TWI833987B - Release film and method of producing semiconductor package - Google Patents

Abstract

A release film that satisfies at least one of the following (1) or (2): (1) has a substrate layer, an adhesive layer and a conductive layer that is disposed between the substrate layer and the adhesive layer, and the substrate layer includes a polyester copolymer that includes a butylene structure and an alkylene oxide structure; or (2) has a degree of elongation at 150°C of 1000% or more.

Description

Release film and method for manufacturing semiconductor packaging

The invention relates to a release film and a method for manufacturing a semiconductor package.

In recent years, as electronic devices, especially mobile phones, have become thinner, semiconductor packages containing electronic components such as semiconductor elements have also been required to be further thinned. In addition, from the viewpoint of improving heat dissipation, instead of over molding (Over Molding) in which the entire electronic component is covered with sealing resin, exposure molding (Exposed Die Molding) in which a part of the surface of the electronic component is exposed is used. cases are also increasing.

When the electronic component is sealed so that a part of the electronic component is exposed, it is necessary to prevent the sealing material from leaking (flash burr) to the exposed portion of the electronic component. Therefore, a process is performed in which the exposed portion of the electronic component is sealed with a releasable film (release film) attached thereto, and then the release film is peeled off to expose the surface of the electronic component. As such a release film, for example, Patent Document 1 describes a laminated film in which a film containing a fluororesin is laminated on at least a single area of a base film containing a stretched polyester resin film.

[Prior art documents]

[Patent Document]

[Patent Document 1] Japanese Patent Application No. 2005-186740

As described above, the release film is peeled off from the surface of the electronic component after the sealing step. At this time, if the release film is charged, discharge will occur during peeling, which may cause electrostatic damage to electronic components.

Furthermore, in recent years, technology for mounting a plurality of packages on a substrate and sealing them together has been studied, and the use of a release film to expose terminals has been studied. In this case, since various packages exist on the substrate, the release film is required to have excellent extensibility (mold followability). In addition, depending on the type of package, it may not be heat-resistant, so it is required to show excellent elongation even at low temperatures (for example, 150° C. or lower).

In view of the above-described circumstances, an aspect of the present invention aims to provide a release film that suppresses electrostatic destruction of electronic components and has excellent extensibility at low temperatures. Another aspect of the present invention aims to provide a method of manufacturing a semiconductor package using the release film.

Means for solving the above problems include the following embodiments.

<1> A release film, including: a base material layer, an adhesive layer, and a conductive layer disposed between the base material layer and the adhesive layer, the base material layer containing butylene junction Polyester copolymer with alkylene oxide structure.

<2> A release film, including: a base material layer, an adhesive layer, and a conductive layer disposed between the base material layer and the adhesive layer; and the elongation rate at 150°C is 1000% or more.

<3> The release film according to <1> or <2> is used for manufacturing semiconductor packages by exposure molding.

<4> A method of manufacturing a semiconductor package, including sealing the release film in a state where the adhesive layer of any one of <1> to <3> is in contact with at least a part of the surface of the electronic component. a step around an electronic component; and a step of peeling off the release film from the electronic component.

According to one aspect of the present invention, it is possible to provide a release film that suppresses electrostatic destruction of electronic components and has excellent extensibility at low temperatures. According to another aspect of the present invention, a method for manufacturing a semiconductor package using the release film can be provided.

10:Substrate layer

20:Adhesive layer

30:Conductive layer

40: Release film

FIG. 1 is a diagram schematically showing the structure of a release film.

FIG. 2 is a diagram showing the shape of a test piece used for measuring the elongation and elastic coefficient of the release film.

Hereinafter, the form for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the structural elements (including element steps, etc.) are not essential unless otherwise expressly stated. Numerical values and their ranges are also the same and do not limit the present invention.

The term "step" in this specification includes not only steps that are independent of other steps, but also steps that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved.

The numerical range expressed by "~" in this manual includes the values stated before and after "~" as the minimum value and maximum value respectively.

Among the numerical ranges described in stages in this specification, the upper limit or lower limit described in one numerical range may be replaced by the upper limit or lower limit of the numerical range described in another stage. In addition, in the numerical range described in this specification, the upper limit value or the lower limit value of the said numerical range can be replaced with the value shown in an Example.

