JP2002321300A - Adhesive film and method for producing the same - Google Patents

Abstract

(57) [Problem] With the rapid progress of high performance, high functionality, and miniaturization of portable terminal equipment and electronic equipment, a substrate for mounting electronic components such as semiconductor elements used in electronic equipment has been developed. It is an object of the present invention to provide an adhesive film which is thin and has excellent dimensional stability, heat resistance and adhesive strength and is suitable for electronic substrate materials in order to meet the demand for higher density and higher performance. SOLUTION: An adhesive film having an adhesive layer having a thickness of 2 to 5 μm on one or both sides of a heat-resistant film having a thickness of 3 to 10 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive film having an adhesive layer on one or both sides of a heat-resistant film and a method for producing the same, and more particularly, to an adhesive layer having a specific thickness range and a heat-resistant film having a specific thickness range. The present invention relates to a thin adhesive film for an electronic substrate material, which is composed of a film layer and has excellent heat resistance and can be suitably used for a flexible printed wiring board, a high-density mounting board, and the like.

[0002]

2. Description of the Related Art In recent years, with the rapid progress of IT technology,
2. Description of the Related Art Higher performance, higher functionality, and smaller size of electronic devices such as portable terminal devices, computers, and displays are rapidly progressing. Along with this, electronic components such as semiconductor elements used in electronic devices and substrates on which they are mounted are required to have higher density and higher performance. Flexible printed wiring boards (hereinafter referred to as FPC
), Wiring patterns are thinned and multilayers are formed, and component mounting FPCs in which components are directly mounted on the FPC, double-sided FPCs in which circuits are formed on both sides,
Multi-layer FP with multiple FPCs stacked and interconnected by wiring
C and the like have appeared. For this reason, the demands for thinner and dimensional stability materials for flexible printed boards have become more severe. Generally FPC
Is manufactured by bonding a copper foil to one or both sides of a heat-resistant film (hereinafter, referred to as a base film) via an adhesive layer to form a copper-clad laminate, and etching the copper foil to form a desired circuit pattern. Is done. As the base film, a film made of a polyimide resin having excellent heat resistance, mechanical properties, and other properties is widely used. Further, an epoxy resin or an acrylic resin having excellent insulating properties and heat resistance has been used for the adhesive layer, but a thermoplastic polyimide resin having excellent heat resistance has come to be used. FP
In order to make C thinner, both the copper foil and the resin layer composed of the insulating organic film and the adhesive layer must be made thinner. However, thinning the adhesive layer poses a problem from the viewpoint of the reliability of adhesion to the copper foil. In addition, thinning the insulating organic film has problems in handling properties during processing, FPC strength and dimensional stability. The dimensional stability of the FPC means that the dimensional change when processing the copper-clad laminate into the FPC is small, and that the dimensional change of the FPC with respect to the environmental change is small. Conventionally, it has been important that the dimensional change during processing, in particular, when the temperature and moisture absorption / desorption change are large, is small. However, as the density increases, it is also important that the dimensional change due to moisture absorption after processing is small. . In order to reduce the dimensional change, it is necessary to balance the characteristics (linear expansion coefficient, hygroscopic expansion coefficient, and elastic modulus) of the copper foil, the adhesive layer, and the base film. When the base film is thinned without changing the thickness of the adhesive layer, copper foil,
There has been a problem that the above-mentioned property balance between the adhesive layer and the base film is largely lost, and as a result, the dimensional change is large.

[0003]

[Problems to be Solved by the Invention] It is increasingly important to make electronic substrates such as FPCs thinner in the future.
For that purpose, it is necessary to reduce the thickness of the resin layer comprising the adhesive layer and the heat-resistant film, which constitutes the electronic substrate. Therefore, as a result of extensive research for the purpose of providing an adhesive film used for an electronic substrate such as an FPC which is excellent in the above-mentioned problem relating to this case, that is, thinning, dimensional characteristics, adhesive strength, and even heat resistance, This has led to the present invention.

[0004]

The gist of the adhesive film and the method for producing the same according to the present invention is as follows.
10 μm heat-resistant film with a thickness of 2 on one or both sides
The adhesive film according to the present invention has a tensile elasticity of 9 to 12 GPa, a coefficient of linear expansion at 20 to 300 ° C. of 1 to 10 ppm, and an adhesive film according to the present invention. The coefficient of hygroscopic expansion at 50 ° C. is 1
It is characterized by being 10 to 10 ppm (claim 2). Further, the gist of the adhesive film according to the present invention is as follows.

