Method for manufacturing release film and semiconductor package

Abstract

To provide a mold release film having excellent peelability from a face having a protrusion.SOLUTION: A mold release film comprises a base material layer and an adhesive layer, wherein the thickness of the adhesive layer is 4-30% of the total thickness of the base material layer and the adhesive layer, and the thickness of the base material layer is 75 μm or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a release film and a semiconductor package. [Background technology]

[0002] In recent years, as electronic devices, especially mobile phones, have become thinner, there is a growing demand for even thinner semiconductor packages that contain electronic components such as semiconductor elements. Furthermore, from the perspective of improving heat dissipation, exposed die molding, which leaves a portion of the surface of electronic components exposed, is increasingly being adopted as an alternative to overmolding, which covers the entire electronic component with encapsulating resin.

[0003] When sealing electronic components in a way that leaves a portion of the component exposed, it is necessary to prevent leakage of the sealing material (flash burr) to the exposed portion of the electronic component. Therefore, a release film is applied to the portion of the electronic component to be exposed before sealing, and then the release film is peeled off to expose the surface of the electronic component. As an example of such a release film, Patent Document 1 describes a laminated film in which a film made of fluororesin is laminated on at least one side of a base film made of stretched polyester resin film. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent Application No. 2005-186740 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The release film described in Patent Document 1 does not have sufficient adhesion to electronic components, and there is a risk that the sealing material may penetrate the area to which the release film is attached during the sealing process. Furthermore, as semiconductor packages become smaller, the solder balls on electronic components also tend to become smaller, necessitating the protection of a portion of the solder balls with a sealing material to prevent cracking. As a result, there are cases where a release film is applied to the surface on which the solder balls are formed.

[0006] When applying a release film to a surface with protrusions such as solder balls, it is necessary that the solder balls are sufficiently exposed on the surface after the release film has been removed. One aspect of the present invention aims to provide a release film that exhibits excellent peelability from surfaces having protrusions. Another aspect of the present invention aims to provide a method for manufacturing a semiconductor package using this release film. [Means for solving the problem]

[0007] The following embodiments are included as means for solving the above problems. <1> A release film comprising a base layer and an adhesive layer, wherein the thickness of the adhesive layer is 4% to 30% of the total thickness of the base layer and the adhesive layer, and the thickness of the base layer is 75 μm or more. <2> To expose at least a portion of the surface of an electronic component that has solder balls, <1> The release film described above. <3> The adhesive layer contains an acrylic adhesive. <1> or <2> The release film described above. <4> <1> ~ <3> A method for manufacturing a semiconductor package, comprising the steps of: sealing the area around an electronic component with the adhesive layer of the release film described in any one of the above items in contact with at least a portion of the surface of the electronic component; and peeling the release film from the electronic component. <5> At least a portion of the surface of the electronic component that the adhesive layer contacts has solder balls. <4> A method for manufacturing semiconductor packages as described above. [Effects of the Invention]

[0008] According to the present invention, a release film is provided that exhibits excellent peelability from surfaces having protrusions. According to another aspect of the present invention, a method for manufacturing a semiconductor package using this release film is provided. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view showing an example of the structure of the release film disclosed herein. [Modes for carrying out the invention]

[0010] The embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including elemental steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and they do not limit the present invention.

[0011] In this specification, the term "process" includes not only processes that are independent of other processes, but also processes that cannot be clearly distinguished from other processes, provided that the purpose of the process is achieved. In this specification, numerical ranges indicated using "~" include the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described stepwise within this specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Furthermore, in numerical ranges described within this specification, the upper or lower limit of that range may be replaced with the values ​​shown in the examples. In this specification, the content or amount of each component in a composition means the total content or amount of the multiple substances present in the composition, unless otherwise specified, if multiple substances corresponding to each component are present in the composition. In this specification, the particle size of each component in a composition refers to the value for a mixture of multiple types of particles present in the composition, unless otherwise specified, if multiple types of particles corresponding to each component are present in the composition. In this specification, the term "layer" includes not only the case where it is formed over the entire area being observed, but also the case where it is formed only in a part of the area. In this specification, the thickness of the release film or each layer constituting the release film can be measured by known methods. For example, it may be measured using a dial gauge or the like, or may be measured from a cross-sectional image of the release film. Alternatively, the layer-forming material may be removed using a solvent or the like, and calculated from the mass before and after removal, the density of the material, the area of the layer, etc. When the thickness of the layer is not constant, the arithmetic mean value of the values measured at any five points is taken as the thickness of the layer.

[0012] In this specification, "(meth)acryloyl group" means at least one of an acryloyl group and a methacryloyl group, "(meth)acrylic" means at least one of acrylic and methacrylic, and "(meth)acrylate" means at least one of acrylate and methacrylate.

[0013] <Release film> The release film of the present disclosure includes a base material layer and an adhesive layer, and is a release film in which the thickness of the adhesive layer is 4% to 30% of the total thickness of the base material layer and the adhesive layer, and the thickness of the base material layer is 75 μm or more.

[0014] Even when convex portions such as solder balls are formed on the surface of the electronic component, the above release film is unlikely to cause deformation of the convex portions or remaining of the adhesive layer on the surface having the convex portions. Therefore, the state of the convex portions in the portion where the release film is peeled off is maintained well.

[0015] Hereinafter, the release film of the present disclosure will be described with reference to the drawings, but the present invention is not limited thereto. Also, the sizes of the members shown in the drawings are conceptual, and the relative relationships of the sizes between the members are not limited thereto.

[0016] Figure 1 is a schematic cross-sectional view showing an example of the structure of the release film of this embodiment. The release film 30 shown in Figure 1 is composed of a base layer 20 and an adhesive layer 10. If necessary, the release film may also include layers other than the base layer 20 and the adhesive layer 10 (for example, a conductive layer).

[0017] The release film of this disclosure is peeled off after a sealing process or other treatment is performed with the adhesive layer side attached to the surface of an object to be adhered, such as an electronic component. The release film of this disclosure has excellent peelability from surfaces having protrusions. For this reason, it is suitably used, for example, in a semiconductor package manufacturing method by exposed molding, particularly when at least a portion of the surface having protrusions of an electronic component is exposed.

[0018] (base material layer) The thickness of the substrate layer is 75 μm or more. A substrate layer thickness of 75 μm or more ensures sufficient adhesion to surfaces with protrusions, thereby suppressing the penetration of the sealing material. The substrate layer thickness is preferably 80 μm or more, and more preferably 90 μm or more. There is no particular upper limit to the substrate layer thickness. For example, the substrate layer thickness may be 200 μm or less.

[0019] The material of the base layer is not particularly limited. From the viewpoint of conformability to the mold, resin is preferred. Examples of resins include polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyimides, polyamides, polyester ethers, polyamide-imides, and fluorine-containing resins. When using resin, it is preferable that it has sufficient heat resistance to the heating temperature during the sealing process.

[0020] If necessary, the side of the substrate layer on which the adhesive layer is provided may be treated to improve the adhesion between the substrate and the adhesive layer. Examples of treatment methods include surface treatments such as corona treatment and plasma treatment, and application of a primer.

[0021] If necessary, a back treatment agent may be applied to the back surface of the base layer (the side opposite to the adhesive layer) to adjust the unwinding properties of the release film from the roll. Examples of back treatment agents include individual components, modified forms, and mixtures of silicone resins, fluorine-containing resins, polyvinyl alcohol, and alkyl group resins.

[0022] If necessary, an antistatic agent may be applied to the back surface of the base layer or the side on which the adhesive layer is provided in order to suppress the generation of static electricity when the release film is unwound or when it is peeled from the adherend. Examples of antistatic agents include cationic antistatic agents having cationic groups such as quaternary ammonium salts, pyridium salts, and primary to tertiary amino groups; anionic antistatic agents having anionic groups such as sulfonic acid bases, sulfate ester bases, and phosphate ester bases; amphoteric antistatic agents such as amino acid-based and amino acid sulfate ester-based agents; nonionic antistatic agents having nonionic groups such as amino alcohol-based, glycerin-based, and polyethylene glycol-based agents; and polymeric antistatic agents that are high molecular weight versions of these antistatic agents. These antistatic agents are also preferable in that they have good transparency.

