Thermoplastic release film for semiconductor sealing process

Abstract

The present disclosure provides a thermoplastic release film for a semiconductor sealing process, which not only exhibits excellent releasability between a sealing resin and a mold and excellent mold followability, but also has sufficient heat resistance required for a semiconductor sealing process, such as resin molding, and further exhibits excellent handleability. This thermoplastic release film for a semiconductor sealing process contains a crystalline resin (A) having a melting point of 180ºC or higher and an acrylic copolymer (B). The crystalline resin (A) preferably includes at least one type selected from the group consisting of a crystalline fluororesin, a crystalline acyclic olefin resin and a crystalline polystyrene resin.

Description

Thermoplastic release film for semiconductor encapsulation process

[0001] The present invention relates to a thermoplastic release film for use in a semiconductor encapsulation process.

[0002] Conventionally, in a resin molding process for semiconductor elements on various package substrates such as multilayer printed wiring boards and flexible printed wiring boards, a release film has generally been used to ensure releasability between the encapsulating resin and a mold after the resin has hardened (see Patent Documents 1 and 2).

[0003] As this type of release film, fluororesin films such as ethylene-tetrafluoroethylene copolymer (ETFE) and polytetrafluoroethylene (PTFE), which have relatively excellent heat resistance, releasability, and mold conformability, are widely used. In addition, the use of non-fluororesin films such as polystyrene (PS) and polymethylpentene (PMP), or films containing syndiotactic polystyrene resins, is also being considered.

[0004] For example, Patent Document 3 discloses a mold release film for producing a semiconductor resin package, which includes at least one base layer C, a pair of outermost layers A sandwiching the base layer C and containing a 4-methyl-1-pentene polymer as a main component, and a pair of adhesive layers B bonding the base layer C and the outermost layer A together.

[0005] Furthermore, Patent Document 4 discloses a biaxially oriented film containing a syndiotactic polystyrene resin, characterized in that at least one side is a transfer surface, and the transfer surface is matte.

[0006] Furthermore, Patent Document 5 discloses a release film that is a biaxially oriented film formed from a composition containing a lubricant such as paraffin and hydrocarbon resin, fatty acid, fatty acid amide, fatty acid ester, fatty alcohol, partial ester of fatty acid and polyhydric alcohol, composite lubricant, and a syndiotactic polystyrene resin.

[0007] JP 2000-167841 A JP 2001-250838 A WO 2010 / 023907 JP 2013-216779 A Japanese Patent No. 5918604 A

[0008] However, although the laminated film using the 4-methyl-1-pentene polymer described in Patent Document 3 was expected to have improved heat resistance and mold releasability, in reality, the heat resistance is insufficient, and there are problems such as the transfer film itself fusing to a mold or a roll, and large thermal deformation causing adverse effects in the molding of a material to be molded, the lamination step of thin film layers, or the heat treatment step of the laminated thin film layers.

[0009] Furthermore, in practice, the syndiotactic polystyrene resin film described in Patent Document 4 sometimes fails to provide sufficient releasability between the film and the material to be molded, depending on the pressing conditions and the type and formulation of the resin.

[0010] Furthermore, in the release film described in Patent Document 5, although it was expected that the incorporation of a lubricant would improve mold tracking and releasability, in reality, this lubricant is likely to bleed out onto the surface of the release film, causing new problems in handling, such as poor appearance of the resin molded part and contamination of the mold.

[0011] The present invention has been made in view of the above-mentioned problems. That is, an object of the present invention is to provide a thermoplastic release film for a semiconductor encapsulation process, which not only has excellent releasability between the encapsulating resin and the mold and excellent mold followability, but also has the heat resistance required for a semiconductor encapsulation process such as resin molding, and further has excellent handleability (particularly due to the fact that the lubricant is less likely to bleed out onto the release film surface, also referred to as bleeding property).

[0012] As a result of extensive research into various release films in order to solve the above-mentioned problems, the inventors have newly developed a thermoplastic release film containing a crystalline resin (A) having a melting point of 180°C or higher and an acrylic copolymer (B), and have found that the above-mentioned problems can be solved by using this as a release film for semiconductor encapsulation processes, which has led to the completion of the present invention.

[0013] That is, the present invention provides various specific embodiments as shown below: (1) A thermoplastic release film for a semiconductor encapsulation process, comprising: a crystalline resin (A) having a melting point of 180°C or higher; and an acrylic copolymer (B).

[0014] (2) The thermoplastic release film for semiconductor encapsulation processes according to (1), wherein the crystalline resin (A) comprises at least one selected from the group consisting of a crystalline fluororesin, a crystalline acyclic olefin resin, and a crystalline polystyrene resin.

[0015] (3) The crystalline resin (A) comprises one or more selected from the group consisting of ethylene-tetrafluoroethylene copolymer (ETFE), 4-methyl-1-pentene (co)polymer (PMP), and syndiotactic polystyrene (S-PS). (1) or (2) The thermoplastic release film for semiconductor encapsulation process.

[0016] (4) The thermoplastic release film for semiconductor encapsulation process according to any one of (1) to (3), wherein the crystalline resin (A) contains syndiotactic polystyrene.

[0017] (5) The thermoplastic release film for semiconductor encapsulation process according to any one of (1) to (4), wherein the content of the crystalline resin (A) is 80 to 99 parts by mass, and the content of the acrylic copolymer (B) is 1 to 20 parts by mass, when the total amount of the crystalline resin (A) and the acrylic copolymer (B) is 100 parts by mass.

[0018] (6) The thermoplastic release film for a semiconductor encapsulation process according to any one of (1) to (5), wherein the crystalline resin (A) has a melt flow rate (MFR, in accordance with JIS K7210:1999, 300°C, 1.2 kg load) of 3 to 20 g / 10 min and a melting point of 200 to 275°C.

