JP2007314742A - Adhesive composition, laminate of the same, and flexible printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an adhesive that is for a flexible printed wiring board, gives flame retardancy to the wiring board containing practically neither halogen element nor heavy metal element while satisfying such characteristics as electric insulation property, soldering heat resistance and adhesivity generally required for an adhesive for a flexible printed wiring board, and improves flexibility at a temperature beyond ambient temperature. <P>SOLUTION: The adhesive composition comprises a resin (A), that has a glass transition temperature of 30°C or above, and has a hydroxy group and/or a carboxy group and/or an amino group, these are each reactive with an epoxy resin, and the sum total of a hydroxyl value, an acid value, and an amino value is 2-60 mg KOH/g, a phosphorus-containing epoxy resin (Bp) or/and a mixture (Bm) of a phosphorus compound, having reactivity with an epoxy resin, and an epoxy resin, and an epoxy resin curing agent (C), wherein, a phosphorus content against an organic component in the total solid material is 1-10 wt.%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a metal-clad laminate for a flexible printed wiring board and an adhesive for a coverlay film, and in particular, electrical insulation, adhesiveness, solder heat resistance, and room temperature or higher required for the flexible printed wiring board. The present invention relates to a high-performance and environment-friendly adhesive composition that satisfies the flexibility and exhibits flame retardancy without containing halogen or antimony, and further relates to a laminate and an adhesive printed wiring board containing the adhesive.

A flexible printed wiring board is formed by forming a circuit from a copper-clad film obtained by bonding a polyester film or a polyimide film and a copper foil with an adhesive by an etching method, and the circuit is protected by laminating a polyimide film or the like with an adhesive. As can be seen from this configuration, the performance of the flexible printed wiring board largely depends on the performance of the adhesive layer. For example, if a high heat-resistant thermosetting resin is used to impart solder heat resistance to the adhesive, flexibility and adhesion are hindered. For this purpose, a thermosetting resin and a rubber component having a glass transition point of zero degrees or less are generally used in combination (for example, see Patent Document 1). However, in recent years, flexible printed wiring boards are required to have high performance with the development of electronic devices. For example, in order to directly mount a semiconductor chip on a flexible printed wiring board, higher heat resistance is required than before, or the flexibility required from a hard disk drive can withstand not only room temperature environment but also heat generation from equipment and in-vehicle environment. Thus, flexibility at 80 ° C. or higher has been required. Corresponding to these, attempts have been made to modify the rubber component with a heat-resistant resin (see, for example, Patent Document 2). In addition, halogen compounds and antimony compounds are used to impart flame retardancy to the adhesive layer from the viewpoint of safety. However, the use of halogen-free / heavy metals is required due to environmental and health issues. ing. For this reason, various phosphorus compounds have been studied (for example, see Patent Document 3). However, the problem of bleeding out of phosphorus compounds and copper migration caused by hydrolysis products of phosphorus compounds are problematic.
JP 2005-154512 A JP 2002-69270 A JP 2001-339132 A

  While satisfying general required characteristics such as electrical insulation, solder heat resistance, and adhesiveness required for the adhesive of the flexible printed wiring board, halogen-free used in the above-mentioned recent flexible printed wiring board, It is a problem to be solved by the present invention to impart flame retardancy without using a heavy metal such as antimony and to improve flexibility at a temperature of room temperature or higher.

  In order to solve the above problems, (1) a resin containing a hydroxyl group or / and a carboxyl group or / and an amino group and having a total hydroxyl value, acid value and amine value in the range of 2 to 60 mgKOH / g. A resin (A) having a glass transition temperature of 30 ° C. or higher, an epoxy resin (Bp) containing a phosphorus atom, and / or a mixture of a phosphorus compound and an epoxy resin having reactivity to the epoxy resin (Bm), and an epoxy An adhesive composition containing the resin curing agent (C) and having a phosphorus content of 1 to 10% by weight in the total organic content of the solid, (2) the adhesive composition is cured In the state where the adhesive composition of (1), (3) and (1) are laminated on a synthetic resin film or a synthetic resin plate, or a metal foil or a metal plate, Specially (4) The cured product of the adhesive composition of (2) is in a state of being laminated on a synthetic resin film or a synthetic resin plate, or a metal foil or a metal plate. And a cured printed wiring board comprising at least a part of the laminated structure of the cured adhesive composition of (5) and (4).

