JP7709349B2 - Adhesive Film - Google Patents

Description

The present invention relates to an adhesive film.

2. Description of the Related Art As a technique capable of reducing the size and weight of electronic devices (e.g., semiconductor devices), a method for manufacturing an electronic device using an adhesive film is known.
An example of the application of the adhesive film in the manufacture of electronic devices is the sealing process. Specifically, the adhesive film may be applied to a process in which (i) a wafer or chip is first fixed with an adhesive film, (ii) the fixed wafer or chip is then sealed with a sealant, and (iii) the adhesive film is then peeled off.

As a technique relating to a method for manufacturing an electronic device using an adhesive film, for example, the technique described in Patent Document 1 can be mentioned.
Patent Document 1 describes a heat-resistant adhesive sheet for use in manufacturing semiconductor device that is attached when resin-encapsulating a substrateless semiconductor chip, the heat-resistant adhesive sheet having a base layer and an adhesive layer, the adhesive layer having an adhesive strength to SUS304 of 0.5 N/20 mm or more after lamination, and hardening due to stimuli received up to the time when the resin-encapsulating process is completed, such that the peel strength to the package is 2.0 N/20 mm or less.

Patent Document 2 describes an adhesive film used for temporarily fixing electronic components when sealing the electronic components with a sealing material in the manufacturing process of an electronic device. The adhesive film includes an adhesive resin layer (A) for temporarily fixing the electronic components, an adhesive resin layer (B) used for attaching to a support substrate and having a lower adhesive strength due to an external stimulus, and an intermediate layer (C) provided between the adhesive resin layer (A) and the adhesive resin layer (B). The storage modulus E' of the intermediate layer (C) at 120°C is 1.0×10 ⁵ Pa or more and 8.0×10 ⁶ Pa or less, and the loss tangent (tan δ) of the intermediate layer (C) at 120°C is 0.1 or less.

Patent Document 3 also describes a method for manufacturing an electronic device using an adhesive film. Specifically, the method for manufacturing an electronic device described in Patent Document 3 includes at least a step (1) of preparing a structure including an adhesive film including a base layer, an adhesive resin layer provided on the first surface side of the base layer and for temporarily fixing an electronic component, and an adhesive resin layer (B) provided on the second surface side of the base layer and whose adhesive strength is reduced by an external stimulus, an electronic component attached to the adhesive resin layer (A) of the adhesive film, and a support substrate attached to the adhesive resin layer (B) of the adhesive film, at least one step (2) selected from a step (2-1) of reducing the moisture content in the adhesive film and a step (2-2) of reducing the moisture content in the structure, and a step (3) of sealing the electronic component with a sealing material.

Patent Document 4 also describes a method for manufacturing an electronic device. Specifically, the method for manufacturing an electronic device described in Patent Document 4 includes at least a preparation step of preparing a structure including a base layer, an adhesive resin layer (A) provided on the first surface side of the base layer and for temporarily fixing an electronic component, an adhesive resin layer (B) provided on the second surface side of the base layer and whose adhesive strength is reduced by an external stimulus, and an unevenness-absorbing resin layer (C) provided between the base layer and the adhesive resin layer (A) or between the base layer and the adhesive resin layer (B), an electronic component having an uneven structure attached to the adhesive resin layer (A) of the adhesive film, and a support substrate attached to the adhesive resin layer (B) of the adhesive film, and a sealing step of sealing the electronic component with a sealing material.

JP 2011-134811 A JP 2018-157037 A International Publication No. 2019/188543 International Publication No. 2020/184201

The inventors' investigations have revealed that when placing an electronic component having an uneven structure, such as bumps, on an adhesive film and sealing the electronic component with a sealant, the electronic component may become misaligned in the horizontal direction (hereinafter also referred to as misalignment of the electronic component) or the sealant may get in between the adhesive film and the electronic component.

In order to improve the above-mentioned problems, it is considered effective to use an adhesive film having an unevenness-absorbing resin layer, as described in Patent Document 4, for example. By using an adhesive film having an unevenness-absorbing resin layer, it is possible to prevent the electronic components from shifting in position during the sealing process and the sealant from penetrating between the adhesive film and the electronic components.

However, as shown in Figures 4(a) to (c), when an adhesive film 50A with an unevenness-absorbing resin layer is used, when an electronic component 70A having an uneven structure 75A is placed and sealed with a sealant 60A, the unevenness-absorbing resin layer softens due to heat, and the electronic component 70A is likely to sink into the adhesive film 50A due to the pressure of the sealant 60A. As a result, it has become clear that there are cases where a seal failure of the electronic component 70A, called a standoff 90 (where part of the side of the electronic component 70A is not sealed) or wrinkles occur on the surface of the sealant after sealing, as shown in Figure 4(d).

The present inventors have conducted research to solve the above-mentioned problems of stand-off and wrinkles, and have found that an adhesive film having a crosslinkable unevenness-absorbing resin layer is effective. The present inventors have conducted further research and found that there is still room for improvement in both photocrosslinkable resins and thermally crosslinkable resins.
That is, when the support is opaque to light, light is applied from the side where the chip is fixed, but the light does not reach the area directly below the chip, which tends to result in insufficient curing of the photocrosslinkable intermediate layer.
When a thermally crosslinkable intermediate layer is used, the surface of the adhesive layer between the chips is exposed to air, so the radicals generated from the added curing agent are quenched by oxygen, which can lead to insufficient curing of the intermediate layer.
The present invention has been made in consideration of the above circumstances. One of the objects of the present invention is to provide an adhesive film that can absorb unevenness at least as well as conventional ones, while suppressing the occurrence of standoffs, which are sealing defects of electronic components, and wrinkles.

The present inventors conducted extensive research to achieve the above object. As a result, they discovered that the use of an adhesive film having an unevenness-absorbing resin layer that can be crosslinked by light energy and thermal energy as an adhesive film can suppress the occurrence of standoffs, which are sealing defects and wrinkles in electronic components, and thus completed the present invention.

According to the present invention, the following adhesive film is provided:

[1]
An adhesive film comprising: a base layer; an adhesive resin layer (A) provided on a first surface side of the base layer for temporarily fixing an electronic component; an adhesive resin layer (B) provided on a second surface side of the base layer; and an unevenness-absorbing resin layer (C) provided between the base layer and the adhesive resin layer (A) or between the base layer and the adhesive resin layer (B) and capable of being crosslinked by light energy and thermal energy.
[2]
In the pressure-sensitive adhesive film according to the above-mentioned [1],
The adhesive film, wherein the adhesive resin layer (B) is a layer whose adhesive strength decreases in response to an external stimulus.
[3]
In the pressure-sensitive adhesive film according to the above-mentioned [1] or [2],
The adhesive film, wherein the unevenness-absorbing resin layer (C) comprises a resin, a crosslinking agent, a photoinitiator, and a thermal initiator.
[4]
The adhesive film according to [3] above, wherein the photoinitiator comprises an alkylphenone-based photoinitiator.
[5]
The adhesive film according to [3] or [4], wherein the thermal initiator comprises one or more selected from aromatic ketones, onium salt compounds, organic peroxides, thio compounds, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and azo compounds.
[6]
The pressure-sensitive adhesive film according to any one of [3] to [5], wherein the crosslinking agent comprises one or more selected from a multifunctional (meth)acrylate compound and an isocyanate compound.
[7]
In the pressure-sensitive adhesive film according to any one of the above [1] to [6],
An adhesive film, wherein the unevenness-absorbing resin layer (C) is provided at least between the base layer and the adhesive resin layer (A).
[8]
In the pressure-sensitive adhesive film according to any one of the above [1] to [7],
The adhesive film further comprises an unevenness-absorbing resin layer (C') obtained by crosslinking the unevenness-absorbing resin layer (C), the unevenness-absorbing resin layer (C') having a storage modulus E' at 125° C. of 1.0×10 ⁶ Pa or more and 1.0×10 ⁹ Pa or less.
[9]
In the pressure-sensitive adhesive film according to any one of the above [1] to [8],
The thickness of the unevenness-absorbing resin layer (C) of the pressure-sensitive adhesive film is from 5 μm to 1000 μm.
[10]
In the pressure-sensitive adhesive film according to any one of the above [1] to [9],
An adhesive film, wherein the adhesive resin constituting the adhesive resin layer (A) is one or more selected from (meth)acrylic adhesive resins, silicone adhesive resins, urethane adhesive resins, olefin adhesive resins and styrene adhesive resins.
[11]
In the pressure-sensitive adhesive film according to any one of the above [1] to [10],
An adhesive film used for temporarily fixing an electronic component when the electronic component is sealed with a sealing material.
[12]
In the pressure-sensitive adhesive film according to the above-mentioned [11],
The electronic component is an adhesive film having a concave-convex structure.
[13]
In the pressure-sensitive adhesive film according to the above-mentioned [12],
The uneven structure of the electronic component is an adhesive film including bump electrodes.

The present invention provides a method for manufacturing electronic components that can absorb unevenness to an equal or greater extent than conventional methods while suppressing the occurrence of standoffs, which are defective sealing of electronic components, and wrinkles.

1 is a cross-sectional view showing a schematic example of a structure of an adhesive film according to an embodiment of the present invention. 1A to 1C are cross-sectional views illustrating an example of a method for manufacturing an electronic device according to an embodiment of the present invention. 1A to 1C are cross-sectional views illustrating an example of a method for manufacturing an electronic device according to an embodiment of the present invention. FIG. 1 is a diagram for explaining a sealing defect of an electronic component called a standoff.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In all the drawings, the same components are denoted by the same reference numerals, and the description thereof will be omitted as appropriate. In addition, the drawings are schematic views, and the actual dimensional ratios are not necessarily the same.
In the present specification, unless otherwise specified, the expression "A to B" regarding a numerical range means from A to B. For example, 1 to 5% means from 1% to 5%.
In the present specification, "(meth)acrylic" means acrylic, methacrylic, or both acrylic and methacrylic.

1. Adhesive Film The adhesive film 50 according to this embodiment will now be described.
FIG. 1 is a cross-sectional view showing a schematic example of the structure of an adhesive film 50 according to an embodiment of the present invention.

As shown in FIG. 1, the adhesive film 50 according to this embodiment comprises a base layer 10, an adhesive resin layer (A) provided on a first surface 10A side of the base layer 10 for temporarily fixing an electronic component, an adhesive resin layer (B) provided on a second surface 10B side of the base layer 10, and an unevenness-absorbing resin layer (C) provided between the base layer 10 and the adhesive resin layer (A) or between the base layer 10 and the adhesive resin layer (B) and capable of being crosslinked by light energy and thermal energy.
From the viewpoint of further improving the unevenness absorbency of the adhesive film 50, the unevenness-absorbing resin layer (C) is preferably located at least between the base layer 10 and the adhesive resin layer (A).
When the unevenness-absorbing resin layer (C) is located between the base layer 10 and the adhesive resin layer (A), another unevenness-absorbing resin layer (C2) may be present between the adhesive resin layer (B) and the base layer 10. In this case, the unevenness-absorbing resin layer (C) and the unevenness-absorbing resin layer (C2) may be the same or different in terms of material, thickness, etc.

As described above, according to the inventors' investigations, by using an adhesive film having an unevenness-absorbing resin layer as described in Patent Document 4 as the adhesive film, it is possible to suppress misalignment of electronic components during the sealing process and infiltration of sealing material between the adhesive film and the electronic components.
However, as shown in Figures 4(a) to 4(c), when an adhesive film 50A having an unevenness-absorbing resin layer is used, when an electronic component 70A having an uneven structure 75A is arranged and sealed with a sealing material 60A, the unevenness-absorbing resin layer is softened by heat, and the electronic component 70A is likely to sink into the adhesive film 50A due to the pressure of the sealing material 60A. As a result, a sealing failure of the electronic component 70A, called a standoff 90, may occur as shown in Figure 4(d).