[0019] (7) The thermoplastic release film for semiconductor encapsulation process according to any one of (1) to (6), wherein the acrylic copolymer (B) is a copolymer of a first (meth)acrylic acid alkyl ester and a second (meth)acrylic acid alkyl ester having a structure different from that of the first (meth)acrylic acid alkyl ester.

[0020] (8) The thermoplastic release film for semiconductor encapsulation process according to any one of (1) to (7), wherein the acrylic copolymer (B) is a copolymer of a (meth)acrylic acid alkyl ester having 1 to 3 carbon atoms and a (meth)acrylic acid alkyl ester having 4 or more carbon atoms.

[0021] (9) The thermoplastic release film for semiconductor encapsulation process according to any one of (1) to (8), wherein the acrylic copolymer (B) is a copolymer having two or more types of units selected from the group consisting of methyl methacrylate units, n-butyl methacrylate units, n-butyl acrylate units, and isobutyl methacrylate units.

[0022] (10) The thermoplastic release film for a semiconductor encapsulation process according to any one of (1) to (9), wherein the acrylic copolymer (B) has a weight average molecular weight (Mw) of 100,000 or more and 6,000,000 or less.

[0023] (11) The thermoplastic release film for a semiconductor encapsulation process according to any one of (1) to (10), wherein the acrylic copolymer (B) has a weight average molecular weight (Mw) of 100,000 or more and 1,000,000 or less.

[0024] (12) The thermoplastic release film for semiconductor encapsulation process according to any one of (1) to (11), having a film thickness of 10 μm or more and 300 μm or less.

[0025] (13) The thermoplastic release film for semiconductor encapsulation process according to any one of (1) to (12), which is a uniaxially stretched film or a biaxially stretched film.

[0026] (14) The thermoplastic release film for a semiconductor encapsulation process according to any one of (1) to (13), which is a release film for molding.

[0027] According to one aspect of the present invention, it is possible to realize a thermoplastic release film for semiconductor encapsulation processes, which not only has excellent releasability between the encapsulating resin and the mold and excellent mold followability, but also has the heat resistance required in semiconductor encapsulation processes such as resin molding, and further has excellent handleability.

[0028] 1 is a schematic diagram illustrating an example of use of a thermoplastic release film 100 according to an embodiment.

[0029] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to those shown. However, the following embodiments are merely examples for explaining the present invention, and the present invention is not limited to these. In other words, the present invention can be implemented with any modifications within the scope of the gist of the present invention. In this specification, for example, a numerical range such as "1 to 100" includes both the lower limit "1" and the upper limit "100." The same applies to other numerical ranges.

[0030] (Thermoplastic release film) The thermoplastic release film of this embodiment is characterized by containing a crystalline resin (A) having a melting point of 180°C or higher and an acrylic copolymer (B). The thermoplastic release film of this embodiment can be suitably used, for example, as a release film for a semiconductor encapsulation process. The thermoplastic release film of this embodiment can be particularly suitably used as a release film for mold molding, which is interposed between a mold and a resin when resin molding a semiconductor element, to obtain good releasability between the mold and the resin after resin encapsulation.

[0031] [Crystalline Resin (A)] The crystalline resin (A) can be appropriately selected from known crystalline resins, and its type is not particularly limited, as long as it is a crystalline resin having a melting point of 180° C. or higher. By using a crystalline resin (A) having such a high melting point, the thermoplastic release film can be imparted with the heat resistance required in the semiconductor encapsulation process, and by using it in combination with the acrylic copolymer (B), a thermoplastic release film having an excellent balance of releasability, mold conformability, and handleability can be realized.

[0032] Examples of the crystalline resin (A) include, but are not limited to, crystalline fluororesins, crystalline acyclic olefin resins, and crystalline polystyrene resins. The crystalline resin (A) can be used alone or in any combination and ratio of two or more.

[0033] Specific examples of crystalline fluororesins include hexafluoropropylene-tetrafluoroethylene copolymer (FEP), perfluoro(alkyl vinyl ether)-tetrafluoroethylene copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-hexafluoropropylene-tetrafluoroethylene copolymer, vinyl fluoride polymer (PVF), vinylidene fluoride polymer (PVDF), vinylidene fluoride-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer, chlorotrifluoroethylene polymer (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), and the like, but are not particularly limited thereto. Among these, ethylene-tetrafluoroethylene copolymer (ETFE) is more preferred. The crystalline fluororesin can be used alone or in any combination and ratio of two or more types. The use of ethylene-tetrafluoroethylene copolymer (ETFE) as the crystalline fluororesin can impart high heat resistance and high mold releasability.

[0034] Specific examples of crystalline acyclic olefin resins include, but are not limited to, α-olefin (co)polymers. Among these, 4-methyl-1-pentene (co)polymers are more preferred. The term 4-methyl-1-pentene (co)polymer encompasses homopolymers of 4-methyl-1-pentene monomers, as well as copolymers containing 4-methyl-1-pentene monomer units and α-olefin monomer units other than 4-methyl-1-pentene. Here, the 4-methyl-1-pentene (co)polymer may further contain monomer units other than α-olefins. Examples of α-olefin monomers include, but are not limited to, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 3-methyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, 2-ethyl-1-hexene, and 2,2,4-trimethyl-1-pentene, each of which has 2 to 20 carbon atoms. The crystalline acyclic olefin resins may be used alone or in any combination and ratio of two or more. By using a 4-methyl-1-pentene (co)polymer as the crystalline acyclic olefin resin, high heat resistance and high mold releasability can be imparted.