  Further, the present invention will be described. In the present invention, the resin contains a hydroxyl group or / and a carboxyl group or / and an amino group, and has a total hydroxyl value, acid value, and amine value in the range of 2 to 60 mgKOH / g, and its glass transition temperature. Uses a resin (A) of 30 ° C. or higher. Hydroxyl groups, carboxyl groups, and amino groups react with the epoxy compound, and the resin part responsible for flexibility and the cured epoxy resin part mainly responsible for heat resistance are integrated by chemical bonding to form a strong resin layer as a whole. It exhibits excellent thermal, mechanical, and chemical properties. If the sum of the hydroxyl group, carboxyl group and amino group is less than 2 mg KOH / g resin, the degree of crosslinking of the resin by the epoxy compound is lowered, and the solder heat resistance is insufficient. On the other hand, if the resin exceeds 60 mgKOH / g resin, the pot life of the adhesive composition and the shelf life of the coating are decreased, the degree of crosslinking is increased, the structure is hard and brittle, and the adhesiveness and flexibility are deteriorated.

  In the present invention, a resin having a glass transition temperature of 30 ° C. or higher is used. It goes without saying that the glass transition temperature of the adhesive layer depends on the density of crosslinking by the epoxy compound of the resin (A) and the structure of the crosslinked part, but even if the crosslinking density and the structure of the crosslinked part are the same, the resin It was found that the characteristics of the part (A) are reflected in the flexibility of the circuit. That is, when the temperature is higher than the glass transition temperature of the resin (A), the adhesive layer is not hard enough to prevent the growth of minute cracks on the metal surface formed by repeated bending, and the repeated flexibility of the circuit deteriorates. . In order to impart high flexibility at a temperature of room temperature or higher, the glass transition temperature of the resin (A) needs to be 30 ° C. or higher, preferably 80 ° C. or higher, more preferably 100 ° C. or higher. It is not preferable to include a rubber component having a temperature.

  Examples of the resin (A) used in the present invention include a polyester resin, a polycarbonate resin, a polyester urethane resin, a polycarbonate urethane resin, a polyamide resin, a polyamideimide resin, and a polyimide resin containing a hydroxyl group or / and a carboxyl group or / and an amino group. Of these, the total of hydroxyl value, acid value, and amine value (other than at least one of hydroxyl value, acid value, and amine value may be 0) is 2 to 60 mgKOH / g, and the glass transition temperature is 30 Resin having a temperature of ℃ or higher. Among them, a resin containing a phosphorus atom or a nitrogen atom is desirable from the viewpoint of imparting flame retardancy, and a polyester resin, a polyester urethane resin, a polycarbonate urethane resin, a polyamideimide resin, or a polyimide resin obtained by copolymerizing a phosphorus-containing diol is preferable. The ratio of the resin (A) component to the organic content in the total solid is 5% by weight to 95% by weight. If it is less than 5% by weight, the adhesiveness and flexibility cannot be satisfied, and if it exceeds 95% by weight, the heat resistance is insufficient.