[0005]

Embedded image (Wherein, X ^{1 to} X ⁴ and Y ^{1 to} Y ⁴ each independently represent any one of a hydrogen atom, an alkyl group having 2 or less carbon atoms, and a halogen group) (Claim 3), and the heat-resistant film is made of a polyimide resin (Claim 4). The adhesive film according to the present invention is characterized in that the adhesive layer is made of a resin composition containing thermoplastic polyimide as a main component (claim 5). In addition, the gist of the method for producing an adhesive film according to the present invention includes (1) a step of applying a polyamic acid solution to the surface of a heat-resistant film and drying the solution;
Heating in a far-infrared furnace to imidize the polyamic acid,
(Claim 6).

[0006]

Embodiments of the present invention will be described below. First, the configuration of the adhesive film according to the present invention will be described. The adhesive film of the present invention has an adhesive layer on one or both sides of the heat-resistant film, the thickness of the heat-resistant film is 3 to 10 μm, the thickness of the adhesive layer is 2 to
5 μm. The most suitable film as the heat-resistant film has a tensile modulus in the range of 9 to 12 GPa, 20 to 20 GPa.
The linear expansion coefficient at 300 ° C. is in the range of 1 to 10 ppm, 50
The film has a coefficient of hygroscopic expansion at 1 ° C. in the range of 1 to 10 ppm. Examples of the heat-resistant film include, for example, an aromatic polyester film, an aromatic polyamide film, a polyimide film, and the like.

[0007]

Embedded image (Wherein X1 to X4 and Y1 to Y4 each independently represent any one of a hydrogen atom, an alkyl group having 2 or less carbon atoms, and a halogen group) And a polyimide film are preferable, and a polyimide film is most preferable because it is excellent in mutual balance of various properties such as heat resistance (particularly, long-term heat resistance at 200 ° C. or more), flexibility, and low water absorption.

The preferred resin used for the adhesive layer in the adhesive film of the present invention is an epoxy resin, an acrylic resin, a polyamide resin, a resin containing thermoplastic polyimide as a main component, etc. because of its excellent insulating properties and heat resistance. However, it is most preferable to use a thermoplastic polyimide as a main component, which is more excellent in heat resistance (in particular, long-term heat resistance of 200 ° C. or more). Hereinafter, the case where the heat-resistant film is a polyimide film and the adhesive layer is a resin whose main component is thermoplastic polyimide will be described more specifically.

[0009] The polyimide film can be manufactured by a known method. That is, the film can be obtained by casting or applying a solution containing polyamic acid, which is a precursor material of polyimide, to a support, and then chemically or thermally imidizing the solution. The polyamic acid, which is a precursor substance of the polyimide according to the present invention, usually has at least one acid dianhydride and at least one diamine as starting materials, and dissolves both in an organic solvent in a substantially equimolar amount. After the reaction, the mixture can be manufactured by stirring while controlling the reaction conditions such as temperature until the polymerization is completed. Specific examples of the acid dianhydride include pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic acid Acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4 ′
-Benzophenonetetracarboxylic dianhydride, 3,
3 ', 4,4'-oxydiphthalic dianhydride, p-phenylenebis (trimellitic acid monoester anhydride),
4,4′-biphenylbis (trimellitic acid monoester acid anhydride) and their analogs (derivatives) are exemplified. Among the acid dianhydrides exemplified above, pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride , P-phenylenebis (trimellitic acid monoester anhydride) and 4,4'-biphenylbis (trimellitic acid monoester anhydride) are particularly preferred. These acid dianhydrides may be used alone or in combination of two or more at an arbitrary ratio. As the above-mentioned diamine, specifically, for example, 3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine, 3,
3'-dichlorobenzidine, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl ether, 1,5-
Diaminonaphthalene, 1,4-diaminobenzene (p-
Phenylenediamine), 1,3-diaminobenzene,
Examples thereof include 1,2-diaminobenzene, 4,4′-diaminobenzanilide, 3,4′-diaminobenzanilide and their analogs (derivatives). Among the diamines exemplified above, 3,3′-dimethylbenzidine,
3'-dimethoxybenzidine, 3,3'-dichlorobenzidine, 4,4'-diaminobenzanilide, 4,
4'-diaminodiphenyl ether and p-phenylenediamine are more preferred, and 4,4'-diaminobenzanilide is particularly preferred. These diamines may be used alone or in combination of two or more at an arbitrary ratio. And, in order to obtain a polyimide film more suitable as the heat-resistant film according to the present invention, the following formula