In this specification, the content rate or content of each component in the composition, when there are multiple substances corresponding to each component in the composition, refers to the multiple substances present in the composition unless otherwise specified. The total content rate or content.

In this specification, the particle size of each component in the composition, when there are multiple types of particles corresponding to each component in the composition, refers to a mixture of the multiple types of particles present in the composition unless otherwise specified. value.

The term "layer" in this specification includes not only the case where the layer is formed in the entire region but also the case where it is formed in only a part of the region when the region in which the layer exists is observed.

In this specification, the thickness of the release film or each layer constituting the release film can be measured by a known method. For example, it can be measured using a dial gauge or the like, or it can be measured based on a cross-sectional image of the release film. Alternatively, the material constituting the layer can be removed using a solvent, etc., and calculated based on the mass before and after removal, the density of the material, the area of the layer, etc. When the thickness of the layer is not constant, the arithmetic mean of the values measured at any five points is used as the thickness of the layer.

In this specification, "(meth)acrylic acid" refers to either or both acrylic acid and methacrylic acid, and "(meth)acrylate" refers to either or both acrylate and methacrylate.

<Release film>

The release film of the present disclosure is a release film that includes: a base material layer, an adhesive layer, and a conductive layer disposed between the base material layer and the adhesive layer, and satisfies the following (1) or ( At least one of 2).

(1) The base material layer contains a polyester copolymer containing a butylene structure and an alkylene oxide structure (hereinafter, also referred to as a polyester copolymer).

(2) The elongation at 150°C is more than 1000%.

According to the release film, electrostatic damage of electronic components can be suppressed. The reason for this is not necessarily clear, but it is thought to be that providing the conductive layer suppresses charging of the release film, making it less likely that discharge will occur when the release film is peeled off from the electronic component.

FIG. 1 schematically shows the structure of a release film. As shown in FIG. 1 , the release film 40 includes a base material layer 10 , an adhesive layer 20 , and a conductive layer 30 disposed between the base material layer 10 and the adhesive layer 20 .

As shown in Figure 1, in the release film of the present disclosure, the conductive layer 30 is not disposed on the surface of the release film 40, but is disposed between the base material layer 10 and the adhesive layer 20 (the adhesive layer 20 is disposed on the surface of the release film). surface). Therefore, the release film can be fully adhered to the surface of the electronic component via the adhesive layer, thereby effectively preventing the intrusion of the sealing material.

Furthermore, since the release film satisfies at least one of the above (1) or (2), it is excellent in elongation at low temperatures.

The release film disclosed in the present disclosure is peeled off after undergoing a sealing step and other treatments with the adhesive layer side attached to the surface of an adherend such as electronic components. The release film of the present disclosure is less likely to generate discharge when peeled off from the adherend. Therefore, it can be suitably used for manufacturing semiconductor packages by exposure molding, for example.

In this disclosure, the elongation (%) of the release film at 150° C. is measured as follows.

First, a test piece having a shape as shown in Figure 2 was produced using a release film. A tensile test was performed by holding both ends of the test piece using a testing machine. The measurement was performed at 150° C., and the stretching speed was set to 500 mm/min. The distance between marks A of the sample before the test (the length of the portion of the test piece with a width of 10 mm shown in Figure 2: 40 mm), and the distance between the marks when the sample is cut B (the width of the test piece before the test is 10 mm) (length of the part), use the following formula to calculate the elongation.

When measuring the elongation of the release film, for example, Orient "Tensilon tensile testing machine RTA-100 type" manufactured by Orientec Co., Ltd. or a similar testing machine equipped with a pinching tool and a 180-degree peeling device.

The elongation rate of the release film at 150°C is preferably 1200% or more, more preferably 1400% or more. The elongation of the release film at 150° C., for example, when the base material layer contains a polyester copolymer, can be adjusted based on the composition ratio of the butene structure and the alkylene oxide structure in the polyester copolymer.