  The epoxy resin (Bp) containing phosphorus atoms used in the present invention is an epoxy resin in which phosphorus atoms obtained by reacting a phosphorus compound having reactivity with a normal epoxy resin with an epoxy resin are chemically bonded. . Specifically, a reaction product of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide or a derivative thereof and an epoxy resin, 1,4-cyclooctylene phosphine oxide or 1,5-cyclohexane Examples include a reaction product of octylene phosphine oxide and an epoxy resin, a reaction product of n-butyl-bis (3-hydroxypropyl) phosphine oxide, tris (3-hydroxypropyl) phosphine oxide and an epoxy resin, and the like. Further, instead of separately preparing an epoxy resin having phosphorus atoms bonded thereto, a mixture (Bm) of the above phosphorus compound and epoxy resin having reactivity to the epoxy resin may be directly used. The ratio of the epoxy resin to the organic content in the total solid is 5 to 80% by weight. If it is less than 5% by weight, the solder heat resistance cannot be satisfied, and if it exceeds 80% by weight, the adhesiveness and the flexibility are deteriorated. The content of phosphorus atoms with respect to the organic content in the entire solid is 1 to 10% by weight. If the content is less than 1% by weight, sufficient flame retardancy is not exhibited. It is inconvenient and disturbing. As for the content rate of the phosphorus atom which occupies for the organic content in all the solid substances, 2 to 5 weight% is preferable. In order to adjust the amount of the epoxy resin used and the phosphorus atom content in the total solid, it is possible to use an epoxy resin containing no phosphorus atom in combination.

  Epoxy resins that can be used in the present invention are polyphenol compounds such as glycidyl such as bisphenol A and its alkyl-substituted products, bisphenol F and its alkyl-substituted products, bisphenol S and its alkyl-substituted products, various novolak resins, and phenols having a fluorene skeleton. Examples include etherified products, alicyclic epoxy resins, heterocyclic epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, and the like.

  Examples of the epoxy resin curing agent (C) used in the present invention include acid anhydrides, phenols, amines, isocyanates, blocked isocyanates, etc. Among them, acid anhydride systems that can react with the resin (A) used in the present invention. For example, phthalic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic acid anhydride, alkylene glycol trimellitic anhydride ester and the like are preferable. Further, from the viewpoint of imparting flame retardancy, amines, for example, aromatic amines such as diaminodiphenylmethane, aliphatic amines such as ethylenediamine, and curing agents containing nitrogen atoms such as dicyandiamide and diphenylmethane diisocyanate are also desirable. Moreover, these hardeners can also be mixed and used. The usage-amount of these hardening | curing agents is 0.1-2 normally with respect to the equivalent number of the epoxy group of an epoxy resin, Preferably it is 0.2-1.5.

  Further, substituted imidazoles such as 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-phenylimidazole, tertiary amines, phosphines, Lewis acid complexes, etc. are used in combination as curing catalysts or curing accelerators. You can also. These are usually used in an amount of 0.01 to 3 parts by weight with respect to 100 parts by weight of the epoxy resin.

  In the adhesive composition of the present invention, other organic substances, inorganic substances, metals, and the like can be added and used as necessary. For example, inorganic flame retardant such as aluminum hydroxide, magnesium hydroxide, magnesium aluminate, calcium aluminate, inorganic filler such as silica, alumina, talc, glass beads, glass fiber, silica fiber, alumina fiber, silica alumina fiber, etc. Inorganic reinforcing fiber, organic reinforcing fiber such as aramid fiber, polyester fiber, graphite, ketjen black, silver powder, copper powder, aluminum powder, carbon fiber, metal fiber and other conductive agents, silane coupling agent, titanium-based coupling agent Coupling agents such as aluminum-based coupling agents, phosphorus-based adhesion improvers, antioxidants, ultraviolet absorbers, thixotropic agents, antistatic agents, antifoaming agents, lubricants, and the like can be blended.