[0035] Specific examples of crystalline polystyrene resins include syndiotactic polystyrene (S-PS), but are not particularly limited thereto. Among these, syndiotactic polystyrene (S-PS) is more preferred. The crystalline polystyrene resins can be used singly or in any combination and ratio of two or more. By using syndiotactic polystyrene (S-PS) as the crystalline polystyrene, high heat resistance and high mold releasability can be imparted. Here, syndiotactic polystyrene (S-PS) means polystyrene having a high degree of syndiotactic structure. In this specification, "syndiotactic" means that the proportion of phenyl rings in adjacent styrene units that are alternately arranged with respect to the plane formed by the main chain of the polymer block (hereinafter referred to as syndiotacticity) is high. Tacticity can be measured by nuclear magnetic resonance spectroscopy using carbon isotopes ( １３ Quantitative identification can be performed using 1C-NMR. １３ By C-NMR, the proportion of a plurality of consecutive structural units, for example, two consecutive monomer units as a diad, three consecutive monomer units as a triad, and five consecutive monomer units as a pentad, can be quantified.

[0036] The term "polystyrene having a highly syndiotactic structure" refers to polystyrene having a syndiotacticity of typically 75 mol % or more, preferably 85 mol % or more in racemic diad (r), or typically 30 mol % or more, preferably 50 mol % or more in racemic pentad (rrrr), poly(hydrocarbon-substituted styrene), poly(halogenated styrene), poly(halogenated alkylstyrene), poly(alkoxystyrene), poly(vinyl benzoate ester), hydrogenated polymers or mixtures thereof, or copolymers having these as the main component.

[0037] Examples of poly(hydrocarbon-substituted styrenes) include poly(methylstyrene), poly(ethylstyrene), poly(isopropylstyrene), poly(tert-butylstyrene), poly(phenyl)styrene, poly(vinylnaphthalene), and poly(vinylstyrene). Examples of poly(halogenated styrenes) include poly(chlorostyrene), poly(bromostyrene), and poly(fluorostyrene), and examples of poly(halogenated alkylstyrenes) include poly(chloromethylstyrene). Examples of poly(alkoxystyrenes) include poly(methoxystyrene) and poly(ethoxystyrene).

[0038] Particularly preferred examples of the styrene polymers include polystyrene, poly(p-methylstyrene), poly(m-methylstyrene), poly(p-tert-butylstyrene), poly(p-chlorostyrene), poly(m-chlorostyrene), and poly(p-fluorostyrene).Further examples include copolymers of styrene and p-methylstyrene, copolymers of styrene and p-tert-butylstyrene, and copolymers of styrene and divinylbenzene.

[0039] The weight average molecular weight (Mw) of the syndiotactic polystyrene (S-PS) can be appropriately set depending on the desired performance and is not particularly limited, but is preferably from 10,000 to 3,000,000, more preferably from 30,000 to 1,500,000, and even more preferably from 50,000 to 500,000.

[0040] Known commercially available syndiotactic polystyrene (S-PS) products include, for example, Xarec (registered trademark) 142ZE, 300ZC, 130ZC, 90ZC, S105, and S107 manufactured by Idemitsu Kosan Co., Ltd.

[0041] The melt flow rate (MFR) of the crystalline resin (A) can be appropriately set depending on the desired performance, and is not particularly limited. From the viewpoint of improving film transportability, releasability, and suppressing the occurrence of thickness unevenness and wrinkles, it is preferably 3 g / 10 min or more, more preferably 5 g / 10 min or more, even more preferably 7 g / 10 min or more, and preferably 20 g / 10 min or less, more preferably 19 g / 10 min or less, even more preferably 17 g / 10 min or less, and particularly preferably 16 g / 10 min or less. In this specification, the melt flow rate of the crystalline resin (A) means the value measured in accordance with JIS K7210:1999 "Test method for melt mass flow rate (MFR) and melt volume flow rate (MVR) of plastics - thermoplastic plastics" Method A, condition M (300 ° C, 1.2 kg load).

[0042] The melting point of the crystalline resin (A) is not particularly limited as long as it is 180°C or higher, but from the viewpoint of ensuring higher heat resistance and good compatibility or dispersibility with the acrylic copolymer (B), it is preferably 200 to 275°C, more preferably 220 to 275°C, and even more preferably 240 to 275°C. In this specification, the melting point refers to the melting peak temperature in differential scanning calorimetry (DSC) when heated at a heating rate of 20°C / min in a temperature range of 30 to 350°C using a DSC Vesta (manufactured by Rigaku Corporation).

[0043] The content of the crystalline resin (A) in the thermoplastic release film can be appropriately set depending on the required performance and is not particularly limited. From the viewpoints of heat resistance, releasability, mold followability, handleability, etc., when the total amount of the crystalline resin (A) and the acrylic copolymer (B) contained in the thermoplastic release film is taken as 100 parts by mass, the content of the crystalline resin (A) is preferably 80 to 99 parts by mass, more preferably 85 to 99 parts by mass, even more preferably 88 to 99 parts by mass, particularly preferably 90 to 99 parts by mass, and most preferably 92 to 98 parts by mass.

[0044] [Acrylic Copolymer (B)] The acrylic copolymer (B) can be appropriately selected from known copolymers and is not particularly limited in type. The acrylic copolymer (B) can be used alone or in any combination and ratio of two or more. By using the acrylic copolymer (B), it is possible to impart good mold conformability and releasability to the thermoplastic release film, and by using it in combination with a crystalline resin (A) having a melting point of 180°C or higher, it is possible to realize a thermoplastic release film that has an excellent balance of heat resistance and handleability required in the semiconductor encapsulation process.

[0045] Examples of the acrylic copolymer (B) include (meth)acrylic acid alkyl ester copolymers obtained by copolymerizing one or more (meth)acrylic acid alkyl esters, if necessary, together with other copolymerization components. Here, in this specification, "(meth)acrylic acid" and "(meth)acrylate" are generic terms for acrylic acid and methacrylic acid, and acrylate and methacrylate, respectively.

