JP2013142092A - Conductive adhesive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive adhesive film which has stable conduction performance and avoids insufficient adhesion even when used for connecting a wiring member to an electrode of a solar cell substrate which is subjected to heating-cooling cycles in the open air over a long period of time.SOLUTION: The conductive adhesive film comprises a phenoxy resin, an epoxy resin including at least a rubber modified epoxy resin or a urethane modified epoxy resin, a silane coupling agent, a latent curing agent for the epoxy resin, an acrylic resin, and a conductive filler.

Description

  The present invention relates to a conductive adhesive film that electrically connects wiring members and electrodes facing each other on a circuit board and the like, and in particular, electrically connects the electrodes and wiring members in a solar cell substrate subjected to repeated heating and cooling due to a temperature difference. The present invention relates to a conductive adhesive film.

  Conventionally, as a conductive adhesive film for electrically connecting electrodes facing each other on a wiring member and a circuit board, polyhydroxy polyether resin, synthetic rubber, epoxy resin, curing agent as disclosed in Patent Document 1 A sheet-like adhesive composition characterized by containing conductive particles has been proposed (Patent Document 1). Also, an adhesive for connecting a circuit member, which is interposed between opposing circuit electrodes and pressurizes the opposing circuit electrodes to electrically connect the electrodes in the pressurizing direction, with 100 parts by weight of the adhesive resin composition There has been proposed an adhesive for connecting circuit members characterized in that it contains 5 to 200 parts by weight of an inorganic filler (Patent Document 2).

JP 2000-86981 A JP-A-11-61088

  However, the sheet-like adhesive composition disclosed in Patent Document 1 discards the electronic component device when a connection failure occurs due to misalignment between electrodes in the connection process between the circuit board and the wiring member. Without being solvated and swollen with a specific organic solvent, and formed so as to be peelable from the electrode. When used for connecting wiring members, there is a problem that the adhesiveness may be insufficient.

  Moreover, the adhesive for circuit member connection of patent document 2 contains 5 to 200 parts by weight of an inorganic filler as an essential component, and the inorganic filler is fused silica, crystalline silica, calcium silicate, alumina, calcium carbonate, or the like. Because it contains at least 5 parts by weight, when conductive particles are added to this, an inorganic filler may be interposed between the conductive particles and the electrode, resulting in insufficient conduction. There was a problem that it might become.

  The problem to be solved by the present invention is that the adhesiveness does not become insufficient even when it is used for the connection between the electrode of the solar cell substrate and the wiring member which are repeatedly subjected to the thermal cooling outdoors for a long time, and the conductive It is not always necessary to include an inorganic filler other than the conductive filler. For this reason, an object is to provide a conductive adhesive film having stable conductive performance.

  The invention described in claim 1 includes a phenoxy resin, an epoxy resin containing at least a rubber-modified epoxy resin or a urethane-modified epoxy resin, a silane coupling agent, an epoxy resin latent curing agent, an acrylic resin, and a conductive filler. And a conductive adhesive film.

The invention described in claim 2 is the conductive adhesive film according to claim 1, wherein the rubber-modified epoxy resin is an NBR-modified epoxy resin.

  The invention according to claim 3 is the conductive adhesive film according to claim 1 or 2, wherein the silane coupling agent is epoxy silane.

  The conductive adhesive film according to the present invention does not have insufficient adhesion even if it is used for electrical connection between the electrode and the wiring member of the solar cell substrate that is installed outdoors for a long time and is subjected to repeated heating and cooling, Moreover, since it is not always necessary to include an inorganic filler other than the conductive filler, there is an effect of having a stable conduction performance when used for connecting the circuit board and the wiring member.

  The present invention will be described in detail below.

  The conductive adhesive film of the present invention includes a phenoxy resin, an epoxy resin containing at least a rubber-modified epoxy resin or a urethane-modified epoxy resin, a silane coupling agent, an epoxy resin latent curing agent, an acrylic resin, And an antifoaming agent, a leveling agent, a thixotropic agent, a diluent, a tackifier, and a flame retardant, if necessary.

