Release film for compression molds

Abstract

To provide a release film that retains excellent die shape followability and releasability with reduced failures in appearance, such as wrinkles transferred to a mold resin during compression molding, or resin chipping at the edge.SOLUTION: A release film for semiconductor compression molding has a skewness SSk(R) of surface roughness on one surface (R face) and a skewness SSk(M) of surface roughness on the opposite face (M face), satisfying SSk(R)<SSk(M), the R face side having a surface free energy of 40 mN / m or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a release film used in compression molding, and is particularly suitable for use as a release film for compression molding performed in semiconductor encapsulation processes. [Background technology]

[0002] Semiconductor chips are sealed in resin to protect them from external disturbances such as light, heat, moisture, and physical shock, and are mounted on a substrate as a molded product called a package. Curable resins such as epoxy resin are used to seal semiconductor chips. While the so-called transfer molding method or compression molding method is known as a method for sealing semiconductor chips, the introduction of the compression molding method has been progressing in recent years, driven by trends in semiconductor wafer size, package height reduction, and increased pin count.

[0003] The compression molding method is a process in which molten encapsulating resin is compressed and cured by moving a mold up and down while it is heated. In this process, it is common to insert a release film between the mold and the encapsulating resin to ensure release properties. Ethylene-tetrafluoroethylene copolymer films have been widely used as release films because they have excellent release properties, heat resistance, and conformability to the mold shape. However, because they have high permeability to gases generated from the cured resin and tend to contaminate the mold, research is being conducted on materials with low gas permeability, mainly polyester (Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2002-158242 [Patent Document 2] Japanese Patent Publication No. 2016-92272 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, the release film described in the prior art has problems such as insufficient slipperiness with the mold during molding, resulting in the transfer of wrinkles on the release film to the molded resin, and insufficient fluidity of the molded resin, which causes the resin to not completely fill the mold shape before curing, resulting in resin shortage at the edges and poor appearance.

Means for Solving the Problems

[0006] In order to solve the above problems, a preferred embodiment of the present invention has the following configuration. (1) A release film for semiconductor compression molding, wherein the skewness SSk(R) of the surface roughness on one side surface (R surface) and the skewness SSk(M) of the surface roughness on the opposite surface (M surface) satisfy SSk(R) < SSk(M), and the surface free energy on the R surface side is 40 mN / m or less. (2) A release film for semiconductor compression molding, wherein the skewness SSk(R) of the surface roughness on one side surface (R surface) and the skewness SSk(M) of the surface roughness on the opposite surface (M surface) satisfy SSk(R) < SSk(M), and the contact angle of water on the R surface side is 85° or more. (3) The release film for semiconductor compression molding according to (1) or (2), wherein SSk(R) and SSk(M) satisfy SSk(R) < 0.1 < SSk(M). (4) The release film for semiconductor compression molding according to any one of (1) to (3), wherein the center plane average roughness SRa(R) (μm) of the R surface and the center plane average roughness SRa(M) (μm) of the M surface satisfy 1.0 < SRa(M) < SRa(R). (5) The release film for semiconductor compression molding according to any one of (1) to (4), wherein the center plane area ratio of the R surface is 51% or more and 80% or less. (6) The release film for semiconductor compression molding according to any one of (1) to (5), wherein the Young's modulus at 125°C under air is 50 MPa or more and 500 MPa or less. (7) The release film for semiconductor compression molding according to any one of (1) to (6), wherein the surface free energy on the R surface side is 20 mN / m or more and 30 mN / m or less. (8) The release film for semiconductor compression molding according to any one of (1) to (7), comprising at least a release layer and a base material layer, wherein the base material layer contains polyester as a main component. (9) The release film for semiconductor compression molding according to (8), wherein the polyester in the base material layer contains 0.5 mol% or more and 20 mol% or less of cyclohexanedimethanol residues or butylene glycol residues. (10) The release film for semiconductor compression molding according to (8) or (9), wherein the polyester in the base material layer contains 0.5 mol% or more and 10 mol% or less of isophthalic acid residues among the acid components. (11) The release film for semiconductor compression molding according to any one of (8) to (10), wherein the base material layer contains 0.01% by mass or more and 3% by mass or less of polyalkylene glycol. (12) The release film for semiconductor compression molding according to (11), wherein the polyalkylene glycol is polyethylene glycol. [Advantages of the Invention]

[0007] According to the present invention, by arranging and using a release film in which the skewness SSk(R) of the surface roughness on one surface (R surface) and the skewness SSk(M) of the surface roughness of the opposite surface (M surface) satisfy SSk(R) < SSk(M), and the surface free energy on the R surface side is ￥40 mN / m, during compression molding, the generation of wrinkles and resin chipping can be suppressed, and a release film excellent in mold shape followability and releasability can be provided. Further, by suitably using such a release film as a release film for semiconductor compression molding performed in a semiconductor sealing process, the mass productivity of semiconductor chips can be improved. [Embodiments for Carrying out the Invention]

[0008] A preferred embodiment of the present invention is a release film for semiconductor compression molding, in which the skewness SSk(R) of the surface roughness on one surface (R surface) and the skewness SSk(M) of the surface roughness on the opposite surface (M surface) satisfy SSk(R) < SSk(M), and the surface free energy on the R surface side is 40 mN / m or less.

[0009] <Film properties> For the release film of the present invention, it is preferable that the skewness SSk(R) of the surface roughness on one surface (R surface) and the skewness SSk(M) of the surface roughness on the opposite surface (M surface) satisfy SSk(R) < SSk(M).

[0010] Here, the skewness SSk of the surface roughness is a numerical value that defines the degree of unevenness distribution in the height direction obtained by three-dimensional roughness analysis described later. A negative value indicates that the unevenness is biased in the direction of higher unevenness, and a larger positive value indicates that the unevenness is biased in the direction of lower unevenness. When the value is 0, it indicates that there is no unevenness bias in the height direction.

[0011] The release film used for compression molding is heated and pressed in a state where the surface with high release property is in contact with the fluid mold resin, and the opposite side is in contact with the non-fluid mold. At this time, the surface of the film located on the mold resin side affects the fluidity of the mold resin, and the surface of the film on the opposite side affects the slipperiness with the mold, and these may affect appearance defects such as wrinkles and resin chipping during molding. Here, the wrinkle refers to a state where a wrinkled curve is transferred to the surface of the mold resin, and the resin chipping means an appearance where the end of the wafer is chipped because the mold resin is not sufficiently filled (embedded) up to the end of the wafer.

[0012] As a result of the inventors' intensive studies, it has been found that in such a release film, if the SSk of the surface in contact with the mold resin is small, processing can be performed without inhibiting the flow of the liquid mold resin. Conversely, if the SSk of the opposite mold side is large, it is possible to suppress the contact area with the solid mold, resulting in improved mold slipperiness.

[0013] That is, in the release film of the present invention, the surface free energy of at least the surface (R surface in the present invention) in contact with the mold resin is set to 40 mN / m or less, and a deviation in surface unevenness that satisfies the above is caused between the surface (M surface in the present invention) in contact with the mold on the opposite side, so that excellent mold shape followability and releasability during molding can be maintained while suppressing resin chipping and appearance defects such as wrinkles.

[0014] In particular, compared with other transfer molding methods, the compression mold has a lower press temperature, and the filling of the mold resin is controlled only by the pressure during pressing. Therefore, it is difficult to control the fluidity of the mold resin during pressing and the deformation of the film in contact with the mold. Therefore, by using the release film of the present invention, these problems can be significantly solved.

