Adhesive sheet

Abstract

Provided is an adhesive sheet which has moderate adhesiveness to a sealing resin for sealing a semiconductor chip and a semiconductor chip, can be easily peeled from the sealing resin, is less likely to cause a peeling residue, and is less likely to cause a height difference between the semiconductor chip and the sealing resin after peeling the adhesive sheet. The adhesive sheet of the present invention includes a substrate and an adhesive layer disposed on at least one side of the substrate, the adhesive layer containing an acrylic adhesive, the adhesive sheet having a recess amount of 5 μm or less at 23°C using TMA, and the adhesive layer having a T2 relaxation time (T2) of the S component based on pulsed NMR of 45 μsec or less. 2s ) for 45 μsec or less.

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 sealing is sometimes performed on the semiconductor chips to prevent damage and expansion of metal wiring. In the resin sealing process, from an operability perspective, the semiconductor chips are sometimes sealed onto an adhesive sheet. For example, to prevent movement of the semiconductor chips, multiple semiconductor chips are arranged on a pre-defined adhesive sheet as a temporary fixing material, and the semiconductor chips are sealed onto the adhesive sheet in one step. Then, in a predetermined subsequent process, the adhesive sheet is peeled off from the resin used to seal the semiconductor chips.

[0003] In the process described above, if conventional adhesive sheets are used, there is a problem of adhesive residue being left on the structure containing the sealing resin and the semiconductor chip when the adhesive sheet is peeled off. Furthermore, during sealing, the semiconductor chip is pressed into the adhesive sheet, resulting in a height difference between the semiconductor chip and the sealing resin after the adhesive sheet is peeled off. This height difference can lead to insufficient protection of the semiconductor chip or prevent the formation of metal wiring, among other problems. Additionally, adhesive residue caused by this height difference is also easily generated.

[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 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] The present invention was made to solve the above-mentioned prior art problems, and its object is to provide an adhesive sheet that has moderate adhesion to the sealing resin used to seal the semiconductor chip and the semiconductor chip, can be easily peeled off from the sealing resin, is unlikely to produce residual adhesive during peeling, and is unlikely to produce a height difference between the semiconductor chip and the sealing resin after the adhesive sheet is peeled off.

[0010] Solution for solving the problem

[0011] 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 acrylic adhesive, the adhesive sheet having a depression of less than 5 μm at 23°C using TMA, and the T2 relaxation time (T2) of the S component of the adhesive layer based on pulsed NMR.2s The value is below 45 μsec.

[0012] In one embodiment, the thickness change rate of the adhesive layer after adding 4-tert-butylphenyl glycidyl ether to the surface of the adhesive layer and letting it stand for 1 minute is less than 160%.

[0013] In one embodiment, the thickness change of the adhesive layer after adding 4-tert-butylphenyl glycidyl ether to the surface of the adhesive layer and letting it stand for 1 minute is less than 20 μm.

[0014] In one embodiment, the adhesive layer comprises an adhesive having an sp value of 18 (cal / cm). 3 ) 1 / 2 ~20 (cal / cm) 3 ) 1 / 2 The basic polymer.

[0015] In one embodiment, the acrylic adhesive comprises a crosslinked acrylic polymer as the base polymer.

[0016] In one embodiment, the acrylic adhesive comprises an epoxy crosslinking agent.

[0017] In one embodiment, the amount of the epoxy crosslinking agent is 0.6 to 15 parts by weight relative to 100 parts by weight of the acrylic polymer.

[0018] In one embodiment, the substrate is a resin sheet made of a resin with a glass transition temperature (Tg) of 25°C or higher.

[0019] In one embodiment, the thickness of the substrate is 20% to 90% of the total thickness of the adhesive sheet.

[0020] In one embodiment, the indentation of the adhesive sheet at 145°C using TMA is 1 μm to 35 μm.

[0021] In one embodiment, the amount of nitrogen generated during the heat treatment of the adhesive layer is 0.06% to 1% by weight.

[0022] In one embodiment, the adhesive sheet comprises: 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.

[0023] In one embodiment, the adhesive sheet is a temporary fixing material used in the resin sealing process of a semiconductor chip.

[0024] In one embodiment, the adhesive sheet is used when the sealing resin is cured on the adhesive sheet.

[0025] The effects of the invention

[0026] According to the present invention, an adhesive sheet can be provided that has moderate adhesion to a sealing resin used for sealing a semiconductor chip and the semiconductor chip, can be easily peeled off from the sealing resin, is unlikely to produce residual adhesive during peeling, and is unlikely to produce a height difference between the semiconductor chip and the sealing resin after the adhesive sheet is peeled off. Attached Figure Description

[0027] Figure 1 This is a cross-sectional schematic diagram of an adhesive sheet according to one embodiment of the present invention.

[0028] Figure 2 (a) is a diagram illustrating an example of using a conventional adhesive sheet in a semiconductor chip resin sealing process. (b) is a diagram illustrating an example of using the adhesive sheet of the present invention in a semiconductor chip resin sealing process.

[0029] Figure 3 This is a cross-sectional schematic diagram of an adhesive sheet according to another embodiment of the present invention. Detailed Implementation

[0030] A. Overview of Adhesive Sheets

[0031] 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. The adhesive layer comprises an acrylic adhesive.

[0032] The adhesive sheet of the present invention can be suitably used as a temporary fixing material for resin sealing of semiconductor chips. More specifically, the adhesive sheet of the present invention can be used as a temporary fixing material for resin sealing of semiconductor chips when semiconductor chips are arranged on an adhesive layer of the adhesive sheet, covered with resin (usually an epoxy resin), and the semiconductor chips are resin sealed by curing the sealing resin. After the semiconductor chip is resin sealed, the adhesive sheet can be peeled off from the structure composed of the sealing resin and the semiconductor chip during specified subsequent processes (e.g., back-side grinding of the sealing resin, patterning, bumping, chip forming (cutting)). The epoxy equivalent of the sealing resin is, for example, 50 g / eq to 500 g / eq.

[0033] The indentation of the aforementioned adhesive sheet at 23°C using TMA is less than 5 μm. Additionally, the T2 relaxation time (T2) of the S component of the adhesive layer based on pulsed NMR is [not specified]. 2sThe time difference is less than 45 μsec. Based on the adhesive sheet having these characteristics, when the semiconductor chip is resin-sealed onto the adhesive sheet and then the adhesive sheet is peeled off, a height difference between the semiconductor chip and the sealing resin can be prevented.

