JPH08199124A - Bonding sheet - Google Patents

Abstract

PURPOSE: To prepare the subject sheet having an adhesive layer, comprising a specific aromatic polyimide copolymer, excellent in mechanical strength, heat resistance, processability and adhesion and capable of manifesting low water absorptivity and dielectric characteristics. CONSTITUTION: This sheet is obtained by forming an adhesive layer comprising an aromatic polyimide copolymer having recurring units of formulas I and II (Ar1 is a bivalent organic group; Ar2 is a tetravalent aromatic group; Ar3 is a bivalent aromatic group) so as to provide (50/50) to (99/1) molar fraction of the units I/II on one or both sides of a base film layer. The aromatic polyimide copolymer is preferably obtained by using 3,3',4,4'-ethylene glycol dibenzoate- tetracarboxylic dianhydride, etc., as an aromatic diester dianhydride, 3,3',4,4'- benzophenonetetracarboxylic dianhydride as an aromatic tetracarboxylic dianhydride and 2,2-bis[4-(4-amiophenoxy)phenyl]propane as an aromatic diamine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonding sheet, more specifically a flexible printed circuit board (hereinafter referred to as F
It is called a PC. ) Bonding with an aromatic polyimide copolymer adhesive layer, which has excellent heat resistance and adhesiveness and is particularly suitable as an adhesive film for use as a base film layer or semiconductor mounting material, and has low water absorption and low dielectric properties. Regarding the seat.

[0002]

2. Description of the Related Art In recent years, electronic devices have become more sophisticated, more sophisticated, and smaller in size, and electric parts used therewith are required to be smaller and lighter. Has been. Therefore, even higher density for the LSI packaging method and the wiring board on which they are mounted,
High-performance and high-performance products have been demanded. In order to meet this demand, fine line processing of FPC, multilayer molding, etc. have come to be performed, and a component mounting FPC in which components are directly mounted on the FPC and a double-sided FP with circuits formed on both sides
A high density FPC such as a C or a multi-layer FPC in which a plurality of FPCs are stacked and interconnected by wiring has appeared.

By the way, the FPC basically has a structure in which a circuit pattern is formed on a flexible and thin base film and a cover lay is applied to the surface thereof. In order to manufacture well, it is required to improve the performance of insulating adhesives and insulating organic films used as the materials.

At present, as an organic insulating material used as a base film or a coverlay film, a film made of a polyimide resin having high heat resistance and mechanical strength and having excellent electric characteristics is a base film for FPC. And is preferably used as a coverlay film.

However, the polyimide resin is almost insoluble and infusible in the closed ring state, and almost no application example is found as an adhesive. As an insulating adhesive, it is excellent in workability and workability at low temperature (180 ° C. or less). Therefore, epoxy resin or acrylic resin is often used. But,
These adhesives are inferior in properties such as heat resistance to polyimide, and for example, the adhesive deteriorates at high temperature (250 ° C. or higher), and the properties of polyimide used as a base film cannot be fully utilized. There was a problem. Furthermore, long-term post-cure is also required, and there has been a strong demand for higher performance adhesives for high-density mounting material applications as described above.

Therefore, in order to solve such a problem, an example in which a polyimide-based adhesive is used as an adhesive has recently been proposed. For example, Japanese Patent Laid-Open No. 2-1387
In 89, an adhesive film is obtained from a resin composition obtained by mixing poly (maleimide) and aromatic polyimide obtained from 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and aromatic diamine, and the adhesive film A method of manufacturing an FPC in which a base material such as a polyimide film and a copper foil are bonded using a film has been proposed. Further, in JP-A-5-179224 and JP-A-5-112768, various types of thermoplastic polyimide adhesives which can be pressed under heat and pressure have been proposed.

These polyimide-based adhesives are adhesives having excellent melt flowability, excellent adhesiveness when heated and pressed, and excellent heat resistance. They are polyimide films used as base films for FPCs. It has been attracting attention as an adhesive that can fully exhibit the above characteristics.

