JP2000202966A - Heat-resistant bonding sheet and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-resistant bonding sheet excellent in heat resistance, adhesiveness, dimensional stability and low dielectric characteristics while having sufficient mechanical strength and a method for producing the same. SOLUTION: A heat-resistant bonding sheet can be obtained by applying a thermoplastic polyimide layer to at least the single surface of a heat-resistant base film as an adhesive layer to heat and dry the same. In this case, a heat treatment is performed under a condition of a temp. of 300 deg.C or higher and tension of 5 kgf/m or less by floating to make it possible to realize the adhesiveness with a copper foil, excellent soldering heat resistance and dimensional characteristics. This heat-resistant bonding sheet can be especially used in 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 method for producing the same.
The present invention relates to a heat-resistant bonding sheet having excellent heat resistance, adhesiveness, and dimensional characteristics, and a method for producing 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 a sufficient adhesive force between the insulating layer and the conductor layer cannot be obtained.

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.

Further, as for FPC using a polyimide resin having excellent melt fluidity, a base made of a heat-resistant resin proposed in JP-A-2-138789, JP-A-5-179224 and JP-A-5-112768 has been proposed. Although a bonding sheet having a thermoplastic polyimide layer on at least one side of the film is used, it has been difficult to realize adhesiveness, 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 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 provide a bonding sheet having a thermoplastic polyimide layer on at least one surface of a base film made of a heat-resistant resin. A final heat treatment is performed at a temperature of not less than 5 ° C. and a tension of not more than 5 kgf / m, and the adhesive strength with the copper foil is not more than 0.1.
A heat-resistant bonding sheet having a shrinkage of 0.2% or less when heated at 5 kgf / cm or more and 300 ° C. for 5 minutes.

More specifically, it is a heat-resistant bonding sheet obtained by performing a floating heat treatment in which the final heat treatment is performed at 300 ° C. or higher.

Further, the thermoplastic polyimide resin layer has the general formula (2)

[0012]

Embedded image Wherein m and n are equal to the mole fraction of each repeating unit in the polymer chain, m is in the range of about 0.000 to 0.95, and n is in the range of about 1.00 to about 0.05. Where the sum of m and n is equal to 1.00. A and B are tetravalent organic groups, and X is a divalent organic group. Further, A and B in the general formula (2) are

[0013]

Embedded image And at least two kinds selected from the group of tetravalent organic groups shown in (1).

Further, X and Y in the general formula (2)
But

[0015]

Embedded image At least one selected from the group of divalent organic groups shown in the above. 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.

According to another aspect of the present invention, in a bonding sheet having a thermoplastic polyimide layer on at least one surface of a base film made of a heat-resistant resin, the final heat treatment is performed at a temperature of 300 ° C. or more and 5 kgf / m 2.
It is performed under the following tension, and the adhesive strength with the copper foil is 0.5 kgf.
This is a method for producing a heat-resistant bonding sheet having a shrinkage factor of 0.2% or less when heated at 300 ° C. for 5 minutes or more.

More specifically, there is provided a method for manufacturing a heat-resistant bonding sheet, wherein the heat treatment is performed in a floating state.

Further, when the thermoplastic polyimide layer is represented by the general formula (1): ## STR1 ## where m and n are equal to the mole fraction of each repeating unit in the polymer chain, and m is from about 0.000 to about 0.95. Where n is in the range of about 1.0 to about 0.05, where m and n
Is equal to 1.00. A and B are tetravalent organic groups,
X and Y each represent a divalent organic group. ) Is a method for producing a heat-resistant bonding sheet.

Further, there is provided a method for producing a heat-resistant bonding sheet, wherein A and B in the general formula (1) are at least two kinds selected from the group of tetravalent organic groups shown in Chemical formula 2. .

Further, there is provided a method for producing a heat-resistant bonding sheet, wherein the base film made of a heat-resistant resin is a non-thermoplastic polyimide film or a thermoplastic polyimide film having a glass transition temperature of 350 ° C. or higher.

