Adhesive sheet

Abstract

This invention provides an adhesive sheet that can be used as a temporary fixing material during resin encapsulation of semiconductor chips, preventing defects in the appearance of the encapsulating resin after the adhesive sheet is peeled off. The adhesive sheet of this invention comprises a substrate and an adhesive layer disposed on at least one side of the substrate. The adhesive layer contains an adhesive with an Sp value of 19.5 (J / cm²). 3 ) 1 / 2 ~25 (J / cm) 3 ) 1 / 2 The basic polymer.

Description

Technical Field

[0001] This invention relates to adhesive sheets. Background Technology

[0002] In recent years, during the manufacturing of semiconductor components containing semiconductor chips, resin encapsulation is sometimes performed on the semiconductor chips to prevent scratches, expansion of metal wiring, etc. From an operability perspective, the semiconductor chips are sometimes encapsulated on an adhesive sheet during the resin encapsulation process. For example, to prevent semiconductor chip movement, multiple semiconductor chips are arranged on an adhesive sheet serving as a predetermined temporary fixing material, and resin encapsulation is performed on the adhesive sheet in one step. Then, in a predetermined subsequent process, the adhesive sheet is peeled off from the resin that has encapsulated the semiconductor chips.

[0003] In the process described above, when using existing adhesive sheets, there is a problem that after peeling off the adhesive sheet, an uneven appearance will occur on the encapsulation resin surface that is in contact with the adhesive sheet.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2001-308116

[0007] Patent Document 2: Japanese Patent Application Publication No. 2001-313350

[0008] Patent Document 3: Japanese Patent Application Publication No. 2018-193563 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] The present invention was made to solve the above-mentioned existing problems, and its purpose is to provide an adhesive sheet that can be used as a temporary fixing material when resin encapsulating semiconductor chips, and can prevent poor appearance of the encapsulating resin after the adhesive sheet is peeled off.

[0011] Solution for solving the problem

[0012] The adhesive sheet of the present invention comprises a substrate and an adhesive layer disposed on at least one side of the substrate, the adhesive layer comprising an adhesive having an Sp value of 19.5 (J / cm). 3 ) 1 / 2 ~25 (J / cm) 3 ) 1 / 2 The basic polymer.

[0013] In one embodiment, the adhesive sheet includes the substrate, the adhesive layer disposed on one side of the substrate, and a second adhesive layer disposed on the side of the substrate opposite to the adhesive layer.

[0014] In one embodiment, the adhesive is an acrylic adhesive.

[0015] In one embodiment, the acrylic adhesive as a base polymer comprises a base polymer having an alkyl ester having 6 or fewer carbon atoms as a side chain, and the content of the structural unit having an alkyl ester having 6 or fewer carbon atoms as a side chain is 50% by weight or more relative to all structural units constituting the acrylic polymer.

[0016] In one embodiment, the contact angle of the adhesive layer with respect to 4-tert-butylphenyl glycidyl ether is less than 47°.

[0017] In one embodiment, the adhesion strength of the epoxy resin to the adhesive layer at 23°C when the epoxy resin is cured is preferably 8 N / 20 mm or more.

[0018] In one embodiment, the shear bond strength at 150°C when the adhesive layer is adhered to the silicon chip is 400g or more.

[0019] The effects of the invention

[0020] According to the present invention, an adhesive sheet can be provided that can be used as a temporary fixing material when resin encapsulating a semiconductor chip, and can prevent poor appearance of the encapsulating resin after the adhesive sheet peeling operation. Attached Figure Description

[0021] Figure 1 This is a cross-sectional schematic diagram of an adhesive sheet according to one embodiment of the present invention.

[0022] Figure 2 This is a cross-sectional schematic diagram of an adhesive sheet according to another embodiment of the present invention.

[0023] Figure 3 These are SEM images showing the results of "cross-sectional observation of the encapsulating resin" for the embodiments and comparative examples. Detailed Implementation

[0024] A. Overview of Adhesive Sheets

[0025] Figure 1 This is a cross-sectional schematic diagram of an adhesive sheet according to one embodiment of the present invention. The adhesive sheet 100 includes a substrate 10 and an adhesive layer (first adhesive layer) 20 disposed on at least one side of the substrate 10.

[0026] The adhesive sheet of the present invention can be suitably used as a temporary fixing material during resin encapsulation of semiconductor chips. More specifically, the adhesive sheet of the present invention can be used as a temporary fixing material for semiconductor chips during resin encapsulation, which involves arranging semiconductor chips on an adhesive layer of the adhesive sheet, covering the semiconductor chips with resin (typically an epoxy resin), and curing the encapsulation resin. After resin encapsulation of the semiconductor chip, the adhesive sheet can be peeled off from the structure composed of the encapsulation resin and the semiconductor chip during predetermined subsequent processes (e.g., back-side grinding of the encapsulation resin, patterning, bumping, chip forming (cutting)).

[0027] The aforementioned adhesive layer contains an adhesive. This adhesive contains an Sp value of 19.5 (J / cm²). 3 ) 1 / 2 ~25 (J / cm) 3 ) 1 / 2 The basic polymer. In this invention, by using a basic polymer with a Sp value in this range, an adhesive layer with high affinity to the encapsulating resin can be formed. When an adhesive sheet having this adhesive layer is bonded to the encapsulating resin and supplied to the resin encapsulation process, the heating and pressurization during this process appropriately forms a mixed layer containing both adhesive layer components and encapsulating resin components between the encapsulating resin and the adhesive layer of the adhesive sheet. As a result, after the adhesive sheet is peeled off from the encapsulating resin, poor appearance (flow marks) on the surface of the encapsulating resin where the adhesive sheet is bonded can be prevented. In one embodiment, during the peeling operation of the adhesive sheet, the adhesive layer of the adhesive sheet is peeled off from the substrate and remains in the encapsulating resin as a result of the formation of the mixed layer. As a result, the effect of preventing flow marks becomes more significant. Furthermore, the adhesion of wiring formed on a structure containing a semiconductor chip can be improved. Moreover, after peeling, the step difference between the surface of the encapsulating resin and the semiconductor chip can also be reduced.

[0028] To date, the primary cause of flow marks is believed to be the uneven thickness of the mixed layer formed by the mixing of the low-molecular-weight components of the encapsulating resin and the adhesive components of the adhesive layer. As adhesive sheets for temporary fixation of resin encapsulation, adhesive sheets with adhesive layers having low affinity to the encapsulating resin (e.g., adhesive layers containing adhesives with low sp values) are being researched and developed. On the other hand, the present invention is based on a concept completely different from existing adhesive sheets, characterized by the prevention of flow marks by forming an adhesive layer with high affinity to the encapsulating resin.

[0029] Figure 2This is a cross-sectional schematic diagram of an adhesive sheet according to another embodiment of the present invention. The adhesive sheet 200 further includes a second adhesive layer 30 on the side of the substrate 10 opposite to the adhesive layer 20. That is, the adhesive sheet 200 sequentially includes the adhesive layer 20, the substrate 10, and the second adhesive layer 30. By including the second adhesive layer 30, when resin encapsulating on a pedestal, the adhesive sheet 200 can be fixedly positioned by attaching the second adhesive layer 30 side to the pedestal.

[0030] In one embodiment, the second adhesive layer comprises thermally expandable microspheres. These microspheres can expand at a specified temperature. This adhesive layer containing thermally expandable microspheres expands by heating it above the specified temperature, creating unevenness on the adhesive surface (i.e., the surface of the second adhesive layer), thereby reducing or eliminating the adhesive force. If a second adhesive layer containing thermally expandable microspheres is formed, the desired adhesion is exhibited when the adhesive sheet is fixed (e.g., fixed to a pedestal), and good peelability is exhibited when the adhesive sheet is peeled off (e.g., peeled from the pedestal) by heating, thereby reducing or eliminating the adhesive force.