[0015] Moreover, it is more preferable that SSk(R) and SSk(M) satisfy the following formula (I), further preferable that they satisfy the following formula (II), and particularly preferable that they satisfy the following formula (III). By satisfying these, the deviation in surface unevenness becomes significant, and the effects of the present invention can be further enhanced

[0016] SSk(R) < 0.1 < SSk(M) ···(I) SSk(R) < 0.2 < SSk(M) ···(II) SSk(R) < 0.5 < SSk(M) ···(III) Furthermore, SSk(R) is preferably -17 or more and -0.10 or less, and moreover, SSk(M) is preferably 0.01 or more and 20 or less. When SSk(R) is less than -17, the deviation of surface irregularities may become too large, and uniform mold release properties may not be obtained. When SSk(R) is greater than -0.10, the fluidity of the mold resin decreases, and appearance defects such as resin shortage at the end are likely to occur. Also, SSk(R) is more preferably -5.0 or more and -0.25 or less, and even more preferably -1.5 or more and -0.30 or less. When SSk(M) is less than 0.01, the slipperiness with the contacting mold decreases, and appearance defects such as wrinkles are likely to occur on the flat part of the mold resin. When SSk(M) is greater than 20, the deviation of surface irregularities may become too large, and there is a possibility of leading to breakage or whitening when the film follows the mold. Also, SSk(M) is more preferably 0.10 or more and 10 or less, and even more preferably 0.50 or more and 3.0 or less. In addition, the relationship between the center plane average roughness SRa(R) on the R surface and the center plane average roughness SRa(M) on the M surface preferably satisfies the following formula (IV). Here, the center plane average roughness SRa is a numerical value defined by the average height of irregularities obtained by three-dimensional roughness analysis described later. The smaller the value, the smaller the irregularities, and the larger the value, the larger the irregularities. In the release film of the present invention, when formula (IV) is not satisfied, even if there is a deviation in surface irregularities, the influence may not be sufficient. By satisfying formula (IV), the effect of the deviation of surface irregularities can be enhanced more.

[0017] 1.0 < SRa(M) < SRa(R) ···(IV) Furthermore, SRa(R) is preferably 1.2 μm or more and 7.0 μm or less, more preferably 1.6 μm or more and 5.0 μm or less, and even more preferably 2.0 μm or more and 3.5 μm or less. If SRa(R) is less than 1.2 μm, the surface irregularities may be too small, resulting in insufficient suppression of resin chipping, and if SRa(R) is greater than 7.0 μm, tearing may occur at the surface in contact with the molded resin during mold conformation. Also, SRa(M) is preferably 1.0 μm or more and 3.0 μm or less, more preferably 1.3 μm or more and 2.0 μm or less, and even more preferably 1.4 μm or more and 1.8 μm or less. If SRa(M) is less than 1.0 μm, the surface irregularities may be too small, resulting in insufficient suppression of wrinkles, and if SRa(M) is greater than 3.0 μm, the heat transfer efficiency from the mold may decrease, leading to poor curing of the molded resin and reduced release properties.

[0018] The release film of the present invention preferably has a central surface area ratio SSr of 51% or more and 80% or less on the R surface, more preferably 53% or more and 70% or less, and even more preferably 58% or more and 65% or less. Here, the central surface area ratio SSr is an index that shows the area ratio of the irregularities above the central surface of the rough curved surface. In the case of a surface with many irregularities, the larger the SSr, the more the planar structure before processing exists in terms of area ratio. In particular, in compression molding, the ease with which air escapes is important when vacuuming is performed at the same time as the fluidity of the resin. On the R surface, the deeper the irregularities are and the smaller the area ratio, the more possible it is to create an escape route for air that cannot flow through the resin. If the SSr is less than 51%, the above effect will be insufficient, and wrinkles may occur due to vacuuming. If the SSr exceeds 80%, the unevenness will become too great, which may lead to tearing or whitening when the film follows the mold.

[0019] The SSk(R) and SSk(M), SRa(R) and SRa(M), and the central surface area ratio SSr of the R-surface of the release film of the present invention can be adjusted to a desirable range by adjusting the resin component of the film and performing surface processing. For example, by adjusting the resin component of the film to make the release film flexible within an optimal range, and then performing embossing under conditions corresponding to the thermal properties of the resin component, it is possible to reduce the SSk on the side where the embossed shape is pressed while increasing the SSk on the opposite side. Furthermore, by controlling the transfer efficiency of the embossed shape by the flexibility of the film, it becomes possible to adjust SRa(R) and SRa(M), and the central surface area ratio SSr of the R-surface. Details will be described later. The release film of the present invention has a surface free energy of 40 mN / m or less on the R-side. Having a surface free energy of 40 mN / m or less on the R-side makes it possible to suppress resin chipping and wrinkles during molding. Furthermore, the surface free energy of the R-side of the release film of the present invention is more preferably 20 mN / m or more and 30 mN / m or less, even more preferably 21 mN / m or more and 28 mN / m or less, and particularly preferably 22 mN / m or more and 26 mN / m or less. If the surface free energy of the surface in contact with the molding resin is less than 20 mN / m, the affinity with the molding resin will be insufficient, which may reduce the fluidity of the molding resin during molding and cause resin chipping. Also, if the surface free energy of the surface in contact with the molding resin exceeds 40 mN / m, the release properties may be insufficient.

[0020] Further, it is preferable that the water contact angle on the R surface side of the release film of the present invention is 85° or more. When the water contact angle on the R surface side is 85° or more, it becomes possible to suppress resin chipping and appearance defects such as wrinkles during molding. Further, the water contact angle on the R surface side of the R surface of the release film of the present invention is more preferably 90° or more and 115° or less, still more preferably 95° or more and 110° or less, and particularly preferably 100° or more and 105° or less. When the water contact angle of the surface in contact with the mold resin exceeds 120°, the affinity with the mold resin is insufficient, the fluidity of the mold resin may decrease during molding, and resin chipping may occur. Further, when the water contact angle of the surface in contact with the mold resin is less than 85°, the release property may be insufficient.

[0021] A preferred embodiment of the release film of the present invention has a base material layer (hereinafter referred to as layer A). The base material layer in the present invention occupies 80% or more of the total thickness of the film when observing the cross section of the release film with a transmission electron microscope (TEM). Here, a layer refers to a portion having a distinguishable boundary surface with an adjacent portion in the thickness direction and having a finite thickness. More specifically, when observing the cross section of the release film with a transmission electron microscope (TEM), it refers to what is distinguished by the presence or absence of a discontinuous boundary surface. Even if the composition changes in the thickness direction of the film, if there is no aforementioned boundary surface between them, it is treated as one layer. Another preferred embodiment of the release film of the present invention consists of a base material layer (hereinafter referred to as layer A) and a release layer (hereinafter referred to as layer B). Further, the release layer in the present invention necessarily has an interface with the base material layer only on one side, and on the surface located on the opposite side of the base material layer, it refers to a resin layer having a surface free energy of 40 mN / m or less and / or a water contact angle of 85° or more measured by the method described later.

[0022] <Composition of layer A> The A layer of the present invention preferably has a polyester resin as a main constituent. Here, having a polyester resin as a main constituent means that the polyester resin is contained at 60% by mass or more with respect to the components constituting the film.

[0023] Polyester resin has a glass transition temperature suitable for compression molding, and its surface irregularities can be controlled by introducing copolymer and flexible components, as described later. Therefore, by using it as the main component of layer A in the present invention, it is possible to improve mold shape conformability and suppress wrinkle formation during processing.

[0024] Polyester resins can be obtained by 1) polycondensation of a dicarboxylic acid or its ester-forming derivative (hereinafter collectively referred to as "dicarboxylic acid component") and a diol component or its ester-forming derivative (hereinafter collectively referred to as "diol component"), 2) polycondensation of a compound having a carboxylic acid or carboxylic acid derivative and a hydroxyl group in one molecule, and combinations of 1) and 2).

