Adhesive film

Abstract

An adhesive film used in the manufacturing process of an electronic device, the adhesive film having a stress retention rate at 100 °C of 55.0% or less and a stress retention rate at 150 °C of 5.0% or more and 90.0% or less.

Description

Technical Field

[0001] The present invention relates to an adhesive film.

Background Art

[0002] In a method of manufacturing an electronic device, after forming a circuit of an electronic component, a process of performing processing such as back grinding (grinding), ion implantation, laser annealing, sputtering, etc. on the surface opposite to the circuit formation surface of the electronic component is included. In these processes, an adhesive film for protecting the circuit formation surface of the electronic component is used. As a technology related to such an adhesive film, for example, the one described in Patent Document 1 (International Publication No. 2015 / 152010) can be mentioned.

[0003] Patent Document 1 describes a protective film having a polyimide base material and a thermosetting adhesive layer obtained from a composition provided on one surface of the polyimide base material and containing an acrylic polymer (a), a thermal radical generator (b) having a half-life temperature of 140°C or higher and 200°C or lower for 1 minute, and a crosslinking agent (c), and being attached to the circuit formation surface of a semiconductor wafer. Patent Document 1 describes that when applied to a method of manufacturing a semiconductor device including a process performed under vacuum heating while the semiconductor wafer is attached after attaching to the circuit formation surface of the semiconductor wafer and thermosetting the thermosetting adhesive layer, it is possible to provide a protective film that protects the circuit formation surface of the semiconductor wafer, suppresses the occurrence of lifting, and has excellent peelability when peeling from the semiconductor wafer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the manufacturing method of such an electronic device, if the adhesion between the electronic component and the adhesive film is insufficient, water or chemical solution may penetrate between the electronic component and the adhesive film, and the electronic component may deteriorate.

[0006] According to the study by the present inventors, in order to improve the adhesion between the electronic component and the adhesive film and protect the electronic component, when the adhesive film is attached to the circuit formation surface of the electronic component, the adhesive film should follow the unevenness of the circuit formation surface (unevenness followability), and even in a vacuum atmosphere, the adhesive film attached to the electronic component should not float (vacuum resistance).

[0007] Furthermore, according to the study by the present inventors, in order to improve the unevenness followability, a method of making the adhesive film flexible can be adopted, but it has been clarified that the adhesive film is likely to deform and float from the electronic component in a vacuum atmosphere. On the other hand, in order to improve the vacuum resistance, a method of making the adhesive film hard can be adopted, but it has been clarified that the unevenness followability when attaching to the electronic component is insufficient. That is, it has been found that the unevenness followability and the vacuum resistance of the adhesive film are in a trade-off relationship.

[0008] The present invention has been made in view of the above circumstances, and provides an adhesive film with an improved performance balance of unevenness followability and vacuum resistance.

Means for Solving the Problems

[0009] According to the present invention, the following adhesive film is provided.

[0010] [1] An adhesive film used in the manufacturing process of an electronic device, The stress residual rate at 100 °C calculated by the following method 1 is 55.0% or less, An adhesive film having a stress residual rate at 150 °C calculated by the following method 2 of 5.0% or more and 90.0% or less. [Method 1] The adhesive film is laminated until it reaches a thickness of 1.4 ± 0.1 mm to produce a measurement sample. For the measurement sample cut to a width of 10 mm, using a dynamic viscoelasticity measuring device, at a temperature of 100°C, deformation mode: compression, upper jig: three-point bending (tip of the indenter: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen, the stress when continuously applying a strain of 2% is measured, and the value calculated by the formula of "(stress [Pa] at 600 seconds / stress [Pa] at the time when the maximum stress was measured) × 100" is defined as the stress residual rate [%] at 100°C. [Method 2] For the sample obtained by laminating the adhesive film until it reaches a thickness of 1.4 ± 0.1 mm, a measurement sample is produced by performing heat treatment under the conditions of 130°C for 30 minutes. For the measurement sample cut to a width of 10 mm, using a dynamic viscoelasticity measuring device, at a temperature of 150°C, deformation mode: compression, upper jig: three-point bending (tip of the indenter: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen, the stress when continuously applying a strain of 2% is measured, and the value calculated by the formula of "(stress [Pa] at 600 seconds / stress [Pa] at the time when the maximum stress was measured) × 100" is defined as the stress residual rate [%] at 150°C. [2] The adhesive film according to [1] above, comprising a base material layer, an unevenness-absorbing resin layer, and a thermosetting adhesive layer in this order. [3] The adhesive film according to [2] above, wherein the unevenness-absorbing resin layer and the thermosetting adhesive layer are provided so as to be in direct contact with each other. [4] The adhesive film according to [2] or [3] above, wherein the thermosetting adhesive layer contains a (meth)acrylic resin and a thermal polymerization initiator. [5] The adhesive film according to any one of [2] to [4] above, wherein the resin constituting the unevenness-absorbing resin layer contains at least one selected from the group consisting of ethylene-vinyl acetate copolymer, (meth)acrylic resin, ethylene-α-olefin copolymer, and low-density polyethylene. [6] The adhesive film according to any one of [2] to [5], wherein the uneven-absorbing resin layer has a thickness of 20 μm or more and 500 μm or less. [7] The adhesive film according to any one of [2] to [6], wherein the resin constituting the base material layer contains at least one selected from the group consisting of polyethylene naphthalate, polyethylene terephthalate, and polyimide. [8] The manufacturing process of the electronic device includes: a step (A) of preparing a structure including an electronic component having a circuit formation surface and the adhesive film bonded to the circuit formation surface side of the electronic component; and a step (B) of processing the surface on the side opposite to the circuit formation surface side of the electronic component in a vacuum atmosphere. The adhesive film according to any one of [1] to [7]. [9] The adhesive film according to any one of [1] to [8], wherein the electronic device is a power semiconductor device.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide an adhesive film with an improved performance balance of uneven-following property and vacuum resistance.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by common reference numerals, and the description thereof will be omitted as appropriate. The drawings are schematic views and do not match the actual dimensional ratios. Also, the numerical range "A to B" represents A or more and B or less unless otherwise specified. In the present embodiment, "(meth)acrylic" means acrylic, methacrylic, or both acrylic and methacrylic.

