Mold release film and method for manufacturing semiconductor package

Abstract

Provided is a mold release film including a mold release layer and a base material layer, the elongation rate at break of the mold release layer being 120% or greater, and the average thickness of the mold release layer being 5 μm or greater.

Description

Release film and method for manufacturing semiconductor package

[0001] The present disclosure relates to a method for manufacturing a release film and a semiconductor package.

[0002] Semiconductor chips are typically sealed with resin to protect them from the outside air and are mounted on a substrate as a molded product called a package. Conventionally, molded products are molded as individual package molded products, with each chip connected via a runner, which is a flow path for the sealing resin. In this case, the mold structure and the addition of a mold release agent to the sealing resin ensure that the molded product can be easily released from the mold.

[0003] On the other hand, due to demands for smaller packages and higher pin counts, there has been an increase in packages such as the Ball Grid Array (BGA) type, Quad Flat Non-leaded (QFN) type, and Wafer Level Chip Size Package (WL-CSP) type. In the QFN type, a resin release film is used to ensure standoff and prevent burrs from forming on the terminals, while in the BGA and WL-CSP types, a resin release film is used to improve the releasability of the package from the mold (see, for example, Patent Document 1). This molding method using a release film is called "film-assisted molding."

[0004] Japanese Patent Application Laid-Open No. 2002-158242

[0005] Patent Document 1 discloses a release film in which a layer responsible for releasability from a molded article is mainly made of an acrylic resin. From the viewpoint of releasability, it is preferable to employ a release layer made of an acrylic resin.

[0006] However, in recent years, package structures have become more complex, and precision in the package structure is also required. Therefore, release films may be required to have properties other than releasability. For example, as package structures become more complex, a part of the release layer is more likely to break when the package is peeled off from the release film, and as a result, a phenomenon in which a part of the broken release layer adheres to the package (hereinafter also referred to as "release layer residue") is more likely to occur. It is desirable to reduce the occurrence of such release layer residue.

[0007] The present disclosure has been made in consideration of the above circumstances, and an object of the present disclosure is to provide a release film that can reduce the occurrence of release layer residue and a method for manufacturing a semiconductor package using this release film.

[0008] The present disclosure includes the following aspects. <1> A release film comprising a release layer and a substrate layer, wherein the release layer has a breaking elongation rate of 120% or more and an average thickness of 5 μm or more. <2> The release film according to <1>, wherein the release layer contains a urethane resin. <3> A release film comprising a release layer and a substrate layer, wherein the release layer contains a urethane resin, and the urethane resin contains a structural unit 1 having an alkylene oxide skeleton. <4> The release film according to any one of <1> to <3>, wherein the substrate layer is a polyester film. <5> The release film according to <2>, wherein the urethane resin contains a structural unit 1 having an alkylene oxide skeleton. <6> The release film according to <3> or <5>, wherein the structural unit 1 contains at least one of a structural unit 2 having an ethylene oxide skeleton and a structural unit 3 having a propylene oxide skeleton. <7> The release film according to any one of <3>, <5> and <6>, wherein the urethane resin further includes a structural unit 4 having a urethane bond at both ends of a divalent linking group, and the total content of the structural unit 2 and the structural unit 3 is 50 mol % or more relative to the total of the structural unit 1 and the structural unit 4. <8> The release film according to any one of <3>, <5>, <6> and <7>, wherein the structural unit 1 includes the structural unit 2 and the structural unit 3, and the ratio of the structural unit 2 to the structural unit 3, that is, structural unit 2:structural unit 3, is 10:90 to 60:40. <9> The release film according to any one of <2>, <3> and <5> to <8>, wherein the urethane resin includes a structural unit 4 having a urethane bond at each end of a divalent linking group, and the divalent linking group is a hexamethylene group, a 2,2,4-trimethylhexamethylene group, a 2,4,4-trimethylhexamethylene group, a pentamethylene group, or a tetramethylene group. <10> The release film according to any one of <1> to <9>, wherein the release film is used for transfer molding or compression molding. <11> A method for producing a semiconductor package, comprising performing transfer molding or compression molding using the release film according to any one of <1> to <10>.