[0021]

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 can be obtained by reacting an acid dianhydride with a diamine in an organic solvent. In the present invention, first, in an atmosphere of an inert gas such as argon or nitrogen, general Equation (3)

[0023]

Embedded image (In the formula, C represents a tetravalent organic group.) At least one acid dianhydride is dissolved or diffused in an organic solvent. The general formula (4)

[0024]

Embedded image (In the formula, X represents a divalent organic group.) At least one kind of diamine is added in a solid state or an organic solvent solution state. Further, a mixture of one or more acid dianhydrides represented by the general formula (3) is added in a solid state or an organic solvent solution, and a polyamic acid solution as a polyimide precursor is added. obtain. 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. Reaction time is 30 minutes to 3
Time. By this reaction, an adhesive of a polyamic acid solution which is a precursor of the thermoplastic polyimide is prepared.

Examples of the organic solvent used in the polyamic acid synthesis reaction 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.

Although the molecular weight of the polyamic acid copolymer and the polyimide copolymer is not particularly limited, 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, in order to obtain a polyimide from the polyamic acid solution as a precursor, a method of thermally or chemically dehydrating a ring closure (imidization) may be used. Specifically, in the method of thermally dehydrating ring closure (imidization), a solution of the above polyamic acid is coated on a base film made of a heat-resistant resin to form a film, and the organic solvent is evaporated and dried to be self-supported. Get a body membrane. Furthermore, the evaporation of the organic solvent is 1
It is preferable to carry out at a temperature of 50 ° C. or less for about 5 minutes to 90 minutes. Next, it is heated and dried to imidize it. The heating temperature at the time of imidization is preferably in the range of 150 ° C to 350 ° C. Particularly, the final heat treatment is preferably performed at 300 ° C. or higher. More preferably, the temperature is 300 to 350 ° C. The heating time varies depending on the thickness and the maximum temperature, but is generally preferably in the range of 10 seconds to 10 minutes after the maximum temperature is reached. Further, at the time of this heat treatment, since the heat treatment temperature is higher than the Tg of the thermoplastic layer, a stress remains, so that it is preferable to perform the heat treatment without applying tension as much as possible. The tension is preferably 5 kgf / m or less. Furthermore, considering the film transportability, 2 kgf / m to 5 kgf
/ M is preferred. Further, a so-called floating method in which the film does not contact a roll or the like during the heat treatment is more preferable. This is because the heat treatment temperature is higher than the Tg of the thermoplastic layer, so that sticking of the thermoplastic layer occurs, the tension balance is lost, and the thermoplastic surface is adversely affected.

In the method of chemically dehydrating and cyclizing (imidizing), a dehydrating agent having a stoichiometric amount or more and a tertiary amine as a catalyst are added to the polyamic acid solution, and the method is performed in the same manner as in the case of thermally dehydrating. 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.

Next, a copper foil is laminated on one or both sides of the bonding sheet and thermocompression-bonded to obtain a copper-clad laminate.

The base film referred to in the present invention is FPC
Any film may be used as long as it can be used as a base film, but a polyimide film having excellent heat resistance is particularly preferably used. Specifically, as the polyimide film used as the base film, for example, a polyimide film having no adhesive property such as “Apical (registered trademark; manufactured by Kaneka Chemical Co., Ltd.)” can be used. It may be a polyimide film.

Although the embodiment of the heat-resistant bonding sheet according to the present invention has been described above, the present invention is not limited thereto, and the present invention is based on the knowledge of those skilled in the art without departing from the scope of the present invention. , 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.

[0033]

Example 1 The whole system was cooled with ice water and purged with nitrogen.
33.2 g of 3,3 g in a 000 ml three-neck separable flask
3′4,4′Benzophenonetetracarboxylic dianhydride (hereinafter referred to as “BTDA”), 287 g of dimethylformamide (hereinafter referred to as “DMF”) was taken and sufficiently dissolved by stirring using a stirrer. Subsequently, 43.1
g of 2,2′bis [4- (4-aminophenoxy) phenyl] propane (hereinafter referred to as “BAPP”) was charged using 20 g of DMF and reacted. After 15 minutes of stirring, 76.0 g of 3,3
3 ', 4,4'-Ethylene glycol dibenzoate tetracarboxylic dianhydride (hereinafter referred to as TMEG) was added to 150 g of DM.
It was thrown in using F. After stirring for 15 minutes, 80.0 g
Of BAPP was added and reacted using 150 g of DMF. 30
After stirring for minutes, an additional 4.1 g of TMEG was added to 47.2 g of DM
The solution dissolved in F was gradually added while paying attention to the viscosity of the solution in the flask, and then left for 1 hour with stirring. Thereafter, 106 g of DMF was charged and stirred to obtain a polyamic acid solution.