[0023] (Adhesive layer) The adhesive layer has a thickness of 4% to 30% of the combined thickness of the base layer and the adhesive layer. Hereafter, the ratio of the adhesive layer's thickness to the combined thickness of the base layer and the adhesive layer will also be referred to as the "adhesive layer thickness ratio." A thickness ratio of 4% or more of the adhesive layer ensures sufficient adhesion to the protrusions, suppressing the penetration of the sealant. On the other hand, a thickness ratio of 30% or less of the adhesive layer makes it less likely for the adhesive layer to remain on the surface with protrusions when the release film is peeled off, thus maintaining the condition of the protrusions well. The thickness ratio of the adhesive layer may also be between 4.8% and 25%.

[0024] Examples of adhesive layers include layers containing adhesives such as acrylic adhesives, silicone adhesives, rubber adhesives, and urethane adhesives. The adhesive layer may contain one type of adhesive or two or more types. In the present invention, the adhesive contained in the adhesive layer may be partially or completely reacted, or unreacted. Furthermore, it may be in a hardened state due to heat or the like, or in an unhardened state.

[0025] (1) Acrylic adhesive In this specification, "acrylic adhesive" means an adhesive that uses an acrylic polymer as its base polymer. An acrylic polymer is a monomer having at least one (meth)acryloyl group in one molecule (hereinafter, this may be referred to as "acrylic monomer"). This refers to a polymer whose main constituent monomer is acrylic polymer (a component that accounts for 50% or more by mass of the total amount of monomers constituting the acrylic polymer). Acrylic adhesives are advantageous in terms of transparency, weather resistance, heat resistance, solvent resistance, etc.

[0026] When designing the acrylic polymer contained in acrylic adhesives, it is important to adjust the type of monomer and molecular weight, taking into consideration factors such as the glass transition temperature (adhesion to the adherend, applicable temperature, etc.), the introduction of crosslinking points (durability, heat resistance, etc.), and the copolymerizability of the acrylic monomer (uniformity of the molecular structure and crosslinking points of the acrylic polymer). To introduce crosslinking points into the molecule, the acrylic polymer is synthesized using monomers (acrylic acid, hydroxyethyl acrylate, etc.) that contain functional groups that can react with the crosslinking agent used in combination.

[0027] Examples of acrylic polymers include polymers whose main constituent monomer is alkyl (meth)acrylate. For example, compounds represented by the following formula (1) can be suitably used as alkyl (meth)acrylate. CH2=C(R 1 )COOR 2 (1)

[0028] Here, in equation (1) above, R 1 R represents a hydrogen atom or a methyl group. 2 This represents an alkyl group having 1 to 20 carbon atoms (which may be either a linear alkyl group or an alicyclic alkyl group).

[0029] From the perspective of obtaining an adhesive with superior adhesive performance, R 2 It is preferable that the C2-14 chain alkyl group has 2 to 14 carbon atoms (either a linear or branched alkyl group). Examples of C2-14 chain alkyl groups include ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, n-pentyl group, isoamyl group, neopentyl group, n-hexyl group, n-heptyl group, n-octyl group, isooctyl group, 2-ethylhexyl group, n-nonyl group, isononyl group, n-decyl group, isodecyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, etc. 2 Examples of alicyclic alkyl groups when is an alicyclic alkyl group include cyclohexyl group and isobornyl group.

[0030] From the viewpoint of obtaining an acrylic polymer with superior adhesive performance, 50% by mass or more (e.g., 50% to 99.9% by mass), more preferably 70% by mass or more (e.g., 70% to 99.9% by mass), and even more preferably 85% by mass or more (e.g., 85% to 99.9% by mass) of the total amount of monomers used in the synthesis of the acrylic polymer should be R in formula (1) above. 2 It is preferable that R is a (meth)acrylate in which the C2-C14 chain alkyl group is, 2 It is more preferable that the compound is a C4-10 chain-like alkyl acrylate, and even more preferable that it is at least one selected from n-butyl acrylate and 2-ethylhexyl acrylate.

[0031] Acrylic polymers preferably have hydroxyl groups as crosslinking points. As acrylic polymers having hydroxyl groups, those containing acrylic monomers containing hydroxyl groups as polymerization components can preferably be used.

[0032] Specific examples of acrylic monomers containing hydroxyl groups include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxyhexyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, (4-hydroxymethylcyclohexyl)methyl acrylate, polypropylene glycol mono(meth)acrylate, N-hydroxyethyl (meth)acrylamide, and N-hydroxypropyl (meth)acrylamide. Acrylic monomers containing hydroxyl groups may be used individually or in combination of two or more.

[0033] Among acrylic monomers containing hydroxyl groups, (meth)acrylates containing hydroxyl groups are preferred. Preferred hydroxyl-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

[0034] In the synthesis of acrylic polymers having hydroxyl groups, the proportion of acrylic monomers containing hydroxyl groups among the total amount of monomers used may be, for example, in the range of 0.01% to 20% by mass, preferably in the range of 0.05% to 15% by mass, and more preferably in the range of 0.1% to 10% by mass.

[0035] Acrylic polymers may contain acrylic monomers having functional groups other than hydroxyl groups and monomers other than acrylic monomers (hereinafter also referred to as "other monomers") as polymerization components. Other monomers can be used, for example, to adjust the Tg, tackiness, etc., of the acrylic polymer. For example, monomers that can improve the cohesive force and heat resistance of adhesives include sulfonic acid group-containing monomers, phosphate group-containing monomers, cyano group-containing monomers, vinyl esters, aromatic vinyl compounds, etc. Furthermore, monomers that can introduce functional groups that can act as crosslinking sites in acrylic polymers or contribute to improving adhesive strength include carboxyl group-containing monomers, acid anhydride group-containing monomers, amide group-containing monomers, amino group-containing monomers, imide group-containing monomers, epoxy group-containing monomers, (meth)acryloylmorpholine, vinyl ethers, etc. Other monomers may be used individually or in combination of two or more.

[0036] Examples of monomers containing sulfonic acid groups include styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, sulfopropyl (meth)acrylate, (meth)acryloyloxynaphthalenesulfonic acid, and sodium vinylsulfonate. Examples of monomers containing a phosphate group include 2-hydroxyethyl acryloyl phosphate. Examples of cyano group-containing monomers include acrylonitrile and methacrylonitrile. Examples of vinyl esters include vinyl acetate, vinyl propionate, and vinyl laurate. Examples of aromatic vinyl compounds include styrene and substituted styrenes (chlorostyrene, chloromethylstyrene, α-methylstyrene, etc.).

[0037] Examples of monomers containing a carboxyl group include acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Examples of monomers containing acid anhydride groups include maleic anhydride, itaconic anhydride, and acid anhydrides of the above-mentioned carboxyl group-containing monomers. Examples of monomers containing amide groups include acrylamide, methacrylamide, diethylacrylamide, N-vinylpyrrolidone, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N,N'-methylenebisacrylamide, N,N-dimethylaminopropylacrylamide, N,N-dimethylaminopropylmethacrylamide, and diacetoneacrylamide. Examples of amino group-containing monomers include aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and N,N-dimethylaminopropyl (meth)acrylate. Examples of imide group-containing monomers include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide. Examples of epoxy group-containing monomers include glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, and allyl glycidyl ether. Examples of vinyl ethers include methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether.

[0038] When an acrylic polymer contains other monomers as polymerization components, the content of the other monomers is preferably 40% by mass or less, and more preferably 30% by mass or less, of the total amount of monomers used in the synthesis of the acrylic polymer. Furthermore, it is preferable that the total amount of other monomers is 0.001% by mass or more of the total amount of monomers used in the synthesis of the acrylic polymer.

[0039] The acrylic polymer may contain only acrylic monomers as polymerization components. Examples of acrylic polymers containing only acrylic monomers as polymerization components include acrylic polymers containing only alkyl (meth)acrylates having 6 to 14 carbon atoms as polymerization components, acrylic polymers containing only alkyl (meth)acrylates having 6 to 14 carbon atoms and hydroxyl group-containing (meth)acrylates as polymerization components, and the like.