The present inventors have conducted extensive research to realize an adhesive film that can suppress the displacement of electronic components during the sealing process and the intrusion of sealing material between the adhesive film and the electronic components, as well as the occurrence of stand-off during the sealing process. As a result, the inventors have found for the first time that an adhesive film 50 comprising a base layer 10, an adhesive resin layer (A) provided on the first surface 10A side of the base layer 10 and for temporarily fixing electronic components, an adhesive resin layer (B) provided on the second surface 10B side of the base layer 10, and an unevenness-absorbing resin layer (C) that is provided between the base layer 10 and the adhesive resin layer (A) or between the base layer 10 and the adhesive resin layer (B) and can be crosslinked by light energy and thermal energy, can suppress the displacement of electronic components during the sealing process and the intrusion of sealing material between the adhesive film and the electronic components, as well as the occurrence of stand-off during the sealing process.

That is, according to this embodiment, by using an adhesive film 50 having an unevenness-absorbing resin layer (C) that can be crosslinked by light energy and thermal energy as an adhesive film for temporarily fixing an electronic component having an uneven structure, the adhesive film 50 has improved adhesion to an electronic component having an uneven structure. Therefore, in the process of sealing the electronic component, it is possible to prevent the position of the electronic component from being shifted due to pressure caused by the flow of the sealing material, and the sealing material from penetrating between the adhesive film and the electronic component. Furthermore, after temporarily fixing an electronic component having an uneven structure, the unevenness-absorbing resin layer (C) is crosslinked and cured by light energy and thermal energy to increase the elastic modulus, thereby preventing the electronic component from sinking into the adhesive film in the process of sealing the electronic component. That is, by designing the unevenness-absorbing resin layer (C) so that it undergoes cross-linking and changes its elastic modulus due to light energy and thermal energy, (i) before light energy and thermal energy are applied, the unevenness-absorbing resin layer (C) can be sufficiently deformed to match the uneven structure of the electronic component, and (ii) on the other hand, after light energy and thermal energy are applied, movement of the electronic component is suppressed.

Furthermore, it has been found for the first time that the occurrence of wrinkles on the surface of the sealing material after sealing can be suppressed by crosslinking and curing the unevenness-absorbing resin layer (C) using light energy and heat energy.
Although the mechanism is unclear, it is considered that when irradiation is performed from the electronic component 70 side in FIG. 2, the area directly below the electronic component where the light does not hit is insufficiently photocured. In addition, since the adhesive layer surface between the electronic components 70 is exposed to air, it is considered that active chemical species such as radicals and cations generated from the initiator are quenched by oxygen, that is, so-called oxygen inhibition makes it difficult for thermal curing to occur. In this case, it is considered that crosslinking and curing of the unevenness-absorbing resin layer (C) can be performed by both light energy and thermal energy to compensate for the parts that are difficult to cure by each energy.
As a result, it is presumed that the occurrence of wrinkles on the surface of the sealing material after sealing, which is caused by insufficient crosslinking and curing of the unevenness-absorbing resin layer (C), can be suppressed.

As described above, the adhesive film 50 according to this embodiment can prevent the electronic components from shifting in position during the sealing process and the sealant from entering between the adhesive film and the electronic components, and can also prevent the occurrence of standoffs and wrinkles during the sealing process.

From the viewpoint of the balance between mechanical properties and ease of handling, the overall thickness of the adhesive film 50 according to this embodiment is preferably 10 μm or more and 1000 μm or less, and more preferably 20 μm or more and 500 μm or less.

The adhesive film 50 according to this embodiment can be used, for example, as a film for temporarily fixing electronic components when sealing the electronic components with a sealing material in the manufacturing process of an electronic device.
In this case, the electronic component may have an uneven structure.

Next, we will explain each layer that constitutes the adhesive film 50 according to this embodiment.

<Base material layer>
The base layer 10 is a layer provided for the purpose of improving the properties of the pressure-sensitive adhesive film 50, such as ease of handling, mechanical properties, and heat resistance.
The base layer 10 is not particularly limited, but may be, for example, a resin film.
Examples of the resin constituting the resin film include known thermoplastic resins, such as polyolefins such as polyethylene, polypropylene, poly(4-methyl-1-pentene), and poly(1-butene); polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamides such as nylon-6, nylon-66, and polymethaxylene adipamide; polyacrylates; polymethacrylates; polyvinyl chloride; polyvinylidene chloride; polyimides; polyetherimides; ethylene-vinyl acetate copolymers; polyacrylonitrile; polycarbonates; polystyrenes; ionomers; polysulfones; polyethersulfones; and polyphenylene ethers.
Among these, from the viewpoint of an excellent balance of transparency, mechanical strength, price, and the like, one or more selected from polypropylene, polyethylene terephthalate, polyethylene naphthalate, polyamide, and polyimide are preferred, and at least one selected from polyethylene terephthalate and polyethylene naphthalate is more preferred.

The substrate layer 10 may be a single layer or two or more layers.
The form of the resin film used to form the base layer 10 may be a stretched film or a uniaxially or biaxially stretched film, but from the viewpoint of improving the mechanical strength of the base layer 10, it is preferable that the resin film be a uniaxially or biaxially stretched film.

From the viewpoint of obtaining good film properties, the thickness of the base layer 10 is preferably 1 μm or more and 500 μm or less, more preferably 5 μm or more and 300 μm or less, and further preferably 10 μm or more and 250 μm or less.
The substrate layer 10 may be subjected to a surface treatment in order to improve adhesion to other layers. Specifically, corona treatment, plasma treatment, undercoat treatment, primer coat treatment, etc. may be performed.

<Adhesive resin layer (A)>
The adhesive resin layer (A) is a layer provided on one surface side of the base layer 10. The adhesive resin layer (A) is a layer for temporarily fixing an electronic component by contacting the surface of the electronic component when sealing the electronic component with a sealing material in a manufacturing process of an electronic device, for example.

The adhesive resin layer (A) preferably contains an adhesive resin (A1).
The adhesive resin (A1) preferably contains one or more selected from the group consisting of (meth)acrylic adhesive resins (a), silicone adhesive resins, urethane adhesive resins, olefin adhesive resins, and styrene adhesive resins.
Among these, the (meth)acrylic adhesive resin (a) is preferred from the viewpoint of facilitating adjustment of adhesive strength.

The adhesive resin layer (A) may be a radiation-crosslinked adhesive resin layer whose adhesive strength can be reduced by radiation. When the radiation-crosslinked adhesive resin layer is irradiated with radiation, crosslinking occurs and the adhesive strength is significantly reduced, making it easier to peel the adhesive film 50 from the electronic component. Examples of radiation include ultraviolet rays, electron beams, and infrared rays.
The radiation crosslinkable adhesive resin layer is preferably an ultraviolet crosslinkable adhesive resin layer.

Examples of the (meth)acrylic adhesive resin (a) used in the adhesive resin layer (A) include a copolymer containing a (meth)acrylic acid alkyl ester monomer unit (a1) and a monomer unit (a2) having a functional group capable of reacting with a crosslinking agent.
In this embodiment, the (meth)acrylic acid alkyl ester means an acrylic acid alkyl ester, a methacrylic acid alkyl ester, or a mixture thereof.

The (meth)acrylic adhesive resin (a) according to this embodiment can be obtained, for example, by copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester monomer (a1) and a monomer (a2) having a functional group capable of reacting with a crosslinking agent.

Examples of the monomer (a1) forming the (meth)acrylic acid alkyl ester monomer unit (a1) include (meth)acrylic acid alkyl esters having an alkyl group with about 1 to 12 carbon atoms. Preferred are (meth)acrylic acid alkyl esters having an alkyl group with 1 to 8 carbon atoms. Specific examples include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, and 2-ethylhexyl methacrylate. These may be used alone or in combination of two or more.
In the (meth)acrylic adhesive resin (a) according to the present embodiment, the content of the (meth)acrylic acid alkyl ester monomer unit (a1) is preferably 10% by mass or more and 98.9% by mass or less, more preferably 50% by mass or more and 97% by mass or less, and even more preferably 85% by mass or more and 95% by mass or less, when the sum of all monomer units in the (meth)acrylic adhesive resin (a) is 100% by mass.

Examples of the monomer (a2) that forms the monomer unit (a2) having a functional group that can react with a crosslinking agent include acrylic acid, methacrylic acid, itaconic acid, mesaconic acid, citraconic acid, fumaric acid, maleic acid, itaconic acid monoalkyl ester, mesaconic acid monoalkyl ester, citraconic acid monoalkyl ester, fumaric acid monoalkyl ester, maleic acid monoalkyl ester, glycidyl acrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, methacrylamide, tertiary-butylaminoethyl acrylate, and tertiary-butylaminoethyl methacrylate. Preferred are acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, methacrylamide, and the like. These may be used alone or in combination of two or more.
In the (meth)acrylic adhesive resin (a) according to the present embodiment, the content of the monomer unit (a2) is preferably 1 mass % or more and 40 mass % or less, more preferably 1 mass % or more and 20 mass % or less, and even more preferably 1 mass % or more and 10 mass % or less, when the sum of all monomer units in the (meth)acrylic adhesive resin (a) is 100 mass %.

The (meth)acrylic adhesive resin (a) according to this embodiment may further contain, in addition to the monomer unit (a1) and the monomer unit (a2), a bifunctional monomer unit (a3) or a specific comonomer unit having surfactant properties (hereinafter referred to as a polymerizable surfactant).
The polymerizable surfactant has the property of copolymerizing with the monomers (a1), (a2) and (a3), and also acts as an emulsifier in the case of emulsion polymerization.

Examples of the monomer (a3) that forms the bifunctional monomer unit (a3) include allyl methacrylate, allyl acrylate, divinylbenzene, vinyl methacrylate, vinyl acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tetraethylene glycol di(meth)acrylate, and, for example, diacrylates at both ends. or dimethacrylate with a main chain structure of propylene glycol type (for example, Nippon Oil & Fats Co., Ltd., product names: PDP-200, PDP-400, ADP-200, ADP-400), tetramethylene glycol type (for example, Nippon Oil & Fats Co., Ltd., product names: ADT-250, ADT-850), and mixtures of these types (for example, Nippon Oil & Fats Co., Ltd., product names: ADET-1800, ADPT-4000).

In the (meth)acrylic adhesive resin (a) according to this embodiment, the content of the monomer unit (a3) is preferably from 0.1% by mass to 30% by mass, more preferably from 0.1% by mass to 20% by mass, even more preferably from 0.1% by mass to 15% by mass, and particularly preferably from 0.1% by mass to 5% by mass, when the sum of all monomer units in the (meth)acrylic adhesive resin (a) is taken as 100% by mass.

Examples of the polymerizable surfactant include those in which a polymerizable 1-propenyl group has been introduced into the benzene ring of polyoxyethylene nonylphenyl ether (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.; trade names: AQUALON RN-10, RN-20, RN-30, RN-50, etc.), those in which a polymerizable 1-propenyl group has been introduced into the benzene ring of an ammonium salt of a sulfate ester of polyoxyethylene nonylphenyl ether (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.; trade names: AQUALON HS-10, HS-20, HS-1025, etc.), and sulfosuccinic acid diesters having a polymerizable double bond in the molecule (manufactured by Kao Corporation; trade names: LATEMULU S-120A, S-180A, etc.).
In the (meth)acrylic adhesive resin (a) according to the present embodiment, the content of the polymerizable surfactant is preferably from 0.1% by mass to 30% by mass, more preferably from 0.1% by mass to 20% by mass, even more preferably from 0.1% by mass to 15% by mass, and particularly preferably from 0.1% by mass to 5% by mass, when the sum of all monomer units in the (meth)acrylic adhesive resin (a) is taken as 100% by mass.

