Adhesive sheet for temporary fixing of electronic components

Abstract

To provide an adhesive sheet which is optimal for temporarily fixing an electronic component, includes an adhesive layer containing an acrylic adhesive, and has excellent characteristics at high temperature.SOLUTION: An adhesive sheet for temporarily fixing an electronic component according to the present invention includes an adhesive layer containing an acrylic adhesive, where the acrylic adhesive contains an acrylic polymer, and the coefficient of linear expansion of the adhesive layer at 200 to 210°C is from 1×10-5 / K to 500×10-5 / K. In one embodiment, the coefficient of linear expansion of the adhesive layer at 230 to 240°C is from 1×10-5 / K to 500×10-5 / K.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet for temporarily fixing electronic components. [Background technology]

[0002] In flip-chip bonding technology, in which small electronic components (e.g., mini-LED or micro-LED chips) are temporarily fixed to an adhesive sheet and then mounted on a circuit board, a method is known in which multiple electronic components are arranged on an adhesive sheet at a predetermined interval and then thermally bonded all at once (e.g., Patent Document 1).The adhesive sheet used in such a heating process is required to have dimensional stability and heat resistance (particularly, low outgassing during heating) to maintain the positional relationship of the arranged electronic components (e.g., Patent Document 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6691184 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-170690 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a pressure-sensitive adhesive sheet that has a pressure-sensitive adhesive layer containing an acrylic pressure-sensitive adhesive, has excellent properties at high temperatures, and is ideal for temporarily fixing electronic components. [Means for solving the problem]

[0005] The pressure-sensitive adhesive sheet for temporarily fixing electronic components of the present invention comprises a pressure-sensitive adhesive layer containing an acrylic pressure-sensitive adhesive, the acrylic pressure-sensitive adhesive containing an acrylic polymer, and the pressure-sensitive adhesive layer has a linear expansion coefficient of 1×10 at 200°C to 210°C. -5 / K~500×10 -5 / K. In one embodiment, the pressure-sensitive adhesive layer has a linear expansion coefficient of 1×10 -5 / K~500×10 -5 / K. In one embodiment, the pressure-sensitive adhesive layer has a storage modulus G' at 200°C of 0.05 MPa or more. In one embodiment, the pressure-sensitive adhesive layer has a 5% weight loss temperature of 320°C to 400°C. In one embodiment, the pressure-sensitive adhesive layer has a gel fraction of 93% to 99.99%. In one embodiment, the pressure-sensitive adhesive layer further comprises an epoxy-based crosslinking agent, and the acrylic polymer comprises a constituent unit derived from a carboxy group-containing monomer. In one embodiment, the pressure-sensitive adhesive layer further comprises an isocyanate-based crosslinking agent, and the acrylic polymer comprises a constituent unit derived from a hydroxyl group-containing monomer. In one embodiment, the acrylic polymer contains constitutional units derived from a polyfunctional monomer. In one embodiment, the polyfunctional monomer is trimethylolpropane triacrylate. In one embodiment, the acrylic pressure-sensitive adhesive further comprises a crosslinking catalyst. In one embodiment, the crosslinking catalyst is dioctyltin dilaurate or triethylenediamine. In one embodiment, the acrylic polymer has a weight average molecular weight Mw of 600,000 to 1,600,000. In one embodiment, the pressure-sensitive adhesive sheet further includes a substrate, and the pressure-sensitive adhesive layer is disposed on at least one surface of the substrate. In one embodiment, the pressure-sensitive adhesive sheet is used in a flip-chip bonding process, a resin sealing process, and a rewiring layer formation process for semiconductor elements. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet that has a pressure-sensitive adhesive layer containing an acrylic pressure-sensitive adhesive, has excellent properties at high temperatures, and is optimal for temporarily fixing electronic components. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] A. Overall structure of adhesive sheet for temporary fixing of electronic components Fig. 1(a) is a schematic cross-sectional view of an adhesive sheet for temporarily fixing electronic components (hereinafter also simply referred to as adhesive sheet) according to one embodiment of the present invention. The adhesive sheet 100 includes an adhesive layer 10. The adhesive layer 10 contains an acrylic adhesive. The adhesive layer 10 has a linear expansion coefficient of 1 x 10 at 200°C to 210°C. -5 / K~500×10 -5 / K.

[0009] 1(b) is a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to another embodiment of the present invention. The pressure-sensitive adhesive sheet 200 further comprises a substrate 20, and a pressure-sensitive adhesive layer 10 is disposed on at least one surface of the substrate 20.

