MOLD RELEASE FILM

Abstract

The object of the present invention is to provide a mold release film that does not contaminate the mold or the formed body. This invention provides a mold release film comprising a base material layer formed from a thermoplastic resin, and a surface layer formed from a resin composition layered on at least one surface of the base material layer. The mold release film has a trouser tear strength, according to JIS K 7128-1, of 5 N / mm or stronger. The resin composition has a peel strength of 15 mN / 30 mm or weaker, as measured at 175°C according to JIS Z0237. The resin composition has an elongation at break of 70% or greater, as measured at 175°C according to JIS K 7127.

Description

The present invention relates to a release film, and more particularly to a release film used to seal a semiconductor element with a resin in the inverted chip connection. Background Technique In recent years, in response to the increased functionality of electronic devices and their expansion into mobile applications, there has been a growing demand for higher density and greater integration of semiconductor devices, and the capacity and density of semiconductor packages have also increased. To further enhance speed and functionality, it is necessary to rapidly transmit many signals, and the connection method between the semiconductor element and the package substrate is shifting from conventional wire-bonding to inverted chip connections. These inverted chip connections achieve direct connection via solder protrusions (connecting electrodes), which can increase the number of pins and improve speed.Furthermore, to improve information processing capacity, wiring for semiconductor packages is becoming increasingly wider, with the distance between solder protrusions and the height of the protrusions themselves decreasing, and smaller gaps and clearances becoming more common. In inverted chip connections, it is common to seal the gap between the semiconductor element and the package substrate with a resin composition to reinforce the joint and improve reliability. As a method for sealing with a resin composition, a capillary subfill mode is generally adopted. This method is carried out by applying a liquid sealing resin composition to one or more surfaces of a semiconductor element and allowing the resin composition to flow into a space between a package substrate and a semiconductor element by utilizing capillary action. In order to reduce assembly costs and the number of processes in recent years, a mold underfilling method (Molded Underfill; MUF) has been developed in which sealing is performed in a state where the release film and the semiconductor element are in direct contact with each other, in order to protect and mask the semiconductor element (Patent Literature 1), as a method for sealing with a resin composition. List of References Patent Literature Patent Literature 1: Publication of Application Japanese Unexamined Patent (JP-A) No. 2013-123063 Brief Description of the Invention Technical Problem However, the sealing resin used in the mold underfilling mode has extremely high viscosity in order to improve the filling property for a small space, and the mold needs to be washed frequently, which decreases production efficiency, and at the same time, it becomes necessary to buy many devices. When a release film is subjected to high temperature in a mold, the components contained in the release film can move to the surface of the release film, and the components that move to the surface can contaminate the mold or a molded article of a sealing resin (hereafter referred to as a molded article). When such contamination occurs, the components must be removed from a mold or molded item. Furthermore, the components are often difficult to remove. Therefore, it is desirable to prevent contamination of a mold or molded item with these components. A release film that is not only usable in molding once but also repeatedly usable in multiple moldings can reduce molding costs. In order to repeatedly use a release film in multiple molding operations, the release film is required to maintain its properties through multiple molding operations. In view of the foregoing circumstances, the present invention is proposed to provide a release film that does not contaminate a mold or a molded article. The present invention is also proposed to provide a release film that does not contaminate a mold or a molded article and can be used repeatedly in multiple molding processes. Solution to the Problem The inventors of the present invention have found that a release film having a specific configuration has excellent mold release properties, for example, mold release properties for a sealing resin used in inverted chip bonding, and has low contamination properties. The inventors of the present invention have further found that the release film can be used in multiple molding cycles. That is, the present invention provides a release film having a base layer formed of a thermoplastic resin and a surface layer formed of a resin composition laminated on at least one surface of the base layer, wherein the tear strength of the trousers according to JIS K7128-1 is 5 N / mm or more, the peel strength of the resin composition is 15 mN / 30 mm or less when measured at 175°C according to JIS Z0237, and the elongation at break of the resin composition is 70% or more when measured at 175°C according to JIS K7127. The resin composition may be a fluororesin. The resin composition may contain an isocyanate curing agent. The resin composition may contain a tetrafluoroethylene resin. The release film can be used in sealing a semiconductor to be connected with an inverted chip. The release film can be used for molding two or more times. Advantageous Effects of the Invention The present invention provides a release film that has excellent release properties and low contamination. Furthermore, the release film of the present invention can be used repeatedly for multiple molds. The effect of the present invention is not necessarily limited to the effect described herein, and may be any effect described in this specification. Brief Description of the Drawings [Fig. 1] FIG. 1 is a view showing an example structure of a release film of the present invention. [Fig. 2] FIG. 2 shows an example use of a release film of the present invention in transfer molding. Description of Modalities The embodiments of the present invention will now be described in detail. The embodiments described below are merely examples of typical embodiments of