[0014] <Adhesive film> The adhesive film of the present embodiment is an adhesive film used in the manufacturing process of electronic devices, and is an adhesive film having a stress relaxation rate at 100 °C of 55.0% or less and a stress relaxation rate at 150 °C of 5.0% or more and 90.0% or less. Here, the stress relaxation rate at 100 °C means a value calculated by the following Method 1. The stress relaxation rate at 150 °C means a value calculated by the following Method 2. [Method 1] The adhesive film is laminated until the thickness becomes 1.4 ± 0.1 mm to prepare a measurement sample. For the measurement sample cut to a width of 10 mm, using a dynamic viscoelasticity measuring device, at a temperature of 100 °C, a deformation mode of compression, an upper jig of three-point bending (indenter tip: 2.5R), a lower jig of a parallel plate, a measurement time of 1000 seconds, and an atmosphere of nitrogen, the stress when a strain of 2% is continuously applied is measured, and the value calculated by the formula "(stress [Pa] at 600 seconds / stress [Pa] at the time when the maximum stress is measured) × 100" is taken as the stress relaxation rate [%] at 100 °C. [Method 2] For a sample in which an adhesive film is laminated until it reaches a thickness of 1.4 ± 0.1 mm, a measurement sample is prepared by performing heat treatment under the conditions of 130°C for 30 minutes. For the measurement sample cut to a width of 10 mm, using a dynamic viscoelasticity measuring device, at a temperature of 150°C, a deformation mode of compression, an upper jig of three-point bending (tip of the indenter: 2.5R), a lower jig of a parallel plate, a measurement time of 1000 seconds, and an atmosphere of nitrogen, the stress when continuously applying a strain of 2% is measured, and the value calculated by the formula “(stress [Pa] at 600 seconds / stress [Pa] at the time when the maximum stress is measured) × 100” is defined as the stress residual rate [%] at 150°C.

[0015] As described above, for the adhesive film used in the manufacturing process of conventional electronic devices, there was a trade-off relationship between the unevenness followability and the vacuum resistance. The inventors of the present invention have intensively studied to achieve the above problems. As a result, they obtained the knowledge that the scales of the stress residual rate at 100°C and the stress residual rate at 150°C of the adhesive film are effective as design indices for improving the performance balance between the unevenness followability and the vacuum resistance. As described above, according to the adhesive film of the present embodiment, it is possible to improve the performance balance between the unevenness followability and the vacuum resistance.

[0016] The adhesive film of the present embodiment is an adhesive film having a stress residual rate at 100°C of 55.0% or less and a stress residual rate at 150°C of 5.0% or more and 90.0% or less. From the viewpoint of further improving the unevenness followability of the adhesive film, the stress residual rate at 100°C of the adhesive film of the present embodiment is preferably 50.0% or less, more preferably 45.0% or less, still more preferably 40.0% or less, still more preferably 35.0% or less, still more preferably 30.0% or less, still more preferably 28.0% or less, and the lower limit value is not particularly limited, but may be, for example, 1.0% or more or 2.0% or more. From the perspective of further improving the vacuum resistance of the pressure-sensitive adhesive film, the stress residual rate of the pressure-sensitive adhesive film of the present embodiment at 150°C is preferably 8.0% or more, more preferably 10.0% or more, still more preferably 12.0% or more, and still more preferably 14.0% or more. From the perspective of further improving the performance balance between the unevenness followability and vacuum resistance of the pressure-sensitive adhesive film, it is preferably 87.0% or less, more preferably 85.0% or less, still more preferably 83.0% or less, and still more preferably 81.0% or less. The stress residual rate of the pressure-sensitive adhesive film of the present embodiment at 100°C and the stress residual rate at 150°C can be controlled by, for example, the layer structure of the pressure-sensitive adhesive film, the thickness and material of each layer, etc. Specifically, it can be controlled by the resin used in the unevenness absorbing resin layer, the thermal polymerization initiator contained in the thermosetting pressure-sensitive adhesive layer, etc.

[0017] From the perspective of further improving the handleability of the pressure-sensitive adhesive film, the thickness of the entire pressure-sensitive adhesive film of the present embodiment is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 40 μm or more, still more preferably 60 μm or more, still more preferably 80 μm or more, and still more preferably 100 μm or more. From the perspective of further improving the unevenness followability of the pressure-sensitive adhesive film, it is preferably 700 μm or less, more preferably 500 μm or less, still more preferably 300 μm or less, still more preferably 250 μm or less, and still more preferably 200 μm or less.

[0018] The layer structure of the pressure-sensitive adhesive film of the present embodiment is not particularly limited and may be a single-layer structure or a multi-layer structure, but a multi-layer structure is preferred. FIG. 1 is a cross-sectional view schematically showing a preferred layer structure of the pressure-sensitive adhesive film according to the embodiment of the present invention. As shown in FIG. 1, the pressure-sensitive adhesive film 50 of the present embodiment preferably includes a base material layer 20, an unevenness absorbing resin layer 30, and a thermosetting pressure-sensitive adhesive layer 40 in this order, and more preferably, the unevenness absorbing resin layer 30 and the thermosetting pressure-sensitive adhesive layer 40 are provided so as to be in direct contact with each other.

[0019] Hereinafter, each layer constituting the adhesive film 50 of the present embodiment will be described.

[0020] [Base material layer] The base material layer 20 is a layer provided for the purpose of making the performance balance such as the handleability, mechanical properties, and heat resistance of the adhesive film 50 better. The base material layer 20 is not particularly limited, and examples thereof include resin films. The resin constituting the base material layer 20 preferably contains at least one selected from the group consisting of polyethylene naphthalate, polyethylene terephthalate, and polyimide, and more preferably contains polyethylene naphthalate from the viewpoint of further improving the vacuum resistance.

[0021] The base material layer 20 may be a single layer or two or more layers. Also, as the form of the resin film used to form the base material layer 20, an unstretched film or a film stretched in one axial direction or two axial directions may be used.

[0022] From the viewpoint of further improving the handleability of the adhesive film 50, the thickness of the base material layer 20 is preferably 10 μm or more, more preferably 20 μm or more, still more preferably 30 μm or more, still more preferably 40 μm or more, and from the viewpoint of further improving the unevenness followability of the adhesive film 50, it is preferably 500 μm or less, more preferably 300 μm or less, still more preferably 200 μm or less, still more preferably 100 μm or less, still more preferably 80 μm or less, still more preferably 60 μm or less.

[0023] The base material layer 20 may be surface-treated to further improve the adhesiveness with other layers. Specifically, corona treatment, plasma treatment, undercoat treatment, primer coat treatment, etc. may be performed.

[0024] [Unevenness absorbing resin layer] The uneven-absorbing resin layer 30 is a layer provided to further improve the performance balance between the uneven-following property and the vacuum resistance of the adhesive film 50.

[0025] The resin constituting the uneven-absorbing resin layer 30 preferably contains at least one selected from the group consisting of ethylene-vinyl acetate copolymer, (meth)acrylic resin, ethylene-α-olefin copolymer, and low-density polyethylene, more preferably contains one or two selected from the group consisting of ethylene-vinyl acetate copolymer and (meth)acrylic resin, and even more preferably contains ethylene-vinyl acetate copolymer.

