Thermoplastic release film for semiconductor sealing process

Abstract

To provide a thermoplastic release film for a semiconductor sealing process which has heat resistance required in a semiconductor sealing process such as resin molding in addition to excellent releasability between a sealing resin and a mold and mold followability, and is also excellent in handleability.SOLUTION: A thermoplastic release film for a semiconductor sealing process contains a crystalline resin (A) having a melting point of 180°C or higher, and an acrylic copolymer (B), wherein a lowest value of a storage elastic modulus E' at 100°C to 160°C is 10 MPa or more, in both of one direction in a film plane and the other direction in the film plane perpendicular to the one direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, during the resin molding process of 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 sealing resin and the 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 has 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 characterized by being 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 syndiotactic polystyrene resin. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-167841 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-250838 [Patent Document 3] International Publication No. 2010 / 023907 [Patent Document 4] Japanese Patent Application Laid-Open No. 2013-216779 [Patent Document 5] Patent No. 5918604 Summary of the Invention [Problem to be solved by the invention]

[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 releasability, in reality, it did not have sufficient heat resistance, and had problems such as the transfer film itself fusing to a mold or roll, and large thermal deformation, which adversely affected the molding of the material to be molded, the lamination process of the thin film layer, or the heat treatment process of the laminated thin film layer.

[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 addition of a lubricant would improve mold tracking and releasability, in reality, this lubricant tends to bleed out onto the surface of the release film, causing new problems in handling, such as 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 use in 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 in a semiconductor encapsulation process such as resin molding, and is excellent in handleability (particularly due to the fact that the lubricant is less likely to bleed out onto the release film surface, also known as bleeding property). [Means for solving the problem]

[0012] As a result of extensive research into various release films 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). They have found that the above-mentioned problems can be solved by using this as a release film for semiconductor encapsulation processes, and have thus completed the present invention.

[0013] That is, the present invention provides various specific embodiments as shown below. (1) a crystalline resin (A) having a melting point of 180°C or higher; An acrylic copolymer (B), The minimum value of the storage modulus E' at 100°C to 160°C is 10 MPa or more in both one direction in the film plane and the other direction in the film plane perpendicular to the one direction in the film plane. Thermoplastic release film for semiconductor encapsulation processes.

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

[0015] (3) The crystalline resin (A) contains 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). The thermoplastic release film for semiconductor encapsulation process according to (1) or (2).

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

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

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

[0019] (7) 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 different structure. The thermoplastic release film for semiconductor encapsulation process according to any one of (1) to (6).

[0020] (8) 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. The thermoplastic release film for semiconductor encapsulation process according to any one of (1) to (7).

[0021] (9) 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. The thermoplastic release film for semiconductor encapsulation process according to any one of (1) to (8).

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

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

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

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

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

[0027] (15) In the manufacture of a semiconductor package in which a semiconductor element is placed in a mold and sealed with a hardening resin to form a resin sealing portion, The thermoplastic release film for semiconductor encapsulation process according to any one of (1) to (14). [Effects of the Invention]

[0028] 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. [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic diagram showing an example of use of a thermoplastic release film 100 according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0030] 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 of 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 thereto. 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.

[0031] (thermoplastic release film) The thermoplastic release film of this embodiment contains a crystalline resin (A) having a melting point of 180°C or higher and an acrylic copolymer (B), and is characterized in that the minimum value of the storage modulus E' at 100°C to 160°C is 10 MPa or higher in both one direction in the film plane and the other direction in the film plane perpendicular to the one direction. The one direction in the film plane can be, for example, the MD direction of the thermoplastic release film, and the other direction in the film plane perpendicular to the one direction can be, for example, the TD direction of the thermoplastic release film. Furthermore, in this specification, the term "orthogonal" encompasses orthogonal and approximately orthogonal, and is a concept that includes errors and variations to the extent that identity is not lost. That is, one direction and the other direction perpendicular to the one direction may intersect at an angle of exactly 90°, or may intersect at an angle of 90°±8° (82° to 98°), for example. The thermoplastic release film of this embodiment can be suitably used, for example, as a release film for semiconductor encapsulation processes. The thermoplastic release film of the present embodiment is particularly suitable for use as a release film for mold molding, which is placed between a mold and a resin when resin molding a semiconductor element, in order to obtain good releasability between the mold and the resin after resin sealing.

[0032] [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 given 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.

[0033] 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.

