JP2006339270A - Multilayer printed-wiring board and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a multilayer printed-wiring board capable of improving the adhesiveness between a wiring circuit and the hardened body of a prepreg sufficiently, and to provide the multilayer printed-wiring board. <P>SOLUTION: The multilayer printed-wiring board 1 is manufactured, where the prepreg containing resin and fiber is laminated on the wiring circuit 4 of an internal layer circuit board 6 having a substrate 2 and the wiring circuit 4 provided on the substrate 2, and a laminated structure while the multilayer printed-wiring board 1 has a laminated structure in which the internal layer circuit board 6 is integrated with the hardened body 8 of the prepreg. The method of manufacturing the multilayer printed-wiring board includes a roughening process for roughening a surface 4a by bringing a chemical roughening liquid into contact with the surface 4a of the wiring circuit 4, an oxidation process for oxidizing the surface 4a of the wiring circuit 4 after the roughening process, and a reduction process for reducing the surface 4a of the wiring circuit 4 after the oxidation process. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a multilayer printed wiring board and a multilayer printed wiring board.

  With the miniaturization, weight reduction, and multifunctionality of electrical and electronic components, multilayer printed wiring boards have become denser and higher multilayered. Therefore, there is a demand for a more reliable multilayer printed wiring board having characteristics that can cope with these. One of the required characteristics is adhesion between the wiring circuit and a cured prepreg containing resin.

  FIG. 3 is a cross-sectional view schematically showing an example of a general multilayer printed wiring board that has been conventionally found. A multilayer printed wiring board 100 shown in FIG. 3 includes an inner layer circuit board 10, a prepreg cured body 20 provided on both surfaces of the inner layer circuit board 10, and a metal foil 30 provided on the prepreg cured body 20. Consists of. Inner layer circuit board 10 and prepreg cured body 20 are sandwiched between a pair of metal foils 30.

  The inner layer circuit board 10 includes a substrate 12 and a wiring circuit 14 provided on the substrate 12. The prepreg cured body 20 is provided so as to cover the wiring circuit 14. The prepreg is a semi-cured state in which a moldable resin (for example, an uncured thermosetting resin) is impregnated in a woven or filamentous reinforcing material such as carbon fiber, glass fiber, or aramid fiber. It is a resin sheet.

  In such a method of manufacturing the multilayer printed wiring board 100, generally, the prepreg is bonded to the inner layer circuit board 10, the metal foil 30 is laminated on the prepreg, and the entire circuit board 10 is heated and pressed. A multilayer structure formed by integrating the prepreg cured body 20 is constructed. The inner layer circuit board 10 is manufactured using a base material having a metal foil on both surfaces, such as a double-sided copper-clad laminate (CCL board), and having a smooth gloss surface on the metal foil surface. For this reason, the surface 14a of the wiring circuit 14 obtained by patterning this metal foil is in a state where it is difficult to adhere to the cured prepreg 20 due to its high smoothness.

  Therefore, in order to improve the adhesion between the wiring circuit 14 and the cured prepreg 20, as described in Patent Documents 1 and 2, the surface 14 a of the wiring circuit 14 is brushed and then treated with a coupling agent. There have been proposed a method, a method in which an alkali treatment liquid is brought into contact with the surface 14a of the wiring circuit 14 to give a hydroxyl group, and then a treatment with a coupling agent is performed. However, its adhesiveness has not yet reached a practical level.

  Also, there is a blackening treatment in which the surface 14a is roughened by forming fine needle-shaped cuprous oxide or cupric oxide on the surface 14a of the wiring circuit 14 using an aqueous solution containing an acid as a main component. Generally done. However, when the blackening treatment is used, a phenomenon (haloing phenomenon) occurs in which the acid reacts with the formed cuprous oxide or cupric oxide to form a metal salt and dissolve these. For this reason, in a region where acid erosion has occurred due to this haloing phenomenon, the roughening property of the surface 14a of the wiring circuit 14 is lowered, and the adhesion between the wiring circuit 14 and the cured prepreg 20 is weakened. Arise.

