable in terms of printed wiring board characteristics. As the epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolak type epoxy resin, salicylaldehyde novolak type epoxy resin, Bisphenol F novolac type epoxy resin, alicyclic epoxy resin, glycidyl ester type epoxy resin, glycidyl amine type epoxy resin, hydantoin type epoxy resin, isocyanurate type epoxy resin, aliphatic cyclic epoxy resin and their halides, hydrogenated products , And mixtures of the resins are preferred. Of these, bisphenol A novolac type epoxy resins or salicylaldehyde novolac type epoxy resins are preferred because of their excellent heat resistance.
[0024]
(Curing agent)
As the curing agent for such a resin, those conventionally used can be used. When the resin is an epoxy resin, for example, dicyandiamide, bisphenol A, bisphenol F, polyvinylphenol, phenol novolac resin, bisphenol A novolac resin and Halides, hydrides, etc. of these phenol resins can be used. Of these, bisphenol A novolac resins are preferred because of their excellent heat resistance.
The ratio of the curing agent to the resin may be a ratio conventionally used, and is preferably in the range of 2 to 100 parts by weight with respect to 100 parts by weight of the resin, and further 2 to 5 parts by weight of dicyandiamide. For other curing agents, the range of 30 to 80 parts by weight is preferred. If it is less than 2 parts by weight, sufficient curing cannot be obtained, and if it exceeds 100 parts by weight, an excess curing agent remains, which may reduce the electrical characteristics of the cured product.
[0025]
(Curing accelerator)
As the curing accelerator, when the resin is an epoxy resin, an imidazole compound, an organic phosphorus compound, a tertiary amine, a quaternary ammonium salt, or the like is used.
The ratio of the curing accelerator to the resin may be a conventionally used ratio, preferably 0.01 to 20 parts by weight, more preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the resin. More preferred. If it is less than 0.01 part by weight, curing is remarkably slowed, and if it exceeds 20 parts by weight, the curing rate becomes so high that the curing reaction cannot be controlled.
[0026]
(Diluent)
The thermosetting resin of the present invention can be diluted with a solvent and used as a resin varnish. As such a solvent, acetone, methyl ethyl ketone, toluene, xylene, methyl isobutyl ketone, ethyl acetate, ethylene glycol monomethyl ether, methanol, ethanol, N, N-dimethylformamide, N, N-dimethylacetamide and the like can be used.
The ratio of the diluent to the resin may be a ratio conventionally used, preferably 1 to 200 parts by weight, more preferably 30 to 100 parts by weight with respect to 100 parts by weight of the resin. If it is less than 1 part by weight, there is no effect as a diluent, and if it exceeds 200 parts by weight, the viscosity of the resin composition is too low and it becomes difficult to apply to a copper foil or a carrier film.
[0027]
(Other ingredients)
Furthermore, in the present invention, conventionally known coupling agents, fillers, flame retardants and the like may be appropriately blended in the resin, if necessary, in addition to the above-described components.
[0028]
(Ratio of resin and whisker)
If the blending amount of the electrically insulating whiskers in the resin is less than 5 parts by weight based on 100 parts by weight of the resin solids, this prepreg is not easy to handle, such as the resin being finely crushed and being scattered during cutting. When it is made into a plate, sufficient rigidity cannot be obtained. On the other hand, if the blending amount of the whisker is 350 parts by weight or more, the hole filling property of the inner layer circuit during hot pressing and the resin filling property between the circuits are impaired, and voids and blurring occur in the whisker composite resin layer after hot pressing. Is likely to occur, and the wiring board characteristics may be impaired. Therefore, the blending amount of the whisker is preferably 5 to 350 parts by weight with respect to 100 parts by weight of the resin solid content. Furthermore, it is excellent in filling the inner layer circuit and filling resin between the circuits, and the manufactured wiring board has the same or equivalent rigidity compared to the wiring board manufactured using the conventional glass cloth prepreg. For reasons of having dimensional stability and wire bonding properties, it is more preferable that the amount of whisker is 30 to 230 parts by weight with respect to 100 parts by weight of the resin solid content.
[0029]
(Carrier film)
In the present invention, as a carrier film which is a target for forming a whisker composite resin layer (B stage state) which is an insulating layer on one side thereof, a metal foil such as a copper foil or an aluminum foil, a polyester film, a polyimide film, or the metal foil And what processed the surface of the film with the mold release agent is used.
[0030]
(Whisker orientation)
The whisker in the insulating material composed of the electrically insulating whisker of the present invention and the B-stage resin is in a state close to two-dimensional orientation (the state in which the whisker's axial direction is close to the plane formed by the insulating material layer) ) Is preferable. Specifically, it is preferable to orient the fiber axes of 70% or more of all whiskers in the semi-cured resin in a direction within ± 30 degrees with respect to the plane direction of the insulating material. By orienting the whiskers in this way, the insulating material of the present invention can obtain good handling properties, and at the same time, can obtain high rigidity and good dimensional stability and surface flatness when formed into a wiring board.
