JP2021061437A - Release sheet for semiconductor compression molding, and semiconductor package molded by use thereof - Google Patents

Abstract

To provide: a release sheet for semiconductor compression molding which can be released readily from a sealant without damaging a semiconductor package when molding a resin into the semiconductor package by compression molding, which is superior in uniformity of the surface appearance of a molded semiconductor package, and which enables the decrease in contamination to the surface of the molded semiconductor package from the release sheet; and a semiconductor package molded with the release sheet.SOLUTION: A release sheet for semiconductor compression molding comprises: a release layer including resin particles; and a base material layer. In the release layer, the resin particles account for 5-65 vol.%.SELECTED DRAWING: None

Description

The present invention relates to a release sheet for semiconductor compression molding and a semiconductor package molded using the same.

A semiconductor chip is usually sealed with a resin to shield and protect it from the outside air, and is mounted on a substrate as a molded product called a package. Conventionally, a molded product is molded as a package molded product for each chip connected via a runner which is a flow path of a sealing resin. In this case, the mold releasability of the molded product from the mold is obtained by the structure of the mold, the addition of a mold release agent to the sealing resin, and the like.
On the other hand, due to the demand for smaller packages and more pins, the number of packages such as Ball Grid Array (BGA) method, Quad Flat Non-readed (QFN) method, and Wafer Level Chip Size Package (WL-CSP) method has increased. ing. In the QFN method, in order to secure the standoff and prevent the occurrence of burr of the sealing material on the terminal part, and in the BGA method and the WL-CSP method, in order to improve the mold releasability of the package from the mold, the resin mold is released. Films are used (see, for example, Patent Document 1). The molding method using the release film in this way is called "film assist molding".

Japanese Unexamined Patent Publication No. 2002-158242

By using the above-mentioned release film, it is possible to easily release the sealing material of the semiconductor package and the mold when molding the semiconductor package with resin. However, the appearance of the molded package surface may be uneven and flow traces of the encapsulant may be seen, or the surface of the molded semiconductor package may be contaminated from the release film.
In addition, as the molding method is changed from the conventional transfer molding method to the compression molding method in the BGA method and the WL-CSP method, the size of one shot is increased, and the appearance of the molded package surface is uniform and sealed. The required level of material flow traces is increasing.

The present invention has been made in view of such circumstances, and when a semiconductor package is resin-molded by a compression molding method, the encapsulant and the mold can be easily released without damaging the semiconductor package. It is an object of the present invention to provide a mold release sheet for semiconductor compression molding, which is capable of reducing the contamination of the molded semiconductor package surface from the mold release sheet with excellent uniformity of the surface appearance of the molded semiconductor package. .. Another object of the present invention is to provide a semiconductor package molded by using the release sheet for semiconductor compression molding.

The present invention includes the following aspects in order to solve the above problems.
<1> A release layer containing resin particles and
Base layer and
Including
A release sheet for semiconductor compression molding in which the content of the resin particles in the release layer is 5% by volume to 65% by volume.
<2> The release sheet for semiconductor compression molding according to <1>, wherein the average particle size of the resin particles is 1 μm to 55 μm.
<3> The release for semiconductor compression molding according to <1> or <2>, wherein the resin particles contain at least one selected from the group consisting of acrylic resin, polyolefin resin, polystyrene resin, polyacrylonitrile resin, and silicone resin. Mold sheet.
<4> The release sheet for semiconductor compression molding according to any one of <1> to <3>, wherein the base material layer is a polyester film.
<5> A semiconductor package molded using the release sheet for semiconductor compression molding according to any one of <1> to <4>.