[0031] The adhesive sheet of the present invention has an adhesive strength of 0.05 N / 20 mm to 1 N / 20 mm at 23°C when the adhesive layer is adhered to polyethylene terephthalate, more preferably 0.1 N / 20 mm to 10 N / 20 mm, further preferably 0.1 N / 20 mm to 5 N / 20 mm, particularly preferably 0.2 N / 20 mm to 2 N / 20 mm, and most preferably 0.2 N / 20 mm to 1 N / 20 mm. Within this range, an adhesive sheet that can suitably fix the adhered object (e.g., a semiconductor chip) and leaves minimal adhesive residue upon peeling can be obtained. It should be noted that, in this specification, "adhesive force at 23°C when the adhesive layer is bonded to polyethylene terephthalate" refers to the adhesive force measured by bonding an adhesive layer (width 20mm × length 100mm) to a polyethylene terephthalate film (thickness 25μm) (bonding conditions: 2kg roller passes back and forth once), placing the sample at an ambient temperature of 23°C for 30 minutes, and then subjecting the sample to a tensile test (peeling speed: 300mm / min, peeling angle 180°).

[0032] The adhesive sheet of the present invention, when the epoxy resin is cured on the adhesive layer, preferably has an adhesion force of 8 N / 20 mm or more to the epoxy resin at 23°C, more preferably 8 N / 20 mm to 20 N / 20 mm, and even more preferably 8 N / 20 mm to 15 N / 20 mm. "Adhesion force on the epoxy resin at 23°C when the epoxy resin is cured on the adhesive layer" is an indicator of the adhesion between the adhesive sheet and the encapsulating resin. If the adhesion force is within the above range, an adhesive sheet suitable as a temporary fixing material for resin encapsulation of semiconductor chips can be obtained. It should be noted that, in this specification, "adhesion force on the epoxy resin at 23°C when the epoxy resin is cured on the adhesive layer" refers to the peeling force when the epoxy resin is peeled off from the adhesive layer after applying the epoxy resin (e.g., manufactured by SUMITOMO BAKELITE Co., Ltd., trade name "G730") to the adhesive layer and then curing the epoxy resin. The adhesive force (peel force) was determined by subjecting the above-mentioned sample with a width of 20 mm and a length of 100 mm to a tensile test (peel speed: 300 mm / min, peel angle 180°).

[0033] The shear bond strength of the adhesive sheet of the present invention at 150°C when the adhesive layer is bonded to a silicon chip is preferably 400g or more, more preferably 400g to 2000g, and even more preferably 700g to 1500g. Within this range, the adhesive has high cohesive strength and suitable adhesive force even at high temperatures (e.g., heating processes used to cure the encapsulating resin), and can prevent displacement of the adhered object (e.g., a semiconductor chip) disposed on the adhesive sheet. Furthermore, it can prevent the formation of gaps (gap between the adhesive sheet and the encapsulating resin) that could be penetrated by the encapsulating resin. The shear bond strength can be measured as follows: After the mirror surface of the silicon chip (size: 5mm × 5mm) is perpendicularly bonded to the adhesive layer without touching the chip corners, it is heated at 130°C for 30 minutes to ensure close adhesion between the silicon chip and the adhesive surface. Then, an external force is applied at 150°C with a shear rate of 500 μm / sec in a direction horizontal to the chip, and the maximum destructive load is read from the obtained load-displacement curve, thereby determining the shear bond strength.

[0034] The thickness of the adhesive sheet of the present invention is preferably 3μm to 300μm, more preferably 20μm to 200μm, and even more preferably 50μm to 150μm.

[0035] B. Adhesive layer

[0036] The thickness of the adhesive layer is preferably 1 μm to 300 μm, more preferably 2 μm to 300 μm, even more preferably 2 μm to 200 μm, even more preferably 3 μm to 100 μm, even more preferably 4 μm to 80 μm, and particularly preferably 5 μm to 50 μm. Within this range, an adhesive layer with a flat surface is formed, resulting in an adhesive sheet that is less prone to flow marks.

[0037] The contact angle of the adhesive layer with respect to 4-tert-butylphenyl glycidyl ether is preferably 47° or less, more preferably 25° to 47°, and even more preferably 28° to 45°. Within this range, an adhesive layer with high affinity to the encapsulating resin can be formed.

[0038] The elastic modulus of the adhesive layer at 25°C based on nanoindentation is preferably less than 100 MPa, more preferably 0.1 MPa to 50 MPa, and even more preferably 0.1 MPa to 10 MPa. Within this range, an adhesive sheet with appropriate adhesive strength can be obtained. The elastic modulus based on nanoindentation refers to the elastic modulus obtained by continuously measuring the load on the indenter and the indentation depth when the indenter is pressed into the sample during loading and unloading, and calculating the load-indentation depth curve. In this specification, the elastic modulus based on nanoindentation refers to the elastic modulus measured under the following conditions: load: 1 mN, loading / unloading speed: 0.1 mN / s, holding time: 1 s, and as described above.

[0039] The tensile modulus of elasticity of the adhesive layer at 25°C is preferably less than 100 MPa, more preferably 0.1 MPa to 50 MPa, and even more preferably 0.1 MPa to 10 MPa. Within this range, an adhesive sheet with appropriate adhesive strength can be obtained. It should be noted that the tensile modulus of elasticity can be measured according to JIS K 7161:2008.

[0040] The probe adhesion value of the above-mentioned adhesive layer is preferably... The above is preferred. The above is further optimized. The above. If this range is met, it can prevent the position of the object (e.g., a semiconductor chip) mounted on the adhesive sheet from shifting. The conditions for determining the probe adhesion value are: probe processing speed: 30 mm / min, test speed: 30 mm / min, contact load: 100 gf, contact holding time: 1 second, probe area: 5 mm φSUS.

[0041] <Adhesive>

[0042] As the adhesive constituting the adhesive layer described above, any suitable adhesive can be used as long as the effects of the present invention are achieved. Examples of such adhesives include acrylic adhesives, rubber adhesives, and silicone adhesives. Among these, acrylic adhesives are preferred. Furthermore, active energy radiation-cured adhesives can be used as the adhesive. The above-mentioned adhesives contain a base polymer with an sp value within the above-mentioned range. It should be noted that the base polymer refers to the polymer that constitutes the main reason for the adhesive's adhesive properties.

[0043] As mentioned above, the Sp value of the base polymer is 19.5 (J / cm). 3 ) 1 / 2 ~25 (J / cm) 3 ) 1 / 2 The preferred Sp value of the base polymer is 20 (J / cm). 3 ) 1 / 2 ~24 (J / cm) 3 ) 1 / 2 More preferably, it is 20.5 (J / cm). 3 ) 1 / 2 ~23.5 (J / cm) 3 ) 1 / 2 If the range is such, the effects of the present invention become significant. The Sp value of the base polymer can be calculated using Fedors' method (Hideki Yamamoto, *Basic Applications and Calculation Methods of Sp Value*, published by Information Corporation of Japan, April 3, 2006, pp. 66-67). Specifically, the Sp value is based on the evaporation energy Δe (cal) of each atom or group forming the polymer at 25°C and the molar volume ΔV (cm³) of each atom or group forming the polymer at 25°C. 3 ), which can be calculated using the following formula.

[0044] Sp value = (ΣΔe / ΣΔv) 1 / 2

[0045] When the polymer is a copolymer, its SP value is calculated as follows: calculate the SP value of the homopolymer of each structural unit constituting the copolymer, multiply these SP values ​​by the mole fraction of each structural unit and sum them up to obtain the SP value.

[0046] (Acrylic adhesives)

[0047] Examples of acrylic adhesives include acrylic adhesives that use an acrylic polymer (homopolymer or copolymer) with one or more monomers of (meth)acrylate as a monomer component as a base polymer.

[0048] Specific examples of the aforementioned alkyl methacrylates include: methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecanyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, octadecyl methacrylate, nonadecanyl methacrylate, eicosyl methacrylate, and other C1-20 alkyl methacrylates. Among them, alkyl (meth)acrylates having a straight-chain or branched alkyl group having 1 to 16 carbon atoms (more preferably 1 to 12, particularly preferably 1 to 6) are preferred.

[0049] The aforementioned acrylic polymer preferably has alkyl esters with 6 or fewer carbon atoms as side chains, more preferably alkyl esters with 4 or fewer carbon atoms, and even more preferably alkyl esters with 2 or fewer carbon atoms. Using acrylic polymers with short side chains allows for the formation of an adhesive layer with high affinity for the encapsulation material. In the aforementioned acrylic polymer, the percentage of structural units having alkyl esters with 6 or fewer carbon atoms (preferably 4 or fewer, more preferably 2 or fewer) as side chains relative to all structural units constituting the acrylic polymer is preferably 50% by weight or more, more preferably 60% by weight or more, even more preferably 60% to 100% by weight, particularly preferably 60% to 90% by weight, and most preferably 60% to 80% by weight. Within this range, an adhesive layer with high affinity for the encapsulation material can be formed.