[0040] The weight-average molecular weight (Mw) in terms of standard polystyrene obtained by gel permeation chromatography (GPC) of the acrylic polymer may be, for example, 20×10 4 or more, and preferably 30×10 4 or more. Also, for example, it may be 90×10 4 or less, and preferably 80×10 4 or less. When the weight-average molecular weight of the acrylic polymer is within the above range, an adhesive showing good adhesion performance tends to be obtained.

[0041] The acrylic polymer may be a random copolymer, a block copolymer, a graft copolymer, or the like. From the viewpoint of productivity and the like, it is usually preferably a random copolymer.

[0042] The glass transition temperature (Tg) of the acrylic polymer is preferably -15°C or lower, more preferably -25°C or lower, and even more preferably -40°C or lower. Also, it is preferably -70°C or higher. When the glass transition temperature (Tg) of the acrylic polymer is within the above range, an adhesive showing good adhesion performance tends to be formed.

[0043] In this specification, the Tg of an acrylic polymer refers to the value obtained from Fox's formula based on the Tg of the homopolymer (constituent polymer) of each monomer constituting the acrylic polymer and the mass fraction (mass-based copolymerization ratio) of the monomer. Therefore, the Tg of an acrylic polymer can be adjusted by appropriately changing the monomer composition (i.e., the type and ratio of monomers used in the synthesis of the acrylic polymer). Here, the Tg of the homopolymer will be the value described in the publicly available document ("Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989)). Specifically, the following values ​​will be used as the Tg of the homopolymer.

[0044] Homopolymer of 2-ethylhexyl acrylate: -70℃ Homopolymer of n-butyl acrylate: -55℃ Ethyl acrylate homopolymer: -22℃ Homopolymer of methyl acrylate: 8℃ Homopolymer of methyl methacrylate: 105℃ Homopolymer of cyclohexyl methacrylate: 66℃ Homopolymer of vinyl acetate: 32℃ Styrene homopolymer: 100℃ Acrylic acid homopolymer: 106℃ Homopolymer of methacrylic acid: 130℃

[0045] For homopolymers not listed in the "Polymer Handbook," the Tg value measured by the following method should be used. In a reactor equipped with a thermometer, stirrer, nitrogen inlet tube, and reflux condenser, 100 parts by mass of monomer, 0.2 parts by mass of azobisisobutyronitrile, and 200 parts by mass of ethyl acetate as the polymerization solvent are added, and the mixture is stirred at room temperature (25°C) for 1 hour while circulating nitrogen gas. After removing oxygen from the polymerization system in this way, the temperature is raised to 63°C and the reaction is carried out for 10 hours. Then, the mixture is cooled to room temperature (25°C) to obtain a homopolymer solution with a solid content of 33% by mass. Next, this homopolymer solution is cast onto a release liner and dried to prepare a test sample (sheet-like homopolymer) with a thickness of approximately 2 mm. This test sample is punched out into a disc shape with a diameter of 7.9 mm, sandwiched between parallel plates, and the viscoelasticity is measured using a viscoelasticity tester (ARES, Rheometrics) in shear mode while applying a shear strain at a frequency of 1 Hz in the temperature range of -70°C to 150°C at a heating rate of 5°C / min. The peak top temperature of tanδ is taken as the Tg of the homopolymer.

[0046] The method for synthesizing the acrylic polymer is not particularly limited, and commonly used methods such as solution polymerization, emulsion polymerization, bulk polymerization, and suspension polymerization can be applied. From the viewpoint of ease of preparation of the solvent-type adhesive composition containing the acrylic polymer, solution polymerization is preferred. The organic solvent (polymerization solvent) used in solution polymerization is not particularly limited and examples include toluene, ethyl acetate, hexane, and cyclohexane. One organic solvent may be used, or two or more may be used.

[0047] In this specification, a solvent-type adhesive composition means a composition in which an adhesive component is contained in an organic solvent. The organic solvent is not particularly limited. Examples include toluene, xylene, ethyl acetate, hexane, cyclohexane, methylcyclohexane, isopropyl alcohol, etc. The organic solvent may be one type or two or more types. The solvent-type adhesive composition preferably has an NV (non-volatile content) of 30% to 60% by mass of the total, and more preferably 30% to 50% by mass. The viscosity of the solvent-type adhesive composition is preferably 3 Pa·s to 25 Pa·s, and more preferably 5 Pa·s to 15 Pa·s. The above viscosity refers to the value measured using a rotational viscometer in an environment of 23°C.

[0048] Acrylic adhesives may be designed to allow the acrylic polymer to crosslink. Specific methods for crosslinking an acrylic polymer include introducing functional groups (such as hydroxyl groups or carboxyl groups) that can act as crosslinking sites into the polymerization components of the acrylic polymer, and then adding a compound (crosslinking agent) that can react with these functional groups to form a crosslinked structure to the acrylic polymer and allowing the reaction to occur.

[0049] The crosslinking agent is not particularly limited and may be selected from common compounds used for crosslinking acrylic polymers. Examples include epoxy crosslinking agents, isocyanate crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, carbodiimide crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, and amine crosslinking agents, with epoxy crosslinking agents and isocyanate crosslinking agents being preferred. The crosslinking agent used may be a single agent or two or more agents.

[0050] Examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate ester, diglycidyl o-phthalate ester, triglycidyl-tris(2-hydroxyethyl) isocyanurate, resorcinol diglycidyl ether, bisphenol-S-diglycidyl ether, and epoxy resins having two or more epoxy groups in the molecule.

[0051] Examples of isocyanate-based crosslinking agents include lower aliphatic polyisocyanate compounds such as 1,2-ethylene diisocyanate, 1,4-butylene diisocyanate, and 1,6-hexamethylene diisocyanate; aliphatic polyisocyanate compounds such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated xylene diisocyanate; and aromatic polyisocyanate compounds such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate.

[0052] The amount of crosslinking agent used can be, for example, about 0.01 to 15 parts by mass per 100 parts by mass of acrylic polymer, and preferably 0.1 to 10 parts by mass (for example, 0.2 to 2 parts by mass). When crosslinking agent is included in such amounts, an adhesive exhibiting good tackiness tends to be obtained.

[0053] Acrylic adhesives may contain various additives as needed. Examples of additives include surface lubricants, leveling agents, antioxidants, preservatives, light stabilizers, UV absorbers, polymerization inhibitors, and silane coupling agents.

[0054] Acrylic adhesives may contain tackifying resins as needed. The type of tackifying resin is not particularly limited and includes rosin-based tackifying resins, terpene-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, polyamide-based tackifying resins, elastomer-based tackifying resins, phenol-based tackifying resins, ketone-based tackifying resins, and the like. The tackifying resin contained in the acrylic adhesive may be a single type or two or more types.

[0055] Examples of rosin-based tackifying resins include unmodified rosin (raw rosin) such as gum rosin, wood rosin, and tall oil rosin; modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosin) obtained by hydrogenation, disproportionation, polymerization, etc. of unmodified rosin; and various other rosin derivatives. Examples of rosin derivatives include: rosin esters obtained by esterifying unmodified or modified rosin with alcohols; rosin modified with unsaturated fatty acids (unsaturated fatty acid modified rosin); rosin esters modified with unsaturated fatty acids (unsaturated fatty acid modified rosin esters); rosin alcohols obtained by reducing the carboxyl groups in unmodified rosin, modified rosin, unsaturated fatty acid modified rosin, or unsaturated fatty acid modified rosin esters; metal salts of unmodified rosin, modified rosin, and the above-mentioned rosin derivatives (especially rosin esters); and rosinphenol resins obtained by adding phenol to unmodified rosin, modified rosin, and the above-mentioned rosin derivatives with an acid catalyst and then thermally polymerizing them.

[0056] Examples of terpene-based tackifying resins include terpene resins such as α-pinene polymers, β-pinene polymers, and dipentene polymers; and modified terpene resins obtained by modifying these terpene resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbon modification, etc.). Examples of modified terpene resins include terpene-phenol resins, styrene-modified terpene resins, aromatic-modified terpene resins, and hydrogenated terpene resins.