[0026] The ethylene-vinyl acetate copolymer of the present embodiment is a copolymer of ethylene and vinyl acetate, and is, for example, a random copolymer. From the viewpoint of further improving the performance balance between the uneven-following property and the vacuum resistance of the adhesive film 50, the content ratio of the structural unit derived from vinyl acetate in the ethylene-vinyl acetate copolymer is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, and from the viewpoint of further improving the performance balance between the uneven-following property and the vacuum resistance of the adhesive film 50, it is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, even more preferably 35% by mass or less, even more preferably 30% by mass or less, and even more preferably 25% by mass or less. The vinyl acetate content can be measured in accordance with JIS K7192:1999.

[0027] In addition, the ethylene-vinyl acetate copolymer is preferably a binary copolymer composed only of ethylene and vinyl acetate. However, in addition to ethylene and vinyl acetate, for example, vinyl ester monomers such as vinyl formate, vinyl glycolate, vinyl propionate, vinyl benzoate, etc.; acrylic monomers such as acrylic acid, methacrylic acid, ethacrylic acid, or salts or alkyl esters thereof; etc. At least one selected from the group may be included as a copolymerization component. When a copolymerization component other than ethylene and vinyl acetate is included, the amount of the copolymerization component other than ethylene and vinyl acetate in the ethylene-vinyl acetate copolymer is preferably 0.5% by mass or more and 5% by mass or less.

[0028] The melt flow rate (MFR) of the ethylene-vinyl acetate copolymer, measured under the conditions of 190 °C and a load of 2.16 kg in accordance with JIS K7210:1999, is preferably 0.1 g / 10 min or more, more preferably 0.5 g / 10 min or more, still more preferably 1.0 g / 10 min or more, still more preferably 1.5 g / 10 min or more, still more preferably 2.0 g / 10 min or more from the viewpoint of further improving the moldability of the unevenness-absorbing resin layer 30, and is preferably 50 g / 10 min or less, more preferably 40 g / 10 min or less, still more preferably 20 g / 10 min or less, still more preferably 10 g / 10 min or less, still more preferably 5.0 g / 10 min or less, still more preferably 3.0 g / 10 min or less from the viewpoint of further improving the storage stability of the adhesive film 50.

[0029] The ethylene-α-olefin copolymer of the present embodiment is, for example, a copolymer obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms. As the α-olefin, for example, an α-olefin having 3 to 20 carbon atoms can be used alone or in combination of two or more. Preferably, it is an α-olefin having 3 to 10 carbon atoms, and more preferably, it is an α-olefin having 3 to 8 carbon atoms. Specific examples of the α-olefin include propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3,3-dimethyl-1-butene, 4-methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, etc. Among them, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and 1-octene are preferred from the viewpoint of easy availability. The ethylene-α-olefin copolymer may be a random copolymer or a block copolymer, but a random copolymer is preferred from the viewpoint of flexibility.

[0030] From the viewpoint of further improving the storage stability of the pressure-sensitive adhesive film 50, the melting point of the resin constituting the unevenness-absorbing resin layer 30 is preferably 40 °C or higher, more preferably 50 °C or higher, still more preferably 60 °C or higher, still more preferably 70 °C or higher, still more preferably 80 °C or higher. And from the viewpoint of further improving the unevenness followability of the pressure-sensitive adhesive film 50, it is preferably 100 °C or lower, more preferably 95 °C or lower, more preferably 90 °C or lower, still more preferably 85 °C or lower. When there are two or more kinds of resins constituting the unevenness-absorbing resin layer 30, the melting point of the resin constituting the unevenness-absorbing resin layer 30 is the peak temperature of the maximum melting peak by DSC measurement.

[0031] The unevenness-absorbing resin layer 30 can be obtained, for example, by dry blending or melt kneading a resin and an additive to obtain a resin composition, and then subjecting the resin composition to extrusion molding, coating and drying, etc. The additive may be added as necessary. Specific examples of the additive include a crosslinking agent, an antioxidant, etc.

[0032] When the content of the thermal polymerization initiator contained in the resin composition for forming the concavo-convex absorbent resin layer 30 is based on 100 parts by mass of the entire resin composition for forming the concavo-convex absorbent resin layer 30, it is preferably less than 0.3 parts by mass, more preferably less than 0.1 parts by mass, still more preferably less than 0.01 parts by mass, and even more preferably 0.00 parts by mass. When the content of the thermal polymerization initiator contained in the resin composition for forming the concavo-convex absorbent resin layer 30 is less than the above upper limit value, the moldability can be further improved when the concavo-convex absorbent resin layer 30 is extrusion-molded, and the concavo-convex followability of the adhesive film 50 can be further improved. Note that the thermal polymerization initiator means the same as the thermal polymerization initiator contained in the thermosetting adhesive layer described later.

[0033] The layer in direct contact with the concavo-convex absorbent resin layer 30 preferably contains a thermal polymerization initiator. When the layer in direct contact with the concavo-convex absorbent resin layer 30 contains a thermal polymerization initiator, the vacuum resistance of the adhesive film 50 is further improved. Although the exact mechanism is unknown, the inventors consider that in the manufacturing process of the electronic device, when the temperature of the adhesive film 50 bonded to the electronic component becomes high (for example, 150 ° C or higher), the thermal polymerization initiator contained in the layer in direct contact with the concavo-convex absorbent resin layer 30 diffuses into the concavo-convex absorbent resin layer 30, the resin constituting the concavo-convex absorbent resin layer 30 hardens, the entire adhesive film 50 becomes hard, and the adhesive film 50 bonded to the electronic component is less likely to float.

[0034] From the viewpoint of further improving the handleability of the adhesive film 50, the thickness of the concavo-convex absorbent resin layer 30 is preferably 20 μm or more, more preferably 30 μm or more, and from the viewpoint of further improving the performance balance between the concavo-convex followability and the vacuum resistance of the adhesive film 50, it is preferably 500 μm or less, more preferably 300 μm or less, still more preferably 200 μm or less, and even more preferably 150 μm or less.

[0035] [Thermosetting Adhesive Layer] The thermosetting adhesive layer 40 is a layer provided for bonding the adhesive film 50 to the circuit formation surface of the electronic component. The thermosetting adhesive layer 40 can be composed of, for example, a known adhesive, and preferably contains a (meth)acrylic resin and a thermal polymerization initiator.

[0036] Examples of the resin contained in the thermosetting adhesive layer 40 include (meth)acrylic resins, silicone resins, urethane resins, olefin resins, and styrene resins. Among these, it is preferable to use a (meth)acrylic resin as the base polymer in terms of easy adjustment of the adhesive strength.