[0010] Although not shown, the pressure-sensitive adhesive sheet may further include layers other than the pressure-sensitive adhesive layer 10, if necessary. For example, other pressure-sensitive adhesive layers, resin layers, etc. may be disposed. Also, a separator may be disposed releasably on the pressure-sensitive adhesive layer.

[0011] The adhesive strength of the adhesive layer of the pressure-sensitive adhesive sheet of the present invention when adhered to SUS304 at an ambient temperature of 25°C is preferably 0.1 N / 20 mm to 20 N / 20 mm, more preferably 0.1 N / 20 mm to 18 N / 20 mm, and even more preferably 0.2 N / 20 mm to 12 N / 20 mm. Within these ranges, a pressure-sensitive adhesive sheet can be obtained that exhibits favorable fixation and releasability. In this specification, the adhesive strength refers to the adhesive strength measured according to a method in accordance with JIS Z 0237:2000 (lamination conditions: one reciprocal movement of a 2 kg roller, tensile speed: 300 mm / min, peel angle: 180°).

[0012] The thickness of the pressure-sensitive adhesive sheet is preferably 1 μm to 200 μm, and more preferably 3 μm to 150 μm.

[0013] The pressure-sensitive adhesive sheet is used for temporarily fixing electronic components. In this specification, "temporarily fixing" means fixing electronic components to an extent that allows for predetermined processing (e.g., a sealing process) and allows for peeling. For example, by adjusting the adhesive strength within the above range, a pressure-sensitive adhesive sheet capable of temporary fixation can be obtained. Typically, the pressure-sensitive adhesive sheet is used in a process in which heating is performed at a predetermined temperature (e.g., 200°C or higher, preferably 200°C to 300°C, more preferably 230°C to 270°C). The pressure-sensitive adhesive sheet of the present invention is advantageous in that it undergoes little dimensional change even at high temperatures. By using the pressure-sensitive adhesive sheet, it is possible to process a plurality of electronic components arranged on the pressure-sensitive adhesive sheet (e.g., a process involving heating, such as sealing) while maintaining the positional relationship of the electronic components. Conventionally, when heat resistance is a consideration, silicone-based pressure-sensitive adhesive sheets have been frequently used. However, the pressure-sensitive adhesive sheet of the present invention has superior heat resistance compared to conventional silicone-based pressure-sensitive adhesive sheets, and can exhibit the above-mentioned excellent properties even at temperatures of, for example, about 260°C. In one embodiment, the pressure-sensitive adhesive sheet is used in a flip-chip bonding process, a resin sealing process, and a rewiring layer formation process for semiconductor elements. These applications particularly require dimensional stability under heat, and the use of the pressure-sensitive adhesive sheet of the present invention allows these processes to be carried out with good productivity.

[0014] The size of the electronic component is, for example, 1 μm 2 ~100mm 2 In one embodiment, a plurality of the electronic components can be arranged on the pressure-sensitive adhesive sheet, and the intervals between them are, for example, 1 μm to 10 mm.

[0015] B.Adhesive layer As described above, the linear expansion coefficient of the pressure-sensitive adhesive layer at 200°C to 210°C is 1×10 -5 / K~500×10 -5 The pressure-sensitive adhesive layer preferably has a linear expansion coefficient of 1×10 -5 / K~250×10 -5 / K, and more preferably 1×10 -5 / K~150×10 -5 / K, and more preferably 1×10 -5 / K~100×10 -5 / K, more preferably 1 × 10 -5 / K~60×10 -5 / K, and particularly preferably 1×10 -5 / K~45×10 -5 / K. Within this range, the effects of the present invention are significant. The linear expansion coefficient of the pressure-sensitive adhesive layer can be controlled by the composition of the base polymer that constitutes the acrylic pressure-sensitive adhesive, the type and content of the cross-linking agent added to the acrylic pressure-sensitive adhesive, etc. The linear expansion coefficient can be analyzed by thermomechanical analysis (TMA). Specifically, the linear expansion coefficient is measured by increasing the temperature from 20°C to 300°C at a rate of 10°C / min under conditions of tensile mode, nitrogen gas flow rate: 50.0 ml / min, and load: 0.0196 N, and measuring the sample displacement within a predetermined temperature range (e.g., 200°C to 210°C, 230°C to 240°C).

[0016] The pressure-sensitive adhesive layer preferably has a linear expansion coefficient of 1×10 -5 / K~500×10 -5 / K, and more preferably 1×10 -5 / K~350×10 -5 / K, and more preferably 1×10-5 / K~200×10 -5 / K, and more preferably 1×10 -5 / K~150×10 -5 / K, more preferably 1 × 10 -5 / K~100×10 -5 / K, and particularly preferably 1×10 -5 / K~80×10 -5 Within this range, the effect of the present invention becomes significant.

