JP2001191468A - Heat-resistant bonding sheet and copper clad laminated sheet using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-resistant bonding sheet having sufficient mechanical strength and excellent in solder heat resistance, adhesiveness, dimensional stability and low dielectric characteristics and a copper clad laminated sheet using this bonding sheet. SOLUTION: Polyamic acid being a precursor of thermoplastic polyimide is polymerized while an imidation ratio is adjusted to 10-90% to obtain polyimide which is, in turn, dissolved in an organic solvent and this solvent solution is applied to at least the single surface of a base film comprising a heat-resistant resin to obtain a heat-resistant bonding sheet. In this bonding sheet, the high adhesiveness of the base film and the thermoplastic polyimide interface can be especially realized. This bonding sheet is also excellent in heat resistance and solder heat resistance and can be especially used for a flexible copper clad laminated sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding sheet having a thermoplastic polyimide layer on at least one side of a base film and a copper-clad laminate comprising the same, and more particularly, to a heat resistance excellent in heat resistance, adhesion and dimensional characteristics. The present invention relates to a bonding sheet and a copper-clad laminate comprising the same.

[0002]

2. Description of the Related Art In recent years, higher performance and higher functionality of electronic devices have been developed.
The miniaturization is rapidly progressing, and there is an increasing demand for miniaturization and weight reduction of electronic components used in electronic devices. Along with this, the heat resistance, mechanical strength,
Various physical properties such as electrical characteristics are further required, and a higher density, higher function, and higher performance are also required for a semiconductor element packaging method and a wiring board for mounting the same. With regard to flexible printed wiring boards (hereinafter referred to as FPC), fine wire processing, multilayer formation, etc. are performed, and component mounting FPs in which components are mounted directly on the FPC.
C, a double-sided FPC in which a circuit is formed on both sides, a multilayer FPC in which a plurality of FPCs are stacked, and the layers are connected by wiring have appeared.

Generally, an FPC has a structure in which a circuit pattern is formed on a flexible and thin base film, and a surface cover layer is provided. In order to obtain the above-mentioned FPC, an insulating adhesive used as a material thereof is used. And the performance of insulating organic films must be improved. Specifically, it has high heat resistance and mechanical strength, and is excellent in workability, adhesiveness, low hygroscopicity, electrical characteristics, and dimensional stability.

At present, a film made of a polyimide resin having excellent characteristics is widely used as an insulating organic film for FPC. An epoxy resin or an acrylic resin that is excellent in low-temperature workability and workability is used as the insulating adhesive. However, it has been found that these adhesives are not particularly satisfactory in heat resistance. More specifically, when exposed to a temperature of 150 ° C. or more for a long time, these adhesives are deteriorated, which affects various characteristics. Furthermore, when using these adhesives, the adhesive is applied on a base film, dried, and then adhered to a conductor layer (generally, copper foil is used). Have to be heat-treated.

[0005] In particular, with the expanding use of FPCs, there is an urgent need to solve the problem of heat resistance. In order to solve this problem, a two-layer FPC having no adhesive layer and an FPC using a polyimide resin having excellent melt fluidity have been proposed. Regarding the two-layer FPC having no adhesive layer, a method in which a conductor layer is formed directly on an insulating film and a method in which an insulating layer is formed directly on a conductor layer are common. In the method of forming a conductor layer directly on an insulating layer, a method is used in which a thin layer of a conductor is formed by vapor deposition or sputtering, and then a thick layer of the conductor is formed by plating. There are problems that holes are easily generated and it is difficult to obtain a sufficient adhesive force between the insulating layer and the conductor layer.

On the other hand, in a method of forming an insulating layer directly on a conductor layer, a method of casting and drying a solution of a polyimide copolymer or a polyamic acid copolymer on the conductor layer and drying the same is used. In addition, the conductor layer is likely to be corroded by various solvents. Further, when a double-sided plate is manufactured, there is a problem that a complicated process is required such that two single-sided plates are manufactured and then these single-sided plates are adhered to each other.

[0007] FPCs using a polyimide resin having excellent melt fluidity are disclosed in Japanese Patent Application Laid-Open Nos.
No. 179224 or a bonding sheet having a thermoplastic polyimide layer on at least one surface of a base film made of a heat-resistant resin proposed in JP-A-5112768,
It has been difficult to achieve excellent adhesion, dimensional stability, solder heat resistance, and the like.