[0034] The factors contributing to the height difference between the semiconductor chip and the sealing resin are considered to include: migration of adhesive layer components into the sealing resin; embedding of the semiconductor chip into the adhesive layer due to the force applied to the semiconductor chip during resin sealing; and so on. Figure 2 (a) will be explained in more detail. Figure 2 (a) shows an example of using a conventional adhesive sheet 100' for resin sealing of a semiconductor chip. The adhesive sheet 100' has an adhesive layer, the outer surface of which serves as the attachment surface. Conventionally, when resin sealing a semiconductor chip, firstly, a semiconductor chip 1 is attached to the adhesive sheet 100' (a1). Then, a composition 2' containing monomers that serve as precursors for a sealing resin 2 is applied in a manner that seals the semiconductor chip 1 (a-ii), and then the composition 2' is cured (a-iii). It should be noted that, for example, a composition containing a naphthalene-type difunctional epoxy resin (epoxy equivalent: 144) can be used as the above composition. Next, in a predetermined subsequent process, the adhesive sheet 100' is peeled off from the structure A containing the semiconductor chip 1 and the sealing resin 2 (a-iv). In such an operation, component migration occurs between the adhesive layer and the sealing resin in the processes shown in (a-ii) and (a-iii), forming a mixed phase of adhesive and sealing resin components in the sealing resin. If this mixed phase forms, it is disrupted when the adhesive sheet is peeled off, and a portion of the sealing resin is peeled off along with the adhesive sheet, resulting in a height difference between the semiconductor chip and the sealing resin. Furthermore, in the processes shown in (a-ii) and (a-iii), a portion of the semiconductor chip is embedded in the adhesive layer due to the force applied to it. This embedding of the semiconductor chip in the adhesive layer also contributes to the height difference between the semiconductor chip and the sealing resin.

[0035] In this invention, by setting the indentation amount at 23°C using TMA to below 5 μm, it is possible to prevent the migration of adhesive layer components into the sealing resin and the embedding of the semiconductor chip into the adhesive layer (especially the embedding of the semiconductor chip into the adhesive layer). Figure 2 (b)). Additionally, by measuring the T2 relaxation time (T) of the S component of the adhesive layer based on pulsed NMR. 2s Setting the time to below 45 μsec can prevent the migration of adhesive layer components into the sealing resin and the embedding of the semiconductor chip into the adhesive layer (especially the migration of adhesive layer components into the sealing resin). Figure 2 (b)

[0036] The amount of indentation in the adhesive sheet at 23°C using TMA is preferably 4 μm or less, more preferably 3.5 μm, and even more preferably 3 μm or less. Within this range, the effects of the present invention become significant. The smaller the amount of indentation in the adhesive sheet at 23°C using TMA, the more preferred it is, with a lower limit preferably 0.1 μm (preferably 0.01 μm). For example, the indentation amount within the above range can be achieved by appropriately adjusting the composition of the adhesive constituting the adhesive layer and the structure (especially the crosslinking density) of the base polymer contained in the adhesive.

[0037] "Indentation depth of the adhesive sheet at 23°C using TMA" refers to the indentation depth after 60 minutes of contact between the probe and the adhesive layer (first adhesive layer) using a thermomechanical analyzer. The measurement conditions were set as follows: probe: with needle; nitrogen flow rate: 50.0 ml / min; indentation load: 0.01 N. Additionally, when the adhesive sheet has an adhesive layer only on one side of the substrate (i.e., without the second adhesive layer described later), the above measurement was performed after forming a standard adhesive layer on the surface of the substrate opposite to the adhesive layer (first adhesive layer). The standard adhesive layer is an adhesive layer with a thickness of 45 μm formed by coating with the following adhesive layer forming composition, which is obtained by mixing 100 parts by weight of an acrylic copolymer (a copolymer of 2-ethylhexyl acrylate (2EHA), ethyl acrylate (EA), methyl methacrylate (MMA) and 2-hydroxyethyl acrylate (HEA), with 2EHA structural units:EA structural units:MMA structural units:HEA structural units = 30:70:5:5 (weight ratio) (molecular weight (Mw = 450,000)), 10 parts by weight of a tackifier (manufactured by YASUHARACHEMICAL CO.,LTD., trade name "Mightyace G125"), 2 parts by weight of an isocyanate crosslinking agent (manufactured by Tosoh Corporation, trade name "CORONATE L"), 30 parts by weight of thermally expandable microspheres (manufactured by Matsumoto Oils & Fats Co., Ltd., trade name "Matsumoto Microsphere F-190D"), and toluene.

[0038] The recess amount of the adhesive sheet at 145°C using TMA is preferably 1 μm to 35 μm, more preferably 1 μm to 34 μm, and even more preferably 2 μm to 34 μm. Within this range, the effects of the present invention become significant. Furthermore, even under high-temperature environments (e.g., the heat treatment environment during resin sealing), embedding of the semiconductor chip into the adhesive layer can be prevented.

[0039] Figure 3This is a cross-sectional schematic diagram of an adhesive sheet according to another embodiment of the present invention. The adhesive sheet 200 further comprises a second adhesive layer 30 on the side of the substrate 10 opposite to the adhesive layer 20. That is, the adhesive sheet 200 comprises the adhesive layer 20, the substrate 10, and the second adhesive layer 30 in sequence. By providing the second adhesive layer 30, when performing resin sealing on the base, the second adhesive layer 30 can be attached sideways to the base, thereby providing good fixation for the adhesive sheet 200.

[0040] In one embodiment, the second adhesive layer comprises thermally expandable microspheres. These microspheres are capable of expanding at a specified temperature. When an adhesive layer containing such thermally expandable microspheres is heated above the specified temperature, the microspheres expand, creating unevenness on the adhesive surface (i.e., the surface of the second adhesive layer), resulting in reduced or absent 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 when the adhesive sheet is peeled off (e.g., peeled from the pedestal), the adhesive force is reduced or absent by heating, exhibiting good peelability.

[0041] The adhesive strength A of the adhesive sheet of the present invention at 23°C when the adhesive layer is applied to polyethylene terephthalate is preferably 0.05 N / 20 mm to 1 N / 20 mm, 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 preferably 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 applied to polyethylene terephthalate" refers to the adhesive force measured by applying the adhesive layer of an adhesive sheet (20mm wide × 140mm long) to a polyethylene terephthalate film (25μm thick) (adhesive conditions: 2kg roller passes back and forth once) and 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°).

[0042] The shear bond strength B of the adhesive sheet of the present invention at 150°C when a silicon chip is attached to the adhesive layer is preferably 500g or more, more preferably 700g to 1500g, and even more preferably 800g to 1200g. Within this range, the adhesive has high cohesive strength, exhibiting preferred adhesive strength even at high temperatures (e.g., heating processes used to cure the sealing resin), and preventing displacement of the adhered object (e.g., a semiconductor chip) disposed on the adhesive sheet. The shear bond strength can be measured by: vertically attaching the mirror surface of a silicon chip (size: 5mm × 5mm) to the adhesive layer without touching the chip corners; heating at 130°C for 30 minutes to ensure adhesion between the silicon chip and the adhesive surface; then applying an external force at a shear rate of 500 μm / sec along the direction horizontal to the chip at the measurement temperature (150°C for shear bond strength B measurement); and reading the maximum destructive load from the resulting load-displacement curve. For example, a Nordson Dage4000 can be used as the measuring device. In addition, the measuring terminal for the above measurement can be set at a position 250 μm above the surface of the adhesive layer.

[0043] The shear adhesion force of the adhesive sheet of the present invention at 190°C when a silicon chip is attached to the adhesive layer is preferably 300g to 1000g, more preferably 350g to 750g, and even more preferably 400g to 600g. Within this range, when the adhesive sheet has a second adhesive layer containing thermally expandable microspheres, and the second adhesive layer side exhibits peelability—that is, when heated to cause the thermally expandable microspheres to expand—the adhered material on the adhesive layer can be preferably fixed.