the present invention, and the present invention is not limited to these embodiments. : Release film A release film of the present invention includes a base layer formed from a thermoplastic resin and a surface layer formed from a resin composition laminated to at least one surface of the base layer. The surface layer can be laminated to both surfaces of the base layer. An example structure of the release film of the present invention is shown in Fig. 1. As shown in Fig. 1, a release film 100 of the present invention comprises a base layer 101 and surface layers 102 and 103 laminated to both faces of the base layer. The base layer 101 is formed from a thermoplastic resin. The two surface layers 102 and 103 are formed from a resin composition. The two surface layers 102 and 103 can be formed from the same resin composition or from different resin compositions. The release film of the present invention includes the base layer and the surface layers formed on both surfaces of the base layer, thereby providing excellent mold release properties and low contamination properties in a mold and / or a molded article during molding. Furthermore, the release film of the present invention can be used to carry out a molding process multiple times. The release film of the present invention will then be described in more detail. [Base layer] The base layer is made of a thermoplastic resin. This thermoplastic resin can be, for example, a polyester-based resin, a polyolefin-based resin, a polyamide-based resin, or a polyvinyl chloride-based resin. In particular, a polyester-based resin is preferred due to its ease of resin removal from the inverted chip seal and its flowability in the mold. The polyester-based resin described above is a polymer that has an ester linkage in the main chain. The polyester-based resin may be, for example, a polymer composed of a polyhydric alcohol and a polybasic acid. The polyester resin may be a single resin or a combination composed of two or more selected from the group consisting of, for example, polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polyethylene naphthalate (PEN) resin, polybutylene naphthalate (PBN) resin, and polycarbonate (PC) resin. The polyester-based resin is a resin that contains polyester as a principal component, and, for example, the proportion of polyester to the mass of the resin may preferably be 90% by mass or more, more preferably 95% by mass or more, and more preferably 98% by mass or more. The polyester-based resin is preferably a PET resin, and more preferably an easily moldable polyethylene terephthalate (PET) resin. The easily moldable polyethylene terephthalate resin has better moldability than a general-purpose polyethylene terephthalate resin. The base layer formed from the easily moldable polyethylene terephthalate resin particularly contributes to making the release film of the present invention have low contamination properties. Easily moldable polyethylene terephthalate resin can be, for example, a copolymerized polyethylene terephthalate resin. Copolymerized polyethylene terephthalate can be obtained, for example, by reacting terephthalic acid with ethylene glycol and a copolymerizing agent, or it can be obtained by mixing and melting the polymer of the copolymerizing agent and polyethylene terephthalate and then performing a distribution reaction. The copolymerization component can be, for example, an acid component or an alcohol component. Examples of acid components include aromatic dibasic acids (e.g., isophthalic acid, italic acid, naphthalenedicarboxylic acid, etc.), aliphatic dicarboxylic acids (e.g., adipic acid, azelaic acid, sebacic acid, decandicarboxylic acid, etc.), and alicyclic dicarboxylic acids (e.g., cyclohexanedicarboxylic acid, etc.). Examples of alcohol components include aliphatic diols (e.g., butanediol, hexanediol, neopentyl glycol, hexanediol, etc.) and alicyclic diols (e.g., cyclohexanedimethanol, etc.). Like the copolymerization component, these compounds can be used individually or in combination with other compounds. The acid component specifically can be isophthalic acid and / or sebacic acid. A commercially available material can be used as the base layer formed from the easily moldable polyethylene terephthalate resin used in the present invention. For example, the following can be used as the base layer: Teflex (registered trademark) FT, Teflex (registered trademark) FT3, and Teflex (registered trademark) FW2 (all manufactured by Teijin Film Solution Co. , Ltd.). Additionally, as the base layer, Emblet (registered trademark) CTK-38 (manufactured by Unitika Ltd.) can be used. The base layer formed from the easily moldable polyethylene terephthalate resin can be produced by a method described, for example, in JP-A No. Hei-2-305827, JP-A No. Hei-3-86729, or JP-A No. Hei-3-110124. According to a preferred embodiment of the present invention, the base layer can be obtained by biaxially stretching an easily moldable polyethylene terephthalate resin such that a plane orientation coefficient is preferably 0.06 to 0.16, more preferably 0.07 to 0.15, as described in any of these publications. The glass transition temperature of the easily moldable polyethylene terephthalate resin can preferably be 60°C to 95°C, and more preferably 65°C to 90°C. The easily moldable polyethylene terephthalate resin having a glass transition temperature within the above numerical range contributes to making the release film of the present invention usable in multiple molding cycles. Ordinary polyethylene terephthalate generally has a glass transition temperature of 100°C or higher. Preferably 98% by mass or more with respect to the mass of the resin. The polyamide may be, for example, an aliphatic polyamide, and more specifically, it may be polyamide 6, polyamide 6 / 6, polyamide 6 / 10, polyamide 11, polyamide 12, or polyamide 6 / 12. Polyvinyl chloride-based resin is a resin containing polyvinyl chloride as a major component, and may, for example, contain polyvinyl chloride in a proportion of preferably 90% by mass or more, more preferably 95% by mass or more, and more preferably 98% by mass or more with respect to the mass of the resin. The polyvinyl chloride may be, for example, a vinyl chloride homopolymer or a copolymer of vinyl chloride and a comonomer. The comonomer may be, for example, vinyl acetate or ethylene. The tensile strength of the base layer may preferably be 40 MPa to 200 MPa, more preferably 40 MPa to 120 MPa, more preferably 40 MPa to 110 MPa, and still more preferably 45 MPa to 100 MPa when measured at 175°C