[0008]

However, although these polyimide-based adhesives have excellent melt fluidity and can be used as adhesives, these adhesives require high temperature and a long time for adhesion, There has been a problem that adhesion cannot be achieved unless heated to a high temperature of 300 ° C. or higher. Further, there is a problem that it easily absorbs moisture and the electric characteristics after absorbing moisture are poor.

Therefore, these adhesives are difficult to store in the state of polyimide and cannot be supplied as a film-like adhesive sheet, and to be used as an adhesive, the polyamic acid precursor which is its precursor is used. It was necessary to apply the solution of 1) to an insulating film serving as a base film or a coverlay film, dry it, and heat it to imidize it to form an adhesive layer.

In order to manufacture an FPC, the base film layer thus formed with an adhesive layer and a copper foil or the like are superposed and heat-pressed at 300 ° C. or higher to produce a copper-clad laminate, and thereafter. Circuit is formed by etching copper foil,
Although the coverlay film is pasted through several more steps, the adhesive layer absorbs moisture during the manufacturing process of the FPC, and as a result, the electrical characteristics of the adhesive layer deteriorate and the quality of the final product deteriorates. It could be the cause.

In particular, high density packaging materials such as LOC packages and MCMs, printed wiring board materials such as multilayer FPCs, and aerospace materials have high heat resistance and mechanical strength.
It is required to have excellent workability and adhesiveness, particularly low hygroscopicity, and also have various characteristics such as electrical characteristics and dimensional stability. Further, as described above, the step of forming the adhesive layer at the time of use is troublesome, and a method for further simplifying the production of the FPC or the like is required.

In view of such circumstances, the inventors of the present invention have solved the above-mentioned conventional problems and have sufficient heat resistance, processability and adhesiveness, and particularly low water absorption. The present invention has been accomplished as a result of extensive research aimed at providing a bonding sheet having an adhesive layer exhibiting high dielectric constant and low dielectric properties.

[0013]

A gist of a bonding sheet according to the present invention is that a base film layer and
General formula (1) formula 6 provided on both sides or one side

[Chemical 6] And the general formula (2) 7

[Chemical 7] (In the formulas (1) and (2), Ar ₁ represents a divalent organic group, Ar ₂ represents a tetravalent aromatic group, and Ar ₃ represents a divalent aromatic group.) Then, the repeating unit (1) or (2) has a molar fraction ([1] / [2]) in the range of 50/50 to 99/1 and an adhesive layer made of an aromatic polyimide copolymer. To be composed.

In the bonding sheet, Ar ₁ in the general formulas (1) and (2) is

Embedded image In is any of the divalent organic group represented, Ar ₂ is of 9

[Chemical 9] In a tetravalent aromatic group represented, Ar ₃ is of 10

[Chemical 10] It is a divalent aromatic group represented by.

[0015]

EXAMPLES The bonding sheet according to the present invention will be described below.

The bonding sheet of the present invention comprises a base film layer and a compound represented by the general formula (1):

[Chemical 11] And the general formula (2)

[Chemical 12] (In the formula, Ar ₁ is a divalent organic group, Ar ₂ is a tetravalent aromatic group,
Ar ₃ represents a divalent aromatic group. ), And the molar ratio ([1] / [2]) of the repeating units (1) and (2) is in the range of 50/50 to 99/1. And an adhesive layer made of a polymer.

The aromatic polyimide copolymer having the above structure used as the adhesive layer in the present invention has a low glass transition temperature and excellent adhesiveness at low temperature, low water absorption and excellent dielectric properties. Specifically, it can be obtained by the following method.

That is, in an atmosphere of an inert gas such as argon or nitrogen, the general formula (3) NH ₂ —Ar ₃ —H ₂ N (3) (in the formula, Ar ₃ represents a divalent aromatic group) The aromatic diamine represented by is dissolved or diffused in an organic solvent. In this solution, the compound of the general formula (4) 13

[Chemical 13] (Wherein Ar ₁ represents a divalent organic group) and an aromatic diester dianhydride represented by the general formula (5)

Embedded image (In the formula, Ar ₂ represents a tetravalent aromatic group), an aromatic tetracarboxylic acid dianhydride is added in the form of a solution or a slurry with a solid or an organic solvent, and -10 to 5
By reacting at 0 ° C, more preferably at -5 to 20 ° C for 30 minutes to 6 hours, a solution of an aromatic polyamic acid copolymer which is a precursor of the aromatic polyimide copolymer used in the present invention is obtained. be able to.