According to the present invention, when a semiconductor package is molded by compression molding, the encapsulant and the mold can be easily released without damaging the semiconductor package, and the surface appearance of the molded semiconductor package can be obtained. Provided is a release sheet for semiconductor compression molding, which has excellent uniformity and can reduce contamination from the release sheet on the surface of the molded semiconductor package. Further, according to the present invention, there is provided a semiconductor package that is molded using this release sheet for semiconductor compression molding.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.
The numerical range indicated by using "~" in the present specification indicates a range including the numerical values before and after "~" as the minimum value and the maximum value, respectively.
In the present specification, the amount of each component in the composition means the total amount of the plurality of substances present in the composition when a plurality of substances corresponding to each component are present in the composition, unless otherwise specified. To do.
In the present specification, the term "process" is included in this term not only as an independent process but also as long as the desired action of the process is achieved even if it cannot be clearly distinguished from other processes.
In the present specification, the “layer” and the “film” include not only the shape structure formed on the entire surface but also the shape structure formed on a part thereof when observed as a plan view.
As used herein, "(meth) acrylic" means at least one of "acrylic" and "methacryl", and "(meth) acrylate" means at least one of "acrylate" and "methacrylate".

In the present invention, the average thickness of a layer or film (also referred to as an average value of thickness) is a value given as an arithmetic mean value obtained by measuring the thickness of five points of a target layer or film.
The thickness of the layer or film can be measured using a micrometer or the like. In the present invention, when the thickness of the layer or the film can be directly measured, it is measured by using a micrometer. On the other hand, when measuring the thickness of one layer or the total thickness of a plurality of layers, it may be measured by observing the cross section of the release sheet using an electron microscope.

In the present invention, the "average particle size" is determined as the particle size (50% D) at which the accumulation from the small particle size side is 50% in the volume accumulation particle size distribution curve by the laser diffraction scattering type particle size distribution measurement method. For example, it can be measured using a particle size distribution measuring device using a laser light scattering method (for example, Shimadzu Corporation, "SALD-3000").

<Release sheet for semiconductor compression molding>
The release sheet for semiconductor compression molding of the present invention (hereinafter, also referred to as "release sheet of the present invention") includes a release layer containing resin particles and a base material layer, and the resin particles in the release layer. It is a release sheet for semiconductor compression molding which has a content of 5% by volume to 65% by volume.
More specifically, the release sheet of the present invention has a two-layer structure including a release layer in contact with the molded semiconductor package on one side of a base material layer in contact with the mold used in resin molding of the semiconductor package. Has.

By adopting the above configuration, the release sheet of the present invention can easily release the encapsulant and the mold without damaging the semiconductor package when the semiconductor package is molded by compression molding. Therefore, it is possible to improve the uniformity of the surface appearance of the molded semiconductor package and reduce the contamination of the molded semiconductor package surface from the release sheet.
The reason for this is not clear, but it can be inferred as follows.
When a conventional release sheet is used when molding a semiconductor package, the release sheet is sufficient for the shape of the molding mold from the viewpoint of suppressing the occurrence of shape defects such as wrinkles in the molded semiconductor package. It is required to have a matching followability. Further, since the semiconductor package is easily damaged if an excessive force is applied when the semiconductor package is taken out from the molding die, the release sheet is also required to have sufficient releasability with respect to the semiconductor package.
The release sheet of the present invention has two types having different functions: a release layer having excellent releasability to a sealing resin (for example, epoxy resin) for a semiconductor package and a base material layer having excellent releasability to a molding die. It is presumed that by having the above-mentioned layer, it is possible to improve the releasability from the molded semiconductor package while maintaining the followability to the molding die.
Further, in the release sheet of the present invention, since the release layer contains resin particles at a specific content, the outer surface (the surface facing the semiconductor package) of the release layer becomes rough, and the molded semiconductor package is formed. It is presumed that the rough surface reduces the flow traces of the encapsulant and improves the uniformity of the appearance of the package surface. In addition, the particle size, shape, and the like of the resin particles can be easily selected, and the degree of variation in the roughness of the outer surface of the release layer can be easily adjusted. Further, since the resin particles have excellent adhesion to other components contained in the release layer, it is presumed that they are hard to fall off from the release layer and can suppress contamination of the semiconductor package.