[0010]

Embedded image (Wherein X1 to X4 and Y1 to Y4 each independently represent a hydrogen atom or an alkyl group having 2 or less carbon atoms (as specific examples,
A methyl group, an ethyl group, a tetrafluoromethyl group, and a pentafluoroethyl group are preferable, and a methyl group is more preferable in that a film having heat resistance and a high elastic modulus can be obtained. It is necessary to use an acid dianhydride and / or a diamine containing a structural unit represented, but it is more preferable to use a diamine containing the structural unit. That is, the general formula (1)

[0011]

Embedded image (Wherein X1 to X4 and Y1 to Y4 each independently represent a hydrogen atom or an alkyl group having 2 or less carbon atoms (as specific examples,
A methyl group, an ethyl group, a tetrafluoromethyl group, and a pentafluoroethyl group are preferable, and a methyl group is more preferable in that a film having heat resistance and a high elastic modulus can be obtained. Diamine represented by general formula (2)

[0012]

Embedded image (Wherein R1 represents a tetravalent organic group (preferably having at least one aromatic ring)) to obtain a polyamic acid by reacting with an acid dianhydride represented by More preferably, the polyamic acid is imidized to obtain a polyimide. The combination of acid dianhydride and diamine, and the molar ratio (compounding ratio) of each compound when two or more acid dianhydrides are used, and the compounding ratio of each compound when two or more diamines are used, are polyimide. The heat-resistant film may be appropriately selected and set so that the elastic modulus, the coefficient of linear expansion, and the coefficient of hygroscopic expansion are in specific ranges and / or include the specific structural units. Among them, pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ′, 4,4 '
At least one acid dianhydride among biphenyltetracarboxylic dianhydride and p-phenylenebis (trimellitic acid monoester anhydride); 4,4′-diaminobenzanilide; and 4,4′-diamino A combination with at least one diamine of diphenyl ether and p-phenylenediamine is more preferable, and p-phenylenebis (trimellitic acid monoamine) is more excellent in the mutual balance of various properties such as low water absorption and flexibility. Particularly preferred is a combination of (ester anhydride) and 4,4′-diaminobenzanilide. When two or more acid dianhydrides are used, the proportion of p-phenylenebis (trimellitic acid monoester acid anhydride) in the total amount of the acid dianhydrides is more preferably 40 mol% or more. When two or more diamines are used, the proportion of 4,4′-diaminobenzanilide in the total amount of the diamine is more preferably 50 mol% or more. By appropriately combining the dianhydride and the diamine, a heat-resistant film having an elastic modulus, a linear expansion coefficient and a hygroscopic expansion coefficient within a specific range can be easily obtained. The elastic modulus is preferably in the range of 9 to 12 GPa, and more preferably in the range of 9.5 to 11 GPa. The coefficient of linear expansion is preferably in the range of 1 to 10 ppm, and more preferably in the range of 3 to 8 ppm. The coefficient of hygroscopic expansion is preferably in the range of 1 to 10 ppm, and more preferably in the range of 3 to 8 ppm. Specific examples of the organic solvent used for obtaining the polyamic acid include N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), and N-methyl-2-pyrrolidone (NMP).
And the like. Among the organic solvents exemplified above, N, N-dimethylformamide is particularly preferred.
These organic solvents may be used alone, or may be a mixed solvent obtained by mixing two or more kinds at an arbitrary ratio. The polyamic acid solution is obtained by dissolving the acid dianhydride and the diamine in the organic solvent and then polymerizing. More specifically, for example, there is a method in which a diamine is dissolved in an organic solvent and a substantially equimolar amount of an acid dianhydride is mixed with the diamine and polymerized. As a method of mixing the acid dianhydride, the acid dianhydride in a powder form or the like may be directly mixed, or a solution in which the acid dianhydride is dissolved in an organic solvent may be mixed. More preferably, a method in which a solution in which a diamine is dissolved in an organic solvent is mixed with a solution in which an acid dianhydride is dissolved in an organic solvent. That is, a solution in which 70 to 98.5 mol% of an acid dianhydride is directly mixed with a solution in which a diamine is dissolved in an organic solvent, and then the remaining acid dianhydride is dissolved in the organic solvent. Is more preferable. In addition to the above method of dissolving all diamines in an organic solvent before mixing the acid dianhydride, mixing the acid dianhydride with a solution in which a part (or one component) of the diamine is dissolved in the organic solvent And then
Mixing the remaining (or other components) diamine,
A method of sequentially mixing a diamine and an acid dianhydride in an organic solvent can also be employed. Furthermore, a method in which the mixing order of the acid dianhydride and the diamine is changed, that is, a solution obtained by dissolving the acid dianhydride in an organic solvent is mixed with the dianhydride in a substantially equimolar amount with the acid dianhydride. A method of polymerizing can also be adopted. Therefore, the mixing order and mixing method of the acid dianhydride and the diamine are not particularly limited. The temperature at the time of polymerizing the acid dianhydride and the diamine is 0 to 80 ° C.