  The adhesive composition of the present invention includes a resin (A), an epoxy resin (Bp) containing a phosphorus atom, and / or a mixture of a phosphorus compound having reactivity with an epoxy resin and an epoxy resin (Bm), an epoxy resin curing agent. (C) It is used as an adhesive solution or / and a dispersion in which other additives are dissolved or uniformly dispersed in a solvent. Solvents include ketone solvents such as methyl ethyl ketone and cyclohexanone, hydrocarbon solvents such as toluene and xylene, ether solvents such as tetrahydrofuran, dioxane and ethylene glycol dimethyl ether, alcohol solvents such as ethyl alcohol, isopropyl alcohol and ethyl cellosolve, Aprotic polar solvents such as dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone and a mixed solvent of two or more of these can be used. The solid content concentration of the adhesive solution or dispersion (varnish) is usually 5% by weight to 90% by weight. It can be appropriately selected in consideration of the desired thickness of the adhesive layer after drying, coating suitability, drying equipment, productivity, and the like.

  An adhesive solution or dispersion (varnish) can be coated on a synthetic resin film, metal foil, etc., the solvent can be dried, and another film, metal foil, paper, etc. can be bonded to it. As the coating, an existing coater can be applied, but a comma coater and a reverse roll coater are particularly preferable. Drying is performed in the drying zone of the coater, and the solvent is usually removed by heating at 40 to 180 ° C. for 1 to 30 minutes to form an adhesive layer. The thickness of the adhesive layer after drying is usually 5 to 50 μm. At this stage, the thermoplasticity is maintained (B-stage), and it can be continuously laminated with another substrate and bonded by a roll laminator or a flat plate heat press. It is also possible to coat both substrates to be bonded. The pressing conditions are usually 50 to 200 ° C. and 0.1 to 5 MPa, and 10 seconds to 30 minutes. Further, post-curing can be performed by heating at 50 to 150 ° C. for 1 to 24 hours.

  The adhesive composition of the present invention is suitable as an adhesive for flexible printed wiring board-related materials such as flexible printed wiring board substrates, coverlay films, bonding sheets, and binders for conductive pastes. The substrate for a flexible printed wiring board has a basic structure of a three-layer laminate of an electrically insulating film / adhesive layer / metal foil, and the thickness of the adhesive layer is usually 5 to 30 μm. The coverlay film is a three-layer laminate of an electrical insulating film / adhesive layer / release film (or release paper). The thickness of the adhesive layer is usually 20 to 90 μm, but is appropriately selected depending on the thickness of the circuit. When applied to a dry film type coverlay, it is a three-layer laminate of a release film / adhesive layer / release film (or release paper), and the adhesive layer also functions as an insulating film. The thickness of the adhesive layer is slightly thick and is usually 30 to 100 μm, but is appropriately selected depending on the thickness of the circuit. The bonding sheet is usually a three-layer laminate of release film / adhesive layer / release film (or release paper), and the thickness of the adhesive layer is usually 20 to 50 μm. In addition, a three-layer laminate of metal foil / adhesive layer / releasing film (or release paper) is used as a material for build-up multilayer wiring boards, and a two-layer laminate of metal foil / adhesive layer is a two-layer printed wiring. It can also be applied as a substrate.

  Examples of the electrical insulating film include a polyimide film, a polyester film, a polyarylene ester film, a polyaramid film, and a polyphenylene sulfide film. The thickness of the film is usually 12.5 μm to 100 μm, but a thicker one is also used when used as a reinforcing plate. Further, an epoxy resin plate, a phenol resin plate, a melamine resin plate or the like is also used as a reinforcing plate. Examples of the metal foil include electrolytic copper foil, rolled copper foil, aluminum foil, and stainless steel foil. The thickness of the metal foil is usually 9 μm to 70 μm, but a thicker one is used when used as a reinforcing plate. Examples of the releasable film include a polyethylene film, a polypropylene film, a polymethylpentene film or a polyester film coated with a silicone-based and / or fluorine-based release agent. Examples of the release paper include polyethylene-coated paper, polyethylene-coated paper and a silicone-based and / or fluorine-based release agent.

  The effects of the present invention satisfy the basic characteristics (electrical insulation, adhesiveness, solder heat resistance, etc.) required for the adhesive for flexible printed wiring board materials, and further adversely affect the environment such as halogens and heavy metals. This is because it contains no substances and suppresses copper migration due to phosphorus compound exudation and decomposition products to exhibit flame retardancy and to improve flexibility at a temperature above room temperature.