[0008]

As described above, the FPC having excellent heat resistance has problems in any form, but in consideration of productivity and characteristics, a base film made of a heat-resistant resin is required. It is considered that a method of bonding a copper foil and a bonding sheet obtained by laminating a thermoplastic polyimide on the substrate is most advantageous. Therefore, the above-mentioned problems relating to this case, that is, adhesiveness, dimensional characteristics, solder heat resistance, further low water absorption, low heat absorption, to provide a heat-resistant bonding sheet used for FPC excellent in low dielectric properties. As a result, the present invention has been achieved.

[0009]

The gist of the heat-resistant bonding sheet and the method of manufacturing the same according to the present invention is to dissolve a thermoplastic polyimide having an imidization ratio of 10% to 90% in an organic solvent, The present invention relates to a heat-resistant bonding sheet obtained by applying an organic solvent to at least one surface of a conductive base film and drying the organic solvent.

In such a thermoplastic polyimide, the precursor polyamic acid is represented by the general formula (1)

[0011]

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(Where k is an integer of 1 or more, and m and n are m
+ N is an integer of 0 or more, each of which is 1 or more.
A and B each represent a tetravalent organic group, and X and Y each represent a divalent organic group. ). Further, A and B in the general formula (1) represent the following group (I)

[0013]

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It is at least one kind of tetravalent organic group selected from the group consisting of: Further, X and Y in the general formula (1) represent the following group (II)

[0015]

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At least one divalent organic group selected from the group consisting of: Further, the base film made of the heat-resistant resin is a non-thermoplastic polyimide film or a thermoplastic polyimide film having a glass transition temperature of 350 ° C. or more.

[0017]

Embodiments of the present invention will be described below. First, a method for preparing a polyamic acid copolymer solution used as a thermoplastic polyimide layer in the present invention will be described.

The polyamic acid copolymer is obtained by reacting an acid dianhydride with a diamine in an organic solvent. For example, at first, at least in an inert gas atmosphere such as argon or nitrogen, A kind of acid dianhydride is dissolved or diffused in an organic solvent. At least one diamine compound is added to this solution in a solid state or an organic solvent solution state. Further, a mixture of one or more acid dianhydrides is added in a solid state or an organic solvent solution to obtain a polyamic acid solution which is a precursor of polyimide. In this reaction, contrary to the above addition procedure, a diamine solution may be prepared first, and a solid acid dianhydride or an organic solvent solution of acid dianhydride may be added to the solution. The reaction temperature at this time is preferably from -10C to 0C. The reaction time is 30 minutes to 3 hours. By this reaction, a polyamic acid solution which is a precursor of the thermoplastic polyimide is prepared.

Examples of the organic solvent used in the synthesis reaction of the polyamic acid include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N dimethylformamide and N, N diethylformamide, and N, N dimethyl Acetamide solvents such as acetamide and N, N diethylacetamide can be mentioned. These may be used alone or in combination of two or more. Further, a mixed solvent composed of these polar solvents and a non-solvent of polyamic acid can also be used. Examples of the non-solvent for the polyamic acid include acetone, methanol, ethanol, isopropanol, benzene, and methyl cellosolve.

The molecular weight of the polyamic acid copolymer and the polyimide copolymer is not particularly limited, but in order to maintain the strength as a heat resistant adhesive, the number average molecular weight is 50,000 or more, and It is preferably at least 80,000, particularly preferably at least 100,000. The molecular weight of the polyamic acid copolymer (solution) as an adhesive can be measured by GPC (gel permeation chromatography). Next, as a method for obtaining a polyimide from these polyamic acids, a method of thermally or chemically dehydrating a ring closure (imidization) may be used. Specifically, the method of thermally dehydrating ring closure (imidization) includes heating and drying under normal pressure or heating and drying a polyamic acid solution under reduced pressure.

When heating and drying at normal pressure, first, the organic solvent is evaporated at a temperature of 150.degree.
It is preferably performed for 0 minutes. Subsequently, this is dried by heating to imidize it. Heating temperature for imidization is 150 ° C
The range of -350 ° C is preferred. Especially the final heat treatment is 30
0 ° C. or higher is preferred. More preferably, 300 to 350
C is preferred.

When heating and drying under reduced pressure, solvent removal and imidization are performed simultaneously. The heating temperature is 150 ° C
The range of -200 ° C is preferred. In this method, since heating is performed under reduced pressure, water is easily removed from the system. Therefore, it is characterized in that the hydrolysis of the imide ring and the accompanying decrease in the molecular weight are less likely to occur as compared with the heating under normal pressure.