[0017] The pressure-sensitive adhesive layer preferably has a storage modulus G' at 200°C of 0.05 MPa or more, more preferably 0.06 MPa or more, and more preferably 0.07 MPa or more. Within this range, it is possible to prevent displacement of the adherend (object to be processed) even at high temperatures, and to obtain a pressure-sensitive adhesive sheet with appropriate adhesiveness. The higher the storage modulus G' at 200°C of the pressure-sensitive adhesive layer, the better, and the upper limit is, for example, 100 MPa, preferably 80 MPa. The storage modulus G' can be measured using a dynamic viscoelasticity measuring device under the following measurement conditions for an evaluation sample (pressure-sensitive adhesive layer) with a diameter of 8 mm and a thickness of 1 mm. Distortion: 0.05% Frequency: 1Hz Measurement range: -50℃~260℃ Heating rate: 5℃ / min

[0018] The 5% weight loss temperature of the pressure-sensitive adhesive layer is preferably 320°C to 400°C, more preferably 330°C to 390°C, and even more preferably 340°C to 380°C. Within these ranges, a pressure-sensitive adhesive sheet with little outgassing under heating can be obtained. The 5% weight loss temperature of the pressure-sensitive adhesive layer can be controlled by the composition of the base polymer that constitutes the acrylic pressure-sensitive adhesive, the type and content of the crosslinking agent added to the acrylic pressure-sensitive adhesive, etc. The 5% weight loss temperature refers to the temperature at which the weight of the pressure-sensitive adhesive layer has decreased by 5% relative to its initial weight when thermogravimetry (TG) measurement is performed under the following conditions: Measurement temperature range: 20℃~500℃ Temperature rise: 10°C / min Atmospheric gas: Nitrogen Gas flow rate: 25 ml / min

[0019] The gel fraction of the pressure-sensitive adhesive layer is preferably 93% to 99.99%, more preferably 94% to 99.99%, and even more preferably 95% to 99.99%. Within these ranges, it is possible to prevent displacement of the adherend (object to be processed) even at high temperatures, and to obtain a pressure-sensitive adhesive sheet with appropriate adhesiveness. The gel fraction of the pressure-sensitive adhesive layer can be controlled by adjusting the composition of the base polymer constituting the acrylic pressure-sensitive adhesive, the type and content of the crosslinking agent added to the acrylic pressure-sensitive adhesive, the type and content of the tackifier, etc. The gel fraction is measured as follows. Approximately 0.5 g of the adhesive layer was sampled and precisely weighed (sample weight), and the sample was wrapped in a mesh sheet (trade name "NTF-1122", manufactured by Nitto Denko Corporation) and then immersed in 50 ml of toluene at room temperature (25°C) for one week. Thereafter, the solvent-insoluble portion (contents of the mesh sheet) was removed from the toluene and dried at 130°C for approximately two hours. The dried solvent-insoluble portion was weighed (weight after immersion and drying), and the gel fraction (wt%) was calculated using the following formula (a): Gel fraction (wt%) = [(weight after immersion and drying) / (weight of sample)] × 100 (a)

[0020] The thickness of the pressure-sensitive adhesive layer is preferably 1 μm to 300 μm, more preferably 3 μm to 250 μm, even more preferably 3 μm to 100 μm, and particularly preferably 5 μm to 60 μm. In one embodiment, the thickness of the pressure-sensitive adhesive layer is 30 μm or less. By forming a thin pressure-sensitive adhesive layer, it is possible to obtain a pressure-sensitive adhesive sheet that can prevent displacement of the adherend (object to be processed).

[0021] As described above, an acrylic adhesive is used as the adhesive constituting the adhesive layer.

[0022] (base polymer) Examples of the acrylic adhesive include an acrylic adhesive having as a base polymer an acrylic polymer (homopolymer or copolymer) using one or more (meth)acrylic acid alkyl esters as a monomer component. Specific examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, and methyl (meth)acrylate. Examples of (meth)acrylic acid C1-20 alkyl esters include nonyl acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. Among these, (meth)acrylic acid alkyl esters having a linear or branched alkyl group having 4 to 18 carbon atoms can be preferably used. The content of the (meth)acrylic acid alkyl ester structural unit in the acrylic polymer is preferably 70 to 100 parts by weight, more preferably 75 to 99.9 parts by weight, and even more preferably 80 to 99.9 parts by weight, relative to 100 parts by weight of the acrylic polymer.

