JP2007091803A - Polyimide film and metal-clad laminate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide film which can suitably be used for electronic material uses such as flexible printed boards, base films for COF, and TAB tapes, has thickness-forming freedom and high adhesiveness, and to provide a flexible metal-clad laminate. <P>SOLUTION: This non-thermoplastic polyimide film is characterized in that an organic polar solvent absorption rate is 0.5 to 50%. When a clad layer is formed, an organic polar solvent having an absorption rate of 0.5 to 50% in the polyimide is intervened. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flexible metal-clad laminate that can be suitably used for electronic materials such as a flexible printed circuit board, a COF base film, and a TAB tape.

  In recent years, the demand for various printed circuit boards has increased with the reduction in weight, size and density of electronic products, and in particular, the demand for flexible laminates (also referred to as flexible printed wiring boards (FPC), etc.) has increased. ing. The flexible laminate has a structure in which a circuit made of a metal foil is formed on an insulating film.

  The flexible laminate is generally formed of various insulating materials, and a flexible insulating film is used as a substrate, and a metal foil is bonded to the surface of the substrate by heating and pressure bonding via various adhesive materials. Manufactured by. A polyimide film or the like is preferably used as the insulating film. As the adhesive material, a thermosetting adhesive such as epoxy or acrylic is generally used (FPC using these thermosetting adhesives is hereinafter also referred to as three-layer FPC).

  Thermosetting adhesives have the advantage that they can be bonded at relatively low temperatures. However, in the future, as required characteristics such as heat resistance, flexibility, and electrical reliability become stricter, it is considered that it is difficult to cope with three-layer FPC using a thermosetting adhesive. On the other hand, FPC (hereinafter also referred to as two-layer FPC) is proposed in which a metal layer is directly provided on an insulating film, an insulating layer is directly provided on a metal foil by coating, or a thermoplastic polyimide is used for an adhesive layer. Has been. This two-layer FPC has characteristics superior to those of the three-layer FPC, and demand is expected to increase in the future.

However, the method of providing the metal layer directly on the insulating film requires a special surface treatment because the adhesion between the metal layer and the insulating layer is low, and the method of providing the insulating layer directly on the metal foil by coating or the like does not provide sufficient bending characteristics. Even in the method using thermoplastic polyimide, since the adhesive force between the thermoplastic polyimide and the insulating layer is low, delamination is easy and it is difficult to ensure a sufficient adhesive force.
JP-A-5-129377 Japanese Patent Laid-Open No. 5-114777 WO2002 / 085616

  This invention is made | formed in view of said subject, The objective is to provide the polyimide film which can be used conveniently for a flexible printed circuit board etc. with a high freedom degree of thickness structure and high adhesiveness. .

As a result of intensive studies in view of the above problems, the present inventors have found that the polyimide film needs to have a high affinity for the solvent used in the process in order to improve the adhesion between the polyimide film and the clad layer. And found the present invention.
That is, this invention relates to the non-thermoplastic polyimide fill characterized by the absorption rate of an organic polar solvent being 5 to 50%.
Moreover, this invention relates to the said non-thermoplastic polyimide film characterized by the absorption rate of an organic polar solvent being 10 to 30%.
The present invention also relates to the non-thermoplastic polyimide film, wherein the organic polar solvent contains at least one aprotic polar solvent.
In the present invention, the aprotic polar solvent contains at least one selected from dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, tetrahydrofuran, 1,4-dioxane, dioxolane, methyl ethyl ketone, and methyl isobutyl ketone. It is related with the said non-thermoplastic polyimide film characterized by these.
Moreover, this invention relates to the said non-thermoplastic polyimide film characterized by the linear expansion coefficient of 100-200 degreeC being 5-20 ppm / degrees C.
The present invention also relates to the non-thermoplastic polyimide film, wherein the elastic modulus is 4 GPa or more.
The present invention also relates to a metal-clad laminate obtained by forming a clad layer and a metal layer on at least one surface of a polyimide film.
The present invention also relates to the metal-clad laminate, wherein the clad layer is polyimide.
The present invention also relates to the method for producing a metal-clad laminate, wherein an organic polar solvent having an absorptance of 5 to 50% is interposed when forming the cladding layer.
Moreover, this invention is a method of forming a clad layer by apply | coating a polyimide and / or polyamic-acid organic polar solvent solution, Comprising: The organic polar solvent of this solution is 5 to 50% with respect to a polyimide film. It is related with the manufacturing method of the said metal-clad laminated board characterized by the above-mentioned.
Moreover, this invention is a method of forming a clad layer by laminating a polyimide and / or polyamic acid film, and the film contains 3 to 50% of an organic polar solvent having an absorptance of 5 to 50% with respect to the polyimide film. It is related with the manufacturing method of the said metal-clad laminated board characterized by the above-mentioned.