[0037] Examples of the (meth)acrylic resin of the present embodiment include a homopolymer of a (meth)acrylic acid ester compound, a copolymer of a (meth)acrylic acid ester compound and a comonomer, and the like. Examples of the (meth)acrylic acid ester compound include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, and the like. These (meth)acrylic acid ester compounds may be used alone or in combination of two or more. Examples of the comonomer constituting the (meth)acrylic copolymer include vinyl acetate, (meth)acrylonitrile, styrene, (meth)acrylic acid, itaconic acid, (meth)acrylamide, methylol (meth)acrylamide, maleic anhydride, and the like. These comonomers may be used alone or in combination of two or more.

[0038] The thermosetting adhesive layer 40 preferably contains a thermal polymerization initiator. The thermal polymerization initiator of the present embodiment is, for example, at least one selected from the group consisting of a thermal radical polymerization initiator, a thermal cationic polymerization initiator, and a thermal anionic polymerization initiator, and is preferably a thermal radical polymerization initiator.

[0039] The thermal radical polymerization initiator of this embodiment is, for example, at least one selected from the group consisting of peroxides and azo compounds, and is preferably a peroxide. The peroxide of this embodiment preferably contains at least one selected from the group consisting of 1,1 - di(t - butylperoxy)-2 - methylcyclohexane, 1,1 - di(t - butylperoxy)-cyclohexane, 2,2 - di(4,4 - di-(t - butylperoxy)cyclohexyl)propane, t - butyl peroxymaleic acid, t - butyl peroxy - 3,3,5 - trimethylhexanoate, t - butyl peroxylaurate, t - butyl peroxyisopropyl monocarbonate, t - butyl peroxy - 2 - ethylhexyl monocarbonate, t - hexyl peroxybenzoate, t - butyl peroxyacetate, 2,2 - di(t - butylperoxy)butane, t - butyl peroxybenzoate, n - butyl - 4,4 - di-(t - butylperoxy)valerate, di(2 - t - butylperoxyisopropyl)benzene, dicumyl peroxide, 2,5 - dimethyl - 2,5 - di(t - butylperoxy)hexane, t - butyl cumyl peroxide, di - t - butyl peroxide, 2,5 - dimethyl - 2,5 - di(t - butylperoxy)-3 - hexyne.

[0040] The peroxide of this embodiment preferably contains at least one structure selected from the group consisting of the following formula (I) and the following formula (II) in the molecule, and more preferably contains the structure of the following formula (II) in the molecule.

[0041]

Chemical formula

[0042] In formula (I), the wavy line indicates the bonding point.

[0043]

Chemical formula

[0044] In formula (II), the wavy line indicates the bonding point.

[0045] The 1-minute half-life temperature of the thermal radical polymerization initiator of the present embodiment is preferably 140°C or higher, more preferably 145°C or higher, still more preferably 150°C or higher, and preferably 200°C or lower, more preferably 195°C or lower, still more preferably 190°C or lower, still more preferably 185°C or lower, still more preferably 180°C or lower. When the 1-minute half-life temperature of the thermal radical polymerization initiator is at or above the above lower limit value, it is difficult for the thermal radical polymerization initiator to thermally decompose when forming the thermosetting adhesive layer 40 in the manufacturing process of the adhesive film 50, and the uneven followability of the adhesive film 50 is further improved, which is preferable. When the 1-minute half-life temperature of the thermal radical polymerization initiator is at or below the above upper limit value, the thermal radical polymerization initiator decomposes at a temperature lower than the temperature at which the resin contained in the adhesive film 50 is excessively softened, so that the vacuum resistance of the adhesive film 50 is further improved, which is preferable.

[0046] The hydrogen abstraction ability of the thermal radical polymerization initiator of the present embodiment is preferably 20% or higher, more preferably 25% or higher, still more preferably 30% or higher, and the upper limit value is not particularly limited, but it may be 90% or lower or 80% or lower. When the hydrogen abstraction ability of the thermal radical polymerization initiator of the present embodiment is at or above the above lower limit value, the resin contained in the adhesive film 50 is more likely to be crosslinked, and the vacuum resistance of the adhesive film 50 is further improved, which is preferable. Here, the hydrogen abstraction ability means a value calculated by a radical trapping method using α-methylstyrene dimer as a radical trapping agent. More specifically, first, a thermal radical polymerization initiator is decomposed in the coexistence of α-methylstyrene dimer and cyclohexane. Among the radicals generated from the thermal radical polymerization initiator, radicals with weak hydrogen abstraction ability are trapped by the α-methylstyrene dimer. On the other hand, radicals with strong hydrogen abstraction ability abstract hydrogen from cyclohexane to generate cyclohexyl radicals. The cyclohexyl radicals are trapped by the α-methylstyrene dimer and led to the trapping products of cyclohexyl radicals. The hydrogen abstraction ability is the ratio (mole fraction) of the amount of the trapping products of cyclohexyl radicals to the theoretically generated radical amount.

[0047] When the content of the (meth)acrylic resin contained in the thermosetting adhesive layer 40 is 100 parts by mass, the content of the thermal polymerization initiator contained in the thermosetting adhesive layer 40 is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, still more preferably 0.5 part by mass or more from the viewpoint of further improving the vacuum resistance of the pressure-sensitive adhesive film 50, and preferably 2.0 parts by mass or less, more preferably 1.8 parts by mass or less, still more preferably 1.5 parts by mass or less from the viewpoint of further improving the unevenness followability of the pressure-sensitive adhesive film 50. Here, the content of the thermal polymerization initiator contained in the thermosetting adhesive layer 40 means the content of the thermal polymerization initiator in the adhesive for forming the thermosetting adhesive layer 40. That is, the content of the thermal polymerization initiator in this specification means the charged amount when forming the thermosetting adhesive layer 40. The contents of the crosslinking agent and the polyfunctional acrylate described later also mean the charged amount in the same manner as the thermal polymerization initiator.

[0048] The thermosetting adhesive layer 40 may contain a crosslinking agent. Examples of the crosslinking agent in this embodiment include epoxy compounds such as sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, and diglycerol polyglycidyl ether; aziridine compounds such as tetramethylolmethane-tri-β -aziridinylpropionate, trimethylolpropane-tri-β -aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), and N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide); and isocyanate compounds such as tetramethylene diisocyanate, hexamethylene diisocyanate, and polyisocyanate.