[0025] 1) In this case, the dicarboxylic acid components include aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, dodecanedionic acid, dimer acid, eicosanedionic acid, pimelic acid, azelaic acid, methylmalonic acid, and ethylmalonic acid; alicyclic dicarboxylic acids such as adamantanedicarboxylic acid, norbornenedicarboxylic acid, cyclohexanedicarboxylic acid, and decalindicarboxylic acid; terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, and 1,5-naphtha. Examples of aromatic dicarboxylic acids include lendicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylsulfondicarboxylic acid, 5-sodium sulfisophthalic acid, phenylendanedicarboxylic acid, anthracenedicarboxylic acid, phenantradiocarboxylic acid, 9,9'-bis(4-carboxyphenyl)fluorenic acid, and their ester derivatives. These can be used individually or in combination.

[0026] Furthermore, dicarboxyl compounds can also be used, which are obtained by condensing l-lactide, d-lactide, hydroxybenzoic acid, and their derivatives, or a combination of multiple oxyacids, at least one carboxyl terminus of the aforementioned dicarboxylic acid component.

[0027] Next, typical examples of diol components include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol, and 1,3-butanediol; alicyclic diols such as cyclohexanedimethanol, spiroglycol, and isosorbide; and aromatic diols such as bisphenol A, 1,3-benzenedimethanol, 1,4-benzenedimethanol, and 9,9'-bis(4-hydroxyphenyl)fluorene. These can be used individually or in combination as needed. Dihydroxy compounds formed by condensing diols with at least one hydroxyl terminus of the above-mentioned diol components can also be used. On the other hand, in 2), examples of compounds having a carboxylic acid or carboxylic acid derivative and a hydroxyl group in one molecule include l-lactide, d-lactide, oxy acids such as hydroxybenzoic acid, their derivatives, oligomers of oxy acids, and compounds in which an oxy acid is condensed on one carboxyl group of a dicarboxylic acid.

[0028] Examples of polyester resins include polyethylene terephthalate, polyethylene-2,6-naphthalate, polypropylene terephthalate, polybutylene terephthalate, homopolymers such as polylactic acid, and copolymers thereof. The polyester resin constituting the polyester film of the present invention may be selected from the above homopolymers and copolymers, or homopolymers may be blended together or homopolymers and copolymers may be used.

[0029] Here, as homopolymers of polyester resin, polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, and polylactic acid are preferred from the viewpoint of film-forming properties. Among these, polyethylene terephthalate and polyethylene-2,6-naphthalate are more preferred due to their ease of processing, and polyethylene terephthalate is particularly preferred due to its superior film-forming properties.

[0030] Furthermore, a copolymer of polyester resin refers to a polymer in which less than 50 mol% of the total polyester resin consists of either or both different dicarboxylic acid components and diol components. When considering blending with a homopolymer, it is preferable to use a copolymer in which the same molecular structure as the target homopolymer constitutes 50 mol% or more of the total.

[0031] Here, as the copolymer of polyester resin, from the viewpoint of excellent polymerization suitability, thermal stability, and compatibility with homopolymers, alicyclic dicarboxylic acids, isophthalic acid, and naphthalenedicarboxylic acid are preferably used as the dicarboxylic acid component, and butanediol, ethylene glycol, spiroglycol, and cyclohexanedimethanol are preferably used as the diol component. These may be used individually or in combination as needed.

[0032] In the polyester resin constituting the release film of the present invention, the isophthalic acid residue is preferably 0.5 mol% or more and 10 mol% or less relative to the carboxylic acid component, more preferably 1.0 mol% or more and 7.0 mol% or less, and even more preferably 1.5 mol% or more and 3.0 mol% or less.

[0033] Furthermore, the cyclohexanedimethanol residue or butylene glycol residue is preferably 0.5 mol% or more and 20 mol% or less relative to the diol component, more preferably 5.0 mol% or more and 17 mol% or less, and even more preferably 8.0 mol% or more and 15 mol% or less.

[0034] If the content of each copolymer component is less than the above range, it may be difficult to form surface irregularities by the surface treatment described later, and the mold shape followability of the release film may also decrease. Further, if the content of each copolymer component exceeds the above range and is excessively contained, the heat resistance of the polyester film may decrease, and there is a possibility that the film may fuse or break at the mold edge. Also, if the film becomes excessively flexible, the irregularities formed during the surface treatment may disappear, and it may become difficult to form irregularities instead.

[0035] In the polyester resin constituting the release film of the present invention, it is preferable to contain a polyalkylene glycol component as a softening component for the purpose of further improving the mold shape followability. Examples of the polyalkylene glycol component include polyethylene glycol, polypropylene glycol, and polybutylene glycol. Since it can be obtained by melt-kneading with polyester, polyethylene glycol having a high melting point is more preferable. Further, the content of the polyalkyl ether component is preferably 0.01% by mass or more and 3% by mass or less, more preferably 0.3% by mass or more and 2.0% by mass or less, and still more preferably 0.5% by mass or more and 1.0% by mass or less. If it is less than the above range, the expected effect of improving the mold shape followability or the formation of surface irregularities by the surface treatment described later may be difficult. Also, if the amount of the soft component exceeds the above range and is excessively contained, the thermally decomposed oligomers may adhere to the mold resin or the mold and cause wrinkles. If the film becomes excessively flexible, the irregularities formed during the surface treatment may disappear, and it may become difficult to form irregularities instead.

[0036] In addition, the residue amount of the above copolymer component and the amount of the added component can be analyzed by proton nuclear magnetic resonance spectroscopy ( 1 1H-NMR) or carbon nuclear magnetic resonance spectroscopy ( 13 13C-NMR) after solvent extraction of the release film.

[0037] <Configuration and manufacturing method of layer A> The A layer of the release film of the present invention is not particularly limited, but a laminated film of two or more layers is preferred. In that case, it is preferable to have a main layer (hereinafter referred to as A1 layer) and a sub-layer (hereinafter referred to as A2 layer) that account for 60 volume or more of the total A layer. If a three-layer structure is used, it is more preferable to have the same composition for both surface layers in order to suppress deformation such as curling during post-processing, and it is even more preferable to have the same laminate thickness for both surface layers. For example, by laminating an A2 layer, which has a reduced amount of the copolymer and softening components, onto an A1 layer containing a large amount of the copolymer and softening components, it is possible to suppress the inhibition of surface irregularity formation caused by excessive softening of the film while maintaining excellent mold shape conformability.

[0038] The A layer of the release film of the present invention is preferably a biaxially oriented film from the viewpoint of creating a bias in surface irregularities due to surface processing. When surface processing is performed on an unstretched sheet, for example, when the irregularities are transferred by embossing, the transfer efficiency may become too high and bias may not occur. A biaxially oriented film can be obtained by stretching an unstretched film by a sequential biaxial stretching method in which the film is stretched in the longitudinal direction and then in the width direction, or by stretching it in the width direction and then in the longitudinal direction, or by a simultaneous biaxial stretching method in which the film is stretched in the longitudinal and width directions almost simultaneously.

[0039] In this stretching method, the stretching ratio is preferably 2.7 to 3.6 times in the longitudinal direction, and more preferably 3.0 to 3.4 times. The stretching temperature in the longitudinal direction is preferably 70°C to 90°C. The stretching ratio in the width direction is preferably 3.0 to 5.0 times, and more preferably 3.2 to 4.0 times.

[0040] Furthermore, the film is heat-treated after biaxial stretching. The heat treatment can be carried out by any conventionally known method, such as in an oven. Preferably, this heat treatment is performed in a temperature atmosphere of -40°C to -5°C above the crystal melting peak temperature (Tm) of the film. If the heat treatment temperature is lower than Tm-40°C, the degree of molecular orientation becomes too high, which may result in insufficient conformability to the mold shape, or large shrinkage during heating may cause wrinkles to form inside the mold and transfer to the package surface. Also, if the heat treatment temperature is higher than Tm-5°C, crystallization may proceed excessively, resulting in insufficient conformability to the mold shape. More preferably, the temperature is between Tm-34°C and -8°C, and most preferably between Tm-32°C and -12°C. The heat treatment time can be any amount within a range that does not degrade the properties, preferably between 5 seconds and 60 seconds, more preferably between 7 seconds and 40 seconds, and most preferably between 10 seconds and 25 seconds.

