JP2005132859A - Nonhalogen flame-retardant adhesive resin mixture, metal-clad laminate for flexible printed circuit, cover lay film and flexible printed circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonhalogen flame-retardant adhesive resin mixture useful for use as an adhesive in an FPC (flexible printed circuit) in relation to the nonhalogen flame-retardant adhesive resin mixture having excellent flame retardance, adhesion and migration resistance. <P>SOLUTION: The nonhalogen flame-retardant adhesive resin mixture is composed of 90-50 vol.% of a base resin composed of at least an epoxy resin, a curing agent and a rubber component and 10-50 vol.% of a nitrogen-containing compound. Thereby, the excellent flame retardance, adhesion and migration resistance are obtained by compounding the nitrogen-containing compound which is a nonhalogen flame retardant. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a non-halogen, flame-retardant adhesive resin mixture excellent in flame retardancy, adhesion and migration resistance, a metal-clad laminate for a flexible printed wiring board using the same, a coverlay film, and a flexible printed wiring board It is about.

  In recent years, non-halogenation has been promoted in the field of printed wiring boards from the viewpoint of environment. Taking printed wiring boards, especially those related to flexible printed wiring boards (FPC) as an example, not only the metal-clad laminate side that will be the base film, but also the adhesive on the coverlay film side that will be the cover Therefore, non-halogenation is required.

  A metal-clad laminate for FPC is usually made by attaching a metal foil, that is, a copper foil, to one side (both sides are acceptable) of a base film such as a polyimide film with an adhesive. A circuit pattern is formed by chemical treatment to obtain the target FPC. On this FPC, a cover lay film is covered with an adhesive as a protective layer if necessary.

  Such an FPC is, for example, incorporated at a high density in a narrow movable part of an electronic device such as a small hard desk, or curved as being highly flexible in a narrow part of an electronic device such as a mobile phone or a PDA. It is incorporated and used extensively.

For this reason, in FPC, in order to exhibit stable performance over a long period of time without peeling between layers, the composition of the adhesive used, that is, the adhesive layer is extremely important. One of these compositions has been proposed, and as one of them, one having an epoxy resin as a main component is widely used (Patent Document 1, Patent Document 2).
JP-A-10-112576 JP 2003-27028 A

  In actual use, an appropriate amount of a curing agent, a curing accelerator, a rubber component for improving characteristics, a flame retardant, and the like are appropriately blended with the epoxy resin. Of course, even in each of these compounding components, non-halogenated ones are used, and in particular, phosphorus-based (phosphate esters and phosphorus compounds) materials are often used as non-halogen flame retardants.

However, in the case of the FPC obtained in this way, according to the study by the present inventors, it has been found that a migration phenomenon of metal, particularly copper, is likely to occur in the FPC.
Here, the migration phenomenon is that copper elutes and precipitates between adjacent circuit patterns (copper conductors adjacent to each other at a narrow interval), that is, copper dendrite is generated. Is a phenomenon that leads to a short circuit. Although the details of this phenomenon are unknown, various ionic impurities contained in the constituent material are eluted by stress under high temperature and high humidity, or ions are generated due to partial decomposition of the constituent material. Due to these, it is considered that copper is eluted and deposited.

Actually, depending on the material components used, there is a possibility that ionic impurities are contained, and there is a possibility that unnecessary ions are generated due to decomposition during the manufacturing process. For example, it may be contained in the epoxy resin itself, and may be contained in a rubber component for compounding. In particular, NBR as a rubber component has been reported to contain ionic impurities (Patent Document 3).
JP 2002-80812 A

  From this point of view, the present inventors have focused on phosphorus-based materials that are non-halogen flame retardants, and the phosphorus-based materials themselves are decomposed at high temperatures and high humidity to provide a source of unnecessary impurities and ions. When a nitrogen-containing compound is used as a non-halogen flame retardant, good results can be obtained not only in flame retardancy and adhesiveness, but also in migration resistance. I found out.

  In the future, electronic devices will be further miniaturized, and even smaller FPCs will naturally need to be further miniaturized, and the distance between adjacent circuit patterns will become increasingly narrower, making migration more likely to occur. Such improvement and improvement of migration resistance is becoming increasingly important.

  The present invention has been made through this process, and is basically a non-halogen flame retardant adhesive resin blend in which a predetermined amount of a nitrogen-containing compound is blended with a base resin composed of an epoxy resin, a curing agent, and a rubber component. Thus, the present invention provides a metal-clad laminate for a flexible printed wiring board, a coverlay film, and a flexible printed wiring board using the same.