[0044] The thickness of the adhesive sheet of the present invention is preferably 3μm to 300μm, more preferably 5μm to 150μm, and even more preferably 10μm to 100μm.

[0045] B. Adhesive layer

[0046] The aforementioned adhesive layer is composed of an adhesive containing a base polymer. As described above, the T2 relaxation time (T2) of the S component of the adhesive layer based on pulsed NMR is... 2sThe relaxation time is less than 45 μsec. In pulsed NMR measurements, the relaxation time refers to the time from when the excited atoms (groups) return to their ground state after irradiation with an appropriate energy for exciting the atoms being measured. The excited state of the atoms (groups) can be controlled by the amount and duration of energy irradiation. Furthermore, various energy relaxation mechanisms are known to restore the excited atoms (groups) to their ground state, and the relaxation time is determined according to these mechanisms (e.g., "A Latest Overview of NMR for Chemists," Chemical Companions (1997)). The inventors excited an acrylic adhesive (essentially an acrylic polymer contained in the adhesive) under the following conditions... 1 H atoms were measured, and their subsequent relaxation behavior was analyzed. The results showed that the S component (T2) of the relaxation time (T2) was significant, providing information about the molecular motion related to the degree of crosslinking of the base polymer (representatively acrylic polymers) contained in the adhesive layer. 2s It is useful to find that determining the S component (T) of the T2 relaxation time is helpful. 2s The above effects can be achieved by using T. 2s A short crosslink indicates a state where molecular motion related to the degree of crosslinking of the base polymer is restricted; that is, even as crosslinking progresses, the polymer as a whole experiences reduced degrees of freedom of movement. In acrylic adhesives in this state, the gaps between the base polymers are small, and the migration of adhesive layer components into the sealing resin, as well as the migration of low molecular weight components contained in the sealing resin into the adhesive layer, is suppressed. As a result, when a semiconductor chip is resin-sealed onto an adhesive sheet and then the adhesive sheet is peeled off, a height difference between the semiconductor chip and the sealing resin can be prevented.

[0047] T2 relaxation time (T) of the S component of the adhesive layer based on pulsed NMR 2s The preferred value is 10 μsec to 50 μsec, more preferably 10 μsec to 45 μsec, and even more preferably 10 μsec to 40 μsec. If it is within such a range, the above-mentioned effect is significant.

[0048] Regarding the T2 relaxation time (T) of the S component based on pulsed NMR 2s ), 100mg of the adhesive layer can be used as the test sample and the T2 relaxation curve can be obtained by solid echo method. The T2 relaxation curve can be fitted by the following formula (1) to obtain the result.

[0049] M(t) = α·exp(-(1 / Wa)(t / T) 2s ) Wa )+β·exp(-(1 / Wa)(t / T 2L ) Wa )···(1)

[0050] M(t): Free induction decay

[0051] α: Proton ratio (%) of the component with short relaxation time (S component)

[0052] T 2s T2 relaxation time (msec) of the S component

[0053] β: Proton ratio (%) of the component with longer relaxation time (L component)

[0054] T 2L T2 relaxation time (msec) of the L component

[0055] t: Observation time (msec)

[0056] Wa: Shape factor (=1)

[0057] The measurement conditions described above are as follows.

[0058] • 90° pulse width: 2.1μsec

[0059] • Repetition time: 1 sec

[0060] • Total number of times: 32

[0061] • Measurement temperature: 30℃

[0062] After 4-tert-butylphenyl glycidyl ether is dropped onto the surface of the adhesive layer and allowed to stand for 1 minute, the thickness change rate of the adhesive layer is preferably 160% or less, more preferably 150% or less, further preferably 120% or less, and particularly preferably 100% or less. An adhesive layer with such a thickness change rate has a high crosslinking density, which prevents component migration between the adhesive layer and the sealing resin. As a result, when the semiconductor chip is resin-sealed on the adhesive sheet and then the adhesive sheet is peeled off, a height difference between the semiconductor chip and the sealing resin is prevented. The smaller the thickness change rate, the more preferred; its lower limit is, for example, 20% (preferably 10%). The thickness change rate (and the thickness change amount described later) can be set to the above range, for example, by preferably selecting the base polymer (typically an acrylic polymer) contained in the acrylic adhesive. For example, by using an acrylic polymer with a high carbon number (e.g., 4 or more, preferably 8 or more), an adhesive layer with a small thickness change rate (and the thickness change amount described later) can be formed. Regarding the aforementioned thickness change rate, a specified amount (0.02 g using a 22 mm diameter syringe) of 4-tert-butylphenyl glycidyl ether was dropped onto the surface of the adhesive layer, and the mixture was left in an environment of 23°C and 50% RH for 1 minute. The thickness (Dt) of the area where the 4-tert-butylphenyl glycidyl ether was dropped off and the thickness (It) of the area before the dropping operation were calculated using the mathematical formula (Dt-It) / It.

[0063] The thickness change of the adhesive layer after adding 4-tert-butylphenyl glycidyl ether to the surface of the adhesive layer and allowing it to stand for 1 minute is preferably 20 μm or less, more preferably 15 μm or less, further preferably 10 μm or less, and particularly preferably 6 μm or less. This range of thickness change results in a high crosslinking density of the adhesive layer, preventing component migration between the adhesive layer and the sealing resin. Consequently, when the semiconductor chip is resin-sealed on the adhesive sheet and then the adhesive sheet is peeled off, a height difference between the semiconductor chip and the sealing resin is prevented. A smaller thickness change is more preferred, with a lower limit of, for example, 3 μm (preferably 1 μm). The thickness change is calculated using the mathematical formula Dt-It based on Dt and It.

[0064] The gelation rate of the aforementioned adhesive layer is preferably 75% or more, more preferably 85% or more, and even more preferably 90% or more. Within such a range, crosslinking preferably restricts the molecular movement of the base polymer, thus preventing component migration between the adhesive layer and the sealing resin. A higher gelation rate of the adhesive layer is more preferred, with an upper limit, for example, 99.5%. It should be noted that the gelation rate is calculated by impregnating the crosslinked adhesive in ethyl acetate for 7 days and then drying it, using (dry weight after impregnation / dry weight before impregnation) × 100.

[0065] The amount of nitrogen generated during the heat treatment of the adhesive layer is preferably 0.06 wt% to 1.0 wt%, more preferably 0.06 wt% to 0.9 wt%. When the amount of nitrogen generated during the heat treatment of the adhesive layer is within this range, the acrylic adhesive fully exerts its cohesive force, suppressing the migration of low molecular weight components of the sealing resin into the adhesive layer. Therefore, a mixed layer of adhesive layer components and sealing resin components is not formed, and a height difference is less likely to occur at the interface between the semiconductor chip and the sealing resin. Regarding the amount of nitrogen generated during the heat treatment of the adhesive layer, for a sample of 2 mg of adhesive layer placed on a ceramic plate and measured using a microbalance, the amount of nitrogen generated by heating under conditions of 800°C in a thermal decomposition furnace / 900°C in an oxidation furnace was determined using a TN (micro total nitrogen analysis) apparatus. The conditions for the measurement can be set as shown below.

