JP7799384B2 - adhesive film - Google Patents

Description

The present invention relates to an adhesive film.

BACKGROUND ART As a technique that can reduce the size and weight of electronic devices (for example, semiconductor devices), a method for manufacturing an electronic device using an adhesive film is known.
An example of an application of the adhesive film in the manufacture of electronic devices is its application to a 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 manufacturing method of 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 devices 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 after lamination of 0.5 N/20 mm or more, and hardening due to stimuli received up to the point at which the resin-encapsulating process is completed, so that the peel strength to the package is 2.0 N/20 mm or less.

Patent Document 2 describes an adhesive film used to temporarily fix electronic components when sealing the electronic components with a sealing material in the manufacturing process of an electronic device. This adhesive film includes an adhesive resin layer (A) for temporarily fixing the electronic components, an adhesive resin layer (B) used to attach the electronic components to a support substrate and whose adhesive strength decreases in response 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.

Furthermore, Patent Document 3 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 the following steps: (1) preparing a structure including an adhesive film having a base layer, an adhesive resin layer provided on a first surface of the base layer for temporarily fixing an electronic component, and an adhesive resin layer (B) provided on a second surface of the base layer, the adhesive strength of which decreases in response to 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 the group consisting of 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 encapsulating the electronic component with an encapsulant.

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: an adhesive film including a base layer; an adhesive resin layer (A) provided on a first surface of the base layer for temporarily fixing an electronic component; an adhesive resin layer (B) provided on a second surface of the base layer and whose adhesive strength decreases in response to 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 an encapsulation step of encapsulating the electronic component with an encapsulant.

JP 2011-134811 A Japanese Patent Application Laid-Open No. 2018-157037 International Publication No. 2019/188543 International Publication No. 2020/184201

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

In order to improve the above issues, it is believed that using an adhesive film with an irregularity-absorbing resin layer, as described in Patent Document 4, for example, is effective. By using an adhesive film with an irregularity-absorbing resin layer, it is possible to prevent misalignment of electronic components during the sealing process and the infiltration of sealing material between the adhesive film and the electronic components.

However, as shown in Figures 4(a) to (c), when an adhesive film 50A having an irregularity-absorbing resin layer is used, when an electronic component 70A having an irregularity structure 75A is placed and sealed with a sealing material 60A, the irregularity-absorbing resin layer softens due to heat, and the pressure of the sealing material 60A makes it easier for the electronic component 70A to sink into the adhesive film 50A. As a result, it has been revealed that a defective sealing of the electronic component 70A (where part of the side of the electronic component 70A is not sealed), known as a standoff 90, can occur, as shown in Figure 4(d).

The present invention was made in consideration of the above circumstances. One of the objects of the present invention is to provide an adhesive film that can suppress the occurrence of standoffs, a sealing defect in electronic components.

The inventors conducted extensive research to achieve the above-mentioned objectives. As a result, they discovered that the occurrence of standoff, a sealing defect in electronic components, can be suppressed by using an adhesive film equipped with an unevenness-absorbing resin layer that can be crosslinked by an external stimulus, 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 and for temporarily fixing electronic components; 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 crosslinking in response to an external stimulus.
[2]
In the pressure-sensitive adhesive film according to the above [1],
The adhesive film is one in which 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 [1] or [2],
The adhesive film wherein the external stimulus is heat or light.
[4]
In the pressure-sensitive adhesive film according to any one of the above [1] to [3],
An adhesive film, wherein the unevenness-absorbing resin layer (C) is provided at least between the substrate layer and the adhesive resin layer (A).
[5]
In the pressure-sensitive adhesive film according to any one of the above [1] to [4],
The pressure-sensitive adhesive film has a storage modulus E' at 125° C. of 5.0×10 ⁵ Pa or more and 1.0×10 ⁹ Pa or less of the unevenness-absorbing resin layer (C') obtained by crosslinking the unevenness-absorbing resin layer (C).
[6]
In the pressure-sensitive adhesive film according to any one of the above [1] to [5],
The adhesive film, wherein the irregularity-absorbing resin layer contains a resin, a crosslinking agent, and an initiator that generates active chemical species in response to an external stimulus.
[7]
In the pressure-sensitive adhesive film according to any one of the above [1] to [6],
The thickness of the unevenness-absorbing resin layer of the pressure-sensitive adhesive film is 10 μm or more and 1000 μm or less.
[8]
In the pressure-sensitive adhesive film according to any one of the above [1] to [7],
An adhesive film in which the adhesive resin constituting the adhesive resin layer (A) contains one or more selected from (meth)acrylic adhesive resins, silicone adhesive resins, urethane adhesive resins, olefin adhesive resins, and styrene adhesive resins.
[9]
In the pressure-sensitive adhesive film according to any one of the above [1] to [8],
An adhesive film used to temporarily fix an electronic component when the electronic component is sealed with a sealing material.
[10]
In the pressure-sensitive adhesive film according to the above [9],
The adhesive film has an uneven structure on the electronic component.
[11]
In the pressure-sensitive adhesive film according to the above [10],
The uneven structure of the electronic component is an adhesive film including bump electrodes.

The present invention provides an adhesive film that can prevent standoffs, a sealing defect in electronic components.