  The present invention according to claim 1 is a non-halogen flame retardant adhesive resin mixture characterized by comprising 90-50 vol% of a base resin comprising at least an epoxy resin, a curing agent, and a rubber component and 10-50 vol% of a nitrogen-containing compound. is there.

  The present invention according to claim 2 is the non-halogen flame retardant adhesive resin blend according to claim 1, wherein the rubber component is an acrylic rubber.

  The present invention described in claim 3 is the non-halogen flame retardant adhesive resin blend according to claim 1 or 2, wherein the acrylic rubber contains a carboxyl group.

  The present invention according to claim 4 is the non-halogen flame retardant adhesive resin blend according to claim 1, 2, or 3, wherein the nitrogen-containing compound has a particle size of 10 µm or less.

  The present invention according to claim 5 is the non-halogen flame retardant adhesive resin blend according to claim 1, 2, 3 or 4, wherein the nitrogen-containing compound is melamine cyanurate.

  According to a sixth aspect of the present invention, there is provided a metal-clad laminate for a flexible printed wiring board, wherein the non-halogen flame retardant adhesive resin blend according to any one of the first to fifth aspects is used for an adhesive layer. is there.

  A seventh aspect of the present invention is a cover lay film characterized in that the non-halogen flame retardant adhesive resin mixture according to any one of the first to fifth aspects is used for an adhesive layer.

  The present invention according to claim 8 is a flexible printed wiring board characterized in that the non-halogen flame retardant adhesive resin mixture according to any one of claims 1 to 5 is used for an adhesive layer.

  First, according to the non-halogen flame retardant adhesive resin admixture of the present invention, 10-50 vol% of a nitrogen-containing compound is blended with 90-50 vol% of a base resin consisting of at least an epoxy resin, a curing agent, and a rubber component. In addition to excellent flame retardancy and adhesion, excellent migration resistance is obtained.

  Moreover, if the non-halogen flame retardant adhesive resin blend of the present invention is used as an adhesive, an excellent printed wiring board, in particular, a metal-clad laminate for a flexible printed wiring board, a coverlay film, and a flexible printed wiring board (FPC) can be obtained. Can do.

  The epoxy resin of the base resin used in the present invention is not particularly limited, but is bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac resin, bisphenol A novolac type epoxy. Resins, polyfunctional glycidyl amine resins, polyfunctional phenol diglycidyl etherified products, alicyclic epoxy resins, biphenyl type epoxy resins, naphthalene ring-containing epoxy resins and the like can be used alone or in combination. Among these, the use of a bisphenol type epoxy resin is preferable.

  The curing agent and curing accelerator blended in the epoxy resin are not particularly limited as long as they are usually used. Specific curing agents include, for example, acid anhydride curing agents (phthalic anhydride, maleic anhydride, etc.), phenol resins as curing components, imidazole curing agents, aromatic amine curing agents (4,4 ′ -Diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, etc.), aliphatic amine curing agents, alicyclic amine curing agents and the like. Specific curing accelerators include tertiary amines, borofluorides, octylates and the like. Of course, these addition amounts are usually added in accordance with the type of epoxy resin used.

  As the rubber component blended in the epoxy resin, acrylic rubber such as butadiene acrylonitrile rubber, ethylene acrylic copolymer and ethylene acrylonitrile copolymer are preferable, and those containing a carboxyl group are more preferable. When this rubber component is blended, rubber particles are appropriately dispersed in the epoxy resin during the production of FPC and the like, so that the impact strength of the epoxy resin can be enhanced by the cushion function. Also, moderate flexibility can be obtained. However, since rubber components may contain ionic impurities and the like, it is desirable to use one having as high purity as possible.

  In the present invention, these epoxy resins, curing agents, curing accelerators, rubber components, and the like constitute a base resin, and 10% of the nitrogen-containing compound that is a non-halogen flame retardant is contained with respect to 90-50 vol% of the base resin. -50 vol% is blended.

  As this nitrogen-containing compound, for example, melamine cyanurate, melamine borate and the like are desirably used. This nitrogen-containing compound is used in place of the phosphorus-based material, which is a non-halogen flame retardant, because it is stable even at high temperatures and high humidity during the manufacturing process of FPC, etc., and there is little supply of unnecessary impurities and ions It is possible. And it is based on the following reason that the compounding quantity was 10-50 vol% with respect to 90-50 vol% of base resin. First, if the blending amount is less than 10 vol%, the desired flame retardancy of the target non-halogen flame retardant adhesive resin mixture cannot be obtained. Moreover, it is because adhesiveness will fall as an adhesive agent, when a compounding quantity exceeds 50 vol%.