[Release layer containing resin particles]
The release sheet of the present invention contains a release layer containing resin particles (hereinafter, also referred to as "specific release layer"), and the content of the resin particles in the specific release layer is 5% by volume to 65% by volume. is there.

(Resin particles)
The resin particles in the present invention preferably contain at least one selected from the group consisting of acrylic resin, polyolefin resin, polystyrene resin, polyacrylonitrile resin and silicone resin. From the viewpoint of releasability to the semiconductor package, it is more preferable that the resin particles contain at least one selected from acrylic resin, polystyrene resin and polyacrylonitrile resin.
From the viewpoint of uniformity of package surface appearance, the resin particles are preferably insoluble or sparingly soluble in organic solvents (eg, toluene, methyl ethyl ketone, and ethyl acetate) that can be used in the preparation of the release layer forming composition. .. Here, the term "insoluble or sparingly soluble in an organic solvent" means a gel after resin particles are dispersed in an organic solvent such as toluene and held at 50 ° C. for 24 hours in a gel fraction test based on JIS K6769 (2013). It means that the fraction is 97% or more.

Examples of the acrylic resin include (co) polymers of (meth) acrylic monomers, and include (meth) acrylic acid resin, (meth) acrylic acid ester resin (for example, alkyl (meth) acrylate resin, and dimethylaminoethyl). (Meta) acrylate resin) and the like.
Examples of the (meth) acrylic monomer include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n- acrylate. Butyl, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, pentyl acrylate, pentyl methacrylate, acrylic acid Hexil, hexyl methacrylate, heptyl acrylate, heptyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, octyl acrylate, octyl methacrylate, nonyl acrylate, nonyl methacrylate, decyl acrylate, decyl methacrylate, Dodecyl Acrylic Acid, Dodecyl Methacrylate, Tetradecyl Methacrylate, Tetradecyl Methacrylate, Hexadecyl Acrylate, Hexadecyl Methacrylate, Octadecyl Acrylic Acid, Octadecyl Methacrylate, Eikosyl Acrylic Acid, Eikosyl Methacrylate, Dococil Acrylate, Dococil Methacrylate, Acrylic Acid Cyclopentyl, cyclopentyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, cycloheptyl acrylate, cycloheptyl methacrylate, benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate, Dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylate, dimethylaminopropyl methacrylate, 2-chloroethyl acrylate, 2-chloroethyl methacrylate, 2-chloroacrylate Fluoroethyl, 2-fluoroethyl methacrylate, styrene, α-methylstyrene, cyclohexylmaleimide, dicyclopentanyl acrylate, dicyclopentanyl methacrylate, vinyl toluene, vinyl chloride, vinyl acetate, N-vinylpyrrolidone, butadiene, Examples thereof include isoprene and chloroprene. These are used alone or in combination of two or more.
The polyolefin resin is not particularly limited as long as it is a (co) polymer of an olefin monomer or an alkene monomer. Specific examples thereof include polyethylene, polypropylene, polymethylpentene and the like.
Examples of polystyrene resins include (co) polymers of styrene or styrene derivatives. Examples of the styrene derivative include alkyl-substituted styrene having an alkyl chain such as α-methylstyrene, 4-methylstyrene, 2-methylstyrene, 3-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, and 4-ethylstyrene, and 2 Examples thereof include halogen-substituted styrenes such as −chlorostyrene, 3-chlorostyrene and 4-chlorostyrene, fluorine-substituted styrenes such as 4-fluorostyrene and 2,5-difluorostyrene, and vinylnaphthalene.
Examples of the polyacrylonitrile resin include (co) polymers of acrylonitrile monomers.
From the viewpoint of suppressing the solubility of the resin particles in the organic solvent, the resin contained in the resin particles is preferably a crosslinked resin.