  Moreover, even after bonding, cuprous oxide or cupric oxide is formed on the inner surface or cut surface of the through hole by forming a through hole (through hole; via hole if no component is inserted) or cutting the substrate. When exposed to the above, the same phenomenon occurs due to the acid in the plating solution during the subsequent plating treatment, resulting in a problem that the reliability of the multilayer printed wiring board is lowered. In particular, since the distance between adjacent through holes and the distance between the wiring circuit and the through holes are getting closer in recent years, such a problem tends to occur.

  In order to solve the above blackening problem, for example, by changing the processing conditions with the blackening solution, cupric oxide formed on the copper circuit is made to be cuprous oxide which is difficult to dissolve in acid, organic A method of dissolving and removing cupric oxide with a treatment solution containing a chelating agent, a method of performing reduction treatment to metallic copper using an alkaline reduction solution after blackening treatment (for example, see Patent Documents 3 and 4), and the like. Has been put into practical use.

Also, in recent years, with the thinning of the inner layer circuit board, as an alternative to the blackening treatment method or the treatment method of performing chemical reduction after the blackening treatment, an etching type chemical roughening treatment that etches the copper surface into a needle shape (for example, , See Patent Documents 5 to 8), and a method for improving the adhesion between the wiring circuit and the cured prepreg is also becoming popular.
JP-A-2-277294 JP-A-5-229060 Japanese Patent Publication No. 3-50431 Japanese Patent No. 1574275 Japanese Patent No. 2740768 JP-A-9-411163 JP-A-10-96088 JP-A-11-21517

  However, in recent years, further improvement in the adhesion between the wiring circuit and the cured prepreg has been demanded. Therefore, the present inventors conducted the following examination.

  First, an inner layer circuit board is prepared using an FR-4 copper clad laminate (copper foil thickness 18 μm), and (a) only chemical roughening treatment is applied to the surface of the wiring circuit of the inner layer circuit board. After performing only the treatment, (c) only the blackening treatment and the reduction treatment, a prepreg was laminated on the inner layer circuit board to produce multilayer printed wiring boards (a) to (c). In the obtained multilayer printed wiring boards (a) to (c), the peel strength between the inner layer circuit board and the cured prepreg was measured in accordance with JIS C6481. As a result, the peel strength in the multilayer printed wiring board (a) is 1.0 kN / m, the peel strength in the multilayer printed wiring board (b) is 1.1 kN / m, and the peel strength in the multilayer printed wiring board (c). The strength was 1.0 kN / m. However, when the multilayer printed wiring boards (a) to (c) were allowed to stand at a high temperature for 240 hours in an oven in an air atmosphere, the cured prepreg was peeled off from the wiring circuit.

  Thus, in the multilayer printed wiring board used especially in high temperature conditions, the adhesiveness of a wiring circuit and the hardening body of a prepreg has not yet reached a practical use level.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing a multilayer printed wiring board and a multilayer printed wiring board capable of sufficiently improving the adhesion between a wiring circuit and a cured body of a prepreg. .

  In order to solve the above-described problems, a method for producing a multilayer printed wiring board according to the present invention contains a resin and fibers on the wiring circuit of an inner layer circuit board having a substrate and a wiring circuit provided on the substrate. A method of manufacturing a multilayer printed wiring board having a laminated structure in which a prepreg is laminated and the inner circuit board and the cured body of the prepreg are integrated, wherein a chemical roughening solution is brought into contact with the surface of the wiring circuit. A roughening step for roughening the surface; an oxidation step for oxidizing the surface of the wiring circuit after the roughening step; and a reduction step for reducing the surface of the wiring circuit after the oxidation step.

  In the method for producing a multilayer printed wiring board according to the present invention, since the roughening step, the oxidation step, and the reduction step are sequentially performed, the adhesion between the wiring circuit and the cured prepreg can be sufficiently improved. The reason why the adhesiveness between the wiring circuit and the cured prepreg can be sufficiently improved by the method for producing a multilayer printed wiring board of the present invention is not necessarily clear, but is considered as follows. Since the surface of the wiring circuit roughly roughened by the roughening process is further finely roughened by the oxidation process and the reduction process, it is estimated that fine irregularities are formed on the surface of the wiring circuit.

  The wiring circuit is preferably made of copper as a constituent material. Thereby, the effect of this invention can be acquired more reliably.