[0049] When the content of the (meth)acrylic resin contained in the thermosetting adhesive layer 40 is 100 parts by mass, the content of the crosslinking agent contained in the thermosetting adhesive layer 40 is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, still more preferably 0.5 part by mass or more, still more preferably 1.0 part by mass or more, still more preferably 1.5 part by mass or more, still more preferably 2.0 part by mass or more, still more preferably 2.3 part by mass or more, from the viewpoint of further improving the performance balance of the uneven followability and vacuum resistance of the pressure-sensitive adhesive film 50. And from the viewpoint of further improving the performance balance of the uneven followability and vacuum resistance of the pressure-sensitive adhesive film 50, it is preferably 10.0 parts by mass or less, more preferably 7.0 parts by mass or less, still more preferably 5.0 parts by mass or less, still more preferably 4.0 parts by mass or less, still more preferably 3.0 parts by mass or less.

[0050] In addition to the (meth)acrylic resin, the thermosetting adhesive layer 40 may further contain a polyfunctional acrylate. The polyfunctional acrylate in this embodiment is an acrylate having two or more radically reactive double bonds. Examples of the polyfunctional acrylate of the present embodiment include urethane acrylate, epoxy acrylate, polyester acrylate, polyether acrylate, pentaerythritol polyacrylate, dipentaerythritol polyacrylate, ethoxylated isocyanuric acid triacrylate, trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate, and the like.

[0051] When the content of the polyfunctional acrylate contained in the thermosetting adhesive layer 40 is based on 100 parts by mass of the content of the (meth)acrylic resin contained in the thermosetting adhesive layer 40, from the viewpoint of further improving the performance balance of the uneven followability and vacuum resistance of the pressure-sensitive adhesive film 50, it is preferably 2.0 parts by mass or more, more preferably 3.0 parts by mass or more, still more preferably 4.0 parts by mass or more, and from the viewpoint of further improving the performance balance of the uneven followability and vacuum resistance of the pressure-sensitive adhesive film 50, it is preferably 20.0 parts by mass or less, more preferably 15.0 parts by mass or less, still more preferably 12.0 parts by mass or less.

[0052] The thickness of the thermosetting adhesive layer 40 is not particularly limited, but is preferably 1 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, still more preferably 15 μm or more, and preferably 100 μm or less, more preferably 50 μm or less, still more preferably 30 μm or less, still more preferably 25 μm or less.

[0053] The thermosetting adhesive layer 40 can be formed, for example, by applying an adhesive coating solution on the unevenness-absorbing resin layer 30. As a method for applying the adhesive coating solution, conventionally known coating methods such as a roll coater method, a reverse roll coater method, a gravure roll method, a bar coating method, a comma coater method, a die coater method, etc. can be adopted. There is no particular limitation on the drying conditions of the applied adhesive, but generally, it is preferably dried in the temperature range of 80 to 200 °C for 10 seconds to 10 minutes. More preferably, it is dried at 80 to 170 °C for 15 seconds to 5 minutes.

[0054] [Other Layers] The adhesive film 50 may be provided with an adhesive layer between each layer. According to this adhesive layer, the adhesiveness between each layer can be improved.

[0055] An example of the manufacturing method of the adhesive film 50 according to the present embodiment will be described. First, the unevenness-absorbing resin layer 30 is formed on one surface of the base material layer 20 by extrusion molding. Next, a thermosetting adhesive layer 40 is formed by applying and drying an adhesive coating liquid on the unevenness-absorbing resin layer 30, and the adhesive film 50 is obtained.

[0056] Next, the manufacturing method of the electronic device of the present embodiment will be described. The electronic device of the present embodiment includes, for example, elements, devices, end products, etc. to which the technologies of electronics are applied, such as semiconductor devices, power semiconductor devices, semiconductor chips, semiconductor elements, printed wiring boards, electric circuit display devices, information communication terminals, light-emitting diodes, physical batteries, chemical batteries, etc. The electronic device of the present embodiment is preferably a power semiconductor device. A power semiconductor device is a semiconductor device that controls and converts electric power, and generally has a rated current of 1 A or more.

[0057] The manufacturing method of the electronic device of the present embodiment is not particularly limited, but preferably includes a step (A) of preparing a structure including an electronic component having a circuit formation surface and the adhesive film bonded to the circuit formation surface side of the electronic component, and a step (B) of processing the surface of the electronic component opposite to the circuit formation surface side in a vacuum atmosphere. Hereinafter, each step of the manufacturing method of the electronic device will be described.

[0058] [Step (A)] FIG. 2 is a cross-sectional view schematically showing the structure 100 in step (A). Step (A) prepares a structure 100 including an electronic component 10 having a circuit formation surface 10A and an adhesive film 50 bonded to the circuit formation surface 10A side of the electronic component 10.

[0059] Such a structure 100 can be manufactured by bonding an adhesive film 50 to the circuit formation surface 10A of the electronic component 10. The method of bonding the adhesive film 50 to the circuit formation surface 10A of the electronic component 10 is not particularly limited, and it can be bonded by a known method. For example, it may be performed manually, or it may be performed by an apparatus called an automatic bonding machine equipped with a roll-shaped adhesive film 50.

[0060] When bonding the circuit formation surface 10A of the electronic device 10, for example, it is performed while heating the adhesive film 50. Since the heating temperature is appropriately set according to the type of the adhesive film 50, it is not particularly limited. For example, it may be 40°C or higher, or 45°C or higher, and it may be 120°C or lower, or 110°C or lower.

[0061] The electronic component 10 is not particularly limited as long as it is an electronic component 10 having a circuit formation surface 10A. For example, a semiconductor wafer, a sapphire substrate, a lithium tantalate substrate, a molded wafer, a molded panel, a molded array package, a semiconductor substrate, etc. may be mentioned, and a semiconductor wafer is preferably used. Examples of the semiconductor wafer include a silicon wafer, a sapphire wafer, a germanium wafer, a germanium-arsenic wafer, a gallium-phosphorus wafer, a gallium-arsenic-aluminum wafer, a gallium-arsenic wafer, a lithium tantalate wafer, etc., and a silicon wafer is preferred.

[0062] On the circuit formation surface 10A of the electronic component 10, for example, circuits such as wirings, capacitors, diodes, or transistors are formed on the surface. Further, the circuit formation surface may be subjected to plasma treatment. Further, the circuit formation surface 10A of the electronic component 10 may be an uneven surface by having, for example, bump electrodes or the like. Also, the bump electrode is joined to an electrode formed on the mounting surface when, for example, mounting the electronic device on the mounting surface, to form an electrical connection between the electronic device and the mounting surface (such as the mounting surface of a printed circuit board). Examples of the bump electrode include a ball bump, a printed bump, a stud bump, a plated bump, a pillar bump, etc. That is, the bump electrode is usually a convex electrode. These bump electrodes may be used alone or in combination of two or more. The height and diameter of the bump electrode are not particularly limited, but preferably 10 μm or more, more preferably 50 μm or more, and preferably 400 μm or less, more preferably 300 μm or less, respectively. The bump pitch at that time is not particularly limited either, but preferably 20 μm or more, more preferably 100 μm or more, and preferably 600 μm or less, more preferably 500 μm or less. Also, the metal type constituting the bump electrode is not particularly limited, and examples include solder, silver, gold, copper, tin, lead, bismuth, and alloys thereof. However, the adhesive film 50 is preferably used when the bump electrode is a solder bump. These metal types may be used alone or in combination of two or more.