The (meth)acrylic adhesive resin (a) according to this embodiment may further contain, as necessary, monomer units formed from a monomer having a polymerizable double bond, such as vinyl acetate, acrylonitrile, or styrene.

The polymerization reaction mechanism of the (meth)acrylic adhesive resin (a) according to the present embodiment may be radical polymerization, anionic polymerization, cationic polymerization, etc. Taking into consideration the production cost of the (meth)acrylic adhesive resin (a), the effect of the functional group of the monomer, the effect of ions on the surface of the electronic component, etc., it is preferable to polymerize by radical polymerization.
When polymerization is carried out by radical polymerization reaction, the following radical polymerization initiators may be used: benzoyl peroxide, di-t-butyl peroxide, dicumyl peroxide, 3,3,5-trimethylhexanoyl peroxide, di-2-ethylhexyl peroxydicarbonate, methyl ethyl ketone peroxide, t-butyl peroxyphthalate, t-butyl peroxybenzoate, di-t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxy-2-hexanoate, t-butyl peroxy Examples of the peroxide include organic peroxides such as cis-2-ethylhexanoate, t-butylperoxy-3,5,5-trimethylhexanoate, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, t-butyl peroxide, and di-t-amyl peroxide; inorganic peroxides such as ammonium persulfate, potassium persulfate, and sodium persulfate; and azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, and 4,4'-azobis-4-cyanovaleric acid.

When polymerization is performed by emulsion polymerization, among these radical polymerization initiators, inorganic peroxides such as water-soluble ammonium persulfate, potassium persulfate, and sodium persulfate, and azo compounds having a carboxyl group in the molecule such as water-soluble 4,4'-azobis-4-cyanovaleric acid are preferred. Considering the influence of ions on the surface of electronic components, azo compounds having a carboxyl group in the molecule such as ammonium persulfate and 4,4'-azobis-4-cyanovaleric acid are more preferred, and azo compounds having a carboxyl group in the molecule such as 4,4'-azobis-4-cyanovaleric acid are particularly preferred.

The adhesive resin layer (A) according to this embodiment preferably further contains, in addition to the adhesive resin (A1), a crosslinking agent (A2) having two or more crosslinkable functional groups in one molecule.
The crosslinking agent (A2) having two or more crosslinkable functional groups in one molecule can be used to adjust the adhesive strength and cohesive strength by reacting with the functional groups of the adhesive resin (A1).
Examples of such crosslinking agents (A2) include epoxy compounds such as sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, neopentyl glycol diglycidyl ether, and resorcin diglycidyl ether; isocyanate compounds such as tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate triadduct of trimethylolpropane, polyisocyanate, diphenylmethane diisocyanate, and tolylene diisocyanate; and trimethylolpropane-tri-β-aziridinylpropionate. aziridine-based compounds such as N,N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide), N,N'-toluene-2,4-bis(1-aziridinecarboxamide), and trimethylolpropane-tri-β-(2-methylaziridine)propionate; tetrafunctional epoxy-based compounds such as N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane; and melamine-based compounds such as hexamethoxymethylolmelamine. These may be used alone or in combination of two or more.
Among these, it is preferable to contain one or more compounds selected from the group consisting of epoxy compounds, isocyanate compounds, and aziridine compounds.

The content of the crosslinking agent (A2) is usually preferably within a range in which the number of functional groups in the crosslinking agent (A2) is not greater than the number of functional groups in the adhesive resin (A1). However, when new functional groups are generated by the crosslinking reaction or when the crosslinking reaction is slow, the crosslinking agent (A2) may be contained in excess as necessary.
The content of the crosslinking agent (A2) in the adhesive resin layer (A) is preferably 0.1 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the adhesive resin (A1), from the viewpoint of improving the balance between the heat resistance and adhesion of the adhesive resin layer (A).

The adhesive resin layer (A) may contain additives such as plasticizers and tackifier resins as other components. When the adhesive resin layer (A) is a radiation crosslinking adhesive resin layer, it may contain various additives for radiation crosslinking. The total content of the adhesive resin (A1) and the crosslinking agent (A2) in the adhesive resin layer (A) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, when the entire adhesive resin layer (A) is taken as 100% by mass. This makes it possible to further suppress adhesive residue on the electronic component side when peeling the adhesive film from the electronic component.

The adhesive resin layer (A) may be a single layer or a multilayer.
The thickness of the adhesive resin layer (A) is not particularly limited, but is, for example, preferably from 1 μm to 100 μm, and more preferably from 3 μm to 50 μm.

The adhesive resin layer (A) can be formed, for example, by applying an adhesive onto the base layer 10 or the unevenness-absorbing resin layer (C). The adhesive may be dissolved in a solvent and applied as a coating liquid, or may be applied as a water-based emulsion, or the liquid adhesive may be directly applied.
Among these, an aqueous emulsion coating liquid is preferable. Examples of the aqueous emulsion coating liquid include a coating liquid in which a (meth)acrylic adhesive resin (a), a silicone adhesive resin, a urethane adhesive resin, an olefin adhesive resin, a styrene adhesive resin, or the like is dispersed in water.
The adhesive coating solution dissolved in an organic solvent may be used. The organic solvent is not particularly limited, and may be appropriately selected from known solvents in consideration of solubility and drying time. Examples of organic solvents include esters such as ethyl acetate and methyl acetate; ketones such as acetone and MEK; aromatics such as benzene, toluene, and ethylbenzene; linear or cyclic aliphatic solvents such as heptane, hexane, and cyclohexane; and alcohols such as isopropanol and butanol. Ethyl acetate and toluene are preferred as organic solvents. These solvents may be used alone or in combination of two or more.

The adhesive coating liquid can be applied by a conventionally known coating method, such as a roll coater method, reverse roll coater method, gravure roll method, bar coat method, comma coater method, or die coater method. There are no particular restrictions on the drying conditions for the applied adhesive, but it is generally preferable to dry the applied adhesive at a temperature range of 80 to 200°C for 10 seconds to 10 minutes. It is even more preferable to dry the applied adhesive at 80 to 170°C for 15 seconds to 5 minutes. In order to sufficiently promote the crosslinking reaction between the crosslinker and the adhesive, the adhesive coating liquid may be heated at 40 to 80°C for about 5 to 300 hours after drying is complete.

The base layer 10 and the adhesive resin layer (A) or the unevenness-absorbing resin layer (C) may be formed by co-extrusion molding, or may be formed by laminating the film-like base layer 10 and the film-like adhesive resin layer (A). In the examples described later, the adhesive film is manufactured by first forming the adhesive resin layer (A) on the surface of the separator (release film), and then bonding the adhesive resin layer (A) to another layer.

<Adhesive resin layer (B)>
The adhesive film 50 according to this embodiment includes an adhesive resin layer (B) on the second surface 10B side of the base layer 10 opposite to the first surface 10A.
The adhesive resin layer (B) is preferably a layer whose adhesive strength decreases in response to an external stimulus, so that the adhesive film 50 can be easily peeled off from the supporting substrate by applying an external stimulus.
Here, examples of the adhesive resin layer (B) whose adhesive strength is reduced by an external stimulus include a heat-peeling type adhesive resin layer whose adhesive strength is reduced by heating, a light-peeling type adhesive resin layer whose adhesive strength is reduced by light such as radiation, etc. That is, examples of the external stimulus include light energy and heat energy, etc.
Examples of the heat-peelable adhesive resin layer include adhesive resin layers composed of a heat-expandable adhesive that contains an adhesive resin (B1) and further contains a gas-generating component, a heat-expandable adhesive that contains heat-expandable microspheres that can expand to reduce adhesive strength, and a heat-expandable adhesive whose adhesive strength is reduced as a result of a crosslinking reaction of the adhesive component due to heat.

In this embodiment, the thermally expandable adhesive used in the adhesive resin layer (B) is an adhesive whose adhesive strength is reduced or lost by heating, for example, above 150° C., preferably above 170° C. For example, a material can be selected that does not peel off at 150° C. or below or 170° C. or below, but peels off at 150° C. or above or 170° C., and it is preferable that the adhesive film 50 has an adhesive strength such that it does not peel off from the supporting substrate during the manufacturing process of the electronic device.
Here, the decrease or loss of adhesive strength due to heating at over 150°C or over 170°C can be evaluated by, for example, attaching the adhesive resin layer (B) side to a stainless steel plate, performing a heat treatment at 140°C for 1 hour, and then heating at a temperature exceeding 150°C or 170°C for 2 minutes, and then measuring the peel strength from the stainless steel plate. The specific heating temperature when heating at a temperature exceeding 150°C or 170°C is set to a temperature higher than the temperature at which gas is generated or the temperature at which the thermally expandable microspheres thermally expand, and is appropriately set depending on the type of gas generated or the type of thermally expandable microspheres. In this embodiment, the loss of adhesive strength refers to, for example, a case where the 180° peel strength measured under conditions of 23°C and a tensile speed of 300 mm/min is less than 0.5 N/25 mm.

Examples of gas-generating components that can be used in thermal expansion adhesives include azo compounds, azide compounds, and Meldrum's acid derivatives. In addition, inorganic foaming agents such as ammonium carbonate, ammonium bicarbonate, sodium bicarbonate, ammonium nitrite, sodium boron hydroxide, and various azides, water, fluorinated alkane compounds such as trichloromonofluoromethane and dichloromonofluoromethane, azo compounds such as azobisisobutyronitrile, azodicarbonamide, and barium azodicarboxylate, paratoluenesulfonylhydrazide, diphenylsulfone-3,3'-disulfonylhydrazide, 4,4'-oxybis(benzene Hydrazine compounds such as p-toluenesulfonylsemicarbazide and 4,4'-oxybis(benzenesulfonylsemicarbazide); semicarbazide compounds such as 5-morpholyl-1,2,3,4-thiatriazole; organic foaming agents such as N-nitroso compounds such as N,N'-dinitrosopentamethylenetetramine and N,N'-dimethyl-N,N'-dinitrosoterephthalamide can also be used. The gas-generating component may be added to the adhesive resin (B1) or may be directly bonded to the adhesive resin (B1).

As the heat-expandable microspheres used in the heat-expandable pressure-sensitive adhesive, for example, a microencapsulated foaming agent can be used. Examples of such heat-expandable microspheres include microspheres in which a substance that is easily gasified and expanded by heating, such as isobutane, propane, or pentane, is encapsulated in an elastic shell. Examples of materials constituting the shell include vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, and polysulfone. The heat-expandable microspheres can be produced, for example, by a coacervation method or an interfacial polymerization method.
Thermally expandable microspheres can be added to the adhesive resin.

The content of at least one selected from the gas-generating component and the heat-expandable microspheres can be appropriately set depending on the expansion ratio and adhesive strength reduction of the heat-peelable adhesive resin layer (B), and is not particularly limited, but is, for example, 1 part by mass or more and 150 parts by mass or less, preferably 10 parts by mass or more and 130 parts by mass or less, and more preferably 12 parts by mass or more and 100 parts by mass or less, relative to 100 parts by mass of the adhesive resin (B1) in the heat-peelable adhesive resin layer (B).
It is preferable to design the temperature at which gas is generated or the temperature at which the heat-expandable microspheres expand is greater than 150°C or greater than 170°C.