[0031]
(Coating method)
In order to orient the whiskers as described above, whisker having a fiber length in the preferred range described above is used, and at the same time, when coating a resin varnish containing whiskers on a copper foil, blade coater, rod coater, knife coater, squeeze A coating method that can apply a shearing force in a plane direction parallel to the copper foil, such as a coater, a reverse roll coater, a transfer roll coater, or a compressive force in a direction perpendicular to the surface of the copper foil may be employed.
[0032]
(Function)
The method for producing an insulating varnish of the present invention is to separate electrically insulating whisker aggregates of a specified size or more by optimizing the mesh size of the filter, and to electrically insulate the insulating material obtained by combining the electrically insulating whiskers. Mixing of whisker aggregates can be suppressed at the stage of the insulating varnish, and the insulating reliability of the insulating material can be improved.
[0033]
In addition, since the insulating layer produced using the insulating material of the present invention is a fine whisker that has a better workability with respect to laser than glass, the insulating layer using a conventional glass cloth prepreg Laser drilling, which was difficult, can be easily performed. Therefore, an interstitial via hole (IVH) having a small diameter of 100 μm or less can be easily manufactured, the circuit of the printed wiring board can be miniaturized, and it can greatly contribute to high density and high performance of electronic devices.
[0034]
【Example】
Example 1
(Insulating varnish)
70 parts by weight of bisphenol A novolak type epoxy resin (molecular weight: 1200, epoxy equivalent; 206), 30 parts by weight of bisphenol A novolac resin (molecular weight: 600, hydroxyl equivalent: 118), 2-ethyl-4-methylimidazole A resin varnish composed of 0.5 parts by weight of methyl ethyl ketone and 70 parts of methyl ethyl ketone, and an aluminum borate whisker having an average diameter of 0.8 μm and an average fiber length of 20 μm are blended so as to be 90 parts by weight based on 100 parts by weight of the resin solid content. The aluminum borate whisker was stirred until it was uniformly dispersed in the varnish. This was passed through a 200 mesh nylon filter to separate and remove whisker aggregates having a size of 50 μm or more.
[0035]
(Adhesive film)
An insulating varnish from which whisker aggregates of 50 μm or more are separated and removed is applied to a copper foil having a thickness of 18 μm and a polyethylene terephthalate (hereinafter referred to as PET) film having a thickness of 50 μm with a knife coater and heated at a temperature of 150 ° C. for 10 minutes. Drying to remove the solvent and semi-curing of the resin, two types of adhesive films with copper foil with an adhesive layer thickness of 50 μm and 100 μm, and two types of adhesive layers with an adhesive layer thickness of 50 μm and 100 μm An adhesive film with a PET film is prepared, and the PET film is peeled off from the adhesive film with a PET film. The adhesive film is made of an epoxy resin having a whisker volume fraction of 30% and semi-cured with the whisker. A 100 μm adhesive film was prepared.
The produced adhesive film with copper foil could be cut cleanly with a cutter knife and shear without scattering of the resin and the like, and the adhesive films did not block each other and had good handleability. In addition, the adhesive film produced by coating on the PET film has no troubles such as cracking at the time of peeling or normal handling of the PET film, and can be cut cleanly with a cutter knife and shear without scattering of the resin. The blocking between each other did not occur, and the handleability was good.
[0036]
(Electrical corrosion test)
Next, unnecessary portions of the copper foil of the glass epoxy double-sided copper-clad laminate with a thickness of 0.8 mm were removed by etching to form a pattern to be an electrode on the inner layer surface of the electrolytic corrosion test. An adhesive film with a copper foil with an adhesive layer thickness of 50 μm is laminated and laminated so that the adhesive film is in contact with the pattern which becomes the electrode on the inner surface of the electric corrosion test, and conditions of 170 ° C., 2.5 MPa, 60 minutes Was hot-press molded. An unnecessary portion of the copper foil of the obtained laminate is removed by etching, and a pattern that becomes the electrode of the outer layer is formed in a portion corresponding to the position of the electrode corrosion test pattern that becomes the electrode of the inner layer. Obtained. As a result of applying a voltage of 50 V between the inner layer and outer layer electrodes and measuring the insulation resistance value after 1000 hours in an atmosphere of 85 ° C. and 85% RH, 10 9 A good value of Ω or more was shown, and it was confirmed that the adhesive film was excellent in electric corrosion resistance.
(Flexural modulus)
In addition, a single-side roughened copper foil having a thickness of 18 μm is laminated on the upper and lower sides of the produced adhesive film having a thickness of 100 μm so that the roughened surface faces the adhesive film, and the conditions are 170 ° C., 2.5 MPa, and 60 minutes. Was hot-press molded. When the copper foil of the obtained copper-clad laminate was removed by etching and the flexural modulus was measured by three-point bending, it was 20 GPa (no copper foil, average length).