[0063] [Step (B)] In step (B), the surface 10B on the side opposite to the circuit formation surface 10A side of the electronic component 10 is processed in a vacuum atmosphere. Step (B) is a step subsequent to step (A). Therefore, in step (B), the surface 10B on the side opposite to the circuit formation surface 10A side of the electronic component 10 in the structure 100 is processed.

[0064] The vacuum atmosphere in step (B) means a low-pressure state reduced in pressure from the atmosphere by a vacuum device, and may be, for example, 1000 Pa or less, 100 Pa or less, or 10 Pa or less.

[0065] Step (B) may be under high-temperature conditions. When step (B) is under high-temperature conditions, the temperature of the structure 100 in step (B) is preferably 60°C or higher, more preferably 80°C or higher, still more preferably 100°C or higher, still more preferably 120°C or higher, still more preferably 140°C or higher, and is preferably 230°C or lower, more preferably 210°C or lower, still more preferably 190°C or lower, still more preferably 170°C or lower.

[0066] In step (B), the method of processing the surface 10B on the side opposite to the circuit formation surface 10A of the electronic component 10 is not particularly limited and can be a step in a known method for manufacturing an electronic device. Step (B) is preferably at least one selected from the group consisting of an ion implantation step, a metal film formation step, and an annealing treatment step.

[0067] The method for manufacturing an electronic device according to the present embodiment preferably further includes a step of heating the structure 100 as a step before step (B). By further including a step of heating the structure 100 as a step before step (B), the resin contained in the adhesive film 50 is thermally cured, and in step (B), the adhesive film 50 can be more effectively prevented from lifting off the electronic component 10, which is preferable. The temperature of the structure 100 in the step of heating the structure 100 is preferably 60°C or higher, more preferably 80°C or higher, still more preferably 100°C or higher, still more preferably 120°C or higher, still more preferably 140°C or higher, and is preferably 230°C or lower, more preferably 210°C or lower, still more preferably 190°C or lower, still more preferably 170°C or lower.

[0068] [Step (C)] The method for manufacturing an electronic device according to the present embodiment preferably further includes a step (C) of removing the adhesive film 50 from the electronic component 10. Step (C) is a step after step (B). That is, in step (C), the adhesive film 50 is removed from the electronic component 10 in the structure 100.

[0069] The method for removing the adhesive film 50 from the electronic component 10 is not particularly limited. For example, it is performed by peeling the adhesive film 50 from the electronic component 10 by a known method. As the peeling method, for example, it may be performed manually or by a device called an automatic peeling machine.

[0070] The temperature at the time of peeling the adhesive film 50 from the electronic component 10 may be room temperature (around 25°C), or when the automatic peeling machine is equipped with a temperature raising function, the adhesive film 50 may be peeled in a state where the structure 100 is heated to a predetermined temperature (for example, 40°C or higher and 90°C or lower).

[0071] The surface of the electronic component 10 after peeling the adhesive film 50 may be washed as necessary. Examples of the washing method include wet washing such as water washing and solvent washing, and dry washing such as plasma washing. In the case of wet washing, ultrasonic washing may be used in combination. The washing method can be appropriately selected according to the contamination status of the surface of the electronic component 10.

[0072] [Step (D)] The manufacturing method of the electronic device of the present embodiment preferably further includes a step (D) of back grinding the surface 10B on the side opposite to the circuit formation surface 10A of the electronic component 10. Step (D) is a step performed between step (A) and step (B). "Back grinding" means thinning the electronic component 10 to a predetermined thickness without damaging it. For example, the structure 100 is fixed to a chuck table of a grinding machine, etc., and the surface 10B on the side opposite to the circuit formation surface 10A of the electronic component 10 is ground.

[0073] In such a back grinding operation, the electronic component 10 is ground until its thickness becomes equal to or less than the desired thickness. The thickness of the electronic component 10 before grinding is appropriately determined according to the diameter, type, etc. of the electronic component 10, and the thickness of the electronic component 10 after grinding is appropriately determined according to the size of the obtained chip, the type of circuit, etc. Also, when the electronic component 10 is half-cut or a modified layer is formed by laser irradiation, the electronic component 10 is separated into individual pieces to become chips.

[0074] The back grinding method is not particularly limited, and a known grinding method can be adopted. Grinding can be performed while cooling by applying water to the electronic component 10 and the grindstone. If necessary, a dry polish process, which is a grinding method without using grinding water at the end of the grinding process, can be performed. After the back grinding is completed, chemical etching is performed if necessary. Chemical etching is performed by a method such as immersing the electronic component 10 in an etching solution selected from the group consisting of an acidic aqueous solution composed of a single or mixed solution of hydrofluoric acid, nitric acid, sulfuric acid, acetic acid, etc., and an alkaline aqueous solution such as a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution, with the adhesive film 50 attached. Etching is performed for the purpose of removing distortion generated on the back surface of the electronic component 10, further thinning the electronic component 10, removing an oxide film, etc., and pre-treatment when forming an electrode on the back surface. The etching solution is appropriately selected according to the above purposes.

[0075] [Other Processes] The method for manufacturing the electronic device of the present embodiment may have other processes other than the above. As other processes, known methods in the method for manufacturing an electronic device can be used. For example, any process generally performed in the manufacturing process of electronic components such as a resist process, a development process, an ashing process, a sputtering process, a dicing process, a die bonding process, a wire bonding process, a flip chip connection process, a cure heating test process, a sealing process, a reflow process, etc. may be further performed.

[0076] As described above, the embodiments of the present invention have been described, but these are examples of the present invention, and various configurations other than the above can also be adopted.

[0077] Note that the present invention is not limited to the above-described embodiments, and modifications, improvements, etc. within the scope that can achieve the object of the present invention are included in the present invention.

Example

[0078] Hereinafter, the present invention will be specifically described by way of examples and comparative examples, but the present invention is not limited thereto. Details regarding the production of the adhesive film are as follows.