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples. An evaluation method will be described before describing examples.
(1) Resin hydroxyl value, acid value, amine value The acid value was determined by dissolving a predetermined amount of resin in chloroform and titrating with an ethanol solution of potassium hydroxide. The hydroxyl value is obtained by dissolving a predetermined amount of resin in chloroform, adding a predetermined amount of acetic anhydride to convert the hydroxyl group into acetate ester, and titrating the remaining acid with an ethanol solution of potassium hydroxide. Calculated from the acid equivalent of acetic anhydride-residual acid equivalent. The amine value is obtained by dissolving a predetermined amount of resin in chloroform, titrating with hydrochloric acid in ethanol, and converting to equivalent KOH.
(2) Glass transition temperature of resin Measured at 20 ° C./min using a differential scanning calorimeter (DSC).
(3) Preparation of sample for evaluation The solution or / and dispersion liquid of an adhesive composition are adjusted. However, in Examples 1 to 3, methyl ethyl ketone / toluene / dimethylformamide = 40/40/20 (weight ratio) was used as the solvent, and the solid content concentration was 46% by weight. In Comparative Examples 1 and 2, methyl ethyl ketone was used as the solvent. / Toluene = 80/20 (weight ratio) is used by adjusting the solid content concentration to 46% by weight. This solution or / and dispersion was applied to a treated surface of 35 μm electrolytic copper foil (F2-WS foil manufactured by Furukawa Circuit Foil Co., Ltd.), dried with hot air at 150 ° C. for 5 minutes, and then 25 μm polyimide film (Toray DuPont ( Co., Ltd. Kapton 100H) is roll-laminated and further cured at 160 ° C. and 3 MPa for 30 minutes, after hot pressing, and then cured at 120 ° C. for 12 hours to produce a copper-clad film.The thickness of the adhesive layer is 15 μm. It is.
(4) Solder heat resistance A 25 mm x 25 mm size copper-clad film is conditioned at 40 ° C and 90% RH for 24 hours, then immediately floated in a 260 ° C jet solder bath for 20 seconds, swelled, peeled off, etc. When there is no peeling, it is determined as OK. The others are NG (defective).
(5) Adhesive strength A sample with a width of 1 cm is pulled at a rate of 5 cm / min, and peeled 180 degrees.
(6) Folding strength Using a sample with a width of 1 cm, using a MIT testing machine (JIS P8115), record the number of times until a crack occurs at a bending radius of 0.8 mm, a load of 5 N, and 50 ° C.
(7) Flame retardancy Keep the 5mm wide etched sample vertically, ignite with a cigarette lighter flame from the bottom, release the lighter flame, and observe the extent of fire spread. If the fire is extinguished within 5 seconds, OK (good), otherwise NG (bad).

  60 g of polyester resin (Byron 226 manufactured by Toyobo Co., Ltd., total number of functional groups 21 mg KOH / g, glass transition temperature 65 ° C.), 40 g of epoxy resin (jER154 manufactured by Japan Epoxy Resin Co., Ltd.), 9,10-dihydro-9-oxa -10-phosphaphenanthrene-10-oxide 35g, tetrahydrophthalic anhydride 6g, triphenylphosphine 0.02g as a catalyst, and an adhesive solution containing 2-ethyl-4-methylimidazole 0.7g A copper clad film was prepared. The evaluation results are shown in Table 1.

  Polyester urethane resin (Toyobo Co., Ltd. Byron UR-8200, total number of functional groups 6 mgKOH / g, glass transition temperature 73 ° C.) 50 g as solids, epoxy resin (Japan Epoxy Resin Co., Ltd. jER154) 33 g, n-butyl-bis Using an adhesive solution containing 35 g of (3-hydroxypropyl) phosphine oxide, 10 g of tetrahydrophthalic anhydride, 0.02 g of triphenylphosphine, and 0.7 g of 2-ethyl-4-methylimidazole, the copper-clad film was formed by the above method. Produced. The evaluation results are shown in Table 1.