[0050] The aforementioned acrylic adhesive may comprise a variety of acrylic polymers. Regarding the proportion of the acrylic polymer containing an alkyl ester with 6 or fewer carbon atoms in its side chain (preferably 4 or fewer, more preferably 2 or fewer), relative to 100 parts by weight of the total acrylic polymer, it is preferably 30 to 100 parts by weight, more preferably 70 to 100 parts by weight, and even more preferably 90 to 100 parts by weight. In one embodiment, the proportion of the acrylic polymer containing an alkyl ester with 6 or fewer carbon atoms in its side chain is 100 parts by weight relative to 100 parts by weight of the total acrylic polymer.

[0051] Regarding the aforementioned acrylic polymers, to improve cohesion, heat resistance, and crosslinking properties, units corresponding to other monomeric components that can copolymerize with the aforementioned alkyl methacrylates can be included as needed. Examples of such monomeric components include: acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and other carboxyl-containing monomers; maleic anhydride, itaconic anhydride, and other anhydride monomers; hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxyhexyl methacrylate, hydroxyoctyl methacrylate, hydroxydecyl methacrylate, hydroxylauryl methacrylate, methyl methacrylate (4-hydroxymethylcyclohexyl) methacrylate, and other hydroxyl-containing monomers; styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, and (meth)acrylamide propanesulfonic acid. 500-700-4 ... Maleimide monomers such as N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itconimide monomers such as N-methylitconimide, N-ethylitconimide, N-butylitconimide, N-octylitconimide, N-2-ethylhexylitconimide, N-cyclohexylitconimide, and N-laurylitconimide; succinimide monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxohexamethylenesuccinimide, and N-(meth)acryloyl-8-oxooctamethylenesuccinimide; vinyl acetate, vinyl propionate, and N-ethyl... Vinyl monomers such as alkenylpyrrolidone, methyl vinylpyrrolidone, vinylpyridine, vinyl piperidinone, vinyl pyrimidine, vinyl piperazine, vinyl pyrazine, vinyl pyrrole, vinyl imidazole, vinyl oxazole, vinyl morpholine, N-vinylcarboxylic amides, styrene, α-methylstyrene, and N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy-containing acrylic monomers such as glycidyl (meth)acrylate; and diol-based acrylate monomers such as polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate.Acrylate monomers containing heterocyclic rings, halogen atoms, silicon atoms, etc., such as tetrahydrofurfuryl methacrylate, fluorinated methacrylates, and organosilicon methacrylates; polyfunctional monomers such as hexanediol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol dimethacrylate, pentaerythritol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexamethacrylate, epoxy acrylates, polyester acrylates, and urethane acrylates; olefin monomers such as isoprene, butadiene, and isobutylene; and vinyl ether monomers such as vinyl ethers. These monomer components can be used alone or in combination of two or more. Among the above, carboxyl-containing monomers (particularly acrylic acid) or hydroxyl-containing monomers (particularly hydroxyethyl methacrylate) are more preferred. Regarding the content of structural units derived from carboxyl-containing monomers, relative to all structural units constituting the acrylic polymer, it is preferably 40% by weight or less, more preferably 0.1% by weight to 10% by weight, even more preferably 0.5% by weight to 5% by weight, and particularly preferably 1% by weight to 4% by weight. Furthermore, regarding the content of structural units derived from hydroxyl-containing monomers, relative to all structural units constituting the acrylic polymer, it is preferably 0.09% by weight to 40% by weight, more preferably 0.1% by weight to 20% by weight, even more preferably 0.5% by weight to 10% by weight, and particularly preferably 1% by weight to 7% by weight.

[0052] The aforementioned acrylic adhesives may contain any appropriate additives as needed. Examples of such additives include: crosslinking agents, tackifiers, plasticizers (e.g., trimellitate plasticizers, pyromellitic ester plasticizers, etc.), pigments, dyes, fillers, antioxidants, conductive materials, antistatic agents, UV absorbers, light stabilizers, peel modifiers, softeners, surfactants, flame retardants, antioxidants, etc.

[0053] Crosslinking agents included in the aforementioned acrylic adhesives include, for example, isocyanate-based, epoxy-based, melamine-based, and peroxide-based crosslinking agents, as well as urea-based, metal alkoxide-based, metal chelate-based, metal salt-based, carbodiimide-based, oxazoline-based, aziridine-based, and amine-based crosslinking agents. Among these, isocyanate-based or epoxy-based crosslinking agents are preferred.

[0054] Specific examples of the isocyanate-based crosslinking agents included in the aforementioned acrylic adhesives 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-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and phenylenediamine diisocyanate; isocyanate adducts such as trimethylolpropane / toluene 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 isocyanurate derivatives of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "CORONATE HX"); and so on. The content of the isocyanate-based crosslinking agent can be set to any appropriate amount according to the desired adhesive strength, typically 0.1 to 20 parts by weight, and more preferably 0.5 to 10 parts by weight, relative to 100 parts by weight of the base polymer.

[0055] Examples of epoxy crosslinking agents included in the aforementioned acrylic adhesives include: N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidyl-aniline, 1,3-bis(N,N-glycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd., 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 40E"), propylene glycol diglycidyl ether (manufactured by Kyoeisha Chemical Co., Ltd., trade name "EPOLIGHT 70P"), and polyethylene glycol diglycidyl ether (manufactured by Nippon Yushi Co., Ltd., trade name "EPIOL"). E-400”), polypropylene glycol diglycidyl ether (manufactured by Nippon Yushi Co., Ltd., 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 anhydride polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate, diglycidyl phthalate, triglycidyl tris(2-hydroxyethyl) isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, epoxy resins with two or more epoxy groups in the molecule, etc. The content of the epoxy crosslinking agent can be set to any appropriate amount according to the desired adhesive strength, typically 0.01 parts by weight to 10 parts by weight, and more preferably 0.03 parts by weight to 5 parts by weight, relative to 100 parts by weight of the base polymer.

[0056] As the tackifier included in the above-mentioned acrylic adhesive, any suitable tackifier can be used. For example, a tackifying resin can be used as the tackifier. Specific examples of such tackifying resins include: rosin-based tackifying resins (e.g., unmodified rosin, modified rosin, rosin phenol-based resins, rosin ester-based resins, etc.), terpene-based tackifying resins (e.g., terpene-based resins, terpene phenol-based resins, styrene-modified terpene-based resins, aromatic-modified terpene-based resins, hydrogenated terpene-based resins), hydrocarbon-based tackifying resins (e.g., aliphatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aromatic hydrocarbon resins (e.g., styrene-based resins, xylene-based resins, etc.), aliphatic-aromatic petroleum resins, aliphatic-alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, coumarone-indene-based resins, etc.), phenol-based tackifying resins (e.g., alkylphenol-based resins, xylene-formaldehyde-based resins, methylphenol-formaldehyde resins, phenolic varnishes, etc.), ketone-based tackifying resins, polyamide-based tackifying resins, epoxy-based tackifying resins, and elastic system tackifying resins, etc. Among these, rosin-based tackifying resins, terpene-based tackifying resins, or hydrocarbon-based tackifying resins (such as styrene-based resins) are preferred. The tackifier can be used alone or in combination of two or more. The amount of the tackifier added relative to 100 parts by weight of the base polymer is preferably 5 to 100 parts by weight, more preferably 10 to 50 parts by weight.

[0057] Preferably, a resin with a high softening point or glass transition temperature (Tg) is used as the aforementioned tackifying resin. If a resin with a high softening point or glass transition temperature (Tg) is used, an adhesive layer exhibiting high adhesion can be formed even under high-temperature environments (e.g., high-temperature environments during semiconductor chip packaging processes). The softening point of the tackifier is preferably 100°C to 180°C, more preferably 110°C to 180°C, and even more preferably 120°C to 180°C. The glass transition temperature (Tg) of the tackifier is preferably 100°C to 180°C, more preferably 110°C to 180°C, and even more preferably 120°C to 180°C.