1 is a cross-sectional view schematically illustrating an example of the structure of an adhesive film according to an embodiment of the present invention. 1A to 1C are cross-sectional views schematically 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 schematically illustrating an example of a method for manufacturing an electronic device according to an embodiment of the present invention. 1A and 1B are diagrams for explaining a seal 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 where appropriate. Also, the drawings are schematic diagrams and do not necessarily correspond to the actual dimensional ratios.
In the specification, unless otherwise specified, the expression "A to B" regarding a numerical range means A or more and B or less. For example, 1 to 5% means 1% or more and 5% or less.
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 be described below.
FIG. 1 is a cross-sectional view schematically showing an 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 includes 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) 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 crosslinking in response to an external stimulus.
From the viewpoint of further improving the unevenness absorbency of the pressure-sensitive adhesive film 50, the irregularity-absorbing resin layer (C) is preferably located at least between the substrate layer 10 and the pressure-sensitive adhesive resin layer (A).
When the irregularity-absorbing resin layer (C) is located between the base layer 10 and the adhesive resin layer (A), another irregularity-absorbing resin layer (C2) may be located between the adhesive resin layer (B) and the base layer 10. In this case, the irregularity-absorbing resin layer (C) and the irregularity-absorbing resin layer (C2) may be the same or different in terms of material, thickness, etc.

As described above, according to the investigations of the present inventors, 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 prevent the displacement of electronic components during the sealing process and the intrusion 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 irregularity-absorbing resin layer is used, when an electronic component 70A having an irregularity structure 75A is placed and sealed with a sealing material 60A, the irregularity-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 sealing material 60A. As a result, a sealing failure of the electronic component 70A, known as a standoff 90, may occur, as shown in Figure 4(d).

The inventors conducted extensive research to develop an adhesive film that can prevent displacement of electronic components and intrusion of sealing material between the adhesive film and electronic components during the sealing process, while also preventing the occurrence of standoffs during the sealing process. As a result, they discovered 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 of the base layer 10 and for temporarily fixing electronic components, an adhesive resin layer (B) provided on the second surface 10B of the base layer 10, and an irregularity-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 is crosslinkable in response to an external stimulus, can prevent displacement of electronic components and intrusion of sealing material between the adhesive film and electronic components during the sealing process, and can also prevent the occurrence of standoffs 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 in response to an external stimulus as an adhesive film for temporarily fixing an electronic component having an uneven structure, the adhesive film 50 has improved adhesion to the electronic component having an uneven structure. Therefore, during the process of sealing the electronic component, it is possible to prevent the electronic component from being displaced due to pressure caused by the flow of the sealing material, or the sealing material from penetrating between the adhesive film and the electronic component. Furthermore, after temporarily fixing the electronic component having an uneven structure, the unevenness-absorbing resin layer (C) is crosslinked and hardened in response to an external stimulus to increase the elastic modulus, thereby preventing the electronic component from sinking into the adhesive film during the process of sealing the electronic component. That is, by designing the unevenness-absorbing resin layer (C) so that it crosslinks in response to an external stimulus and changes its elastic modulus, (i) before the external stimulus is applied, the unevenness-absorbing resin layer (C) can sufficiently deform to match the uneven structure of the electronic component, and (ii) on the other hand, after the external stimulus is applied, movement of the electronic component is prevented.

As described above, the adhesive film 50 according to this embodiment can prevent misalignment of electronic components during the sealing process and the infiltration of sealing material between the adhesive film and electronic components, as well as prevent standoffs from occurring during the sealing process.

From the viewpoint of balancing 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 during the manufacturing process of electronic devices.

Next, we will explain each layer that makes up 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 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 resins constituting the resin film include known thermoplastic resins, such as one or more selected from 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.
Furthermore, the form of the resin film used to form the base layer 10 may be a stretched film or a film stretched uniaxially or biaxially, but from the viewpoint of improving the mechanical strength of the base layer 10, a film stretched uniaxially or biaxially is preferred.

From the viewpoint of obtaining good film properties, the thickness of the substrate 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 even more preferably 10 μm or more and 250 μm or less.
The substrate layer 10 may be subjected to a surface treatment 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 of the base layer 10. The adhesive resin layer (A) is a layer that comes into contact with the surface of an electronic component to temporarily fix the electronic component when the electronic component is sealed with a sealing material in the manufacturing process of an electronic device, for example.

The adhesive resin layer (A) usually contains an adhesive resin (A1).
Examples of the adhesive resin (A1) include (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-crosslinkable adhesive resin layer whose adhesive strength can be reduced by radiation. When the radiation-crosslinkable adhesive resin layer is irradiated with radiation, crosslinking occurs, significantly reducing the adhesive strength, 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) that forms the (meth)acrylic acid alkyl ester monomer unit (a1) include (meth)acrylic acid alkyl esters having an alkyl group of about 1 to 12 carbon atoms. Preferably, they are (meth)acrylic acid alkyl esters having an alkyl group of 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 total of all monomer units in the (meth)acrylic adhesive resin (a) is 100% by mass.

Examples of the monomer (a2) that forms the monomer (a2) having a functional group reactive 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, tert-butylaminoethyl acrylate, and tert-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% 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 (a) is 100% by 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 when emulsion polymerization is carried out.

