JP7739710B2 - Release film and method for manufacturing electronic component device - Google Patents

Description

This disclosure relates to a method for manufacturing a release film and a semiconductor package.

In recent years, as electronic devices, especially mobile phones, have become thinner, there has been a demand for even thinner electronic components such as semiconductor elements. Furthermore, from the perspective of improving heat dissipation, there has been an increasing trend toward exposed die molding, which exposes part of the surface of an electronic component, instead of overmolding, which covers the entire electronic component with encapsulating resin.

When sealing an electronic component so that a portion of the electronic component is exposed, it is necessary to prevent leakage of the sealing material onto the exposed portion of the electronic component (flash burrs).To this end, sealing is performed with a film having releasability (release film) attached to the exposed portion of the electronic component, 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 made of a fluororesin is laminated on at least one surface of a base film made of a stretched polyester resin film.

Japanese Patent Application Laid-Open No. 2006-49850

If the release film is made of a material that easily becomes charged, discharge may occur when the release film is brought into contact with electronic components or when the release film is peeled off from electronic components, resulting in electrostatic damage to the electronic components. In recent years, as the integration of semiconductor elements has become increasingly sophisticated, process nodes have become increasingly miniaturized, increasing the risk of electrostatic damage to electronic components.

In light of the above circumstances, one aspect of the present disclosure aims to provide a release film with excellent antistatic properties. Another aspect of the present disclosure aims to provide a method for manufacturing a semiconductor package using this release film.

The means for solving the above problems include the following embodiments.
<1> A release film having a base layer, a conductive layer, and a release layer in this order, the release layer containing polyacrylonitrile particles.
<2> The release film according to <1>, wherein the ratio (A/B) of the average particle size A of the polyacrylonitrile particles to the thickness B of the release layer is greater than 0.7.
<3> The release film according to <1> or <2>, wherein the content of the polyacrylonitrile particles is 10% by mass or more of the entire release layer.
<4> The release film according to any one of <1> to <3>, wherein the release layer contains a pressure-sensitive adhesive.
<5> The release film according to any one of <1> to <4>, for temporarily protecting at least a part of the surface of an object.
<6> The release film according to any one of <1> to <5>, which is for exposure molding.
<7> A method for manufacturing an electronic component device, comprising: a step of sealing the periphery of an electronic component in a state in which the release film according to any one of <1> to <6> is in contact with at least a part of the surface of the electronic component; and a step of peeling the release film from the electronic component.

According to one aspect of the present disclosure, a release film with excellent antistatic properties is provided. According to another aspect of the present disclosure, a method for manufacturing an electronic component device using this release film is provided.

FIG. 2 is a diagram schematically illustrating the configuration of a release film.

The following describes in detail the modes for implementing the present disclosure. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, and do not limit the present disclosure.

In this specification, the term "process" includes not only a process that is independent of other processes, but also a process that cannot be clearly distinguished from other processes as long as the purpose of the process is achieved.
In this specification, when a numerical range is indicated using "to", the numerical values before and after "to" are included as the minimum and maximum values, respectively.
In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.
In this specification, the content or amount of each component in a composition means, unless otherwise specified, the total content or amount of the multiple substances present in the composition when multiple substances corresponding to each component are present in the composition.
In this specification, the particle size of each component in a composition means the value for a mixture of the multiple types of particles present in the composition, unless otherwise specified, when multiple types of particles corresponding to each component are present in the composition.
In this specification, the term "layer" includes cases where the layer is formed over the entire area when the area in which the layer exists is observed, as well as cases where the layer is formed over only a part of the area.
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 may be measured using a dial gauge or the like, or it may be measured from a cross-sectional image of the release film. Alternatively, the material constituting the layer may be removed using a solvent or the like, and the thickness may be calculated from the mass before and after removal, the density of the material, the area of the layer, etc. If the layer thickness is not constant, the arithmetic average of values measured at any five points is taken as the layer thickness.
In this specification, "(meth)acrylic" means either or both of acrylic and methacrylic, and "(meth)acrylate" means either or both of acrylate and methacrylate.