In such a reaction, the ratio of the acid dianhydride component can be arbitrarily selected, but the aromatic diester dianhydride represented by the general formula (4) and the general formula (5) It is preferable to use it so that the molar ratio of the aromatic tetracarboxylic acid dianhydride represented by (4) is in the range of 50:50 to 99: 1. This is because if the proportion of the aromatic diester dianhydride is less than 50%, the processing temperature, that is, the glass transition temperature becomes high, and if it is more than 99%, the polymer becomes poor in self-supporting property. The aromatic diamine represented by the general formula (3) is preferably used in an equimolar amount to the total amount of the acid dianhydride component.

In this reaction, contrary to the above, first, the acid dianhydride component represented by the general formula (4) and the general formula (5) is dissolved or diffused in an organic solvent,
A solution or slurry of a solid or organic solvent of the aromatic diamine represented by the general formula (3) may be added to the solution.

More specifically, as the aromatic diester dianhydride represented by the above-mentioned general formula (4) used in the present invention, aromatic diester dianhydrides having any structure can be used. Is Ar ₁ in the general formula (4) is

[Chemical 15] 2,2-bis (4-hydroxyphenyl) propanebenzoate-3,3 ', 4,4'-tetracarboxylic dianhydride (ESDA) or 3,3', 4,4 '-Ethylene glycol dibenzoate tetracarboxylic dianhydride (EG
It is preferred to use either DA) or 3,3 ', 4,4'-propylene glycol benzoate tetracarboxylic dianhydride (TMPG).

As the aromatic tetracarboxylic acid dianhydride represented by the general formula (5), aromatic tetracarboxylic acid dianhydrides having any structure can be used, but in particular, the general formula (5 Ar ₂ in 16)

Embedded image It is preferable to use 3,3 ′, 4,4′-benzophenone tetracarboxylic acid dianhydride (BTDA) represented by

As the aromatic diamine represented by the general formula (3), aromatic diamines having any structure can be used. In particular, Ar ₃ in the general formula (3) is

[Chemical 17] It is preferable to use 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP) represented by

Examples of the organic solvent used in the reaction for producing the aromatic polyamic acid copolymer solution include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide,
Examples thereof include formamide solvents such as N, N-diethylformamide and acetamide solvents such as N, N-dimethylacetamide and N, N-diethylacetamide. These may be used alone or as a mixed solvent of two or three or more. Further, these polar solvents can be used as a mixed solvent with a non-solvent of a polyamic acid copolymer such as acetone, methanol, ethanol, isopropanol and benzenemethylcellosolve.

By such a reaction, the above repeating units (1) and (2) used as the adhesive layer in the present invention are contained, and the molar ratio of the repeating units (1) and (2) ([1] /
A solution of an aromatic polyamic acid copolymer which is a precursor of the aromatic polyimide copolymer having [2]) in the range of 50/50 to 99/1 can be obtained.

Then, the polyamic acid copolymer solution is formed into a film and thermally and / or chemically dehydrated and cyclized (imidized) to form the aromatic polyimide copolymer used in the present invention. A film can be obtained.

Explaining by way of example, in the method of thermal dehydration ring closure, first, the solution of the aromatic polyamic acid copolymer is applied to a support plate, an organic film such as PET, or a support such as a drum or an endless belt. It is cast or coated on to form a film, and dried to obtain a film having self-supporting property. This drying is preferably carried out at a temperature of 150 ° C. or lower for about 5 to 90 minutes.

Then, this is further heated and dried to be imidized to obtain a film made of the aromatic polyimide copolymer having the repeating units (1) and (2).
The temperature during heating is preferably in the range of 150 to 350 ° C. There is no limitation on the rate of temperature increase during heating, but it is preferable that the maximum temperature reaches the above temperature by gradually heating. The heating time varies depending on the film thickness and the maximum temperature, but in general, it is preferably in the range of 10 seconds to 5 minutes after the maximum temperature is reached. When the film having the self-supporting property is heated, it is preferable to peel it off from the support, fix the ends in this state and heat it, because a polymer having a small linear thermal expansion coefficient can be obtained.