The average particle size of the resin particles is preferably 1 μm to 55 μm. When the average particle size of the resin particles is 1 μm or more, it is possible to sufficiently form irregularities on the surface of the specific release layer, the uniformity of the surface appearance of the molded semiconductor package is improved, and the flow trace of the encapsulant is improved. Tends to be suppressed. Further, when the average particle size of the resin particles is 55 μm or less, it is not necessary to excessively increase the thickness of the specific release layer in order to fix the resin particles in the specific release layer, which is preferable from the viewpoint of cost.
The upper limit of the average particle size of the resin particles is preferably 55 μm, more preferably 50 μm, from the viewpoint of the appearance of the surface of the semiconductor package. The lower limit of the average particle size of the resin particles is more preferably 3 μm and further preferably 10 μm from the viewpoint of cost.

The shape of the resin particles contained in the specific release layer is not particularly limited, and may be spherical, elliptical, amorphous, or the like.

Specific examples of the resin particles include tough tic series such as tough tic FH-S010 (Toyobo Co., Ltd.) which is an acrylic resin particle.

The content of the resin particles contained in the specific release layer is 5% by volume to 65% by volume.
When the content is 5% by volume or more, it is possible to sufficiently form irregularities on the surface of the specific release layer, the uniformity of the surface appearance of the molded semiconductor package is improved, and the flow traces of the encapsulant are suppressed. There is a tendency to obtain a sufficient effect. From this viewpoint, the lower limit of the content of the resin particles is preferably 10% by volume, more preferably 20% by volume.
Further, when the content is 65% by volume or less, the resin particles are easily fixed by the resin component described later in the specific release layer, the possibility of the resin particles falling off is reduced, and the resin particles are attached to the surface of the molded semiconductor package. Contamination can be suppressed and it tends to be economically favorable. From this viewpoint, the upper limit of the content of the resin particles is preferably 60% by volume, more preferably 50% by volume.

The content of the resin particles can be calculated as the ratio of the resin particles per unit volume by observing the cross section of the specific release layer of the release sheet with a scanning electron microscope (SEM), for example. In detail, it can be calculated by the following method.
First, the cross section of the specific release layer is observed by SEM, and the number of resin particles and the particle size contained in an arbitrary area (hereinafter, also referred to as “specific area”) in this cross section are measured. Further, an arbitrary volume (hereinafter, also referred to as “specific volume”) is set based on the specific area, and the number of resin particles contained in the specific volume is calculated. Further, the volume per resin particle is calculated based on the particle size of the resin particles. Then, the total volume of the resin particles contained in the specific volume is calculated from the calculated number of resin particles and the volume per resin particle, and the layer volume of the resin particles is divided by the specific volume to specify the specific volume. The volume content of the resin particles contained in the release layer can be calculated.

As another method, the mass (Wc) of the specific release layer at 25 ° C. is measured, the specific release layer is dissolved in an organic solvent such as toluene, and the mass (Wf) of the remaining resin particles at 25 ° C. To measure. Next, the specific gravity (df) of the resin particles at 25 ° C. is determined using an electronic hydrometer or a specific gravity bottle. Then, the specific gravity (dc) of the specific release layer at 25 ° C. is measured by the same method. Next, the volume of the specific release layer (Vc) and the volume of the remaining resin particles (Vf) are obtained, and the volume of the remaining resin particles is divided by the volume of the specific release layer as shown in (Equation 1). , Obtained as the volume ratio (Vr) of the resin particles.
(Equation 1)
Vc = Wc / dc
Vf = Wf / df
Vr = Vf / Vc

Vc: Volume of release layer (cm ³ )
Wc: Mass of release layer (g)
dc: Specific gravity of release layer (g / cm ³ )
Vf: Volume of resin particles (cm ³ )
Wf: Mass of resin particles (g)
df: Specific gravity of resin particles (g / cm ³ )
Vr: Volume ratio of resin particles The specific release layer in this measurement method may be peeled from the release sheet or may be separately prepared for this measurement method.

(Resin component of specific release layer)
The specific release layer according to the present invention may further contain a resin component. By containing the resin component, the resin particles are fixed in the specific release layer.
The resin component of the specific release layer according to the present invention is not particularly limited. The resin component is preferably an acrylic resin or a silicone resin from the viewpoint of releasability from the semiconductor package, heat resistance, etc., and is a crosslinked acrylic resin (hereinafter, also referred to as “crosslinked acrylic copolymer”). Is more preferable.