<Release film>
The release film of the present disclosure is a release film having a substrate layer, a conductive layer, and a release layer in this order, and the release layer contains polyacrylonitrile particles.

The release film having the above-described configuration exhibits excellent antistatic properties. Specifically, the release film exhibits excellent antistatic properties due to the presence of a conductive layer between the substrate layer and the release layer, and the release layer containing polyacrylonitrile particles.
The reason why the antistatic performance is improved when the release layer contains polyacrylonitrile particles is thought to be that the unshared electron pairs of the nitrogen atoms contained in the polyacrylonitrile particles impart conductivity to the release layer.

An example of the configuration of a release film having a substrate layer, a release layer, and a conductive layer is shown schematically in Figure 1. The release film 40 shown in Figure 1 comprises a substrate layer 10, a release layer 20, and a conductive layer 30 disposed between the substrate layer 10 and the release layer 20.

The release film has a base layer, which provides the release film with the necessary strength, and by appropriately selecting the material, the physical properties such as elongation and elastic modulus can be adjusted.
By having a release layer on the release film, the release film can be easily peeled off from the adherend surface.
By providing the release film with a conductive layer, discharge during application or removal of the release film is suppressed, and electrostatic damage to electronic components is effectively suppressed.

The overall thickness of the release film is not particularly limited and can be set according to the desired physical properties (elongation, elastic modulus, etc.). For example, it may be 30 μm to 300 μm, 35 μm to 250 μm, or 40 μm to 200 μm.

(Base material layer)
The material of the substrate layer is not particularly limited. Examples thereof include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, as well as resins such as polyimide, polyamide, polyester ether, polyamideimide, fluorine-containing resins, and thermoplastic elastomers. The substrate layer may contain one or more types of resins.

From the perspective of film handling, it is preferable that the release film have a certain degree of stiffness. For this reason, the base layer preferably contains polyester, and more preferably contains polyethylene terephthalate.

The base layer may or may not have been stretched. If it has been stretched, the release film tends to have excellent strength, while if it has not been stretched, the release film tends to have excellent extensibility.

The thickness of the base layer is not particularly limited, but is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. When the thickness of the base layer is 10 μm or more, the release sheet is less likely to tear and has excellent handleability.
The thickness of the substrate layer is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less. When the thickness of the substrate layer is 300 μm or less, sufficient conformability to the adherend surface (the property of deforming to match the shape of the adherend surface) can be obtained.

The substrate layer may consist of only one layer, or two or more layers. Methods for obtaining a substrate layer consisting of two or more layers include co-extrusion of the materials for each layer, and lamination of two or more films.

If the release film includes a conductive layer, the surface of the base layer on which the conductive layer is provided may be treated to improve adhesion to the conductive layer. Examples of treatment methods include surface treatments such as corona treatment and plasma treatment, and application of a primer.

If necessary, a backing treatment agent may be applied to the back surface of the base layer (the surface opposite to the side to be attached to the adherend) to adjust the unwinding properties of the release film from the roll. Examples of backing treatment agents include silicone resins, fluorine-containing resins, polyvinyl alcohol, and resins having alkyl groups. If necessary, these backing treatment agents may be modified. One type of backing treatment agent may be used alone, or two or more types may be used in combination.

(Release layer)
The material of the release layer is not particularly limited as long as it contains polyacrylonitrile particles. From the viewpoint of adhesion to the adherend surface, the release layer preferably has adhesiveness. As a method for imparting adhesiveness to the release layer, a method of incorporating an adhesive agent into the release layer can be mentioned.

There are no particular restrictions on the type of adhesive, and it can be selected taking into consideration adhesiveness, releasability, heat resistance, etc. Specifically, acrylic adhesives, silicone adhesives, and urethane adhesives are preferred, with acrylic adhesives being more preferred. The release layer may contain one type of adhesive or two or more types.