[0046] Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, propyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, stearyl (meth)acrylate, phenyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0047] The acrylic copolymer (B) is not particularly limited, but is preferably a copolymer of two or more of the above-mentioned (meth)acrylic acid alkyl esters, and more preferably an acrylic acid alkyl ester copolymer of a first (meth)acrylic acid alkyl ester and a second (meth)acrylic acid alkyl ester having a different structure. A preferred embodiment includes a copolymer of a (meth)acrylic acid alkyl ester having 1 to 3 carbon atoms and a (meth)acrylic acid alkyl ester having 4 or more carbon atoms. Examples of the (meth)acrylic acid alkyl ester having 1 to 3 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, and propyl (meth)acrylate, and examples of the (meth)acrylic acid alkyl ester having 4 or more carbon atoms include, but are not limited to, n-butyl (meth)acrylate and isobutyl (meth)acrylate, each of which has 4 carbon atoms. Another preferred embodiment is a copolymer of methyl (meth)acrylate, which is a (meth)acrylic acid alkyl ester having one carbon atom, and n-butyl (meth)acrylate or isobutyl (meth)acrylate, which is a (meth)acrylic acid alkyl ester having four carbon atoms.

[0048] Examples of other copolymerization components include other vinyl monomers copolymerizable with the (meth)acrylic acid alkyl ester. In this case, the acrylic copolymer (B) can be obtained, for example, by copolymerizing 50 to 100 parts by mass of the (meth)acrylic acid alkyl ester and, as necessary, 0 to 50 parts by mass of another vinyl monomer copolymerizable therewith, for a total of 100 parts by mass.

[0049] Examples of other vinyl monomers include, but are not limited to, styrene-based monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-densylstyrene, p-n-dodecylstyrene, p-phenylstyrene, and 3,4-dicyclostyrene; unsaturated dicarboxylic acid diesters (specifically, dimethyl maleate, Examples of suitable vinyl monomers include carboxylic acid-containing vinyl monomers such as diethyl maleate, dibutyl maleate, dimethyl fumarate, diethyl fumarate, dibutyl fumarate, etc., unsaturated monocarboxylic acids (specifically, (meth)acrylic acid, cinnamic acid, etc.), unsaturated dicarboxylic acids (specifically, maleic acid, fumaric acid, itaconic acid, etc.), and unsaturated dicarboxylic acid monoesters (specifically, monomethyl maleate, monoethyl maleate, monobutyl maleate, monomethyl fumarate, monoethyl fumarate, monobutyl fumarate, etc.); (meth)acrylonitrile; and (meth)acrylamide. These may be used alone or in combination of two or more. In this specification, "(meth)acrylonitrile" is a general term for acrylonitrile and methacrylonitrile, and "(meth)acrylamide" is a general term for acrylamide and methacrylamide.

[0050] Furthermore, as the other vinyl monomer, a polyfunctional vinyl monomer can also be used. Examples of polyfunctional vinyl monomers include divinylbenzene, divinylnaphthalene, allyl methacrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polybutylene glycol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate. These may be used alone or in combination of two or more.

[0051] The acrylic copolymer (B) is not particularly limited, but is preferably a copolymer B1 having two or more units selected from the group consisting of a methyl methacrylate unit, an n-butyl methacrylate unit, an n-butyl acrylate unit, and an isobutyl methacrylate unit, and more preferably a copolymer B2 having a methyl methacrylate unit, an n-butyl methacrylate unit, and an n-butyl acrylate unit.

[0052] In copolymers B1 and B2, the content of methyl methacrylate units is not particularly limited, but is preferably 30 to 85 mol %, more preferably 35 to 80 mol %, and even more preferably 40 to 80 mol %, when the total of all monomer units constituting the copolymer is 100 mol %. If the content of methyl methacrylate units in the copolymer is 30 mol % or more, storage stability is good, and if it is 85 mol % or less, both dispersibility and fixability can be achieved.

[0053] In copolymers B1 and B2, the content of n-butyl methacrylate units is not particularly limited, but is preferably 1 to 50 mol %, more preferably 5 to 45 mol %, and even more preferably 5 to 40 mol %, when the total of all monomer units constituting the copolymer is 100 mol %. If the content of n-butyl methacrylate units in the copolymer is 1 mol % or more, the material dispersibility will be better, and if it is 50 mol % or less, the storage stability will be good.

[0054] In copolymers B1 and B2, the content of n-butyl acrylate units is not particularly limited, but is preferably 1 to 50 mol %, more preferably 5 to 45 mol %, and even more preferably 5 to 40 mol %, when the total of all monomer units constituting the copolymer is 100 mol %. If the content of n-butyl acrylate units in the copolymer is 1 mol % or more, the material dispersibility will be better, and if it is 50 mol % or less, the storage stability will be good.

[0055] In copolymers B1 and B2, the content of isobutyl methacrylate units is not particularly limited, but is preferably 1 to 99 mol %, more preferably 10 to 99 mol %, and even more preferably 20 to 99 mol %, when the total of all monomer units constituting the copolymer is 100 mol %. If the content of isobutyl methacrylate units in the copolymer is within the above range, the material dispersibility will be better.

[0056] Copolymers B1 and B2 may be composed of only two or more of methyl methacrylate units, n-butyl methacrylate units, n-butyl acrylate units, and isobutyl methacrylate units, or may contain other monomer units.Examples of other monomers constituting the other monomer units include (meth)acrylates of linear alkyl alcohols such as methyl acrylate, ethyl (meth)acrylate, i-butyl acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, and lauryl (meth)acrylate; (meth)acrylates of cyclic alkyl alcohols such as cyclohexyl (meth)acrylate; methacrylic acid, acrylic acid, itaconic acid, and crotonic acid; Carboxy group-containing monomers such as maleic acid, fumaric acid, 2-succinoyloxyethyl-2-methacryloyloxyethyl methacrylate succinate, 2-maleinoyloxyethyl-2-methacryloyloxyethyl maleic methacrylate, 2-phthaloyloxyethyl-2-methacryloyloxyethyl phthalate, and 2-hexahydrophthaloyloxyethyl-2-methacryloyloxyethyl hexahydrophthalate; sulfonic acid group-containing monomers such as allyl sulfonic acid; acetoacetoxyethyl (meth)acrylate acrylate and other carbonyl group-containing (meth)acrylates; hydroxy group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate; amino group-containing (meth)acrylates such as N-dimethylaminoethyl (meth)acrylate and N-diethylaminoethyl (meth)acrylate; (poly)ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,6- Examples of suitable acrylates include, but are not limited to, polyfunctional (meth)acrylates such as hexanediol di(meth)acrylate and trimethylolpropane tri(meth)acrylate; acrylamide and its derivatives (for example, diacetone acrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, N-ethoxymethylacrylamide, N-butoxymethylacrylamide, etc.); styrene and its derivatives; vinyl acetate; urethane-modified acrylates; epoxy-modified acrylates; and silicone-modified acrylates. These may be used alone or in combination of two or more.Of these, the other monomers are preferably methyl acrylate, i-butyl acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate.