according to JIS K7127. The tensile elongation of the base layer can preferably be 200% to 500%, more preferably 250% to 450%, and further preferably 300% to 400% when measured at 175°C in accordance with JIS K7127. The base layer having a tensile strength and / or tensile elongation within the numerical range contributes to making the release film of the present invention usable in multiple molding cycles. The thickness of the base layer can be, for example, preferably 10 µm to 80 µm, more preferably 15 µm to 75 µm, and preferably 20 µm to 70 µm. This thickness contributes to enabling the release film of the present invention to be used in a plurality of molds. [Surface layer] The surface layer constituting the release film of the present invention is formed from a resin composition. The resin composition may be, for example, a fluororesin, an acrylic-based resin, or similar materials. Among these, a surface layer formed from a fluororesin is preferable because it exhibits good release properties while maintaining sufficient heat resistance. According to a preferred embodiment of the present invention, the fluororesin is chlorine-free. The fluororesin preferably contains a tetrafluoroethylene resin, and more preferably contains a tetrafluoroethylene resin as a major component. The fact that the tetrafluoroethylene resin is the major component means that the fluororesin consists solely of the tetrafluoroethylene resin, or that the amount of tetrafluoroethylene resin among the components contained in the fluororesin is greater. The fluororesin may be, for example, a cured product of a fluororesin composition containing a fluoropolymer with a reactive functional group and a curing agent. The fluoropolymer containing the reactive functional group in the fluororesin composition can be a fluoropolymer that can be cured by a curing agent. The reactive functional group and the curing agent can be appropriately selected by those skilled in the art. The reactive functional group can be, for example, a hydroxyl group, a carboxyl group, a group represented by -COOCO-, an amino group, or a silyl group, and a hydroxyl group is preferred. With these groups, the reaction to obtain the cured product proceeds well. Of these reactive functional groups, the hydroxyl group is particularly suitable for the reaction to obtain the cured product. That is, the fluoropolymer containing the reactive functional group is preferably a fluoropolymer containing a hydroxyl group, and more preferably a tetrafluoroethylene-based polymer containing a hydroxyl group. The fluorine-containing unit of the fluoropolymer containing the reactive functional group is preferably a fluorine-containing unit based on a perfluoroolefin. Fluorine-containing units based on perfluoroolefins with more than > you NCNN preference may be based on one, two, or three selected from tetrafluoroethylene (hereafter also referred to as TFE in this specification), hexafluoropropylene (HFP), and perfluoro(alkyl vinyl ether) (PAVE). Preferably, among the perfluoroolefin-based fluorine-containing units, the amount of one TFE-based fluorine-containing unit is the largest. The hydroxyl value of the fluoropolymer containing the reactive functional group (particularly the hydroxyl value of the fluoropolymer containing the hydroxyl group) may preferably be 10 mgKOH / g to 300 mgKOH / g, more preferably 10 mgKOH / g to 200 mgKOH / g, and further preferably 10 mgKOH / g to 150 mgKOH / g. When the hydroxyl value of the fluoropolymer containing the reactive functional group is at least the lower limit of the above numerical range, the curability of the resin composition can be improved. Furthermore, if the hydroxyl value of the fluoropolymer containing the reactive functional group is no more than the upper limit of the above numerical range, the curable product of the resin composition is suitable for multiple molding. The hydroxyl value is obtained by measuring using a method in accordance with JIS K0070. The acidity of the fluoropolymer containing the reactive functional group (particularly the acidity of the fluoropolymer containing the hydroxyl group) can preferably be 0.5 mgKOH / g to 100 mgKOH / g, and more preferably 0.5 mgKOH / g to 50 mgKOH / g. When the acidity of the fluoropolymer containing the reactive functional group is at least at the lower limit of the above numerical range, the curability of the resin composition can be improved. Furthermore, ensuring that the acidity of the fluoropolymer containing the reactive functional group is not above the upper limit of the above numerical range contributes to making the cured resin composition suitable for a variety of molds. The reactive functional group of the fluoropolymer can be introduced by copolymerizing a monomer with a fluorine-containing monomer (particularly a perfluoroolefin). In other words, the fluoropolymer can contain one polymerization unit based on the monomer with the reactive functional group and one polymerization unit based on the fluorine-containing monomer (particularly a perfluoroolefin). When the reactive functional group is a hydroxyl group, the monomer that has the reactive functional group can preferably be a vinyl ether containing a hydroxyl group or an allylic ether containing a hydroxyl group. Examples of vinyl ethers containing a hydroxyl group include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxy-2-methylbutyl vinyl ether, o-hydroxypentyl vinyl ether, and 6-hydroxyhexyl vinyl ether. Examples of allyl ethers containing a hydroxyl group include 2-hydroxyethyl allyl ether, 4-hydroxybutyl allyl ether, and monoallyl glycerol ether. Alternatively, the monomer bearing the reactive functional group may be, for example, a hydroxyalkyl ester of (meth)acrylic acid such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate. As the monomer that has the reactive functional group, one or a combination of two or more of these compounds can be used.When the reactive functional group is a hydroxyl group, the monomer that has the reactive functional group is most preferably a vinyl ether containing a hydroxyl group, and particularly preferably 4-hydroxybutyl vinyl ether and / or 2-hydroxyethyl vinyl ether, from the point of view of resin composition curability. When the reactive functional group is a carboxyl group, the monomer that has the reactive functional group can preferably be an unsaturated carboxylic acid, an ester of an unsaturated carboxylic acid, or an acid anhydride of an unsaturated carboxylic acid. When the reactive functional group is an amino group, the monomer that has