Releasing film and method for producing semiconductor package

Abstract

A release film includes a substrate layer and an adhesive layer, wherein the thickness of the adhesive layer is 4% to 30% of the total thickness of the substrate layer and the adhesive layer, and the thickness of the substrate layer is 75 μm or more.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing a release film and a semiconductor package. Prior Technology

[0002] In recent years, with the trend towards thinner electronic devices, especially mobile phones, there has been a growing demand for even thinner semiconductor packages for electronic components such as built-in semiconductor devices. Furthermore, from the perspective of improving heat dissipation, there is an increasing trend towards exposed die molding, which exposes a portion of the surface of the electronic component, instead of overmolding that uses sealing resin to cover the entire component.

[0003] When sealing electronic components in a way that exposes them as part of the electronic components, it is necessary to prevent the sealing material from leaking into the exposed portion of the electronic components (flash burr). Therefore, the following process is performed: sealing is performed with a release film (release film) attached to the exposed portion of the electronic components, and then the release film is peeled off to expose the surface of the electronic components. As such a release film, for example, Patent Document 1 describes a laminated film formed from a film comprising at least one single-area layer of a fluoropolymer resin in a substrate film comprising an extended polyester resin film. [Existing technical documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Application No. 2005-186740 Summary of the Invention

[0005] [The problem that the invention aims to solve] The release film described in Patent Document 1 does not have sufficient adhesion to the electronic components, and the sealing material may penetrate into the part with the release film attached during the sealing process. Furthermore, with the miniaturization of semiconductor packaging, the solder balls on electronic components also tend to be miniaturized. To prevent the solder balls from cracking, it is necessary to use sealing materials to protect a portion of the solder balls. As a result, a release film may be applied to the surface where the solder balls are formed.

[0006] When a release film is applied to a surface with protrusions resembling solder balls, the solder balls need to be fully exposed on the surface after the release film is peeled off. One aspect of this disclosure addresses the issue of providing a release film with excellent peelability relative to a surface having protrusions. Another aspect of this disclosure addresses the issue of providing a method for manufacturing a semiconductor package using the release film. [Methods for solving problems]

[0007] The means used to solve the aforementioned problem include the following implementations. <1> A release film includes a substrate layer and an adhesive layer, wherein the thickness of the adhesive layer is 4% to 30% of the total thickness of the substrate layer and the adhesive layer, and the thickness of the substrate layer is 75 μm or more. <2> like <1> The release film is used to expose at least a portion of the solder ball-shaped surface of the electronic component. <3> like <1> or <2> The release film, wherein the adhesive layer comprises an acrylic adhesive. <4> A method for manufacturing a semiconductor package includes: [The method is described in the original text, but the translation is incomplete and cannot be accurately translated.] <1> to <3> The steps of sealing the area around the electronic component while the adhesive layer of the release film in any one of the following states is in contact with at least a portion of the surface of the electronic component; and the steps of peeling the release film off the electronic component. <5> like <4> The method for manufacturing a semiconductor package, wherein at least a portion of the surface of the electronic component in contact with the adhesive layer has solder balls. [The effects of the invention]

[0008] According to one aspect of the present disclosure, a release film with excellent peelability relative to a surface having protrusions can be provided. According to another aspect of the present disclosure, a method for manufacturing a semiconductor package using the release film can be provided. Simple Explanation of the Diagram

[0009] Figure 1 is a schematic cross-sectional view showing an example of the structure of the release film disclosed herein. Implementation

[0010] The following provides a detailed description of the forms used to implement this disclosure. However, this disclosure is not limited to the following embodiments. In the following embodiments, structural elements (including element steps, etc.) are not necessary unless specifically stated otherwise. The numerical values ​​and their ranges are also the same and do not limit this disclosure.

[0011] In this disclosure, the term "step" includes not only steps that are independent of other steps, but also steps that achieve their purpose, even if they cannot be clearly distinguished from other steps. In this disclosure, the numerical range represented by "~" includes the values ​​before and after "~" as the minimum and maximum values, respectively. In the numerical ranges described in this disclosure in stages, the upper or lower limit value recorded in one numerical range can be replaced with the upper or lower limit value of the numerical range recorded in other stages. Additionally, in the numerical ranges described in this disclosure, the upper or lower limit value of the numerical range can be replaced with the value shown in the embodiments. In this disclosure, the percentage or content of each component in the composition, unless otherwise specified, refers to the total percentage or content of the multiple substances present in the composition when there are multiple substances equivalent to each component in the composition. In this disclosure, the particle size of each component in the composition, unless otherwise specified, refers to the value of a mixture of such multiple particles present in the composition, in the case where multiple particles corresponding to each component exist in the composition. In this disclosure, the term "layer" refers not only to the entirety of the region in which the layer exists, but also to a portion of the region in which the layer is formed. The thickness of the release film or the layers constituting the release film disclosed herein can be measured using known methods. For example, it can be measured using a micrometer or a cross-sectional image of the release film. Alternatively, the material constituting the layers can be removed using a solvent, and the thickness can be calculated based on the mass before and after removal, the density of the material, and the area of ​​the layer. Where the layer thickness is not constant, the arithmetic mean of the values ​​measured at any five points is taken as the layer thickness.

[0012] In this disclosure, "(meth)acrylic" refers to at least one of acrylonitrile and methacrylic, "(meth)acrylic" refers to at least one of acrylic acid and methacrylic acid, and "(meth)acrylate" refers to at least one of acrylate and methacrylate.

[0013] <Mold Release Film> The release film disclosed herein is as follows: it includes a substrate layer and an adhesive layer, wherein the thickness of the adhesive layer is 4% to 30% of the total thickness of the substrate layer and the adhesive layer, and the thickness of the substrate layer is 75 μm or more.

[0014] Even if solder balls-like protrusions are formed on the surface of electronic components, the release film is less prone to deformation of the protrusions or residue of the adhesive layer on the surface with protrusions. Therefore, the state of the protrusions after the release film is peeled off can be well maintained.

[0015] The release film disclosed herein will be described below with reference to the drawings, but this disclosure is not limited thereto. Furthermore, the sizes of the components shown in the drawings are conceptual sizes, and the relative sizes of the components are not limited thereto.

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

[0017] The release film disclosed herein is peeled off after a sealing process or similar treatment, in a state where the adhesive layer is side-attached to the surface of an object such as an electronic component. The release film disclosed herein exhibits excellent peelability relative to the surface with protrusions. Therefore, it can be preferably used, for example, in manufacturing methods utilizing exposed semiconductor packages, particularly in cases where at least a portion of the surface with protrusions of an electronic component is exposed.

[0018] (Substrate layer) The thickness of the substrate layer is 75 μm or more. By ensuring the substrate layer thickness is 75 μm or more, sufficient adhesion force can be achieved relative to the surface with the protrusion, suppressing the intrusion of the sealing material. The thickness of the substrate layer is preferably 80 μm or more, and more preferably 90 μm or more. There is no particular upper limit to the thickness of the substrate layer. For example, the thickness of the substrate layer can be 200 μm or less.

[0019] There are no particular restrictions on the material of the substrate layer. From the viewpoint of mold conformability, resin is preferred. Examples of resins include: polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyimide, polyamide, polyester ether, polyamide-imide, and fluoropolymers. When using a resin, it is preferable to have sufficient heat resistance to the heating temperature during the sealing process.