[0009] According to the present disclosure, there are provided a release film capable of reducing the occurrence of release layer residue and a method for manufacturing a semiconductor package using this release film.

[0010] FIG. 2 is a diagram showing a test piece used to measure the breaking elongation (%) of a release layer.

[0011] Embodiments of the present invention are described in detail below. However, the present invention is not limited to the following embodiments. In the present disclosure, numerical ranges indicated using "to" include the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in the present disclosure, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another staged numerical range. Furthermore, in numerical ranges described in the present disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the Examples. In the present disclosure, each component may contain multiple corresponding substances. When multiple substances corresponding to each component are present in a composition, the content or amount of each component means the total content or amount of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, the term "layer" includes cases where, when the region in which the layer exists is observed, the layer is formed over the entire region, as well as cases where the layer is formed only in a portion of the region.

[0012] In the present disclosure, the average thickness of a layer or film (also referred to as the average thickness) is a value obtained by measuring the thickness of five points on the target layer or film and calculating the arithmetic mean value. The thickness of a layer or film can be measured using a micrometer or the like. In the present disclosure, when the thickness of a layer or film can be measured directly, it is measured using a micrometer. On the other hand, when measuring the thickness of a single layer or the total thickness of multiple layers, it may be measured by observing the cross section of the film using an electron microscope.

[0013] Hereinafter, the release film of the present disclosure will be described in terms of a first embodiment and a second embodiment. Note that the release film of the present disclosure is not limited to the following first and second embodiments. In addition, the configurations that can be adopted in the first and second embodiments may be combined as appropriate.

[0014] [First embodiment] <Release film> A release film in a first embodiment of the present disclosure includes a release layer and a base layer, wherein the release layer has a breaking elongation of 120% or more and an average thickness of 5 μm or more. The break elongation of the release layer is 120% or more.

[0015] The release film of the first embodiment, by adopting the above-described configuration, can reduce the occurrence of release layer residue. The reason for this is not clear, but is presumed as follows. In the release film of the present disclosure, the release layer has a breaking elongation percentage of 120% or more and an average thickness of 5 μm or more, so that the film has excellent extensibility and the release layer is less likely to break when the semiconductor package is peeled off. As a result, the release layer is less likely to adhere to the semiconductor package, and the occurrence of release layer residue can be reduced.

[0016] The release film of the present disclosure is preferably used for semiconductor molding. More specifically, it is preferably used when manufacturing a semiconductor package using an encapsulant, with the base layer being brought into contact with a mold used in resin molding of the semiconductor package, and the release layer being positioned on the side of the semiconductor chip to be molded.

[0017] [Release Layer] The release film of the present disclosure includes a release layer. The configuration of the release layer is not particularly limited as long as it has a breaking elongation of 120% or more and an average thickness of 5 μm or more.

[0018] (Rupture elongation of release layer) The rupture elongation of the release layer is 120% or more, preferably 150% or more, and more preferably 180% or more. The rupture elongation of the release layer can be adjusted, for example, by the composition of the resin components constituting the release layer, the amount of the crosslinking agent described below, etc. The upper limit of the rupture elongation of the release layer is not particularly limited, and may be, for example, 800% or less, 500% or less, or 300% or less.

[0019] The breaking elongation (%) of the release layer is measured as follows. First, a test piece having the shape shown in FIG. 1 is prepared using a release film. The numerical values ​​in FIG. 1 are in mm. A tensile test is performed by gripping both ends of this test piece with a testing machine. The measurement is performed under conditions of 170°C, and the tensile speed is 200 mm / min. The breaking elongation of the release layer is calculated using the following formula from the gauge length A of the sample before the test (the length of the 10 mm wide portion of the test piece shown in FIG. 1: 40 mm) and the gauge length B when the release layer breaks.

[0020]

[0021] The breaking elongation of the release layer of the release film can be measured using, for example, a "Tensilon Tensile Tester RTA-100" manufactured by Orientec Co., Ltd., a "Tensilon Universal Tester RTG-1210" manufactured by A&D Co., Ltd., or a similar tester having a gripper.

[0022] (Average Thickness of Release Layer) The average thickness of the release layer is 5 μm or more, and may be 5 μm to 40 μm, or may be 5 μm to 30 μm.