Examples of adhesive resins (B1) constituting the thermally expandable adhesive include (meth)acrylic resins (b), urethane resins, silicone resins, polyolefin resins, polyester resins, polyamide resins, fluorine resins, and styrene-diene block copolymer resins. Among these, (meth)acrylic resins (b) are preferred.

Examples of the (meth)acrylic resin (b) used in the adhesive resin layer (B) include a copolymer containing a (meth)acrylic acid alkyl ester monomer unit (b1) and a monomer unit (b2) having a functional group capable of reacting with a crosslinking agent.
In this embodiment, the (meth)acrylic acid alkyl ester means an acrylic acid alkyl ester, a methacrylic acid alkyl ester, or a mixture thereof.

The (meth)acrylic adhesive resin (b) according to this embodiment can be obtained, for example, by copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester monomer (b1) and a monomer (b2) having a functional group capable of reacting with a crosslinking agent.

Examples of the monomer (b1) forming the (meth)acrylic acid alkyl ester monomer unit (b1) include (meth)acrylic acid alkyl esters having an alkyl group with about 1 to 12 carbon atoms. Preferred are (meth)acrylic acid alkyl esters having an alkyl group with 1 to 8 carbon atoms. Specific examples include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, and the like. These may be used alone or in combination of two or more.
In the (meth)acrylic adhesive resin (b) according to the present embodiment, the content of the (meth)acrylic acid alkyl ester monomer unit (b1) is preferably 10 mass% or more and 98.9 mass% or less, more preferably 50 mass% or more and 97 mass% or less, and even more preferably 85 mass% or more and 95 mass% or less, when the sum of all monomer units in the (meth)acrylic adhesive resin (b) is 100 mass%.

Examples of monomer (b2) that forms monomer (b2) having a functional group that can react with a crosslinking agent include acrylic acid, methacrylic acid, itaconic acid, mesaconic acid, citraconic acid, fumaric acid, maleic acid, itaconic acid monoalkyl ester, mesaconic acid monoalkyl ester, citraconic acid monoalkyl ester, fumaric acid monoalkyl ester, maleic acid monoalkyl ester, glycidyl acrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, methacrylamide, tertiary-butylaminoethyl acrylate, tertiary-butylaminoethyl methacrylate, etc. Preferred are acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, acrylamide, methacrylamide, etc. These may be used alone or in combination of two or more. In the (meth)acrylic adhesive resin (b) according to this embodiment, the content of the monomer unit (b2) is preferably 1% by mass or more and 40% by mass or less, more preferably 1% by mass or more and 20% by mass or less, and even more preferably 1% by mass or more and 10% by mass or less, when the total of all monomer units in the (meth)acrylic adhesive resin (b) is 100% by mass.

The (meth)acrylic adhesive resin (b) according to this embodiment may further contain, in addition to the monomer unit (b1) and the monomer unit (b2), a bifunctional monomer unit (b3) or a specific comonomer unit having surfactant properties (hereinafter referred to as a polymerizable surfactant).
The polymerizable surfactant has the property of copolymerizing with the monomers (b1), (b2) and (b3), and also acts as an emulsifier in the case of emulsion polymerization.

Examples of the monomer (b3) that forms the bifunctional monomer unit (b3) include allyl methacrylate, allyl acrylate, divinylbenzene, vinyl methacrylate, vinyl acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tetraethylene glycol di(meth)acrylate, and, for example, diacrylates at both ends. or dimethacrylate with a main chain structure of propylene glycol type (for example, Nippon Oil & Fats Co., Ltd.; product names: PDP-200, PDP-400, ADP-200, ADP-400), tetramethylene glycol type (for example, Nippon Oil & Fats Co., Ltd.; product names: ADT-250, ADT-850), and mixtures of these types (for example, Nippon Oil & Fats Co., Ltd.; product names: ADET-1800, ADPT-4000).

In the (meth)acrylic adhesive resin (b) according to this embodiment, the content of the monomer unit (b3) is preferably from 0.1% by mass to 30% by mass, more preferably from 0.1% by mass to 20% by mass, even more preferably from 0.1% by mass to 15% by mass, and particularly preferably from 0.1% by mass to 5% by mass, when the sum of all monomer units in the (meth)acrylic adhesive resin (b) is taken as 100% by mass.

Examples of the polymerizable surfactant include those in which a polymerizable 1-propenyl group has been introduced into the benzene ring of polyoxyethylene nonylphenyl ether (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.; trade names: AQUALON RN-10, RN-20, RN-30, RN-50, etc.), those in which a polymerizable 1-propenyl group has been introduced into the benzene ring of an ammonium salt of a sulfate ester of polyoxyethylene nonylphenyl ether (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.; trade names: AQUALON HS-10, HS-20, HS-1025, etc.), and sulfosuccinic acid diesters having a polymerizable double bond in the molecule (manufactured by Kao Corporation; trade names: LATEMULU S-120A, S-180A, etc.).
In the (meth)acrylic adhesive resin (b) according to the present embodiment, the content of the polymerizable surfactant is preferably 0.1 mass % or more and 30 mass % or less, more preferably 0.1 mass % or more and 20 mass % or less, even more preferably 0.1 mass % or more and 15 mass % or less, and particularly preferably 0.1 mass % or more and 5 mass % or less, when the sum of all monomer units in the (meth)acrylic adhesive resin (b) is 100 mass %.

The (meth)acrylic adhesive resin (b) according to this embodiment may further contain, as necessary, monomer units formed from a monomer having a polymerizable double bond, such as vinyl acetate, acrylonitrile, or styrene.

The polymerization reaction mechanism of the (meth)acrylic adhesive resin (b) according to the present embodiment may be radical polymerization, anionic polymerization, cationic polymerization, etc. In consideration of the production cost of the (meth)acrylic adhesive resin (b), the effect of the functional group of the monomer, the effect of ions on the surface of the electronic component, etc., it is preferable to polymerize by radical polymerization.
When polymerization is carried out by radical polymerization reaction, the following radical polymerization initiators may be used: benzoyl peroxide, di-t-butyl peroxide, dicumyl peroxide, 3,3,5-trimethylhexanoyl peroxide, di-2-ethylhexyl peroxydicarbonate, methyl ethyl ketone peroxide, t-butyl peroxyphthalate, t-butyl peroxybenzoate, di-t-butyl peroxyacetate, t-butyl peroxyisobutyrate, t-butyl peroxy-2-hexanoate, t-butyl peroxy Examples of the peroxide include organic peroxides such as cis-2-ethylhexanoate, t-butylperoxy-3,5,5-trimethylhexanoate, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, t-butyl peroxide, and di-t-amyl peroxide; inorganic peroxides such as ammonium persulfate, potassium persulfate, and sodium persulfate; and azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, and 4,4'-azobis-4-cyanovaleric acid.

When polymerization is performed by emulsion polymerization, among these radical polymerization initiators, inorganic peroxides such as water-soluble ammonium persulfate, potassium persulfate, and sodium persulfate, and azo compounds having a carboxyl group in the molecule such as water-soluble 4,4'-azobis-4-cyanovaleric acid are preferred. Considering the influence of ions on the surface of electronic components, azo compounds having a carboxyl group in the molecule such as ammonium persulfate and 4,4'-azobis-4-cyanovaleric acid are more preferred, and azo compounds having a carboxyl group in the molecule such as 4,4'-azobis-4-cyanovaleric acid are particularly preferred.

The adhesive resin layer (B) according to this embodiment preferably further contains, in addition to the adhesive resin (B1), a crosslinking agent (B2) having two or more crosslinkable functional groups in one molecule.
The crosslinking agent (B2) having two or more crosslinkable functional groups in one molecule is used to adjust the adhesive strength and cohesive strength by reacting with the functional groups of the adhesive resin (B1).
Examples of such crosslinking agents (B2) include epoxy compounds such as sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, neopentyl glycol diglycidyl ether, and resorcin diglycidyl ether; isocyanate compounds such as tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate triadduct of trimethylolpropane, polyisocyanate, diphenylmethane diisocyanate, and tolylene diisocyanate; and trimethylolpropane-tri-β-aziridinylpropionate. aziridine-based compounds such as N,N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide), N,N'-toluene-2,4-bis(1-aziridinecarboxamide), and trimethylolpropane-tri-β-(2-methylaziridine)propionate; tetrafunctional epoxy-based compounds such as N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane; and melamine-based compounds such as hexamethoxymethylolmelamine. These may be used alone or in combination of two or more.
Among these, it is preferable to contain one or more compounds selected from the group consisting of epoxy compounds, isocyanate compounds, and aziridine compounds.

The content of the crosslinking agent (B2) is usually preferably within a range in which the number of functional groups in the crosslinking agent (B2) is not greater than the number of functional groups in the adhesive resin (B1). However, when new functional groups are generated by the crosslinking reaction or when the crosslinking reaction is slow, an excess amount of the crosslinking agent (B2) may be contained as necessary.
The content of the crosslinking agent (B2) in the adhesive resin layer (B) is preferably 0.1 parts by mass or more and 10 parts by mass or less, and more preferably 0.5 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the adhesive resin (B1).

In order to improve adhesion to the support substrate, the adhesive resin layer (B) according to this embodiment preferably contains a tackifier resin in addition to the adhesive resin (B1). It is preferable to include a tackifier resin in the adhesive resin layer (B) because it is easy to adjust the adhesion to the support substrate at around room temperature. The tackifier resin is preferably one whose softening point is 100°C or higher. Specific examples of tackifier resins include rosin-based resins such as rosin-based derivatives that have been treated with esterification or the like; terpene-based resins such as α-pinene-based, β-pinene-based, dipentene-based, and terpene phenol-based resins; natural rosins such as gum-based, wood-based, and tall oil-based resins; hydrogenated, disproportionated, polymerized, maleated, and petroleum resins of these natural rosins; coumarone-indene resins, etc. can be mentioned.

Among these, those with a softening point in the range of 100 to 160°C are more preferred, and those in the range of 120 to 150°C are particularly preferred. Using a tackifier resin with a softening point in the above range not only reduces contamination and adhesive residue on the support substrate, but also makes it possible to further improve adhesion to the support substrate in the working environment. Furthermore, using a polymerized rosin ester-based tackifier resin as the tackifier resin not only reduces contamination and adhesive residue on the support substrate, but also improves adhesion to the support substrate in an environment of 80 to 130°C, and in the case of a heat-expandable adhesive containing heat-expandable microspheres, it becomes even easier to peel the adhesive from the support substrate after the heat-expandable microspheres expand.

The mixing ratio of the tackifier resin is not particularly limited, and may be appropriately selected so that the elastic modulus of the adhesive resin layer (B) can be adjusted within a desired predetermined numerical range. However, in terms of the elastic modulus and initial peeling force of the adhesive resin layer (B), it is preferable to set the mixing ratio to 1 to 100 parts by mass for 100 parts by mass of the adhesive resin (B1). When the mixing ratio of the tackifier resin is equal to or greater than the lower limit value for 100 parts by mass of the adhesive resin (B1), the adhesion to the support substrate during operation tends to be good. On the other hand, when it is equal to or less than the upper limit value, the attachment to the support substrate at room temperature tends to be good. In terms of the adhesion to the support substrate and the attachment at room temperature, it is more preferable to set the mixing ratio of the tackifier resin to 2 to 50 parts by mass for 100 parts by mass of the adhesive resin (B1). In addition, the acid value of the tackifier resin is preferably 30 or less. When the acid value of the tackifier resin is equal to or less than the upper limit value, adhesive residue tends to be less likely to be left on the support substrate during peeling.