The acrylic resin contains a low glass transition temperature (Tg) monomer such as butyl acrylate, ethyl acrylate, 2-ethylhexyl acrylate as the main monomer, and acrylic acid, methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, acrylamide, acrylonitrile and the like. It is preferably an acrylic copolymer obtained by copolymerizing with a functional group monomer. Further, the cross-linked acrylic copolymer can be produced by cross-linking the above-mentioned monomer with a cross-linking agent.
Examples of the cross-linking agent used in the production of the cross-linked acrylic copolymer include known cross-linking agents such as isocyanate compounds, melamine compounds, and epoxy compounds. Further, in order to form a network structure that gently spreads in the acrylic resin, the cross-linking agent is more preferably a polyfunctional cross-linking agent such as trifunctional or tetrafunctional.

Since the cross-linked acrylic copolymer produced by using the above-mentioned cross-linking agent has a gradually expanding network structure, it is specified when this cross-linked acrylic polymer is used as the resin component of the specific release layer. Since the stretchability of the release layer is improved and the stretchability of the base material layer is suppressed from being hindered, the followability of the release sheet to the mold at the time of compression molding can be improved.
From this viewpoint, the amount of the cross-linking agent used in the production of the cross-linked acrylic copolymer is preferably 3 parts by mass to 100 parts by mass with respect to 100 parts by mass of the acrylic copolymer, and is preferably 5 parts by mass to 5 parts by mass. More preferably, it is 70 parts by mass. When the amount of the cross-linking agent is 3 parts by mass or more, the strength of the resin component is secured and contamination can be prevented. When the amount is 100 parts by mass or less, the flexibility of the cross-linked acrylic copolymer is improved and the mold is released. The stretchability of the layer is improved.

(Other ingredients)
The specific release layer in the present invention may further contain a solvent, an anchoring improver, a cross-linking accelerator, an antistatic agent, a colorant and the like, if necessary, as long as the effects of the present invention are not impaired.

(Thickness of specific release layer)
The thickness of the specific release layer is not particularly limited, and is appropriately set in consideration of the relationship with the average particle size of the resin particles used. The thickness of the specific release layer is preferably 0.1 μm to 100 μm, and more preferably 1 μm to 50 μm.
If the thickness of the specific release layer is extremely thinner than the average particle size of the resin particles used, it becomes difficult to fix the resin particles in the specific release layer, the possibility of the resin particles falling off increases, and molding is performed. It may cause contamination of the surface of the semiconductor package. Further, when the thickness of the specific release layer is extremely thicker than the average particle size of the resin particles used, it becomes difficult to sufficiently form irregularities on the surface of the specific release layer, and the appearance of the molded semiconductor package surface becomes uniform. There is a possibility that the effect of improving the effect, the effect of suppressing the flow trace of the sealing material, and the like cannot be sufficiently obtained. It is also economically disadvantageous.
The thickness of the specific release layer in the present specification means a dry thickness, and the specific release layer of the release sheet can be measured by the above-mentioned method for measuring the thickness of the layer.

(Surface roughness of specific release layer)
The outer surface of the specific release layer (the surface opposite to the surface facing the base material layer) preferably has irregularities. The surface roughness of the specific release layer can be evaluated by the arithmetic average roughness (Ra) or the ten-point average roughness (Rz).
Arithmetic mean roughness (Ra) and ten-point average roughness (Rz) were determined by using, for example, a surface roughness measuring device (for example, Kosaka Laboratory Co., Ltd., model number SE-3500) with a stylus tip diameter of 2 μm. The value obtained by analyzing the result measured under the conditions of the feed speed of 0.5 mm / s and the scanning distance of 8 mm by JIS B0601 (2013) or ISO 4287 (1997) may be used. From the viewpoint of the uniformity of the package surface appearance, the arithmetic average roughness (Ra) of the specific release layer is preferably 0.5 μm to 5 μm, and the ten-point average roughness (Rz) is 5 μm to 50 μm. preferable.
By adjusting the average particle size of the resin particles and the thickness of the specific release layer, the surface roughness of the specific release layer can be adjusted within the above range.