[0023] The release layer may contain a resin component. The resin component of the release layer is not particularly limited, and examples thereof include urethane resin, acrylic resin, silicone resin, etc. In particular, from the viewpoint of achieving an excellent breaking elongation of the release layer, it is preferable that the release layer contains a urethane resin.

[0024] In the present disclosure, the urethane resin is preferably a resin component having a urethane bond in the main chain of the resin, and more preferably a resin component having a plurality of structural units containing a urethane bond in the main chain of the resin.

[0025] The release layer may contain only one type of resin component, or may contain two or more types of resin components. For example, the release layer may be a layer containing only a urethane resin as the resin component, or may be a layer containing two types of resin components, a urethane resin and an acrylic resin, or a urethane resin and a silicone resin.

[0026] The release layer may contain a cross-linked urethane resin as the urethane resin, or may contain a cross-linked acrylic resin as the acrylic resin. From the viewpoint of reducing the occurrence of release layer residue and balancing release properties, it is preferable that the release layer contain a cross-linked urethane resin as the urethane resin. In the present disclosure, the cross-linked urethane resin refers to a resin in which a urethane resin is cross-linked with a cross-linking agent, and the cross-linked acrylic resin refers to a resin in which an acrylic resin is cross-linked with a cross-linking agent.

[0027] The urethane resin may be a resin obtained by reacting a polyol compound having multiple hydroxy groups with a polyisocyanate compound having multiple isocyanate groups. The urethane resin may contain a compound having multiple urethane bonds in the main chain, or may contain a compound having multiple urethane bonds in the main chain and a hydroxy group at at least one of both ends of the main chain.

[0028] The urethane resin preferably contains a structural unit 1 having an alkylene oxide skeleton. The urethane resin may contain a plurality of structural units 1. The urethane resin may contain only one type of structural unit 1, or may contain two or more types of structural units 1. When the urethane resin contains a plurality of each of two or more types of structural units 1, the urethane resin may be a block polymer of structural unit 1, or may be a random polymer of structural unit 1.

[0029] The structural unit 1 having an alkylene oxide skeleton preferably contains at least one of a structural unit 2 having an ethylene oxide skeleton and a structural unit 3 having a propylene oxide skeleton, and more preferably contains both the structural unit 2 and the structural unit 3.

[0030] The total content of structural unit 2 and structural unit 3 may be 50 mol% or more, 80 mol% to 100 mol%, or 90 mol% to 100 mol% relative to the total amount of structural unit 1. In the present disclosure, the content of each structural unit is, for example, １ It can be calculated from H NMR measurements.

[0031] Structural unit 1 includes structural unit 2 and structural unit 3, and the ratio of structural unit 2 to structural unit 3, structural unit 2:structural unit 3, may be 10:90 to 60:40, 10:90 to 55:45, or 15:85 to 50:50.

[0032] The urethane resin preferably further contains a structural unit 4 having a urethane bond at each end of a divalent linking group (i.e., *-urethane bond-divalent linking group-urethane bond-*, where * represents the bonding position). The urethane resin more preferably contains a structural unit 1 having an alkylene oxide skeleton in addition to the structural unit 4, and even more preferably contains both a structural unit 2 having an ethylene oxide skeleton and a structural unit 3 having a propylene oxide skeleton.

[0033] The urethane resin further contains structural unit 4, and the total content of structural unit 2 and structural unit 3 relative to the total of structural unit 1 and structural unit 4 may be 50 mol% or more, may be 80 mol% to 99.5 mol%, may be 90 mol% to 99 mol%, or may be 95 mol% to 99 mol%.

[0034] The divalent linking group contained in structural unit 4 is preferably a substituted or unsubstituted hydrocarbon group, and more preferably a linear or branched hydrocarbon group that does not contain a ring structure. The divalent linking group may have 2 to 20 carbon atoms, 3 to 15 carbon atoms, or 4 to 10 carbon atoms.

[0035] Examples of the divalent linking group contained in the structural unit 4 include a hexamethylene group, a 2,2,4-trimethylhexamethylene group, a 2,4,4-trimethylhexamethylene group, a pentamethylene group, and a tetramethylene group.