  According to the present invention, it is possible to provide a polyimide film and a metal-clad laminate that have excellent long-term adhesion reliability and are suitable for high-density mounting wiring boards such as COF, TAB, and FPC.

One embodiment of the present invention will be described below.
The polyimide film of the present invention is produced using polyamic acid as a precursor. Any known method can be used as a method for producing the polyamic acid. Usually, the polyamic acid obtained by dissolving a substantially equimolar amount of an aromatic dianhydride and an aromatic diamine in an organic solvent is obtained. The organic solvent solution is produced by stirring under controlled temperature conditions until the polymerization of the acid dianhydride and the diamine is completed. These polyamic acid solutions are usually obtained at a concentration of 5 to 35 wt%, preferably 10 to 30 wt%. When the concentration is in this range, an appropriate molecular weight and solution viscosity are obtained.

As the polymerization method, any known method and a combination thereof can be used. The characteristic of the polymerization method in the polymerization of polyamic acid is the order of addition of the monomers, and the physical properties of the polyimide obtained can be controlled by controlling the order of addition of the monomers. Therefore, in the present invention, any method of adding monomers may be used for the polymerization of polyamic acid. The following method is mentioned as a typical polymerization method. That is,
1) A method in which an aromatic diamine is dissolved in an organic polar solvent and this is reacted with a substantially equimolar amount of an aromatic tetracarboxylic dianhydride for polymerization.
2) An aromatic tetracarboxylic dianhydride is reacted with a small molar amount of an aromatic diamine compound in an organic polar solvent to obtain a prepolymer having acid anhydride groups at both ends. Then, the method of superposing | polymerizing using an aromatic diamine compound so that an aromatic tetracarboxylic dianhydride and an aromatic diamine compound may become substantially equimolar in all the processes.
3) An aromatic tetracarboxylic dianhydride and an excess molar amount of the aromatic diamine compound are reacted in an organic polar solvent to obtain a prepolymer having amino groups at both ends. Subsequently, after adding an aromatic diamine compound here, using the aromatic tetracarboxylic dianhydride so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar in all steps. How to polymerize.
4) A method in which an aromatic tetracarboxylic dianhydride is dissolved and / or dispersed in an organic polar solvent and then polymerized using an aromatic diamine compound so as to be substantially equimolar.
5) A method in which a substantially equimolar mixture of aromatic tetracarboxylic dianhydride and aromatic diamine is reacted in an organic polar solvent for polymerization.

  And so on. These methods may be used singly or in combination.

As a method of increasing the absorption rate of the organic polar solvent,
(I) A diamine having a flexible structure is used in an amount of 30 to 70 mol%, preferably 35 to 60 mol% of the total diamine component. (II) A diamine having a molecular weight of 250 or more, preferably 300 or more, particularly preferably 400 or more. 10-40 mol% of total diamine, preferably 15-35 mol%
(III) 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 4,4′-oxydiphthalic anhydride, molecule (IV) Flexible diamine using 10 to 50 mol%, preferably 15 to 40 mol% of acid dianhydride having a bending structure such as acid dianhydride having an ester machine in the inside thereof And (V) a monomer having a side chain that forms a block component with an acid dianhydride having a bent structure. These can be used in combination, but the absorption rate of the organic polar solvent is 0.5. In order to make it 50%, trial and error may be required by combining the above indicators within the range of common knowledge of those skilled in the art.