[0034] Specific examples of crystalline fluororesins include, but are not limited to, 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), and ethylene-chlorotrifluoroethylene copolymer (ECTFE). Among these, ethylene-tetrafluoroethylene copolymer (ETFE) is more preferred. Crystalline fluororesins can be used alone or in any combination and ratio of two or more. Using ethylene-tetrafluoroethylene copolymer (ETFE) as the crystalline fluororesin can impart high heat resistance and high mold releasability.

[0035] 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. 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 4-methyl-1-pentene (co)polymer as the crystalline acyclic olefin resin, high heat resistance and high mold releasability can be imparted.

[0036] Specific examples of crystalline polystyrene resins include, but are not limited to, syndiotactic polystyrene (S-PS). 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 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 the C-NMR method. 13 By C-NMR, the proportion of consecutive structural units, for example, two consecutive monomer units as a dyad, three consecutive monomer units as a triad, and five consecutive monomer units as a pentad, can be quantified.

[0037] 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 diads (r), or typically 30 mol % or more, preferably 50 mol % or more in racemic pentads (rrrr), poly(hydrocarbon-substituted styrenes), poly(halogenated styrenes), poly(halogenated alkylstyrenes), poly(alkoxystyrenes), poly(vinyl benzoates), hydrogenated polymers or mixtures thereof, or copolymers having these as the main components.

[0038] 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). Examples of poly(halogenated alkylstyrenes) include poly(chloromethylstyrene). Examples of poly(alkoxystyrenes) include poly(methoxystyrene) and poly(ethoxystyrene).

[0039] 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.

[0040] The weight average molecular weight (Mw) of 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. In this specification, the weight average molecular weight (Mw) is determined by GPC measurement in accordance with JIS K 7252-1:2016 under the following conditions. Apparatus: Tosoh Corporation GPC "HLC-8320GPC" Column: Shodex KF404 x 3 Temperature: 40℃ Solvent: tetrahydrofuran Flow rate: 0.2ml / min Pressure: 10 MPa Detection: RI Sample preparation method: 120 mg of a sample was dissolved in 15 mL of tetrahydrofuran, and then filtered through a syringe filter (Millex (registered trademark) 0.45 um, manufactured by Merck Millipore Co., Ltd.). Injection volume: 10μl Calibration curve: Using standard polystyrene (manufactured by Polymer Laboratories), the relationship between elution time and elution amount is converted into molecular weight to determine various average molecular weights.

[0041] Known commercially available syndiotactic polystyrene (S-PS) products include, for example, Xarek (registered trademark) 142ZE, 300ZC, 130ZC, 90ZC, S105, and S107 manufactured by Idemitsu Kosan Co., Ltd.

[0042] The melt flow rate (MFR) of the crystalline resin (A) can be appropriately set according to the desired performance and is not particularly limited, but from the viewpoint of improving film conveyance, releasability, suppressing thickness unevenness and wrinkles, etc., 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, 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 - thermoplastics" Method A, condition M (300 ° C, 1.2 kg load).

[0043] 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 measured by differential scanning calorimetry (DSC) using a DSC Vesta (manufactured by Rigaku Corporation) in the temperature range of 30 to 350°C, at a heating rate of 20°C / min.

[0044] 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.

[0045] [Acrylic copolymer (B)] The acrylic copolymer (B) can be appropriately selected from known copolymers and is not particularly limited. The acrylic copolymer (B) can be used alone or in any combination and ratio of two or more. The use of the acrylic copolymer (B) can 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, which are required in the semiconductor encapsulation process.

[0046] 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.

[0047] 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.

[0048] 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 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. 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.

[0049] 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 by copolymerizing, for example, 50 to 100 parts by mass of the (meth)acrylic acid alkyl ester and, if necessary, 0 to 50 parts by mass of another vinyl monomer copolymerizable therewith, for a total of 100 parts by mass.

[0050] 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, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn-octylstyrene, pn-nonylstyrene, pn-densylstyrene, pn-dodecylstyrene, p-phenylstyrene, and 3,4-dicyclostyrene; unsaturated dicarboxylic acid diesters (specifically, dimethyl maleate, dimethyl methacrylate ... Examples of suitable vinyl monomers include carboxylic acid-containing vinyl monomers such as diethyl phosphate, 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.

[0051] 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.