Next, this polyamic acid solution was applied on both sides of a base film 12.5 NPI (manufactured by Kaneka Chemical Co., Ltd.) so that the final thickness was 6.5 μm on one side, and 6 ° C. at 100 ° C.
After heating for 150 minutes at 150 ° C, 200 ° C, and 300 ° C,
After heating for a minute, a bonding sheet was obtained. The tension at the time of heating was 5 kgf / m. Rolled copper foil having a thickness of 18 μm is laminated on the adhesive layer surface (one or both surfaces) of the obtained bonding sheet, and a 25 μm-thick polyimide film is disposed thereon as a release film. Laminated. Laminating temperature 280 ° C, pressure 70
A copper-clad laminate was obtained by heating at kgf / cm for about 5 minutes. About the obtained copper clad laminate, JIS C64
81, the peel strength (kg / cm), and the solder heat resistance were measured according to JIS6471. The shrinkage of the bonding sheet after heating at 300 ° C. for 5 minutes was measured according to JIS6471. As a result, the peel strength was 1.5 kgf / c.
m. Solder heat resistance after normal condition adjustment (20 ° C, 60
% RH, after adjusting for 24 hours, soak at 300 ° C for 1 minute),
After absorbing moisture (40 ° C, 90% RH, after adjusting for 96 hours, 280
(Soaked at 10 ° C. for 10 seconds). The heat shrinkage of the bonding sheet is 0.2%
Met.

[0035]

Embodiment 2 Final heat treatment is performed at 150 ° C., 250 ° C., and 3
After producing a bonding sheet in the same manner as in Example 1 except that the temperature was changed to 50 ° C. for 6 minutes each, a copper-clad laminate was produced using DBP. The peel strength was 1.2 kgf / cm, and the solder heat resistance was good both in the normal state and after moisture absorption. Heat shrinkage was 0.2%.

[0036]

Embodiment 3 Final heat treatment is performed at 150 ° C., 250 ° C., and 3 ° C.
A bonding sheet was prepared in the same manner as in Example 1 except that the temperature was changed to 00 ° C. for 3 minutes, and then a copper-clad laminate was prepared using DBP. The peel strength was 0.8 kgf / cm, and the solder heat resistance was good both in the normal state and after moisture absorption. Heat shrinkage was 0.2%.

[0037]

Example 4 A bonding sheet was prepared in the same manner as in Example 1 except that the final heat treatment was performed at a tension of 2 kgf / m, and a copper-clad laminate was prepared using DBP. Peel strength is 1.2kgf / cm, solder heat resistance is normal,
It was good even after moisture absorption. Heat shrinkage was 0.1%.

[0038]

Example 5 A bonding sheet was prepared in the same manner as in Example 2 except that the final heat treatment was performed at a tension of 2 kgf / m, and a copper-clad laminate was prepared using DBP. The peel strength was 1.0 kgf / cm, and the solder heat resistance was good both in the normal state and after moisture absorption. Heat shrinkage was 0.1%.

[0039]

Example 6 A bonding sheet was prepared in the same manner as in Example 3 except that the final heat treatment was performed at a tension of 2 kgf / m, and a copper-clad laminate was prepared using DBP. The peel strength was 0.9 kgf / cm, and the solder heat resistance was good both in the normal state and after moisture absorption. Heat shrinkage was 0.1%.