[0079] <Material> Base material layer 1: polyethylene naphthalate film (manufactured by Toyobo Film Solutions Co., Ltd., trade name: Teonex Q81, thickness: 50 μm) Resin 1: ethylene-vinyl acetate copolymer (manufactured by Mitsui Dow Polychemical Co., Ltd., trade name: Evaflex EV460, melting point: 84 °C, content ratio of structural units derived from vinyl acetate: 19% by mass, MFR (190 °C, 2.16 kg): 2.5 g / 10 min) Crosslinking agent 1: isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., trade name: Orestar P49-75S) Thermal polymerization initiator 1: peroxide (manufactured by Kayaku Nuourion Co., Ltd., trade name: Perkadox 12-XL25) Photoinitiator 1: α-amino ketone (manufactured by IGM Resins B.V., trade name: Omnirad379) Polyfunctional acrylate 1: ditrimethylolpropane tetraacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name: AD-TMP)

[0080] <Preparation of (meth)acrylic polymer solution a> n-butyl acrylate (77 parts by mass), methyl methacrylate (16 parts by mass), 2-hydroxyethyl acrylate (7 parts by mass), and t-butyl peroxy-2-ethylhexanoate (0.3 parts by mass) as a polymerization initiator were reacted at 85 °C for 10 hours with toluene (20 parts by mass) and ethyl acetate (80 parts by mass). After completion of the reaction, the solution was cooled, and toluene (30 parts by mass), methacryloyloxyethyl isocyanate (7 parts by mass), and dibutyltin dilaurate (0.05 parts by mass) were added thereto, and the mixture was reacted at 85 °C for 12 hours while blowing air to obtain (meth)acrylic polymer solution a.

[0081] <Preparation of (meth)acrylic polymer solution b> n-Butyl acrylate (72 parts by mass), methyl methacrylate (18 parts by mass), 2-hydroxyethyl methacrylate (7 parts by mass), acrylic acid (3 parts by mass), and t-butyl peroxy-2-ethylhexanoate (0.3 parts by mass) as a polymerization initiator were reacted at 85°C for 10 hours with toluene (36 parts by mass) and ethyl acetate (53 parts by mass). After the reaction was completed, the solution was cooled, and toluene (34 parts by mass) was added thereto to obtain (meth)acrylic polymer solution b.

[0082] [Example 1] (Preparation of Adhesive Coating Liquid for Thermosetting Adhesive Layer) To 100 parts by mass of (meth)acrylic polymer solution a (solid content), 0.8 part by mass of thermal polymerization initiator 1, 2.56 parts by mass of crosslinking agent 1, and 10 parts by mass of polyfunctional acrylate 1 were added to obtain an adhesive coating liquid for a thermosetting adhesive layer.

[0083] (Production of Adhesive Film) Using an extrusion molding machine, 100 parts by mass of resin 1 was extruded onto substrate layer 1. A laminated film was obtained in which a concavo-convex absorbing resin layer with a thickness of 70 μm was laminated on the substrate layer. Next, the adhesive coating liquid for a thermosetting adhesive layer was applied to a silicone release-treated polyethylene terephthalate film (38 μm) and dried to form a thermosetting adhesive layer with a thickness of 20 μm. Then, the obtained thermosetting adhesive layer was bonded to the concavo-convex absorbing resin layer side of the above-mentioned laminated film to obtain an adhesive film.

[0084] [Examples 2 to 4 and Comparative Example 2] (Preparation of Adhesive Coating Liquid for Thermosetting Adhesive Layer) An adhesive coating liquid for a thermosetting adhesive layer was obtained in the same manner as in Example 1, except that the formulation of the adhesive coating liquid was the formulation shown in Table 1. (Production of Adhesive Film) An adhesive film was obtained in the same manner as in Example 1, except that the thickness of the concavo-convex absorbing resin layer was the thickness shown in Table 1.

[0085] [Example 5] (Preparation of Adhesive Coating Liquid for Thermosetting Adhesive Layer) In the same manner as in Example 1, an adhesive coating liquid for a thermosetting adhesive layer was obtained.

[0086] (Preparation of Coating Liquid for Concavo-Convex Absorbing Resin Layer) To (meth)acrylic polymer solution a (50 parts by mass) and (meth)acrylic polymer solution b (50 parts by mass), crosslinking agent 1 (0.3 part by mass) was added to obtain a coating liquid for a concavo-convex absorbing resin layer.

[0087] (Production of Adhesive Film) The coating liquid for the concavo-convex absorbing resin layer was applied onto the base material layer 1 and dried to form a concavo-convex absorbing resin layer with a thickness of 40 μm, thereby obtaining a laminated film. Next, the adhesive coating liquid for the thermosetting adhesive layer was applied onto a silicone release-treated polyethylene terephthalate film (38 μm) and dried to form a thermosetting adhesive layer with a thickness of 20 μm. Then, the obtained thermosetting adhesive layer was bonded to the concavo-convex absorbing resin layer side of the above-mentioned laminated film to obtain an adhesive film.

[0088] [Comparative Example 1] (Preparation of Coating Liquid for Thermosetting Adhesive Layer) An adhesive coating liquid for a thermosetting adhesive layer was obtained in the same manner as in Example 1, except that the formulation of the adhesive coating liquid was the formulation described in Table 1.

[0089] (Production of Adhesive Film) The adhesive coating liquid for the thermosetting adhesive layer was applied onto a silicone release-treated polyethylene terephthalate film (38 μm) and dried to form a thermosetting adhesive layer with a thickness of 20 μm. Next, the obtained thermosetting adhesive layer was bonded to the base material layer 1 to obtain an adhesive film.

[0090] [Measurement and Evaluation Method] (1) Measurement of Stress Residual Ratio of Adhesive Film at 100 °C n sheets of the adhesive film were laminated until the thickness reached 1.4 ± 0.1 mm to prepare a measurement sample. Here, the measurement sample was laminated such that the base material layer of the adhesive film and the thermosetting adhesive layer of the adjacent adhesive film were in direct contact. Also, the number of laminated adhesive films was set to the number at which the thickness of the measurement sample approached 1.4 mm. That is, since the number of laminated adhesive films varies depending on the thickness of the adhesive film, the number of laminated adhesive films differs for each sample. For the measurement sample cut to a width of 10 mm, using a dynamic viscoelasticity measuring device (manufactured by Netzsch-Gerätebau GmbH, EPLEXOR 500N), at a temperature of 100 °C, deformation mode: compression, upper jig: three-point bending (tip of the indenter: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen, the stress was measured while continuously applying a strain of 2%. The measurement sample was installed so that the major axis direction of the indenter in the upper jig and the width direction of the measurement sample were in the same direction, and the strain was continuously applied in the thickness direction of the measurement sample. The stress retention rate [%] at 100 °C was calculated by the formula “(stress at 600 seconds [Pa] / stress at the time when the maximum stress was measured [Pa]) × 100”.