  The chemical roughening solution preferably contains 1,2,3-benzotriazole. Thereby, the surface of a wiring circuit can be roughened more reliably.

In particular, for example, when the wiring circuit is made of copper, the surface of the wiring circuit roughened with a chemical roughening solution containing 1,2,3-benzotriazole is obtained from X-ray photoelectron spectroscopy (XPS). , A chemical bond of copper / 1,2,3-benzotriazole presumed to be Cu (C ₆ H ₄ N ₃ ) ₂ was observed. For this reason, for example, when the wiring circuit is made of copper, it is considered that the surface of the wiring circuit is roughened due to the layer of Cu (C ₆ H ₄ N ₃ ) ₂ . In addition, for example, when the chemical roughening solution further contains an acid to form cuprous oxide or cupric oxide, this Cu (C ₆ H ₄ N ₃ ) ₂ layer suppresses acid erosion, thereby preventing halo resistance. It is considered that the multilayer printed wiring board obtained is excellent in solder heat resistance and the like because the ingress property can be improved.

  Moreover, it is preferable that the said chemical roughening liquid further contains a sulfuric acid, hydrogen peroxide, and 5-aminotetrazole.

Thereby, the effect by this invention can be acquired more reliably. The reason for this is not necessarily clear, but in such a chemical roughening solution, sulfuric acid and hydrogen peroxide oxidize the surface of the wiring circuit (hereinafter, such components are referred to as “oxidation promoters”). It is considered that aminotetrazole and 1,2,3-benzotriazole suppress corrosion on the surface of the wiring circuit (hereinafter, such a component is referred to as “corrosion inhibitor”). When the components that antagonize each other at the same time are brought into contact with the surface of the wiring circuit in this way, it is considered that oxidation of the surface by the oxidation accelerator is partially prevented by the corrosion inhibitor. Thereby, it is estimated that the surface of a wiring circuit becomes a very complicated roughened surface. Furthermore, for example, when the wiring circuit uses copper as the constituent material, the chemical roughening solution contains 1,2,3-benzotriazole, so the above-described layer of Cu (C ₆ H ₄ N ₃ ) ₂ is also caused. It is considered that the surface of the wiring circuit is roughened.

  The multilayer printed wiring board of the present invention is obtained by the above-described method for producing a multilayer printed wiring board. In the multilayer printed wiring board of the present invention, the adhesion between the wiring circuit and the cured prepreg is sufficiently improved, so that the wiring circuit can function more stably.

  ADVANTAGE OF THE INVENTION According to this invention, the adhesiveness of a wiring circuit and the hardening body of a prepreg can fully be improved.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same reference numerals are used for the same or equivalent elements, and duplicate descriptions are omitted.

  FIG. 1 is a cross-sectional view schematically showing an example of a multilayer printed wiring board according to the embodiment. A multilayer printed wiring board 1 shown in FIG. 1 includes an inner layer circuit board 6, a prepreg cured body 8 provided on both surfaces of the inner layer circuit board 6, and a metal foil 9 provided on the prepreg cured body 8. Is provided. The inner layer circuit board 6 and the prepreg cured body 8 are sandwiched between a pair of metal foils 9. The inner layer circuit board 6 includes a substrate 2 and a wiring circuit 4 provided on both surfaces of the substrate 2 and patterned. Therefore, the multilayer printed wiring board 1 has a laminated structure in which a prepreg containing a resin and a fiber is laminated on the wiring circuit 4 of the inner layer circuit board 6 and the inner layer circuit board 6 and the cured body 8 of the prepreg are integrated. Prepare.

  Examples of the substrate 2 include a glass epoxy substrate, a metal substrate, a polyester substrate, a BT resin substrate, and a thermosetting PPE substrate. The wiring circuit 4 is preferably made of copper as a constituent material. The prepreg cured body 8 is suitably obtained by curing a commonly used prepreg. The constituent material of the metal foil 9 is preferably copper.

  Here, an example of a method for manufacturing a multilayer printed wiring board according to the embodiment will be described in detail with reference to FIGS. 1 and 2. FIG. 2 is a flowchart illustrating an example of a method for manufacturing a multilayer printed wiring board according to the embodiment. Hereinafter, the manufacturing method of the above-mentioned multilayer printed wiring board 1 will be described in detail as an example of the manufacturing method of the multilayer printed wiring board according to the embodiment.