[0040]

Comparative Example 1 A bonding sheet was prepared in the same manner as in Example 1 except that the final heat treatment was performed at 150 ° C. and 250 ° C. for 6 minutes each, and then a copper clad laminate was prepared using DBP. Peel strength is 0.4kgf / cm, solder heat resistance is
Both normal and after moisture absorption were good. Heat shrinkage was 0.2%.

[0041]

Comparative Example 2 A bonding sheet was prepared in the same manner as in Example 1 except that the tension of the final heat treatment was changed to 10 kgf / m, and a copper-clad laminate was prepared using DBP. The peel strength was 1.5 kgf / cm, the solder heat resistance was normal, the moisture absorption was good, and the heat shrinkage was 0.5%.

[0042]

Comparative Example 3 A bonding sheet was prepared in the same manner as in Example 1 except that the bonding sheet passed over several rolls during the final heat treatment, and a copper-clad laminate was prepared using DBP. did. Peel strength is 1.2kg
/ Cm, the solder heat resistance was normal, and some of them had blisters with moisture absorption. The heat shrinkage was 0.5%.

[0043]

As described above, the bonding sheet according to the present invention is particularly excellent in heat resistance, peel strength with copper foil, and dimensional characteristics, and is suitable for FPC, rigid-flex substrate materials, COL and LOC packages, MCM, etc. It is suitable for use in new high-density packaging materials, and other uses are not particularly limited.

Continued on the front page F term (reference) 4F100 AB01D AB17D AK49A AK49B AK49C AK49K AR00B BA03 BA04 BA06 BA07 BA16 BA26 EH462 EJ422 GB41 JA03 JA05B JB16A JB16C JJ03 JJ03B JK06 JL04 YY00

Claims (10)

[Claims] 1. A bonding sheet having a thermoplastic polyimide layer on at least one surface of a base film made of a heat-resistant resin, wherein a final heat treatment is performed at a temperature of 300 ° C. or more and a tension of 5 kgf / m or less to form a copper foil and A heat-resistant bonding sheet having an adhesive strength of 0.5 kgf / cm or more and a shrinkage rate of 0.2% or less when heated at 300 ° C. for 5 minutes. 2. A heat-resistant bonding sheet obtained by performing a floating heat treatment in which the final heat treatment is performed at 300 ° C. or higher. 3. The thermoplastic polyimide layer has the general formula (1): ## STR1 ## Wherein m, n is equal to the mole fraction of each repeating unit in the polymer chain, m ranges from about 0.000 to about 0.95, and n is from about 1.00 to about 0.05. Wherein the sum of m and n is equal to 1.00, wherein A and B are tetravalent organic groups, and X and Y are divalent organic groups. The heat-resistant bonding sheet as described. 4. A and B in the general formula (1) are 4. The heat-resistant bonding sheet according to claim 3, wherein the heat-resistant bonding sheet is at least two kinds selected from the group of tetravalent organic groups shown in (1). 5. The heat-resistant base 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 higher. Bonding sheet. 6. A bonding sheet having a thermoplastic polyimide layer on at least one surface of a base film made of a heat-resistant resin, wherein a final heat treatment is performed at a temperature of 300 ° C. or more and a tension of 5 kgf / m or less, and A method for producing a heat-resistant bonding sheet having an adhesive strength of 0.5 kgf / cm or more and a shrinkage rate of 0.2% or less when heated at 300 ° C. for 5 minutes. 7. The method according to claim 6, wherein the heat treatment is performed in a floating state. 8. The thermoplastic polyimide layer according to the general formula (1) wherein m and n are equal to the mole fraction of each repeating unit in the polymer chain, and m is from about 0.000 to about 0.95. And n is in the range of about 1.0 to about 0.05, provided that the sum of m and n is equal to 1.00, A and B are tetravalent organic groups, and X and Y are 2 The method for producing a heat-resistant bonding sheet according to claim 6, wherein the organic compound has a valency of an organic group. 9. The heat-resistant bonding sheet according to claim 8, wherein A and B in the general formula (1) are at least two kinds selected from the group of tetravalent organic groups shown in Chemical formula 2. Manufacturing method. 10. The heat-resistant base film according to claim 6, wherein 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 higher. Method for manufacturing a flexible bonding sheet.