The elastic coefficient of the release film at 150°C is preferably 10MPa~50MPa, more preferably 20MPa~40MPa. When the elastic modulus at 150° C. is 10 MPa or more, good mold followability tends to be obtained, and when it is 50 MPa or less, good extensibility tends to be obtained.

The elastic coefficient of the release film at 150° C., for example, when the base material layer contains a polyester copolymer, can be adjusted according to the composition ratio of the butene structure and the alkylene oxide structure in the polyester copolymer.

(Elastic coefficient at 150℃)

The elastic coefficient (MPa) of the release film at 150°C is calculated from the slope of the tangent line in the stress-strain diagram by stretching the test piece in the same manner as the measurement of the elongation at 150°C. It is calculated using the following equation from the force per unit cross-sectional area (mm ² ) (MPa) applied to the test piece, the distance between marks L0 (40 mm) before the test, and the distance between marks L.

[Formula 2]

(Substrate layer)

From the viewpoint of low-temperature extensibility, the base layer preferably contains a polyester copolymer containing a butene structure and an alkylene oxide structure.

The alkylene oxide structure contained in the polyester copolymer is a structure in which an alkylene group is bonded to an oxygen atom. The number of carbon atoms in the alkylene group is preferably 1 to 6, and more preferably 4.

The polyester copolymer can be synthesized, for example, by copolymerizing aromatic dicarboxylic acids such as terephthalic acid or derivatives thereof, 1,4-butanediol, and poly(alkylene oxide) glycol.

Preferred examples of the polyester copolymer include copolymers containing a structural unit represented by the following formula (1) and a structural unit represented by the following formula (2). This copolymer is an elastomer in which the structural units represented by the formula (1) constitute the hard segment (PBT) and the structural units represented by the formula (2) constitute the soft segment (PTMG).

The mass ratio (PBT:PTMG) of the hard segment (PBT) and the soft segment (PTMG) constituting the copolymer is not particularly limited. For example, it can be from 1:9~9:1 You can choose from the range of 2:8~8:2, or you can choose from the range of 3:7~7:3.

The base layer may contain components other than polyester copolymers. Examples include polyesters such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT), polyimide, polyamide, and polyester ethers. Polyamide imide, fluorine-containing resin, etc. When the base material layer contains components other than the polyester copolymer, the proportion of the polyester copolymer is preferably 50 mass% or more, more preferably 70 mass% or more, and still more preferably 80 mass% or more of the entire base material layer. .

The thickness of the base material layer is not particularly limited, but is preferably 10 μm to 300 μm, more preferably 20 μm to 100 μm. If the thickness of the base material layer is 10 μm or more, the release sheet will be less likely to be broken and will tend to have excellent workability. When the thickness of the base material layer is 300 μm or less, the mold followability is excellent, so the occurrence of appearance defects caused by wrinkles or the like in the molded semiconductor package tends to be suppressed.

The base material layer may include only one layer, or may include two or more layers. Examples of methods for obtaining a base material layer including two or more layers include a method of extruding materials for each layer using a co-extrusion method, a method of laminating two or more films, and the like.

If necessary, the surface of the base material layer on which the conductive layer is provided may be treated to improve the adhesion to the conductive layer. Examples of treatment methods include surface treatment such as corona treatment and plasma treatment, application of a primer (primer), and the like.

If necessary, a back surface treatment agent for adjusting the self-rolling properties of the release film may be provided on the back surface of the base material layer (the surface opposite to the side where the conductive layer is disposed). as Examples of the back surface treatment agent include silicone resin, fluorine-containing resin, polyvinyl alcohol, and resin having an alkyl group. If necessary, these backside treatment agents can be modified. Only one type of back surface treatment agent may be used, or two or more types may be used in combination.

(adhesive layer)

From the viewpoint of adhesion to the surface of the electronic component, the adhesive layer preferably contains an adhesive. The type of adhesive is not particularly limited, and can be selected taking into consideration adhesion, mold releasability, heat resistance, etc. Specifically, an acrylic adhesive, a silicone adhesive, and a urethane adhesive are preferred, and an acrylic adhesive is more preferred. The adhesive layer may contain only one type of adhesive, or two or more types of adhesives.