Is preferably within the range. In addition, since the polymerization is inhibited by the presence of water, the polymerization reaction is preferably performed in a dehumidified atmosphere. The concentration of the polyamic acid in the polyamic acid solution is preferably in the range of 10 to 25% by weight as a solid content. By using an acid dianhydride and a diamine such that the concentration of the polyamic acid is within the above range, a polyamic acid having a suitable molecular weight (preferably 50,000 or more, preferably 100,000 or more) is obtained, and A solution having a high viscosity (preferably 1000 poise (23 ° C.) or more, more preferably 2000 poise (23 ° C.) or more) is obtained. The imidation may be performed by any one of a thermal curing method and a chemical curing method. The thermal curing method is a method in which the imidization reaction proceeds only by heating without using a dehydrating ring-closing agent or the like.
The chemical curing method is a method in which a chemical conversion agent and a catalyst are added to a polyamic acid solution to advance an imidization reaction. Of these methods, the chemical cure method is more preferred. Further, a chemical curing method and a heat curing method may be used in combination. Examples of the chemical conversion agent include aliphatic acid anhydrides, aromatic acid anhydrides, N, N′-dialkylcarbodiimides, lower aliphatic halides, halogenated lower fatty acid anhydrides, arylphosphonic dihalides, Thionyl halide and the like. One of these chemical conversion agents may be used alone, or two or more thereof may be used in combination. Among the chemical conversion agents exemplified above, aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and lacnic anhydride, and mixtures of these compounds are more preferred. Examples of the catalyst include an aliphatic tertiary amine, an aromatic tertiary amine, and a heterocyclic tertiary amine.
These catalysts may be used alone or in combination of two or more. Among the catalysts exemplified above, heterocyclic tertiary amines such as isoquinoline, β-picoline and pyridine are particularly preferred. The conditions for imidization may be appropriately set depending on the type of polyamic acid, the thickness of the film to be formed, whether the thermal curing method and / or the chemical curing method is employed, and the like. Hereinafter, a method for producing a polyimide film from a polyamic acid solution using a chemical curing method as a method for producing a heat-resistant film will be described more specifically. First, a polyamic acid solution is obtained by the method described above. After the chemical conversion agent and the catalyst are added to the polyamic acid solution, they are cast or coated on a suitable support. Next, this is heated gently at a temperature of, for example, about 100 ° C. to activate the chemical conversion agent and the catalyst, and to partially cure (imidize) or partially dry the polyamic acid film ( (Hereinafter referred to as a gel film). The gel film has a self-supporting property at an intermediate stage of imidization from polyamic acid to polyimide. The gel film is in a partially cured (imidized) or partially dried state, and contains a polyamic acid and a polyimide obtained by imidating the polyamic acid. Next, in order to suppress shrinkage in the tenter process, the end of the obtained gel film is held using a tenter clip or pin for suppressing shrinkage. Thereafter, the gel film is dried and imidized by heating the gel stepwise to obtain a polyimide film. More specifically, a method is preferred in which the gel film is divided into a plurality of sections by a partition plate and passed through a tenter furnace in which the temperature is set for each section for 15 to 400 seconds to heat. The temperature in the furnace is preferably set so that the gel film is heated stepwise from a temperature of about 200 ° C. to finally a temperature of about 400 ° C. Further, in order to obtain a polyimide film having more uniform thickness and quality of various characteristics, it is preferable to heat the gel film in the width direction without temperature unevenness. Thereby, a polyimide film as a heat-resistant film in the adhesive film is obtained. The molecular weight of the polyimide is not particularly limited, but in order to maintain the strength of the adhesive film, it is more preferable that the number average molecular weight of the polyamic acid, which is a precursor substance of the polyimide, is 100,000 or more. preferable. Incidentally, it is difficult to directly measure the molecular weight because polyimide is insoluble, but the molecular weight of polyamic acid can be measured by GPC (gel permeation chromatography). Next, a method for preparing the thermoplastic polyimide constituting the adhesive layer will be described. The thermoplastic polyimide can be obtained basically by the same manufacturing method as the method for manufacturing the polyimide film. As the acid dianhydride suitable for obtaining a polyamic acid which is a precursor of a thermoplastic polyimide, specifically,
For example, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4,4′-benzophenonetetraanhydride Carboxylic dianhydride, 2,2-bis (3,4
-Dicarboxyphenyl) propane dianhydride, 3,4
9,10-perylenetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) propane dianhydride,
1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride Anhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, 3,3 ′, 4,4′-diphenylethertetracarboxylic dianhydride, bis (3,4
-Dicarboxyphenyl) sulfone dianhydride, ethylene bis (trimellitic acid monoester acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride) and their analogs (derivatives).
Among the acid dianhydrides exemplified above, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3
3'-biphenyltetracarboxylic dianhydride, ethylene bis (trimellitic acid monoester acid anhydride) and bisphenol A bis (trimellitic acid monoester acid anhydride) are particularly preferred. One of these acid anhydrides may be used alone, or two or more thereof may be used in combination at an arbitrary ratio. As the diamine suitable for obtaining a polyamic acid which is a precursor of a thermoplastic polyimide, specifically, for example, 4,4′-diaminodiphenylpropane,