[0057] The content of the other monomer units is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less, based on 100% by mass of the total of all monomer units constituting copolymers B1 and B2. The lower limit of the content of the other monomer units is not particularly limited, and may be 20% by mass or more, 1% by mass or more, 3% by mass or more, or 5% by mass or more, based on 100% by mass of the total of all monomer units constituting copolymers B1 and B2.

[0058] It is preferable that the acrylic copolymer (B) has two or more concentrically arranged polymer layers with different compositions from the particle center to the surface layer. By using polymer components with different compositions to form a particle structure having two or more concentrically arranged polymer layers from the particle center to the surface layer, storage stability and heat moldability can be improved. Specific examples of such particle structures include a core-shell type consisting of two layers of a core polymer and a shell polymer, a multi-stage type consisting of a layer structure of three or more stages, and a gradient type in which each of these layers is very thin and has a nearly continuous composition change. Among these, a core-shell particle structure is preferred from the viewpoint of ease of preparation of polymer particles, but is not limited thereto.

[0059] Known commercially available products of the acrylic copolymer (B) include, for example, Metablen (registered trademark) L-1000, P-700, and P-710 manufactured by Mitsubishi Chemical Corporation.

[0060] The weight average molecular weight (Mw) of the acrylic copolymer (B) is not particularly limited, but from the viewpoint of mold conformability, mold releasability, handleability (bleeding), etc., it is preferably 100,000 to 6,000,000, more preferably 100,000 to 3,000,000, even more preferably 100,000 to 1,000,000, and particularly preferably 100,000 to 500,000. The weight average molecular weight (Mw) of the acrylic copolymer (B) can be measured using gel permeation chromatography (GPC). For example, it can be determined using tetrahydrofuran as an eluent and polystyrene as a standard substance.

[0061] The content of the acrylic copolymer (B) in the thermoplastic release film can be appropriately set depending on the required performance and is not particularly limited. From the viewpoints of heat resistance, releasability, mold followability, handleability, etc., when the total amount of the crystalline resin (A) and the acrylic copolymer (B) contained in the thermoplastic release film is taken as 100 parts by mass, the content of the acrylic copolymer (B) is preferably 1 to 20 parts by mass, more preferably 1 to 15 parts by mass, even more preferably 1 to 12 parts by mass, particularly preferably 1 to 10 parts by mass, and most preferably 2 to 8 parts by mass.

[0062] The thermoplastic release film of this embodiment may contain, in addition to the crystalline resin (A) having a melting point of 180 ° C. or higher and the acrylic copolymer (B) described above, other resin components such as thermosetting resins or thermoplastic resins, such as acetate polymers, polyethersulfone polymers, polysulfone polymers, polycarbonate polymers, polyamide polymers, polyimide polymers, polyolefin polymers, polyarylate polymers, and polyvinyl alcohol polymers, as long as the effects of the present invention are not excessively impaired. Furthermore, the thermoplastic release film of this embodiment may contain additives known in the art, such as release improvers such as higher fatty acids having 10 to 25 carbon atoms, higher fatty acid amides, higher fatty acid metal salts, polysiloxanes, and fluororesins; colorants such as dyes and pigments; organic fillers; inorganic fillers; antioxidants; heat stabilizers; light stabilizers; ultraviolet absorbers; flame retardants; antistatic agents; surfactants; rust inhibitors; antifoaming agents; and fluorescent agents, as long as the effects of the present invention are not excessively impaired. The other resin components and additives can be used alone or in combination of two or more. The other resin components and additives can be contained, for example, in the resin composition prepared during the production of the thermoplastic release film. The content of the other resin components and additives is not particularly limited, but from the viewpoints of moldability and thermal stability, it is preferably 0 to 10% by mass, more preferably 0 to 7% by mass, and even more preferably 0 to 5% by mass, of the total amount of the thermoplastic release film.

[0063] Here, the thermoplastic release film of this embodiment is preferably halogen-free or low in halogen content from the viewpoint of suppressing the occurrence of poor appearance of the resin molded part to a higher level and increasing versatility, and from the viewpoint of easy removal and disposal and reducing costs. From this viewpoint, the content of halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, iodine atoms) is preferably less than 3.0 mass%, more preferably less than 1.0 mass%, even more preferably less than 0.5 mass%, and particularly preferably less than 0.1 mass%, and the lower limit is not particularly limited, but is 0.0 mass% or 0.0 mass% or more. Therefore, from this viewpoint, the crystalline resin (A) is preferably a crystalline acyclic olefin resin or a crystalline polystyrene resin.