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 or acrylates having both terminals. or dimethacrylates whose main chain structure is propylene glycol type (for example, NOF Corporation, trade names: PDP-200, PDP-400, ADP-200, ADP-400), tetramethylene glycol type (for example, NOF Corporation, trade names: ADT-250, ADT-850), or a mixture of these (for example, NOF Corporation, trade 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 0.1% by mass or more and 30% by mass or less, more preferably 0.1% by mass or more and 15% by mass or less, even more preferably 0.1% by mass or more and 20% by mass or less, and particularly preferably 0.1% by mass or more and 5% by mass or less, when the total 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: Latemul 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 0.1% by mass or more and 30% by mass or less, more preferably 0.1% by mass or more and 15% by mass or less, even more preferably 0.1% by mass or more and 20% by mass or less, and particularly preferably 0.1% by mass or more and 5% by mass or less, when the sum of all monomer units in the (meth)acrylic adhesive resin (a) is 100% by mass.

The (meth)acrylic adhesive resin (a) according to this embodiment may further contain, as necessary, a monomer unit 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 influence of functional groups of the monomers, the influence of ions on the surface of electronic components, etc., polymerization by radical polymerization is preferred.
When polymerizing by radical polymerization reaction, the radical polymerization initiator may be 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-butylperoxy-2-hexanoate, t-butyl peroxy Examples of the peroxide include organic peroxides such as 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, preferred are inorganic peroxides such as water-soluble ammonium persulfate, potassium persulfate, and sodium persulfate, and azo compounds with a carboxyl group in the molecule, such as water-soluble 4,4'-azobis-4-cyanovaleric acid. Considering the effect of ions on the surface of electronic components, azo compounds with a carboxyl group in the molecule, such as ammonium persulfate and 4,4'-azobis-4-cyanovaleric acid, are more preferred, with azo compounds with a carboxyl group in the molecule, such as 4,4'-azobis-4-cyanovaleric acid, being 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 resorcinol 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 compounds such as tetramethylolmethane-tri-β-aziridinylpropionate, 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 compounds such as N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane; and melamine 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 such that 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, if necessary, an excess amount of the crosslinking agent (A2) may be contained in cases where new functional groups are generated by the crosslinking reaction or where the crosslinking reaction is slow.
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 other components such as additives such as plasticizers and tackifying resins. When the adhesive resin layer (A) is a radiation-crosslinkable 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 further reduces adhesive residue on the electronic component when the adhesive film is peeled 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 preferably, for example, 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 material layer 10 or the irregularity-absorbing resin layer (C). The adhesive may be dissolved in a solvent and applied as a coating liquid, or may be applied as an aqueous emulsion, or the liquid adhesive may be directly applied.
Among these, an aqueous emulsion coating liquid is preferred. Examples of the aqueous emulsion coating liquid include a coating liquid obtained by dispersing 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 in water.
A pressure-sensitive adhesive coating solution dissolved in an organic solvent may also be used. The organic solvent is not particularly limited and may be appropriately selected from known solvents taking into account 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 solution can be applied using conventional coating methods such as roll coating, reverse roll coating, gravure roll coating, bar coating, comma coating, and die coating. There are no particular restrictions on the drying conditions for the applied adhesive, but it is generally preferable to dry it for 10 seconds to 10 minutes at a temperature range of 80 to 200°C. It is even more preferable to dry it for 15 seconds to 5 minutes at a temperature range of 80 to 170°C. To fully promote the crosslinking reaction between the crosslinker and adhesive, the adhesive coating solution may be heated at 40 to 80°C for approximately 5 to 300 hours after drying is complete.

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

<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 material 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 support substrate by applying an external stimulus.
Here, examples of the adhesive resin layer (B) whose adhesive strength decreases with an external stimulus include a heat-peelable adhesive resin layer whose adhesive strength decreases with heating, a light-peelable adhesive resin layer whose adhesive strength decreases with light such as radiation, etc. Among these, a heat-peelable adhesive resin layer whose adhesive strength decreases with heating is preferred.
Examples of heat-peelable adhesive resin layers include adhesive resin layers made of a heat-expandable adhesive containing a gas-generating component, or a heat-expandable adhesive containing heat-expandable microspheres that can expand to reduce adhesive strength.

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

Gas-generating components used in thermally expandable adhesives include, for example, azo compounds, azide compounds, and Meldrum's acid derivatives. Other examples include inorganic blowing 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(benzenesulfonyl)hydrazide; Other examples of organic blowing agents that can be used include hydrazine compounds such as p-toluenesulfonylsemicarbazide and 4,4'-oxybis(benzenesulfonylsemicarbazide); semicarbazide compounds such as p-toluenesulfonylsemicarbazide and 4,4'-oxybis(benzenesulfonylsemicarbazide); triazole compounds such as 5-morpholyl-1,2,3,4-thiatriazole; and N-nitroso compounds such as N,N'-dinitrosopentamethylenetetramine and N,N'-dimethyl-N,N'-dinitrosoterephthalamide. The gas-generating component may be added to the adhesive resin (B1) or may be directly bonded to the adhesive resin (B1).

The heat-expandable microspheres used in heat-expandable pressure-sensitive adhesives can be, for example, microencapsulated blowing agents. Examples of such heat-expandable microspheres include microspheres in which a substance that easily gasifies and expands upon heating, such as isobutane, propane, or pentane, is encapsulated within 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. Heat-expandable microspheres can be produced, for example, by coacervation or interfacial polymerization.
Heat-expandable microspheres can be added to adhesive resins.