[0036] Structural unit 4 may be a structural unit derived from a diisocyanate compound, or may be a structural unit derived from hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, pentamethylene diisocyanate, or tetramethylene diisocyanate.

[0037] The content of structural unit 4 may be 50 mol% or less, 0.5 mol% to 20 mol%, 1 mol% to 10 mol%, or 1 mol% to 5 mol%, relative to all structural units contained in the urethane resin.

[0038] The acrylic resin is preferably an acrylic copolymer obtained by copolymerizing a low glass transition temperature (Tg) monomer such as butyl acrylate, ethyl acrylate, or 2-ethylhexyl acrylate as a main monomer with a functional group monomer such as acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxyethyl acrylate, 4-hydroxybutyl acrylate, acrylamide, or acrylonitrile.

[0039] Whether the resin component contains a urethane resin, an acrylic resin, or the like may be confirmed by IR measurement, NMR measurement, or the like.

[0040] Examples of crosslinking agents used in the production of crosslinked urethane resins or crosslinked acrylic resins include known crosslinking agents such as isocyanate compounds, melamine compounds, and epoxy compounds, and among these, isocyanate compounds are preferred.

[0041] The crosslinked urethane resin or crosslinked acrylic resin produced using the above-mentioned crosslinking agent has a gently spreading network structure. Therefore, when the above-mentioned resin is used as a resin component of the release layer, the stretchability of the release layer is improved and the inhibition of the stretchability of the base layer is suppressed. As a result, the conformability of the release film to the mold tends to be improved.

[0042] From the viewpoint of the balance between the breaking elongation of the release layer and the conformability of the release film to the mold, the crosslinking agent is preferably a bifunctional to tetrafunctional polyfunctional crosslinking agent, and more preferably a bifunctional or trifunctional polyfunctional crosslinking agent. As the polyfunctional crosslinking agent, a bifunctional or trifunctional isocyanate compound is preferred. Examples of the bifunctional or trifunctional isocyanate compound include 2,6-toluene diisocyanate, 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and 1,6-hexane diisocyanate.

[0043] The cross-linked urethane resin preferably has a urethane bond in the main chain and a urethane bond in a side chain that cross-links the main chains, and more preferably has a plurality of urethane bonds in the main chain and a urethane bond in a side chain that cross-links the main chains.

[0044] From the viewpoint of achieving excellent elongation at break of the release layer and excellent conformability of the release film to the mold, it is preferable that the resin component contains a cross-linked urethane resin. Furthermore, the content of the cross-linked urethane resin relative to the entire resin component may be 50% by mass to 100% by mass, 70% by mass to 100% by mass, or 90% by mass to 100% by mass.

[0045] The amount of crosslinking agent used in the production of a crosslinked urethane resin or a crosslinked acrylic resin (preferably the production of a crosslinked urethane resin) may be 10 parts by mass to 50 parts by mass, or 15 parts by mass to 40 parts by mass, relative to 100 parts by mass of the resin to be crosslinked, or from the viewpoint of releasability from a semiconductor package, may be 20 parts by mass to 30 parts by mass.

[0046] When the release layer contains a resin component, the content of the resin component may be 50% by mass to 100% by mass, 80% by mass to 100% by mass, or 90% by mass to 100% by mass, based on the entire release layer.

[0047] (Other Components) The release layer may further contain other components other than the resin component, such as a solvent, an anchoring improver, a crosslinking accelerator, an antistatic agent, a colorant, and inorganic particles, as necessary, as long as the effects of the present invention are achieved.

[0048] [Substrate Layer] The release film of the present disclosure includes a substrate layer. The substrate layer is not particularly limited and can be appropriately selected from resin-containing substrate layers used in the relevant technical field. From the viewpoint of improving conformability to the shape of the mold, it is preferable to use a resin-containing substrate layer with excellent stretchability. Considering that the molding of the encapsulating material is performed at high temperatures (approximately 100°C to 200°C), it is desirable for the substrate layer to have heat resistance at or above this temperature. Furthermore, from the viewpoint of suppressing the occurrence of wrinkles in the encapsulating resin and tears in the release film when the release film is attached to the mold and when the resin flows during molding, it is preferable to select the material for the substrate layer taking into account the elastic modulus, elongation, etc. at high temperatures.