(Inner layer circuit board preparation process)
First, the inner layer circuit board 6 is prepared. The inner layer circuit board 6 is manufactured as follows, for example. First, a laminate having a substrate 2 and a metal foil provided on both surfaces of the substrate 2 is prepared. Next, the wiring circuit 4 is formed from the said metal foil by patterning the said metal foil using the photolithographic method.

(Roughening process)
Next, a chemical roughening solution is brought into contact with the surface 4a of the wiring circuit 4 to roughen the surface 4a (roughening step S1). Thereby, the influence of the grade of the metal foil for forming the wiring circuit 4 can be made small. Such roughening treatment may be performed twice or more as necessary. Hereinafter, the constituent materials of the chemical roughening solution will be described in detail.

  The chemical roughening solution preferably contains an azole compound. As such an azole compound, 1,2,3-benzotriazole is particularly preferable. Thereby, since the surface 4a of the wiring circuit 4 can be roughened more reliably, solder heat resistance (solder resistance at high temperature) can be improved in the multilayer printed wiring board 1 obtained. In order to suitably obtain such an effect, the concentration of 1,2,3-benzotriazole is preferably 0.5 to 20 g / L, more preferably 0.5 to 10 g / L, and 0.5 Particularly preferred is ˜7 g / L. L represents liters.

  The chemical roughening solution preferably further contains an oxidation accelerator. Examples of the oxidation accelerator include sulfuric acid, hydrogen peroxide, hypochlorous acid, nitric acid, phosphoric acid and the like. In particular, the chemical roughening solution preferably contains sulfuric acid and hydrogen peroxide.

  The chemical roughening solution preferably contains a further azole compound in addition to 1,2,3-benzotriazole. The azole compound is believed to work as a corrosion inhibitor. Examples of the azole compound include 5-aminotetrazole, benzotriazole, tolyltriazole, 1-methyltetrazole, 2-methyltetrazole, 5-methyltriazole, 1-phenyltetrazole, imidazole, 5-phenyltetrazole, thiazole, pyrazole, Examples include oxazole, 1,2,3-triazole, indazole, 1,2,4-triazole and the like. Among these, 5-aminotetrazole is particularly preferable.

As a suitable combination of the constituent materials of the chemical roughening solution, for example, the following combinations (1) to (6) may be mentioned.
(1) Persulfates and corrosion inhibitors (2) Persulfates, acids and corrosion inhibitors (3) Sulfuric acid, hydrogen peroxide and corrosion inhibitors (4) Ferric chloride and corrosion inhibitors (5) Chlorination Dicopper and corrosion inhibitor (6) Tetraamine copper chloride and corrosion inhibitor

  Among these, the combination (3) is particularly preferable. Specifically, a combination of sulfuric acid, hydrogen peroxide and an azole compound is preferable. As such an azole compound, 5-aminotetrazole and 1,2,3-benzotriazole are particularly preferable.

  The concentration of sulfuric acid is preferably 20 to 400 g / L, more preferably 20 to 200 g / L, and particularly preferably 50 to 100 g / L. If the concentration of sulfuric acid is less than 20 g / L, the solubility of metals such as copper tends to decrease, resulting in a decrease in the life of the liquid. If it exceeds 400 g / L, the liquid becomes industrially expensive and running. Cost tends to increase.

  The concentration of hydrogen peroxide is preferably 10 to 200 g / L, more preferably 10 to 100 g / L, and particularly preferably 10 to 50 g / L. If the concentration of hydrogen peroxide is less than 10 g / L, the speed of the roughening process decreases, the processing time becomes longer, and the apparatus tends to be longer in the case of a horizontal conveyance processing line. However, the natural decomposition of hydrogen peroxide increases, so that the amount used increases and the running cost tends to increase.

  The concentration of the azole compound is preferably 0.5 to 40 g / L, more preferably 0.5 to 30 g / L, and particularly preferably 0.5 to 20 g / L. When the concentration of the azole compound is less than 0.5 g / L, the solder heat resistance tends to decrease, and when it exceeds 40 g / L, the processing unevenness in the roughening treatment tends to increase.