[0057] Examples of hydrocarbon-based tackifying resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic-aromatic petroleum resins (such as styrene-olefin copolymers), aliphatic-alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins. Examples of aliphatic hydrocarbon resins include polymers of one or more aliphatic hydrocarbons selected from olefins and dienes with approximately 4 to 5 carbon atoms. Examples of olefins include 1-butene, isobutylene, and 1-pentene. Examples of dienes include butadiene, 1,3-pentadiene, and isoprene.

[0058] Examples of aromatic hydrocarbon resins include polymers of vinyl group-containing aromatic hydrocarbons with approximately 8 to 10 carbon atoms (such as styrene, vinyltoluene, α-methylstyrene, indene, and methylindene).

[0059] Examples of aliphatic cyclic hydrocarbon resins include: alicyclic hydrocarbon resins obtained by cyclizing and then polymerizing so-called "C4 petroleum fractions" or "C5 petroleum fractions"; polymers of cyclic diene compounds (cyclopentadiene, dicyclopentadiene, ethylidene norbornene, dipentene, etc.) or their hydrogenated products; aromatic hydrocarbon resins or alicyclic hydrocarbon resins obtained by hydrogenating the aromatic ring of aliphatic-aromatic petroleum resins; and others.

[0060] The tackifying resin preferably has a softening point (softening temperature) of 80°C or higher (preferably 100°C or higher). Using such a tackifying resin tends to yield higher performance (e.g., adhesive) adhesives. There is no particular upper limit to the softening point of the tackifying resin; for example, it can be 200°C or lower (preferably 180°C or lower). The softening point of the tackifying resin referred to here shall be the value measured by the softening point test method (ring-ball method) specified in either JIS K 5902:2006 or JIS K 2207:2006.

[0061] The amount of tackifying resin used is not particularly limited and can be set appropriately according to the desired adhesive performance (adhesion strength, etc.). For example, based on solid content, it is preferable to use 10 to 100 parts by mass (preferably 15 to 80 parts by mass, more preferably 20 to 60 parts by mass) of tackifying resin per 100 parts by mass of acrylic polymer.

[0062] (2) Silicone-based adhesive In this specification, silicone-based adhesives mean adhesives that use a silicone polymer as the base polymer (the main component of the polymer components, i.e., the component that accounts for 50% or more by mass of the total polymer components). Examples of silicone-based adhesives include addition-reaction type silicone-based adhesives, peroxide-curing type silicone-based adhesives, and condensation-type silicone-based adhesives. From the viewpoint of not using peroxides in the curing reaction and not generating decomposition products, addition-reaction type silicone-based adhesives are preferred.

[0063] (Addition reaction type silicone adhesive) An addition-reaction type silicone adhesive is a silicone adhesive that contains an addition-reaction type silicone resin comprising a first polydimethylsiloxane having at least two alkenyl groups (such as vinyl, allyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, and octenyl monovalent hydrocarbon groups, with vinyl groups being particularly preferred) and a second polydimethylsiloxane having at least two hydrosilyl groups in one molecule, and a silicone resin.

[0064] The content of alkenyl groups in the first polydimethylsiloxane (the ratio of the number of alkenyl groups to the number of siloxane bonds) is preferably 0.01% to 10%, and more preferably 0.1% to 5%. The alkenyl groups are preferably present at least at both ends of the molecular chain, and more preferably at both ends and in the side chains. The degree of polymerization of the first polydimethylsiloxane (the number of siloxane bonds) is preferably 200 to 5,000, and more preferably 500 to 3,000. The weight-average molecular weight of the first polydimethylsiloxane is preferably 20,000 to 1,300,000, and more preferably 300,000 to 1,200,000.

[0065] In this specification, the molecular weight (weight-average molecular weight and number-average molecular weight) of polymers is the polystyrene-based value measured by gel permeation chromatography (GPC).

[0066] The hydrosilyl group content in the second polydimethylsiloxane is preferably 2 to 300 per molecule, and more preferably 4 to 200. The degree of polymerization (number of siloxane bonds) of the second polydimethylsiloxane is preferably 50 to 2,000, and more preferably 100 to 1,500.

[0067] In the addition-reaction type silicone resin, the ratio of the first polydimethylsiloxane to the second polydimethylsiloxane is preferably 0.01 to 20 parts by mass of the second polydimethylsiloxane per 100 parts by mass of the first polydimethylsiloxane, and more preferably 0.1 to 10 parts by mass.

[0068] When the content of alkenyl groups in the first polydimethylsiloxane, the content of hydrosilyl groups in the second polydimethylsiloxane, and the blending ratio of the second polydimethylsiloxane to the first polydimethylsiloxane are within the above ranges, the addition reaction between the first polydimethylsiloxane and the second polydimethylsiloxane tends to proceed smoothly. Preferably, the first polydimethylsiloxane does not have hydrosilyl groups, and preferably the second polydimethylsiloxane does not have alkenyl groups.

[0069] Silicone resin plays a role in imparting tackiness to silicone-based adhesives. In this specification, silicone resin means silicone having a three-dimensional network structure. Examples of silicone resins include monofunctional siloxane units [(CH3)3SiO 1 / 2 The M unit is [SiO], and the tetrafunctional siloxane unit is [SiO]. 4 / 2 It is composed of Q units, which are ] MQ resins are one example. In MQ resins, the molar ratio of M units to Q units (M units / Q units) is preferably 0.6 to 1.7.

[0070] In addition-reaction type silicone adhesives, the blending ratio of silicone resin to 100 parts by mass of addition-reaction type silicone resin is preferably 1 to 30 parts by mass, more preferably 3 to 20 parts by mass, and even more preferably 5 to 15 parts by mass. By having the blending ratio of silicone resin within this range, the release properties of the addition-reaction type silicone adhesive can be adjusted to a desirable range.

[0071] Addition-type silicone adhesives preferably contain a catalyst. The inclusion of a catalyst allows the curing reaction of the addition-type silicone resin to proceed more efficiently. The catalyst is not particularly limited as long as it can cause an addition reaction between the first polydimethylsiloxane and the second polydimethylsiloxane, but compounds containing platinum group metals are particularly preferred. Examples of compounds containing platinum group metals include particulate platinum, particulate platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complexes of chloroplatinic acid, palladium, and rhodium.

[0072] When an addition-type silicone adhesive contains a catalyst, the amount of catalyst blended per 100 parts by mass of the addition-type silicone resin (or, if the catalyst is a compound containing a platinum group metal, the amount equivalent to the platinum group metal) is preferably 0.0001 parts by mass to 0.1 parts by mass, and more preferably 0.001 parts by mass to 0.01 parts by mass.

[0073] (Peroxide-curing silicone adhesives and condensation-type silicone adhesives) Peroxide-curing silicone adhesives are generally adhesives that produce silicone polymers by curing (crosslinking) organopolysiloxanes with peroxides. Condensation-type silicone adhesives are generally adhesives that produce silicone polymers by dehydration or dealcoholization reactions between polyorganosiloxanes having hydrolyzable silyl groups such as silanol groups or alkoxysilyl groups at their ends.

[0074] In the case of peroxide-curing silicone adhesives, silicone rubber having at least methyl groups is used, and in the case of condensation-type silicone adhesives, silicone rubber having silanol groups or hydrolyzable alkoxysilyl groups at the ends is used. The weight-average molecular weight of organopolysiloxane in silicone rubber is usually 150,000 or more, preferably 280,000 to 1,000,000, and more preferably 500,000 to 900,000.

[0075] Silicone-based adhesives may contain various additives in addition to polymer components, such as reaction inhibitors and adhesion enhancers.

[0076] The method for forming an adhesive layer on a substrate layer using a silicone-based adhesive is not particularly limited. For example, it can be formed by applying a silicone-based adhesive to the substrate layer, drying it as needed, and curing it. This application can be done using a coating machine such as a bar coater, die coater, gravure coater, roll coater, or knife coater.

[0077] When a silicone-based adhesive contains a diluent, the diluent is not particularly limited. Examples include hydrocarbon compounds such as toluene, hexane, and heptane, as well as acetone, ethyl acetate, methyl ethyl ketone, and methyl isobutyl ketone. The diluent contained in the silicone-based adhesive may be a single type or two or more types.