[0023] The acrylic polymer may contain, as necessary, a structural unit derived from another monomer copolymerizable with the (meth)acrylic acid alkyl ester, for the purpose of modifying cohesive strength, heat resistance, crosslinkability, etc., improving the dimensional stability of the pressure-sensitive adhesive layer, etc. Examples of such monomers include the following monomers. Carboxy group-containing monomers: for example, ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), and crotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and citraconic acid, and their anhydrides (maleic anhydride, itaconic anhydride, etc.); Hydroxyl group-containing monomers: for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether; Amino group-containing monomers: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate; Epoxy group-containing monomers: for example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether; Cyano group-containing monomers: for example, acrylonitrile, methacrylonitrile; Keto group-containing monomers: for example, diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate; Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N-(meth)acryloylmorpholine; Alkoxysilyl group-containing monomers: for example, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane; Isocyanate group-containing monomers: (meth)acryloyl isocyanate, 2-(meth)acryloyloxyethyl isocyanate, m-isopropenyl-α,α-dimethylbenzyl isocyanate. These monomers may be used alone or in combination of two or more.

[0024] In one embodiment, the acrylic polymer contains a structural unit derived from a carboxy group-containing monomer. The content of the structural unit derived from the carboxy group-containing monomer in the acrylic polymer is preferably 1 to 20 parts by weight, more preferably 2 to 15 parts by weight, and even more preferably 3 to 10 parts by weight, per 100 parts by weight of the acrylic polymer. In one embodiment, the acrylic polymer containing a structural unit derived from a carboxy group-containing monomer is used in combination with an epoxy crosslinking agent. By using an acrylic polymer containing a structural unit derived from a carboxy group-containing monomer in combination with an epoxy crosslinking agent, a pressure-sensitive adhesive layer having excellent heat resistance and dimensional stability at high temperatures can be formed. The combined use of the acrylic polymer and an epoxy crosslinking agent is also advantageous in that a pressure-sensitive adhesive layer with little outgassing can be formed. These effects become more pronounced when the content of the structural unit derived from the carboxy group-containing monomer is within the above range.

[0025] In one embodiment, the acrylic polymer contains a structural unit derived from a hydroxyl group-containing monomer. The content of the structural unit derived from the hydroxyl group-containing monomer in the acrylic polymer is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 8 parts by weight, and even more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the acrylic polymer. In one embodiment, the acrylic polymer containing a structural unit derived from a hydroxyl group-containing monomer is used in combination with an isocyanate-based crosslinking agent. By using an acrylic polymer containing a structural unit derived from a hydroxyl group-containing monomer in combination with an isocyanate-based crosslinking agent, a pressure-sensitive adhesive layer can be formed that has excellent heat resistance and dimensional stability at high temperatures. This effect becomes more pronounced when the content of the structural unit derived from the hydroxyl group-containing monomer is within the above range.

[0026] In one embodiment, the acrylic polymer contains a structural unit derived from a polyfunctional (preferably tri- or higher functional, more preferably tri- to hexa-functional) monomer. Examples of such a monomer include trimethylolpropane triacrylate, pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, and dipentaerythritol pentaacrylate. Of these, trimethylolpropane triacrylate is preferred. An acrylic polymer containing the structural unit derived from the polyfunctional monomer has good crosslinkability, excellent heat resistance, and dimensional stability at high temperatures, and can form a pressure-sensitive adhesive layer that is excellent in terms of suppressed outgassing due to heating. The content of the structural unit derived from the polyfunctional monomer in the acrylic polymer is preferably 0.001 to 5 parts by weight, more preferably 0.002 to 3 parts by weight, and even more preferably 0.005 to 1 part by weight, relative to 100 parts by weight of the acrylic polymer.

[0027] The weight-average molecular weight of the acrylic polymer is preferably 600,000 to 1,600,000, more preferably 800,000 to 1,500,000. Within this range, a pressure-sensitive adhesive layer can be formed that has excellent heat resistance, excellent dimensional stability at high temperatures, and suppresses outgassing due to heating. The weight-average molecular weight can be measured by GPC (solvent: THF).

[0028] (additives) The acrylic pressure-sensitive adhesive may contain any appropriate additives as needed, such as crosslinking agents, crosslinking catalysts, tackifiers, plasticizers, pigments, dyes, fillers, antioxidants, conductive materials, antistatic agents, UV absorbers, light stabilizers, release modifiers, softeners, surfactants, flame retardants, and antioxidants.

