JP2003138039A - Polyimide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide film without generating elongation, bending and curling at a processing process on a TAB tape and a flexible print substrate. SOLUTION: The polyimide film comprising at least a polyimide resin component and a mica-based inorganic filler wherein the tensile elastic modulus is not less than 4 GPa, the average linear expansion coefficient from 100 deg.C to 200 deg.C is 18-28 ppm and the hygroscopic expansion coefficient is not more than 15 ppm can be used suitably as a base film without generating elongation, bending and curling at a processing process on a TAB tape and a flexible print substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide film which has been widely used as an insulating material with the weight and size reduction of various electronic devices. Among various uses of a polyimide film, the present invention relates to a flexible printed circuit board, in particular, a polyimide film as a base film used in a TAB (Tape Automated Bonding) system.

[0002]

2. Description of the Related Art Conventionally, a flexible printed wiring board (hereinafter referred to as an FPC) has been used mainly by being folded into a narrow space inside a camera, taking advantage of its flexibility. However, in recent years, it has come to be used in drive units of FD drives, hard disk drives, copiers, printers, etc., and there is a demand for further improvement in sliding and bending characteristics. In order to increase the flexibility of the base film, a film made of a polyimide having a high flexibility in terms of chemical structure may be used. Generally, a polyimide having a high flexibility has a large linear expansion coefficient. The flexible printed circuit board used as above has a drawback that it is apt to warp or curl. On the contrary, when a polyimide having a small coefficient of linear expansion is selected, the flexibility of the film itself is lost and it becomes very fragile, and the flexibility of the obtained FPC is also reduced. As a technology that can support device multi-pinning, downsizing, and high-density mounting, a hole (device hole) for mounting a semiconductor chip such as LSI is provided on a long insulating film, and a very thin copper film is formed on the hole. The TAB technique of forming a foil lead and connecting the LSI or the like to a printed wiring board or the like via the lead is drawing attention. In such a TAB technique, a protective layer, an adhesive layer, and an organic insulating film layer (base film layer) are generally used.
FC tape with a three-layer structure of
The processing steps until the LSI is mounted on the TAB tape obtained by processing the tape are performed as follows. That is,
The processing steps of the TAB tape include a step of forming sprocket holes and device holes by punching, a step of curing the adhesive after removing the protective layer and laminating a copper foil, an arrangement pattern forming step (resist coating, copper etching, The resist is peeled off), the plating process, the inner lead bonding process, the resin sealing process, the punching process, and the outer lead bonding process, and the LSI is mounted through the above processing steps. When mounting the LSI on the TAB tape,
From the punching process to the plating process, tension is applied. For this reason, when the elastic modulus of the base film is low, it is difficult to draw a circuit having a precise pattern because the base film easily stretches. Further, heat is applied in the processing steps of copper foil laminating, adhesive curing, inner lead bonding, resin encapsulation, and outer lead bonding, so that a large coefficient of linear expansion of the base film of the TAB tape causes inconvenience. For example, in the processing step of inner lead bonding, the thermal expansion of the base film causes a shift in the bonding position with the LSI. Similarly, in the outer lead bonding processing step, a displacement occurs in the bonding position between the outer lead and the substrate. The deviation of these joining positions causes a decrease in reliability. Further, in the process of copper foil laminating, since it is heated together with the copper foil, it exhibits curling behavior different from that of the copper foil, that is, a coefficient of linear expansion different from that of the copper foil causes curling. Curl or TAB
When the warp of the tape occurs, there is a problem in that the electrical connection part of the bonding is distorted and the electrical reliability of the circuit deteriorates. Also, when the water absorption of the base film is large, in the processing step of copper foil laminating,
Immediately after the curing reaction of the adhesive is completed and the base film is dried immediately after being taken out from the heating furnace for curing, it is fixed to the copper foil without distortion, but if this copper foil is left in a laminated state, Due to the nature of the base film, it absorbs and expands over time. However, copper foil does not swell due to moisture absorption, and because it has higher rigidity than the film and does not cause dimensional changes due to the expansion of the film, the internal stress in the adhesive layer sandwiched between the copper foil and the film Will be accumulated.
Therefore, if the placement pattern forming process is performed in this state, drying and moisture absorption will be repeated, and when the wiring pattern is formed on the copper foil by etching, the stress in the portion where the copper foil is removed is released and the dimensional change occurs. Occurs, a pattern larger than the photomask size for forming the wiring pattern is formed, and warpage or curling occurs. As a result, a defective connection with a semiconductor device occurs, and such a dimensional change causes a reduction in yield in the TAB processing step.