the reactive functional group can be, for example, aminovinyl ether or allylamine. When the reactive functional group is a silicon group, the monomer that has the reactive functional group can preferably be a silicone-based vinyl monomer. The fluorine-containing monomer is preferably a perfluoroolefin. Examples of perfluoroolefins include tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and perfluoro(alkyl vinyl ether) (PAVE). Preferably, the fluorine-containing monomer contains TFE. Preferably, the fluoropolymer containing the reactive functional group may contain a polymerization unit based on a fluorine-free vinyl monomer, in addition to a polymerization unit based on the monomer containing the reactive functional group and a polymerization unit based on the monomer containing fluorine. The fluorine-free vinyl monomer may be, for example, one or a combination of two or more selected from the group consisting of vinyl carboxylic acid esters, vinyl alkyl ethers, and non-fluorinated olefins. Examples of vinyl esters of carboxylic acids include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caproate, vinyl versatate, vinyl laurate, vinyl stearate, vinyl cyclohexylcarboxylate, vinyl benzoate, and vinyl pt-butylbenzoate. Examples of alkyl vinyl ethers may include vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, and vinyl cyclohexyl ether. Examples of non-fluorinated olefins include ethylene, propylene, n-butene, and isobutene. Furthermore, the fluoropolymer containing a reactive functional group may contain, in addition to the polymerization unit based on a monomer containing a reactive functional group and the polymerization unit based on a monomer containing fluorine such as a perfluoroolefin, a polymerization unit based on a fluoromonomer other than a perfluoroolefin, such as vinylidene fluoride (VdF), chlorotrifluoroethylene (CTFE), vinyl fluoride (VF), and fluorovinyl ether. The fluoropolymer containing the reactive functional group can be, for example, a TFE-based copolymer / non-fluorinated olefin / butyl hydroxyvinyl ether, a TFE-based copolymer / carboxylic acid vinyl ester / butyl hydroxyvinyl ether, or a TFE-based copolymer / alkyl vinyl ether / butyl hydroxyvinyl ether. More specifically, the fluoropolymer containing the reactive functional group may be a TFE / isobutylene / vinyl hydroxyethyl ether copolymer, a TFE / vinyl versatate / vinyl hydroxyethyl ether copolymer, or a TFE / VdF / vinyl hydroxyethyl ether copolymer. The fluoropolymer containing the particularly reactive functional group may preferably be a TFE / isobutylene / vinyl hydroxyethyl ether copolymer or a TFE / vinyl versatate / vinyl hydroxyethyl ether copolymer. Products such as the Zeffle GK series can be used, for example, as a fluoropolymer containing a reactive functional group. The curing agent contained in the fluororesin composition can be appropriately selected by those skilled in the technique depending on the type of reactive functional group contained in the fluoropolymer containing the reactive functional group. When the reactive functional group is a hydroxyl group, the preferred curing agent may be one or a combination of two or more selected from an isocyanate curing agent, a melamine resin, a silicate compound, and a silane compound containing an isocyanate group. When the reactive functional group is a carboxyl group, the preferred curing agent may be one or a combination of two or more selected from an amino curing agent and an epoxy curing agent. When the reactive functional group is an amino group, the curing agent may be one or a combination of two or more selected from a carbonyl-containing curing agent, an epoxy curing agent, and an acid anhydride curing agent. The curing agent content in the fluororesin composition is, for example, preferably 15 to 30 parts by mass, and more preferably 10 to 25 parts by mass, relative to 100 parts by mass of the fluoropolymer containing the reactive functional group. These numerical ranges also apply to the curing agent content in the cured product of the fluororesin composition. The curing agent content can be measured using a pyrolysis gas chromatography (Py-GC / MS) method. In one embodiment of the present invention, the reactive functional group contained in the fluoropolymer may be a hydroxyl group, and the curing agent may be an isocyanate curing agent. In this embodiment, the isocyanate curing agent is preferably hexamethylene diisocyanate (HDI) polyisocyanate. The content of HDI polyisocyanate in the fluoresin composition is, for example, preferably 15 parts by mass to 50 parts by mass, more preferably 20 parts by mass to 40 parts by mass, and more preferably 23 parts by mass to 35 parts by mass with respect to 100 parts by mass of the fluoropolymer containing the reactive functional group. These numerical ranges also apply to the HDI polyisocyanate content in the cured product of the fluoresin composition. Like HDI polyisocyanate, for example, one or a combination of two or more selected isocyanurate-type polyisocyanates, adduct-type polyisocyanates, and biuret-type polyisocyanates can be used. In the present invention, the isocyanate curing agent can preferably be an isocyanurate-type polyisocyanate and / or an adduct-type polyisocyanate, and more preferably a combination of an isocyanurate-type polyisocyanate and an adduct-type polyisocyanate. When a combination of isocyanurate-type polyisocyanate and adduct-type polyisocyanate is used as the curing agent, their mass ratio is, for example, preferably 10:6 to 10:10, more preferably 10:7 to 10:9. The total amount of both may be, for example, preferably 15 parts by mass to 50 parts by mass, more preferably 20 parts by mass to 40 parts by mass, and more preferably 25 parts by mass to 35 parts by mass with respect to 100 parts by mass of the fluoropolymer containing the reactive functional group. The content ratio of these curing agents can be determined by a pyrolysis gas chromatography (Py-GC / MS) method. The fluororesin forming the surface layer contains particles with an average particle size of preferably 1 µm to 10 µm, and more preferably 2 µm to 9 µm, measured using a laser diffraction particle size analysis method. The inclusion of these particles enhances the release properties of the release film mold. The particles are preferably inorganic or organic. Examples of inorganic particles include silicon dioxide (particularly amorphous silicon dioxide), calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, aluminum oxide, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide. Examples