  In addition to the above constituent materials, the chemical roughening solution may further contain an alcohol solvent. Thereby, generation | occurrence | production of black deposit is suppressed. As a result, the foreign matter defect of the multilayer printed wiring board due to redeposition of the black precipitate can be eradicated. Furthermore, the life of the chemical roughening solution can be extended by about 4 times without impairing the adhesive properties. The alcohol solvent is not particularly limited, but a glycol solvent is preferable, and examples thereof include alkylene glycol, alkylene glycol alkyl ether, glycolic acid, and polyethylene glycol having a molecular weight of 200 to 20000.

  Examples of the alkylene glycol include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and methylpropylene glycol. Examples of the alkylene glycol alkyl ether include diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol dimonoethyl ether, and diethylene glycol monobutyl ether. These solvents may be used alone or in combination of two or more.

  Examples of the method for bringing the chemical roughening solution into contact with the surface 4a of the wiring circuit 4 include a spray method and a dip method. The treatment temperature and treatment time are preferably determined as appropriate so that the roughening amount (etching amount) on the surface 4a is 0.5 μm or more. When the roughening amount on the surface 4a is less than 0.5 μm, sufficient adhesive force tends not to be obtained.

  The roughening amount can be measured by a weight method using the electronic balance according to the following formula (1).

Roughening amount = [weight before roughening treatment (g) −weight after roughening treatment (g)] / [roughening area (cm ² ) × specific gravity of metal to be roughened (g / cm ³ )] (1 )

(Oxidation process)
After the roughening step, the surface 4a of the wiring circuit 4 is oxidized (oxidation step S2). Specifically, for example, the surface 4a of the wiring circuit 4 is brought into contact with an oxidation treatment liquid containing water and an oxidizing agent. Examples of the oxidizing agent include alkaline aqueous solutions such as sodium chlorite, alkali persulfate, potassium chlorate, potassium perchlorate, and alkali peroxosulfate. As a method of bringing the oxidation treatment liquid into contact with the surface 4a of the wiring circuit 4, for example, a method of immersing the surface 4a of the wiring circuit 4 in the oxidation treatment liquid, a method of spraying the oxidation treatment liquid onto the surface 4a of the wiring circuit 4, and the like. Can be mentioned.

  For example, when the wiring circuit 4 is made of copper, copper oxide is formed on the surface 4 a of the wiring circuit 4. Such oxidation treatment is also called blackening treatment.

The composition of the oxidation treatment liquid and the treatment conditions are, for example, as follows.
NaClO ₂ : 30 to 150 g / L
Na ₃ PO ₄ · 12H ₂ O: 10 to 60 g / L
NaOH: 5-30 g / L
Water: Amount in which the entire oxidation treatment liquid becomes 1 L Treatment temperature (liquid temperature): 55 to 95 ° C.
Processing time: 60-600 seconds

(Reduction process)
After the oxidation step, the surface 4a of the wiring circuit 4 is reduced (reduction step S3). Specifically, for example, the surface 4a of the wiring circuit 4 is brought into contact with a reduction treatment liquid containing water and a reducing agent. Examples of such a reducing agent include sodium borohydride, formalin and the like. Examples of the method of bringing the reduction treatment liquid into contact with the surface 4a of the wiring circuit 4 include a method of immersing the surface 4a of the wiring circuit 4 in the reduction treatment solution, and a method of spraying the reduction treatment solution onto the surface 4a of the wiring circuit 4. Can be mentioned.

The composition of the reduction treatment liquid and the treatment conditions are, for example, as follows.
Sodium borohydride: 0.1-10 g / L
Water: Amount in which the entire reduction treatment solution becomes 1 L pH: 7.0 to 13.0
Process temperature (liquid temperature): 20-60 degreeC
Processing time: 30-300 seconds

  Subsequently, after washing with water as necessary, the treatment liquid is brought into contact with the surface 4 a of the wiring circuit 4.