[Base layer]
The release sheet of the present invention has a base material layer. The base material layer is not particularly limited, and can be appropriately selected from the resin-containing base material layers used in the art. From the viewpoint of improving the followability to the shape of the mold, it is preferable to use a resin-containing base material layer having excellent stretchability.
Considering that the base material layer of the present invention is formed at a high temperature (about 100 ° C. to 200 ° C.), it is desirable that the base material layer has heat resistance equal to or higher than this temperature. Further, in order to suppress the occurrence of wrinkles of the sealing resin, tearing of the release sheet, etc. when the release sheet is attached to the mold and when the resin during molding flows, the elastic modulus and elongation at high temperature are to be suppressed. It is important to make a selection in consideration of such factors.

The material of the base material is preferably a polyester resin from the viewpoint of heat resistance and elastic modulus at high temperature. Examples of the polyester resin include polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, and copolymers and modified resins thereof.
As the base material layer, a polyester resin molded into a sheet shape is preferable, the base material layer is more preferably a polyester film, and from the viewpoint of followability to a mold, it is a biaxially stretched polyester film. Is preferable.
The thickness of the base material layer is not particularly limited, and is preferably 5 μm to 100 μm, more preferably 10 μm to 70 μm. When the thickness is 5 μm or more, the handleability is excellent and wrinkles tend to be less likely to occur. When the thickness is 100 μm or less, the followability to the mold at the time of molding is excellent, so that the occurrence of wrinkles and the like of the molded semiconductor package tends to be suppressed.

[Other configurations]
The base material layer is a layer that comes into contact with the surface of the mold, and depending on the material used, a larger peeling force may be required to peel the release sheet from the mold. When a material that is difficult to peel off from the mold is used for the base material layer, it is preferable to make adjustments so that the release sheet can be easily peeled off from the mold. For example, the surface of the base material layer that is in contact with the specific mold release layer, that is, the surface of the base material layer on the mold side, may be subjected to surface processing such as satin finish in order to improve the mold releasability from the mold. Another release layer (second release layer) may be newly provided. The material of the second release layer is not particularly limited as long as it satisfies heat resistance, peelability from the mold, and the like, and the same material as the specific release layer may be used. The thickness of the second release layer is not particularly limited, but is preferably 0.1 μm to 100 μm.

Further, if necessary, an anchoring improving layer of the specific release layer or the second release layer, such as between the specific release layer and the base material layer, between the base material layer and the second release layer, etc. A layer such as an antistatic layer or a colored layer may be provided.

<Manufacturing method of release sheet of the present invention>
The release sheet of the present invention can be produced by a known method. For example, the release sheet of the present invention is produced by applying a release layer forming composition containing 5% by volume to 65% by volume of resin particles to the total solid content on one side of the base material layer and drying the composition. can do. The release layer forming composition may contain a resin component and other components added as desired.

[Preparation of composition for mold release layer formation]
The method for adjusting the composition for forming a release layer is not particularly limited, and examples thereof include a method of dispersing resin particles in a solvent, and a known composition adjusting method can be used.
The solvent used for preparing the release layer forming composition is not particularly limited, and an organic solvent capable of dispersing the resin particles and dissolving the resin component is preferable. Examples of the organic solvent include toluene, methyl ethyl ketone, ethyl acetate and the like.

[Giving and drying]
The method of applying the release layer forming composition to one side of the base material layer is not particularly limited, and known coating methods such as a roll coating method, a bar coating, and a kiss coating can be used. When the composition for forming a release layer is applied, the composition layer (release layer) after drying is applied so that the thickness is 0.1 μm to 100 μm.
The method for drying the applied release layer forming composition is not particularly limited, and a known drying method can be used. For example, a method of drying at 50 ° C. to 150 ° C. for 0.1 to 60 minutes may be used.