The acrylic adhesive is preferably a copolymer (hereinafter also referred to as an acrylic copolymer) obtained by copolymerizing a main monomer with a low glass transition temperature (Tg) (e.g., -20°C or below), such as butyl acrylate, ethyl acrylate, or 2-ethylhexyl acrylate, with a monomer having a functional group, such as (meth)acrylic acid, hydroxyethyl (meth)acrylate, hydroxyethyl (meth)acrylate, (meth)acrylamide, or (meth)acrylonitrile. The above "glass transition temperature" refers to the glass transition temperature of a homopolymer obtained using the corresponding monomer.

The acrylic copolymer may be a cross-linked acrylic copolymer. Cross-linked acrylic copolymers can be synthesized by cross-linking the monomers that serve as raw materials for the acrylic copolymer using a cross-linking agent. Examples of cross-linking agents used to synthesize cross-linked acrylic copolymers include known cross-linking agents such as isocyanate compounds, melamine compounds, and epoxy compounds. Furthermore, in order to form a loosely dispersed network structure in the acrylic adhesive, it is more preferable that the cross-linking agent be a multifunctional cross-linking agent, such as a trifunctional or tetrafunctional cross-linking agent.

The content of polyacrylonitrile particles in the release layer is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more of the total release layer. When the content of polyacrylonitrile particles is 10% by mass or more of the total release layer, the polyacrylonitrile particles tend to function sufficiently as conductive paths in the release layer, and sufficient antistatic performance tends to be obtained.
From the viewpoint of suppressing cohesive failure of the release layer and the generation of residues on the adherend surface, the content of polyacrylonitrile particles is preferably 50% by mass or less of the entire release layer, more preferably 40% by mass or less, and even more preferably 30% by mass or less.

From the viewpoint of imparting sufficient conductivity to the release layer, the ratio (A/B) of the average particle diameter A of the polyacrylonitrile particles to the thickness B of the release layer is preferably greater than 0.7, more preferably 0.75 or more, even more preferably 0.8 or more, even more preferably 0.9 or more, and even more preferably 0.95 or more.
When the ratio (A/B) of the average particle diameter A of the polyacrylonitrile particles to the thickness B of the release layer is 0.75 or more, the polyacrylonitrile particles tend to function sufficiently as a conductive path, and sufficient antistatic performance tends to be obtained.
From the viewpoint of suppressing detachment of polyacrylonitrile particles from the release layer, A/B is preferably 2.0 or less, and more preferably 1.7 or less.

The thickness B of the release layer is the thickness of the release layer containing polyacrylonitrile particles in the thickness direction of the release film. If the thickness is not constant, the cross section obtained after cutting the release film is observed with an SEM, and the arithmetic average of the thicknesses at five arbitrarily selected points is taken as the thickness B of the release layer.

Furthermore, if the approximate resin composition can be determined using known analytical methods, the release layer can be removed using a solvent such as methyl ethyl ketone as described in the Examples, and the thickness B of the release layer can be calculated from the difference in mass of the release film before and after removal, the specific gravity of the resin removed with the solvent, and the volume of the polyacrylonitrile particles remaining as insoluble matter.

The average particle size of the polyacrylonitrile particles may be, for example, in the range of 1 μm to 50 μm, in the range of 5 μm to 30 μm, or in the range of 7 μm to 20 μm.

In this disclosure, the average particle size of particles is the particle size (D50) at which the cumulative percentage from the smallest diameter side reaches 50% in the volume-based particle size distribution measured by laser diffraction/scattering.

The particle shape of the polyacrylonitrile particles is not particularly limited, and may be spherical or non-spherical (flat, irregular, etc.).
From the viewpoint of incorporating a sufficient amount into the release layer, the polyacrylonitrile particles are preferably non-spherical. For example, the average aspect ratio (major axis/minor axis) of the polyacrylonitrile particles may be 1.1 or more, 1.2 or more, or 1.5 or more. The average aspect ratio of the polyacrylonitrile particles may be 10 or less, 7 or less, or 5 or less.
In the present disclosure, the average aspect ratio of particles is defined as the arithmetic mean value of the aspect ratios of 100 arbitrarily selected particles.