In the method of chemically dehydrating ring closure (imidization), a dehydrating agent having a stoichiometric amount or more and a tertiary amine as a catalyst are added to the above polyamic acid solution, and a method similar to the method of thermally dehydrating is used. Upon treatment, a desired polyimide film can be obtained in a shorter time than when thermally dehydrating.

As the tertiary amine used as a catalyst, pyridine, α-picoline, β-picoline, γ-picoline, trimethylamine, triethylamine, isoquinoline and the like are preferable.

Examples of the organic solvent for dissolving the obtained polyimide resin include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N, N dimethylformamide and N, N diethylformamide, and N, N dimethylacetamide. Acetamide solvents such as N, N diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone, tetrahydrofuran,
Examples thereof include ether solvents such as 1,4-dioxane and dioxolan. These may be used alone or in combination of two or more.

The imidization is carried out by the above-mentioned method, and it is necessary to appropriately set processing conditions such as temperature and time in order to adjust the imidization ratio to 10 to 90%. The imidation ratio is calculated from the following equation using an infrared absorption spectrometry. (A / B) × 100 / (C / D) Formula In the formula, A, B, C, and D represent the following. A: Absorption peak height of the target resin at 1780 cm ^-1 B: Absorption peak height of the target resin at 1500 cm ^-1 C: Absorption peak height of the chemically imidized polyimide at 1780 cm ^-1 D: 1500 cm ^{− of the} chemically imidized polyimide Absorption peak height of ¹ * Chemically imidized polyimide is a chemically imidized polyimide resin, and the imidation rate of the target resin is set with the imidation rate of this resin being 100%.

Next, the base film will be described.
Apical A is already on the market for base film
H, NPI and HP (Kanebuchi Chemical Industry Co., Ltd.) are preferably used. In addition, polyimides obtained from various combinations of acid dianhydrides and diamines can be used according to required characteristics.

By applying the above-mentioned thermoplastic polyimide solution to the base film, a bonding sheet having a desired structure can be obtained.

Although the embodiment of the heat-resistant bonding sheet according to the present invention has been described above, the present invention is not limited to this, and the present invention is based on the knowledge of those skilled in the art without departing from the spirit thereof. , Various improvements,
The present invention can be implemented in a form in which changes and modifications are made. The present invention will be described more specifically with reference to the above examples, but the present invention is not limited to these examples.

The copper-clad laminate of the present invention can be obtained by arranging a copper foil on at least one side of the heat-resistant bonding sheet by a press method or a laminating method.

[0031]

EXAMPLES Example 1 The whole system was cooled with ice water and placed in a 2000 ml three-neck separable flask purged with nitrogen.
3.1 g of 2,2'bis [4- (4-aminophenoxy) phenyl] propane (hereinafter, referred to as BAPP) was charged with 716.2 g of dimethylformamide (hereinafter, referred to as DMF) and stirred for 15 minutes. . Subsequently, 33.8 g of 3,3′4,4′benzophenonetetracarboxylic dianhydride (hereinafter referred to as “BTDA”) was added using 20 g of DMF. Subsequently, 76.
20 g of 0 g of 3,3'4,4'-ethylene glycol dibenzoate tetracarboxylic dianhydride (hereinafter referred to as TMEG).
And stirred for 30 minutes. After stirring for 30 minutes, a solution in which 4.1 g of TMEG was dissolved in 36.9 g of DMF was gradually added while paying attention to the viscosity of the solution in the flask.
% Polyamic acid solution was obtained. The obtained polyamic acid was dried under reduced pressure in a vacuum oven heated to 180 ° C. for 20 minutes to obtain a polyimide resin having an imidization ratio of 50%.

The obtained polyimide resin was mixed with N, N dimethylacetamide (hereinafter referred to as DMAc) at a solid concentration of 17%.
And dissolve in a polyimide film (Apical 12.5N
PI: manufactured by Kaneka Chemical Co., Ltd.), and a polyamic acid is applied so that the final one-side thickness of the thermoplastic polyimide layer is 6 μm, and then heated at 140 ° C. and 220 ° C. for 2 minutes each to remove the solvent. Then, a bonding sheet was obtained. 18 on the thermoplastic polyimide surface of the obtained bonding sheet
A rolled copper foil having a thickness of μm was overlaid, a polyimide film having a thickness of 25 μm was disposed thereon as a release film, and laminated with a double belt press (DBP) to obtain a copper-clad laminate. Laminating temperature is 280 ℃, pressure is 70kgf / c
m, and the lamination time was about 5 minutes. According to JIS C6481, the adhesive strength (kgf / c
m), solder heat resistance was measured according to JIS6471.
Table 1 shows the results. Solder heat resistance after normal condition adjustment (2
The measurement was carried out under two conditions: 0 ° C., 60% RH, after adjusting for 24 hours, immersion at 300 ° C. for 1 minute), and after moisture absorption (at 40 ° C., 90% RH, after adjusting for 96 hours, 280 ° C. for 10 seconds).
Table 1 shows the results.