[0029] Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, as well as urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and amine-based crosslinking agents. Of these, epoxy-based crosslinking agents and isocyanate-based crosslinking agents are preferred.

[0030] Examples of the epoxy crosslinking agent include N,N,N',N'-tetraglycidyl-m-xylylenediamine, diglycidylaniline, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company, Inc., trade name "Tetrad C"), 1,6-hexanediol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolight 1600"), neopentyl glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolight 1500NP"), ethylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolight 1500NP"), and ethylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolight 1500NP"). Licor diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolight 40E"), propylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "Epolight 70P"), polyethylene glycol diglycidyl ether (manufactured by NOF Corporation, trade name "Epiol E-400"), polypropylene glycol diglycidyl ether (manufactured by NOF Corporation, trade name "Epiol P-200"), sorbitol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name "Denacol") EX-611), glycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name "Denacol EX-314"), pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether (manufactured by Nagase ChemteX Corporation, trade name "Denacol EX-512"), sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, adipic acid diglycidyl ester, o-phthalic acid diglycidyl ester, triglycidyl tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule. The content of the epoxy-based crosslinking agent can be set to any appropriate amount depending on the desired adhesive strength, viscoelasticity, dimensional stability, and outgassing properties of the adhesive layer, and is typically 0.01 to 10 parts by weight, and more preferably 0.03 to 7 parts by weight, per 100 parts by weight of the base polymer.

[0031] Specific examples of the isocyanate-based crosslinking agent include lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; aromatic isocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate and xylylene diisocyanate; and isocyanate adducts such as trimethylolpropane / tolylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate L"), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate HL"), and hexamethylene diisocyanate isocyanurate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate HX"). The content of the isocyanate-based crosslinking agent can be set to any appropriate amount depending on the desired adhesive strength, elasticity of the adhesive layer, dimensional stability, outgassing properties, etc., and is typically 0.1 to 20 parts by weight, and more preferably 0.5 to 10 parts by weight, per 100 parts by weight of the base polymer.

[0032] In one embodiment, the acrylic pressure-sensitive adhesive contains a crosslinking catalyst. Addition of a crosslinking catalyst allows for the formation of a pressure-sensitive adhesive layer that exhibits excellent heat resistance, excellent dimensional stability at high temperatures, and suppresses outgassing due to heating. Addition of a crosslinking catalyst is particularly effective when an isocyanate-based crosslinking agent is used. Examples of crosslinking catalysts include metal-based crosslinking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, nursem ferric, butyltin oxide, and dioctyltin dilaurate; and amine-based compounds such as trialkylamine, N,N,N',N'-tetraalkyldiamine, N,N-dialkylaminoalcohol, triethylenediamine, morpholine derivatives, and piperazine derivatives. Among these, dioctyltin dilaurate or triethylenediamine is preferred. Use of these crosslinking catalysts enhances the effects of the present invention. The content of the crosslinking catalyst is preferably 0.01 to 3 parts by weight, and more preferably 0.02 to 1 part by weight, relative to 100 parts by weight of the acrylic polymer.

[0033] C. Base material Examples of the substrate include resin sheets, nonwoven fabrics, paper, metal foils, woven fabrics, rubber sheets, foam sheets, and laminates thereof (particularly laminates containing resin sheets). Examples of resins constituting resin sheets include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polyethylene (PE), polypropylene (PP), ethylene-propylene copolymers, ethylene-vinyl acetate copolymers (EVA), polyamides (nylons), wholly aromatic polyamides (aramids), polyimides (PI), polyvinyl chloride (PVC), polyphenylene sulfide (PPS), fluorine-based resins, and polyether ether ketones (PEEK). Examples of nonwoven fabrics include heat-resistant natural fiber nonwoven fabrics such as Manila hemp nonwoven fabrics; and synthetic resin nonwoven fabrics such as polypropylene resin nonwoven fabrics, polyethylene resin nonwoven fabrics, and ester resin nonwoven fabrics. Examples of metal foils include copper foils, stainless steel foils, and aluminum foils. Examples of paper include Japanese paper and kraft paper. The substrate is preferably made of a resin having excellent heat resistance, such as polyimide.

[0034] The thickness of the substrate is preferably 1000 μm or less, more preferably 1 μm to 1000 μm, still more preferably 1 μm to 500 μm, particularly preferably 3 μm to 300 μm, and most preferably 5 μm to 250 μm.