[0052] 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 methyl methacrylate units, n-butyl methacrylate units, n-butyl acrylate units, and isobutyl methacrylate units, and more preferably a copolymer B2 having methyl methacrylate units, n-butyl methacrylate units, and n-butyl acrylate units.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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, 2-maleinoyloxyethyl-2-methacryloyloxyethyl maleic acid, 2-phthaloyloxyethyl-2-methacryloyloxyethyl phthalic acid, and 2-hexahydrophthaloyloxyethyl-2-methacryloyloxyethyl hexahydrophthalic acid; sulfonic acid group-containing monomers such as allyl sulfonic acid; acetoacetoxyethyl (meth)acrylate Carbonyl group-containing (meth)acrylates such as acrylate; 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 the polyfunctional (meth)acrylates include hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and the like; acrylamide and its derivatives (e.g., diacetone acrylamide, N-methylolacrylamide, N-methoxymethylacrylamide, N-ethoxymethylacrylamide, N-butoxymethylacrylamide, and the like); styrene and its derivatives; vinyl acetate; urethane-modified acrylates; epoxy-modified acrylates; and silicone-modified acrylates, but are not limited thereto. 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.

[0058] The content of 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 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.

[0059] The acrylic copolymer (B) preferably has two or more concentrically arranged polymer layers with different compositions from the particle center to the surface. By using polymer components with different compositions to form a particle structure with two or more concentrically arranged polymer layers from the particle center to the surface, 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 with 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.

[0060] 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.

[0061] The weight average molecular weight (Mw) of the acrylic copolymer (B) is not particularly limited, but from the viewpoints of mold conformability, mold releasability, handleability (bleedability), etc., it is preferably from 100,000 to 6,000,000, more preferably from 100,000 to 3,000,000, even more preferably from 100,000 to 1,000,000, and particularly preferably from 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.

[0062] 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.

[0063] In addition to the crystalline resin (A) having a melting point of 180 ° C. or higher and the acrylic copolymer (B), the thermoplastic release film of this embodiment may contain 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 singly or in combination of two or more. The other resin components and additives can be contained in, for example, a 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, the content of each of the other resin components and additives is preferably 0 to 10% by mass, more preferably 0 to 7% by mass, and even more preferably 0 to 5% by mass, relative to the total amount of the thermoplastic release film.

[0064] 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%. 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.

[0065] The thermoplastic release film of this embodiment is characterized in that the minimum value of the storage modulus E' at 100°C to 160°C is 10 MPa or more in both one direction in the film plane (MD direction of the thermoplastic release film) and the other direction in the film plane perpendicular to this (TD direction of the thermoplastic release film). If the storage modulus E' of the thermoplastic release film does not satisfy the above condition, the heat resistance tends to be insufficient, and adverse effects such as the occurrence of wrinkles and tears in the thermoplastic release film during semiconductor encapsulation processes such as resin molding tend to occur. Note that, in this specification, the storage modulus E' in dynamic viscoelasticity measurement means the value (MPa) measured when the temperature is increased from room temperature to 200°C at a heating rate of 5°C / min according to JIS K 7244-4:1999. The storage modulus E' of the thermoplastic release film is preferably 13 MPa or more in both the MD direction and the TD direction, more preferably 15 MPa or more, and even more preferably 20 MPa or more. The upper limit is not particularly limited, but may be preferably 100 MPa or less, more preferably 90 MPa or less, and even more preferably 75 MPa or less. The storage modulus E' can be controlled, for example, by the type and blending ratio of the crystalline resin (A) and acrylic copolymer (B) used. The storage modulus E' can also be controlled by the average thickness and stretching ratio of the thermoplastic release film. Increasing the stretching ratio of the thermoplastic release film tends to increase the storage modulus E' in that direction. The measurement conditions for dynamic viscoelasticity measurement are the same as those described in the examples below.

[0066] 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 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.

[0067] The conditions for 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.

[0068] 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, a melt-extruded film is preferably stretched 1.1 to 6.0 times in the MD direction (machine direction; longitudinal direction) at 70 to 180°C to form a uniaxially stretched film, and then further stretched 1.1 to 6.0 times in the TD direction (transverse direction; horizontal direction) at 90 to 180°C, and then preferably heat-treated (heat-set) for 1 to 600 seconds at 100 to 240°C, for example. At this time, simultaneous biaxial stretching can be performed instead of sequential stretching. The stretching ratio is not particularly limited. From the viewpoints of improving film transportability and releasability, and suppressing thickness unevenness and wrinkles, the total stretching ratio in the MD direction*TD direction (where m is the stretching ratio in the MD direction and n is the stretching ratio in the TD direction, and the result is m×n) is preferably 4.00 or more, more preferably 5.00 or more, even more preferably 6.25 or more, and particularly preferably 6.50 or more. The upper limit is not particularly limited, but a guideline is 25 or less, preferably 20 or less. Furthermore, heat setting can be performed using methods known in the art, such as contact heat treatment and non-contact heat treatment, 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. If necessary, a release film or porous film known in the art can be placed on the surface of the stretched melt-extruded film, followed by heat and pressure treatment.