[0020] If necessary, treatments can be applied to the side of the substrate layer where the adhesive layer is located to improve the adhesion between the substrate and the adhesive layer. Examples of such treatments include surface treatments such as corona treatment and plasma treatment, and the application of a primer.

[0021] If necessary, a backing agent can be applied to the back side of the substrate layer (the side opposite to the adhesive layer) to adjust the self-rolling properties of the release film. Examples of backing agents include: silicone resin, fluorinated resin, polyvinyl alcohol, monomers such as alkyl resins, modifiers, and mixtures.

[0022] To suppress static electricity during the roll-out of the release film or the peeling off of the adhesive, an antistatic agent may be applied to the back of the substrate layer or the side where the adhesive layer is located, as needed. Examples of antistatic agents include: quaternary ammonium salts, pyridinium salts, cationic antistatic agents with cationic groups such as primary to tertiary amino groups, anionic antistatic agents with anionic groups such as sulfonate groups, sulfate groups, and phosphate groups, amphoteric antistatic agents such as amino acid-based and amino acid sulfate-based agents, nonionic antistatic agents with nonionic groups such as amino alcohol-based, glycerol-based, and polyethylene glycol-based agents, and polymeric antistatic agents that increase the molecular weight of these antistatic agents. These antistatic agents are also preferred in terms of good transparency.

[0023] (Adhesive layer) The thickness of the adhesive layer is 4% to 30% of the total thickness of the substrate layer and the adhesive layer. Hereinafter, the ratio of the thickness of the adhesive layer to the total thickness of the substrate layer and the adhesive layer will also be referred to as the "adhesive layer thickness ratio". By using an adhesive layer thickness ratio of 4% or more, sufficient adhesion to the protrusions can be achieved, suppressing the intrusion of sealing materials. On the other hand, by using an adhesive layer thickness ratio of 30% or less, the adhesive layer is less likely to remain on the surface with protrusions when the release film is peeled off, thus maintaining the condition of the protrusions well. The adhesive layer thickness ratio can be 4.8% to 25%.

[0024] Examples of adhesive layers include layers containing acrylic adhesives, silicone adhesives, rubber adhesives, and carbamate adhesives. The adhesive layer may contain a single type of adhesive or two or more types. The adhesive contained in the adhesive layer disclosed herein may react partially or completely, or it may not react at all. Furthermore, it may be in a state that hardens by heat, or it may be in a state that does not harden.

[0025] (1) Acrylic adhesives The acrylic adhesives mentioned in this disclosure refer to adhesives that use acrylic polymers as their base polymers. An acrylic polymer is defined as a polymer in which a monomer having at least one (meth)acrylic group in one molecule (hereinafter, sometimes referred to as "acrylic monomer") is the main constituent monomer (acrylic monomers accounting for more than 50% by mass of the total monomers constituting the acrylic polymer). Acrylic adhesives are advantageous in terms of transparency, weather resistance, heat resistance, and solvent resistance.

[0026] When designing acrylic polymers in acrylic adhesives, it is important to consider factors such as glass transfer point (adhesion relative to the adhered material, applicable temperature, etc.), introduction of crosslinking points (durability, heat resistance, etc.), and copolymerization properties of acrylic monomers (uniformity of molecular structure and crosslinking points of the acrylic polymer) to adjust the type and molecular weight of monomers. To introduce crosslinking points into the molecule, acrylic polymers are synthesized using monomers (acrylic acid, hydroxyethyl acrylate, etc.) containing functional groups capable of reacting with crosslinking agents used in combination.

[0027] Examples of acrylic polymers include those in which alkyl (meth)acrylates are the main constituent monomers. Alkyl (meth)acrylates are preferably represented by compounds according to formula (1). CH₂=C(R₁)COOR₂(1)

[0028] Here, R1 in formula (1) represents a hydrogen atom or a methyl group, and R2 represents an alkyl group with 1 to 20 carbon atoms (which can be either a chain alkyl group or an alicyclic alkyl group).

[0029] From the viewpoint of obtaining an adhesive with excellent adhesive properties, R2 is preferably a chain alkyl group with 2 to 14 carbon atoms (C2 to C14), which can be either a straight-chain alkyl group or a branched alkyl group. Examples of C2 to C14 chain alkyl groups include: ethyl, n-propyl, isopropyl, n-butyl, isobutyl, dibutyl, tributyl, n-pentyl, isopentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, isooctyl, 2-ethylhexyl, n-nonyl, isononyl, n-decyl, isodecyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, etc. Examples of alicyclic alkyl groups in the case where R2 is an alicyclic alkyl group include cyclohexyl, isobornyl, etc.

[0030] From the viewpoint of obtaining acrylic polymers with superior adhesive properties, the total amount of monomers used in the synthesis of acrylic polymers is preferably 50% by mass or more (e.g., 50% by mass to 99.9% by mass), more preferably 70% by mass or more (e.g., 70% by mass to 99.9% by mass), and even more preferably 85% by mass or more (e.g., 85% by mass to 99.9% by mass). It is more preferably (meth)acrylates in which R2 is a C2 to C14 chain alkyl group, more preferably acrylates in which R2 is a C4 to C10 chain alkyl group, and even more preferably 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 containing hydroxyl groups, those containing acrylic monomers with hydroxyl groups in the polymerization composition are preferred.

[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-hydroxylaurate (meth)acrylate, (4-hydroxymethylcyclohexyl)methacrylate, polypropylene glycol mono(meth)acrylate, N-hydroxyethyl(meth)acrylamide, N-hydroxypropyl(meth)acrylamide, etc. A single hydroxyl-containing acrylic monomer can be used alone, or two or more can be used in combination.

[0033] Among acrylic monomers containing hydroxyl groups, hydroxyl-containing (meth)acrylates are preferred. Preferably, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, and hydroxybutyl (meth)acrylate are also preferred.

[0034] For acrylic polymers containing hydroxyl groups, the proportion of hydroxyl-containing acrylic monomers in the total amount of monomers used for their synthesis can 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 even more preferably in the range of 0.1% to 10% by mass.

[0035] Acrylic polymers may also contain acrylic monomers with functional groups other than hydroxyl groups and monomers other than acrylic monomers (hereinafter also referred to as other monomers) as polymerization components. Other monomers may be used for purposes such as adjusting the Tg, adhesive properties, etc. of acrylic polymers. For example, monomers that can improve the cohesiveness and heat resistance of adhesives include: monomers containing sulfonic acid groups, monomers containing phosphate groups, monomers containing cyano groups, vinyl esters, aromatic vinyl compounds, etc. In addition, monomers that can introduce functional groups that can become crosslinking sites into acrylic polymers or can help improve adhesion include: monomers containing carboxyl groups, monomers containing acid anhydride groups, monomers containing amide groups, monomers containing amide groups, monomers containing amide imine groups, monomers containing epoxy groups, (meth)acrylic acid morpholine, vinyl ethers, etc. Other monomers may be used alone 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)acrylamide propanesulfonic acid, (meth)acrylate sulfonylpropyl ester, (meth)acryloxynaphthalene sulfonic acid, sodium vinyl sulfonate, etc. Examples of monomers containing phosphate groups include 2-hydroxyethylpropenyl phosphate. Examples of cyanide-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 styrene (chlorostyrene, chloromethylstyrene, α-methylstyrene, etc.).