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 thermally expand to be higher than 150°C or higher than 170°C.

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

Examples of the (meth)acrylic adhesive resin (b) used in the adhesive resin layer (B) include copolymers containing (meth)acrylic acid alkyl ester monomer units (b1) and monomer units (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) that forms the (meth)acrylic acid alkyl ester monomer unit (b1) include (meth)acrylic acid alkyl esters having an alkyl group of about 1 to 12 carbon atoms. Preferably, they are (meth)acrylic acid alkyl esters having an alkyl group of 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 (b) according to the present embodiment, the content of the (meth)acrylic acid alkyl ester monomer unit (b1) 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 total of all monomer units in the (meth)acrylic adhesive resin (b) is 100% by mass.

Examples of the monomer (b2) that forms the monomer (b2) having a functional group reactive 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, tert-butylaminoethyl acrylate, and tert-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 (b) according to the present 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 when emulsion polymerization is carried out.

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 or acrylates having both ends or dimethacrylates whose main chain structure is propylene glycol type (for example, NOF Corporation's trade names: PDP-200, PDP-400, ADP-200, ADP-400), tetramethylene glycol type (for example, NOF Corporation's trade names: ADT-250, ADT-850), or a mixture of these (for example, NOF Corporation's trade 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 0.1% by mass or more and 30% by mass or less, more preferably 0.1% by mass or more and 15% by mass or less, even more preferably 0.1% by mass or more and 20% by mass or less, and particularly preferably 0.1% by mass or more and 5% by mass or less, when the total 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: Latemul 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% by mass or more and 30% by mass or less, more preferably 0.1% by mass or more and 20% by mass or less, even more preferably 0.1% by mass or more and 15% by mass or less, and particularly preferably 0.1% by mass or more and 5% by mass or less, when the sum 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, if necessary, a monomer unit 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. Taking into consideration the production cost of the (meth)acrylic adhesive resin (b), the influence of functional groups of the monomer, the influence of ions on the surface of electronic components, etc., polymerization by radical polymerization is preferred.
When polymerizing by radical polymerization reaction, the radical polymerization initiator may be 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-butylperoxy-2-hexanoate, t-butyl peroxy Examples of the peroxide include organic peroxides such as 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, preferred are inorganic peroxides such as water-soluble ammonium persulfate, potassium persulfate, and sodium persulfate, and azo compounds with a carboxyl group in the molecule, such as water-soluble 4,4'-azobis-4-cyanovaleric acid. Considering the effect of ions on the surface of electronic components, azo compounds with a carboxyl group in the molecule, such as ammonium persulfate and 4,4'-azobis-4-cyanovaleric acid, are more preferred, with azo compounds with a carboxyl group in the molecule, such as 4,4'-azobis-4-cyanovaleric acid, being 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 react with the functional groups of the adhesive resin (B1) to adjust the adhesive strength and cohesive strength.
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 resorcinol 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 compounds such as tetramethylolmethane-tri-β-aziridinylpropionate, 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 compounds such as N,N,N',N'-tetraglycidyl-m-xylylenediamine and 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane; and melamine 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, if necessary, an excess amount of the crosslinking agent (B2) may be contained in cases where new functional groups are generated by the crosslinking reaction or where the crosslinking reaction is slow.
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).

From the viewpoint of improving 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). Incorporating a tackifier resin into the adhesive resin layer (B) is preferred because it facilitates adjustment of adhesion to the support substrate at around room temperature. Tackifier resins preferably have a softening point of 100°C or higher. Specific examples of tackifier resins include rosin-based resins such as rosin derivatives that have been treated with esterification or the like; terpene-based resins such as α-pinene, β-pinene, dipentene, and terpene phenol; natural rosins such as gum-based, wood-based, and tall oil-based rosins; hydrogenated, disproportionated, polymerized, or maleated natural rosins; petroleum resins; and coumarone-indene resins.

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 within this range not only reduces contamination and adhesive residue on the support substrate, but also enables improved adhesion to the support substrate in working environments. Furthermore, using a polymerized rosin ester-based tackifier resin not only reduces contamination and adhesive residue on the support substrate, but also improves adhesion to the support substrate in environments of 80 to 130°C, and in the case of a heat-expandable adhesive containing heat-expandable microspheres, it enables easier peeling from the support substrate after the heat-expandable microspheres expand.

The blending ratio of the tackifier resin is not particularly limited, and may be selected as appropriate so as to adjust the elastic modulus of the adhesive resin layer (B) within the desired range. However, in terms of the elastic modulus and initial peel strength of the adhesive resin layer (B), a blending ratio of 1 to 100 parts by mass per 100 parts by mass of adhesive resin (B1) is preferred. When the blending ratio of the tackifier resin is equal to or greater than the lower limit above per 100 parts by mass of adhesive resin (B1), adhesion to the support substrate during operation tends to be improved. On the other hand, when the blending ratio is equal to or less than the upper limit above, attachment to the support substrate at room temperature tends to be improved. In terms of adhesion to the support substrate and attachment at room temperature, a blending ratio of 2 to 50 parts by mass of the tackifier resin per 100 parts by mass of adhesive resin (B1) is even more preferred. Furthermore, 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 above, adhesive residue on the support substrate tends to be less likely to be left 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 multiple layers. For example, by laminating two or more layers that expand by heating to form the adhesive resin layer (B), it is possible to change the adhesiveness/thermal releasability 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 5 μm to 300 μm, and more preferably from 20 μm to 150 μm.