Phenoxy resin The phenoxy resin used in the present invention is not particularly limited, but those having a weight average molecular weight of 20,000 to 100,000 are preferred. By using these phenoxy resins, the composition before film formation according to the present invention can be dissolved in an organic solvent and can be easily formed into a film by a cast coating method, a melt extrusion method or the like. Further, the conductive adhesive film of the present invention contains an epoxy resin containing the following modified epoxy resin in addition to the phenoxy resin, and further contains a latent curing agent for the epoxy resin. Functions as a thermosetting resin. As a commercial product of phenoxy resin, there is phenototoy YP-50 (pellet-like solid, weight average molecular weight: 60000-80000, manufactured by Nippon Steel Chemical Co., Ltd.).

Rubber-modified epoxy resin A rubber-modified epoxy resin is a product obtained by reacting a rubber compound with an epoxy resin. Examples of the rubber compound include butadiene acrylonitrile rubber (NBR), styrene butadiene rubber (SBR), hydrogenated nitrile rubber ( Examples thereof include rubber polymers such as HNBR) ethylene propylene rubber (EPDM), acrylic rubber (ACM), butyl rubber (IIR), and butadiene rubber. The end of the rubber polymer may be amino-modified, hydroxy-modified, or carboxyl-modified. A product obtained by reacting these rubber polymer and epoxy resin in an appropriate blending ratio by a known polymerization method is a rubber-modified epoxy resin used in the present invention, and preferably an NBR-modified epoxy resin is used. . The rubber-modified epoxy resin preferably has an epoxy equivalent of 200 to 1000 g / eq. When the epoxy equivalent is in this range, a tough film can be formed, and the workability and adhesiveness are also improved. A commercially available product is Adeka Resin EPR-4030 (60 Pa · s / 50 ° C., epoxy equivalent: 365 g / eq, manufactured by ADEKA) as an NBR-modified epoxy resin. The blending amount is 1 part by weight or more and less than 200 parts by weight, and more preferably 10 parts by weight or more and less than 100 parts by weight with respect to 100 parts by weight of the phenoxy resin. If it is less than 1 part by weight, the adhesive strength is insufficient, and if it is 200 parts by weight or more, film formation becomes difficult. If it is less than 10 parts by weight, the adhesive strength tends to be insufficient, and if it is 100 parts by weight or more, film formation tends to be difficult.

Urethane-modified epoxy resin The urethane-modified epoxy resin used in the present invention refers to a product obtained by reacting an epoxy resin with a urethane prepolymer containing an isocyanate group. The epoxy equivalent of the urethane-modified epoxy resin is preferably 100 to 1000 g / eq. When the epoxy equivalent is in this range, a tough film can be formed, and the workability and adhesiveness are also improved. As a commercial item, there is Adeka Resin EPR-78-13s (30 Pa · s / 25 ° C., epoxy equivalent: 210 g / eq, manufactured by ADEKA). The blending amount is 1 part by weight or more and less than 200 parts by weight, and more preferably 10 parts by weight or more and less than 50 parts by weight with respect to 100 parts by weight of the phenoxy resin. If it is less than 1 part by weight, the adhesive strength is insufficient, and if it is 200 parts by weight or more, film formation becomes difficult. If it is less than 10 parts by weight, the adhesive strength tends to be insufficient, and if it is 50 parts by weight or more, film formation tends to be difficult.