[0037] Examples of monomers containing carboxyl groups include: acrylic acid, methacrylic acid, carboxyethyl methacrylate, carboxypentyl methacrylate, itaconic acid, maleic acid, fumaric acid, butenoic acid, isobutenoic acid, etc. Examples of monomers containing anhydride groups include: maleic anhydride, itaconic anhydride, and anhydrides of the aforementioned carboxyl-containing monomers. Examples of monomers containing the acrylamide group 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, diacetoneacrylamide, etc. Examples of monomers containing amine groups include: aminoethyl methacrylate, N,N-dimethylaminoethyl methacrylate, and N,N-dimethylaminopropyl methacrylate. Examples of monomers containing nimidyl groups include: cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, itaconimidide, etc. Examples of epoxy-containing monomers include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and allyl glycidyl ether. Examples of vinyl ethers include: methyl vinyl ether, ethyl vinyl ether, and isobutyl vinyl ether.

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

[0039] Acrylic polymers can also be those in which only acrylic monomers are used as polymerizing components. Examples of acrylic polymers in which only acrylic monomers are used as polymerizing components include acrylic polymers in which only alkyl (meth)acrylates with 6 to 14 carbon atoms are used as polymerizing components, and acrylic polymers in which only alkyl (meth)acrylates with 6 to 14 carbon atoms and hydroxyl-containing (meth)acrylates are used as polymerizing components.

[0040] The weight-average molecular weight (Mw) of the acrylic polymer, obtained by gel permeation chromatography (GPC) from standard polystyrene, can be, for example, 20 × 10⁴ or more, preferably 30 × 10⁴ or more. Alternatively, it can be, for example, 90 × 10⁴ or less, preferably 80 × 10⁴ or less. If the weight-average molecular weight of the acrylic polymer is within the aforementioned range, there is a tendency to obtain an adhesive exhibiting good adhesive properties.

[0041] Acrylic polymers can be random copolymers, block copolymers, or graft copolymers. From a production point of view, random copolymers are generally preferred.

[0042] The glass transition temperature (Tg) of the acrylic polymer is preferably below -15°C, more preferably below -25°C, and even more preferably below -40°C. Furthermore, the glass transition temperature (Tg) is preferably above -70°C. When the glass transition temperature (Tg) of the acrylic polymer is within the aforementioned range, there is a tendency to form an adhesive exhibiting good adhesive properties.

[0043] The Tg of acrylic polymers as described in this disclosure refers to a value calculated based on the Tg of the homopolymer of each monomer constituting the acrylic polymer, the mass fraction of that monomer (copolymerization ratio on a mass basis), and Fox's formula. Therefore, the Tg of acrylic polymers can be adjusted by appropriately changing the monomer composition (i.e., the types and proportions of monomers used in the synthesis of the acrylic polymer). Here, the Tg of the homopolymer is the value recorded in publicly available materials ("Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989)). Specifically, the following values ​​are used as the Tg of the homopolymer.

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

[0045] For homopolymers not described in the "Polymer Handbook", the Tg value is the value determined using the method described below. 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 were added to a reactor including a thermometer, a stirrer, a nitrogen inlet pipe, and a reflux cooling pipe. The mixture was stirred at room temperature (25°C) for 1 hour while nitrogen was flowing through it. After removing oxygen from the polymerization system, the temperature was raised to 63°C and the reaction was carried out for 10 hours. Then, the mixture was cooled to room temperature (25°C) to obtain a homopolymer solution with a solid content of 33% by mass. This homopolymer solution was then cast onto a release liner and dried to prepare a test sample (sheet homopolymer) approximately 2 mm thick. The test sample was stamped into a disc shape with a diameter of 7.9 mm and clamped in place using parallel plates. A viscoelasticity testing machine (ARES, Rheometrics) was used to apply a shear strain at a frequency of 1 Hz. The viscoelasticity was measured in shear mode at a temperature range of -70℃ to 150℃ and a heating rate of 5℃ / min. The peak temperature of tanδ was then set as the Tg of the homopolymer.

[0046] There are no particular limitations on the methods for synthesizing acrylic polymers; 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 solvent-based adhesive compositions containing acrylic polymers, solution polymerization is preferred. There are no particular limitations on the organic solvents (polymerization solvents) used in solution polymerization; examples include toluene, ethyl acetate, hexane, and cyclohexane. A single organic solvent or two or more solvents can be used.

[0047] The solvent-based adhesive composition disclosed herein refers to a composition containing an adhesive component in an organic solvent. There are no particular limitations on the organic solvent. Examples include toluene, xylene, ethyl acetate, hexane, cyclohexane, methylcyclohexane, and isopropyl alcohol. The organic solvent may be a single type or two or more. Preferably, the non-volatile component (NV) of the solvent-based adhesive composition is 30% to 60% by mass, more preferably 30% to 50% by mass. The viscosity of the solvent-based adhesive composition is preferably 3 Pa·s to 25 Pa·s, more preferably 5 Pa·s to 15 Pa·s. Furthermore, the viscosity refers to a value measured using a rotational viscometer at 23°C.

[0048] Acrylic adhesives can be designed by crosslinking acrylic polymers. Specific methods for crosslinking acrylic polymers include the following: Since the polymeric components of the acrylic polymer contain monomers with functional groups (hydroxyl, carboxyl, etc.) that can serve as crosslinking points, these functional groups are introduced into the acrylic polymer, and a compound (crosslinking agent) that can react with these functional groups to form a crosslinked structure is added to the acrylic polymer to carry out the reaction.

[0049] There are no particular limitations on the crosslinking agent; it can 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, among which epoxy and isocyanate crosslinking agents are preferred. The crosslinking agent used can be a single agent or two or more.

[0050] Examples of epoxy-based crosslinking agents include: N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidyl aniline, 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, and sorbitol polyglycidyl ether. Ethers, glycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether, trimethylolpropane polyglycidyl ether, diglycidyl adipate, diglycidyl o-phthalate, triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcinol diglycidyl ether, bisphenol-S-d-diglycidyl ether, and epoxy resins having two or more epoxy groups within the molecule, etc.

[0051] Examples of isocyanate-based crosslinking agents include: lower aliphatic polyisocyanate compounds such as 1,2-epoxyethyl diisocyanate, 1,4-epoxybutyl diisocyanate, and 1,6-hexamethylene diisocyanate; aliphatic polyisocyanate compounds such as epoxycyclopentyl diisocyanate, epoxycyclohexyl diisocyanate, isophorone diisocyanate, hydrogenated toluene diisocyanate, and hydrogenated xylene diisocyanate; and aromatic polyisocyanate compounds such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and phenylenediamine diisocyanate.

[0052] The amount of crosslinking agent used relative to 100 parts by weight of the acrylic polymer can be set to, for example, about 0.01 parts by weight to 15 parts by weight, preferably 0.1 parts by weight to 10 parts by weight (e.g., 0.2 parts by weight to 2 parts by weight). When the crosslinking agent is included in the above-mentioned amount, there is a tendency to obtain an adhesive that exhibits good adhesive properties.