The adhesive resin layer (B) can be formed, for example, by applying an adhesive coating liquid onto the substrate layer 10, or by transferring the adhesive resin layer (B) formed on a separator onto the substrate 10.
The adhesive coating liquid can be applied by conventionally known coating methods, such as a roll coater method, a reverse roll coater method, a gravure roll method, a bar coater method, a comma coater method, or a die coater method. There are no particular restrictions on the drying conditions for the applied adhesive, but it is generally preferable to dry it for 10 seconds to 10 minutes at a temperature range of 80 to 200°C. It is more preferable to dry it for 15 seconds to 5 minutes at 80 to 170°C. 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 material layer 10 and the adhesive resin layer (B) may be formed by co-extrusion molding, or may be formed by laminating a film-like base material layer 10 and a film-like adhesive resin layer (B).

<Irregularity-absorbing resin layer (C)>
The adhesive film 50 according to this embodiment has an unevenness-absorbing resin layer (C) that can be crosslinked by an external stimulus between the base layer 10 and the adhesive resin layer (A) or between the base layer 10 and the adhesive resin layer (B).
The irregularity-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 irregular structure is formed, and improving the adhesion between the electronic component having the irregular structure and the adhesive film 50. Furthermore, the irregularity-absorbing resin layer (C) can be crosslinked and cured by an external stimulus, thereby increasing the elastic modulus of the irregularity-absorbing resin layer (C). This makes it possible to prevent the electronic component from sinking into the adhesive film during the sealing process of the electronic component.
The external stimulus may be, for example, heat or light.

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

The irregularity-absorbing resin layer (C) preferably contains a resin, a crosslinking agent, and an initiator that generates active chemical species in response to an external stimulus. By including these components in the irregularity-absorbing resin layer (C), the irregularity-absorbing resin layer (C) can be more effectively crosslinked in response to an external stimulus, and the elastic modulus of the irregularity-absorbing resin layer (C) can be further improved. This prevents the irregularity-absorbing resin layer from softening due to heat during the process of sealing the electronic components with a sealing material, and as a result, it is possible to further prevent 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 irregularity-absorbing resin layer (C) may be crosslinked (cured) by an external stimulus even if it does not necessarily contain an initiator.

The resin that can be used to form the irregularity-absorbing resin layer (C) is not particularly limited, but preferred examples include the resins described as the adhesive resin (B1) in the adhesive resin layer (B) described above.
Other resins that can be used to form the roughness-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 copolymers, 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 Ethylene-ethylenically unsaturated acid copolymers such as ethylene-crotonic acid copolymer; ethylene-vinyl ester copolymers such as ethylene-vinyl acetate copolymer, ethylene-vinyl propionate copolymer, ethylene-vinyl butyrate copolymer, and ethylene-vinyl stearate copolymer; ethylene-styrene copolymers, etc.; unsaturated carboxylic acid ester (co)polymers such as (meth)acrylic acid ester (co)polymers; ionomer resins such as ethylene-metal acrylate copolymer and ethylene-metal methacrylate copolymer; 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 group consisting of polyolefin resins; 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; and polylactic acid can be used.
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 roughness-absorbing resin layer (C) is not particularly limited, and may be any agent that undergoes a crosslinking reaction with a chemical species generated from an initiator.
Preferred crosslinking agents include polyfunctional (meth)acrylate 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, and 1,4-butanediol di(meth)acrylate.
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, 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 irregularity-absorbing resin layer (C) may contain one or more crosslinking agents (A2) that can be contained in the aforementioned adhesive resin layer (A). Specifically, the irregularity-absorbing resin layer (C) may contain an isocyanate-based compound. When such a crosslinking agent is used, the amount thereof is, for example, 0.01 to 5 parts by weight, preferably 0.01 to 3 parts by weight, per 100 parts by weight of the resin (base polymer).

The initiator (an initiator that generates active chemical species upon external stimulation) that can be contained in the roughness-absorbing resin layer (C) is not particularly limited as long as it can crosslink the resin and/or crosslinking agent in the roughness-absorbing resin layer (C) by heat or light. Considering that the light transmittance of other layers may not be high and that light may be blocked by electronic components, the initiator is preferably an initiator that generates active chemical species upon heat.
The chemical species generated from the 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 the initiator 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, azo compounds, etc. These may be used alone or in combination of two or more.
Among these, azo compounds or organic peroxides are preferred in terms of availability, ease of handling, etc., and organic peroxides are more preferred.

Commercially available initiators include V-70, V-65, V-601, V-59, V-40, VF-096, V-30, VAm-110, and VAm-111 (all manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), Niper BW, Niper BMT, Perloyl TCP, Perloyl L, Perloyl 355, Perloyl SA, Perhexa HC, Perbutyl 355, Perbutyl D, Perbutyl L, Perbutyl ND, Perocta O, Perhexyl D, Perhexyl O, and Perhexyl PV (all manufactured by NOF Corp.), Trigonox 36-C75, Laurox, Perkadox L-W75, Perkadox CH-50L, Trigonox TMBH, Kayacumen H, Kayabutyl H-70, Perkadox BC-FF, and Kayahexa Examples include 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, Kayacarbon EH, Kayacarbon I-20, Kayacarbon BIC-75, Trigonox 117, and Kayalene 6-70 (all manufactured by Kayaku Akzo Co., Ltd.).