In the present invention, an epoxy resin containing at least one modified epoxy resin selected from the above-mentioned rubber-modified epoxy resin or urethane-modified epoxy resin is used, and the cured adhesive adhesive film is peeled off by blending these modified epoxy resins. The property that the peel strength after heating can be maintained at a certain level or more with the strength maintained high. Epoxy resins other than rubber-modified epoxy resin or urethane-modified epoxy resin are bisphenol A type, bisphenol F type, bisphenol S type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol AF type, bisphenol E type, naphthalene type, A bifunctional epoxy resin such as a phenol novolac type or a polyfunctional epoxy resin can be used, and these can be used alone or in combination of two or more. The blending amount of the epoxy resin other than the rubber-modified epoxy resin or the urethane-modified epoxy resin is preferably 40 parts by weight or more and less than 110 parts by weight with respect to 100 parts by weight of the phenoxy resin. If it is less than 40 parts by weight, the adhesive strength is insufficient, and if it exceeds 110 parts by weight, curing is insufficient.

Silane coupling agent Examples of the silane coupling agent include 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and 3-glycidoxypropyltrimethyl having an epoxy group. Epoxy silanes such as ethoxysilane and epoxy silanes such as 3-glycidoxypropyl monomethyldimethoxysilane can be used. A commercially available product is DYNASYLAN GLYMO (3.7 mPa · s / 20 ° C., EVONIK) as 3-glycidoxypropyltrimethoxysilane. The amount is from 0.1 parts by weight to less than 30 parts by weight, more preferably from 1 part by weight to less than 15 parts by weight, based on 100 parts by weight of the phenoxy resin. If it is less than 0.1 part by weight, the adhesive strength is insufficient, and if it is 30 parts by weight or more, curing is insufficient. Further, if it is less than 1 part by weight, the adhesive strength tends to be insufficient, and if it is 15 parts by weight or more, it tends to be insufficiently cured.

Epoxy resin latent curing agent Epoxy resin latent curing agent can be selected from imidazole, hydrazide, modified polyamine, boron trifluoride amine complex, guanamine, melamine, and urea. It is desirable to consist of at least one. As an imidazole-based commercial product, there is Curazole 2MZ-H (solid, imidazole-based, manufactured by Shikoku Kasei Co., Ltd.). In addition, the latent curing agent may be microencapsulated by coating with a polymer material such as polyurethane, polyurea, polyester, etc. As a commercial product of the microencapsulated latent curing agent, NovaCure HX-3941HP (35% microencapsulated latent curing agent, 15% bisphenol A type liquid epoxy resin, 50% bisphenol F type liquid epoxy resin, manufactured by Asahi Kasei E-Materials). NovaCure HX-3941HP is obtained by dispersing a microencapsulated latent curing agent in a liquid epoxy resin. The blending amount of the latent curing agent is 1 part by weight or more and less than 200 parts by weight, more preferably 10 parts by weight or more and less than 100 parts by weight with respect to 100 parts by weight of the phenoxy resin. If it is less than 1 part by weight, curing is insufficient, and if it is more than 200 parts by weight, the storage stability is deteriorated. Further, if it is less than 10 parts by weight, curing tends to be insufficient, and if it is 100 parts by weight or more, storage stability tends to be poor.

Acrylic resin The acrylic resin used in the present invention is not particularly limited, but an acrylic resin having a glass transition temperature Tg of -40C to 60C is preferred. As a commercial product, there is Nipol AR31 (trade name, glass transition temperature Tg: −15 ° C. (by DSC), manufactured by Nippon Zeon Co., Ltd.). The amount is from 1 part by weight to less than 150 parts by weight, more preferably from 5 parts by weight to less than 50 parts by weight, based on 100 parts by weight of the phenoxy resin. If it is less than 1 part by weight, stress relaxation is insufficient, and if it is 150 parts by weight or more, curing is insufficient. If the amount is less than 5 parts by weight, the stress relaxation tends to be insufficient. If the amount is 50 parts by weight or more, there is a tendency for the curing to be insufficient.