of organic particles include crosslinked polymer particles and calcium oxalate. In the present invention, the particles are preferably inorganic, more preferably silicon dioxide particles, and more preferably amorphous silicon dioxide. The amorphous silicon dioxide may be sol-gel type silica. For example, amorphous silicon dioxide of the Sylysia series may be used as the amorphous silicon dioxide. The particle content in the fluororesin composition can be, for example, preferably 10 parts by mass to 30 parts by mass, more preferably 12 parts by mass. > your NCNNCC N mass to 25 parts by mass, and preferably 15 parts by mass to 20 parts by mass with respect to 100 parts by mass of the fluoropolymer containing the reactive functional group. These numerical ranges also apply to the particle content in the cured product of the fluororesin composition. The particle content can be measured by thermogravimetric analysis (TGA). The fluororesin composition may contain a solvent. The type of solvent can be appropriately selected by those skilled in the art. Examples of solvents include butyl acetate, ethyl acetate, and methyl ethyl ketone (also referred to as MEK). For example, a mixture of these three types can be used as the solvent. The fluoresin composition may contain a release accelerator. Examples of release accelerators include amino-modified methylpolysiloxane, epoxy-modified methylpolysiloxane, carboxy-modified methylpolysiloxane, and carbinol-modified methylpolysiloxane. The preferred release accelerator is amino-modified methylpolysiloxane. The release accelerator content is, for example, preferably 0.01 parts by mass to 3 parts by mass, more preferably 0.05 parts by mass to 2 parts by mass, and more preferably 0.1 parts by mass to 1 part by mass with respect to 100 parts by mass of the fluoropolymer containing the reactive functional group. These numerical ranges also apply to the release accelerator content in the cured fluororesin composition. The thickness of the surface layer can be, for example, preferably 1 pm to 10 pm, more preferably 2 pm to 9 pm, and more preferably 3 pm to 8 pm. The fluororesin composition can be produced by mixing and stirring the components described above using methods known to those skilled in the art. A mixer such as, for example, a high-speed mixer, a homomixer, a paint stirrer, or the like, can be used for mixing and stirring. A dissolver such as, for example, a high-speed edge turbine-type dissolver, or the like, can be used for mixing and stirring. The cured fluororesin composition is obtained by applying the fluororesin composition to at least one surface of the base layer and heating it to, for example, preferably 100°C to 200°C, more preferably 120°C to 180°C for, for example, preferably 10 seconds to 240 seconds, more preferably 30 seconds to 120 seconds. The cured product forms the surface layer. The amount of fluororesin composition applied can be adjusted appropriately by those skilled in the art according to the thickness of the surface layer formed. Of the two surface layers laminated on either side of the base layer, one surface layer is in contact with the mold during the production of the inverted chip resin molded article, and the other surface layer is in contact with the molded article. In this specification, the surface layer in contact with the mold is referred to as the mold-side surface layer, and the surface layer in contact with the molded article is referred to as the molded article-side surface layer. The composition of the mold-side surface layer and the composition of the molded article-side surface layer may be the same or different. The preferred release accelerator is contained in the fluororesin of the surface layer on the molded article side. The release accelerator may be contained in both the fluororesin of the mold-side surface layer and the surface layer on the molded article side. In a preferred embodiment of the present technology, the mold-side surface layer is formed from a cured product of a fluororesin composition containing the fluoropolymer containing the reactive functional group, the curing agent, and the particles, and the molded article-side surface layer is formed from a cured product of a fluororesin composition containing the fluoropolymer containing the reactive functional group (particularly, a tetrafluoroethylene polymer containing a hydroxyl group), the curing agent, the particles, and the release accelerator. More preferably, the mold-side surface layer is formed from a cured product of a fluororesin composition containing a tetrafluoroethylene polymer containing a hydroxyl group, HDI polyisocyanate, and silicon dioxide particles, and the molded article-side surface layer is formed from a cured product of a fluororesin composition containing a tetrafluoroethylene polymer containing a hydroxyl group, HDI polyisocyanate, silicon dioxide particles, and amino-modified methylpolysiloxane. Having two surface layers particularly contributes to imparting excellent mold release properties with respect to the release film of the present invention. [Features of the release film] According to a preferred embodiment of the present invention, the trouser tear strength of the release film of the present invention is 5 N / mm or more. The release film is arranged between the upper mold 201 and the lower mold 203, in which the semiconductor element mounting substrate 202 is mounted. Then, as shown in Fig. 2(B), the upper mold 201 is brought into contact with the substrate 202 and the lower mold 203 in a state where the release film 100 is bonded to the inner surface of the mold 201. Then, as shown in Fig. 2(C), the resin 204 is introduced between the upper mold 201 and the substrate 202, and the resin 204 is cured. After curing, the upper mold 201 is separated from the substrate 202 as shown in Fig. 2(D).Since the release film of the present invention has excellent mold release properties, it is possible to uniformly release the cured resin 204 from the upper mold 201 in the step of Fig. 2(D). If the mold release properties of the release film are not good, the release film 250 may adhere to the cured resin 204, for example, as shown in Fig. 2(E). Examples of resins used to seal the semiconductor element in such transfer molding include epoxy resins and silicone resins. The release film of the present invention can be used to seal a semiconductor element using such a resin. The release film of the present invention can be used for molding, for example, preferably 2 or more times, preferably 4 or more times, preferably 