The adhesive resin layer (B) may contain additives such as plasticizers as other components. The total content of the adhesive resin (B1), crosslinking agent (B2) and tackifier resin in the adhesive resin layer (B) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, when the entire adhesive resin layer (B) is taken as 100% by mass. Furthermore, when the adhesive resin layer (B) is composed of a heat-expandable adhesive, the total content of the adhesive resin (B1), crosslinking agent (B2), tackifier resin, gas-generating component and heat-expandable microspheres in the adhesive resin layer (B) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, when the entire adhesive resin layer (B) is taken as 100% by mass.

The adhesive resin layer (B) may be a single layer or a multilayer. For example, by laminating two or more layers having different degrees of expansion by heating to form the adhesive resin layer (B), the adhesiveness/thermal peelability can be changed between one side and the other side of the adhesive resin layer (B).
The thickness of the adhesive resin layer (B) is not particularly limited, but is preferably, for example, from 3 μm to 300 μm, and more preferably from 20 μm to 150 μm.

The adhesive resin layer (B) can be formed, for example, by a method of applying an adhesive coating liquid onto the base layer 10, or by transferring the adhesive resin layer (B) formed on a separator onto the base layer 10.
The adhesive coating liquid can be coated by a conventional coating method such as a roll coater method, a reverse roll coater method, a gravure roll method, a bar coat method, a comma coater method, a die coater method, etc. There is no particular restriction on the drying conditions of the coated adhesive, but it is generally preferable to dry the coated adhesive at a temperature range of 80 to 200°C for 10 seconds to 10 minutes. More preferably, the coated adhesive is dried at 80 to 170°C for 15 seconds to 5 minutes. In order to sufficiently promote the crosslinking reaction between the crosslinking agent and the adhesive, the adhesive coating liquid may be heated at 40 to 80°C for about 5 to 300 hours after drying is completed.
The base material layer 10 and the adhesive resin layer (B) may be formed by co-extrusion molding, or the base material layer 10 in the form of a film and the adhesive resin layer (B) in the form of a film may be laminated together.

<Irregularity-absorbing resin layer (C)>
The adhesive film 50 of this embodiment has an unevenness-absorbing resin layer (C) that can be crosslinked by light energy and thermal energy between the base layer 10 and the adhesive resin layer (A) or between the base layer 10 and the adhesive resin layer (B).
The unevenness-absorbing resin layer (C) is a layer provided for the purpose of improving the conformability of the adhesive film 50 to the surface of the electronic component on which the uneven structure is formed, and improving the adhesion between the electronic component having the uneven structure and the adhesive film 50. Furthermore, the unevenness-absorbing resin layer (C) can be crosslinked and cured by light energy and thermal energy to increase the elastic modulus of the unevenness-absorbing resin layer (C). This makes it possible to suppress the electronic component from sinking into the adhesive film during the sealing process of the electronic component.

The resin constituting the unevenness-absorbing resin layer (C) is not particularly limited as long as it exhibits unevenness-absorbing properties, and is preferably, for example, a thermoplastic resin. Specifically, one or more selected from the group consisting of polyolefin-based resins, polystyrene-based resins, and (meth)acrylic resins are more preferable. From another perspective, a resin having a Shore D hardness according to ASTM D-2240 Shore D hardness of preferably 50 or less, more preferably 40 or less is preferable.
Even when the resin constituting the irregularity-absorbing resin layer (C) is not a thermoplastic resin, it is preferable that the resin has the same irregularity-absorbing property as described above.

The unevenness-absorbing resin layer (C) preferably contains a resin, a crosslinking agent, a photoinitiator that generates active chemical species by light, and a thermal initiator that generates active chemical species by heat. By containing these components in the unevenness-absorbing resin layer (C), the unevenness-absorbing resin layer (C) can be crosslinked more effectively by light energy and thermal energy, and the elastic modulus of the unevenness-absorbing resin layer (C) can be further improved. This makes it possible to suppress the unevenness-absorbing resin layer from softening due to heat in the process of sealing the electronic components with the sealing material, and as a result, it is possible to further suppress the electronic components from sinking into the adhesive film 50 due to the pressure of the sealing material.
Depending on the chemical structure and reactivity of the resin and crosslinking agent, the unevenness-absorbing resin layer (C) may be crosslinked (cured) by light energy and thermal energy even if it does not necessarily contain an initiator.

The resin that can be used to form the unevenness-absorbing resin layer (C) is not particularly limited, but preferable examples include the resins described above as the adhesive resin (B1) in the adhesive resin layer (B).
Other resins that can be used to form the unevenness-absorbing resin layer (C) are not particularly limited, and examples thereof include olefin-based resins such as ethylene-α-olefin copolymers containing ethylene and an α-olefin having 3 to 20 carbon atoms, high-density ethylene resins, low-density ethylene resins, medium-density ethylene resins, very low-density ethylene resins, linear low-density polyethylene (LLDPE) resins, propylene (co)polymers, 1-butene (co)polymers, 4-methylpentene-1 (co)polymers, ethylene-cyclic olefin copolymers, ethylene-α-olefin-cyclic olefin copolymers, ethylene-α-olefin-non-conjugated polyene copolymers, ethylene-α-olefin-conjugated polyene copolymers, ethylene-aromatic vinyl copolymers, and ethylene-α-olefin-aromatic vinyl copolymers; ethylene-unsaturated carboxylic anhydride copolymers, ethylene-α-olefin-unsaturated olefin-based resins, and the like. ethylene-carboxylic acid anhydride copolymers such as ethylene-epoxy-containing unsaturated compound copolymers and ethylene-α-olefin-epoxy-containing unsaturated compound copolymers; ethylene-(meth)acrylic acid ester copolymers such as ethylene-ethyl (meth)acrylate copolymer, ethylene-methyl (meth)acrylate copolymer, ethylene-propyl (meth)acrylate copolymer, ethylene-butyl (meth)acrylate copolymer, ethylene-hexyl (meth)acrylate copolymer, ethylene-2-hydroxyethyl (meth)acrylate copolymer, ethylene-2-hydroxypropyl (meth)acrylate copolymer, and ethylene-glycidyl (meth)acrylate copolymer; ethylene-(meth)acrylic acid copolymer, ethylene-maleic acid copolymer, ethylene-fumaric acid copolymer, ethylene-(meth)acrylic acid copolymer, Ethylene-ethylenically unsaturated acid copolymers such as ethylene-crotonic acid copolymer; ethylene-vinyl acetate copolymer, ethylene-vinyl propionate copolymer, ethylene-vinyl butyrate copolymer, ethylene-vinyl stearate copolymer, and other ethylene-vinyl ester copolymers; ethylene-styrene copolymers; unsaturated carboxylic acid ester (co)polymers such as (meth)acrylic acid ester (co)polymers; ionomer resins such as ethylene-metal acrylic acid copolymers and ethylene-metal methacrylic acid copolymers; urethane-based resins; silicone-based resins; acrylic acid-based resins; methacrylic acid-based resins; cyclic olefin (co)polymers; α-olefin-aromatic vinyl compound-aromatic polyene copolymers; ethylene-α-olefin-aromatic vinyl compound; aromatic polyene copolymers; ethylene-aromatic vinyl compound-aromatic polyene copolymers; styrene One or more types selected from the following can be used: thermoplastic elastomers; acrylonitrile-butadiene-styrene copolymers; styrene-conjugated diene copolymers; acrylonitrile-styrene copolymers; acrylonitrile-ethylene-α-olefin-non-conjugated polyene-styrene copolymers; acrylonitrile-ethylene-α-olefin-conjugated polyene-styrene copolymers; methacrylic acid-styrene copolymers; ethylene terephthalate resins; fluororesins; polyester carbonates; polyvinyl chloride; polyvinylidene chloride; polyolefin-based thermoplastic elastomers; polystyrene-based thermoplastic elastomers; polyurethane-based thermoplastic elastomers; 1,2-polybutadiene-based thermoplastic elastomers; trans-polyisoprene-based thermoplastic elastomers; chlorinated polyethylene-based thermoplastic elastomers; liquid crystalline polyesters; polylactic acid, etc.
The irregularity-absorbing resin layer (C) may contain only one resin, or may contain two or more resins.

The crosslinking agent that can be contained in the unevenness-absorbing resin layer (C) is not particularly limited, and may be any agent that undergoes a crosslinking reaction due to a chemical species generated from an initiator.
Preferred crosslinking agents include polyfunctional (meth)acrylate compounds and isocyanate compounds. More specifically, urethane (meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol monohydroxypenta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,4-butanediol di(meth)acrylate, and the like; and isocyanate compounds such as tetramethylene diisocyanate, hexamethylene diisocyanate, toluene diisocyanate triadduct of trimethylolpropane, polyisocyanate, diphenylmethane diisocyanate, and tolylene diisocyanate.
Examples of the crosslinking agent include various monomers or oligomers such as urethane-based, polyether-based, polyester-based, polycarbonate-based, and polybutadiene-based.
The amount of the crosslinking agent is, for example, 5 parts by mass or more and 500 parts by mass or less, and preferably 40 parts by mass or more and 150 parts by mass or less, per 100 parts by mass of the resin (base polymer) such as a (meth)acrylic polymer.

From another perspective, the unevenness-absorbing resin layer (C) may contain one or more crosslinking agents (A2) that can be contained in the adhesive resin layer (A) described above. Specifically, the unevenness-absorbing resin layer (C) may contain an isocyanate-based compound. When such a crosslinking agent is used, the amount is, for example, 0.01 parts by mass or more and 5 parts by mass or less, preferably 0.01 parts by mass or more and 3 parts by mass or less, relative to 100 parts by mass of the resin (base polymer).

The photoinitiator that can be contained in the unevenness-absorbing resin layer (C) is not particularly limited as long as it is capable of crosslinking the resin and/or crosslinking agent in the unevenness-absorbing resin layer (C) by light energy.
The chemical species generated from the photoinitiator may be appropriately selected based on the functional groups of the resin and/or crosslinker. The chemical species generated from the photoinitiator is typically a radical or a cation.

As the photoinitiator, an alkylphenone-based photoinitiator, an acetophenone-based photoinitiator, an oxime ester-based photoinitiator, a benzoin ether-based photoinitiator, an acylphosphine oxide-based photoinitiator, an α-ketol-based photoinitiator, an aromatic sulfonyl chloride-based photoinitiator, a photoactive oxime-based photoinitiator, a benzoin-based photoinitiator, a benzyl-based photoinitiator, a benzophenone-based photoinitiator, a thioxanthone-based photoinitiator, etc. can be used. The photoinitiator can be used alone or in appropriate combination of two or more kinds. Among these, it is preferable to include an alkylphenone-based photoinitiator from the viewpoint of high reactivity and low sublimation.

Specific examples of alkylphenone photoinitiators include 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-propan-1-one, 2-hydroxy-1-{[4-(2-hydroxy-2-methyl-propionyl)-benzyl]phenyl}-2-methyl-propan-1-one, and the like.
Specific examples of acetophenone-based photoinitiators include 1-hydroxycyclohexyl-phenyl-ketone, 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, methoxyacetophenone, and the like.
Specific examples of oxime ester photoinitiators include 1,2-octanedione, 1-[4-(phenylthio)phenyl]-2-(o-benzoyloxime), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-1-(o-acetyloxime), and the like.
Specific examples of benzoin ether photoinitiators include benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, and benzoin isobutyl ether, and substituted benzoin ethers such as anisole methyl ether.
Specific examples of the acylphosphine oxide photoinitiator include bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and the like.
Specific examples of the α-ketol photoinitiator include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)phenyl]-2-methylpropan-1-one, and the like.
Specific examples of aromatic sulfonyl chloride photoinitiators include 2-naphthalenesulfonyl chloride.
Specific examples of photoactive oxime-based photoinitiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime, and the like.
Specific examples of benzoin-based photoinitiators include benzoin.
Specific examples of benzyl-based photoinitiators include benzyl and the like.
Specific examples of benzophenone-based photoinitiators include benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, and α-hydroxycyclohexyl phenyl ketone.
Specific examples of thioxanthone-based photoinitiators include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone.