[0041] By using the above-mentioned A layer in the release film of the present invention, it becomes possible to transfer the unevenness while retaining the rigidity of the film during surface processing, thereby creating an unevenness in the surface unevenness.

[0042] <Embossing> The release film of the present invention can have surface irregularities formed by surface processing after the film that will become layer A is formed by the method described above. The surface processing method is not particularly limited as long as the surface shape of the release film described later is satisfied, but from the viewpoint that layer A used in the present invention is flexible, and from the viewpoint that it is difficult to create a surface with a large SSK with surface processing such as particle addition or sandblasting, the transfer of the irregular shape by embossing is preferred. Furthermore, embossing is a preferred method because it can form a surface with a large SSK and a surface with a small SSK in a single process.

[0043] Regarding the embossing method, a method of pressing and transferring an embossed shape onto one side of a film is preferred. Examples include a method of extruding heated and molten resin from a T-die onto a pair of pressure rolls, one of which consists of a roll with an embossed pattern and the other of which consists of a roll with an elastic material on its surface, to form a film with an embossed pattern; a method of applying pressure to the film between a hot press plate and an embossing die to impart an embossed pattern to the film; and a method of passing the film through a pair of heated and pressurized rolls, one of which consists of a roll with an embossed pattern and the other of a heated roll, while heating and pressurizing the film. In particular, in the present invention, from the viewpoint of creating unevenness in the surface irregularities, it is preferred to preheat a biaxially oriented film, then heat the roll with the embossed pattern itself, and then convey and pressurize it between the other touch roll. As for the embossed pattern, any shape such as sand, stone, cloth, wood, silk, pearlescent, leather, or hairline can be arbitrarily selected.

[0044] The surface temperature during embossing is preferably between 140°C and 240°C, more preferably between 160°C and 230°C, and even more preferably between 180°C and 220°C. If the processing temperature is lower than the above range, the surface irregularities will be smaller, and the expected effect may not be obtained. If the processing temperature is higher than the above range, the A layer may become excessively flexible, causing the formed irregularities to disappear, or it may fuse to the embossing roll, making processing difficult.

[0045] In other words, according to the present invention, by pressing an embossed shape onto layer A, the pressed surface can be given a shape in which the remaining flat portion and the concave portion of the unevenness are largely distributed due to the rigidity of the film. Furthermore, due to the flexibility of layer A, it is possible to give the opposite surface to the pressed embossed shape a shape in which the convex portion of the unevenness is largely distributed, all in a single surface processing step.

[0046] <Composition of the release layer (layer B)> The B layer of the present invention is preferable because it contains a binder resin, which improves adhesion with the A layer and allows for adjustment of the peeling force with respect to the object to be peeled off. Specific examples of binder resins include polyester resin, polystyrene resin, acrylic resin, urethane resin, polyvinyl, polyalkylene glycol, polyalkyleneimine, cellulose, starches, etc., but acrylic resin is preferably used from the viewpoint of mold shape conformability and peeling force control.

[0047] Examples of the above-mentioned acrylic resins include homopolymers or copolymers of alkyl (meth)acrylate esters, and (meth)acrylate ester copolymers having curable functional groups in the side chains and / or main chain ends. Examples of curable functional groups include hydroxyl groups, carboxyl groups, epoxy groups, and amino groups. Among these, acrylic monomer copolymers obtained by copolymerizing an acrylic monomer with an acrylic ester having curable functional groups in the side chains and / or main chain ends are preferred.

[0048] Furthermore, it is preferable to add a crosslinking agent as a component of layer B. By using various crosslinking agents in combination with the aforementioned resin, the heat resistance can be dramatically improved. Preferred crosslinking agents are oxazoline resin, melamine resin, epoxy resin, carbodiimide resin, and isocyanate resin. From the viewpoint of the durability of layer B to solvents, melamine resin is even more preferably used. The crosslinking agent can be mixed and used in any ratio, but it is preferable to add 5 to 50 parts by mass of the crosslinking agent per 100 parts by mass of the binder resin, and more preferably 10 to 40 parts by mass, in order to improve heat resistance. If the amount of crosslinking agent added is less than 5 parts by mass, the effect of improving heat resistance will be insufficient, and scratches may occur during roll transport. Also, if it exceeds 50 parts by mass, it is undesirable because unevenness is likely to occur during coating.

[0049] In the present invention, it is preferable that the resin composition forming layer B contains an additive suitable for imparting release properties, in addition to the binder resin and crosslinking agent. The additive is preferably in an amount of 3 parts by mass or more and 50 parts by mass or less, when the sum of the masses of the binder resin and the crosslinking agent is 100 parts by mass. By adding 3 parts by mass or more of the additive, release properties can be imparted, and by adding 50 parts by mass or less, sufficient heat resistance can be imparted. Preferably, it is 10 parts by mass or more and 42 parts by mass or less, and most preferably 20 parts by mass or more and 34 parts by mass or less.

[0050] In this invention, the term "additive" refers to a compound that, when added to a resin, has release properties on the surface of the resin. Specifically, examples include silicone-containing compounds, fluorine compounds, waxes such as paraffin wax, polyethylene wax, and carnauba wax, long-chain alkyl group-containing compounds, and resins. Among these, long-chain alkyl group-containing compounds are preferred from the viewpoint of suppressing mold release and appearance defects. In this invention, the term "long-chain alkyl compound" refers to a compound having a long-chain alkyl group, and is not particularly limited as long as it contains a long-chain alkyl group, but examples include those having a long-chain alkyl group in the side chain of the main chain polymer.

[0051] In compounds having a long-chain alkyl group in the side chain of the main chain polymer, examples of main chain polymers include acrylate-based polymers or copolymers, polyvinyl alcohol (including partially saponified polyvinyl acetate), ethylene-vinyl alcohol copolymer (including partially saponified ethylene-vinyl acetate copolymer), vinyl alcohol-acrylic acid copolymer (including partially saponified vinyl acetate-acrylic acid copolymer), polyethylimine, polyvinylamine, styrene-maleic anhydride copolymer, and polyurethane.

[0052] The resin constituting the B layer of the present invention may contain inert particles for the purpose of improving the adhesion and slipperiness of the release layer. Specific examples of the inert particles include silica, alumina, kaolin, calcium carbonate, titanium oxide, organic particles, and the like. Further, within a range not impairing the effects of the present invention, an antifoaming agent, a coating property improver, a thickener, an organic lubricant, an antistatic agent, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, etc. may be contained as necessary.

[0053] <Method for forming the B layer> A preferred embodiment of the release film of the present invention is characterized in that a B layer is provided on one side or both sides of the A layer. Although not particularly limited, it is preferable to provide the B layer after performing the embossing on the A layer, because the shape can be retained in the cured B layer. When embossing is performed after providing the B layer, there is a case where the B layer cannot follow the surface unevenness, and the A layer is partially exposed, resulting in a decrease in the release property.

[0054] When the B layer is provided only on one side of the A layer, it is preferable in that the manufacturing process of the B layer can be shortened. In that case, by providing the B layer on the surface pressed with the shape by embossing and arranging it on the surface in contact with the resin during molding, it is possible to improve the appearance defect during molding while maintaining excellent release property. When the B layer is provided on both sides of the A layer, it is preferable in that the release property is also imparted to the mold side, and it is possible to avoid adhesion to the mold by the deposited oligomers or the like.

[0055] As a method for providing the B layer on the A layer, a method of dissolving or dispersing the resin composition of the B layer in a solvent and applying it to the A layer, drying the solvent and applying heat after application, a method of melt coextruding the resin composition of the B layer together with the A layer and sheet-forming it together with the A layer by the above method, a method of extruding the molten resin composition of the B layer onto the A layer subjected to processing such as corona treatment to provide a resin layer, and a method of laminating the separately manufactured A layer and B layer can be mentioned. Among them, from the viewpoint that the above-mentioned preferred binder resin, additives, and crosslinking agents can be freely selected, the method of providing the B layer by coating is preferable.