[0078] When the silicone adhesive is an addition-reaction type silicone adhesive, it is preferable to apply the addition-reaction type silicone adhesive to the substrate layer and then heat it to cure it. In this case, the heating temperature is preferably 80°C to 180°C, and the heating time is preferably about 10 to 90 seconds.

[0079] (3) Rubber-based adhesive In this specification, "rubber-based adhesive" means an adhesive that uses a rubber-based polymer as its base polymer. The rubber-based polymer is not particularly limited and may be a natural rubber-based polymer (including modified natural rubber-based polymers) or a synthetic rubber-based polymer. Examples of synthetic rubber-based polymers include ABA-type or AB-type block copolymers (where A represents a thermoplastic block and B represents a rubber block; examples include styrene-isoprene-styrene copolymer (SIS), styrene-butadiene-styrene copolymer (SBS), etc.). The rubber-based polymer may also be a combination of a natural rubber-based polymer and a synthetic rubber-based polymer.

[0080] When a rubber-based adhesive contains a synthetic rubber polymer, examples of synthetic rubber polymers include polybutadiene, polyisoprene, butyl rubber, polyisobutylene, styrene-butadiene rubber (SBR), styrene-butadiene-styrene block copolymer (SBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and styrene-isoprene-styrene block copolymer (SIS).

[0081] When a rubber-based adhesive contains a modified natural rubber polymer, it is preferable that the modified natural rubber polymer has a structural component derived from natural rubber, with 50% or more (for example, 60% or more) by mass being natural rubber. Examples of modified natural rubber polymers include grafted modified natural rubber polymers, which are obtained by grafting other monomers onto a natural rubber polymer. Examples of monomers to be grafted onto the natural rubber polymer include acrylic monomers (monomers having an acryloyl group or a methacryloyl group), styrene, and the like. The monomers grafted onto the natural rubber polymer may be one type or two or more types.

[0082] Examples of acrylic monomers to be grafted onto natural rubber polymers include alkyl acrylates (for example, alkyl acrylates with 1 to 16 carbon atoms in the alkyl group, such as methyl acrylate, ethyl acrylate, isopropyl acrylate, and t-butyl acrylate), alkyl methacrylates (for example, alkyl methacrylates with 1 to 16 carbon atoms in the alkyl group, such as methyl methacrylate (MMA), ethyl methacrylate, isopropyl methacrylate, and t-butyl methacrylate), acrylic acid, and methacrylic acid. As the modified natural rubber polymer, it is preferable that 50% or more by mass of the monomers grafted onto the natural rubber polymer are acrylic monomers (acrylic-modified natural rubber polymer).

[0083] When the base polymer of a rubber-based adhesive is a natural rubber polymer, it is preferable that the natural rubber polymer has a Mooney viscosity of approximately 10 to 60 under the measurement conditions of MS(1+4)100℃ (using an L-type rotor, preheating for 1 minute, viscosity measurement time for 4 minutes, test temperature 100℃). In another embodiment, an acrylic-modified natural rubber polymer (NR-MMA graft copolymer) is preferred, which is obtained by grafting methyl methacrylate (MMA) onto a natural rubber polymer. Such graft copolymers can be manufactured by conventional methods and are also available commercially. The grafting rate of MMA in the NR-MMA graft copolymer (expressed as mass of MMA bonded to natural rubber / mass of natural rubber used for grafting × 100 (%), and is usually equivalent to the value calculated from the mass ratio of natural rubber to MMA used in the production of the NR-MMA graft copolymer) can be, for example, 1% to 120%, preferably 5% to 100%, more preferably 10% to 90%, and even more preferably 30% to 80%. The grafting rate is preferably 50% to 90%, more preferably 60% to 80%. If the grafting rate is 1% or higher, excessively high adhesive strength is suppressed, and if the grafting rate is 120% or lower, excessively low adhesive strength to the adherend such as a SUS plate is suppressed. In the production of the NR-MMA graft copolymer, a portion of the MMA (for example, 5% by mass or less, typically 3% by mass or less of the total monomer grafted onto the natural rubber) may be replaced with other monomers.

[0084] Rubber-based adhesives may contain other polymers (hereinafter also referred to as subpolymers) in addition to the base polymer. Examples of subpolymers include acrylic polymers, polyester polymers, polyurethane polymers, and silicone polymers, which can serve as base polymers for known acrylic adhesives, polyester adhesives, polyurethane adhesives, and silicone adhesives. Alternatively, any rubber-based polymer other than the base polymer may be used. The subpolymers contained in the rubber-based adhesive may be one type or two or more types. Examples of combinations of base polymers and subpolymers include a combination of a natural rubber-based polymer as the base polymer and an NR-MMA graft copolymer as the subpolymer, and a combination of an NR-MMA graft copolymer as the base polymer and a natural rubber-based polymer as the subpolymer.

[0085] When a rubber-based adhesive contains a base polymer and a subpolymer, the subpolymer is used in an amount of 100 parts by mass or less per 100 parts by mass of the base polymer (the total amount if there are two or more types of subpolymers). Typically, it is appropriate to use 70 parts by mass or less of the subpolymer per 100 parts by mass of the base polymer, and preferably 50 parts by mass or less. The rubber-based adhesive may also be substantially free of subpolymers (i.e., substantially 100% by mass of the polymer component is the base polymer). Furthermore, the rubber-based adhesive may be substantially free of polymer components other than the rubber-based polymer (for example, a rubber-based adhesive substantially free of polymer components other than natural rubber and modified natural rubber).

[0086] Rubber-based adhesives may contain a tackifier in addition to the polymer component. In particular, if the polymer component includes a natural rubber polymer with low tackiness on its own, the inclusion of a tackifier makes it possible to exhibit high tackiness to many types of adherends. When a rubber-based adhesive contains a tackifier, examples of tackifiers include those exemplified as tackifying resins that may be included in acrylic adhesives.

[0087] When a rubber-based adhesive contains a polymer component and a tackifier, the amount of tackifier used (the total amount if there are two or more types of tackifiers) can be, for example, 20 to 150 parts by mass (preferably 30 to 100 parts by mass) per 100 parts by mass of the polymer component. When the amount of tackifier used is 20 parts by mass or more, sufficient adhesion to the adherend such as a lead frame tends to be obtained. On the other hand, when the amount of tackifier used is 150 parts by mass or less, sufficient adhesion to the adherend such as a lead frame (especially adhesion in low-temperature environments) tends to be obtained.

[0088] The method for applying the rubber-based adhesive to the substrate layer is not particularly limited. For example, known methods such as a method of directly forming an adhesive layer on the substrate layer by applying an adhesive composition, in which components that will become a rubber-based adhesive are dissolved or dispersed in a suitable medium, to the substrate layer and drying it, or a method of transferring an adhesive layer formed on a peelable surface to the substrate layer can be appropriately employed. The adhesive composition can be prepared, for example, by mixing a polymer component, typically a tackifier, other components used as needed, and the above-mentioned medium by conventional methods.

[0089] Rubber-based adhesives may contain vulcanization accelerators as needed. Examples of vulcanization accelerators include dithiocarbamates (sodium dimethyldithiocarbamate, sodium diethyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, etc.), thiazoles (2-mercaptobenzothiazole, dibenzothiadyl disulfide, etc.), guanidines (diphenylguanidine, di-o-tolylguanidine, etc.), and sulfenamides (benzothiadyl-2-diethylsulfenamide, N-cyclohexyl-2-benzothiadylsulfenamide) Examples of vulcanization accelerators used include phenamides, thirams (tetramethylthiram monosulfide, tetramethylthiram disulfide, etc.), xanthogenic acids (sodium isopropylxanthogenic acid, zinc isopropylxanthogenic acid, etc.), ammonium aldehydes (ammonium acetaldehyde, hexamethylenetetramine, etc.), aldehyde amines (n-butyraldehyde aniline, butyraldehyde monobutylamine, etc.), and thioureas (diethylthiourea, trimethylthiourea, etc.). The vulcanization accelerator contained in the rubber-based adhesive may be one type alone or two or more types. For example, dithiocarbamic acids and thirams may be used in combination. The amount of vulcanization accelerator used can be, for example, 0.1 to 10 parts by mass (preferably 0.5 to 5 parts by mass) per 100 parts by mass of polymer component.