  Examples that can be preferably used as the main component of the flexible diamine include 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfide, 3,3′-diaminodiphenylsulfone, 4, 4'-diaminodiphenyl sulfone, 4,4'-oxydianiline, 3,3'-oxydianiline, 3,4'-oxydianiline, 4,4'-diaminodiphenyldiethylsilane, 4,4'-diamino Diphenylsilane, 4,4′-diaminodiphenylethylphosphine oxide, 4,4′-diaminodiphenyl N-methylamine, 4,4′-diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine) Bis {4- (4-aminophenoxy) phenyl} sulfone, bi {4- (3-aminophenoxy) phenyl} sulfone, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 1,3-bis (3-amino Phenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 3,3′-diaminobenzophenone 4,4′-diaminobenzophenone, 2,2-bis (4-aminophenoxyphenyl) propane and the like, and these can be used alone or in combination. These examples are examples that are suitably used as the main component, and any diamine can be used as the accessory component. Examples of diamines that can be particularly preferably used among these are 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-bis (3-aminophenoxy) biphenyl, 1,3-bis (3-amino). Phenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 2,2-bis (4 -Aminophenoxyphenyl) propane and the like.

  In order to obtain non-thermoplastic polyimide, it is preferable to use a rigid component such as paraphenylenediamine and its derivative, benzidine and its derivative as the main component. By using these diamines having a rigid structure, it becomes non-thermoplastic and it is easy to achieve a high elastic modulus. Moreover, it is preferable to use pyromellitic dianhydride as a main component as an acid component. As is well known, pyromellitic dianhydride tends to give a non-thermoplastic polyimide because of its rigid structure. In this way, molecular design is performed so that the finally obtained polyimide film is non-thermoplastic. However, if there is too much diamine having a rigid structure, the absorption rate of the organic polar solvent tends to decrease. Therefore, it is preferably 70 mol% or less, preferably 60 mol% or less.

  In addition, determination of whether the polyimide film obtained is non-thermoplastic is performed as follows. When the polyimide film is fixed to a metal fixed frame and heated at 450 ° C. for 1 minute, the one that retains the original film shape (no tarmi, no melting, etc.) is made non-thermoplastic.

The linear expansion coefficient of the non-thermoplastic polyimide film of the present invention is preferably 5 to 20 ppm / ° C, particularly 10 to 20 ppm / ° C. The hygroscopic expansion coefficient is preferably 15 ppm or less, particularly 13 ppm. If the linear expansion coefficient and the hygroscopic expansion coefficient are out of this range, the dimensional stability tends to deteriorate.
Furthermore, the elastic modulus is preferably 4 GPa or more. If the elastic modulus is below this range, the productivity at the time of producing the metal-clad laminate tends to be poor.

  The absorption rate of the organic polar solvent is 5 to 50%, preferably 10 to 30%. When the absorptance is below this range, the adhesion strength tends to decrease, and when it exceeds, the film strength decreases during the process and the yield tends to decrease.

  As a preferred solvent for synthesizing a polyimide precursor (hereinafter referred to as polyamic acid), any solvent that dissolves polyamic acid can be used, but amide solvents, that is, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone and the like, and N, N-dimethylformamide and N, N-dimethylacetamide can be particularly preferably used.

  In addition, a filler can be added for the purpose of improving various film properties such as slidability, thermal conductivity, conductivity, corona resistance, and loop stiffness. Any filler may be used, but preferred examples include silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica and the like. Any known method may be used for the addition.

  A conventionally well-known method can be used about the method of manufacturing a polyimide film from these polyamic acid solutions.