[0064] The method for producing the thermoplastic release film of this embodiment is not particularly limited, but a melt extrusion method is preferably used. One preferred embodiment involves extruding a resin composition containing the above-mentioned components into a film by a melt extrusion film-forming method, and then, if necessary, pressurizing and heating the melt-extruded film to obtain a melt-extruded film. In this case, the preparation of the resin composition may be carried out according to a conventional method and is not particularly limited. The above-mentioned components can be produced and processed by known methods such as kneading, melt kneading, granulation, extrusion molding, pressing, or injection molding. When melt kneading, commonly used kneading devices such as single-screw or twin-screw extruders and various kneaders can be used. When supplying the components to these melt kneading devices, the components may be dry-blended in advance using a mixing device such as a tumbler or Henschel mixer. The obtained melt-extruded film can be used as an unstretched release film for semiconductor encapsulation processes. However, from the viewpoints of improving film strength, improving heat resistance, adjusting film crystallinity, etc., uniaxial or biaxial heat stretching treatment may be performed in the in-plane direction of the film as necessary, and a post-heat treatment (annealing treatment) may also be performed after the stretching treatment. From the viewpoints of improving film transportability and releasability, suppressing the occurrence of thickness unevenness and wrinkles, etc., the thermoplastic release film of this embodiment is preferably a uniaxially stretched film or a biaxially stretched film, and more preferably a biaxially stretched film. Furthermore, from the viewpoints of cost reduction, reuse or recycling, etc., the thermoplastic release film of this embodiment is preferably a single-layer film (non-laminated film). The thickness of the unstretched melt-extruded film can be appropriately set depending on the required performance and is not particularly limited, but may be, for example, 5 μm to 1500 μm. The thickness is preferably 10 μm or more and 1000 μm or less, more preferably 20 μm or more and 800 μm or less, and even more preferably 30 μm or more and 600 μm or less. In this specification, the thickness of the unstretched melt-extruded film means the average value of nine randomly selected points.

[0065] The conditions set during melt extrusion are not particularly limited and may be appropriately set depending on the type and composition of the resin composition used, the desired performance of the target thermoplastic release film, etc. For example, the set temperature of the cylinder of the extruder is preferably 250 to 320°C, more preferably 260 to 310°C.

[0066] The conditions for the heat stretching treatment are not particularly limited and may be appropriately set depending on the type and composition of the resin composition used, the desired performance of the target thermoplastic release film, etc. For example, the melt-extruded film is preferably stretched in the MD (machine direction; longitudinal direction) at 70 to 180°C by 1.1 to 6.0 times to form a uniaxially stretched film, and then further stretched in the TD (transverse direction; horizontal direction) at 90 to 180°C by 1.1 to 6.0 times, and then preferably heat-treated (heat-set) at 100 to 240°C for 1 to 600 seconds, for example. At this time, simultaneous biaxial stretching can also be performed instead of sequential stretching. The stretching ratio is not particularly limited, but from the viewpoints of improving film transportability and releasability, and suppressing the occurrence of thickness unevenness and wrinkles, the total stretching ratio in the MD direction*the TD direction (stretching ratio expressed as m×n, where m is the stretching ratio in the MD direction and n is the stretching ratio in the TD direction) is preferably 2.00 or more, more preferably 4.00 or more, and even more preferably 6.25 or more. The upper limit is not particularly limited, but 25 is used as a guide, preferably 20. Furthermore, during heat setting, methods known in the art, such as contact heat treatment and non-contact heat treatment, can be used, and the type of method is not particularly limited. For example, heat setting can be performed using known equipment such as a non-contact heater, oven, blower, heat roll, cooling roll, heat press, or double-belt heat press. At this time, if necessary, a release film or porous film known in the art can be placed on the surface of the stretched melt-extruded film, and heat and pressure treatment can be performed.

[0067] The conditions for the post-heat treatment (annealing treatment) are not particularly limited and may be set appropriately depending on the type and composition of the resin composition used, the desired performance of the target thermoplastic release film, etc. For example, it is preferable to heat-treat the melt-extruded film or stretched melt-extruded film at 100 to 240°C for 1 to 600 seconds. This post-heat treatment can be carried out using a method known in the art, such as contact heat treatment or non-contact heat treatment, and the type is not particularly limited. For example, the post-heat treatment can be carried out using known equipment such as a non-contact heater, oven, blower, heat roll, cooling roll, heat press, or double-belt heat press. At this time, if necessary, a release film or porous film known in the art can be placed on the surface of the melt-extruded film or stretched melt-extruded film, and the heat and pressure treatment can be carried out.

[0068] The thickness of the thermoplastic release film of this embodiment can be set appropriately according to requirements and is not particularly limited. Considering handleability and productivity, the thickness of the thermoplastic release film of this embodiment is preferably 10 μm or more and 300 μm or less, more preferably 10 μm or more and 200 μm or less. From the viewpoint of improving mold followability, it is even more preferably 20 μm or more and 150 μm or less, particularly preferably 30 μm or more and 100 μm or less. In this specification, the thickness of the thermoplastic release film means the average value of nine randomly selected points. The surface shape of the thermoplastic release film of this embodiment can be adjusted appropriately according to requirements, and may be an uneven shape on one or both sides. The method for imparting an uneven surface shape to the thermoplastic release film of this embodiment is not particularly limited, but common methods such as sandblasting and embossing can be used.

[0069] By adopting the above-described configuration, the thermoplastic release film of this embodiment not only exhibits excellent releasability and mold conformity between the encapsulating resin and the mold, but also has the heat resistance required for semiconductor encapsulation processes such as resin molding, and is easy to handle. Therefore, the thermoplastic release film of this embodiment can be suitably used as a release film for semiconductor encapsulation processes to ensure releasability between the encapsulating resin and the mold after the resin has hardened during the resin molding process of semiconductor elements using an encapsulating resin such as an epoxy resin. Furthermore, the thermoplastic release film of this embodiment can also suppress the occurrence of wrinkles, poor appearance of the resin molded part, and mold contamination. Therefore, the thermoplastic release film of this embodiment fully meets the required performance requirements as a thermoplastic release film for semiconductor encapsulation processes using a compression molding method (compression molding method), which requires more precise molding conditions than the conventionally commonly used transfer molding method.