[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 also include adhesive-improving resins as needed. There are no particular restrictions on the types of adhesive-improving resins, but examples include: rosin-based adhesive-improving resins, terpene-based adhesive-improving resins, hydrocarbon-based adhesive-improving resins, epoxy-based adhesive-improving resins, polyamide-based adhesive-improving resins, elastic adhesive-improving resins, phenol-based adhesive-improving resins, ketone-based adhesive-improving resins, etc. Acrylic adhesives may contain a single adhesive-improving resin or two or more.

[0055] As rosin-based adhesive resins, examples include: unmodified rosin such as rosin glue, rosin wood, and tall oil rosin (raw rosin); modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, rosin modified by other chemical methods, etc.) obtained by modifying unmodified rosin through hydrogenation, disproportionation, polymerization, etc.; and various other rosin derivatives. Examples of rosin derivatives include: rosin esters (formed by esterification of unmodified or modified rosin with alcohols); unmodified or modified rosin (formed by modification of unmodified or modified rosin with unsaturated fatty acids); rosin esters (formed by modification of rosin esters with unsaturated fatty acids); rosin alcohols (formed 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 aforementioned rosin derivatives (especially rosin esters); and rosin phenol resins obtained by adding phenol to unmodified rosin, modified rosin, and the aforementioned rosin derivatives using an acid catalyst and then performing thermal polymerization.

[0056] Examples of terpene-based adhesive resins include: α-pinene polymers, β-pinene polymers, and dipeptene polymers; and modified terpene resins, which are 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 adhesive 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. As aliphatic hydrocarbon resins, examples 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, isobutene, and 1-pentene. Examples of dienes include butadiene, 1,3-pentadiene, and isoprene.

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

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

[0060] The adhesive-imparting resin preferably has a softening point (softening temperature) of 80°C or higher (preferably 100°C or higher). By using such an adhesive-imparting resin, it is likely to obtain adhesives with higher performance (e.g., high adhesion). There is no particular upper limit to the softening point of the adhesive-imparting resin; for example, it can be set to 200°C or lower (preferably 180°C or lower). Furthermore, the softening point of the adhesive-imparting resin referred to herein is set as the value determined by the softening point test method (ring and ball method) specified in either Japanese Industrial Standards (JIS) K 5902:2006 or JIS K 2207:2006.

[0061] There is no particular limitation on the amount of adhesive-imparting resin used, and it can be appropriately set according to the desired adhesive properties (adhesion strength, etc.). For example, it is preferable to use the adhesive-imparting resin at a ratio of 10 parts by weight to 100 parts by weight (preferably 15 parts by weight to 80 parts by weight, more preferably 20 parts by weight to 60 parts by weight) relative to 100 parts by weight of acrylic polymer, based on the solid content.

[0062] (2) Silicone adhesives In this disclosure, silicone-based adhesives refer to adhesives in which a silicone polymer is set as the base polymer (the main component in the polymer composition, i.e., the component that accounts for more than 50% by mass of the total polymer composition). Examples of silicone-based adhesives include addition-reaction silicone adhesives, peroxide-cured silicone adhesives, and condensation-reaction silicone adhesives. From the viewpoint that no peroxide is used in the curing reaction and no decomposition products are generated, addition-reaction silicone adhesives are preferred.

[0063] (Addition-reaction silicone adhesive) The so-called addition-reaction silicone adhesive is a silicone adhesive containing addition-reaction silicone resin and silicone resin. The addition-reaction silicone resin includes a first polydimethylsiloxane having at least two alkenyl groups (such as vinyl, allyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, etc., with vinyl being particularly preferred) in one molecule, and a second polydimethylsiloxane having at least two hydrosilyl groups in one molecule.

[0064] The alkenyl group content (the ratio of the number of alkenyl groups to the number of siloxane bonds) in the first polydimethylsiloxane is preferably 0.01% to 10%, more preferably 0.1% to 5%. The alkenyl groups are preferably present at least at both ends of the molecular chain, more preferably at both ends and in the side chains. The degree of polymerization (the number of siloxane bonds) of the first polydimethylsiloxane is preferably 200 to 5,000, 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] The molecular weights (weight average and number average) of the polymers in this disclosure are converted values ​​from polystyrene determined using gel permeation chromatography (GPC).

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

[0067] In addition-reaction silicone resins, the ratio of the first polydimethylsiloxane to the second polydimethylsiloxane is preferably, for example, 0.01 to 20 parts by mass of the second polydimethylsiloxane relative to 100 parts by mass of the first polydimethylsiloxane, more preferably 0.1 to 10 parts by mass.

[0068] If the content of alkenyl groups in the first polydimethylsiloxane, the content of hydrosilyl groups in the second polydimethylsiloxane, and the mixing ratio of the second polydimethylsiloxane to the first polydimethylsiloxane are all within the aforementioned ranges, then there is a tendency for the addition reaction between the first and second polydimethylsiloxanes to proceed well. Furthermore, the first polydimethylsiloxane preferably does not contain hydrosilyl groups, and the second polydimethylsiloxane preferably does not contain alkenyl groups.

[0069] Silicone resins impart adhesive properties to silicone-based adhesives. In this disclosure, the term "silicone resin" refers to silicone with a three-dimensional mesh structure. Examples of silicone resins include MQ resins, which contain M units as monofunctional siloxane units [(CH3)3SiO1 / 2] and Q units as tetrafunctional siloxane units [SiO4 / 2]. The molar ratio (M unit / Q unit) of the M unit to the Q unit in the MQ resin is preferably 0.6 to 1.7.

[0070] In addition-reactive silicone adhesives, the proportion of silicone resin relative to 100 parts by weight of addition-reactive silicone resin is preferably 1 to 30 parts by weight, more preferably 3 to 20 parts by weight, and even more preferably 5 to 15 parts by weight. By maintaining the silicone resin proportion within the aforementioned range, the peelability of the addition-reactive silicone adhesive can be adjusted to an ideal range.

[0071] Addition-reaction silicone adhesives preferably contain a catalyst. By including a catalyst, the curing reaction of the addition-reaction silicone resin can be carried out more efficiently. The catalyst is not particularly limited as long as it enables the first polydimethylsiloxane and the second polydimethylsiloxane to undergo an addition reaction; however, compounds containing platinum group metals are preferred. Examples of compounds containing platinum group metals include: microparticle platinum, microparticle platinum adsorbed on a carbon powder carrier, chloroplatinic acid, alcohol-modified chloroplatinic acid, olefin complexes of chloroplatinic acid, palladium, rhodium, etc.

[0072] When the addition-reaction silicone adhesive contains a catalyst, the amount of catalyst (equivalent to the amount of platinum group metals if the catalyst is a platinum group metal compound) relative to 100 parts by weight of the addition-reaction silicone resin is preferably 0.0001 parts by weight to 0.1 parts by weight, more preferably 0.001 parts by weight to 0.01 parts by weight.

[0073] (Peroxide-cured silicone adhesives and condensation-type silicone adhesives) Peroxide-cured silicone adhesives are generally adhesives that use peroxides to harden (crosslink) organopolysiloxanes and form silicone polymers. Condensation-type silicone adhesives are generally adhesives that form silicone polymers through dehydration or de-alcoholization reactions between polyorganosiloxanes with hydrolyzable silanol or alkoxysilyl groups at the ends.