[0090] Rubber-based adhesives may contain crosslinking agents as needed. Examples of crosslinking agents include isocyanate compounds, sulfur, sulfur-containing compounds, phenolic resins, and organometallic compounds. As the crosslinking agent, isocyanate compounds are preferred, and bifunctional or more functional isocyanate compounds are more preferred. Examples of isocyanate compounds with two or more functions include: lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic diisocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate; and isocyanate adducts such as trimethylolpropane / tolylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate L"), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate HL"), and isocyanurate derivative of hexamethylene diisocyanate (manufactured by Nippon Polyurethane Industry Co., Ltd., trade name "Coronate HX"). The crosslinking agent contained in the rubber-based adhesive may be one type or two or more types. The amount of crosslinking agent used (in the case of an isocyanate compound) is preferably 0.3 to 10 parts by mass (for example, 0.5 to 5 parts by mass) per 100 parts by mass of polymer component.

[0091] The rubber-based adhesive may contain a vulcanization accelerator as needed. Examples of vulcanization accelerators include zinc stearate. By using a vulcanization accelerator, the vulcanization accelerator can be activated and the vulcanization efficiency can be promoted. When a vulcanization accelerator is included, the amount used can be, for example, 0.1 to 10 parts by mass (preferably 0.5 to 5 parts by mass) per 100 parts by mass of the polymer component.

[0092] Rubber-based adhesives may contain additives as needed. Examples of additives include softeners, flame retardants, antistatic agents, light stabilizers (radical scavengers, UV absorbers, etc.), and antioxidants.

[0093] (4) Urethane adhesive In this specification, urethane adhesives refer to adhesives that use a urethane polymer as the base polymer. Examples of urethane polymers include polymers obtained by reacting a polyol with a polyisocyanate compound, and terminal isocyanate group-containing urethane prepolymers (hereinafter referred to as "terminal NCO prepolymers") obtained by reacting a polyol with an excess amount of a polyisocyanate compound are preferred. Terminal NCO prepolymers can be synthesized by reacting various polyols with an excess amount of a polyisocyanate compound, for example, such that the equivalent ratio of OH to NCO (number of OH groups / number of NCO groups) is 1 / 1.2 to 3.5. The reaction can be carried out in the presence of a suitable reaction catalyst as needed (such as an organotin catalyst like dibutyltin dilaurate, a bismuth catalyst like bismuth octylate, or a tertiary amine catalyst like 1,4-diaza[2.2.2]bicyclooctane), for example, at 20°C to 90°C (preferably 60°C to 90°C) for 1 to 7 hours.

[0094] The content of terminal isocyanate groups (NCOs) in the terminal NCO prepolymer is preferably 0.2% to 15.0% by mass, and more preferably 0.5% to 3.5% by mass, from the viewpoint of storage stability of the prepolymer and flexibility of the cured product. The number-average molecular weight of the terminal NCO prepolymer is usually 3,000 to 50,000, and preferably 4,000 to 30,000 from the viewpoint of handling.

[0095] Examples of polyols include polyether polyols obtained by addition polymerization of polyhydric alcohols such as ethylene glycol, propylene glycol, glycerin, trimethylolpropane, pentaerythritol, sorbitol, and sucrose with propylene oxide or propylene oxide and alkylene oxide such as ethylene oxide; ethylene glycol, propylene glycol and their oligoglycols; butylene glycol, hexylene glycol, and polytetramethylene ether glycol; polycaprolactone polyols; polyester polyols such as polyethylene adipate; polybutadiene polyols; higher fatty acid esters having hydroxyl groups such as castor oil; and polymer polyols obtained by grafting vinyl monomers onto polyether polyols or polyester polyols. The polyol used in the synthesis of urethane polymers may be a single type or two or more types.

[0096] The polyol may be a polymer. If the polyol is a polymer, its number-average molecular weight is preferably 500 to 20,000, and more preferably 1,000 to 20,000, from the viewpoint of reactivity and workability. From the viewpoint of foam suppression, workability, curability, and stability of physical properties, and especially from the viewpoint of obtaining an excellent balance of these properties when combined with specific curing catalysts described later, the polyol is preferably a polyoxyalkylene polyol as an adduct of propylene oxide or a polyoxyalkylene polyol as an adduct of propylene oxide and ethylene oxide. From the viewpoint of practicality, a polyoxyalkylene polyol as an adduct of propylene oxide (i.e., polypropylene polyol) is more preferable, and polypropylene glycol is even more preferable.

[0097] The polyol may also be a rosin diol. Using a rosin diol improves the adhesive strength of the adhesive. A rosin diol is a diol that has two rosin skeletons and two hydroxyl groups in its molecule. Examples of rosin diols include rosin esters obtained by reacting rosin with polyhydric alcohols, and reaction products of rosin with bisphenol A diglycidyl ether, etc. These rosin diols can be produced by conventionally known methods. Among rosin diols, those having a polyoxyalkylene skeleton are preferred from the viewpoint of compatibility with NCO-terminated prepolymers. Examples of commercially available rosin diols having a polyoxyalkylene skeleton include Pine Crystal D-6011, KE-615-3, and D-6250 (all manufactured by Arakawa Chemical Industries, Ltd.).

[0098] Rosin diol is preferably used in combination with other polyols. Polypropylene glycol is a preferred other polyol. When rosin diol is used in combination with other polyols, the amount of rosin diol used is preferably 50% by mass or less of the total polyol amount, more preferably 2% to 30% by mass, and even more preferably 3% to 15% by mass, from the viewpoint of the properties after curing.

[0099] The polyol may be a polyfunctional polyol. For example, using a polyfunctional polyol with four or more functions (preferably four to eight functions) results in better adhesive strength (peel strength) after curing of the adhesive.

[0100] Examples of polyfunctional polyols include tetraols (pentaerythritol, diglycerin, etc.), pentaols (triglycerin, galactose, etc.), hexaols (dipentaerythritol, sorbitol, etc.), heptaols, octaols (tripentaerythritol, sucrose, etc.), and those obtained by adding ethylene oxide, propylene oxide, etc., to these polyfunctional polyols. From the viewpoint of versatility and effectiveness, alkoxide adducts of pentaerythritol are preferred. These polyfunctional polyols can be manufactured by conventionally known methods and are also available as commercial products. Examples of commercially available polyfunctional polyols include EL-410NE (Asahi Glass Co., Ltd.) and POLYPL 4525 (Perstorp Specialty Chemicals AB).

[0101] The polyfunctional polyol may be a polymer. When the polyfunctional polyol is a polymer, its number-average molecular weight is usually 100 to 2,000, and preferably 300 to 700 from the viewpoint of properties and reactivity.

[0102] It is preferable to use polyfunctional polyols in combination with other polyols. Among the other polyols, polypropylene glycol is preferred, and a combination of polypropylene glycol and rosin diol is more preferred. When polyfunctional polyols are used in combination with other polyols, from the viewpoint of the flexibility of the cured product (adhesive), the amount of polyfunctional polyol used is preferably such that the number of hydroxyl groups in the polyfunctional polyol is 60% or less of the total number of hydroxyl groups in the polyol, and more preferably 5% to 20%.

[0103] The polyisocyanate compound is not particularly limited and may be any compound belonging to the aromatic, aliphatic, or alicyclic groups. Specifically, examples include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 1,4-phenylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, naphthylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, crude TDI, polymethylene polyphenyl isocyanate, isophorone diisocyanate (IPDI), hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, etc. Furthermore, isocyanurates, carbodiimides, biuretides, etc., of these polyisocyanate compounds may also be used. The polyisocyanate compound used in the synthesis of the urethane polymer may be a single compound or two or more compounds. In particular, IPDI is preferred from the viewpoint of prepolymer properties, flexibility after curing, non-yellowing, and safety.