Further, in the method of chemically dehydrating and ring-closing, the same method as in the case of thermally dehydrating by adding a stoichiometric or more dehydrating agent and a catalytic amount of a tertiary amine to the solution of the polyamic acid copolymer is used. When treated by the method, the desired polyimide film can be obtained in a shorter time than when thermally dehydrated.

Comparing the thermal imidization method and the chemical imidization method, the chemical method is advantageous in that the obtained polyimide film has a large mechanical strength and a small coefficient of linear thermal expansion. There is. In addition, it is also possible to use the method of thermally imidizing and the method of chemically imidizing together.

The molecular weights of the polyamic acid copolymer and the polyimide copolymer are not particularly limited, but in order to maintain the strength of the obtained film, the number average molecular weight is 50,000 or more, and further, It is preferably 80,000 or more, particularly 100,000 or more, and more preferably 120,000 or more.

However, it is often difficult to directly measure the molecular weight of the polyimide copolymer, and in such a case, it is estimated by an indirect method. For example, when the polyimide copolymer is synthesized from the polyamic acid copolymer, the value corresponding to the molecular weight of the polyamic acid copolymer is the molecular weight of the polyimide copolymer.

The aromatic polyimide copolymer obtained as described above has a molar fraction ([1] / [2]) of repeating units represented by the above general formulas (1) and (2). But,
It is in the range of 50/50 to 99/1 and has excellent thermoplasticity, heat resistance, low-temperature adhesiveness, low water absorption, and low dielectric constant characteristics.

That is, the aromatic polyimide copolymer has excellent heat resistance, which is a characteristic of polyimide, and has a clear glass transition temperature between 100 ° C. and 250 ° C. depending on its composition, and has a glass transition temperature of 100 ° C. to 250 ° C. Excellent adhesion is exhibited by laminating at close temperature. Also,
These copolymers show low water absorption of 1% or less when immersed in pure water at 20 ° C. for 24 hours, and low dielectric constant of 3.0 or less at 1 MHz (normal state). .

Then, a film made of this aromatic polyimide copolymer is used as an adhesive layer, and the adhesive layer is laminated on both sides or one side of the base film and thermocompression bonded, whereby the bonding sheet of the present invention is easily obtained. be able to. The base film referred to in the present invention is FPC.
Any film can be used as long as it can be used as a base film for the above, but a polyimide film having excellent properties such as heat resistance is particularly preferably used. As the polyimide film used as the base film, for example, a polyimide film having no adhesiveness such as “Apical (registered trademark; polyimide film, manufactured by Kaneka Kagaku Kogyo Co., Ltd.)” can be used. It may be a film. The base film in the present invention also includes a thermoplastic film, and the bonding sheet of the present invention may be obtained by using a thermoplastic film having a different glass transition temperature as a base film.

As another method of obtaining the bonding sheet of the present invention, a solution of the polyamic acid copolymer, which is a precursor of the polyimide copolymer, is cast on a base film to imidize it and only one side thereof is cast. An adhesive layer may be formed, and then, a polyamic acid copolymer solution may be cast on the other surface of the base film to imidize it to form an adhesive layer on both surfaces. Further, the polyamic acid copolymer solution may be simultaneously cast on both sides of the base film to imidize it.

Alternatively, the imidized polyimide copolymer may be dissolved in a solvent such as DMF or NMP, and directly coated on both sides or one side of the base film and dried.

The bonding sheet of the present invention obtained by these methods has excellent thermoplasticity, heat resistance, low-temperature adhesiveness, low water absorption rate, low dielectric constant characteristics and mechanical strength, and has an adhesive layer. Since there is no fear of deterioration due to moisture absorption during storage, it can be supplied as such an adhesive sheet. Then, this bonding sheet can be relatively easily manufactured by superposing it on a copper foil or the like and laminating it at a low temperature so that a copper-clad laminate having excellent adhesiveness can be produced. In particular, by using a polyimide film as a base film to produce a bonding sheet made entirely of polyimide, it is possible to easily carry out a punching process by alkali etching, which is preferable.