[0035] The substrate may be subjected to a surface treatment, such as corona treatment, chromic acid treatment, ozone exposure, flame exposure, high-voltage shock exposure, ionizing radiation treatment, or coating with a primer.

[0036] Examples of the organic coating material include those described in Plastic Hard Coat Materials II (CMC Publishing, 2004). Urethane-based polymers are preferred, and polyacrylic urethane, polyester urethane, or their precursors are more preferred. These materials are easy to apply to substrates, and are available in a wide variety of industrially available materials at low cost. The urethane-based polymer is, for example, a polymer formed from a reaction mixture of an isocyanate monomer and an alcoholic hydroxyl group-containing monomer (e.g., a hydroxyl group-containing acrylic compound or a hydroxyl group-containing ester compound). The organic coating material may contain optional additives such as a chain extender such as polyamine, an antioxidant, or an oxidation stabilizer. The thickness of the organic coating layer is not particularly limited, but is preferably about 0.1 μm to 10 μm, more preferably about 0.1 μm to 5 μm, and even more preferably about 0.5 μm to 5 μm.

[0037] D. Manufacturing method of adhesive sheet The pressure-sensitive adhesive sheet of the present invention can be produced by any appropriate method. The pressure-sensitive adhesive sheet of the present invention can be formed, for example, by coating (applying and drying) the acrylic pressure-sensitive adhesive on a predetermined support material to form a pressure-sensitive adhesive layer. The support may be used as the base material for the pressure-sensitive adhesive sheet, and may be peeled off after the pressure-sensitive adhesive layer is formed. As the coating method, various methods can be used, such as bar coater coating, air knife coating, gravure coating, gravure reverse coating, reverse roll coating, lip coating, die coating, dip coating, offset printing, flexographic printing, and screen printing. [Example]

[0038] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Evaluation methods in the examples are as follows. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0039] [evaluation] (1) Adhesive strength PET#25 was laminated to one side of the adhesive layer of the adhesive sheet to obtain a measurement sample (width: 20 mm, length: 140 mm). The other side of the adhesive layer of this measurement sample was laminated to SUS304 by rolling a 2 kg roller back and forth once. The resulting adhesive sheet with adherend was left in an environment of 25°C for 30 minutes, then placed in a tensile tester (Shimadzu Corporation, product name "Shimadzu Autograph AG-120kN"), and the adhesive strength to SUS304 was measured according to a method in accordance with JIS Z 0237:2000 (lamination conditions: 1 roll back and forth with a 2 kg roller, tensile speed: 300 mm / min, peel angle 180°, measurement temperature: 23°C). (2) Weight average molecular weight of base polymer The weight average molecular weight Mw of the base polymer (acrylic polymer) was measured by GPC (gel permeation chromatography (solvent: THF)) using a calibration curve of standard polystyrene. (3) Linear expansion coefficient of the adhesive layer Using "TMA Q400" (manufactured by TA-instrument), the linear expansion coefficient of the adhesive layer at 200 to 210°C and 230 to 240°C was measured in tension mode under the conditions of a nitrogen gas flow rate of 50.0 ml / min and an applied load of 0.0196 N. Specifically, the measurement was performed by the following method. A 50 μm thick adhesive layer was formed using the same adhesive as used in each Example and Comparative Example, and the adhesive layer was laminated to obtain a 200 μm thick sample. The sample was punched out to a size of 4 mm x 30 mm and placed on the probe of a TMA Q400 with an 8 mm gap between each. The dimensional change of the sample was measured while the temperature was increased from 20°C to 300°C at a rate of 10°C / min. From the obtained data, the slope of the dimensional change at 200-210°C and 230-240°C was calculated to obtain the linear expansion coefficient. (4) Storage modulus of adhesive layer Using a dynamic viscoelasticity measuring device (manufactured by TA instruments, trade name "ARES-G2"), the storage modulus G' was measured at a measurement frequency of 1 Hz, a strain of 0.05%, and at 200°C. Specifically, the measurement was performed by the following method. A 50 μm thick adhesive layer was formed using the same adhesive as used in each Example and Comparative Example, and the adhesive layer was laminated to obtain a sample with a thickness of 1 mm or more. The obtained sample was punched out to a diameter of 8 mm and set in the probe of the "ARES-G2." The temperature was raised from -50°C to 260°C at a rate of 5°C / min, and the storage modulus G' at 200°C was measured. (5) 5% weight loss temperature of adhesive layer Using a differential thermal analyzer (manufactured by TA Instruments, product name "Discovery TGA"), the temperature at which the pressure-sensitive adhesive layer loses 5% weight was measured under conditions of a temperature rise rate of 10°C / min, a N2 atmosphere, and a gas flow rate of 25 ml / min. Specifically, the measurement was performed by the following method. Approximately 0.01 g of the adhesive layer sample was placed in the Discovery TGA. The weight loss of the adhesive sheet was measured while the temperature was increased from 20°C to 500°C at a rate of 10°C / min. From the obtained data, the temperature at which the weight loss was 5% was extracted. (6) Gel fraction of adhesive layer Approximately 0.5 g of the adhesive layer was weighed out and used as a sample (weight W1). The sample was wrapped in a porous polytetrafluoroethylene membrane (manufactured by Nitto Denko Corporation, product name "Nitoflon NTF1122", average pore size: 0.2 μm, porosity 75%, thickness 85 μm, weight W2) in a purse shape, and the opening was tied with string (weight W3). The package was immersed in 50 mL of toluene and kept at room temperature (25 ° C) for 7 days to elute only the sol component in the adhesive layer out of the membrane. After that, the package was removed and the toluene adhering to the outer surface was wiped off. The package was dried at 130 ° C for 2 hours, and the weight of the package (W4) was measured. The gel fraction was then calculated by substituting each value into the following formula: Gel fraction (%) = [(W4 - W2 - W3) / W1] x 100 (7) Film shape change rate after oven heating at 240℃ for 5 minutes An adhesive sheet (size: 10mm x 50mm) was suspended in mid-air with no slack, with the distance between its bottom edge and the surface of the table 30mm, and fixed in an oven at 240°C. It was left for 5 minutes and the dimensional change due to heating was measured. If the dimensional change was less than 20mm, the dimensional stability was evaluated as ◯, and if it was 20mm or more, it was evaluated as ×.