[0066] • Carrier gas: O2 (300 mL / min), Ar (300 mL / min)

[0067] Standard sample: pyridine / toluene solution

[0068] • Detector: Reduced-pressure chemiluminescence detector

[0069] • Range: High concentration

[0070] The thickness of the adhesive layer is preferably 1 μm to 50 μm, more preferably 3 μm to 30 μm, and even more preferably 5 μm to 20 μm. Within this range, an adhesive sheet can be obtained that makes it difficult for the semiconductor chip to be embedded in the resin even under pressure during the sealing process.

[0071] The elastic modulus of the aforementioned 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 loading load and indentation depth of the indenter when it is pressed into the sample from loading to unloading, and calculating the loading 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, as described above.

[0072] The tensile modulus 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 can be measured according to JIS K 7161:2008.

[0073] The preferred probe adhesion value for the above adhesive layer is... The above, or more preferably The above, further preferred The above. If this range is maintained, it can prevent the position of the object (e.g., a semiconductor chip) mounted on the adhesive sheet from shifting. The conditions for measuring the probe adhesive force are set as follows: probe processing speed: 30 mm / min, test speed: 30 mm / min, adhesion load: 100 gf, adhesion holding time: 1 second, probe area:

[0074] The sp value of the above-mentioned basic polymer is preferably 10 (cal / cm). 3 ) 1 / 2 ~30 (cal / cm) 3 ) 1 / 2 More preferably 15 (cal / cm) 3 ) 1 / 2 ~25 (cal / cm) 3 ) 1 / 2 A further preferred value is 18 (cal / cm). 3 ) 1 / 2 ~20 (cal / cm) 3 ) 1 / 2 If it is within such a range, then it is preferable to prevent the migration of components between the adhesive layer and the sealant resin.

[0075] (Acrylic adhesives)

[0076] Examples of acrylic adhesives include those using an acrylic polymer (homopolymer or copolymer) containing one or more alkyl methacrylates as monomers as a prepolymer, and a crosslinked product of the prepolymer as a base polymer. It should be noted that, in this specification, the "base polymer" in the acrylic adhesive layer refers to a polymer formed by crosslinking the prepolymer (uncrosslinked polymer). In one embodiment, the base polymer has a crosslinked structure based on an acrylic polymer and an epoxy crosslinking agent.

[0077] 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. Preferably, alkyl (meth)acrylates having a straight-chain or branched alkyl group having 4 to 20 carbon atoms (more preferably 6 to 20, particularly preferably 8 to 18) are used, and 2-ethylhexyl (meth)acrylate is even more preferred.

[0078] In one embodiment, an alkyl (meth)acrylate having a linear or branched alkyl group having 4 or more carbon atoms is used. Using an alkyl (meth)acrylate preferably prevents component migration between the adhesive layer and the sealant.

[0079] For the purpose of modifying cohesion, heat resistance, crosslinking, etc., the above-mentioned acrylic polymers (prepolymers) may, as needed, contain units corresponding to other monomer components that can copolymerize with the above-mentioned alkyl methacrylates. Examples of such monomer 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; hydroxyl-containing monomers such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyhexyl (meth)acrylate, hydroxyoctyl (meth)acrylate, hydroxydecyl (meth)acrylate, hydroxylauryl (meth)acrylate, and methyl methacrylate (4-hydroxymethylcyclohexyl)methacrylate; styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, and (meth)acrylic acid... Monomers containing sulfonic acid groups, such as methacrylamide propanesulfonic acid, sulfonylpropyl (meth)acrylate, and methacryloyloxynaphthalenesulfonic acid; (N-substituted) amide monomers, such as (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, and N-hydroxymethylpropane (meth)acrylamide; (meth)acrylate aminoethyl ester monomers, such as N,N-dimethylaminoethyl (meth)acrylate and tert-butylaminoethyl (meth)acrylate; (meth)acrylate alkoxyalkyl ester monomers, such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; N- Maleimide monomers such as cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide; itaconimide 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-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; vinyl acetate, vinyl propionate, etc. Vinyl monomers such as N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazolium, vinyloxazole, vinylmorpholine, N-vinylcarboxylic amides, styrene, α-methylstyrene, and N-vinylcaprolactam; cyanoacrylate monomers such as acrylonitrile and methacrylonitrile; epoxy-containing acrylic monomers such as glycidyl acrylate; diol-based acrylate monomers such as polyethylene glycol acrylate, polypropylene glycol acrylate, methoxyethylene glycol acrylate, and methoxypolypropylene glycol acrylate.Acrylate monomers containing heterocyclic rings, halogen atoms, or silicon atoms, such as tetrahydrofurfuryl methacrylate, fluoromethacrylates, and organosilicon methacrylates; multifunctional 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.

[0080] In one embodiment, the aforementioned acrylic polymer (prepolymer) further comprises structural unit a derived from monomers whose glass transition temperature (Tg) at which the homopolymer is formed is -5°C to 150°C (preferably 50°C to 150°C, more preferably 80°C to 120°C). If such structural unit a is included, the molecular motion of the acrylic polymer is restricted, allowing for a preferred adjustment of the T2 relaxation time (Tg) of the S component based on pulsed NMR. 2s The acrylic polymer is described above. Furthermore, adhesive sheets with excellent low-temperature adhesion can be obtained. The content of the aforementioned structural unit a is preferably 0.1% to 20% by weight, more preferably 1% to 10% by weight, particularly preferably 1.5% to 8% by weight, and most preferably 3% to 6% by weight, relative to all structural units constituting the acrylic polymer.

[0081] Monomers with glass transition temperatures (Tg) ranging from -5℃ to 150℃ include, for example, 2-hydroxyethyl acrylate (Tg: -3℃), 2-hydroxyethyl methacrylate (Tg: 77℃), acrylic acid (Tg: 102℃), cyclohexyl methacrylate (Tg: 83℃), dicyclopentyl acrylate (Tg: 120℃), dicyclopentyl methacrylate (Tg: 175℃), isobornyl acrylate (Tg: 94℃), isobornyl methacrylate (Tg: 150℃), tert-butyl methacrylate (Tg: 118℃), methyl methacrylate (Tg: 105℃), styrene (Tg: 80℃), acrylonitrile (Tg: 97℃), and N-acryloyloxymorpholine (Tg: 145℃). Among them, methyl methacrylate is preferred because it improves the transparency of the adhesive layer, thus enhancing the visibility of the adhered objects during processing. In addition, acrylic acid adheres firmly to the adhered objects through intermolecular interactions, making it preferred when strong adhesion is required. Hydroxyethyl acrylate exhibits high reactivity with a variety of crosslinking agents, making it more preferred in terms of controlling relaxation time.

[0082] In one embodiment, the acrylic polymer (prepolymer) further comprises structural units derived from hydroxyl-containing monomers. The content of the structural units derived from hydroxyl-containing monomers relative to all structural units constituting the acrylic polymer is preferably 0.1% to 20% by weight, more preferably 0.5% to 10% by weight, and particularly preferably 1% to 7% by weight.