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

[0075] Silicone adhesives may contain polymer components, as well as various additives such as reaction inhibitors and adhesion enhancers.

[0076] There are no particular limitations on the method of forming an adhesive layer on a substrate layer using a silicone-based adhesive. For example, an adhesive layer can be formed by applying a silicone-based adhesive to a substrate layer and then drying and curing it as needed. This application can be performed using coating machines such as bar coaters, die coaters, gravure coaters, roller coaters, and doctor blade coaters.

[0077] When silicone-based adhesives contain diluents, there are no particular restrictions on the type of diluent. Examples include hydrocarbon compounds such as toluene, hexane, and heptane, as well as acetone, ethyl acetate, methyl ethyl ketone, and methyl isobutyl ketone. Silicone-based adhesives may contain a single diluent or two or more diluents.

[0078] When the silicone adhesive is an addition-reactive silicone adhesive, it is preferable to apply the addition-reactive silicone adhesive to the substrate layer and then heat it to harden it. In this case, the preferred heating temperature is 80°C to 180°C, and the preferred heating time is approximately 10 to 90 seconds.

[0079] (3) Rubber-based adhesives In this disclosure, rubber-based adhesives refer to adhesives that use a rubber-based polymer as the base polymer. There are no particular limitations on the rubber-based polymer; it can 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 (A represents the thermoplastic block, and B represents the rubber block. Examples include styrene-isoprene-styrene copolymers (SIS) and styrene-butadiene-styrene copolymers (SBS)). Rubber-based polymers can also be combinations of natural and synthetic rubber-based polymers.

[0080] When a rubber-based adhesive contains a synthetic rubber-based polymer, examples of synthetic rubber-based 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-based polymer, it is preferable that 50% or more (e.g., 60% or more by mass) of the modified natural rubber-based polymer is derived from the structural components of natural rubber. Examples of modified natural rubber-based polymers include grafted modified natural rubber-based polymers formed by grafting other monomers onto the natural rubber-based polymer. Examples of monomers grafted onto the natural rubber-based polymer include acrylic monomers (monomers having acrylonitrile or methacrylonitrile groups), styrene, etc. The monomer grafted onto the natural rubber-based polymer may be a single type or two or more types.

[0082] Examples of acrylic monomers grafted onto natural rubber-based polymers include: alkyl acrylates (e.g., alkyl acrylates with 1 to 16 carbon atoms such as methyl acrylate, ethyl acrylate, isopropyl acrylate, and tributyl acrylate), alkyl methacrylates (e.g., alkyl methacrylates with 1 to 16 carbon atoms such as methyl methacrylate (MMA), ethyl methacrylate, isopropyl methacrylate, and tributyl methacrylate), acrylic acid, and methacrylic acid. As a modified natural rubber polymer, it is preferable that the monomer grafted into the natural rubber polymer contains more than 50% by mass of acrylic monomers (acrylic acid modified natural rubber polymer).

[0083] When the base polymer of the rubber-based adhesive is a natural rubber-based polymer, the Mooney viscosity of the natural rubber-based polymer, for example, is preferably around 10 to 60 under the test conditions of MS(1+4) 100°C (using an L-shaped rotor, preheating for 1 minute, viscosity measurement time of 4 minutes, and test temperature of 100°C). In another embodiment, a preferred alternative is an acrylic-modified natural rubber polymer (NR-MMA graft copolymer) formed by grafting methyl methacrylate (MMA) onto a natural rubber-based polymer. The graft copolymer can be manufactured by conventional methods or is available as a commercially available product. The grafting rate of MMA in the NR-MMA graft copolymer (expressed as the mass of MMA bonded to the natural rubber / the mass of the natural rubber used for grafting × 100 (%), typically equivalent to a value calculated based on the mass ratio of natural rubber to MMA used in the manufacture of the NR-MMA graft copolymer) can be, for example, set to 1%~120%, preferably 5%~100%, more preferably 10%~90%, and even more preferably 30%~80%. The grafting rate is preferably 50%~90%, more preferably 60%~80%. If the grafting rate is above 1%, excessively high adhesion can be prevented; if the grafting rate is below 120%, excessively low adhesion relative to substrates such as SUS sheets can be prevented. A portion of the MMA used in the manufacture of the NR-MMA graft copolymer (e.g., less than 5% by mass of the monomer grafted onto natural rubber, typically less than 3% by mass) can be replaced with other monomers.

[0084] Rubber-based adhesives may contain other polymers (hereinafter also referred to as secondary polymers) in addition to the base polymer. Examples of secondary polymers include: acrylic polymers, polyester polymers, polyurethane polymers, and silicone polymers that are base polymers of well-known acrylic adhesives, polyester adhesives, polyurethane adhesives, silicone adhesives, etc. Alternatively, they may be polymers other than the base polymers in the aforementioned rubber-based polymers. The secondary polymers included in the rubber-based adhesive may be a single type or two or more. Examples of combinations of base polymers and secondary polymers include: combinations of natural rubber-based polymers as base polymers and NR-MMA graft copolymers as secondary polymers, and combinations of NR-MMA graft copolymers as base polymers and natural rubber-based polymers as secondary polymers.

[0085] When a rubber-based adhesive comprises a base polymer and auxiliary polymers, the auxiliary polymers may be used in an amount of 100 parts by weight or less relative to 100 parts by weight of the base polymer (or, in total, if there are two or more auxiliary polymers). It is generally appropriate to set the amount of auxiliary polymers used relative to 100 parts by weight of the base polymer to 70 parts by weight or less, and preferably to 50 parts by weight or less. Rubber-based adhesives may also substantially not contain auxiliary polymers (i.e., the polymer component is substantially 100% by weight of the base polymer). Furthermore, rubber-based adhesives may also be substantially free of polymer components other than rubber-based polymers (e.g., rubber-based adhesives substantially free of polymer components other than natural rubber and modified natural rubber).

[0086] Rubber-based adhesives may contain adhesive-improving agents in addition to polymer components. Particularly when the polymer component is a natural rubber-based polymer with inherently low tackiness, the inclusion of an adhesive-improving agent can enhance tackiness relative to a variety of adherends. Examples of adhesive-improving resins that can be included in acrylic adhesives include the following:

[0087] When a rubber-based adhesive comprises a polymer component and an adhesive agent, the amount of adhesive agent used (total if there are two or more adhesive agents) relative to 100 parts by weight of the polymer component can be set to, for example, 20 to 150 parts by weight (preferably 30 to 100 parts by weight). If the amount of adhesive agent used is 20 parts by weight or more, there is a tendency to obtain sufficient adhesion to the adhered object such as a lead frame. On the other hand, if the amount of adhesive agent used is 150 parts by weight or less, there is a tendency to obtain sufficient adhesion to the adhered object such as a lead frame (especially adhesion at low temperatures).

[0088] There are no particular limitations on the method of applying a rubber-based adhesive to a substrate layer. For example, suitable methods include: forming an adhesive layer directly on the substrate layer by applying an adhesive composition, which dissolves or disperses the components that constitute the rubber-based adhesive in a suitable medium, to the substrate layer and allowing it to dry; and transferring an adhesive layer formed on a peelable surface to the substrate layer, among other known methods. The adhesive composition can be prepared, for example, by conventional methods, by mixing a polymer component, typically an adhesive agent, other components as needed, and the medium.