  Further, the particle size (average particle size) of the nitrogen-containing compound is desirably 10 μm or less, preferably 5 μm or less. The reason for this is that if the particle size is 10 μm or less as a flame retardant, the surface properties are excellent when applied thinly, and the condition is good. On the other hand, if the particle size exceeds 10 μm, the film thickness is applied thinly. This is because the surface properties are lowered and the condition is poor.

  In the base resin of the present invention, if necessary, other materials can be appropriately blended within the range where the characteristics do not change. For example, a leveling agent, a viscosity modifier, etc. can be mix | blended with the corrosion inhibitor benzotriazole (BTA), ethylenediaminetetraacetic acid (EDTA), 2-aminoethanol, and others. When BTA is blended, as is clear from the examples described later, corrosion of the copper foil portion is suppressed, and migration resistance is further improved.

  1 to 3 show a metal-clad laminate for a flexible printed wiring board, a cover lay film, and a flexible printed wiring board of the present invention using the non-halogen flame retardant adhesive resin mixture.

  A metal-clad laminate 10A for a flexible printed wiring board in FIG. 1 is before FPC manufacture, and is mixed with the non-halogen flame-retardant adhesive resin of the present invention on one side (both sides are acceptable) of a base film 11 such as a polyimide film. A metal foil, that is, a copper foil 13 is pasted with an adhesive 12 made of a material. The FPC 10B in FIG. 2 is obtained by applying a predetermined chemical treatment to the laminated plate 10A to form a circuit pattern on the copper foil 13 portion. In addition, the layer of the adhesive 12 consisting of the non-halogen flame retardant adhesive resin blend of the present invention is applied to one side (lower surface) of the base film 14 such as a polyimide film as a protective layer on the upper surface side of the FPC 10B. The coverlay film 10C is covered. Moreover, both base films 11 and 14 are not limited to a polyimide film, The other film normally used can also be used.

  In any case, in these articles, delamination does not easily occur because the adhesive 12 made of the non-halogen flame-retardant adhesive resin blend of the present invention having excellent flame retardancy, adhesion and migration resistance is used. In addition, short circuit due to the migration phenomenon hardly occurs, and characteristically stable reliability can be obtained. Of course, no toxic gas or toxic substance is generated at the time of combustion destruction or disposal by the non-halogen flame retardant.

  As shown in Tables 1 to 6, the blends of non-halogen flame retardant adhesive resin blends that satisfy the requirements of the present invention (Examples 1 to 20) and the similar blends that lack the requirements of the present invention (comparison) A sample adhesive was prepared using Examples 1 to 9), and this was coated on a polyimide film having a thickness of 25 μm with a thickness of 30 μm when dried to prepare a test sample sheet. Each sample sheet was subjected to the following tests and inspections for property evaluation. In other words, flame resistance test, adhesive strength test for adhesive evaluation, insulation resistance test for evaluating migration resistance, whether dendrites are generated, and surface condition by coating film surface test It was. In addition, the numerical value of the compounding quantity of each material in each Table 1-6 represents vol%.

  In each table, the composition of the base resin A is as follows: bisphenol A type epoxy resin 37.1 wt%, acid anhydride curing agent 34.8 wt%, carboxyl group-containing NBR 27.0 wt% of rubber component, tertiary accelerator of curing accelerator 04.0 wt%. The composition of the base resin B is 14.1 wt% of novolak type epoxy resin, 43.6 wt% of bisphenol A type epoxy resin, 23.4 wt% of phenolic resin as a curing component, 18.7 wt% of NBR containing a carboxyl group as a rubber component, It is 0.2 wt% of imidazole. The composition of the base resin C is 64.5 wt% of bisphenol A type epoxy resin, 22.5 wt% of aromatic amine curing agent (4,4′-diaminodiphenyl sulfone), and 13.0 wt% of NBR containing a carboxyl group of the rubber component. .

  The nitrogen-containing compound was melamine cyanurate without surface treatment, and the average particle size was 5 μm, 10 μm, or 20 μm. The additive of Examples 15-20 is the corrosion inhibitor benzotriazole (BTA). The phosphorus compound that is the flame retardant of Comparative Example 9 is trixylenyl phosphate.

<Flame retardance test>
About the said sample sheet | seat, a UL94VTM test is performed, the thing which passed VTM-0 is displayed by (circle), and the rejected thing is displayed by x.

<Adhesive strength test>
The adhesive surface side of the sample sheet was bonded to a copper foil having a thickness of 35 μm, and a bonded sample was formed by pressing at 170 ° C. and 40 kg / cm ² for 40 minutes, and 180 ° peel strength was measured. The measured numerical value is expressed in N / cm, and if the FPC value is usually about 7 N / cm, it is almost acceptable.