[0058] The aforementioned acrylic adhesives may further include reaction aids. By adding reaction aids, it is expected that the anti-residue effect resulting from the cohesive breakdown of the adhesive during peeling of the resin-encapsulated adhesive sheet can be further improved. As reaction aids, when using isocyanate-based crosslinking agents, examples include tin-based organic compounds, titanium-based organic compounds, iron-based organic compounds, and amine (TEDA, etc.)-based organic compounds. Specific examples of tin-based organic compounds include "OL-1" manufactured by Tokyo Fine Chemical Co., Ltd., and "Tetraethylenediamine" manufactured by Tosoh Corporation. When using epoxy-based crosslinking agents, examples include imidazole-based and phosphorus-based organic compounds. Regarding the content ratio of the reaction aid, it is preferably 0.001 parts by weight to 0.5 parts by weight relative to 100 parts by weight of the base polymer, more preferably 0.005 parts by weight to 0.1 parts by weight, and even more preferably 0.01 parts by weight to 0.07 parts by weight.

[0059] (Rubber-based adhesives)

[0060] As the aforementioned rubber-based adhesive, any suitable adhesive can be used as long as the effects of the present invention can be obtained. For example, rubber-based adhesives using the following rubbers as base polymers are preferred: natural rubber; synthetic rubbers such as polyisoprene rubber, butadiene rubber, styrene-butadiene (SB) rubber, styrene-isoprene (SI) rubber, styrene-isoprene-styrene block copolymer (SIS) rubber, styrene-butadiene-styrene block copolymer (SBS) rubber, styrene-ethylene-butene-styrene block copolymer (SEBS) rubber, styrene-ethylene-propylene-styrene block copolymer (SEPS) rubber, styrene-ethylene-propylene block copolymer (SEP) rubber, recycled rubber, butyl rubber, polyisobutylene rubber, or modified forms thereof; etc. These base polymers (rubbers) have low sp values, and if such base polymers are used, an adhesive layer with low affinity for the encapsulating material can be formed.

[0061] Polyisobutylene rubber, polyisoprene rubber, or butyl rubber are particularly preferred as the base polymers constituting the aforementioned rubber-based adhesives. Using these rubbers allows for the formation of an adhesive layer that exhibits excellent semiconductor chip retention and peelability at room temperature. Furthermore, an adhesive layer with low affinity for encapsulation materials can be formed.

[0062] As the base polymer constituting the above-mentioned rubber-based adhesive, styrene-ethylene-propylene block copolymer (SEP) rubber, styrene-ethylene-butene-styrene block copolymer (SEBS) rubber, styrene-isoprene-styrene block copolymer (SIS) rubber, styrene-butadiene-styrene block copolymer (SBS) rubber, and propylene rubber may also be preferably used. Using these rubbers, an adhesive layer exhibiting high adhesion can be formed even under high-temperature environments (e.g., high-temperature environments during semiconductor chip packaging). In the base polymer (rubber) having styrene-derived structural units, the content of styrene-derived structural units is preferably 15% by weight or more relative to all structural units in the base polymer.

[0063] The aforementioned rubber-based adhesives may contain any appropriate additives as needed. Examples of such additives include: crosslinking agents, vulcanizing agents, tackifiers, plasticizers, pigments, dyes, fillers, antioxidants, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, peel modifiers, softeners, surfactants, flame retardants, antioxidants, etc.

[0064] As the tackifier included in the aforementioned rubber-based adhesive, any suitable tackifier can be used. For example, a tackifying resin can be used as the tackifier. Specific examples of such tackifying resins include rosin-based tackifying resins, rosin derivative resins, petroleum-based resins, terpene-based resins, ketone-based resins, etc. The amount of the tackifier added relative to 100 parts by weight of the base polymer is preferably 5 to 100 parts by weight, more preferably 10 to 50 parts by weight.

[0065] Examples of rosin-based resins included in the aforementioned rubber-based adhesives include: rosin resin, wood rosin, tall oil rosin, etc. As a rosin-based resin, stabilized rosin obtained by disproportionation or hydrogenation of any suitable rosin can be used. Furthermore, as a rosin-based resin, polymeric rosin (typically a dimer) of any suitable rosin, or modified rosin obtained by modifying any suitable rosin (e.g., based on modification with unsaturated acids) can be used.

[0066] Examples of rosin derivative resins included in the aforementioned rubber-based adhesives include: esterified rosin resins, phenol-modified rosin resins, and esterified rosin resins modified with phenol.

[0067] Examples of petroleum-based resins included in the aforementioned rubber-based adhesives include: aliphatic petroleum resins, aromatic petroleum resins, copolymer petroleum resins, alicyclic petroleum resins, and their hydrides.

[0068] Examples of terpene resins included in the aforementioned rubber-based adhesives include α-pinene resin, β-pinene resin, aromatic modified terpene resin, and terpene phenol resin.

[0069] Examples of ketone resins included in the aforementioned rubber-based adhesives include ketone resins obtained by condensing ketones (e.g., aliphatic ketones, alicyclic ketones) with formaldehyde.

[0070] Examples of crosslinking agents included in the aforementioned rubber-based adhesives include isocyanate-based crosslinking agents. Examples of vulcanizing agents included in the aforementioned rubber-based adhesives include thiuram-based vulcanizing agents, quinone-based vulcanizing agents, and p-benzoquinone dioxime-based vulcanizing agents. By including crosslinking agents and / or vulcanizing agents in the rubber-based adhesive, an adhesive layer with high cohesiveness and low residue can be formed. The total content of crosslinking agents and vulcanizing agents is typically 0.1 to 20 parts by weight, more preferably 0.1 to 10 parts by weight, relative to 100 parts by weight of the base polymer.

[0071] In one embodiment, a rubber-based adhesive (Rub1) comprising the aforementioned base polymer (rubber), a hydroxyl-containing polyolefin, and a crosslinking agent a that reacts with the hydroxyl groups of the hydroxyl-containing polyolefin can be used. In this rubber-based adhesive, the base polymer does not directly undergo crosslinking, but rather entanglement occurs between the base polymer and the already crosslinked hydroxyl-containing polyolefin, resulting in so-called pseudo-crosslinking. As a result, an adhesive layer with high cohesiveness and low residue can be formed. The aforementioned synthetic rubber is preferably used as the base polymer (rubber) in this embodiment. Furthermore, an isocyanate-based crosslinking agent is preferably used as the crosslinking agent in this embodiment.

[0072] Regarding the amount of the hydroxyl-containing polyolefin, it is preferably 0.5 parts by weight or more, more preferably 1.0 parts by weight or more, relative to 100 parts by weight of the total of the base polymer (rubber), the hydroxyl-containing polyolefin, and the crosslinking agent a. If it is within this range, an adhesive layer with high cohesiveness can be formed. Furthermore, when the adhesive sheet has a substrate layer, the adhesion (anchoring force) between the substrate layer and the adhesive layer can be improved. That is, if the amount of the hydroxyl-containing polyolefin is within the above range, an adhesive sheet with less residual adhesive can be obtained.

[0073] Regarding the mixing amount of the aforementioned crosslinking agent a, it is preferably 0.5 parts by weight or more, more preferably 1.0 parts by weight or more, relative to 100 parts by weight of the total of the aforementioned base polymer (rubber), the aforementioned hydroxyl-containing polyolefin, and the aforementioned crosslinking agent a. If it is within this range, an adhesive layer with high cohesiveness can be formed. Furthermore, when the adhesive sheet has a substrate layer, the adhesion (anchoring force) between the substrate layer and the adhesive layer can be improved. That is, if the mixing amount of the aforementioned crosslinking agent a is within the above range, an adhesive sheet with less adhesive residue can be obtained.

[0074] As the aforementioned hydroxyl-containing polyolefin, a resin with excellent compatibility with the aforementioned synthetic rubber is preferred. Examples of hydroxyl-containing polyolefins include: polyethylene-based polyols, polypropylene-based polyols, polybutadiene polyols, hydrogenated polybutadiene polyols, polyisoprene polyols, and hydrogenated polyisoprene polyols. Among these, from the perspective of compatibility with the aforementioned synthetic rubber, hydrogenated polyisoprene polyols, polyisoprene polyols, and polybutadiene polyols are preferred.

[0075] The number-average molecular weight (Mn) of the above-mentioned hydroxyl-containing polyolefin is preferably 500 to 500,000, more preferably 1,000 to 200,000, and even more preferably 1,200 to 150,000. The number-average molecular weight can be determined according to ASTM D2503.