Therefore, the bonding sheet of the present invention is F
It can be suitably used as a base film for PC. For example, a bonding sheet which is entirely made of polyimide has a copper foil laminated on both sides of the bonding sheet and thermocompression bonded to produce a double-sided copper-clad laminate. After the layer is etched to form the circuit, the bonding sheet is further alkali-etched, so that the through hole can be easily punched, and the double-sided FPC can be obtained relatively easily.

When a single-sided FPC is produced by using the bonding sheet of the present invention as a base film layer, an adhesive layer is formed on the other side of the base film layer where no circuit is formed. A multi-layer FPC can be easily obtained by punching through holes by alkali etching and laminating and laminating a plurality of single-sided FPCs.

Further, a bonding sheet made entirely of polyimide and a bonding sheet using a base film layer other than polyimide are arbitrarily combined, and a layer to be punched by alkali etching and a layer not to be punched are laminated. It is also possible to obtain a multilayer FPC having

As described above, the bonding sheet of the present invention can be suitably used as a double-sided FPC or multi-layer FPC material, and is also suitable for a rigid-flex substrate material, a new high-density mounting material such as LOC package, MCM and the like. Yes, other uses are not particularly limited.

Although the bonding sheet according to the present invention has been described above, the present invention is not limited to these examples and may be used not only as a base film but also as a cover lay film. Other,
The present invention can be carried out in various modes with various improvements, changes and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to these Examples. In the examples, DMF is N, N-dimethylformamide. Also, BAPP is 2,2-bis [4-
(4-aminophenoxy) phenyl] propane, and E
SDA is 2,2-bis (4-hydroxyphenyl) propanedibenzoate-3,3 ', 4,4'-tetracarboxylic dianhydride,
BTDA is 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride, EGDA is 3,3', 4,4'-ethylene glycol dibenzoate tetracarboxylic dianhydride, TMPG is 3,
It is 3 ', 4,4'-propylene glycol benzoate tetracarboxylic dianhydride.

Example 1 In a 500 ml three-neck separable flask (1) equipped with a stirrer, 16.4 g (40 mmol) of BAPP and 140.
0 g was added and stirred under a nitrogen atmosphere to sufficiently dissolve it. Next, 2.6 g (8 m) of BTDA was placed in a 50 ml eggplant flask (2).
mol) and 17.9 g (31 mmol) of ESDA were collected and added as a solid to the BAPP solution in the separable flask (1). The wall surface of the eggplant flask (2) is 5 g of DMF.
It was washed with and poured into a separable flask (1).
After standing for about 1 hour with stirring, 0.6 g (1 mmo
The solution obtained by dissolving 1) of ESDA in 5.0 g of DMF in a separable flask (1)
The varnish inside was gradually added while paying attention to the viscosity. After reaching the maximum viscosity, the addition of the ESDA solution was terminated to obtain a polyamic acid solution.

On the other hand, in a 100 ml volumetric flask (3), 10.0 g of isoquinoline, 10.0 g of acetic anhydride, DMF10.
0 g was stirred well. Then, the solution in the volumetric flask (3) was added to 100 g of the polyamic acid solution prepared above, and well stirred for 2 minutes to degas. This solution is PE
Apply on T film, heat at 80 ℃ for 25 minutes, PE
After peeling off the T film, the end was fixed and the temperature was continuously raised from 100 ° C. to 250 ° C., and after the temperature was raised, it was heated for 5 minutes to imidize to obtain a polyimide adhesive film.

The glass transition temperature (° C.), water absorption (%) and dielectric constant of the obtained polyimide adhesive film were examined. The glass transition temperature is measured by TMA,
Water absorption rate is 20 ° C according to ASTM D-570
The rate of change in weight after immersion in pure water was measured. The dielectric constant was measured by the Q meter method (normal state, 1 MHz).