  At this time, it is preferable to finally heat at a temperature of 400 to 650 ° C. for 5 to 400 seconds. Above this temperature and / or for a long time, the film may suffer from thermal degradation and may cause problems. Conversely, if the temperature is lower than this temperature and / or the time is shorter, the predetermined effect may not be exhibited.

  Moreover, in order to relieve the internal stress remaining in the film, heat treatment can be performed under the minimum tension necessary for transporting the film. This heat treatment may be performed in the film manufacturing process, or may be provided separately. The heating conditions vary depending on the characteristics of the film and the apparatus used, and therefore cannot be determined in general. The internal stress can be relaxed by heat treatment at a temperature of 450 ° C. or lower for 1 to 300 seconds, preferably 2 to 250 seconds, particularly preferably 5 to 200 seconds.

Any resin may be used for the clad layer of the present invention, but from the viewpoint of heat resistance, polyimide, polyamideimide, acrylic resin, epoxy resin, phenol resin, etc. may be mentioned. It is preferable to use it.
When a clad layer is formed on a polyimide film, a clad resin and / or clad resin precursor solution using an organic polar solvent having an absorptivity of 5 to 50% as a solvent is applied, and dried and cured as necessary. That's fine. Furthermore, in order to laminate | stack a metal layer, metal foil etc. can be laminated | stacked using well-known methods, such as roll lamination and a double belt press. When the clad layer is a thermoplastic resin, it is preferable to form the clad layer by this method.

Alternatively, the clad resin and / or clad resin precursor solution may be applied to a metal foil or the like and dried, and then the metal foil may be laminated to a polyimide film. In this case, the clad layer on the metal foil needs to contain 3 to 50 wt%, preferably 5 to 40 wt%, of an organic polar solvent having an absorption rate of 3 to 50 wt% with respect to the polyimide film. At this time, the laminating temperature is 80 to 150 ° C, more preferably 80 to 120 ° C. When the temperature is below this range, the adhesion is too low, and when the temperature is above, the tendency to foam and become a defect increases. In this method, if necessary, post-curing may be performed to completely remove the solvent and cure. In this case, it is preferable to carry out in an inert gas atmosphere so that the metal foil is not oxidized.
This method is suitably used when the cladding layer is a non-thermoplastic resin.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited only to these Examples.

(Elastic modulus)
The elastic modulus was measured according to ASTM D882.

(Linear expansion coefficient)
The linear expansion coefficient at 50 to 200 ° C. was measured by using a TMA120C manufactured by Seiko Electronics Co., Ltd. (sample size: 3 mm width, 10 mm length), and once increased from 10 ° C. to 400 ° C. at 10 ° C./min with a load of 3 g. After heating, the temperature was cooled to 10 ° C., the temperature was further increased at 10 ° C./min, and the average value was calculated from the thermal expansion coefficients at 50 ° C. and 200 ° C. during the second temperature increase.

(Adhesion evaluation)
According to JIS C-6471, a metal pattern of 1 mm was evaluated at 90 degrees peel.

(Solvent Absorption Rate)
The film was cut into 5 × 10 cm, dried at 150 ° C. for 30 minutes, and then quickly weighed to obtain an initial weight. After immersing this film in a solvent at 23 ° C. for 1 hour, the droplets were wiped off, the weight after solvent absorption was measured, and the solvent absorption rate was calculated according to the following formula.
{(Weight after solvent absorption) − (initial weight)} / (initial weight) × 100
(Reference Example 1)
Dissolve 3,4'-oxydianiline in dimethylformamide (DMF), add 4,4'-oxydiphthalic anhydride (ODPA) so that it is almost equimolar as a powder, polyamic acid solution (Solid content concentration 18%, viscosity 1800 poise). This solution was diluted with DMF until the solid concentration became 8% to obtain a clad layer solution.

(Reference Example 2)
A clad layer solution was obtained in the same manner as in Reference Example 1 except that methyl cellosolve was used as a solvent.