The acrylic adhesive is preferably a monomer with a low glass transition temperature (Tg) (for example, -20°C or less) such as butyl acrylate, ethyl acrylate, and 2-ethylhexyl acrylate as the main monomer, and ( Copolymer obtained by copolymerizing monomers with functional groups such as meth)acrylic acid, hydroxyethyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, (meth)acrylonitrile, etc. (Hereinafter also referred to as acrylic copolymer). The "glass transition temperature" is the glass transition temperature of a homopolymer obtained using the corresponding monomer.

The acrylic copolymer may be a cross-linked acrylic copolymer. The cross-linked acrylic copolymer can be synthesized by cross-linking monomers that are raw materials of the acrylic copolymer using a cross-linking agent. Examples of the crosslinking agent used in the synthesis of the crosslinked acrylic copolymer include known crosslinking agents such as isocyanate compounds, melamine compounds, and epoxy compounds. In addition, in order to form a slowly expanding network structure in the acrylic adhesive, the cross-linking agent is preferably a multi-functional cross-linking agent such as trifunctional or tetrafunctional.

The adhesive layer may contain anchoring enhancers, cross-linking accelerators, fillers, colorants, etc., if necessary. For example, when the adhesive layer contains a filler, the outer surface of the adhesive layer (the surface opposite to the conductive layer) is roughened, thereby improving the peelability from the electronic component.

The material of the filler is not particularly limited and can be organic substances such as resin, inorganic substances such as metals and metal oxides, or a combination of organic substances and inorganic substances. In addition, the filler contained in the adhesive layer may be only one type or two or more types. The volume average particle diameter of the filler is not particularly limited. For example, it can be selected from the range of 1μm~20μm. The volume average particle diameter of the filler in this specification is the particle diameter (D50) when the accumulation from the small diameter side reaches 50% in the volume-based particle size distribution measured by the laser diffraction method.

From the viewpoint of affinity with the adhesive contained in the adhesive layer, the filler is preferably resin particles. Examples of the resin constituting the resin particles include acrylic resin, olefin resin, styrene resin, acrylonitrile resin, silicone resin, and the like. From the viewpoint of suppressing residues on the surface of the semiconductor package after molding, an acrylic resin is preferred.

The thickness of the adhesive layer is not particularly limited, but is preferably 0.1 μm to 100 μm, more preferably 1 μm to 100 μm. If the thickness of the adhesive layer is 0.1 μm or more, sufficient adhesion to electronic parts can be obtained and the intrusion of the sealing material can be effectively suppressed. If the thickness of the adhesive layer is 100 μm or less, the distance between the surface of the adhesive layer and the conductive layer will not be too far, and the surface resistivity will be maintained low, thereby effectively suppressing electrostatic damage to electronic components. In addition, it is difficult to generate thermal shrinkage stress when the adhesive layer is thermally cured, and it is easy to maintain the flatness of the release film.

Taking into consideration the ease of formation of the adhesive layer (coatability, etc.), ensuring the adhesive force, ensuring the antistatic function, etc., the thickness of the adhesive layer is further preferably 3 μm to 50 μm.

(conductive layer)

The structure of the conductive layer is not particularly limited as long as it can improve the conductivity of the release film and suppress charging. For example, the layer may be a layer containing conductive materials such as antistatic agents, conductive polymer materials, and metals.

Examples of the antistatic agent contained in the conductive layer include quaternary ammonium salts, pyridinium salts, cationic antistatic agents having cationic groups such as primary to tertiary amine groups, sulfonate groups, and sulfate esters. Anionic antistatic agents with anionic bases such as salt base and phosphate ester base, amphoteric antistatic agents such as amino acid based and amino acid sulfate based, aminoalcohol based, glycerin based, polyethylene glycol based, etc. Nonionic-based nonionic antistatic agents, polymeric antistatic agents that have high molecular weight of these antistatic agents, etc. Antistatic agent can be a combination of main agent and auxiliary agent (hardener, etc.).

Examples of the conductive polymer material contained in the conductive layer include polymer compounds having polythiophene, polyaniline, polypyrrole, polyacetylene, etc. in their skeleton.

Examples of the metal include aluminum, copper, gold, chromium, tin, etc. From the viewpoint of accessibility, aluminum is preferred.

The method of forming the conductive layer is not particularly limited. Examples include a method of laminating a metal foil on one side of a film as a base layer, a method of applying a conductive layer material to one side of a film as a base layer by coating, vapor deposition, or the like.

The thickness of the conductive layer is not particularly limited as long as the antistatic effect of the release film is sufficiently obtained. For example, it can be in the range of 0.01μm~1μm.

<Manufacturing method of semiconductor package>

The manufacturing method of a semiconductor package of the present disclosure is a manufacturing method of a semiconductor package including the steps of sealing the periphery of the electronic component in a state where the adhesive layer of the release film is in contact with at least part of the surface of the electronic component; and The step of peeling off the release film from electronic parts.

As described above, the release film of the present disclosure is less likely to generate discharge when peeled off, and can suppress electrostatic damage to electronic components. Therefore, according to the method, a semiconductor package with excellent reliability can be manufactured.

Furthermore, the release film of this disclosure has excellent adhesion to electronic components. Therefore, it is difficult for the sealing material to invade the portion exposed after the release film is peeled off from the electronic component.

The types of electronic components used in the method are not particularly limited. Examples include semiconductor elements, capacitors, terminals, and the like.

The type of material (sealing material) used to seal the surroundings of the electronic component in the method is not particularly limited. Examples include resin compositions containing epoxy resin, acrylic resin, and the like.

[Example]

Hereinafter, the release film of this disclosure is demonstrated based on an Example. However, this disclosure is not limited to the following Examples.

<Example 1>

As the material of the base material layer, the mass ratio of the hard segment (PBT) with the structure represented by the general formula (1) and the soft segment (PTMG) with the structure represented by the general formula (2) is used. (PBT:PTMG) is a 3:7 polyester copolymer, and a substrate film with a thickness of 100 μm is made, and one side is corona treated.

Apply an antistatic agent diluted to 2.5% by mass with a solvent on the corona-treated surface of the base film, and heat it at 100°C for 1 minute to form a conductive layer (thickness: 0.3 μm). As a solvent, a mixture of water and isopropyl alcohol (mass ratio 1:1) was used.

As a material for the adhesive layer, mix an adhesive (100 parts by mass), a cross-linking agent (20 parts by mass), a mixed solvent (34 parts by mass) with a mass ratio of toluene:methyl ethyl ketone of 8:2, and a filler ( 5 parts by mass) to prepare a composition for forming an adhesive layer. The composition for forming an adhesive layer was applied on the conductive layer so that the thickness of the adhesive layer became 5 μm, and the adhesive layer was formed by heating at 100° C. for 1 minute to prepare a release film.

<Example 2>

A release film was produced in the same manner as in Example 1 except that the mass ratio (PBT:PTMG) of the hard segment (PBT) and the soft segment (PTMG) of the polyester copolymer was 5:5.

<Example 3>

A release film was produced in the same manner as in Example 1 except that the mass ratio (PBT:PTMG) of the hard segment (PBT) and the soft segment (PTMG) of the polyester copolymer was 7:3.

<Example 4>

A release film was produced in the same manner as in Example 1 except that the mass ratio (PBT:PTMG) of the hard segment (PBT) and the soft segment (PTMG) of the polyester copolymer was 8:2.

<Example 5>

A base film (thickness 100 μm) was produced by co-extrusion. The base film was composed of layer A containing polybutylene terephthalate, and layer A containing hard segments (PBT) and soft segments (PTMG). Layer B of a polyester copolymer with a mass ratio (PBT:PTMG) of 2:8 is laminated. The thickness ratio of layer A and layer B is set to 1:1.

A release film was produced in the same manner as in Example 1 except that the obtained base film was used.

<Comparative example 1>

A release film was produced in the same manner as in Example 1, except that a polybutylene terephthalate film with a thickness of 100 μm that was corona-treated on one side was used as a base film.

<Comparative example 2>

A release film was produced in the same manner as in Example 3 except that a conductive layer was not formed on the base film but an adhesive layer was formed.

Details of each material used for production of the release film are as follows.

Antistatic agent: a mixture of the following component A (100 parts by mass) and component B (25 parts by mass)

Component A: A cationic antistatic agent that is an acrylic copolymer with quaternary ammonium salt, trade name "bondeip PA-100 main agent", Konishi Co., Ltd.

Component B: Epoxy resin, trade name "bondeip PA-100 hardener", Konishi Co., Ltd.

Adhesive: Acrylic adhesive, trade name "FS-1208", Lion Essence Lion Specialty Chemicals Co., Ltd., various mixed monomers including methacrylate

Cross-linking agent: Polyisocyanate cross-linking agent (hexamethylene diisocyanate cross-linking agent (HMDI)), trade name "Duranate E405-80T", Asahi Kasei Chemical Co., Ltd.

Filler: Cross-linked acrylic particles, trade name "MX-500", Soken Chemical Co., Ltd., volume average particle size 5 μm

<Evaluation test>

The following evaluation test was performed using the produced release film.

(Elongation and elastic coefficient at 150℃)

By the above method, the elongation and elastic coefficient of the release film at 150°C were measured. "Tensilon tensile testing machine RTA-100 model" manufactured by Orientec Co., Ltd. was used during the measurement. The results are shown in Table 1.

(Mold followability and/or molded product appearance)

A release film is installed on the upper mold of a transfer mold with a depth of 3 mm, and the mold is closed after fixing it with vacuum, and transfer molding is performed using sealing material. The mold temperature was set to 150°C, the molding pressure was set to 6.86MPa (70kgf/cm ² ), and the molding time was set to 300 seconds.

Regarding the mold followability, if no cracks etc. occur and the release sheet can follow the mold, the evaluation is ○; if cracks etc. occur slightly but there is no practical problem, the evaluation is △; if cracks etc. occur, the evaluation is △ is ×.

Regarding the appearance of the molded product, when the release film has no wrinkles, flow marks, etc. and the appearance is good, the evaluation is ○; when the release film has slight wrinkles, flow marks, etc., but it is not practical In the case of a problem, the evaluation is Δ, and in the case where wrinkles, flow marks, etc. occur in the release film and a defective appearance occurs, the evaluation is ×.

(Electrostatic damage test of electronic parts)

Place the release film on the adhesive layer side of the circuit board on which the electronic component (semiconductor component) is mounted, and place it in an environment with a temperature of 23°C ± 2°C and a humidity of 60 ± 10% RH for 60 seconds. After that, take advantage of the opportunity to peel off the release film. The circuit board after repeating this operation five times was confirmed by V-I (voltage and current characteristics) measurement. When energization was obtained, the evaluation was "○", and when energization was not obtained, the evaluation was "×".

As shown in the results in Table 1, compared with the release film of Comparative Example 1 in which the base material layer did not contain a polyester copolymer and the elongation at 150° C. was less than 1000%, the base material layer contained a polyester copolymer, 150 The release films of the Examples with an elongation of 1000% or more at ℃ were excellent in elongation at low temperatures, and were also evaluated favorably in mold followability and molded product appearance.

Furthermore, the release film of the embodiment in which the conductive layer was formed between the base material layer and the adhesive layer did not cause electrostatic damage to the electronic component in the electrostatic damage test.

Claims (4)

A release film, including: a base material layer, an adhesive layer, and a conductive layer disposed between the base material layer and the adhesive layer. The base material layer includes a polyethylene containing a butylene structure and an alkylene oxide structure. ester copolymer, and the alkylene oxide structure does not include a proportion of less than 10 mol% in the polyester copolymer. The release film according to claim 1, including: a base material layer, an adhesive layer, and a conductive layer disposed between the base material layer and the adhesive layer; and the elongation rate at 150° C. is 1000% or more. . The release film according to claim 1 or claim 2 is used for manufacturing semiconductor packages by exposure molding. A method of manufacturing a semiconductor package, comprising: sealing the electronic component in a state where the adhesive layer of the release film according to any one of claims 1 to 2 is in contact with at least a part of the surface of the electronic component. surrounding steps; and a step of peeling off the release film from the electronic component.