When the irregularity-absorbing resin layer (C) contains an initiator, the amount thereof 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. Furthermore, from the viewpoint of storage stability, the amount is preferably 15 parts by mass or less, more preferably 5 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, more preferably 5.0 x 103 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' at 60°C of the unevenness-absorbing resin layer (C) before crosslinking is preferably 1.0 x 10 ⁶ Pa or less, and more preferably 5.0 x 10 ⁵ Pa or less, in order to effectively absorb the unevenness on the chip surface and to prevent deterioration of unevenness absorption over time due to springback of the resin.
The storage modulus E' at 60°C of the uneven absorbent resin layer (C) before crosslinking can be controlled within the above range, for example, by controlling the type and blending ratio of each component constituting the uneven absorbent 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 pressure-sensitive 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 10 ⁹ Pa or less, and more preferably 1.0 x 10 ⁸ Pa or less, in order to further suppress misalignment of electronic components during the sealing process.
The storage modulus E' of the uneven absorbent resin layer (C') at 125°C can be controlled within the above range, for example, by controlling the types and blending ratios of the components constituting the uneven absorbent resin layer (C).
Here, whether the crosslinking treatment of the uneven absorbent resin layer (C) is complete or not can be determined, for example, by determining the point at which the storage modulus E' of the uneven absorbent resin layer (C) no longer increases even after the crosslinking treatment.

The thickness of the irregularity-absorbing resin layer (C) is not particularly limited as long as it is thick enough to embed the irregularity structure of the electronic component, but for example, it is preferably 10 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, 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 above upper limit, the thickness of the pressure-sensitive adhesive film 50 can be made thinner while improving the unevenness absorbency.
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 irregularity-absorbing resin layer (C) is not particularly limited, and the same methods as those 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 or the like between the layers, 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 this embodiment will be described. Figures 2 and 3 are cross-sectional views that schematically show an example of a method for manufacturing an electronic device according to an embodiment of the present invention.
The method for manufacturing an electronic device according to this embodiment includes at least the following three steps.
(1) a preparation step of preparing a structure 100 including a substrate layer 10, an adhesive resin layer (A) provided on the first surface 10A of the substrate layer 10 and for temporarily fixing an electronic component 70, an adhesive resin layer (B) provided on the second surface 10B of the substrate layer 10, an unevenness-absorbing resin layer (C) provided between the substrate layer 10 and the adhesive resin layer (A) or between the substrate layer 10 and the adhesive resin layer (B) and capable of being crosslinked by an external stimulus, and an electronic component 70 attached to the adhesive resin layer (A) of the adhesive film 50 and having an unevenness structure 75; (2) a crosslinking step of crosslinking the unevenness-absorbing resin layer (C) in the structure 100 by applying an external stimulus to the unevenness-absorbing resin layer (C);
(3) Sealing step of sealing the electronic component 70 with the sealing material 60

The following describes each step in the manufacturing method for an electronic device 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, the structure 100 may further include 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 to 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 to the adhesive resin layer (B), and the protective film can be peeled off to attach the exposed surface of the adhesive resin layer (B) 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 placed 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 (mounting surface of a printed circuit board or the like).
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, an external stimulus is applied to the irregularity-absorbing resin layer (C) in the structure 100, thereby crosslinking the irregularity-absorbing resin layer (C).

The method for thermally crosslinking the irregularity-absorbing resin layer (C) is not limited, but thermal crosslinking is preferred. In the case of thermal crosslinking, the heating temperature is, for example, 100°C to 180°C, and the heating 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.

Furthermore, the irregularity-absorbing resin layer (C) can be crosslinked and cured by irradiating the irregularity-absorbing resin layer (C) with light such as ultraviolet light.
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 rays having a dominant wavelength of 365 nm using a high-pressure mercury lamp under conditions of an irradiation intensity of 10 to 350 mW/ ^cm2 and an ultraviolet amount ^of 100 to 20,000 mJ/cm2 in an environment of 0 to 60°C.

((3) Sealing process)
Next, the electronic component 70 is 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, or liquid.

The sealing material 60 is not particularly limited, but for example, an epoxy resin-based sealing material using an epoxy resin can be used.
In particular, a liquid epoxy resin-based sealing material is preferred because it 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.

Sealing methods include, for example, 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, thereby obtaining 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 may be further provided in which an external stimulus is applied to reduce the adhesive strength of the adhesive resin layer (B) to peel off the support substrate 80 from the structure 100.
The support substrate 80 can be easily removed from the adhesive film 50, for example, by sealing the electronic component 70 and then heating it to a temperature exceeding 150°C or a temperature exceeding 170°C to reduce 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 using conventional methods and may have a multi-layer structure.

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

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. 3(7).
The electronic device 300 can be diced by a known method.

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

The present invention is not limited to the above-described embodiments, and any modifications or improvements that achieve the objectives of the present invention are included in the present invention.