[0083] The aforementioned acrylic adhesives may contain any suitable additives as needed. Examples of such additives include crosslinking agents, tackifiers, plasticizers (e.g., trimellitate plasticizers, pyromellitic ester plasticizers, etc.), pigments, dyes, fillers, anti-aging agents, conductive materials, antistatic agents, ultraviolet absorbers, light stabilizers, peel modifiers, softeners, surfactants, flame retardants, antioxidants, etc.

[0084] Examples of crosslinking agents contained in the aforementioned acrylic adhesives include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, 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.

[0085] In one embodiment, the amount of crosslinking agent mixed with the acrylic polymer (prepolymer) is preferably 0.08 molar equivalents to 2 molar equivalents, more preferably 0.1 molar equivalents to 1 molar equivalent, relative to the carboxyl groups of the acrylic polymer (prepolymer). Within this range, an acrylic adhesive with high crosslinking density can be formed, which preferably prevents component migration between the adhesive layer and the sealing resin. Here, the amount of crosslinking agent mixed with the acrylic polymer refers to the content of crosslinking agent before crosslinking of the acrylic polymer.

[0086] Specific examples of the isocyanate-based crosslinking agents contained 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 phenyl 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 esters of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "CORONATE HX"). The amount of isocyanate-based crosslinking agent can be set to any suitable amount according to the desired adhesive strength, typically 0.1 to 20 parts by weight, and more preferably 1 to 10 parts by weight, relative to 100 parts by weight of the acrylic polymer. Within this range, adhesive sheets with fewer residual carboxyl groups in the adhesive layer can be obtained. Here, the amount of crosslinking agent refers to the content of crosslinking agent before crosslinking of the acrylic polymer.

[0087] In one embodiment, an epoxy-based crosslinking agent is preferably used as the crosslinking agent. Using an epoxy-based crosslinking agent allows for the preparation of an adhesive sheet that preferably reduces the height difference between the semiconductor chip and the sealing resin. Furthermore, it enables the formation of an adhesive layer with high cohesion, more effectively preventing positional displacement of the adhered objects.

[0088] Examples of epoxy crosslinking agents contained in the aforementioned acrylic adhesives include: N,N,N',N'-tetraglycidyl-m-phenylenediamine, 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 amount of epoxy crosslinking agent can be set to any suitable amount according to the desired adhesive strength, typically 0.01 to 50 parts by weight, more preferably 0.6 to 15 parts by weight, further preferably 2 to 13 parts by weight, and particularly preferably 3 to 10 parts by weight relative to 100 parts by weight of the acrylic polymer. Within this range, adhesive sheets with fewer residual carboxyl groups in the adhesive layer can be obtained. Here, the amount of crosslinking agent refers to the content of crosslinking agent before crosslinking of the acrylic polymer.

[0089] In one embodiment, an epoxy-based crosslinking agent containing nitrogen atoms can be used as the crosslinking agent. Using a crosslinking agent containing nitrogen atoms promotes the crosslinking reaction through catalysis, which is advantageous from the perspective of easily achieving high gelation of the adhesive.

[0090] As the tackifier contained 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, phenolic varnish, etc.), ketone-based tackifying resins, polyamide-based tackifying resins, epoxy-based tackifying resins, and elastic system tackifying resins, etc. The preferred tackifiers are rosin-based, terpene-based, or hydrocarbon-based tackifiers (such as styrene-based resins). Tackifiers can be used alone or in combination of two or more types. 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 8 to 50 parts by weight.

[0091] Preferably, a resin with a high softening point or glass transition temperature (Tg) is used as the aforementioned tackifying resin. Using a resin with a high softening point or glass transition temperature (Tg) allows for the formation of an adhesive layer exhibiting high adhesion even under high-temperature conditions (e.g., high-temperature environments during semiconductor chip sealing 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.

[0092] A low-polarity tackifying resin is preferably used as the aforementioned tackifying resin. Using a low-polarity tackifying resin allows for the formation of an adhesive layer with low affinity for the sealing material. Examples of low-polarity tackifying resins include 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, and other hydrocarbon-based tackifying resins. Tackifiers with 5 to 9 carbon atoms are preferred. This is because such tackifiers are low-polarity, have excellent compatibility with acrylic polymers, do not undergo phase separation over a wide temperature range, and can form an adhesive layer with excellent stability.

[0093] The acid value of the aforementioned tackifying resin is preferably 40 or less, more preferably 20 or less, and even more preferably 10 or less. Within this range, an adhesive layer with low affinity for the sealing material can be formed. The hydroxyl value of the aforementioned tackifying resin is preferably 60 or less, more preferably 40 or less, and even more preferably 20 or less. Within this range, an adhesive layer with low affinity for the sealing material can be formed.

[0094] C. Substrate

[0095] 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; 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. As for paper, examples include Japanese paper and kraft paper.

[0096] In one embodiment, a resin sheet made of a resin with a glass transition temperature (Tg) of 25°C or higher (preferably 40°C or higher, more preferably 50°C or higher) is preferably used as a substrate. Using such a resin sheet allows the substrate to maintain its shape even during heating in the sealing process, preventing the semiconductor chip from embedding into the resin. Examples of resins constituting such a resin sheet include polyethylene terephthalate, polyimide, and polyethylene naphthalate.

[0097] The thickness of the substrate can be set to any appropriate thickness depending on the desired strength or flexibility, and the intended use. The substrate thickness is preferably 1000 μm or less, more preferably 25 μm to 1000 μm, further preferably 40 μm to 500 μm, particularly preferably 60 μm to 300 μm, and most preferably 80 μm to 250 μm. In one embodiment, a substrate with a thickness of 25 μm or more is used. Using such a substrate allows the substrate to maintain its shape even under pressure during the sealing process, preventing the semiconductor chip from embedding into the adhesive layer.

[0098] In one embodiment, the thickness of the substrate is 20% to 90% (preferably 20% to 89%, more preferably 20% to 88%) relative to the total thickness of the adhesive sheet. Such a range prevents the semiconductor chip from embedding into the adhesive layer.

[0099] The aforementioned substrate may be subjected to 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 primer-based coating treatment.

[0100] Examples of organic coating materials include those described in Plastic Hard Coating Materials II (CMC Publication, (2004)). Urafra-based polymers are preferred, and polyurethane acrylate, polyester urethane, or precursors thereof are more preferred. This is because coating / applying to the substrate is simple, and a variety of materials are available industrially and inexpensive. The urethane-based polymer is, for example, a polymer formed from a reaction mixture of an isocyanate monomer and a monomer containing an alcoholic hydroxyl group (e.g., a hydroxyl-containing acrylic compound or a hydroxyl-containing ester compound). The organic coating material may contain chain extenders such as polyamines, anti-aging agents, oxidation stabilizers, etc., as optional additives. The thickness of the organic coating layer is not particularly limited, but is suitable for 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.

[0101] D. Second adhesive layer

[0102] 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.

[0103] The adhesive contained 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-based adhesives. Details of the adhesive contained in the second adhesive layer can be found in Japanese Patent Application Publication No. 2018-009050. The entire contents of that publication are incorporated herein by reference.