[0076] The hydroxyl value (mgKOH / g) of the above-mentioned hydroxyl-containing polyolefin is preferably 5 to 95, more preferably 10 to 80. The hydroxyl value can be determined according to JIS K1557:1970.

[0077] (Silicone-based adhesives)

[0078] As the aforementioned silicone-based adhesive, any suitable adhesive can be used as long as the effects of the present invention can be obtained. For example, silicone-based adhesives using silicone rubber or silicone resin containing organopolysiloxanes as the base polymer are preferred. As the base polymer constituting the silicone-based adhesive, a base polymer obtained by crosslinking the aforementioned silicone rubber or silicone resin can be used. It should be noted that, in this specification, "silicone rubber" refers to a polymer (e.g., viscosity 1000 Pa·s) obtained by linearly linking diorganosiloxanes (D units) as the main component, and "silicone resin" refers to a polymer composed of triorganosilhemioxanes (M units) and silicates (Q units) as the main components (Materials Design and Functional Assignment of Adhesives (Films and Tapes), Technical Information Association, September 30, 2009).

[0079] Examples of silicone rubbers mentioned above include organopolysiloxanes containing dimethylsiloxane as a structural unit. Functional groups (e.g., vinyl groups) may be incorporated into the organopolysiloxane as needed. The weight-average molecular weight of the organopolysiloxane is preferably 100,000 to 1,000,000, more preferably 150,000 to 500,000. The weight-average molecular weight can be determined using GPC (solvent: THF).

[0080] Examples of the aforementioned organosilicon resins include those containing R3SiO2. 1 / 2Structural unit, SiO2 structural unit, RSiO 3 / 2 The organopolysiloxane (R is a monovalent hydrocarbon group or hydroxyl group) of at least one of the structural units, including the structural unit and the R2SiO structural unit.

[0081] The aforementioned silicone rubber and silicone resin can be used together. The weight ratio (rubber:resin) of silicone rubber to silicone resin in the silicone adhesive is preferably 100:0 to 100:220, more preferably 100:0 to 100:180, and even more preferably 100:10 to 100:100. Silicone rubber and silicone resin can be included in the silicone adhesive as a simple mixture, or they can be included in the silicone adhesive in a partially condensed form. The rubber:resin ratio can also be adjusted according to the application... 29 The ratio of Q units (resin) to D units (rubber) obtained by Si-NMR determination of the composition of organosilicon adhesives is used to determine the composition.

[0082] The aforementioned silicone-based adhesives may contain any appropriate additives as needed. Examples of such additives include: crosslinking agents, vulcanizing agents, tackifiers, plasticizers, pigments, dyes, fillers, antioxidants, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, peel modifiers, softeners, surfactants, flame retardants, antioxidants, etc.

[0083] Preferably, the aforementioned silicone-based adhesive includes a crosslinking agent. Examples of such crosslinking agents include siloxane-based crosslinking agents and peroxide-based crosslinking agents. As a peroxide-based crosslinking agent, any suitable crosslinking agent can be used. Examples of such peroxide-based crosslinking agents include benzoyl peroxide, tert-butyl peroxide, and dicumyl peroxide. Examples of such siloxane-based crosslinking agents include polyorganohydrosiloxanes. The polyorganohydrosiloxane preferably has two or more hydrogen atoms bonded to silicon atoms. Furthermore, the polyorganohydrosiloxane preferably has alkyl, phenyl, or haloalkyl groups as functional groups bonded to silicon atoms.

[0084] (Active energy radiation curing adhesive)

[0085] As the aforementioned adhesive, an active energy radiation-cured adhesive that can be cured by irradiation with active energy rays (high elastic modulus) can be used. If an active energy radiation-cured adhesive is used, an adhesive sheet can be obtained that exhibits low elasticity, high flexibility, and excellent workability during bonding, and whose adhesive strength can be reduced by irradiation with active energy rays in situations requiring peeling. Examples of active energy rays include: gamma rays, ultraviolet rays, visible light, infrared rays (thermal rays), radio frequency waves, alpha rays, beta rays, electron beams, plasma streams, ionizing rays, particle beams, etc. It should be noted that in this specification, when the term "adhesive layer" is simply mentioned, it refers to the adhesive layer before the adhesive is cured to reduce adhesive strength.

[0086] Examples of resin materials constituting the aforementioned active energy ray-curable adhesives include: ultraviolet curing systems (Kiyoshi Kato, published by the Comprehensive Technical Center, (1989)), light curing technology (edited by the Technical Information Association, (2000)), Japanese Patent Application Publication No. 2003-292916, and Japanese Patent No. 4151850. More specifically, examples include: resin materials (R1) containing a polymer constituting a masterbatch and an active energy ray-reactive compound (monomer or oligomer), and resin materials (R2) containing an active energy ray-reactive polymer.

[0087] Examples of polymers constituting the masterbatch include: natural rubber, polyisobutylene rubber, styrene-butadiene rubber, styrene-isoprene-styrene block copolymer rubber, reclaimed rubber, butyl rubber, polyisobutylene rubber, nitrile rubber (NBR), and other rubber-based polymers; silicone polymers; and acrylic polymers. These polymers can be used alone or in combination of two or more. From the perspective of affinity with the encapsulation material, it is preferable to use the polymers exemplified as the base polymers for the acrylic adhesives, rubber adhesives, or silicone adhesives described above as constituting the masterbatch.

[0088] Examples of photoreactive compounds that are reactive to the aforementioned energy rays include: monomers or oligomers with photoreactive functional groups containing carbon-carbon multiple bonds, such as acryloyl, methacryloyl, vinyl, allyl, and ethynyl groups. Specific examples of such photoreactive monomers or oligomers include: compounds containing (meth)acryloyl groups, such as trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and polyethylene glycol di(meth)acrylate; 2-5 polymers of such (meth)acryloyl-containing compounds; and so on.

[0089] Furthermore, monomers such as epoxide butadiene, glycidyl methacrylate, acrylamide, and vinylsiloxane, or oligomers composed of these monomers, can be used as the aforementioned reactive compounds. Resin materials (R1) containing these compounds can be cured by high-energy rays such as ultraviolet light and electron beams.

[0090] Furthermore, as the aforementioned reactive compounds to active energy rays, mixtures of organic salts such as onium salts and compounds having multiple heterocycles within their molecules can be used. This mixture can be irradiated with active energy rays (e.g., ultraviolet light, electron beams) to cause the organic salts to break and generate ions, thereby initiating a ring-opening reaction of the heterocycles and forming a three-dimensional network structure. Examples of such organic salts include iodonium salts, phosphonium salts, antimonyonium salts, sulfonium salts, and borates. Examples of heterocycles in compounds having multiple heterocycles within their molecules include oxetane, oxetane, oxetane, thiohexacyclopropane, and aziridine.

[0091] In the resin material (R1) comprising the polymer constituting the masterbatch and the reactive energy ray-reactive compound, the proportion of the reactive energy ray-reactive compound relative to 100 parts by weight of the polymer constituting the masterbatch is preferably 0.1 parts by weight to 500 parts by weight, more preferably 1 part by weight to 300 parts by weight, and even more preferably 10 parts by weight to 200 parts by weight. Within this range, an adhesive layer with low affinity to the encapsulation material can be formed.

[0092] The resin material (R1) comprising the polymer constituting the masterbatch and the reactive compound of active energy rays can contain any suitable additives as needed. Examples of additives include: active energy ray polymerization initiators, active energy ray polymerization accelerators, crosslinking agents, plasticizers, vulcanizing agents, etc. As the active energy ray polymerization initiator, any suitable initiator can be used depending on the type of active energy ray used. The active energy ray polymerization initiator can be used alone or in combination of two or more. In the resin material (R1) comprising the polymer constituting the masterbatch and the reactive compound of active energy rays, the proportion of the active energy ray polymerization initiator relative to 100 parts by weight of the polymer constituting the masterbatch is preferably 0.1 parts by weight to 10 parts by weight, more preferably 1 part by weight to 5 parts by weight.