<Molding of semiconductor package>
The release sheet for compression molding of the present invention can be used for molding a semiconductor package, and can be particularly preferably used for compression molding.
Normally, in compression molding of a semiconductor package, a release sheet is placed in a mold of a compression molding apparatus, and the release sheet is made to follow the shape of the mold by vacuum suction or the like. After that, a sealing material (for example, epoxy resin) of the semiconductor package is put into a mold, a semiconductor chip is placed on the mold, and the sealing material is cured by compressing the mold while heating to cure the semiconductor package. To mold. After that, the mold is opened and the molded semiconductor package is taken out.

As described above, in compression molding, the release sheet is adsorbed on the mold, so that the release sheet is required to have excellent followability to the shape of the mold. In the release sheet of the present invention, the followability to the mold can be further improved by using a resin having excellent stretchability as the base material layer.

The release sheet for compression molding of the present invention is attached so that the specific release layer surface is in contact with the semiconductor package (molded product) when the semiconductor is molded by compression molding, so that the release sheet can be removed from the semiconductor package in the peeling process after molding. The release sheet can be easily peeled off, the encapsulant and the mold can be easily demolded without damaging the semiconductor package, and the molded package surface is excellently uniform in appearance. The flow traces of the material are also suppressed, and the contamination of the molded package surface from the film can also be suppressed.

Hereinafter, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to these examples.

<Example 1>
Acrylic resin (Imperial Chemical Industry Co., Ltd .: WS-023) 100 parts by mass, coronate L as a cross-linking agent (Nippon Polyurethane Industry Co., Ltd., trade name) 10 parts by mass, and tough tick as resin particles (C) 10 parts by mass of FH-S010 (Toyo Boseki Co., Ltd., trade name, acrylic particles, average particle diameter 10 μm) and 10 parts by mass were added to toluene to prepare a toluene solution having a solid content of 15% by mass, and a composition for forming a release layer was prepared. Prepared.
A biaxially stretched polyethylene terephthalate film (Unitika Ltd .: S-25) having a thickness of 25 μm as a base material layer was corona-treated. Then, a release layer forming composition was applied and dried on one side of the biaxially stretched polyethylene terephthalate film using a roll coater so that the average thickness after drying was 10 μm to form a release layer. A release sheet was obtained.
The content of the particles (C) in the release layer of the obtained release sheet was measured by cross-sectional observation by SEM and found to be 10% by volume.

[Characteristic evaluation of release sheet]
This release sheet is attached to the upper mold of a compression molding mold in which a semiconductor bare chip is set in the lower mold, fixed in a vacuum, then molded and sealed (Hitachi Kasei Co., Ltd .: Product name "CEL-". 9750ZHF10 ") was molded (compression molding) to obtain a semiconductor package. The mold temperature was 180 ° C., the molding pressure was 6.86 MPa (70 kgf / cm ² ), and the molding time was 180 seconds.
Releasability of the release sheet from the encapsulant after molding, uniformity of the appearance of the molded semiconductor package surface (presence or absence of flow traces of the encapsulant), and dropout of particles (C) on the molded semiconductor package surface. The presence or absence of (presence or absence of contamination) was evaluated by the following method. The evaluation results are shown in Tables 1 and 2.

(Evaluation of mold releasability with sealing material after molding)
As an index of the releasability of the mold release sheet after molding with the sealing material, the peeling force when the peeling test was performed at a peeling angle of 180 ° and a peeling speed of 300 mm / min was measured and evaluated according to the following criteria.
A: Less than 0.5N / 50mm B: 0.5N / 50mm or more and less than 5.0N / 50mm C: 5.0N / 50mm or more

(Evaluation of the appearance of the surface of the semiconductor package)
The presence or absence of flow traces of the encapsulant on the surface of the semiconductor package was observed visually and with an optical microscope (100 times), and evaluated according to the following criteria.
A: No flow trace is observed by either visual observation or microscopic observation.
B: No flow trace is visually observed, and slightly observed under a microscope.
C: Flow traces are observed by both visual observation and microscopic observation.