  A reaction vessel equipped with a thermometer, stirrer, reflux condenser and distillation tube was charged with 100 g of a polyester resin (Toyobo Co., Ltd. Byron 885) and 70 g of toluene, dissolved, and then 20 g of toluene was distilled off. The reaction system was dehydrated by boiling. After cooling to 60 ° C., 50 g of methyl ethyl ketone and 15 g of a phosphorus-containing polyol (FC-450 manufactured by Asahi Denka Kogyo Co., Ltd.) were added. To this solution was added 8 g of hexamethylene diisocyanate and 0.4 g of dibutyltin dilaurate as a reaction catalyst. After reacting at 80 ° C. for 3 hours, 93.5 g of toluene and 93.5 g of methyl ethyl ketone were added to make the solid content concentration 30% by weight. A solution of phosphorus-containing polyester urethane resin was prepared. This phosphorus-containing polyester urethane resin (total number of functional groups: 40 mgKOH / g, glass transition temperature: 60 ° C.) 60 g as a solid content, epoxy resin (Japan Epoxy Resin Co., Ltd. jER154) 50 g, 9,10-dihydro-9-oxa-10- Using an adhesive solution containing 30 g of phosphaphenanthrene-10-oxide, 6 g of tetrahydrophthalic anhydride, 0.02 g of triphenylphosphine, and 0.7 g of 2-ethyl-4-methylimidazole, a copper-clad film is produced by the above method. did. The evaluation results are shown in Table 1.

Comparative Example 1

  Polyester urethane resin (Toyobo Co., Ltd. Byron UR-3500, total number of functional groups 45 mg KOH / g, glass transition temperature 10 ° C.) 50 g as solid content, epoxy resin (Japan Epoxy Resin Co., Ltd. jER154) 25 g, epoxy resin (Japan Epoxy) Resin Co., Ltd. jER871) 25 g, tetrahydrophthalic anhydride 6 g, and an adhesive solution containing 0.7 g of 2-ethyl-4-methylimidazole as a catalyst was used to prepare a copper-clad film by the above method. The evaluation results are shown in Table 1.

Comparative Example 2

Nitrile Butadiene Rubber (NBR) (Nippon Zeon Co., Ltd. Nipol 1072J, total functional group 39 mg KOH / g, glass transition temperature -35 ° C.) 40 g, epoxy resin (Japan Epoxy Resin Co., Ltd. jER154) 30 g, epoxy resin (Japan Epoxy Resin) A copper-clad film was prepared by the above-mentioned method using an adhesive solution containing 30 g of jER871), 6 g of tetrahydrophthalic anhydride, and 0.7 g of 2-ethyl-4-methylimidazole as a catalyst. The evaluation results are shown in Table 1.

Claims (5)

  Resin containing a hydroxyl group or / and a carboxyl group or / and an amino group and having a total hydroxyl value, acid value, and amine value in the range of 2 to 60 mgKOH / g and having a glass transition temperature of 30 ° C. or higher (A), an epoxy resin (Bp) containing a phosphorus atom, and / or a mixture of a phosphorus compound having reactivity with an epoxy resin and an epoxy resin (Bm), and an epoxy resin curing agent (C), all solids An adhesive composition, wherein the content of phosphorus in the organic content is 1 to 10% by weight.   The adhesive composition according to claim 1, wherein the adhesive composition is cured.   The laminate of an adhesive composition according to claim 1, wherein the adhesive composition is in a state of being laminated on a synthetic resin film or a synthetic resin plate, or a metal foil or a metal plate.   The cured adhesive composition according to claim 2, wherein the cured adhesive composition is in a state of being laminated on a synthetic resin film or a synthetic resin plate, or a metal foil or a metal plate. body.   A flexible printed wiring board comprising at least a part of the laminate structure according to claim 4.