[0093] Examples of the aforementioned reactive polymers to reactive energy rays include polymers having functional groups containing carbon-carbon multiple bonds, such as acryloyl, methacryloyl, vinyl, allyl, and ethynyl. Specific examples of polymers having reactive energy ray-reactive functional groups include polymers composed of polyfunctional (meth)acrylates. These polymers preferably contain alkyl esters with 4 or more carbon atoms, more preferably alkyl esters with 6 or more carbon atoms, even more preferably alkyl esters with 8 or more carbon atoms, particularly preferably alkyl esters with 8 to 20 carbon atoms, and most preferably alkyl esters with 8 to 18 carbon atoms. Using polymers with long side chains allows the formation of an adhesive layer with low affinity to the encapsulation material. In these polymers, the percentage of structural units containing alkyl esters with 4 or more carbon atoms as side chains is preferably 30% by weight or more, more preferably 50% by weight or more, even more preferably 70% to 100% by weight, and particularly preferably 80% to 100% by weight, relative to all structural units constituting the polymer. If it falls within this range, an adhesive layer with low affinity to the encapsulation material can be formed.

[0094] The resin material (R2) containing the reactive polymer can further contain the reactive compound (monomer or oligomer). Furthermore, the resin material (R2) containing the reactive polymer can contain any suitable additives as needed. Specific examples of additives are the same as those that can be included in the resin material (R1) containing both the polymer constituting the masterbatch and the reactive compound. In the resin material (R2) containing the reactive polymer, the proportion of the reactive polymer initiator relative to 100 parts by weight is preferably 0.1 to 10 parts by weight, more preferably 1 to 5 parts by weight.

[0095] C. Substrate

[0096] Examples of substrates include: resin sheets, nonwoven fabrics, paper, metal foils, woven fabrics, rubber sheets, foam sheets, and laminates thereof (especially 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 copolymer, ethylene-vinyl acetate copolymer (EVA), polyamide (nylon), fully aromatic polyamide (aramid), polyimide (PI), polyvinyl chloride (PVC), polyphenylene sulfide (PPS), fluorinated resins, and polyetheretherketone (PEEK). Examples of nonwoven fabrics include: nonwoven fabrics based on heat-resistant natural fibers such as Manila hemp nonwoven fabrics; and synthetic resin nonwoven fabrics such as polypropylene resin nonwoven fabrics, polyethylene resin nonwoven fabrics, and ester-based resin nonwoven fabrics. Examples of metal foils include copper foil, stainless steel foil, and aluminum foil. Examples of paper foils include washi paper and kraft paper.

[0097] The thickness of the substrate can be set to any appropriate thickness according to the desired strength or flexibility, and the intended use. The thickness of the substrate is preferably less than 1000 μm, more preferably 1 μm to 1000 μm, even more preferably 1 μm to 500 μm, particularly preferably 3 μm to 300 μm, and most preferably 5 μm to 250 μm.

[0098] The aforementioned substrate may have undergone surface treatment. Examples of surface treatments include: corona treatment, chromic acid treatment, ozone exposure, flame exposure, high-voltage electric shock exposure, ionizing radiation treatment, and coating treatment using a primer.

[0099] Examples of organic coating materials include, for instance, those described in Plastic Hard Coating Materials II (CMC Publication, (2004)). Polyurethane polymers are preferred, and polyacrylic polyurethane, polyester polyurethane, or precursors thereof are more preferred. This is because coating / applying to the substrate is simple, and a variety of substances are available industrially and inexpensively. The polyurethane polymer is, for example, a polymer formed from a reaction mixture of isocyanate monomers and alcohol-containing hydroxyl monomers (e.g., hydroxyl-containing acrylic compounds or hydroxyl-containing ester compounds). The organic coating material may contain chain extenders such as polyamines, antioxidants, oxidation stabilizers, etc., as any additive. The thickness of the organic coating layer is not particularly limited; for example, it is suitable to be about 0.1 μm to 10 μm, preferably about 0.1 μm to 5 μm, and more preferably about 0.5 μm to 5 μm.

[0100] D. Second adhesive layer

[0101] The second adhesive layer described above can be an adhesive layer composed of any suitable adhesive. In one embodiment, as described above, the second adhesive layer further comprises thermally expandable microspheres.

[0102] The adhesive included in the second adhesive layer described above can be a curing adhesive (e.g., an active energy radiation curing adhesive) or a pressure-sensitive adhesive. Examples of pressure-sensitive adhesives include acrylic adhesives and rubber adhesives. The adhesives described in section B can be used as these adhesives.

[0103] As the aforementioned thermally expandable microspheres, any suitable thermally expandable microsphere can be used, as long as it can expand or foam upon heating. For example, microspheres obtained by encapsulating a substance that easily expands upon heating within an elastic shell can be used. Such thermally expandable microspheres can be manufactured using any suitable method, such as coagulation or interfacial polymerization.

[0104] Examples of substances that readily expand upon heating include: propane, propylene, butene, n-butane, isobutane, isopentane, neopentane, n-pentane, n-hexane, isohexane, heptane, octane, petroleum ether, halides of methane, tetraalkylsilanes, and other low-boiling-point liquids; azodicarbonamide that vaporizes through thermal decomposition; and so on.

[0105] Examples of polymers constituting the aforementioned shell include: nitrile monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, and trans-butenedionitrile; carboxylic acid monomers such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and citraconic acid; vinylidene chloride; vinyl acetate; (meth)acrylates such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, isobornyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, and β-carboxyethyl acrylate; styrene monomers such as styrene, α-methylstyrene, and chlorostyrene; amide monomers such as acrylamide, substituted acrylamide, methacrylamide, and substituted methacrylamide; and so on. Polymers composed of these monomers can be homopolymers or copolymers. Examples of such copolymers include: vinylidene chloride-methyl methacrylate-acrylonitrile copolymer, methyl methacrylate-acrylonitrile-methacrylonitrile copolymer, methyl methacrylate-acrylonitrile copolymer, acrylonitrile-methacrylonitrile-itaconic acid copolymer, etc.

[0106] As the aforementioned thermally expandable microspheres, inorganic or organic foaming agents can be used. Examples of inorganic foaming agents include: ammonium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium borohydride, and various azides. In addition, examples of organic blowing agents include: chlorofluoroalkane compounds such as trichloromonofluoromethane and dichloromonofluoromethane; azo compounds such as azobisisobutyronitrile, azodicarbonamide, and barium azodicarboxylate; hydrazine compounds such as p-toluenesulfonyl hydrazine, diphenyl sulfonyl hydrazine, 4,4'-oxobis(benzenesulfonyl hydrazine), and allylbis(sulfonyl hydrazine); aminourea compounds such as p-toluenesulfonamide and 4,4'-oxobis(benzenesulfonamide); triazole compounds such as 5-morpholino-1,2,3,4-thiatriazole; N,N'-dinitrospentamethylenetetramine and N,N'-dimethyl-N,N'-dinitrosterephthalamide; and other N-nitroso compounds.

[0107] The aforementioned thermally expandable microspheres can be commercially available. Specific examples of commercially available thermally expandable microspheres include: Matsumoto Microsphere (grades: F-30, F-30D, F-36D, F-36LV, F-50, F-50D, F-65, F-65D, FN-100SS, FN-100SSD, FN-180SS, FN-180SSD, F-190D, F-260D, F-2800D) manufactured by Matsumoto Oils & Fats Co., Ltd., and Japan Fillite. Products manufactured by Co., Ltd. under the brand name "Expancel" (grades: 053-40, 031-40, 920-40, 909-80, 930-120), products manufactured by Kureha Chemical Industry Co., Ltd. under the brand name "DAIFOAM" (grades: H750, H850, H1100, S2320D, S2640D, M330, M430, M520), products manufactured by Kureha Chemical Industry Co., Ltd. under the brand name "ADVANCELL" (grades: EML101, EMH204, EHM301, EHM302, EHM303, EM304, EHM401, EM403, EM501), products manufactured by Sekisui Chemical Industry Co., Ltd., etc.

[0108] The particle size of the aforementioned thermally expandable microspheres before heating is preferably 0.5 μm to 80 μm, more preferably 5 μm to 45 μm, even more preferably 10 μm to 20 μm, and particularly preferably 10 μm to 15 μm. Therefore, the average particle size of the aforementioned thermally expandable microspheres before heating is preferably 6 μm to 45 μm, more preferably 15 μm to 35 μm. The aforementioned particle size and average particle size are values ​​obtained by particle size distribution measurement method in laser scattering.