4,4′-diaminodiphenylmethane, 3,3′-dimethylbenzidine, 3,3′-dimethoxybenzidine,
3,3′-dichlorobenzidine, 3,3′-dihydroxybenzidine, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfone, 4,4 ′
Diaminodiphenyl sulfone, 4,4′-diaminodiphenyl ether, 1,5-diaminonaphthalene, 4,
4'-diaminodiphenyldiethylsilane, 4,4'-
Diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 1,3-diaminobenzene, 1,2-diaminobenzene, 2,2-bis (4-
Aminophenoxyphenyl) propane, 1,2- (4-
Aminophenoxyethoxy) ethane and their analogs (derivatives). Among the diamines exemplified above, 3,3′-dihydroxybenzidine, 3,3′-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylether, 2,2-bis (4-amino Phenoxyphenyl) propane and 1,2- (4-aminophenoxyethoxy) ethane are particularly preferred. One of these diamines may be used, or two or more of them may be used in combination at an arbitrary ratio. The combination of acid dianhydride and diamine, the molar ratio of each compound when two or more acid dianhydrides are used (mixing ratio), and the compounding ratio of each compound when two or more diamines are used are thermoplastic thermoplastics. What is necessary is just to select and set suitably so that a plastic polyimide may be obtained. The polyamic acid, which is a precursor of the thermoplastic thermoplastic polyimide, has the above-mentioned at least one acid dianhydride and at least one diamine as starting materials, and dissolves both in an organic solvent in a substantially equimolar amount. After that, it can be obtained by stirring until polymerization is completed while controlling reaction conditions such as temperature. In the present invention, as long as the various properties to be provided as a thermoplastic polyimide resin are not impaired, if necessary, a monomer other than the acid dianhydride and the diamine, for example, an epoxy monomer or the like as a starting material component May be used. The thermoplastic polyimide can be obtained by chemically or thermally imidizing the polyamic acid.
The adhesive film according to the present invention can be obtained by laminating an adhesive layer on one side or both sides of a heat-resistant film. As a method of laminating the adhesive layer, when the adhesive layer is mainly composed of thermoplastic polyimide, specifically, for example,
A method of thermally fusing a film mainly composed of thermoplastic polyimide to a heat-resistant film; a method of thermally fusing a gel film of thermoplastic polyimide to a heat-resistant film, followed by further imidization; the thermoplastic polyimide is soluble In this case, a method of applying a resin solution containing the thermoplastic polyimide as a main component to a heat-resistant film and then drying; a method of applying a resin solution containing a polyamic acid as a main component to a heat-resistant film, followed by drying and imidization; And the like. Further, at the stage where the heat-resistant film is a gel film, an adhesive layer containing thermoplastic polyimide as a main component may be formed on the gel film. Among these, a method of applying a solution containing a polyamic acid as a main component to the heat-resistant film in view of the adhesiveness between the heat-resistant film and the adhesive layer, and then laminating by drying and thermally imidizing is particularly preferred. preferable. When thermally imidizing the above, using a far infrared furnace,
Preferably, 90 mol% or more of the polyamic acid is imidized. Although the molecular weight of the thermoplastic polyimide is not particularly limited, the number average molecular weight is preferably 50,000 or more, and preferably 80,000 or more, so that the adhesive strength and strength can be maintained as an adhesive layer. More preferably, it is more preferably 100,000 or more. The molecular weight of the thermoplastic polyimide or polyamic acid (solution) can be measured by GPC (gel permeation chromatography). The thickness of the adhesive film according to the present invention is, when having an adhesive layer on both sides, in order to achieve both adhesiveness, dimensional stability and ease of handling and to make the entire adhesive film thinner, within the range of 7 to 20 μm. Yes, 10-18
The range is particularly preferably in the range of μm, and particularly preferably 5 to 15 μm when the adhesive layer is provided on one side. In order to make the thickness of the adhesive film within the above range, the thickness of the heat-resistant film is in the range of 3 to 10 μm, and the thickness of the adhesive layer is 2 to
It is necessary to be within the range of 5 μm. When the thickness of the heat-resistant film is less than 3 μm, the strength and handleability of the adhesive film are reduced, and wrinkles are generated or the adhesive film is torn in a step of attaching a copper foil. Further, the adhesive film is stretched by the tension applied to the adhesive film in the copper foil attaching step, and the dimensional stability of the obtained FPC is greatly impaired, which is not preferable. Conversely, if it exceeds 10 μm, the thickness of the adhesive layer must be increased in order to maintain dimensional stability, and the purpose of thinning a substrate such as an FPC cannot be achieved. If the thickness of the adhesive layer is less than 2 μm, the adhesiveness to the copper foil will be reduced. Conversely, if it exceeds 5 μm, the thickness of the heat-resistant film must be increased to maintain dimensional stability and strength. The purpose of making the substrate thinner cannot be achieved. Although one embodiment of the adhesive film according to the present invention has been described, the present invention is not limited to the embodiment, and various improvements based on the knowledge of those skilled in the art without departing from the gist of the present invention. , Changes and modifications. Less than,
The present invention will be described more specifically with reference to examples.