Then, the polyimide adhesive film obtained above was overlaid on both sides of "Apical (registered trademark; polyimide film, manufactured by Kanegafuchi Chemical Industry Co., Ltd.)" and 240
The bonding sheet of the present invention was obtained by hot-pressing for 10 minutes at 20 ° C. and 20 kg / cm ² .

In order to examine the adhesive strength of the obtained bonding sheet, copper foil (35
μm thickness) and heat press for 1 hour at 240 ° C., 20 kg / cm ² to obtain a flexible double-sided copper clad laminate,
The peel strength (kg / cm) of the copper-clad laminate was measured according to JIS K6481. Table 1 shows the results.

[0050]

[Table 1]

Example 2 The ratio of BTDA and ESDA was 4.5 g (14 m) of BTDA.
mol) and 14.4 g (25 mmol) of ESDA,
The amount of DMF used to dissolve BAPP is 13
A polyamic acid solution was obtained in the same manner as in Example 1 except that the amount was changed to 4.0 g, and further a polyimide adhesive film was obtained. With respect to the obtained polyimide adhesive film, the glass transition temperature (° C.), the water absorption rate (%) and the dielectric constant were measured in the same manner as in Example 1.

A bonding sheet of the present invention was obtained in the same manner as in Example 1 except that this polyimide adhesive film was used. The peel strength (kg / cm) of the obtained bonding sheet was measured in the same manner as in Example 1. Table 1 shows the results.

Example 3 The ratio of BTDA to ESDA was 6.4 g (20 m) of BTDA.
mol) and 11.0 g (19 mmol) of ESDA,
The amount of DMF used to dissolve BAPP is 13
A polyamic acid solution was obtained in the same manner as in Example 1 except that the amount was changed to 4.0 g, and further a polyimide adhesive film was obtained. With respect to the obtained polyimide adhesive film, the glass transition temperature (° C.), the water absorption rate (%) and the dielectric constant were measured in the same manner as in Example 1.

A bonding sheet of the present invention was obtained in the same manner as in Example 1 except that this polyimide adhesive film was used. The peel strength (kg / cm) of the obtained bonding sheet was measured in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 1 For comparison, a bonding sheet having a thermoplastic polyimide polymer composed of BTDA and BAPP as an adhesive layer was obtained. Specifically, 16.4 g (40 mmol) of BAPP and 105.4 g of DMF were placed in a 500 ml three-neck separable flask (1) equipped with a stirrer, and stirred under a nitrogen atmosphere to sufficiently dissolve them. Next, BTDA1 is put in a 50 ml eggplant flask (2).
2.3 g (38 mmol) was taken and added as a solid to the BAPP solution in the separable flask (1). The wall surface of the eggplant flask (2) was washed with 5 g of DMF and poured into the separable flask (1). After standing for about 1 hour with stirring, 0.6 g (2 mmol) of BTDA was added to DMF.
The solution dissolved in 8.0 g was gradually added to the separable flask (1) while paying attention to the viscosity of the varnish in the separable flask (1). After reaching the maximum viscosity, BTDA
Then, the addition of the solution was completed to obtain a polyamic acid solution. Using this polyamic acid solution, a film was formed and imidized in the same manner as in Example 1 to obtain a polyimide adhesive film. With respect to the obtained polyimide adhesive film, the glass transition temperature (° C.), the water absorption rate (%) and the dielectric constant were measured in the same manner as in Example 1.