[0040] [Production Example 1] Production of acrylic polymer A 50 parts by weight of butyl acrylate, 50 parts by weight of ethyl acrylate, 5 parts by weight of acrylic acid, 0.1 parts by weight of 2-hydroxyethyl acrylate, 0.3 parts by weight of trimethylolpropane triacrylate (TMPTA), and 0.1 parts by weight of benzoyl peroxide as a polymerization initiator were added to toluene, and the mixture was heated to 70°C to obtain a toluene solution of an acrylic polymer (polymer A).

[0041] [Production Example 2] Production of Acrylic Polymer B 95 parts by weight of 2-ethylhexyl acrylate, 5 parts by weight of acrylic acid, and 0.15 parts by weight of benzoyl peroxide as a polymerization initiator were added to ethyl acetate, and the mixture was heated to 70°C to obtain an ethyl acetate solution of an acrylic polymer (polymer B).

[0042] [Production Example 3] Production of Acrylic Polymer C 30 parts by weight of 2-ethylhexyl acrylate, 70 parts by weight of methyl acrylate, 10 parts by weight of acrylic acid, and 0.2 parts by weight of benzoyl peroxide as a polymerization initiator were added to ethyl acetate, and the mixture was heated to 70°C to obtain an ethyl acetate solution of an acrylic polymer (polymer C).

[0043] [Production Example 4] Production of Acrylic Polymer D 30 parts by weight of 2-ethylhexyl acrylate, 70 parts by weight of ethyl acrylate, 4 parts by weight of 2-hydroxyethyl acrylate, 5 parts by weight of methyl methacrylate, and 0.2 parts by weight of benzoyl peroxide as a polymerization initiator were added to toluene, and the mixture was heated to 70°C to obtain a toluene solution of an acrylic polymer (polymer D).

[0044] [Production Example 5] Production of Acrylic Polymer E 100 parts by weight of 2-ethylhexyl acrylate, 2 parts by weight of acrylic acid, 0.01 parts by weight of trimethylolpropane triacrylate, and 0.2 parts by weight of benzoyl peroxide as a polymerization initiator were added to toluene, and the mixture was heated to 70°C to obtain a toluene solution of an acrylic polymer (polymer E).

[0045] [Example 1] An acrylic adhesive was prepared by mixing a toluene solution of polymer A (polymer A: 100 parts by weight) with 5 parts by weight of an epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Company, Inc., trade name "TETRAD-C"). The obtained acrylic adhesive was applied to a polyethylene terephthalate film (thickness: 75 μm) with a silicone release agent-treated surface so that the thickness after solvent evaporation (drying) would be 5 μm, and then dried to form an adhesive layer on the polyethylene terephthalate film. The pressure-sensitive adhesive layer was laminated between rolls to a polyethylene terephthalate film with a silicone release agent-treated surface (manufactured by Toray Industries, Inc., product name "Cerapeel", thickness: 38 μm) to obtain a pressure-sensitive adhesive sheet sandwiched between polyethylene terephthalate films with silicone release agent-treated surfaces. The resulting pressure-sensitive adhesive sheet was subjected to the above evaluations, and the results are shown in Table 1.