(Drilling accuracy)
Further, when the amount of slip of the drill was measured as a deviation amount of the hole positions of the uppermost plate and the lowermost plate when drilling 10 copper-clad laminates by using a drill having a diameter of 0.3 mm, 20 μm It was the following.
[0037]
(Multilayer printed wiring board)
A circuit is formed by etching away unnecessary portions of the copper foil of the copper-clad laminate, and the adhesive film of the present invention having a thickness of 50 μm previously produced is stacked on both sides thereof, and further on one side having a thickness of 18 μm. The roughened copper foil was laminated so that the roughened surface faced the adhesive film, and hot pressed under conditions of 170 ° C., 2.5 MPa, 60 minutes to produce a multilayer copper-clad laminate with an inner layer circuit.
When the surface roughness of this multilayer copper clad laminate with an inner layer circuit was measured with a stylus type surface roughness meter, the measurement location was a straight line with a length of 25 mm including a portion with and without an inner layer circuit immediately below it. On the surface of the outer layer on the line, the 10-point average of the step difference between the portion having the inner layer circuit and the portion not having the inner layer circuit was 3 μm or less, and had good surface flatness that did not hinder circuit processing.
Further, a hole having a diameter of 75 μm is formed by etching at a predetermined position of the surface copper foil of the multilayer copper clad laminate containing the inner layer circuit, and the hole is drilled by using an impact laser manufactured by Sumitomo Heavy Industries, Ltd. After desmear treatment with acid and electroless plating, an etching resist pattern was formed, and unnecessary copper was removed by etching to form a circuit.
An adhesive film having a thickness of 50 μm is laminated on both surfaces of the multilayer printed wiring board, and a single-sided roughened copper foil having a thickness of 18 μm is laminated on the outer side of the multilayer printed wiring board so that the roughened surface faces the adhesive film. Hot press molding at 5 MPa for 60 minutes to produce a multilayer copper-clad laminate with inner layer circuit, drill a hole with a diameter of 75 μm at a predetermined position, and impact laser manufactured by Sumitomo Heavy Industries, Ltd. Holes were used, desmeared with permanganic acid, electroless plating, an etching resist pattern was formed, and unnecessary copper was removed by etching to form a circuit. The above process was repeated to produce a 10-layer printed wiring board.
[0038]
(Multilayer printed wiring board test)
A part of this multilayer printed wiring board was cut out, and its thermal expansion coefficient and bending elastic modulus were measured. The thermal expansion coefficient was measured by TMA, and the flexural modulus was measured by DMA bending mode. The average coefficient of thermal expansion in the vertical direction was 10 ppm / ° C. (at room temperature), and the average bending elastic modulus in the vertical direction was 60 GPa at normal temperature and 40 GPa at high temperature (200 ° C.). Moreover, the surface hardness by a Barcol hardness tester was 65 at normal temperature and 50 at high temperature (200 degreeC).
(Wire bonding property)
Furthermore, a bare chip was mounted on a part of this 10-layer printed wiring board and connected to the surface circuit by wire bonding. As for the wire bonding conditions, when the ultrasonic output was 1 W, the ultrasonic output time was 50 μs, the bond load was 100 g, and the wire bonding temperature was 180 ° C., the wire bonding was good.
(Thermal shock test)
Further, an IC chip (TSOP) having a size of 8 × 20 mm is connected to the surface circuit via solder on this 10-layer printed wiring board, and the substrate on which the IC chip (TSOP) is mounted is set at −65 ° C. for 30 minutes and 150 minutes. When evaluated by a thermal shock test in which exposure to an environment at 30 ° C. for 30 minutes was one cycle, defects such as disconnection did not occur in the solder joint even after 2,000 cycles. In addition, a continuity test of the circuit including the interstitial via hole inside the substrate was conducted, but there was no trouble such as disconnection.
[0039]
Example 2
(varnish)
70 parts by weight of salicylaldehyde novolac type epoxy resin (molecular weight: 1000, epoxy equivalent; 180), 30 parts by weight of bisphenol A novolac resin (molecular weight: 700, hydroxyl equivalent: 118), and N-methylimidazole as a curing accelerator 90 parts by weight of an aluminum borate whisker having an average diameter of 0.8 μm and an average fiber length of 20 μm with respect to 100 parts by weight of resin solids, in a resin varnish comprising 0.5 parts by weight of methyl ethyl ketone and 70 parts by weight of methyl ethyl ketone, Stir until the aluminum borate whiskers are uniformly dispersed in the varnish.
This was passed through a 200-mesh nylon filter to separate and remove whisker aggregates having a size of 50 μm or more.