[0013]

EXAMPLES The elastic modulus and the coefficient of linear expansion of the base film in each of the examples and comparative examples were measured by the following methods. Furthermore, the adhesive strength and the dimensional change of the copper-clad laminate obtained in each of the examples and comparative examples were measured by the following methods.

[Elastic Modulus of Heat Resistant Film] Using an autograph (AG2000A; manufactured by Shimadzu Corporation),
Perform a tensile test of the film in accordance with MD-882,
At a temperature of 20 ° C and a humidity of 60%, the pulling speed is 200mm
/ Min was used to calculate the elastic modulus from the chart obtained.

[Linear expansion coefficient of heat-resistant film] Measured in a tensile mode using a thermal analyzer (TMA-50; manufactured by Seiko Denshi Kogyo Co., Ltd.), and the average value at 20 to 300 ° C was taken as the linear expansion coefficient. . However, the measurement sample used was a heat-resistant film slit to a width of 3 mm, and the measurement conditions were as follows:
Measurement jig interval (measurement length) is 15mm, tensile load is 0
The adjustment was performed so as to be 1 g / mm ² .

[Heat-absorbing expansion coefficient of heat-resistant film] 50 ° C.
At a temperature of 40% RH and a sample length (L) of 80% R
The sample length (L ′) at the time of H was measured, and the following equation (A): hygroscopic expansion coefficient = {(L′−L)} (L)｝ ÷ (80% R
(H-40% RH) Using Equation (A), the coefficient of hygroscopic expansion of the heat-resistant film was calculated. After setting the humidity conditions, the sample was allowed to stand for 10 hours, and after confirming the saturated state of moisture absorption, the sample length under each humidity was measured.