5 or more times, preferably 6 or more times, and particularly preferably 8 or more times. The release film of the present invention can be used for molding, for example, preferably 2 to 20 times, preferably 4 to 15 times, preferably 5 to 15 times, preferably 6 to 15 times, and particularly preferably 8 to 12 times. The release film of the present invention maintains its performance through multiple releases and does not break easily. Therefore, the release film of the present invention can be used for a plurality of molds. This makes it possible to reduce the sealing (molding) cost. [Method for Manufacturing the Release Film] The present invention provides a method for manufacturing the release film described above. The manufacturing method includes an application step for applying a resin composition onto at least one surface of a base layer formed from a thermoplastic resin, and a curing step, following the application step, for curing the resin composition. The above explanation also applies to the base layer and the resin composition used in the application stage, and the description of the same is omitted. The application stage can be carried out appropriately by those skilled in the art to achieve the proposed layer thickness. For example, the resin composition can be applied to at least one surface of the base coat by etching, reverse laminating, offset etching, contact coating, reverse contact coating, wire rod coating, spray coating, or impregnation coating. Apparatus for application using such a method can be appropriately selected by those skilled in the art. The curing stage involves heating the resin composition to, for example, preferably 100°C to 200°C, or more preferably 120°C to 180°C for, for example, preferably 10 seconds to 240 seconds, or more preferably 30 seconds to 120 seconds. This heating process cures the resin composition. EXAMPLES The present invention will then be described in more detail based on examples. The examples described below are typical examples of the present invention, and the scope of the present invention is not limited to these examples. Test Category 1 (Evaluation of the resin composition coating film that forms the surface layer) In order to evaluate the physical properties of the resin composition that forms the surface layer of the release film of the present invention, a resin composition was prepared to form a resin composition coating pattern as shown below. Preparation of the resin composition (Al) 100 parts by mass of tetrafluoroethylene resin composition containing hydroxyl group (Zeffle (registered trademark) GK570, Daikin Kogyo Co., Ltd., of which 65% by mass is tetrafluoroethylene resin containing hydroxyl group), 12.9 parts by mass of isocyanurate-type polyisocyanate (curing agent, Sumidule (registered trademark) N3300, Sumitomo Bayer Urethane Co., Ltd.), 2.6 parts by mass of adduct-type polyisocyanate (curing agent, Duranato (registered trademark) AE700-100), and 45 parts by mass of ethyl acetate were mixed and stirred, to prepare a fluororesin (Al) composition. The fluororesin composition was applied to a spacer (polypropylene plate). The application was performed using a reverse contact coating apparatus. After application, the composition was cured by heating at 150°C for 30 seconds and aging at 60°C for 1 day. After aging, the spacer coated with the fluororesin composition was cut into pieces measuring 150 mm x 15 mm, and the cured fluororesin composition was released from the spacer to obtain a resin composition coating film. Preparation of the resin composition (A-2) A resin composition (A-2) was prepared by the same method as for the previous resin composition (A-1), except that 10 parts by mass of isocyanurate-type polyisocyanate (curing agent, Sumidule (registered trademark) N3300, Sumitomo Bayer Urethane Co., Ltd.), 7.8 parts by mass of adduct-type polyisocyanate (curing agent, Duranate (registered trademark) AE700-100), and 48 parts by mass of ethyl acetate were mixed, and a coating film was further obtained from the resin composition. Preparation of resin composition (A-3) A resin composition (A-3) was prepared by the same method as for the resin composition (Al) above, except that 8.6 parts by mass of isocyanurate-type polyisocyanate (curing agent, Sumidule (registered trademark) N3300, Sumitomo Bayer Urethane Co., Ltd.), 10.4 parts by mass of adduct-type polyisocyanate (curing agent, Duranate (registered trademark) AE700-100) and 50 parts by mass of ethyl acetate were mixed together, and a coating film was further obtained from the resin composition. Resin composition film formation (RA-1) A resin composition (RA-1) was prepared by the same method as for the resin composition film (Al) mentioned above, except that 14 parts by mass of isocyanurate-type poisocyanate (curing agent, Sumidule (registered trademark) N3300, Sumitomo Bayer Urethane Co., Ltd.) and 0 parts by mass of adduct-type poisocyanate (curing agent, Duranate (registered trademark) AE700-100) were mixed, and a coating film of the resin composition was further obtained. Resin composition film formation (RA-2) One hundred parts by mass of UV-curable acrylate resin composition (RA-2, SEIKO PMC Corp., 35% of which is acrylate resin) and five parts by mass of photoinitiator (Irgacure (registered trademark) 184, BASF Co., Ltd.) were mixed and stirred to prepare a UV-curable resin composition (RA-2). The UV-curable resin composition was applied to a separator (polypropylene plate). The application was performed using a reverse contact coating apparatus. After application, the composition was heated to 100°C for 30 seconds and then cured by irradiation at 600 mJ with a 120 W / cm² high-pressure mercury lamp. After curing, the spacer coated with the UV-curable resin composition was cut into pieces that are sized 150 mm × 15 mm, and the cured UV-curable resin composition was released from the spacer to obtain a resin composition coating film. [Evaluation of the flow capacity of the surface layer (release layer)J The test pieces of the previous resin composition coating film (Al to RA-1) were tested using a constant temperature bath tensile tester (Shimadzu Autograph AG-IS MS (floor-mounted type)), and the elongation at break (%) at a measuring temperature of 175°C was measured with a clamping width of 20 mm and a measuring speed of 20 mm / min according to JIS K7127. The measured value of the elongation at break (%) was calculated from the average value of 10 test pieces. The results are shown in Table 1. [Table 1] bz / nin / zznz / Ε / γΐΛΐ RA-2 36 70 RA-1 100 OO