As the photoinitiator, a photoinitiator that absorbs light having a wavelength of 300 nm or more (for example, light having a wavelength of 300 nm or more and 500 nm or less) and generates radicals can be preferably used. The photoinitiators can be used alone or in appropriate combination of two or more types.

The content of the photoinitiator in the unevenness-absorbing resin layer (C) is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100 parts by mass of the resin (base polymer) such as a (meth)acrylic polymer. From the viewpoint of storage stability, the content is preferably 7 parts by mass or less, and more preferably 3 parts by mass or less.

The thermal initiator that may be contained in the unevenness-absorbing resin layer (C) is not particularly limited as long as it is capable of crosslinking the resin and/or crosslinking agent in the unevenness-absorbing resin layer (C) by thermal energy.
The chemical species generated from the thermal initiator may be appropriately selected based on the functional groups possessed by the resin and/or the crosslinking agent, and is typically a radical or a cation.

Examples of thermal initiators include aromatic ketones, onium salt compounds, organic peroxides, thio compounds, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and azo compounds. These may be used alone or in combination of two or more.
Among these, azo compounds and organic peroxides are preferred from the viewpoints of availability and ease of handling, and organic peroxides are more preferred.

Commercially available thermal initiators include V-70, V-65, V-601, V-59, V-40, VF-096, V-30, VAm-110, VAm-111 (all manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), Niper BW, Niper BMT, Peroyl TCP, Peroyl L, Peroyl 355, Peroyl SA, Perhexa HC, Perbutyl 355, Perbutyl D, Perbutyl L, Perbutyl ND, Perocta O, Perhexyl D, Perhexyl O, Perhexyl PV (all manufactured by NOF Corp.), Trigonox 36-C75, Laurox, Perkadox L-W75, Perkadox CH-50L, Trigonox TMBH, Kayacumene H, Kayabutyl H-70, Perkadox BC-FF, Kayahexyl SA AD, Perkadox 14, Kayabutyl C, Kayabutyl D, Perkadox 12-XL25, Trigonox 22-N70 (22-70E), Trigonox D-T50, Trigonox 423-C70, Kayaester CND-C70, Trigonox 23-C70, Trigonox 257-C70, Kayaester P-70, Kayaester TMPO-70, Trigonox 121, Kayaester O, Kayaester HTP-65W, Kayaester AN, Trigonox 42, Trigonox F-C50, Kayabutyl B, Kayacarvone EH, Kayacarvone I-20, Kayacarvone BIC-75, Trigonox 117, Kayalene 6-70 (all manufactured by Kayaku Akzo Co., Ltd.)

The content of the thermal initiator in the unevenness-absorbing resin layer (C) is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100 parts by mass of the resin (base polymer) such as a (meth)acrylic polymer. From the viewpoint of storage stability, the content is preferably 7 parts by mass or less, and more preferably 3 parts by mass or less.

In the adhesive film 50 according to this embodiment, the lower limit of the storage modulus E' at 60°C of the unevenness-absorbing resin layer (C) before crosslinking is preferably 1.0 x ¹⁰³ Pa or more, and more preferably 5.0 x ¹⁰³ Pa or more, since this can further suppress sinking of electronic components into the adhesive film during the sealing process of the electronic components.
In addition, in the adhesive film 50 according to this embodiment, the upper limit of the storage modulus E' at 60°C of the unevenness-absorbing resin layer (C) before crosslinking is preferably 1.0 x ¹⁰⁶ Pa or less, and more preferably 5.0 x ¹⁰⁵ Pa or less, in order to effectively absorb the unevenness on the chip surface and to prevent deterioration of the unevenness absorption over time due to springback of the resin.
The storage modulus E' at 60°C of the unevenness-absorbing resin layer (C) before crosslinking can be controlled within the above range, for example, by controlling the types and blending ratios of each component constituting the unevenness-absorbing resin layer (C).

In the adhesive film 50 according to this embodiment, the lower limit of the storage modulus E' at 125°C of the unevenness-absorbing resin layer (C') obtained by crosslinking the unevenness-absorbing resin layer (C) is preferably 1.0 x 10 ⁶ Pa or more, and more preferably 5.0 x 10 ⁶ Pa or more, since this can further suppress the sinking of electronic components into the adhesive film during the sealing process of the electronic components.
In addition, in the adhesive film 50 according to this embodiment, the upper limit of the storage modulus E' of the unevenness-absorbing resin layer (C') at 125°C is preferably 1.0 x ¹⁰⁹ Pa or less, and more preferably 1.0 x ¹⁰⁸ Pa or less, in order to further suppress the misalignment of electronic components during the sealing process.
The storage modulus E' at 125° C. of the unevenness-absorbing resin layer (C') can be controlled within the above range, for example, by controlling the types and blending ratios of each component constituting the unevenness-absorbing resin layer (C).
Here, whether or not the crosslinking treatment of the unevenness-absorbing resin layer (C) is completed can be determined, for example, by determining the point at which the storage modulus E' of the unevenness-absorbing resin layer (C) no longer increases even after the crosslinking treatment.

The thickness of the unevenness-absorbing resin layer (C) is not particularly limited as long as it is a thickness that can embed the uneven structure of the electronic component, but for example, it is preferably 5 μm or more and 1000 μm or less, more preferably 20 μm or more and 900 μm or less, even more preferably 30 μm or more and 800 μm or less, and particularly preferably 50 μm or more and 700 μm or less.

Here, the uneven structure of the electronic component preferably includes a bump electrode. When the uneven structure of the electronic component includes a bump electrode, when the height of the bump electrode is H [μm] and the thickness of the unevenness-absorbing resin layer (C) is d [μm], H/d is preferably 1 or less, more preferably 0.85 or less, and even more preferably 0.7 or less. When H/d is equal to or less than the upper limit, the thickness of the adhesive film 50 can be made thinner while improving the unevenness absorption.
The lower limit of H/d is not particularly limited, but is, for example, 0.01 or more. The height of the bump electrode is generally 2 μm or more and 600 μm or less.

The method for forming the unevenness-absorbing resin layer (C) is not particularly limited, and the same method as for the adhesive resin layer (A) and the adhesive resin layer (B) can be used.

<Other demographics>
The adhesive film 50 according to this embodiment may further include, for example, an easy-adhesion layer between each layer, as long as the effect of this embodiment is not impaired.

2. Method for Manufacturing an Electronic Device Next, a method for manufacturing an electronic device according to the present embodiment will be described below. 2 and 3 are cross-sectional views that are schematic diagrams showing an example of a method for manufacturing an electronic device according to the embodiment of the present invention.
The method for manufacturing an electronic device according to this embodiment includes at least the following three steps.
(1)
an adhesive film 50 including a base layer 10, an adhesive resin layer (A) provided on a first surface 10A side of the base layer 10 and for temporarily fixing an electronic component 70, an adhesive resin layer (B) provided on a second surface 10B side of the base layer 10, and an unevenness-absorbing resin layer (C) provided between the base layer 10 and the adhesive resin layer (A) or between the base layer 10 and the adhesive resin layer (B) and crosslinkable by light energy and thermal energy;
(1) a preparation step of preparing a structure 100 including an electronic component 70 attached to the adhesive resin layer (A) of the adhesive film 50 and having an uneven structure 75; (2) a crosslinking step of crosslinking the unevenness-absorbing resin layer (C) in the structure 100 by applying light energy and heat energy to the unevenness-absorbing resin layer (C); and (3) a sealing step of sealing the electronic component 70 with a sealing material 60.

Below, we will explain each step of the manufacturing method for electronic devices according to this embodiment.

((1) Preparation process)
In the preparation step, a structure 100 is prepared, which includes an adhesive film 50 and an electronic component 70 attached to the adhesive resin layer (A) of the adhesive film 50 and having a concave-convex structure 75. Here, it is preferable that the structure 100 further includes a support substrate 80 attached to the adhesive resin layer (B) of the adhesive film 50.

Such a structure 100 can be fabricated, for example, by the following procedure.
First, the adhesive film 50 is attached onto the support substrate 80 so that the adhesive resin layer (B) faces the support substrate 80. A protective film called a separator may be attached onto the adhesive resin layer (B), and the protective film may be peeled off, and the exposed surface of the adhesive resin layer (B) may be attached to the surface of the support substrate 80.
The support substrate 80 may be, for example, a quartz substrate, a glass substrate, or a SUS substrate.

Next, the electronic component 70 is disposed on the adhesive resin layer (A) of the adhesive film 50, whereby the structure 100 can be obtained.
Examples of the electronic component 70 include semiconductor chips such as ICs, LSIs, discrete devices, light-emitting diodes, and light-receiving elements, semiconductor panels, and semiconductor packages.
The surface of the electronic component 70 has an uneven structure 75 due to, for example, the presence of electrodes.
Furthermore, for example, when mounting an electronic device on a mounting surface, the electrodes are joined to electrodes formed on the mounting surface to form an electrical connection between the electronic device and the mounting surface (a mounting surface of a printed circuit board, etc.).
Examples of the electrodes include bump electrodes such as ball bumps, printed bumps, stud bumps, plated bumps, and pillar bumps. That is, the electrodes are usually convex electrodes. These bump electrodes may be used alone or in combination of two or more types.
The metal species constituting the bump electrode is not particularly limited, and examples thereof include silver, gold, copper, tin, lead, bismuth, and alloys thereof. These metal species may be used alone or in combination of two or more.

((2) Crosslinking step)
Next, light energy and heat energy are applied to the unevenness-absorbing resin layer (C) in the structure 100 to crosslink the unevenness-absorbing resin layer (C). That is, the unevenness-absorbing resin layer (C) in the structure 100 is crosslinked by applying light energy to the unevenness-absorbing resin layer (C) by irradiating it with light and applying heat energy by heating.
At this time, the light irradiation and the heating may be performed sequentially or simultaneously, but it is preferable to perform the first crosslinking step of crosslinking the unevenness-absorbing resin layer (C) by irradiating the unevenness-absorbing resin layer (C) with light, and the second crosslinking step of further crosslinking the unevenness-absorbing resin layer (C) by heating the unevenness-absorbing resin layer (C) in this order. That is, in the manufacturing method of the electronic device of this embodiment, it is preferable that the (2) crosslinking step at least includes the first crosslinking step of crosslinking the unevenness-absorbing resin layer (C) by irradiating the structure with light, and the second crosslinking step of further crosslinking the unevenness-absorbing resin layer (C) by heating the structure.