[Dimensional change rate of copper-clad laminate] 21 cm × 2
1cm height, 1cm from outer edge (four corners) on 1cm copper clad laminate
1 cm inside, 4 points in total (clockwise from any one point)
A, B, C, and D) and drill holes with a diameter of 1 mm
It was a test piece. Test specimens are at a temperature of 20 ± 2 ° C and a humidity of 60 ± 5%
Leave for 24 hours in an RH environment, and use a coordinate measuring machine (AE1
12; manufactured by Mitoyo Seisakusho), A and B, C and D, A and D, B
And the distance between C and AB_Two, CD_Two, AD _Two,
BC_TwoAnd Next, add copper with a ferric chloride solution at 43 ± 5 ° C.
Copper foil on test specimen is completely removed by etching the foil
And dried at 40 ± 5 ° C. for 30 minutes.
It was left for 24 hours in an environment at a temperature of 60 ° C and a humidity of 60 ± 5% RH.
Then, the distance between the holes was measured again, and AB₁,
CD₁, AD₁, BC₁And And the following formula and formula
 ΔL_AB(%) = [(AB₁-AB_Two) ÷ AB_Two+ (CD₁-CD_Two) ÷ CD_Two] ÷ 2 × 100 (Formula) ΔL_AD(%) = [(AD₁−AD_Two) ÷ AD_Two+ (BC₁-BC_Two) ÷ BD_Two÷ 2 × 100 (Expression), the dimension change rate of the copper-clad laminate in the AB direction
ΔL which is the law change rate_AB, And the dimensional change rate in the AD direction
Some ΔL_ADWas calculated. The dimensional change after moisture absorption is as follows
It was calculated as follows. Copper foil of copper clad laminate in the same manner as above
Was completely removed and dried at 40 ± 5 ° C. for 30 minutes. Next
The temperature is 50 ℃ ± 3 ℃ and the humidity is 80RH ± 5RH%
Measure the interval between the holes of the sample left for 96 hours in the environment of
AB respectively₁’, CD₁’, AD₁’, BC₁’.
Then, the following equations 'and'_AB’(%) = [(AB₁'-AB_Two) ÷ AB_Two+ (CD₁’-CD_Two) ÷ CD_Two] ÷ 2 × 100 (expression) ΔL_AD’(%) = [(AD₁’-AD_Two) ÷ AD_Two+ (BC₁'-BC_Two) ÷ BD_TwoThe dimensional change rate of the copper-clad laminate after moisture absorption is expressed by AB
Is the dimensional change rate after moisture absorption_AB’And AD direction
ΔL which is the dimensional change rate after moisture absorption_AD'.

[Adhesive Strength of Copper-Clad Laminate] The measurement was performed using an autograph (AG2000A; manufactured by Shimadzu Corporation). The copper-clad laminate was partially etched, and a copper-clad laminate in which a copper pattern having a width of 5 mm and a length of 80 mm was formed on an adhesive film was used as a sample. The end of the copper pattern was peeled off from the interface between the heat-resistant film and the adhesive layer, and the end was fixed to a jig for measurement, and 180 ° with respect to the pattern.
At an angle of 50 mm / min, and the strength was measured.

[Production Example of Heat Resistant Film] Pyromellitic dianhydride / 4,4'-diaminobenzanilide / 4,4
4'-diaminodiphenyl ether in a molar ratio of 5/4 /
Polyamic acid was synthesized by polymerizing at a ratio of 1. 13% by weight DMA of polyamic acid under cooling in an ice bath
c / 100 g of solution, 8 g of acetic anhydride / pyridine /
A solution obtained by adding and stirring 2 g of the mixed solution was cast on a stainless steel endless belt as a support so that the thickness of the obtained film was 5 μm. The polyamic acid solution on the endless belt was heated at 110 ° C. for 4 minutes to obtain a gel film having self-supporting properties. The gel film was peeled off from the endless belt, and both ends parallel to the longitudinal direction of the film were fixed with tenter pins, and then passed through a tenter furnace at 150 ° C, 200 ° C, and 25 ° C.
Heating was performed stepwise at 0 ° C., 300 ° C., 350 ° C., and 450 ° C. for 1 minute each to obtain a long heat-resistant film. The resulting heat-resistant film had an elastic modulus of 10.8 GPa, a coefficient of linear expansion of 5 ppm, and a coefficient of hygroscopic expansion of 7 ppm.

[Example of preparation of resin solution for adhesive layer]
4,4'-biphenyltetracarboxylic dianhydride / 2,2
Polyamide acid is synthesized by polymerizing 2-bis ((4-aminophenoxyphenyl) propane at a molar ratio of 1/1, and a 23% by weight N, N-dimethylformamide solution as a resin solution for an adhesive layer. Was obtained.