co Ó? A-3 100 50 9.8 10.4 169 50 co 8.5 344 CM < 100 48 OT“” 7.8 165.8 50 r- co 8.5 304 A-1 100 45 12.9 2.6 160.5 50 o T 8.5 173 UV Curable Resin Fluororesin (GK570) Ethyl Acetate N3300 AE-700 N3300 AE-700 Resin Composition Curing Agent Total Amount AN Curing Agent Mixing Ratio (on a molar basis) Peel Strength (nN / 30mm) Elongation at Break (%GL) [Evaluation of the mold release properties of the surface layer (release layer)] A single polyethylene terephthalate (PET) film was placed on a heated plate, 0.5 g of the following black epoxy resin was applied to it, and on the epoxy-coated surface, a test piece 30 mm wide and 100 mm long, obtained by applying a resin composition to a polyester film, was aligned with the resin-coated surface. The black epoxy resin was then cured at a heating temperature of 175°C for 5 minutes. After curing, a tensile peel tester (VPA-2 manufactured by Kyowa Interface Science Co., Ltd.) was used to measure the peel strength between the test piece and the epoxy resin. Black epoxy resin: An epoxy resin composition obtained by adding 83% by mass of a filler having a filler diameter of 20 pm / 55 pm, spherical silica in this case, to an epoxy resin (EF-200 manufactured by SANYU REC Co., Ltd.) and subjecting it to a gelation treatment was used. Peeling conditions: Peeling was performed under conditions of a peeling speed of 100 mm / min and a peeling temperature of 175°C according to JIS Z0237. The results are also shown in Table 1. Test Category 2 (Release Film Evaluation) [Tear resistance of the release film trousers] A 150 mm × 50 mm test piece was cut from the release films of the following Examples and Comparative Examples, and a 75 mm cut was made from the midpoint of the short side in the direction of the long side of the test piece. The Tensilon Universal Testing Machine (A & D Co., Ltd., RTG-1210) was used to measure the tear strength of the trousers at a mandrel distance of 75 mm and a measuring speed of 200 mm / min in accordance with JIS K7128-1. The results are shown in Table 2 below. (Example 1) As a base layer, a film was prepared made of an easily moldable polyethylene terephthalate resin (Teflex (registered trademark) FT, Teijin Limited, thickness 50 pm, glass transition temperature 90°C). The resin composition (Al) was applied to both surfaces of the film. The application was performed using a reverse contact coating apparatus. After application, the resin composition (Al) was cured by heating to 150°C for 60 seconds, and a release film was formed in which a fluororesin layer was laminated to both sides of an easily moldable PET resin film (then in > The present one, referred to as the liberation film of Example 1) was obtained. NCNN The thickness of the release film in Example 1 was 70 ± 5 pm. The thickness of the base layer in the release film of Example 1 was 50 pm ± 10%. The thickness of the surface layer of the release film of Example 1 was 5.5 ± 0.5 pm. The trouser tear strength of the release film of Example 1 was measured according to JIS K7128-1 and found to be 27.77 N / mm. The peel strength of the resin composition (Al) in the release film was measured at 175°C according to JIS Z0237 and found to be 8.5 mN / 30 mm. (Example 2) A release film (hereafter referred to as the Example 2 release film) was obtained by the same method as in Example 1, except that resin composition (A-2) was used. The thickness of the release film in Example 2 was 70 ± 5 pm. The thickness of the base layer in the release film of Example 2 was 50 pm ± 10%. The thickness of the surface layer of the release film of Example 2 was 5.5 ± 0.5 pm. The tear resistance of the Example 2 release film was measured in accordance with JIS K7128-1 > you NCNN and was found to be 27.77 N / mm. The release strength of the resin composition (A-2) on the release film was measured at 175°C according to JIS Z0237 and was found to be 8.5 mN / 30 mm. (Example 3) A release film (hereafter referred to as the Example 3 release film) was obtained by the same method as in Example 1, except that resin composition (A-3) was used. The thickness of the release film in Example 3 was 70 ± 5 pm. The thickness of the base layer in the release film of Example 3 was 50 pm ± 10%. The thickness of the surface layer of the release film of Example 3 was 5.5 ± 0.5 pm. The trouser tear strength of the release film of Example 3 was measured according to JIS K7128-1 and found to be 27.77 N / mm. The peel strength of the resin composition (A-3) on the release film was measured at 175°C according to JIS Z0237 and found to be 8.5 mN / 30 mm. (Comparative Example 1) A release film (hereafter referred to as the release film of Comparative Example 1) was obtained by the same method as in Example 1, except that the ream composition (RA-l) was used. The thickness of the release film of the Example Comparative Example 1 was 70 ± 5 pm. The base layer thickness in the release film of Comparative Example 1 was 50 pm + 10%. The surface layer thickness of the release film of Comparative Example 1 was 5.5 ± 0.5 pm. The tear strength of the release film in Comparative Example 1 was measured according to JIS K7128-1 and found to be 27.77 N / mm. The peel strength of the resin composition (RA-1) in the release film was measured at 175°C according to JIS Z0237 and found to be 8.5 mN / 30 mm. (Comparative Example 2) A release film (hereafter referred to as the release film of Comparative Example 2) was obtained by the same method as in Example 1, except that the resin composition (RA-2) was used. The thickness of the release film in Comparative Example 2 was 70 ± 5 pm. The thickness of the base layer in the release film of Comparative Example 2 was 50 pm ± 10%. The thickness of the surface layer of the release film of Comparative Example 2 was 5.5 ± 0.5 pm. The trouser tear resistance of the release film from Comparative Example 2 was measured according to JIS K7128-1 and found to be 27.77 N / m. The peel strength of the resin composition (RA-2) on the release film was measured at 175°C according to JIS Z0237 and was found to be 36 mN / 30 mm. (Example 4) As a base layer, a film was prepared made of an easily moldable polyethylene terephthalate resin (Emblet (registered trademark) CTK-38, Unitika Ltd., 38 pm thickness, glass transition temperature 65°C). The resin composition (Al) was applied to both surfaces of the film. After application, these compositions were cured by heating to 150°C for 60 seconds, and a release film was obtained in which a fluororesin layer was laminated to both sides of an easily moldable PET resin film (hereafter