The composition of the treatment liquid and the treatment conditions are, for example, as follows.
36 mass% formalin: 2 to 20 mL / L
NaOH: 0.05 to 0.03 mol / L
Water: Amount in which the entire treatment liquid becomes 1 L pH: 11.0-13.0
Process temperature (liquid temperature): 50-70 degreeC
Processing time: Time until the potential of the surface 4a of the wiring circuit 4 becomes -1400 to -1100 mV with respect to the Ag-AgCl electrode

(Silane treatment process)
After the reduction step, if necessary, the surface 4a of the wiring circuit 4 may be subjected to silane treatment using a silane coupling agent. Thereby, the adhesiveness between the wiring circuit 4 and the cured prepreg body 8 can be further increased. The reason is not necessarily clear, but a silanol group (Si—OH) generated by hydrolysis of the silane coupling agent is bonded to a copper atom present on the surface 4 a of the wiring circuit 4, thereby forming a metallosiloxane bond (Si—O). -Cu) is presumed to be formed.

(Lamination process)
After the reduction step, the prepreg is bonded to the inner circuit board 6, and the whole is heated and pressurized while adjusting the conditions. Examples of the molding method include a method using a multistage press, a multistage vacuum press, a continuous molding machine or an autoclave molding machine. Heating and pressurization can be performed under conditions of a temperature of 100 to 250 ° C., a pressure of ^{2 to} 100 kg / cm ² and a treatment time of 0.1 to 5 hours. Here, the prepreg is suitably cured by heating at a temperature of 120 ° C. or higher for 15 to 30 minutes, preferably at a temperature of 170 to 220 ° C. for 60 to 150 minutes. In this way, the prepreg cured body 8 is formed on the inner layer circuit board 6.

  Next, the multilayer printed wiring board 1 can be produced by bringing the metal foil 9 into close contact with the prepreg cured body 8 and heating and / or pressurizing the whole. As the metal foil 9, a single-side roughened metal foil or a double-sided roughened metal foil can be used. It is preferable that the metal foil 9 is in close contact with the hardened body 8 side of the prepreg as a roughened surface.

  As described above, in the method for manufacturing a multilayer printed wiring board according to the present embodiment, the roughening process, the oxidation process, and the reduction process are sequentially performed, so that the adhesiveness between the wiring circuit 4 and the cured prepreg 8 is sufficient. Can be improved. Therefore, the peel strength, solder heat resistance, and hydrochloric acid resistance (haloing resistance) between the inner circuit board 6 and the prepreg cured body 8 are improved. In particular, the peel strength between the inner layer circuit board 6 and the cured prepreg body 8 is significantly improved. Therefore, in the obtained multilayer printed wiring board 1, the wiring circuit 4 can function more stably.

  For example, when the wiring circuit 4 uses copper as a constituent material, the adhesiveness between the wiring circuit 4 and the cured prepreg body 8 can be improved more reliably. Further, for example, when the chemical roughening solution contains sulfuric acid, hydrogen peroxide, 1,2,3-benzotriazole and 5-aminotetrazole, the adhesion between the wiring circuit 4 and the cured prepreg 8 is further improved. It can be definitely improved.

  The bonding method of the inner circuit board 6, the prepreg cured body 8 and the metal foil 9 is not limited to the above method. For example, after the metal foil 9 is previously bonded to the prepreg, the prepreg to which the metal foil 9 is bonded may be bonded to the inner layer circuit board 6, or the inner layer circuit board 6, the prepreg and the metal foil 9 may be formed by press molding or the like. You may adhere together. Further, instead of the metal foil 9, a single-sided plate in which a resin plate and a metal foil are bonded together can be used, and the resin plate side can be adhered to the prepreg.

  Moreover, in the multilayer printed wiring board 1, you may pattern the metal foil 9 as needed. In this case, a wiring circuit is formed from the metal foil 9. Further, the surface of the wiring circuit (or the surface of the metal foil 9 when no wiring circuit is formed) can be roughened, oxidized and reduced as necessary, and the prepreg and the metal foil can be laminated by the above-described method. By repeating such operations and alternately laminating prepregs and metal foils (wiring circuits), a multilayer printed wiring board having a further multilayered structure can be produced.

  Further, after the prepreg is cured, via holes (through holes) may be formed in the laminated substrate having the inner circuit board, the cured prepreg, and the metal foil. In order to form a via hole, it is necessary to make a hole in the multilayer substrate. When the metal foil in the laminated substrate is thin, it can be directly drilled by a drill or a laser. When the metal foil in the laminated substrate is thick, the hole can be drilled with a drill or a laser after the window hole is formed by the conformal mask method or the large window method. When the prepreg is cured and the outer layer is a metal foil, the surface of the metal foil may be roughened before drilling or after drilling. If resin residue remains on the surface of metal foil or through holes after drilling, remove the resin residue and use electroless copper plating, metal deposition, sputtering, ion plating, etc. Via holes can be formed.

  As mentioned above, although preferred embodiment of this invention was described in detail, this invention is not limited to the said embodiment.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
Copper-clad laminate (trade name: E-67, manufactured by Hitachi Chemical Co., Ltd.) in which rolled copper foil (trade name: BHN-35, manufactured by Nikko Materials Co., Ltd., foil thickness 35 μm) is formed on both surfaces of the epoxy resin substrate. The inner layer circuit board on which the copper circuit was formed was produced by patterning in advance a rolled copper foil having a thickness of 0.4 mm on both sides. The obtained inner layer circuit board was processed by the following method.

  First, after immersing the inner layer circuit board in a degreasing solution (NaOH aqueous solution, 50 g / L) for 4 minutes and thoroughly washing with water, a 75 mass% sulfuric acid aqueous solution 80 mL / L, a 35 mass% hydrogen peroxide solution 60 mL / L, 5 -It immersed for 1 minute at 30 degreeC in the liquid mixture (chemical roughening liquid) which consists of aminotetrazole 2g / L and 1,2,3-benzotriazole 3g / L (roughening process). The roughening amount was 2.5 μm.

  Subsequently, after washing with water, the blackening treatment liquid (oxidation treatment liquid) was brought into contact with the surface of the copper circuit of the inner layer circuit board to perform the blackening treatment. Thereby, copper oxide was formed on the surface of the copper circuit (oxidation step).

The composition and treatment conditions of the blackening treatment liquid are as follows.
NaClO ₂ : 90 g / L
Na ₃ PO ₄ · 12H ₂ O: 30 g / L
NaOH: 15 g / L
Water: Amount of the blackening treatment liquid to be 1 L Treatment temperature (liquid temperature): 85 ° C.
Processing time: 180 seconds

  Subsequently, after washing with water, a reduction treatment was performed by bringing the reduction treatment liquid into contact with the surface of the copper circuit of the inner layer circuit board. Thereby, the copper oxide formed on the surface of the copper circuit was reduced (reduction process).

The composition of the reduction treatment liquid and the treatment conditions are as follows.
Sodium borohydride: 1g / L
Water: Amount in which the entire reduction treatment solution becomes 1 L pH: 12.5
Processing temperature (liquid temperature): 40 ° C
Processing time: 40 seconds

  Subsequently, after washing with water, the treatment liquid was brought into contact with the surface of the copper circuit of the inner layer circuit board.

The composition of the treatment liquid and the treatment conditions are as follows.
36% by mass formalin: 4 mL / L
NaOH: 0.1 mol / L
Water: Amount of 1L of the entire treatment solution pH: 12.5
Processing temperature (liquid temperature): 60 ° C
Processing time: Time until the surface potential of the copper circuit becomes −1200 mV with respect to the Ag—AgCl electrode

Thereafter, it was washed again with water and dried at 80 ° C. for 40 minutes to obtain an inner layer circuit board. A prepreg made of glass cloth-epoxy resin (trade name: E-67, manufactured by Hitachi Chemical Co., Ltd.) is laminated on both surfaces of the inner layer circuit board, and rolled copper foil (trade name: BHN-18, Nikko) as an outer layer on the prepreg. The materials company make, foil thickness 18micrometer) were bonded together. And these were press-molded at 4.9 × 10 ⁶ Pa (50 kgf / cm ² ) and 170 ° C. for 90 minutes to produce a multilayer printed wiring board (four-layer printed wiring board) of Example 1. .

(Example 2)
The multilayer print of Example 2 was made in the same manner as in Example 1 except that electrolytic copper foil (trade name: NDGR-35, manufactured by Nippon Electrolytic Co., Ltd.) was used instead of the rolled copper foil when producing the inner layer circuit board. A wiring board (4-layer printed wiring board) was produced.

(Comparative Example 1)
A multilayer printed wiring board (four-layer printed wiring board) of Comparative Example 1 was produced in the same manner as in Example 1 except that the oxidation process and the reduction process were not performed.

(Comparative Example 2)
A multilayer printed wiring board (four-layer printed wiring board) of Comparative Example 2 was produced in the same manner as in Example 1 except that the roughening step and the reduction step were not performed.

(Comparative Example 3)
A multilayer printed wiring board (4-layer printed wiring board) of Comparative Example 3 was produced in the same manner as in Example 1 except that the roughening step was not performed.

(Comparative Example 4)
A multilayer printed wiring board (four-layer printed wiring board) of Comparative Example 4 was produced in the same manner as in Example 1 except that the reduction step was not performed.

(Evaluation results)
For the multilayer printed wiring boards of Examples 1 and 2 and Comparative Examples 1 to 4 produced above, peel strength between the inner circuit board and the cured prepreg, solder heat resistance, and hydrochloric acid resistance (haloing resistance) ) Was evaluated. The evaluation results are shown in Table 1.

  The peel strength was measured according to JIS C6481. The peel strength test was performed using an autograph (manufactured by Shimadzu Corporation, model: AGS-100B) at a pulling speed of 50 mm / min.

  In the solder heat resistance test, first, a multilayer printed wiring board was cut in the laminating direction to produce a 100 mm square test piece. Next, after drying a test piece at 230 degreeC for 2 hours, the pressure cooker test (121 degreeC, 2 atmospheres) was implemented for 2 hours. Thereafter, the test piece was immersed in a solder bath at 260 ° C. for 20 seconds. About the test piece taken out from the solder bath, the surface layer surface was observed using the stereomicroscope. As a result, “blowing” was confirmed when blistering was confirmed due to the peeling phenomenon at the interface between the inner layer circuit board and the cured prepreg, and “abnormality” was confirmed when blistering was not confirmed. .

  In the hydrochloric acid resistance test, first, a multilayer printed wiring board was drilled with a diameter of 0.3 mm, and then the outer layer copper foil was removed and cut in the stacking direction to prepare a 130 mm × 30 mm square test piece. Then, the test piece was immersed in 18 mass% hydrochloric acid, and the time until hydrochloric acid permeates between the inner layer circuit board and the cured prepreg was measured. In Table 1, ◯ indicates that there is no soaking, and x indicates that there is soaking.

It is sectional drawing which shows typically an example of the multilayer printed wiring board which concerns on embodiment. It is a flowchart which shows an example of the manufacturing method of the multilayer printed wiring board which concerns on embodiment. It is sectional drawing which shows typically an example of the common multilayer printed wiring board seen conventionally.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Multilayer printed wiring board, 2 ... Board | substrate, 4 ... Wiring circuit, 4a ... The surface of a wiring circuit, 6 ... Inner layer circuit board, 8 ... Hardened | cured body of prepreg, 9 ... Metal foil.

Claims (5)

A prepreg containing a resin and a fiber is laminated on the wiring circuit of an inner layer circuit board having a substrate and a wiring circuit provided on the substrate, and the inner layer circuit board and the cured body of the prepreg are integrated. A method for producing a multilayer printed wiring board having a laminated structure comprising:
A roughening step of roughening the surface by bringing a chemical roughening solution into contact with the surface of the wiring circuit;
An oxidation step of oxidizing the surface of the wiring circuit after the roughening step;
A reduction step of reducing the surface of the wiring circuit after the oxidation step;
A method for producing a multilayer printed wiring board, comprising:   The method for manufacturing a multilayer printed wiring board according to claim 1, wherein the wiring circuit is made of copper.   The manufacturing method of the multilayer printed wiring board of Claim 1 or 2 with which the said chemical roughening liquid contains 1,2,3- benzotriazole.   The manufacturing method of the multilayer printed wiring board of Claim 3 with which the said chemical roughening liquid further contains a sulfuric acid, hydrogen peroxide, and 5-aminotetrazole.   The multilayer printed wiring board obtained by the manufacturing method of the multilayer printed wiring board as described in any one of Claims 1-4.

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