[0089] Rubber adhesives may also contain vulcanization accelerators if required. As vulcanization accelerators, dithiocarbamates (sodium dimethyl dithiocarbamate, sodium diethyl dithiocarbamate, zinc dimethyl dithiocarbamate, zinc diethyl dithiocarbamate, etc.), thiazoles (2-mercaptobenzothiazole, dibenzothiazole disulfide, etc.), guanidines (diphenylguanidine, di-o-tolylguanidine, etc.), sulfenamides (benzothiazole-2-diethylsulfenamide, N-cyclohexyl-2-benzothiazole-sulfenamide, etc.), thiurams (tetramethylthiuram monosulfide, tetramethylthiuram disulfide, etc.), xanthic acid compounds (sodium isopropyl xanthate, zinc isopropyl xanthate, etc.), aldehydes and amines (acetaldehyde amine, hexamethylenetetramine, etc.), aldehydes and amines (n-butylaldehyde aniline, butylaldehyde monobutylamine, etc.), and thioureas (diethylthiourea, trimethylthiourea, etc.) can be used. The vulcanization accelerator contained in rubber-based adhesives may be a single type or two or more. For example, dithiocarbamate and thiuram derivatives may be used in combination. The amount of vulcanization accelerator used relative to 100 parts by weight of polymer content may be set to, for example, 0.1 parts by weight to 10 parts by weight (preferably 0.5 parts by weight to 5 parts by weight).

[0090] Rubber-based adhesives may also include crosslinking agents as needed. Examples of crosslinking agents include: isocyanate compounds, sulfur, sulfur-containing compounds, phenolic resins, organometallic compounds, etc. Isocyanate compounds are preferred as crosslinking agents, and more preferably difunctional or higher isocyanate compounds. Examples of isocyanate compounds with difunctionality or higher include: lower aliphatic polyisocyanates such as butyl diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentyl diisocyanate, cyclohexyl diisocyanate, and isophorone diisocyanate; aromatic diisocyanates such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and phenyl diisocyanate; and isocyanate adducts such as trimethylolpropane / toluene diisocyanate trimer adduct (manufactured by Polyurethane Industries, Ltd., Japan, trade name "Coronate L"), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Polyurethane Industries, Ltd., Japan, trade name "Coronate HL"), and isocyanurate esters of hexamethylene diisocyanate (manufactured by Polyurethane Industries, Ltd., Japan, trade name "Coronate HX"). The crosslinking agent contained in rubber-based adhesives may be a single type or two or more. The amount of crosslinking agent used (in the case of isocyanate compounds) relative to 100 parts by weight of the polymer component is preferably set at 0.3 to 10 parts by weight (e.g., 0.5 to 5 parts by weight).

[0091] Rubber-based adhesives may also include vulcanization accelerators as needed. Examples of vulcanization accelerators include zinc stearate. By using vulcanization accelerators, the vulcanization accelerators can be activated, thereby improving vulcanization efficiency. When vulcanization accelerators are included, the amount of vulcanization accelerator used per 100 parts by weight of polymer component can be set to, for example, 0.1 parts by weight to 10 parts by weight (preferably 0.5 parts by weight to 5 parts by weight).

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

[0093] (4) Carbamate adhesives In this disclosure, urethane-based adhesives refer to adhesives that use urethane polymers as the base polymer. Examples of urethane polymers include polymers obtained by reacting polyols with polyisocyanate compounds, and more preferably, urethane prepolymers containing terminal isocyanate groups (hereinafter referred to as "terminated NCO prepolymers") obtained by reacting polyols with an excess of polyisocyanate compound. The terminal NCO prepolymers can be synthesized by reacting various polyols with an excess of polyisocyanate compound, for example, with an OH to NCO equivalence ratio (number of OH groups / number of NCO groups) of 1 / 1.2 to 3.5. The reaction can be carried out as needed in the presence of a suitable reaction catalyst (organotin catalysts such as dibutyltin dilaurate, bismuth catalysts such as bismuth octanoate, tertiary amine catalysts such as 1,4-diaza[2.2.2]bicyclooctane, etc.), for example at 20°C to 90°C (preferably 60°C to 90°C) for 1 to 7 hours.

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

[0095] Examples of polyols include: polyether polyols synthesized by addition polymerization of propylene oxide or propylene oxide with ethylene oxide and other epoxides, or with polyhydric alcohols such as ethylene glycol, propylene glycol, glycerol, trimethylolpropane, pentaerythritol, sorbitol, and sucrose; oligomeric glycols of ethylene glycol, propylene glycol, and the like; butanediol, hexanediol, and polytetramethylene ether glycol; polycaprolactone polyols; polyester polyols such as poly(ethyl adipate); polybutadiene polyols; higher fatty acid esters containing hydroxyl groups such as castor oil; and polymer polyols synthesized by grafting vinyl monomers with polyether polyols or polyester polyols. Polyols used in the synthesis of carbamate polymers can be a single type or two or more.

[0096] Polyols can also be polymers. When polyols are polymers, from the viewpoint of reactivity and workability, their number average molecular weight is preferably 500 to 20,000, more preferably 1,000 to 20,000. From the viewpoint of suppressing foaming, workability, curing properties, and stability of physical properties, and especially from the viewpoint of achieving an excellent balance of these properties when combined with the 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, it is more preferably a polyoxyalkylene polyol as an adduct of propylene oxide (i.e., polyoxypropyl polyol), and even more preferably polypropylene glycol.

[0097] Polyols can also be rosin diol. Using rosin diol results in adhesives with superior adhesion. Rosin diol is a diol containing two rosin backbones and two hydroxyl groups within its molecule. Examples of rosin diols include rosin esters obtained by reacting rosin with polyols, and reaction products of rosin with bisphenol A diglycidyl ether, etc. These rosin diols can be manufactured by previously known methods. From the viewpoint of compatibility with NCO-terminated prepolymers, rosin glycols with a polyoxyalkylene backbone are preferred. Commercially available rosin glycols with a polyoxyalkylene backbone include: Pinecrystal D-6011, KE-615-3, and D-6250 (all from Arakawa Chemical Industry Co., Ltd.).

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

[0099] Polyols can also be multifunctional polyols. For example, by using multifunctional polyols with four or more functions (preferably four to eight functions), the adhesive exhibits superior adhesion (peel strength) after curing.

[0100] Examples of multifunctional polyols include: tetraols (pentaerythritol, diglycerol, etc.), pentaols (triglycerol, galactose, etc.), hexaols (dipentaerythritol, sorbitol, etc.), heptanoyl alcohols, octaols (tripentaerythritol, sucrose, etc.), and those formed by the addition of ethylene oxide, propylene oxide, etc. to these multifunctional polyols. From the viewpoint of versatility and effectiveness, alkoxide adducts of pentaerythritol are preferred. These multifunctional polyols can be manufactured by previously known methods and are also available as commercially available products. Examples of commercially available multifunctional polyols include: EL-410NE (Asahi Glass Co., Ltd.) and POLYPL 4525 (Perstorp Specialty Chemicals AB).

[0101] Polyfunctional polyols can also be polymers. When polyfunctional polyols are polymers, their number average molecular weight is usually 100 to 2,000, and from the viewpoint of properties and reactivity, it is preferably 300 to 700.