The unevenness-absorbing resin layer (C) is crosslinked and cured by irradiating the unevenness-absorbing resin layer (C) with light such as ultraviolet light. The light source used at this time is not particularly limited, but it is preferable to use a light source capable of irradiating ultraviolet light containing a wavelength component capable of exciting a photoinitiator, and it is more preferable to use a light source capable of irradiating ultraviolet light containing a component with a wavelength of less than 300 nm. Examples of such light sources include high-pressure mercury lamps, low-pressure mercury lamps, metal halide lamps, super UV lamps, etc. The light irradiated by the light source may contain a component with a wavelength of 300 nm or more.
In the case of ultraviolet crosslinking, for example, the unevenness-absorbing resin layer (C) can be crosslinked and cured by irradiating the unevenness-absorbing resin layer (C ⁾ with ultraviolet light having a main wavelength of 365 nm using a high-pressure mercury lamp under conditions of an irradiation intensity of 10 to 350 mW/ ^cm2 and an amount of ultraviolet light of 100 to 20,000 mJ/cm2 in an environment of 0 to 60°C.

The method of crosslinking the unevenness-absorbing resin layer (C) by heating is not limited, but preferred examples include thermal crosslinking in an oven, thermal crosslinking on a hot plate, and thermal crosslinking by infrared radiation. In the case of the above thermal crosslinking, the heating temperature is, for example, 100°C to 180°C, and the heat treatment time is, for example, 10 to 180 minutes. It is preferable that the heating temperature does not exceed the temperature at which gas is generated or the temperature at which the heat-expandable microspheres thermally expand.

((3) Sealing process)
Next, the electronic components 70 are sealed with a sealing material 60 .
The electronic component 70 is covered with the sealing material 60, and the sealing material 60 is cured at a temperature of, for example, 150° C. or less or 170° C. or less to seal the electronic component 70. When the adhesive resin layer (B) of the adhesive film 50 contains at least one selected from a gas-generating component and heat-expandable microspheres, the temperature for curing the sealing material 60 is preferably within a range not exceeding the temperature at which gas is generated or the temperature at which the heat-expandable microspheres thermally expand.
The form of the sealing material 60 is not particularly limited, but may be, for example, granular, sheet-like, or liquid.

As the sealing material 60, it is preferable to use one or two types selected from an epoxy resin-based sealing material using an epoxy resin and a silicone resin-based sealing material using a silicone resin.
In particular, a liquid epoxy resin-based or silicone resin-based sealing material is preferred, since this improves the affinity of the sealing material 60 to the adhesive film 50 and enables the electronic component 70 to be sealed more evenly.
As such an epoxy resin-based sealing material, for example, T693/R4000 series, T693/R1000 series, T693/R5000 series, etc. manufactured by Nagase ChemteX Corporation can be used.
Examples of such silicone resin-based sealing materials that can be used include KMC-8400 manufactured by Shin-Etsu Chemical Co., Ltd., and TSE3033 and TSE3251 manufactured by Momentive Performance Materials Japan, Inc.

Examples of sealing methods include transfer molding, injection molding, compression molding, and cast molding. After sealing the electronic component 70 with the sealing material 60, the sealing material 60 is cured by heating at a temperature of, for example, 150° C. or less or 170° C. or less, to obtain a structure 100 in which the electronic component 70 is sealed.

((4) First peeling step)
In the method for manufacturing an electronic device according to this embodiment, as shown in FIG. 3(4), after the sealing step (3), a first peeling step of applying an external stimulus to reduce the adhesive strength of the adhesive resin layer (B) to peel off the support substrate 80 from the structure 100 may be further provided.
The support substrate 80 can be easily removed from the adhesive film 50, for example, by heating the support substrate 80 to a temperature exceeding 150°C or a temperature exceeding 170°C after sealing the electronic component 70, thereby reducing the adhesive strength of the adhesive resin layer (B).

((5) Second peeling step)
In the method for manufacturing an electronic device according to this embodiment, as shown in FIG. 3 (5), after the first peeling step, a second peeling step may be further provided in which the adhesive film 50 is peeled off from the electronic component 70 to obtain the electronic device 200.
Examples of methods for peeling the adhesive film 50 from the electronic component 70 include a mechanical peeling method and a method in which the adhesive strength of the surface of the adhesive film 50 is reduced before peeling.

(Other processes)
The method for manufacturing an electronic device according to this embodiment may further include a step (6) of forming a wiring layer 310 and a bump 320 on the exposed surface of the obtained electronic device 200, as shown in FIG. 3 (6), to obtain the electronic device 300.

The wiring layer 310 includes pads (not shown) that are external connection terminals formed on the outermost surface, and wiring (not shown) that electrically connects the exposed electronic components 70 to the pads. The wiring layer 310 can be formed by a conventionally known method, and may have a multi-layer structure.

Then, bumps 320 are formed on the pads of the wiring layer 310, and the electronic device 300 can be obtained. Examples of the bumps 320 include solder bumps and gold bumps. Solder bumps can be formed, for example, by placing solder balls on the pads that are the external connection terminals of the wiring layer 310 and heating the solder to melt (reflow). Gold bumps can be formed by ball bonding, plating, Au ball transfer, or other methods.

Furthermore, the method for manufacturing an electronic device according to this embodiment may further include a step (7) of dicing the electronic device 300 to obtain a plurality of electronic devices 400, as shown in FIG.
The electronic device 300 can be diced by a known method.

As another embodiment, the method for producing an electronic device according to the present embodiment may be configured not to use the adhesive resin layer (B). That is, as another embodiment, the method for producing an electronic device according to the present embodiment includes at least the following four steps.
(1)
an adhesive film (50) including a base layer (10), an adhesive resin layer (A) provided on a first surface (10A) of the base layer (10) for temporarily fixing an electronic component (70), and an unevenness-absorbing resin layer (C) provided between the base layer (10) and the adhesive resin layer (A) and capable of being crosslinked by light energy and thermal energy;
(2) a first crosslinking step of crosslinking the unevenness-absorbing resin layer (C) in the structure 100 by irradiating the unevenness-absorbing resin layer (C) in the structure 100 with light; (3) a second crosslinking step of further crosslinking the unevenness-absorbing resin layer (C) in the structure 100 by heating the unevenness-absorbing resin layer (C); and (4) a sealing step of sealing the electronic component 70 with a sealing material 60.

The above describes embodiments of the present invention, but these are merely examples of the present invention, and various configurations other than those described above can also be adopted.

The present invention is not limited to the above-mentioned embodiment, and any modifications or improvements that can achieve the object of the present invention are included in the present invention.

The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.
The details of the method for producing the adhesive film are as follows.

<Synthesis (polymerization) of adhesive raw materials for forming the unevenness-absorbing resin layer (C), adhesive resin layer (A) or adhesive resin layer (B)>

(Meth)acrylic resin solution 1:
49 parts by mass of ethyl acrylate, 20 parts by mass of 2-ethylhexyl acrylate, 21 parts by mass of methyl acrylate, 10 parts by mass of glycidyl methacrylate, and 0.5 parts by mass (solid content equivalent) of a benzoyl peroxide-based polymerization initiator as a polymerization initiator were reacted in 65 parts by mass of toluene and 50 parts by mass of ethyl acetate at 80° C. for 10 hours. After completion of the reaction, the obtained solution was cooled, and 25 parts by mass of xylene, 5 parts by mass of acrylic acid, and 0.5 parts by mass of tetradecyldimethylbenzylammonium chloride were added to the cooled solution, and the reaction was carried out at 85° C. for 32 hours while blowing in air. In this manner, a (meth)acrylic resin solution 1 was obtained.

(Meth)acrylic resin emulsion 1:
Using 0.5 parts by mass of ammonium peroxodisulfate as a polymerization initiator, 63 parts by mass of 2-ethylhexyl acrylate, 21 parts by mass of n-butyl acrylate, 9 parts by mass of methyl methacrylate, 3 parts by mass of 2-hydroxyethyl methacrylate, 2 parts by mass of methacrylic acid, 1 part by mass of acrylamide, 1 part by mass of polytetramethylene glycol diacrylate (manufactured by NOF Corporation, product name: Blemmer ADT-250), and 2 parts by mass of an aqueous solution of polyoxyethylene nonylpropenyl phenyl ether ammonium sulfate (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name: Aqualon HS-1025) were emulsion polymerized in deionized water at 70° C. for 8 hours.
After the polymerization was completed, the pH was adjusted to 7 with aqueous ammonia.
In this manner, a (meth)acrylic resin emulsion 1 having a solid content concentration of 56.5% was obtained.

(Meth)acrylic resin emulsion 2:
Using 0.5 part by mass of 4,4'-azobis-4-cyanovaleric acid (manufactured by Otsuka Chemical Co., Ltd., product name: ACVA) as a polymerization initiator, 74 parts by mass of butyl acrylate, 14 parts by mass of methyl methacrylate, 9 parts by mass of 2-hydroxyethyl methacrylate, 2 parts by mass of methacrylic acid, 1 part by mass of acrylamide, and 3 parts by mass of an aqueous solution of polyoxyethylene nonylpropenyl phenyl ether ammonium sulfate (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name: Aqualon HS-1025) were emulsion-polymerized in deionized water at 70°C for 8 hours.
After the polymerization was completed, the pH was adjusted to 7 with aqueous ammonia.
As a result, a (meth)acrylic resin emulsion 2 having a solid content concentration of 42.5% was obtained.

<Formulation of adhesive coating solution>
Adhesive coating solution B1 for forming adhesive resin layer (B):
100 parts by mass of the (meth)acrylic resin solution 1 (solid content concentration 45%) and 0.9 parts by mass of an isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name: Takenate D170N) (2 parts by mass per 100 parts by mass of adhesive resin in terms of solid content) were mixed, and 7 parts by mass of toluene and 7 parts by mass of ethyl acetate were added to prepare an adhesive coating solution B1.

Adhesive coating solution B2 for forming adhesive resin layer (B):
100 parts by mass of the (meth)acrylic resin solution 1 (solid content concentration 45%), 2.4 parts by mass of a polymerized rosin ester tackifier (manufactured by Arakawa Chemical Industries, Ltd., product name: Pencel D-125) (5.3 parts by mass per 100 parts by mass of adhesive resin in terms of solid content), 1.3 parts by mass of an isocyanate crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name: Olester P49-75S) (3.7 parts by mass per 100 parts by mass of adhesive resin in terms of solid content), and 7.1 parts by mass of thermally expandable microspheres (manufactured by Sekisui Chemical Co., Ltd., product name: Advancell EM-503) (15.8 parts by mass per 100 parts by mass of adhesive resin in terms of solid content) were mixed, and 37 parts by mass of toluene and 37 parts by mass of ethyl acetate were added to prepare an adhesive coating solution B2.

Adhesive coating solution C1 for forming irregularity-absorbing resin layer (C):
The (meth)acrylic resin solution 1, an isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name: Olester P49-75S), a thermal initiator (manufactured by Nouryon Chemical, Inc., organic peroxide, product name: Perkadox 12-XL25), an alkylphenone-based photoinitiator (manufactured by IGM Resins B.V., 2-benzyl-2-(dimethylamino)-4'-morpholinobutyrophenone, product name: Omnirad 369), and a polyfunctional acrylic oligomer (manufactured by Toagosei Co., Ltd., product name: Aronix M400) were mixed in the solid content blending ratio (parts by mass) shown in Table 1 to prepare an adhesive coating solution C1.

Adhesive coating solution C2 for forming irregularity-absorbing resin layer (C):
The (meth)acrylic resin solution 1, an isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name: OLESTAR P49-75S), a thermal initiator (manufactured by Nouryon Chemical Industries, Ltd., organic peroxide, product name: PERKADOX 12-XL25) and a polyfunctional acrylic oligomer (manufactured by Toagosei Co., Ltd., product name: ARONIX M400) were mixed in the solid content blending ratio (parts by mass) shown in Table 1 to prepare an adhesive coating solution C2.