[0069] The thermoplastic release film of this embodiment is preferably a uniaxially stretched film or a biaxially stretched film. Here, when the thermoplastic release film of this embodiment is a uniaxially stretched film, the stretching ratio in the other direction in the film plane (TD direction of the thermoplastic release film) is preferably 4.0 times or more, more preferably 4.5 times or more, and even more preferably 5.0 times or more. When it is a uniaxially stretched film, by setting the stretching ratio in the TD direction to such a relatively high stretching ratio, the above-mentioned storage modulus E' tends to be easily achieved with good reproducibility. Note that when only the stretching ratio in the MD direction is set to such a relatively high stretching ratio, the anisotropy of the film becomes too large, making it more likely to shrink in the TD direction, and therefore heat resistance tends to deteriorate. On the other hand, when the thermoplastic release film of the present embodiment is a biaxially stretched film, from the viewpoint of easily achieving the above-mentioned storage modulus E' with good reproducibility, the stretching ratio in one direction in the film plane (MD direction of the thermoplastic release film) is preferably 2.5 times or more, more preferably 3.0 times or more, and the stretching ratio in the other direction in the film plane perpendicular thereto (TD direction of the thermoplastic release film) is preferably 2.5 times or more, more preferably 3.0 times or more. In the case of a biaxially stretched film, by setting the stretching ratio in both the MD direction and the TD direction to 2.5 times or more, the above-mentioned storage modulus E' tends to be easily achieved with good reproducibility.

[0070] The conditions for the post-heat treatment (annealing 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, 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.

[0071] 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, the thickness 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 uneven 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.

[0072] By adopting the above-described configuration, the thermoplastic release film of this embodiment not only exhibits excellent releasability between the encapsulating resin and the mold and mold followability, 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 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.

[0073] 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 miniaturized packages, thinner packages, higher integration, higher productivity, and lower costs. The compression method eliminates the need for gates and runners used in the transfer method and achieves nearly 100% resin utilization efficiency, thereby reducing costs and waste.

[0074] 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, which 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 mold resin M is poured into the cavity C of the lower mold D2. The mold 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 the semiconductor element to the mold 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, and the substrate 11 after resin sealing can be easily released from the mold D. 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. [Example]

[0075] 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.

[0076] 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 point: 247°C, melt flow rate: 14 g / 10 min (JIS K7210:1999 compliant, 300°C, 1.2 kg load)) (A-2) Ethylene-tetrafluoroethylene copolymer (AGC Corporation, Fluon (registered trademark) ETFE, C-88AXP, melting point: 260°C) (A-3) Ethylene-tetrafluoroethylene copolymer (AGC Corporation, Fluon (registered trademark) LM-ETFE, LM-720AP, melting point: 225°C) (A-4) 4-methyl-1-pentene (co)polymer (manufactured by Mitsui Chemicals, Inc., TPX (registered trademark), MX004, melting point: 228°C) (A-5) General-purpose α-polystyrene (manufactured by Toyo Styrene Co., Ltd., Toyo Styrol (registered trademark), HRM61) (Resin B) (B-1) Alkyl methacrylate-alkyl acrylate copolymer, trade name "Metablen L-1000" manufactured by Mitsubishi Chemical Corporation, melt flow rate: 2.4 g / 10 min (JIS K7210:1999 compliant, 230°C, 2.16 kg load)

[0077] 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 listed 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 with 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 1.0 times in the MD direction and 5.0 times in the TD direction (total stretching ratio: 5.0 times) in a sequential biaxial stretching machine at 120°C, 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.

[0078] Examples 2 to 5 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 the stretching ratios were changed to those shown in Table 1, and thermoplastic release films of Examples 2 to 5 were obtained, respectively.

[0079] (Examples 6 to 7) The same procedure as in Example 5 was carried out except that the compositions and blending ratios were changed to those shown in Table 1, and thermoplastic release films of Examples 6 and 7 were obtained.

[0080] (Examples 8 to 9) The same procedure as in Example 5 was carried out except that the average thickness of the thermoplastic release film was changed to that shown in Table 1, and thermoplastic release films of Examples 8 and 9 were obtained.

[0081] Examples 10 to 12 The same procedure as in Example 1 was carried out except that the stretching ratio was changed to that shown in Table 1, and thermoplastic release films of Examples 10 to 12 were obtained.

[0082] (Comparative Examples 1 and 2) The same procedure as in Example 1 was carried out except that the stretching ratio was changed to that shown in Table 2, and thermoplastic release films of Comparative Examples 1 and 2 were obtained.