[0102] Multifunctional polyols are preferably used in combination with other polyols. Among these other polyols, polypropylene glycol is preferred, and a combination of polypropylene glycol and rosin glycol is more preferred. When multifunctional polyols are used in combination with other polyols, from the viewpoint of the flexibility of the cured material (adhesive), the amount of multifunctional polyol used is preferably such that the number of hydroxyl groups in the multifunctional polyol is less than 60% of the total number of hydroxyl groups in the polyol, and more preferably 5% to 20%.

[0103] There are no particular limitations on the polyisocyanate compounds; they can 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'-epimine diisocyanate, 1,4-phenylene diisocyanate, phenylene diisocyanate, tetramethylphenylene diisocyanate, naphthalene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, crude TDI, polymethylene-polyphenyl isocyanate, isophorone diisocyanate (IPDI), hexamethylene diisocyanate, hydrogenated phenylene diisocyanate, etc. Additionally, isocyanurate derivatives, carbodiimides, biuret derivatives, etc., of these polyisocyanate compounds can also be included. The polyisocyanate compound used in the synthesis of urethane polymers can be a single compound or two or more. Among them, IPDI is preferred from the viewpoints of prepolymer properties, curing flexibility, non-yellowing, and safety.

[0104] The polyisocyanate compound is preferably a multifunctional polyisocyanate containing three or more functions (preferably trifunctional to hexafunctional). By using multifunctional polyisocyanates with three or more functions, the adhesive exhibits superior adhesion (peel strength) after curing. Commercially available multifunctional polyisocyanates include: Coronate HX (alicyclic polyisocyanate, Nippon Polyurethanes Industries, Ltd.), Takenate D-170N (alicyclic polyisocyanate, Takeda Pharmaceutical Co., Ltd.), Sumidur N-3500 (alicyclic polyisocyanate, Sumitomo Chemical Bayer Polyurethanes Co., Ltd.), Sumidur N-3200 (alicyclic polyisocyanate, Sumitomo Chemical Bayer Polyurethanes Co., Ltd.), Duranate 24A-100, and Duranate E-405-80T (Asahi Kasei Chemicals Co., Ltd.), etc.

[0105] The polyfunctional polyisocyanate compound is preferably used in combination with other polyisocyanate compounds. IPDI is preferably used as one of the other polyisocyanate compounds. When the polyfunctional polyisocyanate compound is used in combination with other polyisocyanate compounds, from the viewpoint of the properties after the reaction, the amount of the polyfunctional polyisocyanate compound used is preferably such that the number of NCO groups in the polyfunctional polyisocyanate compound is less than 60% of the total number of NCO groups in the polyisocyanate compound, more preferably 5% to 20%.

[0106] Terminal NCO prepolymers can be obtained by reacting polyols, excess polyisocyanate compounds, and monools as needed. In this case, the cured adhesive exhibits superior adhesion (peel strength).

[0107] Examples of monools include: polyoxyalkylene monools, polyester monools, polyether-ester monools, higher saturated monools, and monools with vinyl unsaturated double bonds. When using monools, a single type or two or more may be used.

[0108] Examples of polyoxyalkylene monools include high-molecular-weight polyoxyalkylene monools containing a single hydroxyl group, which are produced by using alkyl compounds containing one active hydrogen as initiators to perform ring-opening addition polymerization on alkyl oxides such as ethylene oxide, propylene oxide, butane oxide, and tetrahydrofuran. Examples of polyester monools include: ester monools obtained by reacting lactone-based polyester monools, polyols, and saturated fatty acids or (meth)acrylic acid, cinnamic acid, or higher unsaturated fatty acids with more than 10 carbon atoms, such as oleic acid, linoleic acid, and alpha-linolenic acid, which have ethylene-like unsaturated double bonds. The lactone-based polyester monools and polyols are obtained by using alkylated modified products of known polyester polyols with terminal hydroxyl groups or monohydroxy compounds as initiators to carry out ring-opening addition copolymerization or esterification reactions of cyclic lactone compounds. Examples of polyether-ester monools include polyoxyalkyl fatty acid ester monools formed by the addition polymerization of the (mono)epoxide onto fatty acid ester monools. Examples of higher saturated monools include lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, and other straight-chain, monovalent higher saturated alcohols with more than 10 carbon atoms. Examples of monools with ethylene-like unsaturated double bonds include: oleyl alcohol, linolenic acid alcohol, hypolinolenic acid alcohol, and other straight-chain monovalent higher unsaturated alcohols with more than 10 carbon atoms, as well as allyl alcohols. From a general and safety perspective, polyoxyalkylene monools are preferred, and polyoxyalkylene propyl ethers are even more preferred. Monools can also be polymers. When monools are polymers, their number average molecular weight can be, for example, 100 to 10,000, but from the point of view of versatility and operability, 500 to 10,000 is preferred. Commercially available monools that are polymers include PML-S1004F (Asahi Glass Co., Ltd.). When using monools as polymers, from the viewpoint of the properties after curing, the amount of monool used is preferably 5% to 50% by mass, and more preferably 5% to 30% by mass, relative to the total amount of polyols.

[0109] Carbamate adhesives may also include adhesive-improving agents as needed. There are no particular limitations on the adhesive-improving agent, as long as it imparts or enhances the adhesiveness of the carbamate adhesive. Examples of adhesive-improving agents include, for instance, adhesive-improving resins that may be included in acrylic adhesives.

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

[0111] Carbamate adhesives may also contain reactive monofunctional compounds as needed. By including reactive monofunctional compounds, the cured adhesive exhibits superior adhesion (peel strength).

[0112] The reactive monofunctional compound is not particularly limited as long as it is a monofunctional compound that is reactive in the carbamate reaction and can improve the adhesive force (peel strength) of the cured adhesive. Specifically, examples include: monools used in the synthesis of terminal NCO prepolymers; monofunctional isocyanate compounds (reaction products of monools and diisocyanates, etc.); and other monofunctional components capable of undergoing carbamate reactions (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 even more preferred. Examples of reaction products of monools and diisocyanates include Bayer's trade name "Additive TI".

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

[0114] Carbamate adhesives may also contain additives as needed. Examples of additives include: urethane catalysts, plasticizers (acrylate plasticizers, phthalate esters, epoxidized hexahydrophthalate esters, alkyl dicarboxylic acid esters, alkylbenzenes, etc.), fillers (heavy calcium carbonate, fatty acid-treated calcium carbonate, fumigated silica, precipitated silica, carbon black, talc, titanium dioxide, balloons, granules, etc.), antioxidants (hindered phenols, etc.), flame retardants, thixotropic agents (colloidal silica, organobentonite, fatty acid amides, polyamide waxes, hydrogenated castor oil, etc.), ultraviolet absorbers (benzotriazoles, hindered amines, etc.), anti-aging agents (hindered phenols, thiols, thioethers, dithiocarboxylates, thioureas, thiophosphates, sulfur aldehydes, etc.), bonding agents (epoxides, silane coupling agents, etc.), and dehydrating agents.