[0056] A preferred method for applying layer B to layer A is to apply it uniformly using a metering bar or gravure roll, followed by drying in an oven. When applying using a coating method such as gravure coating, it is preferable to apply the coating in a way that does not hinder the flow and flattening (leveling) of the coated layer. The oven temperature is preferably 70 to 245°C, more preferably 80 to 235°C, and most preferably 90 to 225°C. If the drying temperature is lower than 70°C, the release layer may not harden sufficiently, and the release layer may not adhere properly to the substrate film. Also, if the temperature is higher than 245°C, the accuracy of the coating thickness may decrease due to thermal deformation of the film. The heat treatment time is preferably 1 to 60 seconds, more preferably 5 to 40 seconds, and most preferably 10 to 30 seconds.

[0057] In the release film of the present invention, layer B can be provided by in-line coating in order to ensure stable release properties. Specifically, in the manufacturing process of layer A, it is preferable to uniformly apply a solution or dispersion of the resin composition of layer B onto a film that has been at least uniaxially stretched using a metering ring bar or gravure roll, and then dry the coating while stretching the film. By performing the above method, the thickness of layer B can be made more uniform. Furthermore, by increasing the molecular affinity with layer A, the adhesion between layer A and layer B can be improved, and the degree of hardening of the coating film is increased by heat treatment at a higher temperature compared to off-line coating, improving heat resistance and chemical resistance, while at the same time eliminating or shortening the aging treatment after manufacturing.

[0058] In the release film of the present invention, the thickness of layer B after drying is preferably 50 nm to 500 nm, more preferably 100 nm to 400 nm, and even more preferably 200 nm to 300 nm. If the thickness of layer B is less than 50 nm, the release properties may be insufficient, and if the thickness of layer B exceeds 500 nm, the surface irregularities formed by embossing may disappear due to the coating film.

[0059] Furthermore, surface treatment may be performed in addition to the above, to the extent that it does not impair the effects of the present invention. For example, by providing a coating layer containing inert particles such as inorganic particles or organic particles on the opposite side of the embossed surface, the slipperiness with the mold can be further improved.

[0060] <Other structure and characteristics> The thickness of the release film of the present invention is preferably 25 μm or more and 75 μm or less, more preferably 28 μm or more and 50 μm or less, and even more preferably 30 μm or more and 40 μm or less. If the thickness is less than 25 μm, excessive transfer may occur during embossing, resulting in excessive unevenness of the surface irregularities. If the thickness exceeds 75 μm, the surface irregularities may not be transferred well to the opposite side of the embossed surface during embossing, potentially causing wrinkles. In addition, insufficient heat transfer from the mold may reduce the degree of hardening of the mold resin, leading to a decrease in release properties.

[0061] The release film of the present invention preferably has a Young's modulus of 50 MPa or more and 500 MPa or less, more preferably 75 MPa or more and 400 MPa or less, and even more preferably 100 MPa or more and 300 MPa or less at 125°C under air conditions. If the Young's modulus at 125°C is less than 50 MPa, the rigidity of the film is too low, and when it detaches from the embossed surface during embossing, elastic deformation may reduce the efficiency of surface irregularities formation. Also, if the Young's modulus at 125°C exceeds 500 MPa, surface irregularities may not be easily transferred to the opposite side of the embossed surface during embossing, and resin chipping may occur. Furthermore, insufficient flexibility may reduce the ability to follow the mold shape.

[0062] <Manufacturing method for semiconductor encapsulants> A method for manufacturing a semiconductor encapsulant using the release film of the present invention involves stacking the release film and a silicon wafer on which a semiconductor chip is placed in a molding apparatus, placing a measured amount of molding resin on the wafer, and then transporting the release film of the present invention from the top so that the R side faces the molding resin and the M side faces the mold, and applying vacuum suction, followed by compression pressing while heating the mold. At this time, since the release film of the present invention is located between the molding resin and the mold, a design that suppresses the occurrence of surface defects in both is required.

[0063] As described above, the release film of the present invention possesses excellent mold shape conformability and release properties, and its characteristic surface shape suppresses appearance defects such as resin chipping and wrinkles in the molded resin, which are problems during compression molding. Since these can cause concerns about the insulation properties of semiconductor chips and induce cracks during dicing, the release film of the present invention is suitable as a release film for circuit manufacturing processes and semiconductor manufacturing processes, and is particularly suitable for use as a release film for semiconductor encapsulation processes.

[0064] [Methods for measuring and evaluating characteristics] (1) Composition of polyester Dissolve the polyester resin and film in hexafluoroisopropanol (HFIP), 1 H-NMR and 13 The content of each monomer residue and polyalkylene glycol can be quantified using 1C-NMR. In the case of laminated films, the components constituting each layer can be collected and evaluated by scraping off each layer of the film according to the laminate thickness. For the film of the present invention, the composition was calculated from the mixing ratio during film manufacturing.

[0065] (2) Film thickness, layer thickness The film was embedded in epoxy resin, and a cross-section of the film was cut using a microtome. The cross-section was observed at 5000x magnification using a transmission electron microscope (Hitachi TEM H7100) to determine the film thickness and the thickness of the polyester layer.

[0066] (3) Crystal melting peak temperature (melting point Tm) Measurements and analyses were performed using a differential scanning calorimeter (Rigaku Thermo plus EVO2 DSCvesta) in accordance with JIS K7121-1987 and JIS K7122-1987. A 5 mg polyester film sample was used, and the melting point was defined as the temperature at the peak of the endothermic peak obtained from the DSC curve when the film was heated from 25°C to 300°C at a rate of 20°C / min. If multiple endothermic peaks were present, the peak temperature of the highest-temperature endothermic peak was used as the melting point. (4) Skewness SSK, mean center surface roughness SRa, center surface area ratio SSR The surface morphology of the release film was measured using a 3D micro-morphometer (model ET-4000A, manufactured by Kosaka Research Institute Co., Ltd.) under the following measurement conditions.

[0067] (Measurement conditions) • Measuring device: 3D micro-shape measuring instrument (model ET-4000A), manufactured by Kosaka Research Institute Co., Ltd. • Stylus: Model ET-1480 (tip radius 0.5 μmR, diameter 2 μm, made of diamond) ·Stylus pressure: 100μN • Measurement direction: Film width direction • X-axis (film width direction) measurement length: 1.0 mm • Y-axis (longitudinal direction of film) measurement length: 0.40 mm ·Measurement speed: 0.1mm / sec • X-axis feed pitch: 1 μm (measurement interval) • Y-axis feed pitch: 5 μm (measurement interval) • Number of Y-axis lines: 81 (number of measurement lines) • Z-axis measurement magnification: 10,000x (vertical magnification) • Evacuation amount: 2mm Next, the obtained measurement data was imported into a 3D surface roughness analysis system (model TDA-31), and the skewness SSk, mean center surface roughness SRa, and center surface area ratio SSr, which are 3D parameters in accordance with JIS-B0601 (1994) as defined in the manual included with the measuring instrument and analysis system, were calculated under the following analysis conditions. For the above measurements, measurements were taken with an arbitrary direction as the X-axis and another direction perpendicular to that direction as the X-axis, and the average of the two measurements was adopted.

[0068] (Analysis conditions) • Analysis equipment: 3D surface roughness analysis system (Model TDA-31) • Filtering method: Gaussian space type • Leveling: Yes, full range (tilt correction) • Low-frequency cutoff: 0.250mm • Low-frequency reserve length: λc × 0.5 • Recommended low-frequency cutoff range: 1 / 5 of the wavelength • High-frequency cutoff: 0mm • High frequency buffer length: None (5) Contact angle and surface free energy of water After leaving the release film in an atmosphere of 23°C and 65% relative humidity for 24 hours, the contact angles of four liquids—pure water, ethylene glycol, formamide, and diiodomethane—were measured at five points on a horizontally held measurement surface under the same atmosphere using a contact angle meter DM-501 (manufactured by Kyowa Interface Science Co., Ltd.). The average of these measurements was taken as the contact angle of each liquid.