Example 1 An adhesive resin solution was applied to one side of a 5 μm heat-resistant film obtained in the production example using a roll coater such that the thickness of the adhesive layer became 2.5 μm after drying and imidization. And dried at 100 ° C. for 4 minutes.
The other side was similarly coated with the adhesive resin solution and dried to obtain a film having an adhesive layer which was semi-dried on both sides. The resulting film was passed through a far-infrared furnace heated to an atmosphere temperature of 300 ° C. for 2 minutes, and a total thickness of 10 μm having a 2.5 μm adhesive layer on both sides of a 5 μm heat-resistant film was obtained.
Was obtained. 18 on both sides of this adhesive film
After rolling the rolled copper foil of μm, the copper-clad laminate was obtained by heating and compressing with a double belt press at a temperature of 290 ° C. and a linear pressure of 70 kg / cm for 3 minutes. Table 1 shows the adhesive strength and the dimensional change of the obtained copper-clad laminate.

(Embodiment 2) As in Embodiment 1, the thickness is 7.
An adhesive film having an adhesive layer of 4 μm on both sides of 5 μm Apical HP ((elastic modulus: 6.0 GPa, linear expansion coefficient: 11 ppm, moisture absorption expansion coefficient: 7 ppm); manufactured by Kaneka Corporation) was prepared. Subsequently, a copper-clad laminate was prepared, and the adhesive strength and the dimensional change were measured. The results are shown in Table 1.

Comparative Example 1 An adhesive film having a total thickness of 8 μm and having a 1.5 μm adhesive layer on both surfaces of a heat-resistant film having a thickness of 5 μm was prepared in the same manner as in Example 1.
Subsequently, a copper-clad laminate was prepared, and the adhesive strength and the dimensional change were measured. The results are shown in Table 1.

Comparative Example 2 An adhesive film having a total thickness of 19 μm and having a 7 μm adhesive layer on both surfaces of a heat-resistant film having a thickness of 5 μm was produced in the same manner as in Example 1. Subsequently, a copper-clad laminate was prepared, and the adhesive strength and the dimensional change were measured. The results are shown in Table 1.

[0025]

[Table 1]

[0026]

As described above, by setting the thickness of each of the heat-resistant film and the adhesive layer to a specific range, FPC, rigid-flex substrate material, COF and LOC packages are excellent in dimensional change rate and adhesive strength. And a thin adhesive film suitable for a new high-density packaging material such as MCM.

Continued on the front page (72) Inventor Kosuke Kataoka 2-4-64 Sakamoto, Otsu-shi, Shiga Prefecture (72) Inventor Hiroyuki Furuya 1-10-6-412, Kamitsumuro, Takatsuki-shi, Osaka F-term (reference) 4F100 AK01A AK46A AK49A AK49A AK49B AL05B AR00B AR00C EH462 EJ432 EJ862 GB43 JA02A JB16B JD15A JJ03 JJ03A JK07A JL04 JL11 JL11B JL11C YY00A YY00B YY00C 4J004 AA10 AA11 AA13 AA16 CC02 EA05 FA05 GA01

Claims (6)

[Claims] 1. An adhesive film having an adhesive layer having a thickness of 2 to 5 μm on one or both sides of a heat-resistant film having a thickness of 3 to 10 μm. 2. The heat-resistant film has a tensile modulus of 9-12.
GPa, linear expansion coefficient at 20 to 300 ° C is 1 to 10 pp
The adhesive film according to claim 1, wherein a coefficient of moisture expansion at 50 ° C is 1 to 10 ppm. 3. The heat-resistant film has the following formula: (Wherein, X ^{1 to} X ⁴ and Y ^{1 to} Y ⁴ each independently represent any one of a hydrogen atom, an alkyl group having 2 or less carbon atoms, and a halogen group) The adhesive film according to claim 1 or 2, wherein: 4. The adhesive film according to claim 1, wherein the heat-resistant film is made of a polyimide resin. 5. The adhesive layer according to claim 1, wherein said adhesive layer comprises a resin composition containing thermoplastic polyimide as a main component.
The adhesive film according to any one of the above. 6. A method for producing an adhesive film, comprising: (1) a step of applying a polyamic acid solution to the surface of a heat-resistant film and drying; and (2) a step of imidizing by heating in a far-infrared ray furnace. A method for producing an adhesive film according to claim 1.