(Example 2) Polyamic acid was polymerized in the same manner as in Example 1, and then dried under reduced pressure in a vacuum oven heated to 200 ° C for 20 minutes to obtain a polyimide resin having an imidization ratio of 60%. As in Example 1, a polyimide solution was applied to the base film and dried to obtain a bonding sheet. Subsequent production of CCL and measurement of physical properties were performed in the same manner as in Example 1. Table 1 shows the results.

(Example 3) The whole system was cooled with ice water and 8 ml was placed in a 2000 ml three-neck separable flask purged with nitrogen.
2.2 g of BAPP was charged using 650.0 g of DMF and 15
Stirred for minutes. Subsequently, 21.3 g of BTDA was introduced using 40 g of DMF. Subsequently, 71.5 g of 2,2′-bis (hydroxyphenyl) propanedibenzoatetetracarboxylic dianhydride (hereinafter referred to as ESDA) was added using 20 g of DMF, and the mixture was stirred for 30 minutes. After stirring for 30 minutes, a solution of 5.8 g of ESDA dissolved in 52.2 g of DMF was gradually added while paying attention to the viscosity of the solution in the flask.
Then, the mixture was left for 1 hour with stirring to obtain a polyamic acid solution of SC23%. Using the obtained polyamic acid solution, imidation and production of a bonding sheet were performed in the same manner as in Example 1. Preparation of CCL and measurement of physical properties were performed in the same manner as in Example 1. Table 1 shows the results.

(Comparative Example 1) Polyamic acid was polymerized in the same manner as in Example 1, and then dried under reduced pressure in a vacuum oven heated to 150 ° C for 5 minutes to obtain a polyimide resin having an imidation ratio of 8%. As in Example 1, a polyimide solution was applied to the base film and dried to obtain a bonding sheet. Then C
CL production and physical property measurement were performed in the same manner as in Example 1. Table 1 shows the results.

(Comparative Example 2) Polyamic acid was polymerized in the same manner as in Example 1, and then dried under reduced pressure in a vacuum oven heated to 200 ° C for 1 hour to obtain a polyimide resin having an imidization ratio of 95%. As in Example 1, a polyimide solution was applied to the base film and dried to obtain a bonding sheet. Subsequent production of CCL and measurement of physical properties were performed in the same manner as in Example 1. Table 1 shows the results.

[0037]

[Table 1]

[0038]

As described above, the bonding sheet according to the present invention is particularly excellent in heat resistance, the peel strength at the interface between the base film and the thermoplastic polyimide and between the thermoplastic polyimide and the copper foil, and the dimensional characteristics. It is suitable for new high-density packaging materials such as flex board materials, COF and LOC packages, and MCM, and other uses are not particularly limited.

Continued on the front page F-term (reference) 4F100 AB17D AB17E AB33D AB33E AK49A AK49B AK49C AT00B BA02 BA03 BA04 BA05 BA06 BA10A BA10C BA10D BA10E BA14 BA16 GB43 JA05B JB12B JB16B JJ03 JL04 JL11 YY1B0J04 CM04 EU04

Claims (5)

[Claims] 1. A heat-resistant bonding sheet obtained by dissolving a thermoplastic polyimide having an imidization ratio of 10% to 90% in an organic solvent, applying it to at least one surface of a heat-resistant base film, and drying the organic solvent. 2. A precursor of a thermoplastic polyimide is represented by the following general formula (1). (In the formula, k is an integer of 1 or more, m and n are each an integer of 0 or more where m + n is 1 or more. A and B are tetravalent organic groups, and X and Y are divalent organic groups. The heat-resistant bonding sheet according to claim 2, which is represented by the following formula: 3. A and B in the general formula (1) according to claim 2 are represented by the following group (I): The heat-resistant bonding sheet according to claim 2, wherein the heat-resistant bonding sheet is at least one kind of tetravalent organic group selected from the group consisting of: 4. The heat-resistant bonding film according to claim 1, wherein the heat-resistant base film is a non-thermoplastic polyimide film or a thermoplastic polyimide film having a glass transition temperature of 350 ° C. or more. Sheet. 5. A copper-clad laminate wherein a copper foil is disposed on at least one surface of the heat-resistant bonding sheet according to claim 1.