[0104] As the aforementioned thermally expandable microspheres, any suitable thermally expandable microspheres can be used, as long as they are capable of expanding or foaming upon heating. For example, microspheres containing a substance that readily expands upon heating enclosed in an elastic shell can be used. Such thermally expandable microspheres can be manufactured using any suitable method, such as the coacervate method, interfacial polymerization, etc.

[0105] 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.

[0106] Examples of materials constituting the aforementioned shell include polymers composed of nitrile monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethoxyacrylonitrile, and fumaric acid; 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; and amide monomers such as acrylamide, substituted acrylamide, methacrylamide, and substituted methacrylamide. 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.

[0107] 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: chlorofluorocarbon compounds such as trichloromonofluoromethane and dichloromonofluoromethane; azo compounds such as azobisisobutyronitrile, azodicarbonamide, and barium azodicarbonate; hydrazine compounds such as p-toluenesulfonyl hydrazine, diphenyl sulfone-3,3′-disulfonyl 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.

[0108] The aforementioned thermally expandable microspheres can also be commercially available products. Specific examples of commercially available thermally expandable microspheres include those manufactured by Matsumoto Oils & Fats Co., Ltd. under the trade name "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), Japan. Products manufactured by Fillite Co., Ltd. under the brand name "Expacel" (grades: 053-40, 031-40, 920-40, 909-80, 930-120), by Kureha Chemical Industry Co., Ltd. under the brand name "DYFOAM" (grades: H750, H850, H1100, S2320D, S2640D, M330, M430, M520), and by Sekisui Chemical Industry Co., Ltd. under the brand name "Advacell" (grades: EML101, EMH204, EHM301, EHM302, EHM303, EM304, EHM401, EM403, EM501), etc.

[0109] 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, if the average particle size of the aforementioned thermally expandable microspheres before heating is expressed as the average particle size, it 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 using laser scattering.

[0110] The aforementioned thermally expandable microspheres preferably possess moderate strength that does not break even with 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.

[0111] The content ratio of thermally expandable microspheres in the adhesive layer can be appropriately set according to the desired reduction in adhesive strength, etc. The content ratio of thermally expandable microspheres relative to 100 parts by weight of the base polymer forming the second adhesive layer is, for example, 1 to 150 parts by weight, preferably 10 to 130 parts by weight, and more preferably 25 to 100 parts by weight.

[0112] When the adhesive layer comprises thermally expandable microspheres, the arithmetic mean 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. 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 setting the thickness of the adhesive layer to the above range, or by coating the adhesive layer onto a release liner and transferring it when other adhesive layers are included. It should be noted that, as explained in item A above, when the adhesive sheet of the present invention further includes other adhesive layers, these other adhesive layers may comprise thermally expandable microspheres. When these other adhesive layers comprise thermally expandable microspheres, the arithmetic mean roughness Ra of these adhesive layers is also preferably within the above range.

[0113] When the aforementioned adhesive layer contains thermally expandable microspheres, the adhesive layer preferably comprises an adhesive made of a base polymer with a dynamic storage modulus at 80°C ranging from 5 kPa to 1 MPa (more preferably from 10 kPa to 0.8 MPa). With such an adhesive layer, an adhesive sheet can be formed that exhibits moderate adhesion before heating and whose adhesive strength is easily reduced by heating. 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) under measurement conditions of a frequency of 1 Hz and a heating rate of 10°C / min.

[0114] E. Method for manufacturing adhesive sheets

[0115] The adhesive sheet of the present invention can be manufactured by any suitable method. Examples of methods for manufacturing the adhesive sheet of the present invention include: directly coating a composition comprising an acrylic adhesive onto a substrate; or transferring a coating layer formed by coating a composition comprising an acrylic adhesive onto any suitable substrate to the substrate. The composition comprising the acrylic adhesive may contain any suitable solvent.

[0116] When forming an adhesive layer containing thermally expandable microspheres, the adhesive layer can be formed by coating a composition containing thermally expandable microspheres, an adhesive, and any suitable solvent onto a substrate. Alternatively, the thermally expandable microspheres can be embedded into the adhesive using a laminator or the like after the thermally expandable microspheres are sprinkled onto the adhesive coating layer, thereby forming an adhesive layer containing thermally expandable microspheres.

[0117] As a coating method for the aforementioned adhesives and compositions, any suitable coating method can be employed. For example, drying can be performed after coating to form each layer. Examples of coating methods include those using multi-functional coating machines, die-casting machines, gravure coating machines, applicators, etc. 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.

[0118] Example

[0119] The present invention is illustrated below by way of examples, but the present invention is not limited to these examples. The evaluation methods in the examples are shown below. In addition, in the examples, unless otherwise specified, "parts" and "%" are based on weight.

[0120] (1) T2 relaxation time (T) of the S component of the adhesive layer based on pulsed NMR 2s )

[0121] Using Bruker's "TD-NMR the minispec mq20" product, 100 mg of the adhesive layer was used as the test sample, and the T2 relaxation curve was obtained by solid-state echo method. The T2 relaxation curve was fitted using the following equation (1) to obtain the T2 relaxation time (T) of the S component of the adhesive layer based on pulse NMR. 2s ).

[0122] M(t) = α·exp(-(1 / Wa)(t / T) 2s ) Wa )+β·exp(-(1 / Wa)(t / T 2L ) Wa )···(1)

[0123] M(t): Free induction decay

[0124] α: Proton ratio (%) of the component with short relaxation time (S component)

[0125] T 2s T2 relaxation time (msec) of the S component

[0126] β: Proton ratio (%) of the component with longer relaxation time (L component)

[0127] T 2L T2 relaxation time (msec) of the L component

[0128] t: Observation time (msec)

[0129] Wa: Shape factor (=1)

[0130] The measurement conditions described above are as follows.

[0131] • 90° pulse width: 2.1μsec

[0132] • Repetition time: 1 sec

[0133] • Total number of times: 32

[0134] • Measurement temperature: 30℃

[0135] (2) Indentation measurement at 23°C using TMA.

[0136] The indentation of the first adhesive layer was measured using a TMA Q400 (manufactured by TA-instrument) under the following conditions: probe with needle, nitrogen flow rate: 50.0 ml / min, indentation load: 0.01 N, measurement atmosphere temperature: 23.0 °C, and indentation loading time: 60 min. Measurements were performed with N=5 values, and the average of N=3 values ​​(excluding the maximum and minimum values) was taken as the indentation of the sample.

[0137] (3) Thickness change caused by the addition of 4-tert-butylphenyl glycidyl ether

[0138] A specified amount (0.02 g) of 4-tert-butylphenyl glycidyl ether was dropped onto the surface of the adhesive layer and placed in an environment of 23°C and 50% RH for 1 minute. The thickness change rate ((Dt-It) / It) and the thickness change amount (Dt-It) were calculated based on the thickness (Dt) of the area after the 4-tert-butylphenyl glycidyl ether was wiped off and the thickness (It) of the area before the dropping operation.

[0139] (4) Adhesion (to PET)

[0140] The SUS304 board is attached to the entire side of the adhesive sheet (20mm wide x 140mm long) opposite to the adhesive layer using double-sided adhesive tape (manufactured by Nitto Denko Co., Ltd., trade name "No. 531") and a 2kg hand roller.