[0049] The material of the substrate layer is preferably a polyester resin from the viewpoints of heat resistance and elastic modulus at high temperatures. Examples of polyester resins include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, and copolymers and modified resins thereof. The substrate layer is preferably a polyester resin molded into a sheet, more preferably a polyester film, and from the viewpoint of mold conformability, preferably a biaxially oriented polyester film.

[0050] The average thickness of the base layer is not particularly limited, but is preferably 5 μm to 300 μm, more preferably 10 μm to 200 μm, and even more preferably 20 μm to 100 μm. When the average thickness is 5 μm or more, the layer tends to be easy to handle and less prone to wrinkles. When the average thickness is 300 μm or less, the layer tends to be excellent in conformity to the mold during molding, and thus the occurrence of wrinkles and the like in the molded semiconductor package tends to be suppressed.

[0051] [Others] The substrate layer is a layer located on the mold surface side, and depending on the material used, a greater peeling force may be required to peel the release film from the mold. When using a material that is difficult to peel from the mold for the substrate layer, it is preferable to adjust the material so that the release film is easily peeled from the mold. For example, the surface of the substrate layer opposite to the release layer, i.e., the surface of the substrate layer facing the mold, may be subjected to a surface treatment such as a matte finish to improve releasability from the mold, or a separate release layer (second release layer) may be provided. The material for the second release layer is not particularly limited as long as it satisfies the heat resistance, releasability from the mold, etc., and the same material as the release layer may be used. The average thickness of the second release layer is not particularly limited and may be 0.1 μm to 100 μm.

[0052] If necessary, a layer such as an anchoring improving layer for the release layer or the second release layer, an antistatic layer, or a colored layer may be provided between the release layer and the substrate layer, or between the substrate layer and the second release layer. A preferred layer configuration is a three-layer structure in which a substrate layer, an antistatic layer, and a release layer are provided in this order. The antistatic layer may contain an antistatic polymer such as a quaternary ammonium salt-containing polymer or a polythiophene-based polymer.

[0053] The total thickness of the release film is preferably 350 μm or less, more preferably 200 μm or less, from the viewpoint of conformability to the mold, and is preferably 10 μm or more, more preferably 20 μm or more, from the viewpoint of handleability.

[0054] Second Embodiment <Release Film> A release film in a second embodiment of the present disclosure includes a release layer and a substrate layer, the release layer includes a urethane resin, and the urethane resin includes a structural unit 1 having an alkylene oxide skeleton.

[0055] The release film of the second embodiment, by adopting the above-described configuration, can reduce the occurrence of release layer residue. The reason for this is not clear, but is presumed as follows. In the release film of the present disclosure, the release layer contains a urethane resin, and the urethane resin contains structural unit 1 having an alkylene oxide skeleton, which provides excellent stretchability and makes it difficult for a portion of the release layer to break when the semiconductor package is peeled off. As a result, it becomes difficult for a portion of the release layer to adhere to the semiconductor package, and the occurrence of release layer residue can be reduced.

[0056] [Method for producing release film] The release film of the present disclosure can be produced by a known method. For example, the release film of the present disclosure can be produced by applying a release layer-forming composition to one side of a substrate layer and drying it. The release layer-forming composition may contain a resin component and other components that are added as desired. For example, the release layer-forming composition may contain a urethane resin, a crosslinking agent, and other components as necessary. Resin components such as

[0057] [Preparation of Release Layer-Forming Composition] The method for preparing the release layer-forming composition is not particularly limited, and for example, a method of dispersing or dissolving a resin component or the like in a solvent can be mentioned, and the release layer-forming composition can be prepared using a known composition preparation method. The solvent used for preparing the release layer-forming composition is not particularly limited, and it is preferably an organic solvent that can dissolve or disperse the resin component or the like. Examples of the organic solvent include toluene, methyl ethyl ketone, ethyl acetate, etc.