Adhesive coating solution A for forming adhesive resin layer (A):
As shown in Table 1, 42.6 parts by mass of (meth)acrylic resin emulsion 1, 57.4 parts by mass of (meth)acrylic resin emulsion 2, 0.4 parts by mass of dimethylethanolamine, 5 parts by mass of an epoxy compound (product name: EX-1610, manufactured by Nagase ChemteX Corporation) serving as a crosslinking agent, 13 parts by mass of diethylene glycol monobutyl ether, and 20 parts by mass of H ₂ O were mixed to prepare a pressure-sensitive adhesive coating solution A.

<Preparation of adhesive film>
[Example 1]
First, the adhesive coating solution B1 was applied onto a separator that had been subjected to a silicone release treatment, and a resin film was formed by drying for 3 minutes at 120° C. This resin film was then attached to the second surface of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name: Lumirror S10, thickness: 38 μm, double-sided corona treated product) that was a base layer, to form an acrylic resin layer.
Similarly, the adhesive coating solution B2 was applied onto the separator and dried at 120° C. for 3 minutes to form a resin film. Then, this resin film was laminated onto the acrylic resin layer. Thus, a two-layer adhesive resin layer (B) was obtained.
Thereafter, the adhesive coating solution C1 was similarly applied onto the separator and dried at 100° C. for 3 minutes to form a resin film. This resin film was attached to the first surface of the substrate layer (the surface of the substrate layer opposite to the surface on which the adhesive resin layer (B) was provided). This resulted in a crosslinked irregularity-absorbing resin layer (C).
Further, the adhesive coating solution A was applied onto the separator and dried at 120° C. for 3 minutes to obtain a resin film. This resin film was laminated onto the crosslinked irregularity-absorbing resin layer (C) to obtain an adhesive resin layer (A).
As a result of the above, an adhesive film was obtained comprising a base layer, an adhesive resin layer (A) provided on the first surface side of the base layer, an adhesive resin layer (B) provided on the second surface side of the base layer, and an unevenness-absorbing resin layer (C) provided between the base layer and the adhesive resin layer (A).
The resulting adhesive film was heated at 60° C. for 5 days.

[Comparative Example 1]
An adhesive film was obtained in the same manner as in Example 1, except that the adhesive coating liquid C2 was used instead of the adhesive coating liquid C1 for forming the irregularity-absorbing resin layer (C).
(The material for forming the adhesive resin layer (B) and the method for providing the adhesive resin layer (B) are the same in Example 1 and Comparative Example 1.)
Incidentally, Comparative Example 1 differs from Example 1 in that the irregularity-absorbing resin layer does not contain an alkylphenone-based photoinitiator (Omnirad 369) and is not crosslinkable by light energy.

<Evaluation>
(1) Measurement of storage modulus E' of unevenness-absorbing resin layer (C) at 125 ° C. Using the adhesive coating liquid C1 and C2 for forming the unevenness-absorbing resin layer (C) used in the examples and comparative examples, an unevenness-absorbing resin layer (C) having a thickness of 40 μm was prepared separately from the adhesive film. Then, the obtained unevenness-absorbing resin layer (C) was laminated to obtain unevenness-absorbing resin layer samples C1S and C2S having a thickness of 1 mm.
The obtained roughness-absorbing resin layer samples C1S and C2S were irradiated with UV having a wavelength of 300 to 600 nm using a UV irradiator (Ushio Inc., product name: UVX-02528S1AJA02) under the condition of 1080 mJ/ ^cm2 . The structure was then heated under the condition of 130°C and 30 minutes. As a result, the roughness-absorbing resin layer (C) was crosslinked (cured), and samples C1S' and C2S' for measuring viscoelasticity of the roughness-absorbing resin layer (C') were obtained, respectively.
The solid viscoelasticity of the obtained viscoelasticity measurement samples C1S' and C2S' was measured using a solid viscoelasticity measurement device (RSA-3, manufactured by TA Instruments) under the conditions of a frequency of 1 Hz, a temperature rise rate of 5°C/min, a strain fixed mode of 0.05%, a chuck distance of 20 mm, and a sample width of 10 mm, and the measurement results were analyzed. The storage modulus E' at 125°C of the unevenness-absorbing resin layer (C) was determined.

(2) Evaluation of Wrinkles First, the adhesive resin layer (B) side of the adhesive film obtained in the Examples and Comparative Examples was adhered to a stainless steel plate (φ320 mm, thickness 2.0 mm) for compression molding.
Next, 1574 silicon mirror chips of 4.7 mm x 3.9 mm and 55 patterned silicon chips of 3.5 mm x 3.5 mm were placed as electronic components on the adhesive resin layer (A) of the adhesive film and adhered to each other to obtain a structure.
The obtained structure was irradiated with UV having a wavelength of 300 to 600 nm using a UV irradiator (Ushio Inc., product name: UVX-02528S1AJA02) under the condition of 1080 mJ/ ^cm2 . At this time, the UV was irradiated from the side where the silicon chip was attached. The structure was then heated under the conditions of 130°C and 30 minutes. This caused the unevenness-absorbing resin layer (C) to crosslink (cure).

Next, the silicon chip on the adhesive resin layer (A) was encapsulated by compression molding (125° C., 400 seconds) using a liquid epoxy resin-based encapsulant (manufactured by Nagase Chemtex Corporation, product name: R4212-2C) using a compression molding machine. This resulted in a structure in which an encapsulating resin wafer (φ300 mm, thickness 550 μm) was formed on a stainless steel plate.
The resulting structure was subjected to a post-mold cure at 150° C. for 30 minutes.
Thereafter, the adhesive film was peeled off from the stainless steel plate by heating at 190° C. for 60 seconds, and the adhesive film was then peeled off from the sealing resin wafer.
The surface unevenness of the obtained sealing resin wafer was observed using a shape analysis laser microscope (manufactured by KEYENCE Corporation, product name: VK-X1000), and wrinkles were evaluated according to the following criteria.
◯ (Good): No irregularities with a height difference between the concaves and convexities of 5 μm or more are repeatedly generated. × (Bad): Irregularities with a height difference between the concaves and convexities of 5 μm or more are repeatedly generated.

(3) Evaluation of stand-off of electronic components in sealing process First, the adhesive resin layer (B) side of the adhesive film obtained in the Examples and Comparative Examples was adhered to a stainless steel plate (φ320 mm, thickness 2.0 mm) for compression molding.
Next, 1574 silicon mirror chips of 4.7 mm x 3.9 mm and 55 patterned silicon chips of 3.5 mm x 3.5 mm were placed as electronic components on the adhesive resin layer (A) of the adhesive film and adhered to each other to obtain a structure.
The obtained structure was irradiated with UV having a wavelength of 300 to 600 nm using a UV irradiator (Ushio Inc., product name: UVX-02528S1AJA02) under the condition of 1080 mJ/ ^cm2 . At this time, the UV was irradiated from the side where the silicon chip was attached. The structure was then heated under the conditions of 130°C and 30 minutes. This caused the unevenness-absorbing resin layer (C) to crosslink (cure).

Next, the silicon chip on the adhesive resin layer (A) was encapsulated by compression molding (125° C., 400 seconds) using a liquid epoxy resin-based encapsulant (manufactured by Nagase Chemtex Corporation, product name: R4212-2C) using a compression molding machine. This resulted in a structure in which an encapsulating resin wafer (φ300 mm, thickness 550 μm) was formed on a stainless steel plate.
The resulting structure was subjected to a post-mold cure at 150° C. for 30 minutes.
Thereafter, the adhesive film was peeled off from the stainless steel plate by heating at 190° C. for 60 seconds, and the adhesive film was then peeled off from the sealing resin wafer.
For the obtained encapsulating resin wafer, the height of the surface of the encapsulant was used as a reference, and the difference between the height of the surface of the silicon chip that was not bonded to the adhesive resin layer (A) and the height of the surface of the encapsulant was measured with a laser microscope (manufactured by KEYENCE, product name: VK-X1000) to determine the standoff. The standoff of the electronic component was evaluated based on the average value of the standoffs of five chips according to the following criteria.
○ (Good): Standoff is less than 10 μm × (Poor): Standoff is 10 μm or more

As can be seen from Table 1, the unevenness-absorbing resin layer (C) can be crosslinked by light energy and thermal energy, which can suppress the occurrence of standoffs, a sealing defect in electronic components, and wrinkles.

A Adhesive resin layer B Adhesive resin layer C Irregularity-absorbing resin layer C' Irregularity-absorbing resin layer 10 Base layer 10A First surface 10B Second surface 50 Adhesive film 50A Adhesive film 60 Sealing material 60A Sealing material 70 Electronic component 70A Electronic component 75 Irregularity structure 75A Irregularity structure 80 Support substrate 80A Support substrate 90 Standoff 100 Structure 200 Electronic device 300 Electronic device 310 Wiring layer 320 Bump 400 Electronic device

Claims (11)

The adhesive sheet comprises a base layer, an adhesive resin layer (A) provided on a first surface side of the base layer for temporarily fixing an electronic component, an adhesive resin layer (B) provided on a second surface side of the base layer, and an unevenness-absorbing resin layer (C) provided between the base layer and the adhesive resin layer (A) or between the base layer and the adhesive resin layer (B) and capable of being crosslinked by light energy and thermal energy ,
The unevenness-absorbing resin layer (C) contains a resin, a crosslinking agent, a photoinitiator, and a thermal initiator,
An adhesive film , wherein the photoinitiator comprises an alkylphenone-based photoinitiator . The adhesive film according to claim 1 ,
The adhesive film, wherein the adhesive resin layer (B) is a layer whose adhesive strength decreases in response to an external stimulus. The adhesive film according to claim 1 or 2, wherein the thermal initiator comprises one or more selected from aromatic ketones, onium salt compounds, organic peroxides, thio compounds, hexaarylbiimidazole compounds, ketoxime ester compounds, borate compounds, azinium compounds, metallocene compounds, active ester compounds, compounds having a carbon-halogen bond, and azo compounds. The pressure-sensitive adhesive film according to claim 1 , wherein the crosslinking agent comprises one or more compounds selected from the group consisting of polyfunctional (meth)acrylate compounds and isocyanate compounds. The pressure-sensitive adhesive film according to any one of claims 1 to 4 ,
An adhesive film, wherein the unevenness-absorbing resin layer (C) is provided at least between the base layer and the adhesive resin layer (A). The pressure-sensitive adhesive film according to any one of claims 1 to 5 ,
The adhesive film further comprises an unevenness-absorbing resin layer (C') obtained by crosslinking the unevenness-absorbing resin layer (C), the unevenness-absorbing resin layer (C') having a storage modulus E' at 125° C. of 1.0×10 ⁶ Pa or more and 1.0×10 ⁹ Pa or less. The pressure-sensitive adhesive film according to any one of claims 1 to 6 ,
The thickness of the unevenness-absorbing resin layer (C) of the pressure-sensitive adhesive film is 5 μm or more and 1000 μm or less. The pressure-sensitive adhesive film according to any one of claims 1 to 7 ,
An adhesive film, wherein the adhesive resin constituting the adhesive resin layer (A) includes one or more selected from a (meth)acrylic adhesive resin, a silicone adhesive resin, a urethane adhesive resin, an olefin adhesive resin, and a styrene adhesive resin. The pressure-sensitive adhesive film according to any one of claims 1 to 8 ,
An adhesive film used for temporarily fixing an electronic component when the electronic component is sealed with a sealing material. The adhesive film according to claim 9 ,
The electronic component is an adhesive film having a concave-convex structure. The adhesive film according to claim 10 ,
The uneven structure of the electronic component is an adhesive film including a bump electrode.