[0040]
(Adhesive film)
The insulating varnish from which whisker aggregates of 50 μm or more are separated and removed is applied to a 18 μm thick copper foil and a 50 μm thick PET film with a knife coater, and dried by heating at a temperature of 150 ° C. for 10 minutes to remove the solvent. At the same time, the resin is semi-cured to produce two types of adhesive films with copper foil with an adhesive layer thickness of 50 μm and 100 μm, and two types of adhesive films with PET film with an adhesive layer thickness of 50 μm and 100 μm. Then, the PET film is peeled and removed from the adhesive film with a PET film to produce two types of adhesive films having a thickness of 50 μm and 100 μm made of epoxy resin in a semi-cured state with a whisker volume fraction of 30%. did.
The produced adhesive film with copper foil could be cut cleanly with a cutter knife and shear without scattering of the resin and the like, and the adhesive films did not block each other and had good handleability. In addition, the adhesive film produced by coating on the PET film has no troubles such as cracking at the time of peeling or normal handling of the PET film, and can be cut cleanly with a cutter knife and shear without splashing the resin. The blocking between each other did not occur, and the handleability was good.
[0041]
(Electrical corrosion test)
Next, unnecessary portions of the copper foil of the glass epoxy double-sided copper clad laminate having a thickness of 0.8 mm are removed by etching, and a pattern to be an electrode on the inner layer surface of the electrolytic corrosion test is produced by etching. The adhesive film with a thickness of 50 μm of the adhesive layer produced in step 1 was laminated so that the adhesive film was in contact with the pattern that would be the electrode on the inner layer surface of the electrolytic corrosion test, and 170 ° C., 2.5 MPa, 60 minutes. Hot pressing was performed under the conditions. A pattern to be an electrode for the outer layer was formed by etching on a portion of the obtained laminate that was aligned with the position of the electrode corrosion test pattern to be an electrode for the inner layer, to obtain an electric corrosion test piece. As a result of applying a voltage of 50 V between the inner layer and outer layer electrodes and measuring the insulation resistance value after 1000 hours in an atmosphere of 85 ° C. and 85% RH, 10 9 A good value of Ω or more was shown, and it was confirmed that the adhesive film was excellent in electric corrosion resistance.
(Flexural modulus)
Also, a single-side roughened copper foil with a thickness of 18 μm is laminated on the top and bottom of the produced adhesive film with a thickness of 100 μm so that the roughened surface faces the adhesive film, and the conditions are 170 ° C., 2.5 MPa, 60 minutes. Hot pressing was performed. When the copper foil of the obtained copper-clad laminate was removed by etching and the flexural modulus was measured by three-point bending, it was 20 GPa (no copper foil, average length).
(Drilling accuracy)
Further, the amount of slip of the drill was measured as the amount of deviation of the hole positions of the uppermost plate and the lowermost plate when drilling 10 copper-clad laminates using a drill having a diameter of 0.3 mm. It was the following.
[0042]
(Multilayer printed wiring board)
An unnecessary portion of the copper foil of the copper-clad laminate is removed by etching to form a circuit, the adhesive film having a thickness of 50 μm previously formed is overlapped on both sides thereof, and further roughened on one side with a thickness of 18 μm on the outer side. The copper foil was laminated so that the roughened surface faced the adhesive film, and hot pressed under conditions of 170 ° C., 2.5 MPa, 60 minutes to produce a multilayer copper-clad laminate with an inner layer circuit.
When the surface roughness of this multilayer copper clad laminate with inner layer circuit was measured with a stylus type surface roughness meter, the measurement location was on a straight line of 25 mm in length including the portion with and without the inner layer circuit immediately below it. On the surface of the outer layer, the 10-point average of the step difference between the portion with and without the inner layer circuit was 3 μm or less, and it had good surface flatness that did not hinder circuit processing.
Further, a hole having a diameter of 75 μm is formed by etching at a predetermined position of the surface copper foil of the multilayer copper clad laminate containing the inner layer circuit, and the hole is irradiated with an impact laser manufactured by Sumitomo Heavy Industries, Ltd. After performing desmear treatment with acid and performing electroless plating, an etching resist pattern was formed and unnecessary copper was removed by etching to form a circuit.
The above-mentioned adhesive film having a thickness of 50 μm is again laminated on both surfaces of the multilayer printed wiring board, and further, a single-side roughened copper foil having a thickness of 18 μm is laminated on the outer side so that the roughened surface faces the adhesive film. , 2.5MPa, hot press molding for 60 minutes to produce a multilayer copper-clad laminate with inner layer circuit, drill a hole with a diameter of 75μm at a predetermined position, made by Sumitomo Heavy Industries, Ltd. After drilling with an impact laser, desmearing with permanganic acid, and electroless plating, an etching resist pattern was formed, and unnecessary copper was removed by etching to form a circuit. The above process was repeated to produce a 10-layer printed wiring board.
[0043]
(Multilayer printed wiring board test)
A part of this multilayer printed wiring board was cut out, and its thermal expansion coefficient and bending elastic modulus were measured. The thermal expansion coefficient was measured by TMA, and the flexural modulus was measured by DMA bending mode. The average coefficient of thermal expansion in the vertical direction was 10 ppm / ° C. (at room temperature), and the average bending elastic modulus in the vertical direction was 60 GPa at normal temperature and 50 GPa at high temperature (200 ° C.). Moreover, the surface hardness by a Barcol hardness tester was 65 at normal temperature and 55 at high temperature (200 degreeC).