[0083] (Comparative Example 3) The same procedure as in Example 5 was carried out except that the composition and blending ratio were changed to those shown in Table 2, to obtain a thermoplastic release film of Comparative Example 3 having an average thickness of 50 μm.

[0084] The conditions for measuring the physical properties of each of the obtained thermoplastic release films are as follows.

[0085] [Film thickness] For each thermoplastic release film, the thickness was measured at nine random points, and the average value was expressed.

[0086] [Dynamic viscoelasticity measurement] Using each of the obtained thermoplastic release films, dynamic viscoelasticity measurements were performed under the following conditions based on JIS K 7244-4:1999 to determine the storage modulus E' (MPa) in the MD direction and the storage modulus E' (MPa) in the TD direction. In this measurement, strip-shaped test pieces cut to a length of 15 mm in the direction to be measured and a width of 5 mm in the direction approximately perpendicular to this were used, and the storage modulus (MPa) was measured when the temperature was raised from room temperature to 200°C at a heating rate of 5°C / min. Measurement equipment: TA Instruments - Waters LLC, RSA G2 Measurement conditions were set as follows: sampling rate 1.0 pts / s, strain 0.3%, and frequency 1 Hz, and the storage modulus (MPa) at 100°C to 160°C was calculated from the obtained graph.

[0087] The performance of each of the obtained thermoplastic release films was evaluated as follows. (Mold test) 1, a thermoplastic release film 100 is 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 is 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 is 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.

[0088] <Sealing conditions> Mold temperature: 175℃ Cavity size: 220mm x 55mm Final depth of cavity: 0.5mm Curable resin: Sumikon EME G770H type F Ver.GR (manufactured by Sumitomo Bakelite Co., Ltd.) Vacuum level when following the cavity surface: -85kPa Vacuum level when removing bubbles from hardening resin: -80kPa Curable resin bubble removal time: 10 seconds Clamping time: 120 seconds Molding pressure: 8.0 MPa

[0089] (Mold releasability) Very Good (A): The thermoplastic release film was easily peeled off from the semiconductor package. Good (B): The thermoplastic release film peeled off from the semiconductor package with some resistance. Bad (C): The thermoplastic release film did not peel off from the semiconductor package and stuck to it.

[0090] (heat resistance) Very Good (A): When the thermoplastic release film was attached to the mold, it was attached evenly and no wrinkles were formed. Good (B): Slight wrinkles occurred when the thermoplastic release film was attached to the mold. Bad (C): The thermoplastic release film has many wrinkles or tears.

[0091] (mold followability) Very Good (A): There is absolutely no resin chipping on the semiconductor package. Good (B): There was some resin chipping at the edge of the semiconductor package. Bad (C): The thermoplastic release film did not adhere to the mold, and vacuum adsorption was not possible.

[0092] (bleedability) Each test film was left in an oven at 70°C for 72 hours, and the components that bled out 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

[0093] [Table 1]

[0094] [Table 2] [Industrial Applicability]

[0095] 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. [Explanation of symbols]

[0096] 100 ···Thermoplastic release film 11 - Substrate on which semiconductor elements are mounted C···cavity D···Mold D1: Upper mold D2: Lower mold M···Molding resin

Claims

1. A crystalline resin (A) having a melting point of 180°C or higher; An acrylic copolymer (B), The minimum value of the storage modulus E' at 100°C to 160°C is 10 MPa or more in both one direction in the film plane and the other direction in the film plane perpendicular to the one direction in the film plane. Thermoplastic release film for semiconductor encapsulation processes.

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

3. The crystalline resin (A) contains 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). The thermoplastic release film for semiconductor encapsulation process according to claim 1 .

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

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

6. The crystalline resin (A) has a melt flow rate (MFR, 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. The thermoplastic release film for semiconductor encapsulation process according to claim 1 .

7. 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 different structure. The thermoplastic release film for semiconductor encapsulation process according to claim 1 .

8. 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. The thermoplastic release film for semiconductor encapsulation process according to claim 1 .

9. 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. The thermoplastic release film for semiconductor encapsulation process according to claim 1 .

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

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

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

13. It is a uniaxially or biaxially stretched film. The thermoplastic release film for semiconductor encapsulation process according to claim 1 .

14. Release film for molding The thermoplastic release film for semiconductor encapsulation process according to claim 1 .

15. In the manufacture of semiconductor packages, a semiconductor element is placed in a mold and sealed with hardening resin to form a resin-sealed portion. The thermoplastic release film for semiconductor encapsulation process according to claim 1 .

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