[0104] The polyisocyanate compound preferably contains a polyfunctional polyisocyanate with three or more functions (preferably three to six functions). Using a polyfunctional polyisocyanate with three or more functions results in superior adhesive strength (peel strength) after curing of the adhesive. Commercially available polyfunctional polyisocyanates include Coronate HX (alicyclic polyisocyanate, Nippon Polyurethane Industries Co., Ltd.), Takenate D-170N (alicyclic polyisocyanate, Takeda Pharmaceutical Company Limited), Sumijoule N-3500 (aliphatic polyisocyanate, Sumika Bayer Urethane Co., Ltd.), Sumijoule N-3200 (aliphatic polyisocyanate, Sumika Bayer Urethane Co., Ltd.), Duranate 24A-100 and Duranate E-405-80T (Asahi Kasei Chemicals Corporation), and others.

[0105] It is preferable to use the polyfunctional polyisocyanate compound in combination with other polyisocyanate compounds. IPDI is a preferred other polyisocyanate compound. When using the polyfunctional polyisocyanate compound in combination with other polyisocyanate compounds, the amount of the polyfunctional polyisocyanate compound used is preferably such that the number of NCO groups in the polyfunctional polyisocyanate compound is 60% or less of the total number of NCO groups in the polyisocyanate compound, and more preferably 5% to 20%, from the viewpoint of the properties after the reaction.

[0106] The terminal NCO prepolymer can be obtained by reacting a polyol with an excess amount of polyisocyanate compound and a monool, if necessary. In this case, the adhesive strength (peel strength) after curing of the adhesive is improved.

[0107] Examples of monools include polyoxyalkylene monools, polyester monools, polyether / ester monools, higher saturated monools, and monools having ethylenically unsaturated double bonds. When using monools, one type may be used alone or two or more types may be used.

[0108] Examples of polyoxyalkylene monools include high molecular weight polyoxyalkylene monools containing one hydroxyl group in the molecule, which are produced by ring-opening addition polymerization of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran, using an alkyl compound containing one active hydrogen as an initiator. Examples of polyester monools include alkylated modified products of known polyester polyols, lactone-based polyester monools obtained by ring-opening addition copolymerization or esterification reactions of cyclic lactone compounds using a monohydroxy compound as an initiator, and ester monools obtained from polyhydric alcohols and saturated fatty acids or (meth)acrylic acid, cinnamic acid, or higher unsaturated fatty acids with 10 or more carbon atoms such as oleic acid, linoleic acid, and linolenic acid, which have ethylenically unsaturated double bonds. Examples of polyether ester monools include polyoxyalkylene fatty acid ester monools, which are obtained by addition polymerization of the (mono)alkylene oxide to a fatty acid ester monool. Examples of higher saturated monools include linear, monohydric higher saturated alcohols with 10 or more carbon atoms, such as lauryl alcohol, myristyl alcohol, cetyl alcohol, and stearyl alcohol. Examples of monools having an ethylenically unsaturated double bond include oleyl alcohol, linoleyl alcohol, linolennyl alcohol, and other linear, monohydric higher unsaturated alcohols with 10 or more carbon atoms, as well as allyl alcohols. In particular, from the viewpoint of versatility and safety, polyoxyalkylene monools are preferred, and polyoxypropylene alkyl ethers are more preferred. The monool may be a polymer. If the monool is a polymer, its number-average molecular weight may be, for example, 100 to 10,000, and is preferably 500 to 10,000 from the viewpoint of versatility and handling. Examples of commercially available monool polymers include PML-S1004F (Asahi Glass Co., Ltd.). When using a polymer monool, the amount used is preferably 5% to 50% by mass, and more preferably 5% to 30% by mass, relative to the total amount of polyol, from the viewpoint of performance after curing.

[0109] The urethane adhesive may contain a tackifier as needed. The tackifier is not particularly limited as long as it can impart tackiness to the urethane adhesive or improve its tackiness. Examples of tackifiers include the tackifying resins mentioned above, which may be included in the acrylic adhesive.

[0110] When a urethane-based adhesive contains a tackifier, its content is preferably 10% to 60% by mass of the total amount of the adhesive composition, and more preferably 10% to 50% by mass, from the viewpoint of balancing the physical properties and performance after curing.

[0111] Urethane-based adhesives may contain reactive monofunctional compounds as needed. The inclusion of reactive monofunctional compounds improves the adhesive strength (peel strength) of the adhesive after curing.

[0112] The reactive monofunctional compound is not particularly limited as long as it is a monofunctional compound that is reactive in the urethane reaction and can improve the adhesive strength (peel strength) of the adhesive after curing. Specifically, examples of monools that may be used in the synthesis of terminal NCO prepolymers include the monools mentioned above, monofunctional isocyanate compounds (such as reaction products of monools and diisocyanates), and other monofunctional compositions that can undergo urethane reactions (such as amines, amides, thiols, carboxylic acids, etc.). The reactive monofunctional compound used may be a single compound or two or more. From the viewpoint of safety and versatility, monofunctional isocyanate compounds are preferred, and reaction products of monools and diisocyanates are more preferred. An example of a reaction product of monools and diisocyanates is Bayer's trade name "Additive TI".

[0113] When a urethane-based adhesive contains a reactive monofunctional compound, the amount used is preferably 5% to 50% by mass of the total amount of the adhesive, and more preferably 5% to 30% by mass, from the viewpoint of performance after curing.

[0114] Urethane adhesives may contain additives as needed. Examples of additives include urethane catalysts, plasticizers (acrylic acid ester plasticizers, phthalate diesters, epoxidized hexahydrophthalate diesters, alkylenedicarboxylic acid diesters, alkylbenzenes, etc.), fillers (heavy calcium carbonate, fatty acid treated calcium carbonate, fumed silica, precipitated silica, carbon black, talc, titanium dioxide, balloons, beads, etc.), antioxidants (hindered phenols, etc.), flame retardants, thixotropy-inducing agents (colloidal silica, organic bentonite, fatty acid amides, polyamide waxes, hydrogenated castor oil, etc.), ultraviolet absorbers (benzotriazoles, hindered amines, etc.), anti-aging agents (hindered phenols, mercaptans, sulfides, dithiocarboxylates, thioureas, thiophosphates, thioaldehydes, etc.), adhesion promoters (epoxy compounds, silane coupling agents, etc.), and dehydrating agents.

[0115] Examples of urethane catalysts include DBU-based catalysts, amine-based catalysts, metal salts of organic carboxylic acids, and imidazole-based catalysts. Examples of DBU-based catalysts include DBU[1,8-diazabicyclo(5,4,0)undecene-7], DBU phenol salt, DBU octylate, and DBU formate. Examples of amine-based catalysts include monoamines (triethylamine, etc.), diamines (N,N,N',N'-tetramethylethylenediamine, etc.), triamines (tetramethylguanidine, etc.), cyclic amines (triethylenediamine, etc.), alcohol amines (dimethylaminomethanol, etc.), and ether amines (bis(2-dimethylaminoethyl) ether, etc.). Examples of metal salts of organic carboxylic acids include Sn-based (dibutyltin dilaurate, tin octoate, etc.), Pb-based (lead octoate, etc.), and Zn-based (zinc octoate, etc.). Examples of imidazole-based catalysts include 2-methylimidazole and 1,2-dimethylimidazole.

[0116] The method for producing the urethane-based adhesive is not particularly limited. For example, it may be produced as a one-component urethane-based adhesive by mixing the polymer component contained in the urethane-based adhesive with other components as needed. The urethane-based adhesive may also be a solvent-free adhesive that is substantially free of solvents. If the urethane-based adhesive is substantially free of solvents, environmental pollution caused by the generation of odors, volatile organic compounds (VOCs), etc., when the adhesive is cured by heat can be suppressed.

[0117] The adhesive layer may contain anchoring enhancers, crosslinking accelerators, fillers, colorants, etc., as needed. For example, by including fillers in the adhesive layer, the outer surface of the adhesive layer (the side opposite to the conductive layer) is roughened, which improves the peelability from electronic components.

[0118] The material of the filler is not particularly limited and may be an organic substance such as a resin, an inorganic substance such as a metal or metal oxide, or a combination of organic and inorganic substances. Furthermore, the adhesive layer may contain only one type of filler or two or more types. The volume-average particle size of the filler is not particularly limited. For example, it can be selected from the range of 1 μm to 20 μm. In this specification, the volume-average particle size of the filler is the particle size (D50) at which the cumulative amount from the smallest diameter side in the volume-based particle size distribution measured by laser diffraction is 50%.