[0109] The aforementioned thermally expandable microspheres preferably possess a moderate strength that does not break down up to a volume expansion rate of at least 5 times, more preferably at least 7 times, and even more preferably at least 10 times. When using such thermally expandable microspheres, adhesive forces can be efficiently reduced through heat treatment.

[0110] The proportion of thermally expandable microspheres in the adhesive layer can be appropriately set according to the desired reduction in adhesive strength, etc. Regarding the proportion of thermally expandable microspheres, it is, for example, 1 to 150 parts by weight, more preferably 10 to 130 parts by weight, and even more preferably 25 to 100 parts by weight, relative to 100 parts by weight of the base polymer forming the second adhesive layer.

[0111] When the adhesive layer contains thermally expandable microspheres, the arithmetic surface roughness Ra of the adhesive layer before the thermally expandable microspheres expand (i.e., before heating) is preferably 500 nm or less, more preferably 400 nm or less, and even more preferably 300 nm or less. If it falls within this range, an adhesive sheet with excellent adhesion to the adhered object can be obtained. Such an adhesive layer with excellent surface smoothness can be obtained, for example, by making the thickness of the adhesive layer within the above range; or by coating the adhesive layer onto a release film and performing a transfer process when other adhesive layers are present. It should be noted that, as explained in item A above, when the adhesive sheet of the present invention also contains other adhesive layers, these other adhesive layers may contain thermally expandable microspheres. When these other adhesive layers contain thermally expandable microspheres, the arithmetic surface roughness Ra of these adhesive layers is also preferably within the above range.

[0112] When the aforementioned adhesive layer contains thermally expandable microspheres, the adhesive layer preferably comprises an adhesive made of a base polymer having a dynamic storage modulus in the range of 5 kPa to 1 MPa (more preferably 10 kPa to 0.8 MPa) at 80°C. With such an adhesive layer, an adhesive sheet with moderate adhesion before heating and whose adhesive force is easily reduced by heating can be formed. It should be noted that the dynamic storage modulus can be measured using a dynamic viscoelasticity measuring device (e.g., the trade name "ARES" manufactured by Rheometrics Co.) under measurement conditions of a frequency of 1 Hz and a heating rate of 10°C / min.

[0113] E. Method for manufacturing adhesive sheets

[0114] The adhesive sheet of the present invention can be manufactured by any suitable method. Examples of methods for manufacturing the adhesive sheet include: directly coating a composition containing an adhesive onto a substrate; or coating a composition containing an adhesive onto any suitable substrate and transferring the resulting coating onto the substrate. The composition containing the adhesive may contain any suitable solvent.

[0115] In forming an adhesive layer containing thermally expandable microspheres, a composition comprising thermally expandable microspheres, an adhesive, and any suitable solvent can be coated onto a substrate to form the adhesive layer. Alternatively, the thermally expandable microspheres can be sprinkled onto the adhesive coating layer and then embedded into the adhesive using a laminator or the like to form an adhesive layer containing thermally expandable microspheres.

[0116] As a coating method for the aforementioned adhesives and compositions, any suitable coating method can be employed. For example, each layer can be formed by drying after coating. Examples of coating methods include those using a multi-functional coating machine, a die-casting machine, a gravure coating machine, or a dispensing machine. Examples of drying methods include natural drying and heat drying. The heating temperature during heat drying can be set to any suitable temperature depending on the characteristics of the substance being dried.

[0117] Example

[0118] The present invention will now be specifically described through embodiments, but the present invention is not limited to these embodiments. The evaluation methods in the embodiments are as follows. Furthermore, in the embodiments, unless otherwise specified, "parts" and "%" are based on weight.

[0119] (1) sp value

[0120] The sp value of the polymer in the adhesive layer after the adhesive sheet is formed is calculated using Fedors' method (Hideki Yamamoto, *Basic Applications and Calculation Methods of sp Value*, published by Information Corporation of Japan, April 3, 2006, pp. 66-67). Specifically, this sp value is based on the evaporation energy Δe (cal) of each atom or group of atoms forming the polymer at 25°C and the molar volume ΔV (cm³) of each atom or group of atoms forming the polymer at 25°C. 3 ), which can be calculated using the following formula.

[0121] Sp value = (ΣΔe / ΣΔv) 1 / 2

[0122] Furthermore, when the polymer is a copolymer, its SP value is calculated as follows: calculate the SP value of the homopolymer of each structural unit constituting the copolymer, multiply these SP values ​​by the mole fraction of each structural unit and sum them up to obtain the SP value.

[0123] In the above case, the analytical methods for each structural unit (polymer composition analysis) can be determined by taking an appropriate sample of the adhesive layer from the adhesive sheet, immersing it in organic solvents such as dimethylformamide (DMF), acetone, methanol, and tetrahydrofuran (THF), recovering the solvent-soluble portion of the obtained sample, and then determining the composition based on analytical methods such as gel permeation chromatography (GPC), nuclear magnetic resonance spectrometry (NMR), infrared spectroscopy (IR), and mass spectrometry.

[0124] (2) Contact angle

[0125] The adhesive sheet was placed on a glass slide with the adhesive layer facing upwards, and the contact angle of the adhesive layer surface relative to 4-tert-butylphenyl glycidyl ether was measured.

[0126] Two μl of 4-tert-butylphenyl glycidyl ether was dropped onto the surface of the adhesive layer, and the contact angle (N=5) was measured after 5 seconds. The contact angle was measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., trade name "CX-A type") at 23°C and 50% RH.

[0127] (3) Adhesion to the encapsulating resin (adhesion of the epoxy resin to the encapsulating resin at 23°C when the epoxy resin is cured on the adhesive layer).

[0128] In the examples and comparative examples, the adhesive layer surface of the adhesive sheet (size: 125mm × 125mm) was provided with a 0.6mm thick frame-like spacer (internal size 100mm × 100mm). Granular epoxy encapsulating resin (manufactured by SUMITOMO BAKELITE Co., Ltd., G730) was dispersed inside the spacer, resulting in a cured resin thickness of 0.6mm. A silicone-treated release liner was then placed on top. The evaluation sample was then compressed using a vacuum compression molding machine at 150°C for 600 seconds at 0.3 MPa, and then cured at 150°C for 1 hour. Encapsulating resin was formed on the adhesive sheet of the adhesive sheet, thus forming a structure.

[0129] The structure obtained as described above was cooled, and then a sample (20 mm wide × 100 mm long) was cut from the structure. The adhesive tape was then peeled off from the sample using a tensile testing machine. After mounting the sample in the tensile testing machine, it was placed at an ambient temperature of 23°C (room temperature) for 30 minutes. The test force when peeling the tape at room temperature (300 mm / min, 180-degree peel) was then taken as the adhesion force to the encapsulating resin.

[0130] (4) Shear adhesion

[0131] Using double-sided adhesive tape No. 585 manufactured by Nitto Denko Corporation, the adhesive sheet (size: 20mm × 20mm) obtained in the examples and comparative examples was adhered and fixed to a specified base (e.g., a 20mm × 20mm silicon chip) with the side opposite to the adhesive layer. Using tweezers, a 5mm × 5mm silicon chip (mirror finish) was vertically adhered to the adhesive surface layer of the adhesive sheet without touching the chip corners. Then, the sample was heated at 130°C for 30 minutes to ensure a tight bond between the silicon chip and the adhesive surface, thus creating an evaluation sample.

[0132] For the evaluation sample, at an ambient temperature of 150°C, a measurement terminal was installed on the side of a 5mm × 5mm silicon chip at a height of 250μm from the bonding surface using a Nordson Dage4000. An external force was applied to the chip in the horizontal direction at a shear rate of 500μm / sec, and the maximum failure load was read from the obtained load-displacement curve. This load was taken as the shear bond strength at an ambient temperature of 150°C.

[0133] (5) Cross-sectional observation of the encapsulating resin

[0134] In the examples / comparative examples, the adhesive layer surface of the adhesive sheet was dispersed with glass-filled particulate encapsulating resin (SUMITOMO BAKELITE Co., Ltd. G730), and pressurized at 145°C for 10 min for 0.3 MPa to form a resin layer. Then, after heating to 150°C for 4 h and returning to room temperature, the tape was peeled off at room temperature (300 mm / min, 180-degree peel). Next, the portion of the adhesive tape adhering to the resin was cut off, and the cross-section was sputtered with a Pt / Pd alloy and observed using a SEM (Hitachi, Ltd. "S-3400N", 10 kV applied voltage, high vacuum, SE mode, 1000x magnification).