[0058] [Application and Drying] The method for applying the release layer-forming composition to one side of the base layer is not particularly limited, and known application methods such as roll coating, bar coating, and kiss coating can be used. When applying the release layer-forming composition, it is preferable to apply it so that the average thickness of the composition layer (release layer) after drying is 5 μm or more. The method for drying the applied release layer-forming composition is not particularly limited, and known drying methods can be used. For example, it may be a method of drying at 50° C. to 150° C. for 0.1 minutes to 60 minutes. When the release layer-forming composition contains a urethane resin and a crosslinking agent, a crosslinking reaction between the urethane resin and the crosslinking agent may be promoted by the drying treatment, thereby forming a release layer containing a crosslinked urethane resin.

[0059] [Uses] The release film of the present disclosure can be used for molding semiconductor packages, and can be suitably used for transfer molding or compression molding.

[0060] <Method for Manufacturing Semiconductor Package> A method for manufacturing a semiconductor package according to the present disclosure includes carrying out transfer molding or compression molding using the release film according to the present disclosure described above.

[0061] In transfer molding, for example, a semiconductor chip is placed in a mold of a transfer molding machine, and a release film is placed on the other mold, and the release film is made to conform to the shape of the mold by vacuum suction or the like. Next, the mold is closed, and a molten thermosetting encapsulant (e.g., epoxy resin) is injected into the heated mold by a transfer method, and the encapsulant is cured to form a semiconductor package. After that, the mold is opened, and the molded semiconductor package is removed.

[0062] In compression molding, for example, a release film is placed on the mold of a compression molding device, and the release film is made to conform to the shape of the mold by vacuum suction or the like. Next, a thermosetting encapsulant (e.g., epoxy resin) for the semiconductor package is placed in the mold, a semiconductor chip is placed on top of it, and the encapsulant is hardened by compressing the mold while heating, thereby molding the semiconductor package. The mold is then opened, and the molded semiconductor package is removed.

[0063] The method for manufacturing a semiconductor package according to the present disclosure uses the release film according to the present disclosure. This makes it difficult for a portion of the release layer to break when the molded semiconductor package is peeled off from the release film to remove the semiconductor package. As a result, it is difficult for a portion of the release layer to adhere to the semiconductor package, and the occurrence of residual release layer can be reduced.

[0064] The present invention will be specifically described below with reference to examples, although the present invention is not limited to these examples.

[0065] (Synthesis of Acrylic Resin) Acrylic resins were synthesized by copolymerizing the monomers shown in Table 1 below in the amounts (parts by mass) shown in Table 1 through solution polymerization. In Table 1, BA stands for butyl acrylate, and 4-HBA stands for 4-hydroxybutyl acrylate. The number average molecular weight Mn and weight average molecular weight Mw of the obtained acrylic resin were measured by gel permeation chromatography (GPC) in terms of standard polystyrene. The Mn and Mw of the obtained acrylic resin are shown in Table 1.

[0066]

[0067] Example 1 A release layer-forming composition was prepared by mixing 100 parts by mass of a urethane resin (Lions Specialty Chemicals Co., Ltd.: US-1353H) with a toluene solution having a solids content of 15% by mass, which was prepared by adding 20 parts by mass of Coronate L (product name, Tosoh Corporation) as a crosslinking agent to toluene. A biaxially oriented polyethylene terephthalate film (Unitika Co., Ltd.: S-38) having an average thickness of 38 μm that had been subjected to a corona treatment was used as the substrate layer. Thereafter, the release layer-forming composition was applied to one side of the substrate layer using a roll coater so that the average thickness after drying was 5 μm, and then dried to form a release layer, and a release film was obtained.

[0068] Example 2 A release film was produced in the same manner as in Example 1, except that the average thickness of the release layer after drying was set to 10 μm.

[0069] Example 3 A release film was produced in the same manner as in Example 1, except that the average thickness of the release layer after drying was set to 25 μm.

[0070] Example 4 A release film was produced in the same manner as in Example 2, except that the amount of crosslinking agent was 40 parts by mass per 100 parts by mass of the urethane resin.

[0071] Example 5 A release film was produced in the same manner as in Example 4, except that the average thickness of the release layer after drying was set to 15 μm.

[0072] Comparative Example 1 A release film was produced in the same manner as in Example 3, except that 100 parts by mass of a synthesized acrylic resin was used instead of 100 parts by mass of the urethane resin, and the amount of the crosslinking agent was 10 parts by mass.