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

<Synthesis (polymerization) of adhesive raw material for forming roughness-absorbing resin layer (C) or adhesive resin layer (B)>
(Meth)acrylic resin solution 1:
41 parts by mass of ethyl acrylate, 15 parts by mass of methyl acrylate, 35 parts by mass of 2-ethylhexyl acrylate, 9 parts by mass of 2-hydroxyethyl methacrylate, and 0.8 parts by mass (solids content) of a benzoyl peroxide polymerization initiator were reacted in 10 parts by mass of toluene and 68 parts by mass of ethyl acetate at 80°C for 9 hours. After completion of the reaction, the resulting solution was cooled, and 35 parts by mass of toluene was added to the cooled solution. In this way, (meth)acrylic resin solution 1 was obtained.

(Meth)acrylic resin solution 2:
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 (solids content) of a benzoyl peroxide 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 resulting solution was cooled, and to the cooled solution were added 25 parts by mass of xylene, 5 parts by mass of acrylic acid, and 0.5 parts by mass of tetradecyldimethylbenzylammonium chloride, and the reaction was carried out at 85°C for 32 hours while blowing in air. In this way, (meth)acrylic resin solution 2 was obtained.

(Meth)acrylic resin solution 3:
77 parts by mass of n-butyl acrylate, 16 parts by mass of methyl methacrylate, 16 parts by mass of 2-hydroxyethyl acrylate, and 0.3 parts by mass of t-butylperoxy-2-ethylhexanoate as a polymerization initiator were reacted in 20 parts by mass of toluene and 80 parts by mass of ethyl acetate at 85°C for 10 hours. After completion of the reaction, the solution was cooled, and to this were added 30 parts by mass of toluene, 7 parts by mass of methacryloyloxyethyl isocyanate (manufactured by Showa Denko, product name: Karenz MOI), and 0.05 parts by mass of dibutyltin dilaurate, and the reaction was carried out at 85°C for 12 hours while blowing in air. In this way, (meth)acrylic resin solution 3 was obtained.

(Meth)acrylic resin solution 4:
72 parts by mass of n-butyl acrylate, 18 parts by mass of methyl methacrylate, 7 parts by mass of 2-hydroxyethyl methacrylate, 3 parts by mass of acrylic acid, and 0.3 parts by mass of t-butylperoxy-2-ethylhexanoate as a polymerization initiator were reacted in 36 parts by mass of toluene and 53 parts by mass of ethyl acetate at 85°C for 10 hours.
After the reaction was completed, the resulting solution was cooled, and 34 parts by mass of toluene was added to the cooled solution, thereby obtaining (meth)acrylic resin solution 4.

(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 way, a (meth)acrylic resin emulsion 1 having a solid content concentration of 56.5% was obtained.

(Meth)acrylic resin emulsion 2:
Using 0.5 parts 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.

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

Adhesive coating liquid B2 for forming adhesive resin layer (B):
100 parts by mass of (meth)acrylic resin solution 1 (solid content concentration 45%), 2.4 parts by mass of 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, converted into solid content), 1.3 parts by mass of 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, converted into solid content), and 7.1 parts by mass of heat-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, converted into solid content), were mixed, and 37 parts by mass of toluene and 37 parts by mass of ethyl acetate were added to prepare adhesive coating solution B2.

Adhesive coating solution C for forming irregularity-absorbing resin layer (C):
Any one of the (meth)acrylic resin solutions 1 to 4, an isocyanate-based crosslinking agent (manufactured by Mitsui Chemicals, Inc., product name: OLESTAR P49-75S), a thermal polymerization initiator (manufactured by Nouryon Chemical Co., Ltd., product name: PERKADOX 12-XL25), and a polyfunctional acrylic oligomer (manufactured by Shin-Nakamura Chemical Co., Ltd., product name: NK ESTER AD-TMP) were mixed in the solid content blending ratio (parts by mass) shown in Table 1 to prepare a pressure-sensitive adhesive coating solution C.

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, 3.4 or 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 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 to a separator that had been subjected to a silicone release treatment, and dried for 3 minutes at 120° C. to form a resin film. This resin film was then attached to the first surface of a polyethylene terephthalate film (manufactured by Toray Industries, Inc., product name: Lumirror S10, thickness: 38 μm, double-sided corona treated) that served as a base layer, to form an acrylic resin layer.
Similarly, the adhesive coating solution B2 was applied onto a separator and dried at 120°C for 3 minutes to form a resin film. This resin film was then laminated onto the acrylic resin layer, thereby obtaining a two-layer adhesive resin layer (B).
Thereafter, the adhesive coating solution C was similarly applied to the separator and dried at 100° C. for 3 minutes to form a resin film. This resin film was attached to the opposite side of the adhesive resin layer (B) (the surface of the substrate layer opposite to the surface on which the adhesive resin layer (B) was provided). This gave a crosslinked irregularity-absorbing resin layer (C).
Furthermore, the adhesive coating solution A was applied onto a separator and dried at 120°C for 3 minutes to form a resin film. This resin film was laminated onto the crosslinked irregularity-absorbing resin layer (C), thereby obtaining 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.