referred to as the Example 4 release film). The thickness of the release film in Example 4 was 60 ± 5 pm. The thickness of the base layer in the release film of Example 4 was 38 pm ± 10%. The thickness of the surface layer of the release film of Example 4 was 5.5 + 0.5 pm. The trouser tear strength of the release film in Example 4 was measured according to JIS K7128-1 and found to be 12.41 N / mm. The peel strength of the resin composition (Al) in the release film was measured at 175°C according to JIS Z0237 and found to be 0.5 mN / 30 mm. (Example 5) As a base layer, a film was prepared made of ordinary polyethylene terephthalate resin (Tetoron (registered trademark) G2CW, Teijin Limited, 38pm thickness, glass transition temperature 100°C). The resin composition (Al) was applied to both surfaces of the film. After application, these compositions were cured by heating to 150°C for 60 seconds, and a release film was obtained in which a fluororesin layer was laminated to both sides of an easily moldable PET resin film (hereafter referred to as the Example 5 release film). The thickness of the release film in Example 5 was 60 ± 5 pm. The thickness of the base layer of the release film in Example 5 was 38 pm ± 10%. The thickness of the surface layer of the release film in Example 5 was 5.5 ± 0.5 pm. The tear strength of the Example 5 release film was measured according to JIS K7128-1 and found to be 6.29 N / mm. The peel strength of the resin composition (Al) in the release film was measured at 175°C according to JIS Z0237 and found to be 8.5 mN / 30 mm. > s NCNN C C N A [Table 2] Comparative Example 2 RA-2 LLLZ 36 Comparative Example 1 RA-1 27.77 8.5 Example 5 A-1 6.29 8.5 Example 4 A-1 12.41 8.5 Example 3 A-3 27.77 8.5 Example 2 A-2 27.77 8.5 Example 1 A-1 27.77 8.5 Resin composition Trouser tear resistance (N / mm) Peel strength (mN / 30 mm) Commercially available release film 2 1.75 23.5 Commercially available release film 1 23.62 16.5 Resin composition Trouser tear strength (N / mm) Peel strength (mN / 30 mm) (Adaptability of the release film for multi-shot molding) The release film from Comparative Example 1 was used to perform transfer molding of an epoxy resin. The molding was carried out as shown in Fig. 2. The molding was performed so that the layer formed from the fluororesin composition of the molded article was in contact with the mold, and the layer formed from the fluororesin composition of the molded article was in contact with the epoxy resin. The release film used in the previous molding was then used to perform the same molding once more. The same release film was used for the same molding two more times, and the molding was performed a total of four times with the single release film. The release film from Example 1 was used to seal the semiconductor element with the epoxy resin four times in the same manner as in Comparative Example 1. The release films of Examples 2 to 5 were also used to perform the molding of an epoxy resin by transfer molding four times in the same manner as in Comparative Example 1. The molded article from an epoxy resin was uniformly released from each release film of Examples 1 to 5 after each of the first through fifth molding operations. This has revealed that the release films of Examples 1 to 5 have excellent mold release properties and that these properties are maintained through multiple molding operations. The release films from Examples 1 to 5 were used continuously in at least four models. Furthermore, when the molding process was repeated multiple times, the release films of Examples 1 and 2 broke in the 10th and 10th moldings, respectively. The release film of Example 3 broke in the fifth molding. Therefore, the release films of Examples 1 and 2 can be used for molding more times than the release film of Example 3. That is, the release films of Examples 1 and 2 have better adaptability for multi-shot molding than the release film of Example 3. Previous results on adaptability for multi-shot molding, as well as trouser tear resistance, reveal that by adjusting the trouser tear resistance of the release film, the resulting release film can be used for molding more times. The tear resistance of the release film from Comparative Example 1 was 6 N / mm, as described above. The release film from Example Comparative 1 was also used to perform the molding multiple times and broke on the 10th molding. In addition, two types of commercially available release films were prepared. The tear strength of the first release film was 23.62 N / mm, as measured by the method described above. The tear strength of the second release film was 1.75 N / mm, as measured by the same method. These two release films were tested by undergoing multiple molding cycles, as described above. As a result, the first release film tore on the third molding cycle. The second release film tore on the second molding cycle. The results of the adaptability for multi-shot molding for the release films of Examples 1 to 5 and Comparative Example 1 and the commercially available release films (hereafter referred to as commercially available release films 1 and 2) and the trouser tear strength of these films reveal that when the release film has a trouser tear strength of 5 N / mm or more, the resulting release film can be used for sealing more times. Description of reference numbers 100: Release Film 101: Base layer 102: Top layer 103: Top layer

Claims

1. A release film, characterized in that it has a base layer formed of a thermoplastic resin and a surface layer formed of a resin composition laminated on at least one surface of the base layer, wherein the tear strength of the trousers according to JIS K7128-1 is 5 N / mm or more, the peel strength of the resin composition is 15 mN / 30 mm or less when measured at 175°C according to JIS Z0237, and the elongation at break of the resin composition is 70% or more when measured at 175°C according to JIS K7127.

2. The release film according to claim 1, characterized in that the resin composition is a fluororesin.

3. The release film according to claim 1 or 2, characterized in that the resin composition contains an isocyanate curing agent.

4. The release film according to any of claims 1 to 3, characterized in that the resin composition contains a tetrafluoroethylene resin.

5. The release film according to any of claims 1 to 4, characterized in that it is used in sealing a semiconductor that is connected to an inverted chip.

6. The release film according to any of claims 1 to 5, characterized in that it is used for molding two or more times.