[0070] The thermoplastic release film of this embodiment is preferably used as a release film in the resin encapsulation step of semiconductor elements in the manufacture of semiconductor devices. The method for encapsulating semiconductor elements using the thermoplastic release film of this embodiment is not particularly limited. When encapsulating semiconductor elements inside a molding die, the thermoplastic release film of this embodiment may simply be placed on the inner surface of the molding die. For example, the thermoplastic release film of this embodiment can be preferably used in known resin molding processes such as transfer molding and compression molding. In particular, compression-type resin encapsulation involves pouring resin into the cavity of a mold, melting the resin, and then clamping the mold to tightly seal the semiconductor element and the molten resin. This method minimizes resin flow and minimizes the impact on the chip and wire, allowing for thinner wires. This method is widely adopted as it meets the recent process needs for minimizing packaging, thinning, high integration, high productivity, and cost reduction. The compression method eliminates the need for gates and runners, as required by the transfer method, and achieves nearly 100% resin utilization efficiency, thereby leading to cost savings and reduced waste.

[0071] Therefore, the thermoplastic release film of this embodiment is particularly useful in compression-type resin molding. As an example of its use, as shown in FIG. 1 , a mold D is used that includes an upper mold D1 and a lower mold D2. A thermoplastic release film 100 is interposed on the inner surface of the lower mold D2. Vacuuming is performed as necessary to adhere the thermoplastic release film 100 to the inner surface or parting surface of the lower mold D2. A molding resin M is poured into the cavity C of the lower mold D2. The molding resin M is melted or liquefied by heating as necessary. The upper mold D1 and the lower mold D2 are then clamped together to adhere (or press-bond or compress) the substrate 11 carrying a semiconductor element to the molding resin M. Heating and pressure are applied as necessary to resin-encapsulate the semiconductor element. The thermoplastic release film 100 may be interposed on at least one side of the inner surface of the upper mold D1 or the inner surface of the lower mold D2. The molding conditions at this time are not particularly limited and may be carried out according to conventional methods, but the mold temperature (molding temperature) is, for example, 160 to 190°C, the molding pressure is, for example, 5 to 12 MPa, and the molding time is, for example, about 1 to 600 seconds. By interposing the thermoplastic release film 100 during resin molding in this way, contact between the molding resin M and the inner surface of the mold D can be avoided, making it easier to release the substrate 11 from the mold D after resin sealing. Note that examples of the substrate 11 to be resin-sealed here include multilayer printed wiring boards and flexible printed wiring boards, but the type is not particularly limited.

[0072] The features of the present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto. That is, the materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the spirit of the present invention. Furthermore, the values ​​of various production conditions and evaluation results in the following examples represent preferred upper or lower limits in the embodiments of the present invention, and preferred numerical ranges may be defined by combining the above-mentioned upper or lower limits with the values ​​of the following examples or values ​​between the examples.

[0073] The materials used in the examples and comparative examples are as follows. (Resin A) (A-1) Syndiotactic polystyrene (Idemitsu Kosan Co., Ltd., Xarek (registered trademark), 142ZE, melting temperature: 247°C, melt flow rate: 14 g / 10 min (JIS K7210:1999 compliant, 300°C, 1.2 kg load)) (A-2) Polystyrene (Toyo Styrene Co., Ltd., Toyo Styrol (registered trademark), HRM61) (A-3) Polypropylene (Sunallomer Co., Ltd., Sunallomer (registered trademark), VS200A) (Resin B) (B-1) Alkyl methacrylate / alkyl acrylate copolymer, Mitsubishi Chemical Corporation, trade name "Metablen L-1000"), melt flow rate: 2.4 g / 10 min (JIS K7210:1999 compliant, 230°C, 2.16 kg load) (B-2) Liquid paraffin (MORESCO Corporation, Selenium White 350)

[0074] Example 1 Resin A, which had been dried at 80°C for 8 hours or more, and resin B were dry-blended in the composition and compounding ratios shown in Table 1. The resulting blend was melt-kneaded in a co-rotating, vented twin-screw kneading extruder heated to 280°C, and the resulting strands were cut with a pelletizer to prepare a resin composition (blend chips). The resulting resin composition was dried at 80°C for 8 hours or more using a hopper dryer or the like, and then placed in a hopper equipped in an extruder heated to 280°C, melt-kneaded, extruded into a film form from a T-die at the tip of the extruder, and cooled to obtain an unstretched melt-extruded film having a thickness of 450 μm. The obtained unstretched melt-extruded film was biaxially stretched at 120°C in a sequential biaxial stretching machine to 3.0 times in the MD direction and 3.0 times in the TD direction (total stretching ratio: 9.0 times), and heat-set at 140°C for 2 minutes to obtain the thermoplastic release film of Example 1 having an average thickness of 50 μm.

[0075] Examples 2 to 5 The thermoplastic release films of Examples 2 to 5 were obtained in the same manner as in Example 1, except that the compositions, blending ratios, and average thicknesses of the thermoplastic release films were changed to those shown in Table 1.

[0076] Comparative Examples 1 to 4 The same procedure as in Example 1 was carried out except that the compositions and blending ratios were changed to those shown in Table 1, and thermoplastic release films of Comparative Examples 1 to 4 having an average thickness of 50 μm were obtained.

[0077] The conditions for measuring the physical properties of each of the obtained thermoplastic release films are as follows.

[0078] [Film Thickness] The thickness of each thermoplastic release film was measured at nine random points, and the average value was expressed.

[0079] The performance of each thermoplastic release film obtained was evaluated as follows. (Molding test) As shown in Figure 1, a thermoplastic release film 100 was drawn out from a roll and placed between an upper mold D1 and a lower mold D2 of a semiconductor encapsulation compression molding device (PMC1040, manufactured by TOWA Corporation) with a tension of 1 MPa applied between them, and then the thermoplastic release film 100 was vacuum-adsorbed onto the parting surface of the lower mold D2 and cut to a certain length. A substrate 11 with a semiconductor element mounted thereon was placed on the parting surface of the upper mold D1. Next, molding resin M is poured into cavity C of lower mold D2, whose parting surface is protected by thermoplastic release film 100, and the mold temperature is heated to 180°C to melt or liquefy molding resin M. Then, upper mold D1 and lower mold D2 are clamped together, air is removed from the vacuum suction holes on the periphery of the cavity with a vacuum pump, and the semiconductor elements fixed to the substrate are tightly sealed to a predetermined final depth and with a predetermined clamping force for a predetermined time to perform compression resin sealing (compression molding), and the resin-sealed substrate (semiconductor package) is released and removed from mold D and thermoplastic release film 100. The performance of each thermoplastic release film 100 at this time was evaluated according to the following criteria.