The average particle size of polyacrylonitrile particles contained in a release film can be measured using the following procedure. The release layer of the release film is removed using a solvent such as methyl ethyl ketone, and the polyacrylonitrile particles remaining as insoluble matter are analyzed for volume-based particle size distribution measured by laser diffraction/scattering. The particle size (D50) at which the cumulative total from the smallest diameter side reaches 50% is taken as the average particle size.

The release layer may contain only polyacrylonitrile particles, or may contain polyacrylonitrile particles and particles other than polyacrylonitrile particles.

The material of the particles other than polyacrylonitrile particles is not particularly limited, and may be an organic material such as a resin, an inorganic material such as a metal or metal oxide, or a combination of an organic material and an inorganic material.

From the viewpoint of affinity with the adhesive contained in the release layer, it is preferable that the particles other than polyacrylonitrile particles be resin particles. Examples of resins that make up the resin particles include acrylic resin, olefin resin, styrene resin, and silicone resin. From the viewpoint of suppressing residue on the surface of the semiconductor package after molding, acrylic resin is preferred.

The average particle size of particles other than polyacrylonitrile particles is not particularly limited. For example, it can be selected from the range of 1 μm to 20 μm.

When the release layer contains polyacrylonitrile particles and particles other than polyacrylonitrile particles, from the viewpoint of imparting sufficient conductivity to the release layer and suppressing cohesive failure of the release layer, it is preferable that the proportion of polyacrylonitrile particles in the total particles be 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more.

The release layer may contain components other than the adhesive and particles as needed. For example, it may contain an anchoring enhancer, a crosslinking accelerator, a colorant, etc.

The thickness of the release layer is not particularly limited, but is preferably 0.1 μm or more, and more preferably 1 μm or more. When the thickness of the release layer is 0.1 μm or more, sufficient adhesive strength to the electronic component is obtained, and penetration of the sealing material is effectively suppressed.
The thickness of the release layer may be 100 μm or less, 50 μm or less, or 10 μm or less. When the thickness of the release layer is 100 μm or less, heat shrinkage stress is less likely to occur during thermal curing of the release layer, and the flatness of the release film is easily maintained. Furthermore, when the release film has a conductive layer, the distance from the conductive layer to the surface of the release layer is not too far, so that the surface resistivity is maintained low, and electrostatic damage to electronic components is effectively suppressed.
Taking into consideration the ease of forming the release layer (coating properties, etc.), ensuring adhesive strength, ensuring antistatic properties, etc., it is more preferable that the thickness of the release layer is 3 μm to 50 μm.

(Conductive layer)
The conductive layer is not particularly limited in configuration as long as it can increase the conductivity of the release film and suppress charging. For example, it may be a layer containing a conductive material such as an antistatic agent, a conductive polymer material, or a metal.

Examples of antistatic agents contained in the conductive layer include cationic antistatic agents having a cationic group such as a quaternary ammonium salt, a pyridinium salt, or a primary to tertiary amino group; anionic antistatic agents having an anionic group such as a sulfonate group, a sulfate group, or a phosphate group; amphoteric antistatic agents such as amino acid-based or amino acid sulfate-based; nonionic antistatic agents having a nonionic group such as an amino alcohol-based, glycerin-based, or polyethylene glycol-based; and polymeric antistatic agents obtained by increasing the molecular weight of these antistatic agents. The antistatic agent may be a combination of a main agent and an auxiliary agent (such as a curing agent).
Examples of the conductive polymer material contained in the conductive layer include polymer compounds having polythiophene, polyaniline, polypyrrole, polyacetylene, or the like in the skeleton.
Examples of metals include aluminum, copper, gold, chromium, and tin, with aluminum being preferred from the viewpoint of availability.