Conductive filler In the present invention, metal particles such as gold, silver, nickel, copper, zinc, tin, and the like, and conductive fillers obtained by applying gold plating or nickel plating to the metal particles can be used. As a commercial item, there is nickel powder 4SP10 (powder solid, average particle diameter 7 μm, manufactured by NOVAMENT). The blending amount is 0.1 part by weight or more and less than 300 parts by weight, more preferably 1 part by weight or more and less than 200 parts by weight with respect to 100 parts by weight of the phenoxy resin. If the amount is less than 0.1 parts by weight, conduction failure is caused. If the amount is 300 parts by weight or more, the aggregation of the conductive filler increases and the production becomes impossible. Further, if it is less than 1 part by weight, there is a tendency for poor conduction, and if it is 200 parts by weight or more, aggregation of the conductive filler tends to increase during stirring. The average particle size of the conductive filler measured by particle size distribution measurement is desirably 1 μm or more and less than 20 μm, and more preferably 5 μm or more and less than 15 μm. If it is less than 1 μm, conduction failure occurs, and if it is 20 μm or more, it becomes impossible to manufacture. If the thickness is less than 5 μm, there is a tendency for poor conduction, and if it is 15 μm or more, the manufacturing tends to be difficult.

  The conductive film according to the present application is desirably formed to a thickness of 100% to 500% with respect to the average particle diameter of the conductive filler to be blended. As a result, when the conductive adhesive film of the present invention is used for heating and pressurizing to connect the facing members such as the wiring member and the circuit board, the film can be easily melted and flown in a short time. A bond can be formed.

  Hereinafter, the conductive adhesive film according to the present application will be specifically described in Examples and Comparative Examples.

Example 1 to Example 5
Epototo YP50 (trade name, manufactured by Nippon Steel Chemical Co., Ltd.) as a phenoxy resin, Nipol AR31 (trade name, manufactured by Nippon Zeon Co., Ltd.) as an acrylic resin, NBR modified epoxy resin Adeka Resin EPR-4030 (trade name, ADEKA) as a rubber-modified epoxy resin Adeka Resin EPR-78-13s (trade name, manufactured by ADEKA) was used as a urethane-modified epoxy resin, and 100 parts by weight of ethyl acetate was added to each predetermined part by weight shown in Table 1 to prepare an ethyl acetate solution. (Table 1 does not indicate the number of ethyl acetate blended parts). 8 parts by weight of nickel powder 4SP10 (trade name, manufactured by NOVAMENT) having an average particle diameter of 7 μm is added to the solution as a conductive filler. Next, 40 parts by weight of a microcapsule type latent curing agent-containing liquid epoxy resin NovaCure HX-3941HP (trade name, manufactured by Asahi Kasei E-Materials) and 3-glycidoxypropyltrimethoxysilane DYNASYLAN GLYMO (trade name, EVONIC) 2) parts by weight are added and stirred uniformly to obtain a mixed solution before film formation. The mixed solution is uniformly applied to PET film NP38SA (trade name, manufactured by Panac Co., Ltd.) with a film applicator SA-204 (manufactured by Sheen Co., Ltd.) to about 40 to 50 μm, and then dried at 80 ° C. for 5 minutes to obtain ethyl acetate Is volatilized out of the coating film. Using a film thickness measuring device DIGIMICRO (manufactured by NIKON), confirming that the thickness of the conductive adhesive film formed on the PET film is 20 to 25 μm, the conductive adhesive films of Examples 1 to 5 Got.

Comparative Examples 1 to 4
In the formulation shown in Table 1, instead of the rubber-modified epoxy resin or urethane-modified epoxy resin compounded in Examples 1 to 5, naphthalene type epoxy resin EPICLON
EXA4032 (trade name, epoxy equivalent: 145-157 g / eq, manufactured by Dainippon Ink & Chemicals) or bisphenol A type epoxy resin EP828 (trade name, epoxy equivalent: 184-194 g / eq, manufactured by Mitsubishi Chemical) or EO-modified epoxy Resin Adeka Resin EP-4010 (trade name, epoxy equivalent: 350 g / eq, manufactured by ADEKA) was blended, and conductive adhesive films of Comparative Examples 1 to 3 were obtained by the same method. Moreover, the conductive adhesive film of the comparative example 4 was obtained with the same method about the thing which does not mix | blend the rubber modified epoxy resin mix | blended in Example 1 thru | or Example 5, or a urethane modified epoxy resin.

Evaluation items and evaluation methods

Initial peel strength and initial conduction resistance value The conductive adhesive films of Examples 1 to 5 and Comparative Examples 1 to 4 peeled from the PET film were solar cells (125 mm × 125 mm × about 0.00 mm). 2 mm) is cut in accordance with the width of the electrode wiring (material: Ag paste, width 2 mm × length 125 mm) formed on the conductive wiring film for peel test having a width 2 mm × length 40 mm. The peel test conductive adhesive film was placed on the electrode of the solar battery cell at 23 ° C., and a ribbon wire (material: solder-plated copper, manufactured by Hitachi Cable, NoWarp, width 1.5 mm × length 100 mm) × Thickness of about 0.25 mm) is placed and heated and pressed by a pressure bonding device at 180 ° C. and 1 Mpa for 10 seconds, and the solar cell electrode and ribbon wire are bonded with a conductive adhesive film to form a test specimen. . The conduction resistance value between the electrode wiring and the ribbon wire of the obtained specimen was measured with a digital multimeter, and the measured value was used as the initial conduction resistance value. Next, the test specimen after measuring the conduction resistance was pulled with an Instron tensile tester 5500R (Instron), and the ribbon wire was pulled at 300 mm / min with a peel angle of 90 degrees, and the peel strength (N / cm) Was measured.

Peel strength after heating and conduction resistance value after heating The test piece prepared in the same manner as described above is left in a dryer at 85 ° C and 85RH% for 100 hours, slowly cooled to 23 ° C, and then the conduction resistance value is measured in the same manner. Then, the measured value was used as the conduction resistance value after heating, and the peel strength (N / cm) was measured in the same manner, and the measured value was used as the peel strength after heating.

Evaluation results The evaluation results are shown in Table 2.
The overall evaluation is that the initial peel strength and the peel strength after heating are 10.0 N / cm or more, the initial peel strength is 10.0 N / cm or more, and the peel strength after heating is 8.0 or more and less than 10.0 N / cm. The initial peel strength is 8.0 or more and less than 10.0 N / cm, the peel strength after heating is 8.0 or more and less than 10.0 N / cm, the initial peel strength is 8.0 N / cm or more, and the peel strength after heating is Less than 8.0 N / cm was rated as x, and initial peel strength and post-heating peel strength were less than 8.0 N / cm as xx. If the initial peel strength is 8.0 N / cm or more, the initial adhesiveness is judged to be sufficient, and if the peel strength after heating is similarly 8.0 N / cm or more, it is repeatedly subjected to repeated hot and cold outdoor action over a long period of time. Adhesiveness is sufficiently ensured even when used for connecting the electrode of the solar cell substrate and the wiring member. Further, if the initial peel strength and the peel strength after heating are 10.0 N / cm or more, the adhesiveness is even better.

As shown in Table 2, in Examples 1 to 5, the initial and post-heating conduction resistance values are 0.1Ω or less and have good electrical conductivity, and the initial peel strength and post-heat peel strength are It has 8.0 N / cm or more, and has sufficient adhesiveness even when subjected to a heat cooling action.

Claims (3)

  It consists of a phenoxy resin, an epoxy resin containing at least a rubber-modified epoxy resin or a urethane-modified epoxy resin, a silane coupling agent, an epoxy resin latent curing agent, an acrylic resin, and a conductive filler. Conductive adhesive film.   The conductive adhesive film according to claim 1, wherein the rubber-modified epoxy resin is an NBR-modified epoxy resin. The conductive adhesive film according to claim 1, wherein the silane coupling agent is epoxy silane.