[0073] Comparative Example 2 A release film was produced in the same manner as in Example 2, except that 100 parts by mass of a synthesized acrylic resin was used instead of 100 parts by mass of the urethane resin.

[0074] Comparative Example 3 A release film was produced in the same manner as in Comparative Example 2, except that the average thickness of the release layer after drying was set to 20 μm.

[0075] Comparative Example 4 A release film was produced in the same manner as in Comparative Example 2, except that the average thickness of the release layer after drying was set to 25 μm.

[0076] (Elongation at Break of Release Layer) The elongation at break of the release layer at 170° C. was measured by the method described above. For the measurement, a Tensilon tensile tester RTA-100 manufactured by Orientec Co., Ltd. was used. The results are shown in Table 2.

[0077] (Evaluation of releasability from EMC) The releasability from epoxy molding compound (EMC), which is an encapsulant, was evaluated as follows. A heat and pressure treatment was carried out with the release layer of the release film in contact with the encapsulant (Showa Denko Materials K.K.: product name "CEL-9750ZHF10"). The temperature was 175°C, the pressure was 6 KPa, and the treatment time was 4 minutes. As an index of the releasability of the release film from the encapsulant after the heat and pressure treatment, the peel force was measured when a peel test was carried out at a peel angle of 180° and a peel speed of 1000 mm / min. From the measured peel force values, the releasability was evaluated according to the following criteria. The results are shown in Table 2. Evaluation A or B indicates good releasability. - Evaluation criteria - A: Less than 150 mN / 50 mm B: 150 mN / 50 mm or more but less than 250 mN / 50 mm C: 250 mN / 50 mm or more

[0078] (Presence or absence of release layer residue) A SUS plate (width 5 mm, thickness 0.6 mm) was brought into contact with the base layer side of the release film. A SUS plate (width 50 mm, thickness 0.6 mm) was placed on the release layer side, and a heat and pressure treatment was performed at 170°C and 32 MPa for 5 minutes. After the heat and pressure treatment, the release film was peeled off from the SUS plate on the release layer side. Thereafter, the presence or absence of release layer residue on the SUS plate placed on the release layer side was observed visually and with a Keyence Corporation "Digital Microscope VHX-7000" (20x magnification), and evaluated according to the following criteria. The results are shown in Table 2. A: No release layer residue was observed visually or with a microscope. B: Release layer residue was observed at least visually or with a microscope.

[0079]

[0080] As shown in Table 2, no release layer residue was observed on the SUS plate in Examples 1 to 5. On the other hand, release layer residue was observed on the SUS plate in Comparative Examples 1 to 4.

[0081] Example 6 A synthetic urethane resin 1 was prepared, having a structural unit having a propylene oxide skeleton (PO), a structural unit having an ethylene oxide skeleton (EO), and a structural unit derived from hexamethylene diisocyanate (HDI) in the molar ratios shown in Table 3. The molar ratios of each structural unit in synthetic urethane resin 1 were as follows: １ The value was calculated from the peak area ratio of H NMR. １ The H NMR peaks are due to the solvent, other components, etc. １ Because the peaks partially overlapped with those of H NMR, peaks that overlapped as little as possible were selected, and the molar ratio of each constituent unit was calculated. 100 parts by mass of synthetic urethane resin 1 was mixed with a toluene solution with a solids content of 15% by mass prepared by adding 20 parts by mass of Coronate L (product name, Tosoh Corporation) as a crosslinking agent to toluene to prepare a release layer-forming composition. A corona-treated biaxially oriented polyethylene terephthalate film (Unitika Co., Ltd.: S-38) having an average thickness of 38 μm was used as the base layer. Thereafter, using a roll coater, the release layer-forming composition was applied to one side of the base layer so that the average thickness after drying was 5 μm, and then dried to form a release layer, and a release film was obtained.

[0082] Example 7 A release film was produced in the same manner as in Example 1, except that the average thickness of the release layer after drying was set to 10 μm.

[0083] Example 8 A release film was produced in the same manner as in Example 1, except that the average thickness of the release layer after drying was set to 25 μm.

[0084] Example 9 A release film was produced in the same manner as in Example 7, except that the amount of crosslinking agent was 40 parts by mass per 100 parts by mass of the urethane resin.

[0085] Example 10 A release film was produced in the same manner as in Example 9, except that the average thickness of the release layer after drying was 15 μm.

[0086] Example 11 A synthetic urethane resin 2 was prepared, having a structural unit having a propylene oxide skeleton (PO), a structural unit having an ethylene oxide skeleton (EO), and a structural unit derived from hexamethylene diisocyanate (HDI) in the molar ratios shown in Table 3. The molar ratios of each structural unit in the synthetic urethane resin 2 were as follows: １ The value was calculated from the peak area ratio of H NMR. １ The H NMR peaks are due to the solvent, other components, etc. １ Because the peaks partially overlapped with those of H NMR, peaks that overlapped as little as possible were selected, and the molar ratio of each constituent unit was calculated. 100 parts by mass of synthetic urethane resin 2 was mixed with a toluene solution with a solids content of 15% by mass prepared by adding 10 parts by mass of Coronate L (product name, Tosoh Corporation) as a crosslinking agent to toluene to prepare a release layer-forming composition. A corona-treated biaxially oriented polyethylene terephthalate film (Unitika Co., Ltd.: S-38) having an average thickness of 38 μm was used as the substrate layer. Then, using a roll coater, the release layer-forming composition was applied to one side of the substrate layer so that the average thickness after drying was 15 μm, and dried to form a release layer, and a release film was obtained.

[0087] Example 12 A release film was produced in the same manner as in Example 11, except that the amount of crosslinking agent was 20 parts by mass per 100 parts by mass of the urethane resin.

[0088] Example 13 A release film was produced in the same manner as in Example 11, except that the average thickness of the release layer after drying was set to 25 μm.

[0089] The release films of Examples 6 to 13 were evaluated for the breaking elongation of the release layer, the releasability against EMC, and the amount of the release layer remaining in the film in the same manner as the release films of Examples 1 to 5. The results are shown in Table 4.

[0090]

[0091]

[0092] As shown in Table 4, in Examples 6 to 13, no residual release layer was observed on the SUS plate.

[0093] The disclosure of Japanese Patent Application No. 2022-146410, filed on September 14, 2022, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A release layer and a substrate layer are included, A release film, wherein the release layer has a breaking elongation of 120% or more and an average thickness of 5 μm or more.

2. The release film according to claim 1 , wherein the release layer comprises a urethane resin.

3. A release layer and a substrate layer are included, The release layer comprises a urethane resin, and the urethane resin comprises a structural unit 1 having an alkylene oxide skeleton.

4. The release film according to any one of claims 1 to 3, wherein the base layer is a polyester film.

5. The release film according to claim 2 , wherein the urethane resin comprises a structural unit 1 having an alkylene oxide skeleton.

6. 6. The release film according to claim 3, wherein the structural unit 1 includes at least one of a structural unit 2 having an ethylene oxide skeleton and a structural unit 3 having a propylene oxide skeleton.

7. The urethane resin further comprises a structural unit 4 having a urethane bond at both ends of a divalent linking group, and the total content of the structural unit 2 having an ethylene oxide skeleton and the structural unit 3 having a propylene oxide skeleton is 50 mol % or more relative to the total of the structural unit 1 and the structural unit 4. The release film according to claim 3 or 5.

8. The structural unit 1 includes a structural unit 2 having an ethylene oxide skeleton and a structural unit 3 having a propylene oxide skeleton, and the ratio of the structural unit 2 to the structural unit 3, structural unit 2:structural unit 3, is 10:90 to 60:

40. The release film according to claim 3 or claim 5.

9. The urethane resin includes a structural unit 4 having a urethane bond at each end of a divalent linking group, and the divalent linking group is a hexamethylene group, a 2,2,4-trimethylhexamethylene group, a 2,4,4-trimethylhexamethylene group, a pentamethylene group, or a tetramethylene group. The release film according to any one of claims 2, 3, and 5.

10. The release film according to any one of claims 1 to 3, which is used for transfer molding or compression molding.

11. A method for producing a semiconductor package, comprising carrying out transfer molding or compression molding using the release film according to any one of claims 1 to 3.