[0119] From the viewpoint of affinity with the adhesive contained in the adhesive layer, the filler is preferably a resin particle. Examples of resins that make up the resin particles include acrylic resin, olefin resin, styrene resin, acrylonitrile resin, and silicone resin. From the viewpoint of suppressing residue on the surface of the semiconductor package after molding, acrylic resin is preferred.

[0120] <Manufacturing method for semiconductor packages> The semiconductor package manufacturing method of this disclosure comprises the steps of sealing the area around an electronic component while the adhesive layer of the release film described above is in contact with at least a portion of the surface of the electronic component, and peeling the release film from the electronic component.

[0121] As described above, the release film of this disclosure exhibits excellent peelability from the surface of electronic components (especially surfaces with protrusions such as solder balls). Therefore, when the release film is peeled off, it is less likely to remain on areas with protrusions, and the condition of the protrusions on the surface of the electronic component is well maintained.

[0122] The types of electronic components used in the above method are not particularly limited. Examples include semiconductor elements, capacitors, terminals, etc. In the above method, the type of material (sealant) used to seal around the electronic components is not particularly limited. For example, a resin composition containing epoxy resin, acrylic resin, etc., can be used. [Examples]

[0123] The release film of this embodiment will be described below based on examples. However, this embodiment is not limited to the following examples.

[0124] <Example 1> A composition for forming an adhesive layer was prepared by mixing adhesive A (100 parts by mass), crosslinking agent A (17.4 parts by mass), filler (3 parts by mass), and a mixed solvent (34 parts by mass) with a toluene:methyl ethyl ketone mass ratio of 8:2, and stirring with a disperser. This composition for forming an adhesive layer was applied to the entire surface of one side of a substrate (PBT film with a thickness of 100 μm) so that the adhesive layer thickness was 20 μm, and the mixture was heated at 100°C for 1 minute to form an adhesive layer and produce a release film.

[0125] <Example 2> A composition for forming an adhesive layer was prepared by mixing adhesive A (100 parts by mass), crosslinking agent A (17.4 parts by mass), filler (3 parts by mass), and a mixed solvent (34 parts by mass) with a toluene:methyl ethyl ketone mass ratio of 8:2, and stirring with a disperser. This composition for forming an adhesive layer was applied to the entire surface of one side of a substrate (PBT film with a thickness of 100 μm) so that the adhesive layer thickness was 5 μm, and the mixture was heated at 100°C for 1 minute to form an adhesive layer and produce a release film.

[0126] <Example 3> A composition for forming an adhesive layer was prepared by mixing adhesive B (100 parts by mass), crosslinking agent B (10 parts by mass), and a mixed solvent (44 parts by mass) with a toluene:methyl ethyl ketone mass ratio of 8:2, and stirring with a disperser. This composition for forming an adhesive layer was applied to the entire surface of one side of a substrate (PET film with a thickness of 75 μm) so that the adhesive layer thickness was 25 μm, and the mixture was heated at 100°C for 1 minute to form an adhesive layer and produce a release film.

[0127] <Comparative Example 1> A composition for forming an adhesive layer was prepared by mixing adhesive B (100 parts by mass), crosslinking agent B (10 parts by mass), and a mixed solvent (44 parts by mass) with a toluene:methyl ethyl ketone mass ratio of 8:2, and stirring with a disperser. This composition for forming an adhesive layer was applied to the entire surface of one side of a substrate (PET film with a thickness of 38 μm) so that the adhesive layer thickness was 25 μm, and the mixture was heated at 100°C for 1 minute to form an adhesive layer and produce a release film.

[0128] <Comparative Example 2> A composition for forming an adhesive layer was prepared by mixing adhesive B (100 parts by mass), crosslinking agent B (10 parts by mass), and a mixed solvent (275 parts by mass) with a toluene:methyl ethyl ketone mass ratio of 8:2, and stirring with a disperser. This composition for forming an adhesive layer was applied to the entire surface of one side of a substrate (PET film with a thickness of 38 μm) so that the adhesive layer thickness was 3 μm, and the mixture was heated at 100°C for 1 minute to form an adhesive layer and produce a release film.

[0129] <Comparative Example 3> A composition for forming an adhesive layer was prepared by mixing adhesive B (100 parts by mass), crosslinking agent B (10 parts by mass), and a mixed solvent (275 parts by mass) with a toluene:methyl ethyl ketone mass ratio of 8:2, and stirring with a disperser. This composition for forming an adhesive layer was applied to the entire surface of one side of a substrate (PET film with a thickness of 75 μm) so that the adhesive layer thickness was 3 μm, and the mixture was heated at 100°C for 1 minute to form an adhesive layer and produce a release film.

[0130] Details of each material used in the production of the release film are as follows: • Adhesive A: Acrylic adhesive, product name "FS-1208", solid content 45% by mass, manufactured by Lion Special Chemicals Co., Ltd., composed of a mixture of multiple types of methacrylic acid ester monomers. • Adhesive B: Acrylic adhesive, trade name "S-43", solid content 24% by mass, manufactured by Soken Chemical Co., Ltd., composed of a mixed monomer of butyl acrylate (BA) and 4-hydroxybutyl acrylate (4HBA). • Crosslinking agent A: Product name "Duranate E405-80T", solid content 80% by mass, Asahi Kasei Chemicals Corporation, polyisocyanate-based crosslinking agent (hexamethylene diisocyanate crosslinking agent (HMDI)), number of isocyanate groups per molecule: 2 Crosslinking agent B: Product name "Coronate HL", solid content 75% by mass, Tosoh Corporation, 75% ethyl acetate solution of trimethylolpropane / hexamethylene diisocyanate trimer adduct, number of isocyanate groups per molecule: 3 • Filler: Cross-linked acrylic dispersed particles, product name "MX-500", volume average particle size 5 μm, Soken Chemical Co., Ltd.

[0131] <Evaluation Test> The release properties of the prepared release film on surfaces containing solder balls were evaluated using the following tests. Specifically, a release film adhesive layer was attached to the surface of the semiconductor chip containing solder balls (maximum height from the chip surface: 210 μm), and after transfer molding using a sealing material, the release film was peeled off. The condition was evaluated as "acceptable" if 50 μm or more of solder balls were exposed after peeling off the release film, and as "unacceptable" if 50 μm or more of solder balls were not exposed. The results are shown in Table 1. The condition where solder balls are exposed by 50 μm or more means that on the surface from which the release film has been peeled off, there is little deformation of the solder balls, little residue of the adhesive layer, and the tips of the solder balls protrude from the surface of the molded sealing material by a height of 50 μm or more.

[0132] [Table 1]

[0133] As shown in the results in Table 1, the release sheets in the examples where the adhesive layer thickness ratio was in the range of 4% to 30% and the base layer thickness was 75 μm or more showed good exposure of solder balls. The release sheets of Comparative Examples 1 and 2, in which the thickness of the base layer was less than 75 μm, and the release sheet of Comparative Example 3, in which the thickness of the base layer was 75 μm or more but the thickness ratio of the adhesive layer was outside the range of 4% to 30%, showed insufficient exposure of solder balls compared to the examples. [Explanation of Symbols]

[0134] 10: Adhesive layer, 20: Base material layer, 30: Release film

Claims

1. The release film comprises a base layer and an adhesive layer, wherein the thickness of the adhesive layer is 4% to 30% of the total thickness of the base layer and the adhesive layer, the thickness of the base layer is 75 μm or more, and the adhesive layer is a release film containing an acrylic adhesive and resin particles. A release film for use in a semiconductor package manufacturing method, comprising the steps of: sealing the area around an electronic component while the adhesive layer is in contact with at least a portion of the surface of the electronic component having solder balls; and peeling the release film from the electronic component.

2. The release film according to claim 1, wherein the resin particles are acrylic resin particles.

3. The release film according to claim 1 or claim 2, wherein the volume-average particle diameter of the resin particles is 1 μm to 20 μm.

4. A method for manufacturing a semiconductor package, comprising the steps of: sealing the area around an electronic component with the adhesive layer of the release film according to any one of claims 1 to 3 in contact with at least a portion of the surface of the electronic component having solder balls; and peeling the release film from the electronic component.

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