[0141] Next, a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S-10", thickness: 25μm, width: 30mm) is applied to the entire surface of the adhesive layer (temperature: 23℃, humidity: 65%, 2kg roller for 1 round trip).

[0142] The evaluation specimens obtained as described above were used for tensile testing. A tensile testing machine manufactured by Shimadzu Corporation, under the trade name "Shimadzu Autograph AG-120kN," was used. After placing the evaluation specimens in the tensile testing machine, the machine was placed at an ambient temperature of 23°C for 30 minutes, and then the tensile test was started. The tensile test conditions were set as follows: peel angle: 180°, peel speed (tensile speed): 300 mm / min. The load at which the adhesive sheet was peeled from the PET film was measured, and the maximum load at this point was taken as the adhesive force of the adhesive sheet.

[0143] (5) Adhesion (to sealant)

[0144] A template (mold size: 35mm × 90mm rectangle, thickness: 564μm) is attached to the first adhesive layer of the adhesive sheet (width 50mm × length 140mm). Granular epoxy resin sealant (manufactured by Sumitomo Bakelite Co., Ltd., G730) is sprinkled inside the template to achieve a cured resin thickness of 0.3mm. Then, an organosilicon-treated release liner is applied. Using a Meisho-press Co., Ltd. "Hydraulic forming machine NS-VPF-50", the sealant is heated and formed on the adhesive layer under the following conditions: temperature 145°C, forming time 600 seconds, pressure 0.3MPa (300mm□ table size), vacuum time 600 seconds, and vacuum degree -0.1MPa.

[0145] Then, the sealant was cured in an oven at 150°C for 7 hours. After the sealant was cured, the sample was left to stand at 23°C and 50% RH for 2 hours, and then the portion of the sealant in contact with the first adhesive layer was cut into pieces 20 mm wide and 88 mm long.

[0146] The evaluation specimens obtained as described above were subjected to tensile testing. A tensile testing machine manufactured by Shimadzu Corporation, under the trade name "Shimadzu Autograph AG-120kN," was used. After placing the evaluation specimens in the tensile testing machine, the machine was placed at an ambient temperature of 23°C for 30 minutes, and then the tensile test was started. The tensile test conditions were set as follows: peel angle: 180°, peel speed (tensile speed): 300 mm / min. The load at which the adhesive sheet was peeled from the sealing resin was measured, and the average load at this point was taken as the adhesive force of the adhesive sheet.

[0147] (6) Height difference between semiconductor chip and sealing resin

[0148] Under the conditions described below, a sealing process is performed on the adhesive surface of the adhesive tape, and the height difference (stand-off) between the semiconductor chip (Si chip) and the sealing resin interface is measured.

[0149] Vehicle: SUS-made vehicle, 220mm Φ

[0150] Chip: Si mirror-finish chip, 7mm × 7mm × 400μm thickness

[0151] Connection device: FC3000W (manufactured by TORAY ENGINEERING Co., Ltd.)

[0152] Connection conditions: as shown below

[0153] Crimping time: 6 seconds

[0154] Crimping pressure: 10N

[0155] Crimping temperature: 23℃

[0156] Sealing equipment: MS-150HP (manufactured by APIC YAMADA CORPORATION)

[0157] Sealing resin: G730 (Sumitomo Bakelite)

[0158] Preheating conditions: 130℃ × 30 seconds

[0159] Preheating to sealing start time: 1 hour

[0160] Sealing temperature: 145℃

[0161] Vacuum time: 5 seconds

[0162] Sealing time: 600 seconds

[0163] Clamping force: 3.6MPa

[0164] Sealing thickness: 600μm

[0165] The sealing operation shall be carried out in accordance with the following steps.

[0166] 1) Apply adhesive tape to the SUS vehicle.

[0167] Adhesion conditions: 23℃ atmosphere

[0168] Pressure required for bonding cylinder: 0.1 MPa

[0169] Pasting speed: 0.5m / min

[0170] The SUS bonding surface is set as the outer surface of the second adhesive layer.

[0171] When the adhesive sheet is a single-sided tape (without a second adhesive layer), the SUS carrier is fixed to the single-sided tape using a substrate-free adhesive layer containing thermally expandable microspheres of 48 μm and the evaluation is carried out. The substrate-free adhesive layer containing thermally expandable microspheres is made using a silicone release liner (MRF38, manufactured by Mitsubishi Chemical) with a PET film thickness of 38 μm and a silicone release liner (PET-75-SCA0, manufactured by FUJICO) with a PET film thickness of 75 μm.

[0172] 2) On the adhesive layer of the adhesive sheet attached to the SUS carrier, a Si mirror chip is configured as one chip using a bonding device.

[0173] 3) Preheat the SUS carrier with the Si mirror chip attached for a specified time.

[0174] 4) After preheating, allow the mixture to stand at 23°C and 50% RH for 1 hour, then perform the sealing using the specified sealing equipment, resin, and conditions. Apply the sealing resin to the SUS carrier by hand and perform the sealing operation.

[0175] 5) Use an oven to heat and cure the laminate obtained from the sealing operation at 150°C for 4 hours.

[0176] 6) After the heat-cured laminate is placed in an environment of 23°C and 50% RH for 5 days, the laminate is heated on a hot plate to cause the adhesive bonded to the SUS carrier to foam and peel off, thus separating the SUS carrier.

[0177] 7) Peel off the adhesive tape from the laminate after separating the SUS carrier to obtain a sealant containing the sealing resin and the Si chip.

[0178] 8) Using a laser confocal microscope (OLS-4000OLYMPUS), the height difference between the interface between the sealing resin and the Si chip, and the surface of the sealing body in contact with the adhesive, was measured.

[0179] [Example 1]

[0180] A composition for forming an adhesive layer is prepared by mixing 100 parts by weight of acrylic copolymer A (a copolymer of 2-ethylhexyl acrylate and acrylic acid, with 2-ethylhexyl acrylate structural units: acrylic acid structural units = 95:5 (weight ratio)), 5 parts by weight of epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "TETRAD C"), and 100 parts by weight of toluene.

[0181] The adhesive layer forming composition was coated on one side of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) serving as a substrate, to obtain an adhesive sheet (1) consisting of a substrate and a first adhesive layer (thickness 10 μm).

[0182] On the side of the polyethylene terephthalate film of the adhesive sheet (1) opposite to the first adhesive layer, 100 parts by weight of acrylic copolymer C (a copolymer of 2-ethylhexyl acrylate, ethyl acrylate, methyl methacrylate and 2-hydroxyethyl acrylate, 2-ethylhexyl acrylate structural unit: ethyl acrylate structural unit: methyl methacrylate structural unit: acrylic structural unit = 30:70:5:4 (weight ratio)), 30 parts by weight of thermally expandable microspheres (manufactured by Matsumoto Oils & Fats Co., Ltd., trade name "Matsumoto mircosphere F-190D"), 1.4 parts by weight of isocyanate crosslinking agent (manufactured by Tosoh Co., Ltd., trade name "CORONATE L"), and tackifier (manufactured by YASUHARA CHEMICAL CO.,LTD., trade name "Mightyace") are coated. An adhesive layer forming composition is prepared by mixing 10 parts by weight of G125” and 100 parts by weight of toluene, forming a second adhesive layer (thickness 45 μm) to obtain a double-sided adhesive sheet.