[0080] <Sealing conditions> Mold temperature: 175°C Cavity size: 220 mm x 55 mm Final cavity depth: 0.5 mm Curable resin: Sumikon EME G770H type F Ver. GR (manufactured by Sumitomo Bakelite Co., Ltd.) Degree of vacuum when conforming to cavity surface: -85 kPa Degree of vacuum when removing bubbles from curable resin: -80 kPa Debubbling time for curable resin: 10 seconds Clamping time: 120 seconds Molding pressure: 8.0 MPa

[0081] (Releasability) Very Good (A): The thermoplastic release film peeled off easily from the semiconductor package. Good (B): The thermoplastic release film peeled off from the semiconductor package with resistance. Bad (C): The thermoplastic release film did not peel off from the semiconductor package but remained attached.

[0082] (Heat resistance) Very Good (A): When the thermoplastic release film was adsorbed onto the mold, it was adsorbed evenly and no wrinkles were generated. Good (B): When the thermoplastic release film was adsorbed onto the mold, slight wrinkles were generated. Bad (C): The thermoplastic release film had many wrinkles or was torn.

[0083] (Mold followability) Very Good (A): No resin chipping on the semiconductor package Good (B): There was some resin chipping on the edge of the semiconductor package Bad (C): The thermoplastic release film did not follow the mold and could not be vacuum-adsorbed

[0084] (Bleeding) Each test film was left in an oven at 70°C for 72 hours, and the components that bled onto the surface of the film were visually observed, and the appearance was evaluated according to the following criteria: Very Good (A): No bleeding at all Good (B): Slight bleeding Bad (C): Bleeding

[0085]

[0086] The thermoplastic release film of the present invention not only has excellent releasability between the encapsulating resin and the mold and excellent mold followability, but also has the heat resistance required during semiconductor encapsulation processes such as resin molding, and is easy to handle. Therefore, it can be widely and effectively used as a release film for the semiconductor encapsulation process used during the resin molding step of semiconductor elements, and can be particularly effectively used as a release film for the semiconductor encapsulation process during compression molding.

[0087] REFERENCE SIGNS LIST 100: Thermoplastic release film 11: Substrate on which semiconductor element is mounted C: Cavity D: Mold D1: Upper mold D2: Lower mold M: Mold resin

Claims

1. A thermoplastic release film for semiconductor encapsulation process, comprising: a crystalline resin (A) having a melting point of 180°C or higher; and an acrylic copolymer (B).

2. The thermoplastic release film for semiconductor encapsulation process according to claim 1, wherein the crystalline resin (A) comprises at least one selected from the group consisting of crystalline fluororesin, crystalline acyclic olefin resin, and crystalline polystyrene resin.

3. The thermoplastic release film for semiconductor encapsulation process according to claim 1, wherein the crystalline resin (A) comprises at least one selected from the group consisting of ethylene-tetrafluoroethylene copolymer (ETFE), 4-methyl-1-pentene (co)polymer (PMP), and syndiotactic polystyrene (S-PS).

4. The thermoplastic release film for semiconductor encapsulation process according to claim 1, wherein the crystalline resin (A) contains syndiotactic polystyrene.

5. The thermoplastic release film for semiconductor encapsulation process according to claim 1, wherein the content of said crystalline resin (A) is 80 to 99 parts by mass, and the content of said acrylic copolymer (B) is 1 to 20 parts by mass, when the total amount of said crystalline resin (A) and said acrylic copolymer (B) is 100 parts by mass.

6. The thermoplastic release film for semiconductor encapsulation process according to claim 1, wherein the crystalline resin (A) has a melt flow rate (MFR, JIS K7210:1999 compliant, 300°C, 1.2 kg load) of 3 to 20 g / 10 min and a melting point of 200 to 275°C.

7. The thermoplastic release film for semiconductor encapsulation process according to claim 1, wherein the acrylic copolymer (B) is a copolymer of a first (meth)acrylic acid alkyl ester and a second (meth)acrylic acid alkyl ester having a structure different from that of the first (meth)acrylic acid alkyl ester.

8. The thermoplastic release film for semiconductor encapsulation process according to claim 1, wherein the acrylic copolymer (B) is a copolymer of a (meth)acrylic acid alkyl ester having 1 to 3 carbon atoms and a (meth)acrylic acid alkyl ester having 4 or more carbon atoms.

9. The thermoplastic release film for semiconductor encapsulation process according to claim 1, wherein the acrylic copolymer (B) is a copolymer having two or more types of units selected from the group consisting of methyl methacrylate units, n-butyl methacrylate units, n-butyl acrylate units and isobutyl methacrylate units.

10. The thermoplastic release film for semiconductor encapsulation process according to claim 1, wherein the acrylic copolymer (B) has a weight average molecular weight (Mw) of 100,000 or more and 6,000,000 or less.

11. The thermoplastic release film for semiconductor encapsulation process according to claim 1, wherein the acrylic copolymer (B) has a weight average molecular weight (Mw) of 100,000 or more and 1,000,000 or less.

12. The thermoplastic release film for semiconductor encapsulation process according to claim 1, having a film thickness of 10 μm or more and 300 μm or less.

13. The thermoplastic release film for semiconductor encapsulation process according to claim 1, which is a uniaxially oriented film or a biaxially oriented film.

14. The thermoplastic release film for semiconductor encapsulation process according to claim 1, which is a release film for molding.

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