[0091] (2) Measurement of the stress retention rate of the adhesive film at 150 °C A measurement sample was prepared by the method described in (1). Then, using a constant-temperature dryer (manufactured by Yamato Scientific Co., Ltd., DN-63H), the measurement sample was heat-treated at 130 °C for 30 minutes. For the measurement sample cut to a width of 10 mm, using a dynamic viscoelasticity measuring device (manufactured by Netzsch-Gerätebau GmbH, EPLEXOR 500N), at a temperature of 150 °C, deformation mode: compression, upper jig: three-point bending (tip of the indenter: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen, the stress was measured while continuously applying a strain of 2%. The measurement sample was installed so that the major axis direction of the indenter in the upper jig and the width direction of the measurement sample were in the same direction, and the strain was continuously applied in the thickness direction of the measurement sample. The stress residual rate [%] at 150 °C was calculated by the formula of “(stress [Pa] at 600 seconds / stress [Pa] at the time when the maximum stress was measured) × 100”.

[0092] (3) Evaluation of concavo-convex followability For the circuit formation surface of a wafer (8-inch power device simulation wafer, height of the circuit formation surface (thickness of polyimide): 10 μm, chip size: 10 mm × 10 mm, small pad size: 1 mm × 1 mm), using an attachment device (manufactured by Takatori Corporation, product name: TPL-0612W), an adhesive film was attached under the conditions of SP1: 800 Pa, SP2: 300 Pa, SP3: 100 Pa, attachment pressure: 0.2 MPa, and attachment temperature: 100 °C. For the wafer with the adhesive film attached, two arbitrary locations were observed using a laser microscope (manufactured by Keyence Corporation, product name: VK-X1000) and evaluated according to the following criteria. A (good): No lifting is confirmed near the 10-μm step of the polyimide. B (bad): Lifting is confirmed near the 10-μm step of the polyimide.

[0093] (4) Evaluation of vacuum resistance By the method described in (3), an adhesive film was attached to the circuit formation surface of the wafer, left for 1 hour or more, and then pre-baked at 130 °C for 30 minutes using a constant-temperature dryer (manufactured by Yamato Scientific Co., Ltd., DN-63H). Next, the wafer with the adhesive film attached was heated in a vacuum constant-temperature dryer (manufactured by Shimizu Rikagaku Kikai Seisakusho Co., Ltd., VOD6-4H) under the conditions of a vacuum pressure of 100 - 150 Pa, a temperature of 150 °C, and a time of 15 minutes. The presence or absence of film lifting during the heating process under reduced pressure was visually observed and evaluated according to the following criteria. A (good): No lifting with a diameter of 0.5 mm or more is visually confirmed. B (bad): Lifting with a diameter of 0.5 mm or more is visually confirmed.

[0094] For Examples 1 to 5 and Comparative Examples 1 and 2, each evaluation was performed respectively. The obtained results are shown in Table 1 respectively.

[0095]

Table 1

[0096] From Table 1, it can be understood that the adhesive films of the examples are both good in the evaluation of unevenness followability and vacuum resistance. That is, according to the adhesive film of this embodiment, it can be understood that the performance balance of unevenness followability and vacuum resistance is improved.

Explanation of Signs

[0097] 10 Electronic component 10A Circuit formation surface of the electronic component 10B Surface opposite to the circuit formation surface side of the electronic component 20 Base material layer 30 Unevenness absorbing resin layer 40 Thermosetting adhesive layer 50 Adhesive film 100 Structure

Claims

Claim 1 An adhesive film used in the manufacturing process of an electronic device, wherein the stress retention rate at 100 °C calculated by the following Method 1 is 55.0% or less, and the stress retention rate at 150 °C calculated by the following Method 2 is 5.0% or more and 90.0% or less. An adhesive film. [Method 1] The adhesive film is laminated until it reaches a thickness of 1.4 ± 0.1 mm to prepare a measurement sample. For the measurement sample cut to a width of 10 mm, using a dynamic viscoelasticity measuring device, temperature: 100 °C, deformation mode: compression, upper jig: three-point bending (tip of the indenter: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen, the stress when continuously applying a strain of 2% is measured, and the value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the maximum stress is measured [Pa]) × 100" is defined as the stress retention rate [%] at 100 °C. [Method 2] For a sample obtained by laminating the adhesive film until it reaches a thickness of 1.4 ± 0.1 mm, a measurement sample is prepared by performing a heat treatment under the conditions of 130 °C for 30 minutes. For the measurement sample cut to a width of 10 mm, using a dynamic viscoelasticity measuring device, temperature: 150 °C, deformation mode: compression, upper jig: three-point bending (tip of the indenter: 2.5R), lower jig: parallel plate, measurement time: 1000 seconds, atmosphere: nitrogen, the stress when continuously applying a strain of 2% is measured, and the value calculated by the formula "(stress at 600 seconds [Pa] / stress at the time when the maximum stress is measured [Pa]) × 100" is defined as the stress retention rate [%] at 150 °C. Claim 2 The adhesive film according to Claim 1, comprising a base material layer, a concavo-convex absorbent resin layer, and a thermosetting adhesive layer in this order. Claim 3 The adhesive film according to Claim 2, wherein the concavo-convex absorbent resin layer and the thermosetting adhesive layer are provided so as to be in direct contact with each other. Claim 4 The adhesive film according to Claim 2 or 3, wherein the thermosetting adhesive layer contains a (meth)acrylic resin and a thermal polymerization initiator. Claim 5 The adhesive film according to Claim 2 or 3, wherein the resin constituting the concavo-convex absorbent resin layer contains at least one selected from the group consisting of ethylene-vinyl acetate copolymer, (meth)acrylic resin, ethylene-α-olefin copolymer, and low-density polyethylene. Claim 6 The adhesive film according to claim 2 or 3, wherein the thickness of the concavo-convex absorbent resin layer is 20 μm or more and 500 μm or less.

7. The adhesive film according to claim 2 or 3, wherein the resin constituting the base material layer contains at least one selected from the group consisting of polyethylene naphthalate, polyethylene terephthalate, and polyimide.

8. The manufacturing process of the electronic device includes: a step (A) of preparing a structure including an electronic component having a circuit formation surface and the adhesive film bonded to the circuit formation surface side of the electronic component; and a step (B) of processing the surface of the electronic component opposite to the circuit formation surface side in a vacuum atmosphere. The adhesive film according to claim 1 or 2.

9. The adhesive film according to claim 1 or 2, wherein the electronic device is a power semiconductor device.