[Examples 2 to 6 and Comparative Example 1]
An adhesive film was obtained in the same manner as in Example 1, except that the adhesive coating liquid A for forming the adhesive resin layer (A) and the adhesive coating liquid C for forming the roughness-absorbing resin layer (C) were prepared with the compositions shown in Table 1, and the thickness of each layer was set as shown in Table 1.
(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, Examples 2 to 6, and Comparative Example 1.)
Incidentally, Comparative Example 1 differs from Examples 1 to 6 in that the unevenness-absorbing resin layer does not contain a thermal polymerization initiator (Perkadox 12-XL25) and a polyfunctional acrylic oligomer (NK Ester AD-TMP) and is not crosslinkable by an external stimulus.

<Evaluation>
(1) Evaluation of standoff 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 on the adhesive resin layer (A) of the adhesive film as electronic components and adhered to each other to obtain a structure.
Thereafter, in Examples 1 to 6, the structure was heated at 130°C for 30 minutes, thereby crosslinking (curing) the irregularity-absorbing resin layer (C). In Comparative Example 1, such heating was not performed.

Next, using a compression molding machine, the multiple silicon chips on the adhesive resin layer (A) were encapsulated by compression molding (125°C, 600 seconds) using a liquid epoxy resin encapsulant (manufactured by Nagase ChemteX Corporation, product name: R4212-2C). 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 post-mold curing at 150° C. for 60 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 standoff of the obtained sealing resin wafer was measured with a laser microscope, and the standoff of the electronic component was evaluated according to the following criteria.
○ (Good): Standoff is less than 10 μm × (Poor): Standoff is 10 μm or more

(2) Measurement of storage modulus E' of irregularity-absorbing resin layer (C) at 60 ° C. or 125 ° C. Using the adhesive coating solution C for forming the irregularity-absorbing resin layer (C) used in the examples and comparative examples, an irregularity-absorbing resin layer (C) having a thickness of 40 μm was produced separately from the adhesive film. Then, the obtained irregularity-absorbing resin layer (C) was laminated to obtain a sample for viscoelasticity measurement having a thickness of 1 mm.
The solid viscoelasticity of the obtained sample for viscoelasticity measurement was measured using a solid viscoelasticity measuring 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' of the roughness-absorbing resin layer (C) at 60°C or 125°C was then determined.

(3) Evaluation of convexity absorption (bump absorption) After attaching the self-releasing adhesive layer side of each tape to a slide glass, a 20 × 20 mm Si chip with linear convexities of 10 μm in height and 2 μm in width formed on the surface of the Si chip was mounted on the layer side consisting of the intermediate layer and the chip-side adhesive layer using an MD-P300 manufactured by Panasonic Corporation, and the evaluation was performed under the following mounting conditions: temperature: 60°C, mounting load: 2 N/chip, mounting time: 0.5 s.
The absorbability of the irregularities was confirmed by curing the tape at 130° C. for 30 minutes after mounting the chip, removing the mounted Si chip from the tape, and observing the surface on the tape side under a microscope.
In this case, if the linear depressions on the tape created by the transfer of the protrusions on the chip were shorter than the length of the protrusions on the chip, in other words, if the protrusions were not partially absorbed, it was determined that the protrusion absorption was insufficient (marked as "fault" in the table). If there were no problems with absorption, it was marked as "O" in the table.

As can be seen from Table 1, the irregularity-absorbing resin layer (C) is capable of being crosslinked by an external stimulus, thereby suppressing the occurrence of standoff, a defective sealing of electronic components.

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 Sealant 60A Sealant 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 (9)

The adhesive tape comprises a base layer, an adhesive resin layer (A) provided on a first surface side of the base layer and 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 an external stimulus ,
the irregularity-absorbing resin layer (C) contains a resin, a crosslinking agent, and an initiator that generates an active chemical species in response to an external stimulus;
An adhesive film, wherein the storage modulus E' at 125°C of the unevenness-absorbing resin layer (C') obtained by crosslinking the unevenness-absorbing resin layer (C) by an external stimulus is 5.0 x 105 Pa or more and 1.0 x 109 Pa or less, as measured using a solid viscoelasticity measuring device under conditions of a frequency of 1 Hz, a temperature rise rate of 5°C/min, a strain fixed mode of 0.05% strain, a ^chuck distance of 20 mm , and a sample width of ¹⁰ mm. The adhesive film according to claim 1,
An 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,
The adhesive film, wherein the external stimulus is heat or light. The adhesive film according to any one of claims 1 to 3,
An adhesive film, wherein the unevenness-absorbing resin layer (C) is provided at least between the substrate layer and the adhesive resin layer (A). The adhesive film according to any one of claims 1 to 4 ,
The thickness of the irregularity-absorbing resin layer (C) of the pressure-sensitive adhesive film is 10 μm or more and 1000 μm or less. The adhesive film according to any one of claims 1 to 5 ,
An adhesive film, wherein the adhesive resin constituting the adhesive resin layer (A) comprises one or more selected from the group consisting of (meth)acrylic adhesive resins, silicone adhesive resins, urethane adhesive resins, olefin adhesive resins, and styrene adhesive resins. The adhesive film according to any one of claims 1 to 6 ,
An adhesive film used to temporarily fix electronic components when the electronic components are sealed with a sealing material. The adhesive film according to claim 7 ,
The adhesive film has an uneven structure on the electronic component. The adhesive film according to claim 8 ,
The uneven structure of the electronic component is an adhesive film including bump electrodes.