(Presence or absence of particles (C) falling off on the surface of the semiconductor package)
The presence or absence of particles (C) falling off on the surface of the semiconductor package was observed visually and with an optical microscope (100 times), and evaluated according to the following criteria.
A: No shedding of particles (C) is observed by either visual observation or microscopic observation.
B: No dropout of the particles (C) is visually observed, and slightly observed under a microscope.
C: Dropping of particles (C) is observed by both visual observation and microscopic observation.

<Examples 2 to 8 and Comparative Examples 1 to 4>
Example 2 in the same manner as in Example 1 except that the thickness of layer A after drying, the presence or absence of a release layer, and the type or content of particles (C) were changed as shown in Tables 1 and 2 below. Release sheets of No. 8 and Comparative Examples 1 to 4 were prepared and evaluated. The evaluation results are shown in Tables 1 and 2.

The particles (C) shown in Tables 1 and 2 are as follows.
・ Tuftic FH-S015 (Toyobo Co., Ltd., product name)
・ Tuftic FH-S020 (Toyobo Co., Ltd., product name)
・ Tuftic FH-S050 (Toyobo Co., Ltd., product name)
・ SX-500H (Soken Chemical Co., Ltd., product name)
・ Toughtic ASF-7 (Toyobo Co., Ltd., product name)
・ E606 (Toray Dow Corning Co., Ltd., product name)
・ BM30X-12 (Sekisui Plastics Co., Ltd., product name)
・ HPS-3500 (Toagosei Co., Ltd., product name)
In Tables 1 and 2, "PMMA" means polymethylmethacrylate, and "PMBA" means polybutylmethacrylate.

As shown in Tables 1 and 2, the release sheets of Examples 1 to 8 have good releasability from the sealing material after molding, and have excellent uniformity of the appearance of the molded package surface, and are molded. The release of particles (C) onto the surface of the package was also suppressed.
Although not shown in Tables 1 and 2, a release sheet was produced and evaluated in the same manner as in Example 1 except that the content of the particles (C) was set to 1% by volume. Flow traces were observed in all of the above, and the surface appearance was not sufficiently uniform.

On the other hand, in Comparative Example 1 in which there was no release layer, the sealing material and the release sheet could not be peeled off after molding. In Comparative Example 2 in which the release layer containing no resin particles was used, the appearance of the molded package surface was non-uniform, and flow traces of the encapsulant were observed. In Comparative Example 3 in which the release layer containing inorganic particles was used instead of the resin particles, the sealing material and the release sheet after molding could not be easily peeled off, and the silica particles in the release layer could not be easily peeled off. Dropouts were also observed. Furthermore, shedding of silica particles was observed by both visual observation and microscopic observation. In Comparative Example 4 in which the content of the resin particles exceeded 65% by volume, the resin particles were observed to fall off.

As shown above, when the release sheet of the present invention is used, when the semiconductor package is resin-molded, the encapsulant and the mold can be easily released without damaging the semiconductor package. Therefore, it is possible to provide a release film having excellent uniformity of the appearance of the surface of the molded package and suppressing contamination of the surface of the molded package from the film.

Claims (5)

A release layer containing resin particles and
Base layer and
Including
A release sheet for semiconductor compression molding in which the content of the resin particles in the release layer is 5% by volume to 65% by volume. The release sheet for semiconductor compression molding according to claim 1, wherein the average particle size of the resin particles is 1 μm to 55 μm. The release sheet for semiconductor compression molding according to claim 1 or 2, wherein the resin particles include at least one selected from the group consisting of acrylic resin, polyolefin resin, polystyrene resin, polyacrylonitrile resin, and silicone resin. The release sheet for semiconductor compression molding according to any one of claims 1 to 3, wherein the base material layer is a polyester film. A semiconductor package molded by using the release sheet for semiconductor compression molding according to any one of claims 1 to 4.