A bonding sheet of the present invention was obtained in the same manner as in Example 1 except that this polyimide adhesive film was used. The peel strength (kg / cm) of the obtained bonding sheet was measured in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2 For comparison, a bonding sheet using a thermoplastic polyimide copolymer having a reduced proportion of ESDA as an adhesive layer was obtained. Specifically, 16.4 g (40 mmol) of BAPP was placed in a 500 ml three-neck separable flask (1) equipped with a stirrer.
And 115.4 g of DMF were added, and the mixture was stirred under a nitrogen atmosphere to be sufficiently dissolved. Next, BTDA is put in a 50 ml eggplant flask (2).
10.3 g (32 mmol) and ESDA 4.0 g (7
mmol) and collect BAP of separable flask (1)
It was added as a solid in the P solution. The wall surface of the eggplant flask (2) was washed with 5 g of DMF and poured into the separable flask (1). After leaving it for about 1 hour while stirring,
A solution prepared by dissolving 6 g (1 mmol) of ESDA in 5.0 g of DMF was gradually added to the separable flask (1) while paying attention to the viscosity of the varnish in the separable flask (1). After reaching the maximum viscosity, the addition of the ESDA solution was terminated to obtain a polyamic acid solution. Using this polyamic acid solution, a film was formed and imidized in the same manner as in Example 1 to obtain a polyimide adhesive film. The glass transition temperature (° C.), water absorption rate (%) and dielectric constant of the obtained polyimide adhesive film were measured in the same manner as in Example 1.

A bonding sheet of the present invention was obtained in the same manner as in Example 1 except that this polyimide adhesive film was used. The peel strength (kg / cm) of the obtained bonding sheet was measured in the same manner as in Example 1. Table 1 shows the results.

Examples 4 to 6 Examples 1 to 3 except that EGDA was used instead of ESDA.
A polyamic acid copolymer solution was obtained in the same manner as in, and further a polyimide adhesive film was obtained. The specific amount of EGDA used in Examples 4 to 6 was 12.7 g (31 mmo).
l), 10.3 g (25 mmol), 7.8 g (19 m
mol). Further, the amount of DMF used for dissolving BAPP is appropriately changed according to the viscosity of the obtained polyamic acid copolymer solution, and in Example 4, 119.0.
g, 126.0 g in the fifth embodiment, and 114.g in the sixth embodiment.
0 g of DMF was used. With respect to each of the obtained polyimide adhesive films, the glass transition temperature (° C.), the water absorption rate (%) and the dielectric constant were measured in the same manner as in Example 1.

Then, using the above polyimide adhesive film, a bonding sheet of the present invention was obtained in the same manner as in Example 1, and the peel strength (kg / cm) of each bonding sheet was obtained in the same manner as in Example 1. Was measured. Table 2 shows the results.

[0061]

[Table 2]

Comparative Example 3 For comparison, a polyamic acid copolymer solution was obtained in the same manner as in Comparative Example 2 except that EGDA was used instead of ESDA, and a polyimide adhesive film with a reduced EGDA ratio was obtained. . The specific amount of EGDA used is 2.9.
g (7 mmol), and 110.0 g of DMF was used to dissolve BAPP. With respect to the obtained polyimide adhesive film, the glass transition temperature (° C.), the water absorption rate (%) and the dielectric constant were measured in the same manner as in Example 1.

Using this polyimide adhesive film, a bonding sheet was obtained in the same manner as in Example 1, and the peel strength (kg / cm) of the obtained bonding sheet was measured. These results are shown in Table 2 together with the results of Comparative Example 1.

Examples 7 to 9 Examples 1 to 3 except that TMPG was used instead of ESDA.
A polyamic acid copolymer solution was obtained in the same manner as in, and further a polyimide adhesive film was obtained. The specific amount of TMPG used in Examples 7 to 9 was 13.1 g (31 mmo).
l), 10.6 g (25 mmol), 8.1 g (19 m
mol). Further, the amount of DMF used for dissolving BAPP is appropriately changed according to the viscosity of the obtained polyamic acid copolymer solution, and in Example 7, 120.0
g, 118.0 g in Example 8 and 115.g in Example 9.
0 g of DMF was used. With respect to each of the obtained polyimide adhesive films, the glass transition temperature (° C.), the water absorption rate (%) and the dielectric constant were measured in the same manner as in Example 1.

Then, using the above-mentioned polyimide adhesive film, a bonding sheet of the present invention was obtained in the same manner as in Example 1, and the peel strength (kg / cm) of each bonding sheet was obtained in the same manner as in Example 1. Was measured. Table 3 shows the results.