[0046] [Examples 2 to 10, Comparative Examples 1 and 2] A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that the polymer (base polymer), crosslinking agent, and crosslinking catalyst shown in Table 1 were used in the amounts shown in Table 1, and the thickness of the pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) was set as shown in Table 1. The pressure-sensitive adhesive sheet obtained was subjected to the above-mentioned evaluations. The results are shown in Table 1. The isocyanate crosslinking agent used in Example 7 etc. is a product name "Coronate L" manufactured by Nippon Polyurethane Co., Ltd. The crosslinking catalyst used in Example 7 is dioctyltin dilaurate (product name "OL-1" manufactured by Tokyo Fi Chemical Co., Ltd.).

[0047] [Table 1]

[0048] As is clear from Table 1, the pressure-sensitive adhesive sheet of the present invention, which has a coefficient of linear expansion (CTE) within a specific range, has excellent dimensional stability at high temperatures. The pressure-sensitive adhesive sheet of the present invention also has the advantage of having a low 5% weight loss temperature, i.e., being less susceptible to thermal decomposition even at high temperatures and producing less outgassing. [Explanation of symbols]

[0049] 10 adhesive layer 20 Base material 100 adhesive sheets

Claims

1. A pressure-sensitive adhesive layer containing an acrylic pressure-sensitive adhesive is provided, the acrylic pressure-sensitive adhesive contains an acrylic polymer, the acrylic polymer contains a structural unit derived from a polyfunctional monomer, The pressure-sensitive adhesive layer has a linear expansion coefficient of 1×10 at 200° C. to 210° C. －５ / K~500×10 －５ / K, the gel fraction of the pressure-sensitive adhesive layer is 93% to 99.99%; Adhesive sheet for temporarily fixing electronic components.

2. The pressure-sensitive adhesive layer has a linear expansion coefficient of 1×10 at 230° C. to 240° C. －５ / K~500×10 －５ 2. The pressure-sensitive adhesive sheet for temporary fixing of electronic components according to claim 1, wherein the viscosity is 100 MPa or less.

3. 3. The pressure-sensitive adhesive sheet for temporarily fixing electronic components according to claim 1, wherein the pressure-sensitive adhesive layer has a storage modulus G' at 200°C of 0.05 MPa or more.

4. 4. The pressure-sensitive adhesive sheet for temporarily fixing electronic components according to claim 1, wherein the pressure-sensitive adhesive layer has a 5% weight loss temperature of 320°C to 400°C.

5. the pressure-sensitive adhesive layer further contains an epoxy-based crosslinking agent, The acrylic polymer contains a structural unit derived from a carboxy group-containing monomer. The pressure-sensitive adhesive sheet for temporarily fixing electronic components according to claim 1 .

6. the pressure-sensitive adhesive layer further contains an isocyanate-based crosslinking agent, The acrylic polymer contains a structural unit derived from a hydroxyl group-containing monomer. The pressure-sensitive adhesive sheet for temporarily fixing electronic components according to claim 1 .

7. The pressure-sensitive adhesive sheet for temporarily fixing electronic components according to claim 1 , wherein the polyfunctional monomer is trimethylolpropane triacrylate.

8. The pressure-sensitive adhesive sheet for temporarily fixing electronic components according to claim 1 , wherein the acrylic pressure-sensitive adhesive further contains a crosslinking catalyst.

9. The pressure-sensitive adhesive sheet for temporarily fixing electronic components according to claim 8 , wherein the crosslinking catalyst is dioctyltin dilaurate or triethylenediamine.

10. The pressure-sensitive adhesive sheet for temporarily fixing electronic components according to any one of claims 1 to 9, wherein the acrylic polymer has a weight average molecular weight Mw of 600,000 to 1,600,000.

11. Further comprising a substrate; The pressure-sensitive adhesive layer is disposed on at least one surface of the substrate. The pressure-sensitive adhesive sheet for temporarily fixing electronic components according to claim 1 .

12. The pressure-sensitive adhesive sheet for temporary fixing of electronic parts according to claim 1 , which is used in a flip-chip bonding step, a resin sealing step, and a rewiring layer forming step of a semiconductor element.

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