(Wire bonding property)
Furthermore, a bare chip was mounted on a part of this 10-layer printed wiring board and connected to the surface circuit by wire bonding. As for the wire bonding conditions, when the ultrasonic output was 1 W, the ultrasonic output time was 50 μs, the bond load was 100 g, and the wire bonding temperature was 180 ° C., the wire bonding was good.
(Thermal shock test)
In addition, an IC chip (TSOP) having a size of 8 × 20 mm is connected to the surface circuit via solder on the 10-layer printed wiring board, and the substrate on which the IC chip (TSOP) is mounted is at −65 ° C. for 30 minutes and 150 ° C. In a thermal shock test in which exposure to an environment of 30 minutes was taken as one cycle, no defects such as wire breakage occurred in the solder joint even after 2000 cycles. In addition, a continuity test of the circuit including the interstitial via hole inside the substrate was conducted, but there was no trouble such as disconnection.
[0044]
Comparative Example 1
(varnish)
70 parts by weight of bisphenol A novolac type epoxy resin (molecular weight: 1200, epoxy equivalent: 206), 30 parts by weight of bisphenol A novolac resin (molecular weight: 700, hydroxyl equivalent: 118), and 2-ethyl-4-methylimidazole An aluminum borate whisker having an average diameter of 0.8 μm and an average fiber length of 20 μm is added to a resin varnish composed of 0.5 parts by weight and 70 parts by weight of methyl ethyl ketone so as to be 90 parts by weight with respect to 100 parts by weight of the resin solid content. And stirred until the aluminum borate whisker was uniformly dispersed in the varnish.
(Adhesive film)
The insulating varnish was applied to a 18 μm thick copper foil and a 50 μm thick PET film with a knife coater without passing through a 200-mesh nylon filter, and dried by heating at a temperature of 150 ° C. for 10 minutes. While removing, semi-curing the resin, two types of adhesive film with copper foil with an adhesive layer thickness of 50 μm and 100 μm, and two types of adhesive film with PET film with an adhesive layer thickness of 50 μm and 100 μm Then, the PET film was removed from the adhesive film with a PET film by peeling to produce an adhesive film having a whisker volume fraction of 30% and a whisker and a semi-cured epoxy resin having a thickness of 50 μm and 100 μm. .
The produced adhesive film with copper foil could be cut cleanly with a cutter knife and shear without scattering of the resin and the like, and the adhesive films did not block each other and had good handleability. In addition, the adhesive film produced by coating on the PET film has no troubles such as cracking at the time of peeling or normal handling of the PET film, and can be cut cleanly with a cutter knife and shear without splashing the resin. The blocking between each other did not occur, and the handleability was good.
[0045]
(Electrical corrosion test)
Next, unnecessary portions of the copper foil of the glass epoxy double-sided copper-clad laminate with a thickness of 0.8 mm are removed by etching to form a pattern to be an electrode on the inner layer surface of the electrolytic corrosion test. The laminated insulating film having a thickness of 50 μm is overlapped so that the adhesive film is in contact with the pattern which becomes the electrode on the inner layer surface of the electric corrosion test, and the roughened adhesive film is coated with a single-side roughened copper foil having a thickness of 18 μm. The layers were laminated so as to face each other and subjected to hot press molding under the conditions of 170 ° C., 2.5 MPa, and 60 minutes. On the portion of the obtained laminated plate corresponding to the position of the electrolytic corrosion test pattern that becomes the inner layer electrode, unnecessary copper foil was removed by etching to form a pattern that became the outer layer electrode to obtain an electrolytic corrosion test piece. . As a result of applying a voltage of 50 V between the inner layer and outer layer electrodes and tracking the change with time in an atmosphere of 85 ° C. and 85% RH, the insulation resistance value after 250 hours was 10 9 It became less than Ω, and it was found that the adhesive film was inferior in electric corrosion resistance.
(Flexural modulus)
A single-sided roughened copper foil with a thickness of 18 μm was laminated on top and bottom of the prepared adhesive film with a thickness of 100 μm so that the roughening would face the adhesive film, and hot pressing was performed at 170 ° C., 2.5 MPa, for 60 minutes. . When the copper foil of the obtained copper-clad laminate was removed by etching and the flexural modulus was measured by three-point bending, it was 20 GPa (no copper foil, average length).
(Drilling accuracy)
Further, when the amount of slip of the drill was measured as the amount of deviation between the hole positions of the uppermost plate and the lowermost plate when drilling 10 copper-clad laminates using a drill having a diameter of 0.3 mm, the thickness was 20 μm or less. Met.
[0046]
(Multilayer printed wiring board)
Unnecessary portions of the copper foil of this copper-clad laminate are removed by etching, a circuit is formed, an adhesive film having a thickness of 50 μm previously formed is superimposed on both sides, and a single-side roughening with a thickness of 18 μm is further provided on the outer side. The copper foil was laminated so that the roughened surface faced the adhesive film, and hot pressed under conditions of 170 ° C., 2.5 MPa, 60 minutes to produce a multilayer copper-clad laminate with an inner layer circuit.
When the surface roughness of this multilayer copper clad laminate with inner layer circuit was measured with a stylus type surface roughness meter, the measurement location was on a straight line of 25 mm in length including the portion with and without the inner layer circuit immediately below it. On the surface of the outer layer, the 10-point average of the step difference between the portion having the inner layer circuit and the portion not having the inner layer circuit was 3 μm or less, and had good surface flatness that did not hinder circuit processing. Further, a hole having a diameter of 75 μm is formed by etching at a predetermined position of the surface copper foil of the multilayer copper clad laminate containing the inner layer circuit, and the hole is drilled by using an impact laser manufactured by Sumitomo Heavy Industries, Ltd. After performing desmearing by electroless plating, an etching resist pattern was formed, and unnecessary copper was removed by etching to form a circuit.
The above-mentioned adhesive film having a thickness of 50 μm is again laminated on both surfaces of the multilayer printed wiring board, and further, a single-side roughened copper foil having a thickness of 18 μm is laminated on the outer side so that the roughened surface faces the adhesive film. , 2.5 MPa, hot press molding for 60 minutes to produce a multilayer copper clad laminate with an inner layer circuit, and a hole with a diameter of 75 μm is made by etching at a predetermined position of the copper foil. Sumitomo Heavy Industries, Ltd. Drilling was performed using an impact laser manufactured by Co., Ltd., desmear treatment with permanganic acid was performed, and electroless plating was performed. Then, an etching resist pattern was formed, and unnecessary copper was removed by etching to form a circuit. The above process was repeated to produce a 10-layer printed wiring board.
(Multilayer printed wiring board test)
A part of this multilayer printed wiring board was cut out, and its thermal expansion coefficient and bending elastic modulus were measured. The thermal expansion coefficient was measured by TMA, and the flexural modulus was measured by DMA bending mode. The average coefficient of thermal expansion in the vertical direction was 10 ppm / ° C. (at room temperature), and the average bending elastic modulus in the vertical direction was 60 GPa at normal temperature and 40 GPa at high temperature (200 ° C.). Moreover, the surface hardness by a Barcol hardness tester was 65 at normal temperature and 50 at high temperature (200 degreeC).
(Wire bonding property)
Furthermore, a bare chip was mounted on a part of this 10-layer printed wiring board and connected to the surface circuit by wire bonding. As for the wire bonding conditions, when the ultrasonic output was 1 W, the ultrasonic output time was 50 μs, the bond load was 100 g, and the wire bonding temperature was 180 ° C., the wire bonding was good.
(Thermal shock test)
In addition, an IC chip (TSOP) having a size of 8 × 20 mm is connected to the surface circuit via solder on the 10-layer printed wiring board, and the substrate on which the IC chip (TSOP) is mounted is set at −65 ° C. for 30 minutes. When evaluated by a thermal shock test in which exposure to an environment at 150 ° C. for 30 minutes was one cycle, defects such as disconnection did not occur in the solder connection part even after 2000 cycles.
In addition, a continuity test of the circuit including the interstitial via hole inside the substrate was conducted, but there was no trouble such as disconnection.
[0047]
Comparative Example 2
(Prepreg)
70 parts by weight of bisphenol A novolac type epoxy resin (molecular weight: 1200, epoxy equivalent: 206), 30 parts by weight of bisphenol A novolac resin (molecular weight: 700, hydroxyl equivalent: 118), 2-ethyl-4-methylimidazole A resin varnish consisting of 0.5 parts by weight and 70 parts by weight of methyl ethyl ketone was impregnated and applied to a glass cloth having a thickness of 50 μm and 100 μm, and dried by heating at a temperature of 150 ° C. for 10 minutes to remove the solvent, The resin was semi-cured to prepare glass epoxy prepregs having a thickness of 70 μm and 120 μm, which were composed of a glass cloth and an epoxy resin in a semi-cured state.
In the prepared prepreg, the resin was scattered at the time of cutting with a cutter knife and a shear.
[0048]
(Electrical corrosion test)
Next, unnecessary portions of the copper foil of the glass epoxy double-sided copper-clad laminate having a thickness of 0.8 mm are removed by etching to form a pattern to be an electrode on the inner layer surface of the electrolytic corrosion test. A layer of 50 μm thick epoxy prepreg and 18 μm thick single-sided roughened copper foil were laminated so that the epoxy prepreg was in contact with the pattern of the electrode on the inner layer surface of the electrolytic corrosion test, and 170 ° C., 2.5 MPa, Hot pressing was performed under conditions of 60 minutes. A pattern to be an electrode for the outer layer was formed by etching on a portion of the obtained laminate that was aligned with the position of the electrode corrosion test pattern to be an electrode for the inner layer, to obtain an electric corrosion test piece. As a result of applying a voltage of 50 V between the inner layer and outer layer electrodes and measuring the insulation resistance value after 1000 hours in an atmosphere of 85 ° C. and 85% RH, 10 9 It showed a good value of Ω or more, and confirmed that the fallen product of the epoxy prepreg was excellent in electric corrosion resistance.
(Flexural modulus)
A single-sided roughened copper foil having a thickness of 18 μm was laminated on the upper and lower sides of the produced glass epoxy prepreg having a thickness of 120 μm so that the roughened surface faced the prepreg, and hot pressing was performed. When the copper foil of the obtained copper-clad laminate was removed by etching and the flexural modulus was measured by three-point bending, it was 8 GPa (no copper foil, vertical average).
(Drilling accuracy)
Further, when the amount of deviation between the hole positions of the uppermost plate and the lowermost plate was measured when 10 sheets of this copper-clad laminate were punched with a drill having a diameter of 0.3 mm, the result was 50 μm or more.
[0049]
(Multilayer printed wiring board)
This copper-clad laminate is subjected to circuit processing to produce an inner layer circuit board, the glass epoxy prepreg having a thickness of 50 μm previously prepared on both sides thereof, and a single-side roughened copper foil having a thickness of 18 μm on the outer side thereof are further roughened. Lamination was performed so that the surface faced the prepreg, and hot pressing was performed under conditions of 170 ° C., 2.5 MPa, 60 minutes, to produce a multilayer copper-clad laminate with an inner layer circuit.
When the surface roughness of this multilayer copper clad laminate with inner layer circuit was measured with a stylus type surface roughness meter, the measurement location was on a straight line of 25 mm in length including the portion with and without the inner layer circuit immediately below it. On the surface of the outer layer, the 10-point average of the step difference between the portion with and without the inner layer circuit was 8 μm or more.
Furthermore, a hole with a diameter of 75 μm was made by etching at a predetermined position of the surface copper foil of the multilayer copper clad laminate containing the inner layer circuit, and an attempt was made to make a hole using the impact laser manufactured by Sumitomo Heavy Industries, Ltd. Part could not be removed.
[0050]
Comparative Example 3
(Adhesive film)
50 parts by weight of a high molecular weight epoxy polymer having a weight average molecular weight of 50,000, 50 parts by weight of a bisphenol A type epoxy resin (molecular weight: 1200, epoxy equivalent: 206), and a crosslinking agent for the high molecular weight epoxy polymer 0.2 equivalents of phenol resin masked diisocyanate and 0.5 part by weight of 2-ethyl-4-methylimidazole as a curing agent, a 18 μm thick copper foil and 50 μm thick PET The film was coated with a knife coater, heated and dried at a temperature of 150 ° C. for 10 minutes to remove the solvent, and the resin was semi-cured to form an adhesive film with a copper foil having an adhesive layer thickness of 50 μm, An adhesive film with a PET film with a thickness of 50 μm is prepared, and the PET film is peeled off from the adhesive film with a PET film. An epoxy resin in a thickness of to produce an adhesive film of 50 [mu] m.
The produced adhesive film had no troubles such as cracking during peeling or normal handling of the PET film, and it could be cut cleanly with a cutter knife and shear without scattering of resin, but blocking between prepregs occurred and handled The nature was bad.
[0051]
(Electrical corrosion test)
Next, unnecessary portions of the copper foil of the glass epoxy double-sided copper-clad laminate with a thickness of 0.8 mm are removed by etching to form a pattern to be an electrode on the inner layer surface of the electrolytic corrosion test. The insulating film with a copper foil with a thickness of 50 μm was laminated and laminated so that the adhesive film was in contact with the pattern that would be the electrode on the inner surface of the electric corrosion test, and the conditions were 170 ° C., 2.5 MPa, 60 minutes. Hot pressing was performed. An unnecessary portion of the copper foil of the obtained laminate is removed by etching, and a pattern that becomes the electrode of the outer layer is produced in a portion that matches the position of the electrode corrosion test pattern that becomes the electrode of the inner layer, and an electric corrosion test piece is obtained. It was. As a result of applying a voltage of 50 V between the inner layer and outer layer electrodes and measuring the insulation resistance value after 1000 hours in an atmosphere of 85 ° C. and 85% RH, 10 9 A good value of Ω or more was shown, and it was confirmed that the adhesive film was excellent in electric corrosion resistance.
[0052]
(Multilayer printed wiring board)
The adhesive film having a thickness of 50 μm is laminated on both sides of the inner layer circuit board produced in Comparative Example 1, and a single-sided roughened copper foil having a thickness of 18 μm is further laminated on the outer side so that the roughened surface faces the adhesive film. A multilayer copper-clad laminate with an inner layer circuit was formed by pressure molding.
The surface roughness of the multilayer copper clad laminate containing the inner layer circuit was measured with a stylus type surface roughness meter. The measurement location was the surface of the outer layer on a straight line with a length of 25 mm including a portion with and without an inner layer circuit immediately below. The 10-point average of the step difference between the portion with and without the inner layer circuit was 3 μm or less, and the surface flatness was satisfactory without any problem in circuit processing.
[0053]
Furthermore, a hole with a diameter of 75 μm was made by etching and removing a predetermined position of the surface copper foil of the multilayer copper clad laminate containing the inner layer circuit, and the hole was made using an impact laser manufactured by Sumitomo Heavy Industries, Ltd. After performing desmear treatment with permanganic acid and performing electroless plating, an etching resist pattern was formed by baking and development, and unnecessary copper was removed by etching to form an outer layer circuit.
The adhesive film having a thickness of 50 μm is laminated on both surfaces of the multilayer printed wiring board, and a single-side roughened copper foil having a thickness of 18 μm is further laminated on the outer side so that the roughened surface faces the adhesive film. .5MPa, hot press molding for 60 minutes to produce a multilayer copper-clad laminate with inner layer circuit, etching a predetermined position of the outer layer copper foil to make a 75μm diameter hole, and Sumitomo Heavy Industries Drilling using impact laser manufactured by Kikai Kogyo Co., Ltd., desmear treatment with permanganic acid, electroless plating, etching resist pattern is formed by baking and developing, and unnecessary copper is removed by etching Thus, an outer layer circuit was formed. The above process was repeated to produce a 10-layer printed wiring board.
[0054]
(Multilayer printed wiring board test)
A part of this multilayer printed wiring board was cut out, and its thermal expansion coefficient and bending elastic modulus were measured. The thermal expansion coefficient was measured by TMA, and the flexural modulus was measured by DMA bending mode. The average thermal expansion coefficient in the longitudinal direction was 30 ppm / ° C. (at room temperature), and the average bending elastic modulus in the longitudinal direction was 20 GPa at normal temperature and 10 GPa at high temperature (200 ° C.). Moreover, the surface hardness by a Barcol hardness tester was 30 under normal temperature, and 10 under high temperature (200 degreeC).
(Wire bonding property)
Furthermore, a bare chip was mounted on a part of this 10-layer printed wiring board and connected to the surface circuit by wire bonding. The wire bonding conditions were an ultrasonic output of 1 W, an ultrasonic output time of 50 μs, and a bond load of 100 g. Even when the wire bonding temperature was lowered to 100 ° C., peeling of the wire occurred.
(Thermal shock test)
In addition, a TSOP semiconductor chip having a size of 8 mm × 20 mm is connected to the surface circuit via solder on this 10-layer printed wiring board, and this TSOP mounting substrate is exposed to an environment of −65 ° C. for 30 minutes and 150 ° C. for 30 minutes. When this was evaluated by a thermal shock test with one cycle, a disconnection failure occurred in the solder connection portion around 100 cycles. Further, when a continuity test of the circuit including the interstitial via hole inside the substrate was performed, there was a disconnection portion.
[0055]
【The invention's effect】
According to the method for producing an insulating varnish of the present invention, it is possible to suppress the aggregation of the electrically insulating whisker in the adhesive film obtained by combining the electrically insulating whisker at the stage of the insulating varnish. Reliability can be increased. The adhesive film obtained using the insulating varnish produced according to the present invention was able to form an epoxy resin into a sheet by adding an electrically insulating whisker. Is flat and has good circuit processability, high rigidity, high mounting reliability, high surface hardness, good wire bondability, and low thermal expansion coefficient, resulting in improved dimensional stability. Therefore, the multilayer printed wiring board is greatly contributed to high density, thinning, high reliability, and low cost.
Claims (5)
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09629997A JP3804812B2 (en) | 1997-04-15 | 1997-04-15 | Method for producing insulating varnish |
| US09/057,522 US6197149B1 (en) | 1997-04-15 | 1998-04-09 | Production of insulating varnishes and multilayer printed circuit boards using these varnishes |
| DE69839104T DE69839104D1 (en) | 1997-04-15 | 1998-04-14 | Production of insulating lacquers and multilayer printed circuit boards using them |
| EP19980106742 EP0873047B1 (en) | 1997-04-15 | 1998-04-14 | Production of insulating varnishes and multilayer printed circuit boards using these varnishes |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09629997A JP3804812B2 (en) | 1997-04-15 | 1997-04-15 | Method for producing insulating varnish |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH10287831A JPH10287831A (en) | 1998-10-27 |
| JP3804812B2 true JP3804812B2 (en) | 2006-08-02 |
Family
ID=14161166
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP09629997A Expired - Fee Related JP3804812B2 (en) | 1997-04-15 | 1997-04-15 | Method for producing insulating varnish |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3804812B2 (en) |
-
1997
- 1997-04-15 JP JP09629997A patent/JP3804812B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH10287831A (en) | 1998-10-27 |
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