[0069] Next, using the contact angles of the four types of liquids obtained, the dispersion force, polar force, and hydrogen bonding force were derived using the geometric mean method based on the "extended Fowkes equation," which is an extension of the Fowkes equation, by separating the surface free energy (γ) of a solid into three components: dispersion force component (γSd), polar force component (γSp), and hydrogen bonding force component (γSh), as proposed by Hata et al., and the surface free energy, which is the sum of these components, was calculated.

[0070] The specific calculation method is shown below. The meaning of each symbol is explained below.

[0071] γSL: Surface free energy of the resin layer and the known solution described in Table 1 γS: Surface free energy of the resin layer γL: Surface free energy of the known solution described in Table 1 γSd: Dispersion force component of the surface free energy of the resin layer γSp: Polar force component of the surface free energy of the resin layer γSh: Hydrogen bonding force component of the surface free energy of the resin layer γLd: Dispersion force component of the surface free energy of the known solution described in Table 1 γLp: Polar force component of the surface free energy of the known solution described in Table 1 γLh: Hydrogen bonding force component of the surface free energy of the known solution described in Table 1 Here, when γSL is the interfacial tension between the solid and the liquid, Equation (1) holds. γSL = γS + γL - 2(γSd·γLd) 1 / 2 - 2(γSp·γLp) 1 / 2 - 2(γSh·γLh) 1 / 2 ··· Equation (1) Also, the state when a smooth solid surface and a liquid droplet are in contact at a contact angle (θ) is expressed by the following equation (Young's equation).

[0072] γS = γSL + γLcosθ ··· Equation (2).

[0073] [[ID= (38]]Combining these Equation (1) and Equation (2), the following equation is obtained. (γSd·γLd) 1 / 2 +(γSp·γLp) 1 / 2 +(γSh·γLh) 1 / 2 = γL(1 + cosθ) / 2 ··· Equation (3).

[0074] In practice, the contact angle (θ) for four types of liquids—water, ethylene glycol, formamide, and diiodomethane—and the components of the surface tension of the known liquids listed in Table 1 (γLd, γLp, γLh) were substituted into equation (3), and the four simultaneous equations were solved. As a result, the surface free energy (γ), dispersion force component (γSd), polar force component (γSp), and hydrogen bonding force component (γSh) of the solid were calculated. (6) Young's modulus of the film at 125°C A rectangular section measuring 150 mm in length and 10 mm in width was cut from the film at an arbitrary position in the MD direction to create a sample. Tensile testing was performed on the film in the MD direction using a tensile testing machine (Orientec "Tensilon" (registered trademark) UCT-100) with an initial tensile chuck distance of 50 mm and a tensile speed of 300 mm / min. For measurement, the film sample was placed in a constant temperature chamber preheated to 125°C for 90 seconds, and then the tensile test was performed under air conditions. The measurement was performed with the principal orientation axis direction at an arbitrary position on the film as the TD direction, and the direction perpendicular to the TD direction as the MD direction. Sampling was performed at 5 points at arbitrary positions, and the average value obtained from each sample was adopted.

[0075] (7) Mold shape conformability The evaluation was conducted using a 150mm square, 5mm deep concave mold and a vacuum forming machine (Seiko Sangyo Co., Ltd.: machine name "300X"). After preheating a release film cut to A4 size with an infrared heater, it was vacuum-suctioned into the mold heated to 130°C and allowed to conform to the mold. After releasing the vacuum, the depth at the corners of the removed release film was measured, and the average value for the four corners was taken as the molding depth. Based on the obtained average molding depth and the reproducibility of the mold shape, the conformability to the mold was evaluated as follows. A: The average molding depth is 4.8 mm or more, and the corners on the bottom surface of the mold at the center of the mold recess are molded sharply. B: The average molding depth is 4.8 mm or more, and although the corners on the bottom side of the mold are rounded, the molding is successful. C: The average molding depth is 4.8 mm or more, but whitened areas and areas where the film could not follow the shape and tore can be visually confirmed. D: The average molding depth is less than 4.8 mm. If the result is C or lower, the mold temperature is increased to 150°C and the same evaluation is performed. If the result is equivalent to a C or higher, it is judged as C-. A grade of C or higher was considered a passing grade.

[0076] (8) Mold releasability Using a vacuum press, a 2mm thick mold resin (Nagase ChemteX Co., Ltd.: product name "R4507") was placed on the R-shaped surface of a release film and held at 125°C for 10 minutes while being pressurized under vacuum at a pressure of 2MPa. After leaving it in an atmosphere at room temperature (23°C) and relative humidity (65%) for 24 hours, the release force between the release film and the mold resin was measured (N=3) when a peel test was performed with a peel angle of 90° and a peel speed of 300mm / min, and evaluated according to the following criteria. A: 0.3N / less than 25mm B: 0.3N / 25mm or more and less than 0.5N / 25mm C: 0.5N / 25mm or more, less than 1.0N / 25mm D:1.0N / 25mm or more A grade of C or higher was considered a passing grade.

[0077] (9) Defects in appearance during compression molding Using a compression molding apparatus (Apic Yamada Co., Ltd.: apparatus name "WCM-300"), molding resin (Nagase ChemteX Co., Ltd.: product name "R4507"), measured with a dispenser, was dropped onto a 12-inch silicon dummy wafer to cover the dummy chip to a thickness of 1 mm, and placed on the lower mold of the molding die. Next, the R-shaped side of the release film was placed on the concave upper mold so that it was in contact with the molding resin, and then it was fixed by vacuum suction to prevent wrinkles, and the lower mold was raised to perform vacuum molding and obtain a compression molded sample. The mold temperature was 125°C, the mold pressure was 4 MPa, and the curing time was 10 minutes. Five molded samples were prepared using the method described above. After removing the release film from the molded resin, the samples were visually inspected for resin chipping at the edges and the presence or absence of surface wrinkles, and evaluated according to the following criteria. (Chipped resin) A: No resin chipping was observed in any of the samples. B: Resin chipping is observed in one sample. C: Resin chipping is observed in two or more samples. D: Resin chipping is observed in two or more samples, and in two or more locations on a single sample. A grade of C or higher was considered a passing grade. (Wrinkles) A: No wrinkles were observed in any of the samples. B: Wrinkles can be observed in a single sample. C: Wrinkles are observed in 2 to 3 samples. C-: Wrinkles were observed in 4 samples. D: Wrinkles are observed in all samples. A grade of C or higher was considered a passing grade. [Examples]

[0078] The present invention will be described below with reference to examples, but the present invention is not necessarily limited to these examples. Examples 6, 10, 17, 20, and 21 shall be interpreted as Reference Examples 6, 10, 17, 20, and 21.

[0079] 1. Manufacturing of polyester The polyester resin used to form layer A was prepared as follows.

[0080] (Polyester A) A polyethylene terephthalate resin (intrinsic viscosity 0.65, glass transition temperature 80°C) containing 100 mol% terephthalic acid as the dicarboxylic acid component and 100 mol% ethylene glycol as the glycol component.

[0081] (Polyester B) A cyclohexanedimethanol copolymer polyethylene terephthalate resin (intrinsic viscosity 0.75) in which 1,4-cyclohexanedimethanol is copolymerized with the glycol component at a concentration of 33 mol%.

[0082] (Polyester C) An isophthalic acid copolymer polyethylene terephthalate resin (intrinsic viscosity 0.7) in which the isophthalic acid component is copolymerized with the terephthalic acid component at a concentration of 17.5 mol%.

[0083] (Polyester D) A masterbatch containing polyethylene glycol 1000 (molecular weight 1000) at a concentration of 10% by mass in polyester A (intrinsic viscosity 0.62). (Polyester E) A masterbatch containing polybutylene terephthalate at a concentration of 33% by mass in polyester A (intrinsic viscosity 0.65).