[0115] Examples of carbamate catalysts include: DBU-based catalysts, amine-based catalysts, organocarboxylic acid metal salts, and imidazole-based catalysts. Examples of DBU-based catalysts include: DBU [1,8-diazabicyclo(5.4.0)undecene-7], DBU phenolate, DBU octanoate, 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.), alkanolamines (dimethylaminomethanol, etc.), and ether amines (bis(2-dimethylaminoethyl) ether, etc.). Examples of organocarboxylic acid metal salts include: Sn-based catalysts (dibutyltin dilaurate, tin octoate, etc.), Pb-based catalysts (lead octoate, etc.), and Zn-based catalysts (zinc octoate, etc.). Examples of imidazole-based catalysts include: 2-methylimidazole and 1,2-dimethylimidazole.

[0116] There are no particular limitations on the manufacturing method of carbamate adhesives. For example, a one-component carbamate adhesive can be prepared by mixing the polymer component contained in the carbamate adhesive with other components as needed. Carbamate adhesives can also be solvent-free adhesives that do not contain a solvent. If the carbamate adhesive does not contain a solvent, environmental pollution caused by the generation of odors, volatile organic compounds (VOCs), etc., can be suppressed when the adhesive is hardened by heat.

[0117] The adhesive layer may also 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) can be roughened, thereby improving the peelability of electronic components.

[0118] There are no particular restrictions on the material of the filler; it can be organic materials such as resin, inorganic materials such as metals and metal oxides, or a combination of organic and inorganic materials. Furthermore, the adhesive layer can contain only one type of filler or two or more types. There are no particular restrictions on the volume average particle size of the filler. For example, it can be selected from the range of 1 μm to 20 μm. In this disclosure, the volume average particle size of the filler is the particle size (D50) that accumulates from the smallest diameter side to 50% in the volumetric particle size distribution determined by laser diffraction.

[0119] From the viewpoint of affinity with the adhesive contained in the adhesive layer, the filler is preferably resin particles. Examples of resins constituting the resin particles include: acrylic resins, olefin resins, styrene resins, acrylonitrile resins, silicone resins, etc. From the viewpoint of suppressing residues on the surface of the formed semiconductor package, acrylic resin is preferred.

[0120] <Semiconductor Packaging Manufacturing Methods> The semiconductor package manufacturing method disclosed herein includes the following steps: sealing the periphery of the electronic component while the adhesive layer of the release film is in contact with at least a portion of the surface of the electronic component; and peeling the release film off the electronic component.

[0121] As described, the release film disclosed herein exhibits excellent peelability relative to the surface of electronic components (especially the surface with protrusions such as solder balls). Therefore, when the release film is peeled off, it is less likely to remain on the protruding parts, and the state of the protrusions on the surface of the electronic components can be well maintained.

[0122] There are no particular limitations on the types of electronic components used in the method. Examples include semiconductor elements, capacitors, and terminals. There are no particular limitations on the type of material (sealing material) used to seal around the electronic components in the method described. Examples include resin compositions containing epoxy resin, acrylic resin, etc. [Example]

[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 mixture of adhesive A (100 parts by mass), crosslinking agent A (17.4 parts by mass), filler (3 parts by mass), and a toluene:methyl ethyl ketone (34 parts by mass) in a mass ratio of 8:2 was prepared and stirred using a disperser to prepare the adhesive layer forming composition. This adhesive layer forming composition was applied to the entire surface of one side of a substrate (a 100 μm thick PBT film) to form an adhesive layer with a thickness of 20 μm. The film was then heated at 100°C for 1 minute to form the adhesive layer, thereby producing a release film.

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

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

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

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

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

[0130] Details of the materials used in the production of the release film are as follows. • Adhesive A: Acrylic adhesive, trade name "FS-1208", solids content 45% by weight, produced by Lion Specialty Chemicals Co., Ltd., containing a mixture of various monomers including methacrylates. • Adhesive B: Acrylic adhesive, trade name "S-43", solids content 24% by mass, from Zongyan Chemical Co., Ltd., containing a mixture of monomers including butyl acrylate (BA) and 4-hydroxybutyl acrylate (4HBA). • Crosslinking Agent A: Trade name "Duranate E405-80T", solid content 80% by mass, Asahi Kasei Chemicals Co., Ltd., polyisocyanate crosslinking agent (hexamethylene diisocyanate crosslinking agent (HMDI)), number of isocyanate groups per molecule: 2 • Crosslinking Agent B: Trade 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: Crosslinked acrylic acid dispersed particles, trade name "MX-500", volume average particle size 5 μm, Zongyan Chemical Co., Ltd.

[0131] <Evaluation Experiment> The peelability relative to the solder ball surface was evaluated using the prepared release film and the following tests. Specifically, with a release film attached to the surface of a semiconductor wafer having solder balls (maximum height from the wafer surface: 210 μm), the release film is peeled off after transfer molding using a sealing material. If the solder balls are exposed by more than 50 μm when the release film is peeled off, the evaluation is "acceptable"; if the solder balls are not exposed by more than 50 μm, the evaluation is "unacceptable". The results are shown in Table 1. The state of solder balls protruding more than 50 μm refers to the state where, after the release film is peeled off, the solder balls are less deformed, the adhesive layer is less residual, and the front end of the solder balls protrudes more than 50 μm from the surface of the formed sealing material.

[0132] [Table 1] project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Substrate layer Material PBT PBT PET PET PET PET thickness 100 μm 100 μm 75 μm 38 μm 38 μm 75 μm Adhesive layer Material acrylic acrylic acrylic acrylic acrylic acrylic thickness 20 μm 5 μm 25 μm 25 μm 3 μm 3 μm filler have have none none none none Adhesive layer thickness ratio 16.7% 4.8% 25.0% 39.7% 7.3% 3.8% Peelability Can Can Can No No No

[0133] As shown in Table 1, in the release sheets of the embodiments with an adhesive layer thickness ratio of 4% to 30% and a substrate layer thickness of 75 μm or more, the solder balls were well exposed. Compared with the examples, the solder balls were not sufficiently exposed in the release sheets of Comparative Examples 1 and 2, where the substrate layer thickness was less than 75 μm, and in the release sheet of Comparative Example 3, where the substrate layer thickness was 75 μm or more but the adhesive layer thickness ratio was outside the range of 4% to 30%.

[0134] The entire disclosure of Japanese Patent Application No. 2021-121945 is incorporated herein by reference. All documents, patent applications, and technical specifications described herein, and in particular, those documents, patent applications, and technical specifications which are incorporated herein by reference, are incorporated herein to the same extent.

[0135] 10: Adhesive layer 20: Substrate layer 30: Release film

Claims

1. A release film comprising a substrate layer and an adhesive layer, wherein the thickness of the adhesive layer is 4% to 30% of the combined thickness of the substrate layer and the adhesive layer, and the thickness of the substrate layer is 75 μm or more, the release film being used in a semiconductor packaging manufacturing method comprising the steps of: sealing the periphery of an electronic component while the adhesive layer is in contact with at least a portion of the surface of an electronic component having solder balls; and peeling the release film off the electronic component.

2. The release film as claimed in claim 1, used to expose at least a portion of the surface of an electronic component having solder balls.

3. The release film as claimed in claim 1 or claim 2, wherein the adhesive layer comprises an acrylic adhesive.

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

5. A method of manufacturing a semiconductor package as claimed in claim 4, wherein at least a portion of the surface of the electronic component in contact with the adhesive layer has solder balls.

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