<Insulation resistance test>
First, the adhesive of the above sample was applied to a 25 μm polyimide film so as to have a thickness of 10 μm when dried, and an 18 μm rolled copper foil was bonded to the adhesive surface side, followed by heat curing at about 160 ° C. for 5 hours. A single-sided metal-clad laminate was made. Comb-shaped circuit patterns opposed to each other were formed on the copper foil of the laminate. The interval between adjacent comb-shaped tooth portions was set to 100 μm with land portion L / sea portion S = 100 μm / 100 μm.

Next, a 25 μm polyimide film coated with the above sample adhesive on the circuit pattern so as to have a thickness of 30 μm when dried was pressed at 170 ° C. and 40 kg / cm ² for 40 minutes to prepare a sample FPC. . Each sample FPC was placed in an atmosphere of 85 ° C. and 85% RH (humidity), applied to an opposing comb-shaped circuit pattern at DC 50 V, and held for 240 hours. Thereafter, the insulation resistance was measured. The measured numerical values are expressed in Ω units, and 10 ⁿ is indicated by E + n in the table. An FPC value of 10 ⁷ Ω or more is a sufficient value. Further, the presence or absence of dendrite generation in the sample FPC was examined with a microscope.

  A case where the circuit is short-circuited due to the generation of dendrite is indicated by x, and a case where dendrite is not short-circuited but is growing at 30% or more between the circuits is indicated by Δ, and the growth of the dendrite is 30. The case of less than% is indicated by ○.

<Coating surface property test>
The adhesive of the above sample was applied to a polyimide film so as to have a thickness of 15 μm when dried, and the surface property was visually confirmed. When the surface has good surface properties without wrinkling like streaks during and after application, the surface is marked with ◯, and the surface is wrinkled when applied, but no wrinkle is seen after drying Is indicated by Δ, and when the surface is wrinkled both during and after application, it is indicated by ×.

  First, it can be seen from Tables 1 to 6 that in Examples 1 to 14 of the present invention, good results are obtained in any physical properties. Moreover, in Examples 15-20, when BTA which is a corrosion inhibitor is mix | blended as an additive, it turns out that insulation resistance improves and generation | occurrence | production of a dendrite is also suppressed. On the other hand, in Comparative Examples 1 to 3, it can be seen that the nitrogen-containing compound is less than 10 vol% and the flame retardancy is insufficient. In Comparative Examples 4-6, since nitrogen-containing compound is too much exceeding 50 vol%, it turns out that adhesiveness falls. In Comparative Examples 7-8, since the particle size of a nitrogen-containing compound is too large, it turns out that coating-film surface property is bad. In Comparative Example 9, it can be seen that since the flame retardant is a phosphorus compound, the insulation resistance is low and a short circuit occurs due to the generation of dendrite.

It is a longitudinal cross-sectional view which becomes one embodiment of the metal-clad laminated board for flexible printed wiring boards which concerns on this invention. It is a longitudinal section used as one embodiment of the flexible printed wiring board concerning the present invention. It is a longitudinal section used as one embodiment of the coverlay film concerning the present invention.

Explanation of symbols

10A: Metal-clad laminate for flexible printed wiring board 10B: Flexible printed wiring board 10C: Coverlay film 11: Base film 12 ... Adhesive of non-halogen flame retardant adhesive resin blend 13. ..Copper foil 14 ... Base film

Claims (8)

A non-halogen flame retardant adhesive resin mixture comprising at least 90-50 vol% of a base resin comprising an epoxy resin, a curing agent, and a rubber component and 10-50 vol% of a nitrogen-containing compound. The non-halogen flame retardant adhesive resin blend according to claim 1, wherein the rubber component is an acrylic rubber. 3. The non-halogen flame retardant adhesive resin blend according to claim 1, wherein the acrylic rubber contains a carboxyl group. The non-halogen flame-retardant adhesive resin blend according to claim 1, 2, or 3, wherein the nitrogen-containing compound has a particle size of 10 µm or less. The non-halogen flame retardant adhesive resin blend according to claim 1, wherein the nitrogen-containing compound is melamine cyanurate. A metal-clad laminate for a flexible printed wiring board, wherein the non-halogen flame retardant adhesive resin mixture according to any one of claims 1 to 5 is used for an adhesive layer. A coverlay film, wherein the non-halogen flame retardant adhesive resin mixture according to any one of claims 1 to 5 is used for an adhesive layer. A flexible printed wiring board using the non-halogen flame retardant adhesive resin mixture according to any one of claims 1 to 5 for an adhesive layer.

Images