[0135] An observation of a layer without glass filler (adhesive layer or a mixed phase containing adhesive layer components and resin layer components) on a resin layer containing glass filler is evaluated as 0, and no layer is evaluated as ×.

[0136] [Example 1]

[0137] A composition for forming an adhesive layer is prepared by mixing 100 parts by weight of acrylic copolymer A (a copolymer of butyl acrylate (BA), methyl methacrylate (MMA), and hydroxyethyl acrylate (HEA), BA:MMA:HEA = 65:30:5 (by weight)), 1.5 parts by weight of isocyanate crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "CORONATE L"), and 0.01 parts by weight of reaction aid (manufactured by Tokyo Fine Chemical Co., Ltd., trade name "OM-5").

[0138] The adhesive layer forming composition is coated on one side of a polytetrafluoroethylene film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) serving as a substrate, to obtain an adhesive sheet consisting of a substrate and an adhesive layer (thickness 5 μm).

[0139] The resulting adhesive sheets were used for the evaluations (1) to (4) above. The results are shown in Table 1.

[0140] [Example 2]

[0141] Without the addition of reaction aids, 10 parts by weight of a terpene phenolic tackifying resin (manufactured by SUMITOMO BAKELITE Co., Ltd., trade name "SUMILITE RESIN PR51732") were further mixed to prepare an adhesive layer forming composition. Otherwise, the process was the same as in Example 1, and an adhesive sheet was obtained. The obtained adhesive sheets were subjected to the above evaluations (1) to (4). The results are shown in Table 1.

[0142] [Example 3]

[0143] Without adding any reaction aids, 20 parts by weight of a terpene phenolic tackifying resin (manufactured by YASUHARA CHEMICAL Co., Ltd., trade name "YS Polyster S145") were further mixed to prepare an adhesive layer forming composition with an adhesive layer thickness of 10 μm. Otherwise, the process was the same as in Example 1 to obtain an adhesive sheet. The obtained adhesive sheets were submitted for the evaluations (1) to (4) described above. The results are shown in Table 1.

[0144] [Example 4]

[0145] Without adding any reaction aids, 20 parts by weight of a terpene phenolic tackifying resin (manufactured by YASUHARA CHEMICAL Co., Ltd., trade name "YS Polyster T145") were further mixed to prepare an adhesive layer forming composition with an adhesive layer thickness of 10 μm. Otherwise, the process was the same as in Example 1 to obtain an adhesive sheet. The obtained adhesive sheets were subjected to the above evaluations (1) to (4). The results are shown in Table 1.

[0146] [Example 5]

[0147] A composition for forming an adhesive layer is prepared by mixing 100 parts by weight of an acrylic copolymer B (a copolymer of 2-ethylhexyl acrylate (2EHA), butyl acrylate (BA), acrylic acid (AA), and hydroxyethyl acrylate (HEA) in a ratio of 2EHA:BA:AA:HEA = 50:50:4:1 (by weight)), 5 parts by weight of an epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "TETRAD C"), and 20 parts by weight of a terpene phenolic tackifying resin (manufactured by SUMITOMO BAKELITE Co., Ltd., trade name "SUMILITE RESIN PR12603").

[0148] The adhesive layer forming composition is coated on one side of a polytetrafluoroethylene film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) serving as a substrate, to obtain an adhesive sheet consisting of a substrate and an adhesive layer (thickness 10 μm).

[0149] The resulting adhesive sheets were used for the evaluations (1) to (4) above. The results are shown in Table 1.

[0150] [Example 6]

[0151] A composition for forming an adhesive layer is prepared by mixing 100 parts by weight of an acrylic copolymer C (a copolymer of 2-ethylhexyl acrylate (2EHA), ethyl acrylate (EA), methyl methacrylate (MMA), and hydroxyethyl acrylate (HEA) in a ratio of 2EHA:EA:MMA:HEA = 30:65:5:5 (by weight)), 0.05 parts by weight of a reaction aid (manufactured by Tokyo Fine Chemical Co., Ltd., trade name "OL-1"), 3 parts by weight of an isocyanate crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "CORONATE L"), and 20 parts by weight of a rosin-based tackifier (manufactured by Arakawa Chemical Industry Co., Ltd., trade name "PENSEL D125").

[0152] The adhesive layer forming composition is coated on one side of a polytetrafluoroethylene film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) serving as a substrate, to obtain an adhesive sheet consisting of a substrate and an adhesive layer (thickness 10 μm).

[0153] The resulting adhesive sheets were used for the evaluations (1) to (4) above. The results are shown in Table 1.

[0154] [Comparative Example 1]

[0155] A composition for forming an adhesive layer is prepared by mixing 100 parts by weight of an acrylic copolymer D (a copolymer of 2-ethylhexyl acrylate (2EHA) and hydroxyethyl acrylate (HEA), 2EHA:HEA = 100:5 (by weight)), 0.05 parts by weight of a reaction aid (manufactured by Tokyo Fine Chemical Co., Ltd., trade name "OL-1"), 1.5 parts by weight of an isocyanate crosslinking agent (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "CORONATE L"), and 10 parts by weight of a terpene phenolic tackifying resin (manufactured by SUMITOMO BAKELITE Co., Ltd., trade name "SUMILITE RESIN PR12603").

[0156] The adhesive layer forming composition is coated on one side of a polytetrafluoroethylene film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) serving as a substrate, to obtain an adhesive sheet consisting of a substrate and an adhesive layer (thickness 10 μm).

[0157] The resulting adhesive sheets were used for the evaluations (1) to (4) above. The results are shown in Table 1.

[0158] [Comparative Example 2]

[0159] A composition for forming an adhesive layer is prepared by mixing 100 parts by weight of an acrylic copolymer E (a copolymer of 2-ethylhexyl acrylate (2EHA) and acrylic acid (AA), 2EHA:AA = 100:5 (by weight)), 0.5 parts by weight of an epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "TETRAD C"), and 10 parts by weight of a terpene phenolic tackifying resin (manufactured by YASUHARA CHEMICAL Co., Ltd., trade name "YS Polyster S145").

[0160] The adhesive layer forming composition is coated on one side of a polytetrafluoroethylene film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) serving as a substrate, to obtain an adhesive sheet consisting of a substrate and an adhesive layer (thickness 10 μm).

[0161] The resulting adhesive sheets were used for the evaluations (1) to (4) above. The results are shown in Table 1.

[0162] [Table 1]

[0163]

[0164] For Example 1 and Comparative Example 1, the SEM images of the observation plane in "(5) Cross-sectional observation of the encapsulating resin" are shown below. Figure 3In the cross-sectional specimens prepared by the examples, a gray resin layer containing glass filler and a darker gray layer without glass filler (i.e., an adhesive layer containing a mixed layer) were observed, while in the comparative examples, only a gray resin layer containing glass filler was observed. The same results as in Example 1 were observed in Examples 2-6. Furthermore, the same results as in Comparative Example 1 were obtained in Comparative Example 2.

[0165] Explanation of reference numerals in the attached figures

[0166] 10 Substrate

[0167] 20 Adhesive layers

[0168] 30 Second adhesive layer

[0169] 100 and 200 adhesive sheets

Claims

1. An adhesive sheet comprising a substrate and an adhesive layer disposed on at least one side of the substrate, The adhesive layer contains adhesive. The adhesive contains an Sp value of 19.5 (J / cm). 3 ) 1 / 2 ~25 (J / cm) 3 ) 1 / 2 The basic polymer, The adhesive is an acrylic adhesive. The acrylic adhesive, as a base polymer, comprises a base polymer having alkyl esters with 6 or fewer carbon atoms as side chains. The percentage of alkyl esters having 6 or fewer carbon atoms as side chain structural units relative to all structural units constituting the acrylic polymer is 50% or more by weight. The contact angle of the adhesive layer relative to 4-tert-butylphenyl glycidyl ether is less than 47°. The shear bond strength at 150°C when the adhesive layer is bonded to the silicon chip is above 400g.

2. The adhesive sheet according to claim 1, comprising the substrate, the adhesive layer disposed on one side of the substrate, and a second adhesive layer disposed on the side of the substrate opposite to the adhesive layer.

Images