[0084] (Polyester F) Isophthalic acid copolymerized polybutylene terephthalate resin (intrinsic viscosity 0.82, glass transition temperature 45°C) is obtained by copolymerizing isophthalic acid with a dicarboxylic acid component at a concentration of 10 mol%.

[0085] (Polyester b) A cyclohexanedimethanol copolymer polyethylene terephthalate resin (intrinsic viscosity 0.78) in which 1,4-cyclohexanedimethanol is copolymerized with the glycol component at a concentration of 66 mol%.

[0086] (Polyester c) Isophthalic acid copolymer polyethylene terephthalate resin (intrinsic viscosity 0.72) in which isophthalic acid is copolymerized with a dicarboxylic acid component at a concentration of 35 mol%.

[0087] (Polyester d) A masterbatch containing polyethylene glycol 1000 (molecular weight 1000) at a concentration of 30% by mass in polyester A (intrinsic viscosity 0.56).

[0088] (Particle Master) A masterbatch (intrinsic viscosity 0.65) containing aggregated silica particles with a number-average particle diameter of 2.2 μm at a particle concentration of 2% by mass in polyester A.

[0089] (Particle Master F) A masterbatch (intrinsic viscosity 0.75) containing aggregated silica particles with a number-average particle diameter of 2.2 μm in polyester F at a particle concentration of 2% by mass.

[0090] 2. Resins other than polyester (polystyrene) A polystyrene resin with a melting point of 270°C and a glass transition temperature of 100°C.

[0091] (Particle Master PS) A masterbatch containing aggregated silica particles with a number-average particle diameter of 2.2 μm at a particle concentration of 2% by mass in the above polystyrene resin.

[0092] (nylon) Nylon 6 resin with a melting point Tm of 228°C and a glass transition temperature of 50°C. (Particle Master Ny) A masterbatch containing aggregated silica particles with a number-average particle size of 2.2 μm at a particle concentration of 2% by mass in the nylon 6 resin described above.

[0093] 3. Manufacturing of release layer coating material The coating material used for layer B was prepared by mixing the following composition.

[0094] (Coating material B-1) The mixture contains 10 parts by mass of long-chain alkyl group-containing polyvinyl resin (Lion Specialty Chemicals Co., Ltd.'s "P-ROIL" (registered trademark) 1050) on a solids basis, 2.5 parts by mass of melamine-based crosslinking agent (Sumitomo Chemical Co., Ltd.'s "Sumimar" (registered trademark) M-55) on a solids basis, 1.5 parts by mass of p-toluenesulfonic acid (Teika Co., Ltd.'s "TAYCACURE" (registered trademark) AC-700) on a solids basis, 200 parts by mass of toluene, and 70 parts by mass of methyl ethyl ketone.

[0095] (Coating material B-2) 10 parts by mass of fluororesin (AGC Inc.'s "Lumiflon" (registered trademark) LF200MEK) on a solid content basis, 2.5 parts by mass of melamine-based crosslinking agent (Sumitomo Chemical Co., Ltd.'s "Sumimar" (registered trademark) M-55) on a solid content basis, 1.5 parts by mass of p-toluenesulfonic acid (Teika Co., Ltd.'s "TAYCACURE" (registered trademark) AC-700) on a solid content basis, 200 parts by mass of toluene, and 70 parts by mass of methyl ethyl ketone.

[0096] (Coating material B-3) The mixture consists of 10 parts by mass of long-chain alkyl group-containing polyvinyl resin (Lion Specialty Chemicals Co., Ltd.'s "P-ROIL" (registered trademark) 1050) on a solids basis, 2.5 parts by mass of melamine-based crosslinking agent (Sumitomo Chemical Co., Ltd.'s "Sumimar" (registered trademark) M-55) on a solids basis, 1.5 parts by mass of p-toluenesulfonic acid (Teika Co., Ltd.'s "TAYCACURE" (registered trademark) AC-700) on a solids basis, 15 parts by mass of melamine particles (Nippon Shokubai Co., Ltd.'s "Epostor" (registered trademark) M30) on a solids basis, 200 parts by mass of toluene, and 70 parts by mass of methyl ethyl ketone.

[0097] 4. Manufacturing of release film for compression molds (Example 1) Mixed raw materials according to the composition shown in Table 2 were supplied to separate twin-screw extruders with vents and an oxygen concentration of 0.2 volume%. The A1 layer was melted at a cylinder temperature of 270°C and the A2 layer at a cylinder temperature of 280°C. After the A1 and A2 layers merged, the short tube temperature was 270°C and the die temperature was 270°C, and the material was extruded in a sheet form onto a cooling drum with a temperature controlled to 25°C from the T-die. At this time, electrostatic discharge was applied using a wire electrode with a diameter of 0.1 mm to ensure close contact with the cooling drum, and an unstretched sheet was obtained. Next, before stretching in the longitudinal direction, the film temperature was increased with a heating roll, and the film was stretched 3.3 times in the longitudinal direction at a stretching temperature of 85°C, and immediately cooled with a metal roll with a temperature controlled to 40°C.

[0098] Next, the film was stretched 3.7 times in the width direction using a tenter-type transverse stretcher at a preheating temperature of 85°C and a stretching temperature of 95°C. It was then heat-treated at a constant length in a 225°C atmosphere for 12 seconds, followed by a 3% relaxation treatment at the same temperature, and then a further 2% relaxation treatment at 200°C to obtain a polyester film with a thickness of 35 μm.

[0099] Subsequently, the polyester film was preheated to a surface temperature of 150°C using a radiation heater, and then embossed by sandwiching it between an embossing roll (with a sand-like texture) and a metal roll, with the surface temperature raised to 210°C using an induction heating method.

[0100] Next, the film was cooled to room temperature, then coating material B-1 was applied to the embossed roll side using the gravure coating method. After that, the film was transported to a 110°C oven for pre-drying, and then heated and dried in a 160°C oven to obtain a release film with a B layer thickness of 250 nm.

[0101] The release film obtained above was evaluated with the B-layer coated surface as the surface in contact with the mold resin (the R-surface in this invention). As a result, as shown in Table 3, it was found to be a release film with excellent compression molding processability.

[0102] (Examples 2-12) A release film was obtained in the same manner as in Example 1, except that the film composition was changed as shown in Table 2. The evaluation results for each characteristic are shown in Table 3. In Example 12, film tearing was observed during film formation, and in Example 8, film tearing was observed during film formation and embossing, but in all cases, it was within an acceptable range.

[0103] (Examples 13-16) A release film was obtained in the same manner as in Example 1, except that the embossing conditions and the composition of the release layer were changed as shown in Table 4. The evaluation results for each characteristic are shown in Table 5. In Examples 14 and 15, film tearing was observed during embossing, but it was within an acceptable range.

[0104] (Comparative Example 1) A release film was obtained in the same manner as in Example 1, except that embossing was not performed. As shown in Table 5, the film properties of the obtained release film were such that the SSK of the side coated with layer B was greater than that of the opposite side which was not coated. When the side coated with layer B was evaluated as the side in contact with the mold resin (the R side in this invention), it was found to be inferior in terms of appearance. The surface free energy on the M side was 45 mN / m, and the water contact angle was 79°.

[0105] (Comparative Example 2) A release film was obtained in the same manner as in Example 1, except that sandblasting was performed instead of embossing, and layer B was applied to the sandblasted surface. When the obtained release film was evaluated with the surface coated with layer B as the surface in contact with the mold resin (R surface in this invention), it was found to be inferior in terms of appearance. The surface free energy on the M surface side was 45 mN / m, and the water contact angle was 79°.