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

The thickness of the conductive layer is not particularly limited as long as it provides a sufficient antistatic effect for the release film. For example, it may be in the range of 0.01 μm to 1 μm.

The release film of the present disclosure can be used for various purposes. For example, it can be used to temporarily protect at least a part of the surface of an object. Since the release film of the present disclosure has excellent conformability to the adherend surface, when processing is performed around the area where the release film is attached, the area can be effectively protected from the influence of the processing.
In the present disclosure, "temporarily protect" refers to protecting the part of the surface of an object to which the release film is attached from the time the release film is attached to at least a part of the surface until the time the release film is peeled off.

The type of processing to be performed on the periphery of the region where the release film is attached is not particularly limited. Specific examples include sealing with a sealant, roughening treatment, painting treatment, water-repellent treatment, antistatic treatment, etc.
The release film may be one used in exposure molding.

<Method of manufacturing electronic component device>
The method for manufacturing an electronic component device of the present disclosure includes a step of sealing the periphery of the electronic component with the above-mentioned release film in contact with at least a portion of the surface of the electronic component, and a step of peeling the release film from the electronic component.

As mentioned above, the release film of the present disclosure has excellent antistatic properties. This effectively prevents electrostatic damage to electronic components.

The type of electronic component used in the above method is not particularly limited, and examples thereof include semiconductor elements, capacitors, terminals, etc.
In the above method, the type of material (sealant) used to seal the periphery of the electronic component is not particularly limited, and examples thereof include resin compositions containing epoxy resins, acrylic resins, etc.

The release film of the present disclosure will be described below based on examples. However, the present disclosure is not limited to the following examples.

Example 1
As the substrate layer, a biaxially stretched polyethylene terephthalate film (product name "S-38", Unitika Ltd.) having a thickness of 38 μm and having been subjected to a corona treatment on one side was prepared.
The following antistatic agent was diluted to 2.5% by mass with a mixed solvent (water/isopropyl alcohol = 1/1 (mass ratio)) and applied to the corona-treated surface of the substrate layer, and heated at 100°C for 1 minute to form a conductive layer.

The antistatic agent used to prepare the release film was a mixture of the following component A (100 parts by mass) and component B (25 parts by mass).

Component A: A cationic antistatic agent, which is an acrylic copolymer containing a quaternary ammonium salt, product name "Bondip PA-100 Main Agent", Konishi Co., Ltd. Component B: An epoxy-based curing agent, product name "Bondip PA-100 Curing Agent", Konishi Co., Ltd.

The following composition for forming a release layer was applied onto the formed conductive layer and heated at 100° C. for 1 minute to form a release layer, thereby producing a release film.
The release layer forming composition used to prepare the release film was a mixture of the following adhesive (100 parts by mass), crosslinking agent (10 parts by mass), resin particles A (25 parts by mass), and 34 parts by mass of a mixed solvent (toluene/methyl ethyl ketone = 8:2 (mass ratio)).

Adhesive: Acrylic adhesive, trade name "B-3", Lion Specialty Chemicals Co., Ltd., mixture of multiple types of methacrylic acid ester monomers. Crosslinker: Hexamethylene diisocyanate crosslinker, trade name "Coronate H-CL", Nippon Polyurethane Industry Co., Ltd. Resin particles A: Polyacrylonitrile particles, trade name "Taftic ASF-7", Toyobo Co., Ltd., volume average particle diameter: 7 μm, irregular shape.

Example 2
A release film was produced in the same manner as in Example 1, except that the amount of resin particles A was changed to 30 parts by mass.

Example 3
A release film was produced in the same manner as in Example 1, except that the amount of resin particles A was changed to 40 parts by mass.

Example 4
A release film was produced in the same manner as in Example 1, except that the resin particles A were changed to the following resin particles B and the amount thereof was changed to 30 parts by mass.
Resin particles B: Polyacrylonitrile particles, trade name "Tuftic AM", Toyobo Co., Ltd., volume average particle diameter: 10 μm, irregular shape

Example 5
A release film was produced in the same manner as in Example 1, except that the amount of resin particles A was changed to 15 parts by mass.

<Comparative Example 1>
A release film was produced in the same manner as in Example 1, except that resin particles A were not added to the composition for forming the release layer.

<Comparative Example 2>
A release film was produced in the same manner as in Comparative Example 1, except that 25 parts by mass of the following resin particles C were added to the composition for forming a release layer.
Resin particles C: Polyacrylic particles, product name "MX-1000", Soken Chemical & Engineering Co., Ltd., volume average particle diameter: 10 μm, spherical

<Comparative Example 3>
A release film was produced in the same manner as in Comparative Example 2, except that the amount of resin particles C was changed to 40 parts by mass.

<Comparative Example 4>
A release film was produced in the same manner as in Comparative Example 2, except that resin particles C were changed to 25 parts by mass of resin particles D described below.
Resin particles D: Polyacrylic particles, product name "MX-500", Soken Chemical & Engineering Co., Ltd., volume average particle diameter: 5 μm, spherical

Comparative Example 5
A release film was produced in the same manner as in Comparative Example 4, except that the amount of resin particles D was changed to 40 parts by mass.

<Evaluation test>
The prepared release films were subjected to the following evaluation tests.

<Release layer thickness>
The release layer of the prepared release film was removed with methyl ethyl ketone, and the thickness of the release layer was calculated from the difference in mass of the release film before and after removal. The results are shown in Table 1.

<Glue residue>
A release film was pressed onto the surface of a mirror-finished SUS (stainless steel) plate at 180°C, 16 MPa, and 5 minutes. After pressing, the plate was left to cool to room temperature (25°C), and then the release film was peeled off from the SUS plate. The surface of the SUS plate was visually observed, and the state of adhesive residue was evaluated as OK if no adhesive residue was observed, and NG if adhesive residue was observed. The results are shown in Table 1.

<Surface resistivity>
The surface resistivity of the release layer side of the release film was measured using an insulation resistance meter (digital ultra-high resistance/microcurrent meter manufactured by Advantest Corporation). Specifically, the release film was left in an atmosphere of 23±2°C and 50±10% RH for 1 hour, and then a voltage of 500 V was applied for 1 minute, after which the surface resistance value (Ω) was measured, and the surface resistivity (Ω/□) was calculated using the following formula. The results are shown in Table 1.

Surface resistivity = π(D+d)/(D-d)×R
π: circumference constant, D: inner diameter of ring-shaped electrode, d: outer diameter of ring-shaped electrode, R: surface resistivity The value of π(D+d)/(D−d) used to calculate the surface resistivity was 18.84.

As shown in the results in Table 1, the release films of the examples, in which the release layer contains polyacrylonitrile particles, have lower surface resistivity and are considered to have superior antistatic performance compared to the release films of the comparative examples, in which the release layer does not contain polyacrylonitrile particles.

Claims (7)

a substrate layer, a conductive layer, and a release layer in this order, the release layer containing polyacrylonitrile particles;
A release film, wherein the ratio (A/B) of the average particle size A of the polyacrylonitrile particles to the thickness B of the release layer is 1.04 or more . The release film according to claim 1, wherein the ratio (A/B) of the average particle size A of the polyacrylonitrile particles to the thickness B of the release layer is 2.0 or less. The release film according to claim 1 or claim 2, wherein the content of the polyacrylonitrile particles is 10% by mass or more of the entire release layer. The release film according to any one of claims 1 to 3, wherein the release layer contains an adhesive. The release film according to any one of claims 1 to 4, for temporarily protecting at least a portion of the surface of an object. The release film according to any one of claims 1 to 5, which is for exposure molding. A method for manufacturing an electronic component device, comprising the steps of: sealing the periphery of an electronic component with the release film according to any one of claims 1 to 6 in contact with at least a portion of the surface of the electronic component; and peeling the release film from the electronic component.