Example 1
N, N-dimethylformamide (DMF) 2,2-bis (4-aminophenoxyphenyl) propane (BAPP) cooled to 10 ° C. was dissolved. 3,3 ', 4,4,'-biphenyltetracarboxylic dianhydride (BPDA) was added and dissolved, and then pyromellitic dianhydride (PMDA) was added and stirred for 30 minutes to prepare a prepolymer solution. Got.
After p-phenylenediamine (p-PDA) was dissolved in this solution, PMDA was added and stirred for 1 hour to dissolve. Further, a 7 wt% DMF solution of PMDA prepared separately was carefully added to this solution, and the addition was stopped when the viscosity reached about 3000 poise. Stirring was performed for 1 hour to obtain a polyamic acid solution having a solid content of about 19% by weight and a rotational viscosity at 23 ° C. of 3400 poise. (BAPP / BPDA / PMDA / p-PDA / PMDA = 40/20/16/60/64 (molar ratio))
To 100 g of this polyamic acid solution, 50 g of a curing agent composed of acetic anhydride / isoquinoline / DMF (weight ratio 18.90 / 7.17 / 18.93) was added, and the mixture was stirred and degassed at a temperature of 0 ° C. or less. Using a coater, it was cast on aluminum foil. This resin film is heated at 130 ° C. for 150 seconds, and then the self-supporting gel film is peeled off from the aluminum foil (volatile content 45% by weight) and fixed to a metal frame, 300 ° C. × 20 seconds, 450 ° C. × 20 Second, it was dried and imidized at 500 ° C. for 20 seconds to obtain a polyimide film having a thickness of 38 μm.
The clad layer solution obtained in Reference Example 1 was applied to both surfaces of this film and dried at 120 ° C. for 1 minute. Thereafter, imidization was performed at 360 ° C. for 20 seconds to obtain a composite sheet. A rolled copper foil (BHY-22B-T manufactured by Japan Energy) having a thickness of 18 μm was laminated on both surfaces of this composite sheet at 380 ° C. and 3 t / m by a hot roll laminating method to obtain a copper clad laminate (FCCL).
Table 1 shows the characteristics of the polyimide film and FCCL.

(Example 2)
A polyimide film and FCCL were obtained in the same manner as in Example 1 except that polymerization was performed at a molar ratio of BAPP / ODA / BTDA / PMDA / PDA = 30/20/20/100/50. These characteristics are shown in Table 1.

(Comparative Examples 1 and 2)
FCCL was obtained in exactly the same manner as in Examples 1 and 2, except that the clad layer solution obtained in Reference Example 2 was used. Table 2 shows the characteristics of this FCCL.

Claims (10)

A non-thermoplastic polyimide film, wherein the organic polar solvent has an absorptance of 5 to 50%. The non-thermoplastic polyimide film according to claim 1, wherein the organic polar solvent has an absorptance of 10 to 30%. 3. The non-thermoplastic polyimide film according to claim 1, wherein the organic polar solvent contains at least one aprotic polar solvent. The aprotic polar solvent contains at least one selected from dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, tetrahydrofuran, 1,4-dioxane, dioxolane, methyl ethyl ketone, and methyl isobutyl ketone. Item 4. A non-thermoplastic polyimide film according to Item 3. The non-thermoplastic polyimide film according to claim 1, wherein the linear expansion coefficient at 100 to 200 ° C. is 5 to 20 ppm / ° C. The non-thermoplastic polyimide film according to claim 1, wherein the elastic modulus is 4 GPa or more. A metal-clad laminate comprising a clad layer and a metal layer formed on at least one surface of the polyimide film according to claim 1. The metal-clad laminate according to claim 7, wherein the clad layer is polyimide. 9. The method for producing a metal-clad laminate according to claim 7, wherein an organic polar solvent having an absorptivity of 5 to 50% for the polyimide film is interposed when forming the clad layer. A method of forming a clad layer by applying a polyimide and / or polyamic acid organic polar solvent solution, wherein the organic polar solvent of the solution has an absorptivity of 5 to 50% with respect to the polyimide film. A method for producing a metal-clad laminate according to claim 9.