[0106] (Comparative Example 3) A release film was obtained in the same manner as in Example 1, except that coating material B-3 was applied to one side without embossing. When the obtained release film was evaluated with the side coated with layer B as the surface in contact with the mold resin (the R surface in this invention), it was found to be inferior in terms of appearance. The surface free energy on the M surface side was 45 mN / m, and the water contact angle was 79°.

[0107] (Comparative Example 4) A release film was obtained in the same manner as in Example 1, except that coating material B-3 was applied to both sides of the film without embossing. When the obtained release film was evaluated with an arbitrarily selected surface as the surface in contact with the mold resin (the R surface in this invention), it was found to be inferior in terms of appearance. The surface free energy on the M surface side was 25 mN / m, and the water contact angle was 100°. Furthermore, the results were the same even when the R-surface and M-surface were reversed during the evaluation.

[0108] (Comparative Example 5) A release film was obtained in the same manner as in Example 1, except that a 35 μm thick cast sheet was used as layer A without biaxial orientation. When the obtained release film was evaluated with the surface coated with layer B as the surface in contact with the mold resin (R surface in this invention), it was found to be inferior in terms of appearance. The surface free energy on the M surface side was 46 mN / m, and the water contact angle was 76°.

[0109] (Example 17) A release film was obtained in the same manner as in Example 1, except that a polyester resin without copolymer components was used for layer A. The evaluation results of each property are shown in Table 7. The obtained release film had slightly inferior mold shape conformability, but it was within an acceptable range.

[0110] (Example 18) A release film was obtained in the same manner as in Example 1, except that a polyester film with a thickness of 35 μm was obtained by stretching the film 3.5 times in both the longitudinal and width directions using a tenter-type simultaneous biaxial stretcher at a preheating temperature of 85°C and a stretching temperature of 95°C, followed by heat treatment at a constant length in a 225°C atmosphere for 12 seconds. The evaluation results for each property are shown in Table 7.

[0111] (Example 19) Mixed raw materials according to the composition shown in Table 6 were supplied to separate twin-screw extruders with vents and an oxygen concentration of 0.2 volume%. The A1 layer was melted at 260°C in the extruder cylinder and the A2 layer at 260°C in the extruder cylinder. After the A1 and A2 layers merged, the short tube temperature was 260°C, the die temperature was 260°C, and the material was extruded in a sheet form onto a cooling drum with a temperature controlled to 25°C from the T-die. At this time, electrostatic discharge was applied using a wire electrode with a diameter of 0.1 mm to ensure close contact with the cooling drum, and an unstretched sheet was obtained. Next, a release film was obtained in the same manner as in Example 1, except that the material was stretched 3.5 times in both the longitudinal and width directions using a tenter-type simultaneous twin-screw stretcher at a preheating temperature of 75°C and a stretching temperature of 80°C, and then heat-treated at a constant length in a 200°C atmosphere for 12 seconds to obtain a polyester film with a thickness of 35 μm. The evaluation results of each characteristic are shown in Table 7.

[0112] (Example 20) Mixed raw materials according to the composition shown in Table 6 were supplied to separate twin-screw extruders with vents and an oxygen concentration of 0.2 volume%, and the A1 layer was melted at 300°C in the extruder cylinder and the A2 layer at 300°C in the extruder cylinder. After the A1 and A2 layers merged, the short tube temperature was 300°C and the die temperature was 300°C, and the material was extruded in a sheet form onto a cooling drum with a temperature controlled to 25°C from the T-die. At this time, electrostatic discharge was applied using a wire electrode with a diameter of 0.1 mm to ensure close contact with the cooling drum, and an unstretched sheet was obtained. Next, a release film was obtained in the same manner as in Example 1, except that the film was stretched 3.5 times in both the longitudinal and width directions using a tenter-type simultaneous twin-screw stretcher with a preheating temperature of 100°C and a stretching temperature of 120°C, and then heat-treated at a constant length in a 250°C atmosphere for 12 seconds to obtain a polystyrene film with a thickness of 35 μm. The evaluation results of each characteristic are shown in Table 7. The resulting release film exhibited slightly inferior mold shape conformability and molded appearance after processing, but it was within an acceptable range.

[0113] (Example 21) Mixed raw materials according to the composition shown in Table 6 were supplied to separate twin-screw extruders with vents and an oxygen concentration of 0.2 volume%. The A1 layer was melted at 260°C in the extruder cylinder and the A2 layer at 260°C in the extruder cylinder. After the A1 and A2 layers merged, the short tube temperature was 260°C, the die temperature was 260°C, and the material was extruded in a sheet form onto a cooling drum with a temperature controlled to 25°C from the T-die. At this time, electrostatic discharge was applied using a wire electrode with a diameter of 0.1 mm to ensure close contact with the cooling drum, and an unstretched sheet was obtained. Next, a release film was obtained in the same manner as in Example 1, except that the material was stretched 3.5 times in both the longitudinal and width directions using a tenter-type simultaneous twin-screw stretcher with a preheating temperature of 80°C and a stretching temperature of 90°C, and then heat-treated at a constant length in a 205°C atmosphere for 12 seconds to obtain a nylon film with a thickness of 35 μm. The evaluation results of each characteristic are shown in Table 7. The resulting release film exhibited slightly inferior mold shape conformability and molded appearance after processing, but it was within an acceptable range.

[0114] [Table 1]

[0115] [Table 2]

[0116] [Table 3]

[0117] [Table 4]

[0118] [Table 5]

[0119] [Table 6]

[0120] [Table 7] [Industrial applicability]

[0121] The release film of the present invention suppresses the occurrence of wrinkles and resin chipping during compression molding and provides a release film with excellent mold shape conformability and release properties. Furthermore, by suitably using such a release film as a release film for compression molding performed in the semiconductor encapsulation process, the mass production efficiency of semiconductor chips can be improved.

Claims

1. A release film for semiconductor compression molding, wherein the skewness SSk(R) of the surface roughness on one side (R side) and the skewness SSk(M) of the surface roughness on the opposite side (M side) are less than or equal to SSk(R) < SSk(M), the surface free energy on the R side is 40 mN / m or less, and the Young's modulus at 125°C in air is 50 MPa or more and 500 MPa or less.

2. A release film for semiconductor compression molding, wherein the skewness SSk(R) of the surface roughness on one side (R side) and the skewness SSk(M) of the surface roughness on the opposite side (M side) are less than SSk(R) < SSk(M), the water contact angle on the R side is 85° or more, and the Young's modulus at 125°C in air is 50 MPa or more and 500 MPa or less.

3. The release film for semiconductor compression molding according to claim 1 or 2, wherein SSk(R) and SSk(M) satisfy the condition SSk(R) < 0.1 < SSk(M).

4. The release film for semiconductor compression molding according to any one of claims 1 to 3, wherein the average center surface roughness SRa(R) (μm) of the R surface and the average center surface roughness SRa(M) (μm) of the M surface are 1.0 < SRa(M) < SRa(R).

5. The release film for semiconductor compression molding according to any one of claims 1 to 4, wherein the central surface area ratio of the R surface is 51% or more and 80% or less.

6. The release film for semiconductor compression molding according to any one of claims 1 to 5, wherein the surface free energy on the R-side is 20 mN / m or more and 30 mN / m or less.

7. A release film for semiconductor compression molding according to any one of claims 1 to 6, comprising at least a release layer and a base layer, wherein the base layer is mainly composed of polyester.

8. The release film for semiconductor compression molding according to claim 7, wherein the polyester of the base layer contains 0.5 mol% to 20 mol% of cyclohexanedimethanol residues or butylene glycol residues.

9. The release film for semiconductor compression molding according to claim 7 or 8, wherein the polyester of the base layer contains isophthalic acid residues in an amount of 0.5 mol% to 10 mol% of the acid component.

10. The release film for semiconductor compression molding according to any one of claims 7 to 9, wherein the base layer contains 0.01% by mass or more and 3% by mass or less of polyalkylene glycol.

11. The release film for semiconductor compression molding according to claim 10, wherein the polyalkylene glycol is polyethylene glycol.

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