[0183] [Example 2]

[0184] A composition for forming an adhesive layer is prepared by mixing 100 parts by weight of acrylic copolymer A (a copolymer of 2-ethylhexyl acrylate and acrylic acid, with 2-ethylhexyl acrylate structural units: acrylic acid structural units = 95:5 (by weight)), 5 parts by weight of epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "TETRAD C"), 10 parts by weight of tackifier (manufactured by YASUHARA CHEMICAL CO.,LTD., trade name "Mightyace G125"), and 100 parts by weight of toluene.

[0185] The adhesive layer forming composition was coated on one side of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) as a substrate, to obtain an adhesive sheet (2) consisting of a substrate and a first adhesive layer (thickness 10 μm).

[0186] In the same manner as in Example 1, a second adhesive layer is formed on the side of the polyethylene terephthalate film of the adhesive sheet (2) opposite to the first adhesive layer, to obtain a double-sided adhesive sheet.

[0187] [Example 3]

[0188] A composition for forming an adhesive layer is prepared by mixing 100 parts by weight of acrylic copolymer B (a copolymer of ethyl acrylate, butyl acrylate, acrylic acid and 2-hydroxyethyl acrylate, with ethyl acrylate structural unit: butyl acrylate structural unit: acrylic acid structural unit: hydroxyethyl acrylate structural unit = 50:50:5:0.1 (weight ratio)), 5 parts by weight of epoxy crosslinking agent (manufactured by Mitsubishi Gas Chemical Co., Ltd., trade name "TETRAD C"), 10 parts by weight of tackifier (manufactured by YASUHARA CHEMICAL CO.,LTD., trade name "Mightyace G125"), and 100 parts by weight of toluene.

[0189] The adhesive layer forming composition was coated on one side of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) serving as a substrate, to obtain an adhesive sheet (3) consisting of a substrate and a first adhesive layer (thickness 10 μm).

[0190] In the same manner as in Example 1, a second adhesive layer is formed on the side of the polyethylene terephthalate film of the adhesive sheet (3) opposite to the first adhesive layer to obtain a double-sided adhesive sheet.

[0191] [Example 4]

[0192] As the substrate, a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 100 μm) was used, otherwise, a double-sided adhesive sheet was obtained in the same manner as in Example 2.

[0193] [Comparative Example 1]

[0194] 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, ethyl acrylate, methyl methacrylate and 2-hydroxyethyl acrylate, wherein the ratio of 2-ethylhexyl acrylate structural unit to ethyl acrylate structural unit to methyl methacrylate structural unit to 2-hydroxyethyl acrylate structural unit is 30:70:5:4 (by weight)), 1.5 parts by weight of an isocyanate crosslinking agent (manufactured by Tosoh Corporation, trade name "CORONATE L"), 5 parts by weight of a tackifier (manufactured by YASUHARA CHEMICAL CO.,LTD., trade name "Mightyace G125"), and 100 parts by weight of toluene.

[0195] The adhesive layer forming composition was coated on one side of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) as a substrate, to obtain an adhesive sheet (4) consisting of a substrate and an adhesive layer (thickness 10 μm).

[0196] In the same manner as in Example 1, a second adhesive layer is formed on the side of the polyethylene terephthalate film of the adhesive sheet (4) opposite to the first adhesive layer to obtain a double-sided adhesive sheet.

[0197] [Comparative Example 2]

[0198] A composition for forming an adhesive layer is prepared by mixing 100 parts by weight of acrylic copolymer D (a copolymer of 2-ethylhexyl acrylate and 2-hydroxyethyl acrylate, with 2-ethylhexyl acrylate structural units: 2-hydroxyethyl acrylate structural units = 100:4 (weight ratio)), 1.5 parts by weight of isocyanate crosslinking agent (manufactured by Tosoh Corporation, trade name "CORONATE L"), and 100 parts by weight of toluene.

[0199] The adhesive layer forming composition was coated on one side of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., trade name "Lumirror S10", thickness 38 μm) serving as a substrate, to obtain an adhesive sheet (5) consisting of a substrate and an adhesive layer (thickness 10 μm).

[0200] In the same manner as in Example 1, a second adhesive layer is formed on the side of the polyethylene terephthalate film of the adhesive sheet (5) opposite to the first adhesive layer to obtain a double-sided adhesive sheet.

[0201] [Table 1]

[0202]

[0203] Explanation of reference numerals in the attached figures

[0204] 10 Substrate

[0205] 20 Adhesive layers

[0206] 30 Second adhesive layer

[0207] 100 and 200 adhesive sheets

Claims

1. An adhesive sheet comprising a substrate, an 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. The adhesive layer contains an acrylic adhesive. The acrylic adhesive in the adhesive layer comprises a crosslinked acrylic polymer as the base polymer and an epoxy crosslinking agent. The amount of the epoxy crosslinking agent is 5 to 15 parts by weight relative to 100 parts by weight of the acrylic polymer. The indentation of this adhesive sheet at 23°C using TMA is less than 5 μm. The T2 relaxation time (T2) of the S component of the adhesive layer based on pulsed NMR. 2s The value is below 45 μsec. The second adhesive layer comprises thermally expandable microspheres and an adhesive composed of a base polymer with a dynamic energy storage modulus in the range of 5 kPa to 1 MPa at 80°C. This adhesive sheet is a temporary fixing material used in the resin sealing process of semiconductor chips.

2. The adhesive sheet according to claim 1, wherein, The thickness change rate of the adhesive layer after 4-tert-butylphenyl glycidyl ether is dropped onto the surface of the adhesive layer and left to stand for 1 minute is less than 160%.

3. The adhesive sheet according to claim 1 or 2, wherein, The thickness change of the adhesive layer after adding 4-tert-butylphenyl glycidyl ether to the surface of the adhesive layer and letting it stand for 1 minute is less than 20 μm.

4. The adhesive sheet according to claim 1 or 2, wherein, The adhesive layer contains an adhesive. The adhesive contains an sp value of 18 (cal / cm). 3 ) 1 / 2 ~20 (cal / cm) 3 ) 1 / 2 The basic polymer.

5. The adhesive sheet according to claim 1 or 2, wherein, The substrate is a resin sheet made of resin with a glass transition temperature (Tg) of 25°C or higher.

6. The adhesive sheet according to claim 1 or 2, wherein, The thickness of the substrate is 20% to 90% of the total thickness of the adhesive sheet.

7. The adhesive sheet according to claim 1 or 2, wherein, The indentation of the adhesive sheet at 145°C using TMA is 1μm to 35μm.

8. The adhesive sheet according to claim 1 or 2, wherein, The amount of nitrogen generated during the heat treatment of the adhesive layer is 0.06% to 1.0% by weight.

9. The adhesive sheet according to claim 1 or 2, used when curing a sealing resin onto the adhesive sheet.

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