[0066]

[Table 3]

Comparative Example 4 For comparison, a polyamic acid copolymer solution was obtained in the same manner as in Comparative Example 2 except that TMPG was used instead of ESDA to obtain a polyimide adhesive film having a reduced TMPG ratio. . The specific amount of TMPG used is 3.0
g (7 mmol), and 110.0 g of DMF was used to dissolve BAPP. With respect to the obtained polyimide adhesive film, the glass transition temperature (° C.), the water absorption rate (%) and the dielectric constant were measured in the same manner as in Example 1.

Using this polyimide adhesive film, a bonding sheet was obtained in the same manner as in Example 1, and the peel strength (kg / cm) of the obtained bonding sheet was measured. These results are shown in Table 3 together with the results of Comparative Example 1.

From Tables 1 to 3, BAP was used as the diamine component.
Using P, ESDA (or EGD as an acid dianhydride component)
A or TMPG) and BTDA are mixed, and the molar ratio of the dianhydride component ([ESDA (or EGDA, or TM
It can be seen that the polyimide adhesive film obtained by using PG)]: [BTDA]) at 50:50 to 99: 1 has a low glass transition temperature, low water absorption and low dielectric constant.

Further, the bonding sheet of the present invention exhibits excellent adhesiveness at low temperature, and a copper clad laminate can be easily produced by stacking copper foils and the like and laminating at low temperature (240 ° C.). I understand. It should be noted that the bonding sheet of the present invention exhibited excellent heat resistance and maintained excellent adhesiveness without deterioration of the adhesive layer even at high temperatures.

[0071]

INDUSTRIAL APPLICABILITY As described above, the bonding sheet of the present invention comprises the base film layer and the mole fractions of the repeating units represented by the general formulas (1) and (2) arranged on both sides or one side of the base film layer ( [1] / [2]) is 50/50 to 99 /
It is characterized by comprising an adhesive layer composed of an aromatic polyimide copolymer in the range of 1, and the aromatic polyimide copolymer exhibits low water absorption, and can be supplied as the bonding sheet of the present invention. And

Further, this aromatic polyimide copolymer has a low glass transition temperature, exhibits excellent adhesiveness when laminated at a temperature close to the glass transition temperature, and further exhibits low dielectric properties. Further, it has excellent heat resistance and maintains its excellent adhesiveness even at high temperatures. Therefore, the bonding sheet of the present invention using the aromatic polyimide copolymer as an adhesive can be suitably used as a base film for FPC or the like without causing deterioration of the adhesive layer in the FPC manufacturing process.

In particular, since a bonding sheet made entirely of polyimide can be easily punched by alkali etching, when an FPC is manufactured, copper foil is laminated on both sides of the bonding sheet and heat is applied. A double-sided FPC can be produced relatively easily by pressure-bonding to produce a copper-clad laminate, etching the copper-clad laminate to form a wiring pattern, and then punching a polyimide with alkali to make holes. it can. Similarly, it can be suitably used as a multilayer FPC material, and
Rigid-flex board material, LOC package, M
It is also suitable for new high-density packaging material applications such as CM.

That is, the bonding sheet of the present invention can realize excellent heat resistance, workability, and adhesiveness, and particularly as a base film having low hygroscopicity and low dielectric properties, double-sided FPC, multi-layer FPC, rigid-flex substrate material. ,
It can be suitably used for new high-density mounting material applications such as LOC packages and MCMs, and is expected to be widely used.

Claims (2)

[Claims] 1. A base film layer and a compound represented by the general formula (1), which is provided on both sides or one side of the base film layer. And the general formula (2): (In the formulas (1) and (2), Ar ₁ represents a divalent organic group, Ar ₂ represents a tetravalent aromatic group, and Ar ₃ represents a divalent aromatic group.) Then, the repeating unit (1) or (2) has a molar fraction ([1] / [2]) in the range of 50/50 to 99/1 and an adhesive layer made of an aromatic polyimide copolymer. A bonding sheet characterized by being configured. 2. In the general formula (1) and the general formula (2),
Ar ₁ is chemical 3 [chemical 3] Is one of the divalent organic groups represented by, and Ar ₂ is Ar ₃ is a tetravalent aromatic group represented by The bonding sheet according to claim 1, which is a divalent aromatic group represented by: