WO2024101232A1 - Film and method for producing semiconductor package - Google Patents

Abstract

The present disclosure provides a film which comprises a base material and an antistatic layer, wherein the antistatic layer is formed of a cured product of a composition that contains an antistatic agent, a polymerization initiator and a urethane (meth)acrylate that comprises one or more (meth)acryloyl groups and one or more urethane bonds, while having a (meth)acryloyl group equivalent of 1,000 g/eq or more.

Description

Method for manufacturing film and semiconductor package

This disclosure relates to a method for manufacturing a film and a semiconductor package.

Semiconductor elements are sealed in a package and mounted on a board to protect them from the outside air. Hardening resins such as epoxy resins are used to seal semiconductor elements. Resin sealing is performed by placing the semiconductor element in a designated location in a mold, filling the mold with hardening resin, and then hardening it. When sealing semiconductor elements, a release film is often placed on the inner surface of the mold to improve the releasability of the package from the mold.

When a release film is used in the manufacture of semiconductor packages, static electricity is generated when the sealed semiconductor package is peeled off from the film, causing the film to become charged. Discharge from the charged film can then damage the semiconductor package.
In order to prevent static electricity from building up in the film, Patent Document 1 proposes providing an antistatic layer on one surface of the substrate.

International Publication No. 2016/125796

In recent years, as semiconductor package shapes have become more complex and semiconductor packages with exposed parts have greater height differences, films are increasingly being used to conform to these complex shapes. The inventors have found that when a film is stretched to conform to a complex shape, defects such as cracks and voids can occur in the film. These defects can lead to product defects. Therefore, there is a demand for a film that does not cause cracks or voids even in such cases.

The present disclosure provides a film that has sufficient antistatic properties and is less susceptible to cracks and voids even when stretched to conform to complex shapes, and a method for manufacturing a semiconductor package using the film.

The present disclosure provides a film having the following configurations [1] to [14] and a method for manufacturing a semiconductor package using the film.
[1] A film comprising a substrate and an antistatic layer,
The film, wherein the antistatic layer is a layer made of a cured product of a composition containing a urethane (meth)acrylate having one or more (meth)acryloyl groups and one or more urethane bonds and having a (meth)acryloyl group equivalent of 1,000 g/eq or more, an antistatic agent, and a polymerization initiator.
[2] The film according to [1], wherein the urethane (meth)acrylate comprises a multifunctional urethane (meth)acrylate having two or more (meth)acryloyl groups.
[3] The film according to [1] or [2], wherein the urethane (meth)acrylate has at least one structure selected from the group consisting of a polyether structure, a polyester structure, and a polycarbonate structure.
[4] The film according to any one of [1] to [3], wherein the composition contains a polyfunctional (meth)acrylate other than the urethane (meth)acrylate.
[5] The film according to any one of [1] to [4], wherein the substrate comprises at least one selected from the group consisting of a fluororesin, polymethylpentene, syndiotactic polystyrene, polycycloolefin, silicone rubber, polyester elastomer, polybutylene terephthalate, polyethylene terephthalate, and polyamide.
[6] The film according to [5], wherein the fluororesin comprises at least one selected from the group consisting of ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer, and tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer.
[7] The film according to any one of [1] to [6], wherein the antistatic agent comprises a conductive polymer.
[8] The film according to any one of [1] to [6], wherein the antistatic agent contains a chain-like conductive filler.
[9] The film according to any one of [1] to [8], wherein the polymerization initiator is a photopolymerization initiator.
[10] The film of any one of [1] to [9], wherein the composition further comprises a surface modifier.
[11] The film of any one of [1] to [10] above, further comprising an adhesive layer.
[12] The film according to any one of [1] to [11] above, which is a release film.
[13] The film according to any one of [1] to [12] above, which is a release film used in a step of encapsulating a semiconductor element with a curable resin.
[14] Placing a film according to any one of [1] to [13] on an inner surface of a mold;
placing a substrate having a semiconductor element fixed thereto within the die in which the film is placed;
encapsulating the semiconductor element in the mold with a curable resin to produce an encapsulated body;
and releasing the sealing body from the mold.

This disclosure provides a film that has sufficient antistatic properties and is less susceptible to cracks and voids even when stretched to conform to complex shapes, as well as a method for manufacturing a semiconductor package using the film.

FIG. 1 is a schematic cross-sectional view showing one embodiment of the present film. FIG. 2 is a schematic cross-sectional view showing another embodiment of the present film.

The following describes in detail the embodiments of the present disclosure. However, the embodiments of the present disclosure are not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, and they do not limit the embodiments of the present disclosure.

In the present disclosure, the term "step" includes not only a step that is independent of other steps, but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.
In the present disclosure, the numerical range indicated using "to" includes the numerical values before and after "to" as the minimum and maximum values, respectively.
In the numerical ranges described in the present disclosure in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value of the numerical range may be replaced with a value shown in the examples.
In the present disclosure, each component may contain multiple types of the corresponding substance. When multiple substances corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified.
When an embodiment is described with reference to the drawings in this disclosure, the configuration of the embodiment is not limited to the configuration shown in the drawings. In addition, the sizes of components in the drawings are conceptual, and the relative relationships between the sizes of the components are not limited to these.

In this disclosure, the term "unit" of a polymer refers to a portion derived from a monomer that exists in the polymer and constitutes the polymer. The term "unit" also refers to a unit that is obtained by chemically converting the structure of a unit after the formation of the polymer. In some cases, units derived from individual monomers are referred to by the name of the monomer with "unit" added.
In this disclosure, films and sheets are referred to as "films" regardless of their thickness.
In the present disclosure, acrylate and methacrylate are collectively referred to as "(meth)acrylate", acrylic and methacrylic are collectively referred to as "(meth)acrylic", and acryloyl and methacryloyl are collectively referred to as "(meth)acryloyl".

〔film〕
A film according to an embodiment of the present disclosure (hereinafter also referred to as "the film") is a film including a substrate and an antistatic layer, and the antistatic layer is a layer made of a cured product of a composition (hereinafter also referred to as "antistatic layer composition") that includes a urethane (meth)acrylate having one or more (meth)acryloyl groups and one or more urethane bonds and having a (meth)acryloyl group equivalent of 1000 g/eq or more, an antistatic agent, and a polymerization initiator.

The present film is not particularly limited as long as it contains a substrate and an antistatic layer.
FIG. 1 is a schematic cross-sectional view showing one embodiment of the present film. The film 1 shown in FIG. 1 includes a substrate 2 and an antistatic layer 3 in this order. FIG. 2 is a schematic cross-sectional view showing another embodiment of the present film. The film 1 shown in FIG. 2 includes a substrate 2, an antistatic layer 3, and an adhesive layer 4 in this order. When the film 1 is used for sealing a semiconductor element, the substrate 2 is disposed so as to contact a die, and after resin sealing, the antistatic layer 3 or the adhesive layer 4 contacts a sealing body (i.e., a semiconductor package in which a semiconductor element is sealed). The film 1 may include other layers in addition to the substrate 2, the antistatic layer 3, and the adhesive layer 4.
Each component of the film is described in detail below.

(Base material)
The material of the substrate is not particularly limited.
The substrate typically contains a resin, such as a fluororesin, polymethylpentene, syndiotactic polystyrene, polycycloolefin, silicone rubber, polyester elastomer, polybutylene terephthalate, polyethylene terephthalate, or polyamide.
In one embodiment, from the viewpoint of excellent releasability of the film, it is preferable that the substrate contains a resin having releasability (hereinafter, also referred to as "releasable resin"). The releasable resin means a resin in which a layer composed of the resin has releasability. Examples of the releasable resin include fluororesin, polymethylpentene, syndiotactic polystyrene, polycycloolefin, silicone rubber, polyester elastomer, polybutylene terephthalate, polyamide, etc. From the viewpoint of excellent releasability, heat resistance, strength, and elongation at high temperatures, fluororesin, polymethylpentene, syndiotactic polystyrene, and polycycloolefin are preferable, and from the viewpoint of excellent releasability, fluororesin is more preferable.
The resin contained in the substrate may be one type or two or more types. It is particularly preferable that the resin contained in the substrate is composed solely of a fluororesin. However, even if the substrate is composed solely of a fluororesin, it does not prevent the substrate from containing a resin other than the fluororesin as long as the effect of the invention is not impaired.

As the fluororesin, from the viewpoint of excellent releasability and heat resistance, a fluoroolefin polymer is preferable. The fluoroolefin polymer is a polymer having units based on a fluoroolefin. The fluoroolefin polymer may further have units other than the units based on a fluoroolefin.
Examples of the fluoroolefin include tetrafluoroethylene (hereinafter also referred to as "TFE"), vinyl fluoride, vinylidene fluoride, trifluoroethylene, hexafluoropropylene (hereinafter also referred to as "HFP"), chlorotrifluoroethylene, etc. One type of fluoroolefin may be used alone, or two or more types may be used in combination.

The fluoroolefin polymers include ethylene-TFE copolymer (hereinafter also referred to as "ETFE"), TFE-HFP copolymer (hereinafter also referred to as "FEP"), TFE-perfluoro(alkyl vinyl ether) copolymer, TFE-HFP-vinylidene fluoride copolymer, etc. From the viewpoint of mechanical properties, at least one selected from the group consisting of ETFE and FEP is preferable. One type of fluoroolefin polymer may be used alone, or two or more types may be used in combination.

From the viewpoint of high elongation at high temperatures, ETFE is a preferred fluoroolefin polymer. ETFE is a copolymer having units based on TFE (hereinafter also referred to as "TFE units") and units based on ethylene (hereinafter also referred to as "E units").
As ETFE, the polymer having TFE unit, E unit, and unit based on a third monomer other than TFE and ethylene is preferred.By the type and content of unit based on third monomer, it is easy to adjust the crystallinity of ETFE, and thus it is easy to adjust the storage modulus or other tensile properties of substrate.For example, by ETFE having unit based on third monomer (particularly monomer having fluorine atom), tensile strength and tensile elongation at high temperature (particularly around 180 ℃) tend to improve.

The third monomer includes a monomer having a fluorine atom and a monomer having no fluorine atom.
Examples of the monomer having a fluorine atom include the following monomers a1 to a5.
Monomer a1: Fluoroolefins having 2 or 3 carbon atoms.
Monomer a2: Fluoroalkylethylenes represented by X(CF ₂ ) _n CY═CH ₂ (wherein X and Y each independently represent a hydrogen atom or a fluorine atom, and n represents an integer of 2 to 8).
Monomer a3: Fluorovinyl ethers.
Monomer a4: functional group-containing fluorovinyl ethers.
Monomer a5: a fluorine-containing monomer having an aliphatic ring structure.

Specific examples of monomer a1 include fluoroethylenes (trifluoroethylene, vinylidene fluoride, vinyl fluoride, chlorotrifluoroethylene, etc.) and fluoropropylenes (hexafluoropropylene (HFP), 2-hydropentafluoropropylene, etc.).

As the monomer a2, a monomer in which n is 2 to 6 is preferred, and a monomer in which n is 2 to 4 is more preferred. Also, a monomer in which X is a fluorine atom and Y is a hydrogen atom, that is, (perfluoroalkyl)ethylene, is preferred.
Specific examples of the monomer a2 include the following compounds.
_{CF3CF2CH = CH2} ,
_{CF3CF2CF2CF2CH} = _CH2 ((perfluorobutyl)ethylene ₍ hereinafter _also referred to as " _PFBE ")),
_{CF3CF2CF2CF2CF = CH2 , ​
CF2HCF2CF2CF = CH2 ,
CF2HCF2CF2CF2CF = CH2 . ​}

Specific examples of the monomer a3 include the following compounds: Among the following, diene monomers are monomers that can be cyclopolymerized.
_CF2 = _CFOCF3 ,
_CF2 = _{CFOCF2CF3 ,}
CF ₂ ═CFO(CF ₂ ) ₂ CF ₃ (perfluoro(propyl vinyl ether) (hereinafter also referred to as “PPVE”)),
_CF2 = _CFOCF2CF ( _CF3 )O( _CF2 ) _{2CF3 ,
CF2} =CFO( _CF2 ) _3O ( _CF2 ) _{2CF3 ,
CF2} =CFO( _{CF2CF ( CF3} )O) ₂ ( _CF2 ) _2CF3 ,
_CF2 = _CFOCF2CF ( _CF3 )O( _CF2 ) _{2CF3 ,
CF2} = _CFOCF2CF = _CF2 ,
_CF2 =CFO( _CF2 ) _2CF = _CF2 .

Specific examples of the monomer a4 include the following compounds.
_CF2 =CFO( _{CF2 ) 3CO2CH3 ,
CF2} = _CFOCF2CF ( _CF3 ) _O ( _CF2 ) _{3CO2CH3 ,
CF2} = _CFOCF2CF ( _CF3 )O( _CF2 ) _{2SO2F .}

Specific examples of monomer a5 include perfluoro(2,2-dimethyl-1,3-dioxole), 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole, and perfluoro(2-methylene-4-methyl-1,3-dioxolane).

Examples of the monomer having no fluorine atom include the following monomers b1 to b4.
Monomer b1: Olefins.
Monomer b2: vinyl esters.
Monomer b3: vinyl ethers.
Monomer b4: unsaturated acid anhydride.

Specific examples of the monomer b1 include propylene and isobutene.
A specific example of the monomer b2 is vinyl acetate.
Specific examples of the monomer b3 include ethyl vinyl ether, butyl vinyl ether, cyclohexyl vinyl ether, and hydroxybutyl vinyl ether.
Specific examples of the monomer b4 include maleic anhydride, itaconic anhydride, citraconic anhydride, and 5-norbornene-2,3-dicarboxylic anhydride.

The third monomer may be used alone or in combination of two or more kinds.
As the third monomer, from the viewpoint of easy adjustment of crystallinity and excellent tensile strength and tensile elongation at high temperature (particularly around 180 ° C.), monomer a2, HFP, PPVE and vinyl acetate are preferred, HFP, PPVE, CF ₃ CF ₂ CH = CH ₂ and PFBE are more preferred, and PFBE is particularly preferred. That is, as ETFE, a copolymer having TFE unit, E unit and unit based on PFBE (hereinafter also referred to as "PFBE unit" is particularly preferred.

In ETFE, the molar ratio of TFE units to E units (TFE units/E units) is preferably 80/20 to 40/60, more preferably 70/30 to 45/55, and even more preferably 65/35 to 50/50. When the TFE units/E units ratio is within the above range, the ETFE has excellent heat resistance and mechanical strength.

The proportion of units based on the third monomer in ETFE is preferably 0.01 to 20 mol%, more preferably 0.10 to 15 mol%, and even more preferably 0.20 to 10 mol%, relative to the sum of all units constituting ETFE (100 mol%). When the proportion of units based on the third monomer is within the above range, ETFE has excellent heat resistance and mechanical strength.

When the units based on the third monomer contain PFBE units, the proportion of PFBE units is preferably 0.5 to 4.0 mol%, more preferably 0.7 to 3.6 mol%, and even more preferably 1.0 to 3.6 mol%, relative to the total of all units constituting ETFE (100 mol%). When the proportion of PFBE units is within the above range, the tensile strength and tensile elongation of the film at high temperatures, particularly at around 180°C, are improved.

The substrate may consist of resin only, or may contain other components in addition to resin. Examples of other components include lubricants, antioxidants, antistatic agents, plasticizers, and mold release agents. From the viewpoint of preventing the substrate from soiling the mold, it is preferable that the substrate does not contain other components.

The thickness of the substrate is preferably 25 to 250 μm, more preferably 50 to 150 μm, and even more preferably 75 to 125 μm. When the thickness of the substrate is equal to or less than the upper limit of the above range, the film is easily deformable and has excellent mold conformability. When the thickness of the substrate is equal to or more than the lower limit of the above range, the film is easy to handle, for example, in a roll-to-roll process, and wrinkles are unlikely to occur when the film is stretched and placed to cover the cavity of a mold.
The thickness of the substrate can be measured in accordance with ISO 4591:1992 (JIS K7130:1999) (B1 method: a method for measuring the thickness of a sample taken from a plastic film or sheet by a mass method). The same applies to the thickness of each layer of the film hereinafter.

The surface of the substrate may have a surface roughness. The arithmetic mean roughness Ra of the substrate surface is preferably 0.2 to 3.0 μm, more preferably 0.5 to 2.5 μm. When the arithmetic mean roughness Ra of the substrate surface is equal to or greater than the lower limit of the above range, the releasability from the mold is more excellent. When the arithmetic mean roughness Ra of the substrate surface is equal to or less than the upper limit of the above range, pinholes are less likely to form in the film.
The arithmetic mean roughness Ra is measured based on JIS B0601:2013 (ISO 4287:1997, Amd.1:2009). The reference length lr (cutoff value λc) for the roughness curve is 0.8 mm.

The substrate may be unstretched or stretched. For example, unstretched polyamide film, biaxially oriented polyamide film, biaxially oriented PET (polyethylene terephthalate) film, biaxially oriented PEN (polyethylene naphthalate) film, biaxially oriented syndiotactic polystyrene film, and unstretched PBT (polybutylene terephthalate) film are commercially available. Other films that can be used include polyimide film, polyphenylene sulfide resin film, and cross-linked polyethylene film.

The surface of the substrate adjacent to other layers may be subjected to any surface treatment. Examples of surface treatments include corona treatment, plasma treatment, application of a silane coupling agent, application of an adhesive, etc. From the viewpoint of adhesion between the substrate and other layers, corona treatment or plasma treatment is preferred.

From the viewpoint of adhesion between the substrate and the adjacent layer, the wetting tension of the surface of the substrate on the antistatic layer side is preferably 20 mN/m or more, more preferably 30 mN/m or more, and particularly preferably 35 mN/m or more. There is no particular upper limit to the wetting tension, and it may be 80 mN/m or less.

The substrate may be a single layer or may have a multi-layer structure. The multi-layer structure may be a structure in which a plurality of layers, each of which contains a resin, are laminated. In this case, the resins contained in the plurality of layers may be the same or different. From the viewpoint of mold followability, tensile elongation, production cost, etc., the substrate is preferably a single layer. From the viewpoint of film strength, the substrate is preferably a multi-layer structure.
The multilayer structure may be, for example, a structure in which a layer containing the above-mentioned release resin (preferably a fluororesin) is laminated on a resin film (which may be a film containing only resin) containing a resin such as polyester, polybutylene terephthalate, polystyrene (preferably syndiotactic), or polycarbonate, or a structure in which a layer containing a first release resin, the resin film, and a layer containing a second release resin are laminated in this order. The layer containing the release resin and the resin film may be laminated via an adhesive. One or both sides of each layer containing a release resin may be subjected to a corona treatment or plasma treatment. When the substrate has such a multilayer structure, it is preferable that the layer containing the release resin is disposed on the antistatic layer side. When the substrate has such a multilayer structure, it is preferable that the surface of the antistatic layer side of the layer containing the release resin disposed on the antistatic layer side is subjected to a corona treatment or plasma treatment.

(Antistatic Layer)
The antistatic layer is made of a cured product of a composition for forming an antistatic layer, which will be described in detail later.
The antistatic layer may be provided on the substrate so as to be adjacent to the substrate, or may be provided on the substrate via another layer which is adjacent to the substrate.

The thickness of the antistatic layer is preferably 0.05 to 3.0 μm, and more preferably 0.1 to 2.5 μm. When the thickness of the antistatic layer is equal to or greater than the lower limit, the antistatic function is excellent. When the thickness of the antistatic layer is equal to or less than the upper limit of the range, the film is more easily stretched, and the effect of suppressing the occurrence of cracks and voids is more excellent. In addition, the stability of the production process, including the appearance of the coated surface, is excellent.

<Antistatic Layer Composition>
The composition for the antistatic layer contains a urethane (meth)acrylate (hereinafter also referred to as "specific urethane (meth)acrylate") having one or more (meth)acryloyl groups and one or more urethane bonds and having a (meth)acryloyl group equivalent of 1,000 g/eq or more, an antistatic agent, and a polymerization initiator.
The composition for the antistatic layer may further contain a polymerizable compound other than the specific urethane (meth)acrylate.
The composition for the antistatic layer may further contain other components different from the specific urethane (meth)acrylate and the polymerizable compound other than the specific urethane (meth)acrylate.
The specific urethane (meth)acrylate and the polymerizable compound other than the specific urethane (meth)acrylate are polymerized by the action of a polymerization initiator, and the polymerized product functions as a binder for dispersing the antistatic agent.

The urethane bonds contained in certain urethane (meth)acrylates are characterized by their high cohesive strength resulting from hydrogen bonds, which act to suppress breakage within the antistatic layer due to shear applied during film stretching, and are thought to be linked to the effect of suppressing breakage within the layer that would appear as cracks or voids.
The specific urethane (meth)acrylate may be a urethane (meth)acrylate having one urethane bond, a urethane (meth)acrylate having two or more urethane bonds, or a mixture thereof.
The specific urethane (meth)acrylate may be a monofunctional urethane (meth)acrylate having one (meth)acryloyl group, a polyfunctional urethane (meth)acrylate having two or more (meth)acryloyl groups, or a mixture thereof. The monofunctional urethane (meth)acrylate and the polyfunctional urethane (meth)acrylate may each be used alone or in combination of two or more.

Since the (meth)acryloyl group equivalent of the specific urethane (meth)acrylate is 1,000 g/eq or more, the film has excellent extensibility, and cracks and voids are less likely to occur even when the film is stretched to conform to a complex shape in the production of a semiconductor package having a complex shape.
The (meth)acryloyl group equivalent of the specific urethane (meth)acrylate is preferably 1,500 g/eq or more, more preferably 5,000 g/eq or more. The upper limit of the (meth)acryloyl group equivalent is not particularly limited, but may be, for example, 100,000 g/eq or even 50,000 g/eq. The lower limit and the upper limit can be appropriately combined.

The "(meth)acryloyl group equivalent" is the value obtained by dividing the molecular weight of the (meth)acrylate by the number of (meth)acryloyl groups. The molecular weight of the (meth)acrylate is the value of the mass average molecular weight (hereinafter also referred to as "Mw") obtained by gel permeation chromatography (hereinafter also referred to as "GPC") measurement for compounds whose molecular weight distribution can be obtained by GPC measurement, and is the formula weight calculated from the structural formula for compounds whose molecular weight distribution cannot be obtained by GPC measurement. Mw is a value calculated in terms of polystyrene obtained by GPC measurement using a calibration curve prepared using standard polystyrene samples with known molecular weights.
When the composition for the antistatic layer contains two or more types of urethane (meth)acrylates, the (meth)acryloyl group equivalent of the urethane (meth)acrylate is the sum of the values obtained by multiplying the (meth)acryloyl group equivalent of each of the two or more types of urethane (meth)acrylates by the mass fraction of each urethane (meth)acrylate.
A urethane (meth)acrylate having a (meth)acryloyl group equivalent of less than 1,000 g/eq may be contained, so long as the total (meth)acryloyl group equivalent of the two or more urethane (meth)acrylates is not less than 1,000 g/eq.

From the viewpoint of preventing unreacted monomers from being easily detached from the antistatic layer, the specific urethane (meth)acrylate preferably contains a polyfunctional urethane (meth)acrylate, because by having a plurality of reactive groups in the molecule, one or more of the reactive groups are incorporated in the curing reaction and do not detach from the antistatic layer.
From the viewpoint of obtaining high extensibility without excessively increasing the crosslinking density of the antistatic layer, the number of (meth)acryloyl groups in the polyfunctional urethane (meth)acrylate is preferably 4 or less, more preferably 3 or less, and particularly preferably 2. Therefore, the polyfunctional urethane (meth)acrylate is particularly preferably a bifunctional urethane (meth)acrylate.

The specific urethane (meth)acrylate preferably has at least one structure selected from the group consisting of a polyether structure, a polyester structure, and a polycarbonate structure, more preferably has at least one structure selected from the group consisting of a polyether structure and a polyester structure, and even more preferably has a polyester structure. When the specific urethane (meth)acrylate has such a structure, the structure relaxes to follow the deformation during stretching, making chemical bonds less likely to break, and it tends to have an excellent effect of suppressing the occurrence of cracks and voids.

The specific urethane (meth)acrylate can be produced by a known method. For example, the specific urethane (meth)acrylate can be obtained by any of the following methods.
(1) A method of reacting a compound having one or more hydroxyl groups (hereinafter also referred to as “compound a”) with a compound having an isocyanate group and a (meth)acryloyl group (hereinafter also referred to as “compound b”).
(2) A method in which compound a is reacted with a compound having two isocyanate groups (hereinafter also referred to as "compound c") to obtain a prepolymer having one or more isocyanate groups, and then the prepolymer is reacted with a compound having a hydroxyl group and a (meth)acryloyl group (hereinafter also referred to as "compound d").

The number of hydroxyl groups in compound a is 1 when a monofunctional urethane (meth)acrylate is obtained, and is 2 or more when a polyfunctional urethane (meth)acrylate is obtained. The number of hydroxyl groups in compound a is preferably 4 or less, and particularly preferably 2.
Examples of compound a include polyether monol (such as methoxypolyethylene glycol), polyether polyol (such as polyethylene glycol), polyester monol, polyester polyol, polycarbonate monol, and polycarbonate polyol.
Compound a is preferably one which gives a urethane (meth)acrylate having a (meth)acryloyl group equivalent of 1,000 g/eq or more, and among these, from the viewpoint of excellent effect of suppressing the occurrence of cracks and voids, one having at least one structure selected from the group consisting of a polyether structure, a polyester structure, and a polycarbonate structure is preferred.

Examples of compound b include isocyanatoalkyl (meth)acrylates such as 2-isocyanatoethyl (meth)acrylate.

Examples of the compound c include various polyfunctional isocyanate compounds such as hexamethylene diisocyanate (HDI), tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), isophorone diisocyanate (IPDI), xylene diisocyanate (XDI), triphenylmethane triisocyanate, and tris(isocyanate phenyl)thiophosphate. Also included are isocyanurate bodies (trimers) and biuret bodies of these polyfunctional isocyanate compounds, and reaction products (adducts, bifunctional prepolymers, trifunctional prepolymers, etc.) of these polyfunctional isocyanate compounds with polyol compounds. Also included are compounds in which the isocyanate groups of these polyfunctional isocyanate compounds are protected with a blocking agent. Examples of blocking agents include phenols such as m-cresol and guaiacol, benzenethiol, ethyl acetoacetate, diethyl malonate, and ε-caprolactam.
The number of isocyanate groups in compound c is preferably 4 or less, and particularly preferably 2.

Examples of compound d include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1,4-cyclohexanedimethanol monoacrylate, and 2-acryloyloxyethyl-2-hydroxyethyl-phthalic acid.

The number of urethane bonds in the specific urethane (meth)acrylate is preferably 4 or less, more preferably 3 or less, from the viewpoint of obtaining high extensibility without increasing the crosslink density of the antistatic layer too much. The number of urethane bonds in the specific urethane (meth)acrylate may be 1 or more, and is preferably 2 or more, from the viewpoint of preventing unreacted monomer from being easily detached from the antistatic layer.

The specific urethane (meth)acrylate may be a commercially available product. Examples of commercially available products include U-200PA, UA-W2, UA-W2A, UA-2235PE, UA-290TM, UA-1138P, UA-3573AB, and UA-2374PIB (all product names) manufactured by Shin-Nakamura Chemical Co., Ltd., UF-3003, UF-3003M, UF-3007, UF-3007M, UF-3123M, UF-3223BA, UF-3999BA, UF-3999AM, UF-3999HX, and UF-0146 (all product names) manufactured by Kyoeisha Chemical Co., Ltd., and UN-5500, UN-5590, UN-9200A, and UN-9000PEP manufactured by Negami Chemical Co., Ltd.

The polymerizable compound other than the specific urethane (meth)acrylate may be any compound that is copolymerizable with the specific urethane (meth)acrylate, and may include, for example, a compound having a polymerizable functional group such as a (meth)acryloyl group or a vinyl group. The number of polymerizable functional groups may be one or two or more. From the viewpoint of easily suppressing the detachment of unreacted monomers from the antistatic layer after curing, the number of polymerizable functional groups is preferably two or more.
The polymerizable compound other than the specific urethane (meth)acrylate may contain a compound having a thiol group that is incorporated into the polymerization product by causing a thiol-ene reaction. When the compound having a thiol group is contained, the flexibility and toughness of the antistatic layer can be increased.
As the polymerizable compound other than the specific urethane (meth)acrylate, from the viewpoint of excellent copolymerizability and compatibility with the specific urethane (meth)acrylate, (meth)acrylate is preferable. Examples of the (meth)acrylate include the monofunctional (meth)acrylate and polyfunctional (meth)acrylate shown below.

Monofunctional (meth)acrylate:
Methoxypolyethylene glycol (meth)acrylate, phenoxydiethylene glycol (meth)acrylate, ethoxylated o-phenylphenol (meth)acrylate, 2-(meth)acryloyloxyethyl succinate, isobornyl (meth)acrylate, isononyl (meth)acrylate, and the like.

Polyfunctional (meth)acrylate:
Bifunctional (meth)acrylates such as 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 2-hydroxy-3-methacrylpropyl (meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, and ethoxylated bisphenol A di(meth)acrylate;
Trifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, ethoxylated glycerin tri(meth)acrylate, tris-(2-(meth)acryloxyethyl)isocyanurate, and pentaerythritol tri(meth)acrylate;
tetrafunctional (meth)acrylates such as pentaerythritol tetra(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, and ditrimethylolpropane tetra(meth)acrylate;
(Meth)acrylates having five or more functional groups, such as dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ethoxylated dipentaerythritol hexa(meth)acrylate.

From the viewpoint of improving the hardness of the antistatic layer and preventing unreacted monomers from being released from the antistatic layer, the (meth)acrylate is preferably a polyfunctional (meth)acrylate.
The number of (meth)acryloyl groups in the polyfunctional (meth)acrylate is preferably 6 or less, particularly preferably 3 or less, from the viewpoint of obtaining high extensibility without excessively increasing the crosslinking density of the antistatic layer.

Examples of antistatic agents include ionic liquids, conductive polymers, conductive fillers, etc. One type of antistatic agent may be used alone, or two or more types may be used in combination.

Examples of the ionic liquid include onium compounds such as pyridinium and imidazolium, and fluorine-based compounds.
A conductive polymer is a polymer in which electrons move and diffuse through the polymer skeleton. Examples of the conductive polymer include a conductive polymer having a polyaniline skeleton, a conductive polymer having a polyacetylene skeleton, a conductive polymer having a polyparaphenylene skeleton, a conductive polymer having a polypyrrole skeleton, a conductive polymer having a polythiophene skeleton, and a conductive polymer having a polyvinylcarbazole skeleton.
Examples of the conductive filler include metal ion conductive salts, metal-based fillers such as metals and fillers coated with metals, metal oxide-based fillers such as metal oxides and fillers coated with metal oxides, and carbon-based fillers such as conductive carbon and conductive carbon nanotubes. The shape of the conductive filler is not limited, but needle-like, fibrous, and chain-like fillers are preferred.
Examples of metal ion conductive salts include lithium salt compounds.
Examples of the metal as the conductive filler and the metal that coats the filler include gold, silver, copper, nickel, and cobalt.
Examples of metal oxides as the conductive filler and metal oxides coating the filler include tin oxide, tin-doped indium oxide (ITO), antimony-doped tin oxide (ATO), phosphorus-doped tin oxide (PTO), zinc antimonate, and antimony oxide.

The antistatic agent preferably contains a conductive polymer, from the viewpoint of easily maintaining antistatic performance even after stretching. In such a case, the conductive path is less likely to be destroyed by deformation during stretching. As the conductive polymer, from the viewpoint of excellent heat resistance and conductivity, at least one selected from the group consisting of conductive polymers having a polyaniline skeleton, conductive polymers having a polyacetylene skeleton, conductive polymers having a polyparaphenylene skeleton, conductive polymers having a polypyrrole skeleton, conductive polymers having a polythiophene skeleton, and conductive polymers having a polyvinylcarbazole skeleton is preferable. Among them, from the viewpoint of easily exhibiting good conductive performance even with a small amount of addition and excellent environmental stability, the conductive polymer is preferably a conductive polymer having a polythiophene skeleton, and poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid (PEDOT-PSS) is particularly preferable.

From the viewpoint of easily maintaining the antistatic ability even after stretching, the antistatic agent preferably contains a conductive filler, more preferably a chain-like conductive filler. When the antistatic agent contains a chain-like conductive filler, the chain structure is relaxed in response to deformation during stretching, so that the conductive path is not easily broken. In addition, recombination of the connection points of the chain-like conductive filler occurs during stretching, and the conductive path is easily reformed.
The aspect ratio of the chain-like conductive filler is preferably 5 or more, more preferably 10 or more. The upper limit of the aspect ratio is not particularly limited, but is, for example, 100. An example of a chain-like conductive filler having an aspect ratio of 5 or more is a filler having a structure in which 5 or more conductive particles (for example, the above-mentioned metal or metal oxide particles) are connected. The chain-like conductive filler may have a branch.
The aspect ratio can be determined from the ratio of the length in the major axis direction to the length in the minor axis direction by observing an image under an electron microscope or the like.
From the viewpoint of excellent conductivity and durability, the chain-like conductive filler is preferably at least one selected from the group consisting of metal-based fillers, metal oxide-based fillers, and carbon-based fillers. Among them, from the viewpoint of excellent durability and small fluctuation of antistatic ability depending on the use environment, the chain-like conductive filler is preferably a metal oxide-based filler. Examples of the chain-like metal-based filler include metal nanowires such as gold nanowires, silver nanowires, and copper nanowires. Examples of the chain-like metal oxide filler include chain-like ATO materials, etc.

Examples of the polymerization initiator include a photopolymerization initiator and a thermal polymerization initiator.
The polymerization initiator is preferably a photopolymerization initiator. When the polymerization initiator is a photopolymerization initiator, the antistatic layer composition can be quickly cured by irradiation with active energy rays, and productivity is excellent. For example, the time required for curing is shorter than in the case of thermal curing, and the speed of continuous production (coating process) can be increased. In addition, in the case of thermal curing, aging is required after curing, but in the case of irradiation with active energy rays, aging is not necessary.

　The photopolymerization initiator may be any known compound, such as α-hydroxyacetophenone (α-hydroxyphenyl ketone), α-aminoacetophenone, benzil ketal, or other alkylphenone compounds, acylphosphine oxide compounds, oxime ester compounds, oxyphenylacetic acid esters, benzoin ethers, aromatic ketones (benzophenones), ketone/amine compounds, benzoylformic acid, and its ester derivatives.

Specific examples of the photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin butyl ether, diethoxyacetophenone, benzyl dimethyl ketal, 2-hydroxy-2-methylpropiophenone, 1-hydroxycyclohexyl phenyl ketone, benzophenone, 2,4,6-trimethylbenzoin diphenylphosphine oxide, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propanone, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, Michler's ketone, N,N-dimethylaminobenzoic acid isoamyl, 2-chlorothioxanthone, 2,4-diethylthioxanthone, benzoylformic acid, methyl benzoylformate, and ethyl benzoylformate.
The photopolymerization initiator may be used alone or in combination of two or more kinds.

Other components that may be contained in the antistatic layer composition include various additives such as lubricants, colorants, coupling agents, and surface modifiers.
Examples of the lubricant include microbeads made of a thermoplastic resin, fumed silica, and polytetrafluoroethylene (PTFE) particles.
Examples of colorants include various organic and inorganic colorants, more specifically, cobalt blue, red iron oxide, cyanine blue, and the like.
Examples of the coupling agent include a silane coupling agent and a titanate coupling agent.

When the composition for the antistatic layer contains a surface modifier, it is possible to adjust surface properties such as surface tackiness, adhesion, contact angle, etc. In particular, when an adhesive layer is not provided, it is preferable that the composition for the antistatic layer contains a surface modifier.
The surface modifier is preferably one that can be unevenly distributed on the surface of the antistatic layer and its vicinity when the antistatic layer is formed and has good compatibility with other materials such as urethane (meth)acrylate, and examples thereof include silicone-based surface modifiers, fluorine-based surface modifiers, and fluorine-silicone-based surface modifiers. Examples of silicone-based surface modifiers include BYK-UV3505 manufactured by BYK Corporation, and X-22-164, X-22-164AS, X-22-164A, X-22-164B, X-22-164C, X-22-164E, KP-410, KP-411, KP-412, KP-413, KP-414, KP-415, KP-423, KP-416, KP-418, KP-422, and KP-420 manufactured by Shin-Etsu Chemical Co., Ltd. Examples of the fluorine-based surface modifier include KY-1203, X-71-1203E, KY-1211, and KY-1207 manufactured by Shin-Etsu Chemical Co., Ltd. Examples of the fluorine-silicone surface modifier include KP-911 manufactured by Shin-Etsu Chemical Co., Ltd.

The surface modifier preferably has a polymerizable functional group such as a (meth)acryloyl group. If the surface modifier has a polymerizable functional group, it reacts with urethane (meth)acrylate or the like when the composition for the antistatic layer is cured, and the surface modifier is fixed in and on the surface of the antistatic layer, making it possible to prevent the surface modifier from being transferred to an object such as an electronic component when the film comes into contact with the object.

In the composition for the antistatic layer, the content of the specific urethane (meth)acrylate is preferably 20 to 99% by mass, and more preferably 40 to 90% by mass, based on the total amount of the composition for the antistatic layer. When the content of the specific urethane (meth)acrylate is equal to or greater than the lower limit, the effect of suppressing the occurrence of cracks and voids is more excellent. When the content of the specific urethane (meth)acrylate is equal to or less than the upper limit, the content of the antistatic agent can be increased.

The proportion of the polyfunctional urethane (meth)acrylate to the total amount of the specific urethane (meth)acrylate is preferably 50% by mass or more, more preferably 80% by mass or more, and may be 100% by mass.

The content of the polymerizable compound other than the specific urethane (meth)acrylate is preferably 50% by mass or less, more preferably 20% by mass or less, and may be 0% by mass, based on the total amount of the antistatic layer composition.

From the viewpoint of fully exerting the antistatic function, the content of the antistatic agent is preferably an amount that causes the surface resistivity of the film to fall within the range described below.
In one embodiment, the content of the antistatic agent is preferably 1 to 60% by mass, more preferably 10 to 50% by mass, based on the total amount of the composition for the antistatic layer. When the content of the antistatic agent is equal to or more than the lower limit, the surface resistivity of the film tends to be in a suitable range. When the content of the antistatic agent is equal to or less than the upper limit, the curability of the composition for the antistatic layer tends to be good.

The content of the polymerization initiator is preferably 1 to 10 mass %, more preferably 2 to 5 mass %, based on the total of the specific urethane (meth)acrylate and the polymerizable compound other than the specific urethane (meth)acrylate.

The contents of the other components are appropriately set depending on the desired surface resistance and strength of the antistatic layer.
When the composition for antistatic layer contains a surface modifier, the content of the surface modifier is preferably 0.1 to 10% by mass, and more preferably 1 to 5% by mass, based on the total amount of the composition for antistatic layer. When the content of the surface modifier is equal to or more than the lower limit, the modifying effect is easily exhibited, whereas when the content is equal to or less than the upper limit, the occurrence of poor appearance and transfer to the product side due to detachment of the surface modifier due to poor curing are suppressed.

(Adhesive layer)
The adhesive layer has adhesiveness to other members (e.g., electronic components). By having the adhesive layer, the adhesion between the film and other members is improved. For example, when a semiconductor package having an exposed portion is manufactured, the exposed portion and the film are well adhered to each other, so that the sealing resin is less likely to penetrate into the exposed portion.
The adhesive layer may be provided on the antistatic layer so as to be adjacent to the antistatic layer, or may be provided on the antistatic layer via another layer which is adjacent to the antistatic layer.

The material of the adhesive layer is not particularly limited, and examples thereof include a cured product of a thermosetting adhesive layer composition, a cured product of an active energy ray-curable adhesive layer composition, etc. Examples of the thermosetting adhesive layer composition include a composition containing a hydroxyl group-containing (meth)acrylic polymer and a difunctional or higher isocyanate compound (hereinafter also referred to as a "polyfunctional isocyanate compound"), as described in WO 2016/125796.

In one embodiment, from the viewpoints of heat resistance sufficient to withstand use in a transfer molding process in which the mold and sealing resin are exposed to high temperatures, and compatibility with the antistatic layer, it is preferable that the adhesive layer contains a reaction-cured product of a hydroxyl group-containing (meth)acrylic polymer and a polyfunctional isocyanate compound. In this case, the hydroxyl group-containing (meth)acrylic polymer reacts with the polyfunctional isocyanate compound to crosslink and become a reaction-cured product. The adhesive layer of this embodiment may also contain a reaction-cured product of a hydroxyl group-containing (meth)acrylic polymer, a polyfunctional isocyanate compound, and other components.

The thickness of the adhesive layer is preferably 0.05 to 3.0 μm, more preferably 0.05 to 2.5 μm, and even more preferably 0.05 to 2.0 μm. When the thickness of the adhesive layer is equal to or greater than the lower limit, the adhesiveness is excellent. When the thickness of the adhesive layer is equal to or less than the upper limit, the function of the antistatic layer is fully exerted, and the surface resistivity of the adhesive layer side of the film is low.

(Other layers)
The film may or may not have layers other than the substrate, the antistatic layer, and the adhesive layer. Examples of the other layers include a gas barrier layer, a colored layer, etc. These layers may be used alone or in combination of two or more.

(Film manufacturing method)
The present film is produced, for example, by the following method.
A layer of the composition for the antistatic layer is formed on one side of the substrate, and the composition for the antistatic layer is cured to form an antistatic layer. If necessary, an adhesive layer or other optional layer may be formed. When an optional layer is formed on the side of the antistatic layer opposite the substrate, the composition for the optional layer may be applied before curing the composition for the antistatic layer, and the curing of the composition for the antistatic layer and the curing of the composition for the optional layer may be performed simultaneously.

The layer of the antistatic layer composition can be formed, for example, by preparing a coating liquid for the antistatic layer containing the above-mentioned composition for the antistatic layer and a liquid medium, applying the coating liquid for the antistatic layer onto one side of the substrate, and drying the coating liquid. Note that the composition for the antistatic layer does not contain a liquid medium.

Examples of the liquid medium include general organic solvents, such as ketones, esters, hydrocarbons, alcohols, glycols, glycol ethers, etc. It is preferable to select a liquid medium that has excellent solubility for the specific urethane (meth)acrylate, antistatic agent, etc. contained in the composition for the antistatic layer.
The content of the liquid medium is set according to the solid content of the coating liquid for the antistatic layer.
The solid content concentration of the coating liquid for the antistatic layer is preferably from 1 to 30% by mass, more preferably from 1 to 10% by mass, and even more preferably from 1 to 5% by mass.

When the antistatic layer composition contains a surface modifier, the liquid medium preferably contains a liquid medium having a boiling point of 80° C. or more (hereinafter also referred to as a "high boiling point medium") from the viewpoint of easily distributing the surface modifier on the surface side of the layer. The boiling point of the high boiling point medium is preferably 100° C. or more, and from the viewpoint of reducing the drying load, it is preferably 250° C. or less. Specific examples of the high boiling point medium include propylene glycol monomethyl ether (boiling point 121° C.), cyclopentanone (boiling point 131° C.), propylene glycol monomethyl ether acetate (boiling point 146.4° C.), cyclohexanone (boiling point 155.6° C.), and N-methyl-2-pyrrolidone (boiling point 202° C.).
The content of the high-boiling point medium is preferably from 1 to 30% by mass, more preferably from 5 to 20% by mass, based on the total amount of the liquid medium.

As a method for applying the coating liquid for the antistatic layer, a known coating method can be applied, and examples thereof include spin coating, spray coating, inkjet coating, bar coating, knife coating, roll coating, blade coating, die coating, gravure coating, microgravure coating, comma coating, slot die coating, lip coating, and solution casting.
The drying method may be any known method capable of removing the liquid medium.
When the composition for the antistatic layer contains a surface modifier, in order to easily distribute the surface modifier unevenly on the surface side of the layer, the coating liquid for the antistatic layer may be left in an atmosphere below the boiling point of the liquid medium after application and before drying. The leaving time is, for example, 0.1 to 10 minutes.

Methods for curing the composition for the antistatic layer include irradiation with active energy rays (active energy ray curing), heating (thermal curing), and the like, and irradiation with active energy rays is preferred from the viewpoint of a fast curing rate.
Examples of the active energy ray include ultraviolet rays, electron beams, etc. From the viewpoint of suppressing damage to the coating film caused by the active energy ray, ultraviolet rays are preferred.
When ultraviolet irradiation is selected, it is preferable to select a combination that maximizes the overlap between the emission spectrum of the ultraviolet light source and the absorption spectrum of the polymerization initiator. The ultraviolet light source can be selected from light sources such as a high-pressure mercury lamp, an H bulb, a D bulb, and a V bulb.
The irradiation amount (accumulated light amount) of the active energy rays is preferably from 100 to 3,000 mJ/□, and more preferably from 500 to 2,000 mJ/□.
The irradiation with active energy rays is preferably carried out in an inert gas atmosphere such as nitrogen in order to suppress reaction inhibition by oxygen in the air in radical reactions and promote the curing reaction.
When irradiating with active energy rays, heating may be performed to promote curing.

(Surface resistivity of film)
The surface resistivity of the present film is not particularly limited, and may be 10 ¹⁷ Ω/□ or less, preferably 10 ¹¹ Ω/□ or less, more preferably 10 ¹⁰ Ω/□ or less, and even more preferably 10 ⁹ Ω/□ or less. The lower limit of the surface resistivity is not particularly limited.
The surface resistivity of the film is measured in accordance with IEC 60093:1980: double ring electrode method, at an applied voltage of 500 V for 1 minute. As a measuring device, for example, an ultra-high resistance meter R8340 (Advantec) can be used.

(Film Uses)
The present film is useful, for example, as a release film used in various processes such as a process of sealing a semiconductor element with a curable resin, and as a surface protection film for a semiconductor element, a solar cell module, etc. In particular, the present film is useful as a release film used in a process of sealing a semiconductor element with a curable resin, and is particularly useful as a release film used in a process of producing a semiconductor package having a complex shape, for example, a sealed body in which a part of an electronic component is exposed from the resin.

[Method of manufacturing semiconductor package]
In one aspect, a method for manufacturing a semiconductor package includes:
disposing the film on an inner surface of a mold;
placing a substrate having a semiconductor element fixed thereto in the mold in which the film is placed;
encapsulating the semiconductor element in the mold with a curable resin to produce an encapsulated body;
Releasing the encapsulated body from the mold; and
including.

Examples of the semiconductor package include an integrated circuit in which semiconductor elements such as transistors and diodes are integrated; a light-emitting diode having a light-emitting element; and the like.
The package shape of the integrated circuit may be one that covers the entire integrated circuit, or one that covers only a portion of the integrated circuit, i.e., one that exposes a portion of the integrated circuit. Specific examples include SIP (Single In-line Package), ZIP (Zigzag In-line Package), DIP (Dual In-line Package), SOJ (Small Outline J-leaded package), SON (Small Outline Non-leaded package), SOI (Small Outline I-leaded package), SOF (Small Outline F-leaded package), QFP (Quad Flat Package), QFJ (Quad Flat J-leaded package), QFN (Quad Flat Non-leaded package), QFF (Quad Flat F-leaded package), PGA (Pin Grid Array), LGA (Land Grid Array), BGA (Ball Grid Array), DTP (Dual Tape carrier Package), QTP (Quad Tape carrier Package), CSP (Chip Size Package/Chip Scale Package), WL-CSP (Wafer Level CSP), LLP (Leadless Lead frame Package), DFN (Dual Flatpack No-leaded), MCP (Multiple Flat Packs), and the like. Chip Package), MCM (Multi Chip Module), SiP (System in a Package), PoP (Package on a Package), PiP (Package in a Package), QIP (or QUIP) (Quad In-line Package), CFP (Ceramic Flat Package), LLCC (Lead Less Chip Carrier), FOWLP (Fan Out Wafer Level Package), COB (Chip On Board), COF (Chip On Film), COG (Chip On Glass), SVP (Surface Vertical Package), etc.
From the viewpoint of productivity, the semiconductor package is preferably one that is manufactured through collective sealing and singulation, and examples of the semiconductor package include integrated circuits sealed by the Molded Array Packaging (MAP) method or the Wafer Level Packaging (WL) method.

As the curable resin, thermosetting resins such as epoxy resins and silicone resins are preferred, and epoxy resins are more preferred.

In one aspect, the semiconductor package may or may not have electronic components such as a source electrode and sealing glass in addition to the semiconductor element. Also, some of the electronic components such as the semiconductor element, source electrode, and sealing glass may be exposed from the resin.

The manufacturing method for the semiconductor package can be a known manufacturing method, except for using this film. For example, a method for sealing a semiconductor element can be a transfer molding method, and a known transfer molding device can be used as the device used for this. The manufacturing conditions can also be the same as those in known manufacturing methods for semiconductor packages.

Next, the embodiments of the present disclosure will be specifically described using examples, but the embodiments of the present disclosure are not limited to these examples. In the following examples, Examples 1 to 7 are examples, and Examples 8 to 11 are comparative examples. "Parts" means "parts by mass."

(Evaluation method)
<Surface resistivity>
The surface resistivity (Ω/□) of the film on the side opposite to the substrate was measured according to the double ring electrode method of IEC 60093:1980. The measurement was performed using an ultra-high resistance meter R8340 (Advantec) at an applied voltage of 500 V for 1 minute.

<Defects during stretching>
The film was cut into a strip (50 mm wide, 100 mm long). This film was clamped and set between the grips of a tensile tester (RTC-131-A manufactured by Orientec Co., Ltd.). The film was stretched until the elongation rate reached 200%, with a grip distance of 10 mm before tension and a speed of 100 mm/min. The elongation rate is the ratio of the grip distance during tension to the grip distance before tension. The film was then removed from the grips and observed under an optical microscope (magnification 20x) and evaluated according to the following criteria.
A: There were no cracks or voids.
B: There were no cracks, but there were voids.
C: There were no voids, but there were cracks.
D: There were cracks and voids.

(Materials used)
<Substrate>
ETFE film: Fluon (registered trademark) ETFE C-88AXP (manufactured by AGC) was fed into an extruder equipped with a T-die, and taken up between a pressing roll with an uneven surface and a metal roll with a mirror surface to form a film with a thickness of 100 μm. The temperature of the extruder and the T-die was 320° C., and the temperature of the pressing roll and the metal roll was 100° C. The Ra of the surface of the obtained film was 2.0 μm on the pressing roll side and 0.2 μm on the mirror side. The mirror side was subjected to a corona treatment so that the wetting tension based on ISO8296:1987 (JIS K6768:1999) was 40 mN/m or more.

<Materials for Antistatic Layer>
Bifunctional UA-1: UA-W2A (manufactured by Shin-Nakamura Chemical Co., Ltd.), polyether-based bifunctional urethane acrylate, (meth)acryloyl group equivalent 1,750 g/eq.
Bifunctional UA-2: UF-3003 (manufactured by Kyoeisha Chemical Co., Ltd.), polyester-based bifunctional urethane acrylate, (meth)acryloyl group equivalent 7,500 g/eq.
Bifunctional UA-3: UF-3003M (manufactured by Kyoeisha Chemical Co., Ltd.), polyester-based bifunctional urethane acrylate, (meth)acryloyl group equivalent 10,000 g/eq.
Hexafunctional UA: U-6LPA (manufactured by Shin-Nakamura Chemical Co., Ltd.), a hexafunctional urethane acrylate, (meth)acryloyl group equivalent 142 g/eq.
Trifunctional acrylate: A-TMPT (manufactured by Shin-Nakamura Chemical Co., Ltd.), trimethylolpropane triacrylate, (meth)acryloyl group equivalent 99 g/eq.
Monofunctional acrylate: AM-230 (manufactured by Shin-Nakamura Chemical Co., Ltd.), methoxypolyethylene glycol #1000 acrylate, (meth)acryloyl group equivalent 1098 g/eq.
Conductive polymer: SEPLEGYDA (registered trademark) SAS-F16 (manufactured by Shin-Etsu Polymer Co., Ltd.), conductive polymer having a polythiophene skeleton (PEDOT-PSS), methyl ethyl ketone (MEK) dispersion, solid content 2% by mass.
Conductive filler: V-3561 (manufactured by JGC Catalysts and Chemicals), chain ATO (structure in which 10 or more ATO particles are connected, aspect ratio of 10 or more), propylene glycol monomethyl ether (PGME) dispersion, solid content 20.4 mass %.
Photopolymerization initiator: Omnirad 184 (manufactured by IGM Resins BV), 1-hydroxycyclohexyl phenyl ketone.
Surface modifier: BYK-UV3505 (manufactured by BYK Corporation), a silicone-based surface modifier whose main component is modified polydimethylsiloxane having an acryloyl group, solid content 100% by mass.

Base component 1: ALACOAT (registered trademark) AS601D (manufactured by Arakawa Chemical Industries, Ltd.), solid content 3.4 mass %, conductive polythiophene 0.4 mass %, carboxy group-containing (meth)acrylic polymer 3.0 mass %.
Curing agent 1: ARAQUAT CL910 (manufactured by Arakawa Chemical Industries, Ltd.), solid content 10 mass %, trifunctional aziridine compound (2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate], aziridine equivalent 142 g/eq.

<Material for adhesive layer>
Base agent 2: Nissetsu (registered trademark) KP2562 (manufactured by Nippon Carbide Industries Co., Ltd.), solid content 35% by mass, hydroxyl group-containing (meth)acrylic polymer.
Curing agent 2: Nissetsu CK157 (manufactured by Nippon Carbide Industries Co., Ltd.), solid content 100 mass%, bifunctional isocyanate compound (isocyanurate-type hexamentylene diisocyanate), NCO content 21 mass%.

(Examples 1 to 6, 8 to 10)
The coating liquid for the antistatic layer was prepared by mixing the binder, the antistatic agent, other additives, the photopolymerization initiator, and the liquid medium (only cyclohexanone when the antistatic agent is a conductive polymer, and a mixed medium of PGME/cyclohexanone = 9/1 (mass ratio) when the antistatic agent is a conductive filler). The material types and amounts of the binder, the antistatic agent, and the other additives are shown in Table 1. The amounts shown in Table 1 are the ratios of each component to the total of the binder, the antistatic agent, and the other additives (solid content conversion). The amount of the photopolymerization initiator was 4 mass% relative to the binder. The amount of the liquid medium was an amount such that the solid content of the coating liquid for the antistatic layer was 3.7 mass%.
The obtained coating liquid for antistatic layer was applied to the surface of the substrate on the side that had been subjected to the corona treatment using a wire bar #8, and dried for 1 minute in an oven at 55° C. Thereafter, the coating liquid was cured by irradiating ultraviolet rays (UV) using an H-bulb UV lamp under a nitrogen gas atmosphere so that the integrated light amount was 1,500 mJ/□, forming an antistatic layer having a thickness of 0.3 μm, and a film was obtained.

The cross section of the film of Example 6 was observed with a scanning electron microscope (SEM) while undergoing elemental analysis by EDX. Silicon, an element specific to the surface modifier, was detected unevenly on the surface and near the surface, confirming that the surface modifier is unevenly distributed on the surface side of the antistatic layer.

(Example 7)
In the same manner as in Example 3, an antistatic layer was formed on the substrate.
Next, 100 parts of the base agent 2, 6 parts of the curing agent 2, and ethyl acetate were mixed to prepare a coating liquid for adhesive layer. The amount of ethyl acetate was set to an amount such that the solid content of the coating liquid for adhesive layer was 25 mass%.
The obtained adhesive layer coating liquid was applied to the surface of the substrate on which the antistatic layer was formed using a gravure coater, and then dried (thermosetting) to form an adhesive layer having a thickness of 0.8 μm, to obtain a film. Coating was performed by a direct gravure method using a Φ100 mm×250 mm width lattice 150#-depth 40 μm roll as a gravure plate. Drying was performed at 100° C. for 1 minute through a roll support drying oven with an air volume of 19 m/sec. Thereafter, the film was aged at 40° C. for 2 days to obtain a film.

(Example 11)
An antistatic layer coating liquid was prepared by mixing 10 parts of the base agent 1, 1 part of the curing agent 1, and methanol. The amount of methanol was set to an amount such that the solid content of the antistatic layer coating liquid was 2% by mass.
The obtained coating liquid for the antistatic layer was applied to the surface of the substrate on the corona-treated side using a gravure coater, and then dried (thermosetting) to form an antistatic layer having a thickness of 0.1 μm. Coating was performed by a direct gravure method using a Φ100 mm×250 mm width lattice 150#-depth 40 μm roll as a gravure plate. Drying was performed at 100° C. for 1 minute through a roll-supported drying oven with an air flow rate of 19 m/sec.

Next, 100 parts of the base agent 2, 4 parts of the curing agent 2, and ethyl acetate were mixed to prepare a coating liquid for adhesive layer. The amount of ethyl acetate was set to an amount such that the solid content of the coating liquid for adhesive layer was 25% by mass.
The obtained adhesive layer coating liquid was applied to the surface of the substrate on the side on which the antistatic layer was formed using a gravure coater, and then dried (thermosetting) to form an adhesive layer having a thickness of 2 μm. Coating was performed by a direct gravure method using a Φ100 mm×250 mm width lattice 150#-depth 40 μm roll as a gravure plate. Drying was performed at 100° C. for 1 minute through a roll support drying oven with an air volume of 19 m/sec. Thereafter, the film was aged at 40° C. for 120 hours to obtain a film.

The surface resistivity of the obtained film and the results of defects during stretching are shown in Table 1. In Table 1, "10^n" for the surface resistivity indicates 10 ⁿ . For example, "10^10" indicates 10 ¹⁰ .

The films of Examples 1 to 7 had sufficient antistatic properties, and no cracks or voids were generated during stretching.
On the other hand, after stretching, numerous cracks extending in a direction perpendicular to the stretching direction were observed in Examples 8, 10, and 11. In Example 9, no cracks or voids were generated, but the film did not have antistatic properties because the antistatic layer did not contain an antistatic agent.

The film of the present disclosure has sufficient antistatic properties and is less likely to crack or void when stretched. The film of the present disclosure can be used as a release film to manufacture semiconductor packages such as integrated circuits that integrate semiconductor elements such as transistors and diodes, source electrodes, sealing glass, and other electronic components. The film of the present disclosure can also be used as a protective film when processing, transporting, and storing semiconductor elements, solar cell modules, etc.

Although various embodiments have been described above, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure. Furthermore, the components in the above embodiments may be combined in any manner as long as it does not deviate from the spirit of the invention.

This application is based on a Japanese patent application (Patent Application No. 2022-178344) filed on November 7, 2022, the contents of which are incorporated by reference into this application.

REFERENCE SIGNS LIST 1 Laminate 2 Substrate 3 Antistatic layer 4 Adhesive layer

Claims (15)

1. A film comprising a substrate and an antistatic layer,
   The film, wherein the antistatic layer is a layer made of a cured product of a composition containing a urethane (meth)acrylate having one or more (meth)acryloyl groups and one or more urethane bonds and having a (meth)acryloyl group equivalent of 1,000 g/eq or more, an antistatic agent, and a polymerization initiator.
2. The film of claim 1, wherein the urethane (meth)acrylate comprises a multifunctional urethane (meth)acrylate having two or more (meth)acryloyl groups.
3. The film according to claim 1 or 2, wherein the urethane (meth)acrylate has at least one structure selected from the group consisting of a polyether structure, a polyester structure, and a polycarbonate structure.
4. The film according to claim 1 or 2, wherein the composition contains a multifunctional (meth)acrylate other than the urethane (meth)acrylate.
5. The film according to claim 1 or 2, wherein the substrate comprises at least one selected from the group consisting of fluororesin, polymethylpentene, syndiotactic polystyrene, polycycloolefin, silicone rubber, polyester elastomer, polybutylene terephthalate, polyethylene terephthalate, and polyamide.
6. The film according to claim 5, wherein the fluororesin comprises at least one selected from the group consisting of ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer, and tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer.
7. The film of claim 1 or 2, wherein the antistatic agent comprises a conductive polymer.
8. The film according to claim 1 or 2, wherein the antistatic agent comprises a conductive filler.
9. The film according to claim 1 or 2, wherein the polymerization initiator is a photopolymerization initiator.
10. The film of claim 1 or 2, wherein the composition further comprises a surface modifier.
11. The film of claim 1 or 2, further comprising an adhesive layer.
12. The film according to claim 1 or 2, which is a release film.
13. The film according to claim 1 or 2, which is a release film used in a process for sealing a semiconductor element with a curable resin.
14. Placing the film according to claim 1 or 2 on an inner surface of a mold;
    placing a substrate having a semiconductor element fixed thereto within the die in which the film is placed;
    encapsulating the semiconductor element in the mold with a curable resin to produce an encapsulated body;
    and releasing the sealing body from the mold.
15. Placing the film according to claim 11 on an inner surface of a mold;
    placing a substrate having a semiconductor element fixed thereto within the die in which the film is placed;
    encapsulating the semiconductor element in the mold with a curable resin to produce an encapsulated body;
    and releasing the sealing body from the mold.

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