In order to prevent the above inconvenience from occurring, specifically, in the TAB tape processing step, in the inner lead bonding processing step, LS is used.
I (silicon wafer) and the base film must have a linear expansion coefficient close to each other, and in the process of outer lead bonding, the substrate to be joined and the base film have a similar linear expansion coefficient. In the processing step of coating, it is required that the copper foil and the base film have similar linear expansion coefficients. Also, in the process of manufacturing a flexible printed circuit board, similar to the process of processing a TAB tape, a process of laminating a copper foil, a process of forming a wiring pattern, etc. are included, and various characteristics such as a linear expansion coefficient and a water absorption rate of the film are obtained. It may cause curling. Further, if the elastic modulus is small, that is, if the elasticity is low, it becomes difficult to handle in the manufacturing process. It is known that the coefficient of linear expansion and the elastic modulus of a polyimide film largely depend on the primary chemical structure of the polyimide. However, in general, when a polyimide primary chemical structure having a large elastic modulus is selected, the linear expansion coefficient becomes small, and it is difficult to match the elastic modulus and the linear expansion coefficient.

[0004]

In view of the above situation, the inventors of the present invention have made earnest studies, and as a result, in the process of processing a TAB tape or a flexible printed circuit board, warpage or curling does not occur without elongation. The present invention relates to a polyimide film that does not have the above.

[0005]

The present invention comprises a composition containing at least a polyimide resin component and a mica type inorganic filler, and has a tensile elastic modulus of 4 GPa or more and an average linear expansion coefficient from 100 ° C to 200 ° C of 18 ~ 28 ppm,
It relates to a polyimide film having a hygroscopic expansion coefficient of 15 ppm or less.

Further, the present invention comprises a composition containing at least a polyimide resin component and a mica type inorganic filler,
The present invention relates to a polyimide film having a tensile elastic modulus of 5 GPa or more, an average linear expansion coefficient from 100 ° C. to 200 ° C. of 20 to 25 ppm, and a hygroscopic expansion coefficient of 12 ppm or less.

The present invention also relates to the above polyimide film, wherein the mica type inorganic filler is synthetic mica.

The present invention also relates to the above polyimide film, wherein the mica-based inorganic filler is a non-swelling mica.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The polyimide film of the present invention will be described below based on an example of its embodiment. The polyimide film of the present invention is produced by casting an organic solvent solution of a polyamic acid, which is a polyimide precursor, on a support such as an endless belt or a stainless drum, followed by drying and imidization. As a method for producing the polyamic acid used in the present invention, a known method can be used. Usually, at least one kind of aromatic acid dianhydride and at least one kind of diamine are used in a substantially equimolar amount in an organic solvent. And the resulting polyamic acid organic solvent solution is stirred under controlled temperature conditions until the polymerization of the acid dianhydride and diamine is completed. These polyamic acid solutions are usually 5 to 35 wt%,
It is preferably obtained at a concentration of 10 to 30 wt%. When the concentration is within this range, an appropriate molecular weight and solution viscosity are obtained. As the polymerization method, any known method can be used, and particularly preferable polymerization methods include the following methods. That is, 1) a method in which an aromatic diamine is dissolved in an organic polar solvent, and a substantially equimolar amount of an aromatic tetracarboxylic dianhydride is reacted therewith to perform polymerization. 2) Aromatic tetracarboxylic acid dianhydride is reacted with an aromatic diamine compound in an excessively small molar amount in an organic polar solvent to obtain a prepolymer having acid anhydride groups at both ends. Then, a method of polymerizing using an aromatic diamine compound so that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar in all steps. 3) Aromatic tetracarboxylic dianhydride is reacted with an excess molar amount of an aromatic diamine compound in an organic polar solvent to obtain a prepolymer having amino groups at both ends. Then after adding additional aromatic diamine compound here,
A method of polymerizing using an aromatic tetracarboxylic dianhydride such that the aromatic tetracarboxylic dianhydride and the aromatic diamine compound are substantially equimolar in all steps. 4) A method in which an aromatic tetracarboxylic dianhydride is dissolved and / or dispersed in an organic polar solvent, and then polymerization is performed using an aromatic diamine compound so as to be substantially equimolar. 5) A method of reacting a mixture of substantially equimolar amounts of aromatic tetracarboxylic dianhydride and aromatic diamine in an organic polar solvent to perform polymerization. And so on. Here, the materials used for the polyimide precursor polyamic acid composition according to the present invention will be described.

Suitable acid anhydrides for use in the present polyimides are pyromellitic dianhydride, 2,3,6,7.
-Naphthalene tetracarboxylic dianhydride, 3,3 ',
4,4'-biphenyltetracarboxylic dianhydride, 1,
2,5,6-naphthalenetetracarboxylic dianhydride,
2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) Propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) Ethane dianhydride,
1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, oxydiphthalate Acid dianhydride, bis (3,
4-dicarboxyphenyl) sulfone dianhydride, p-phenylene bis (trimellitic acid monoester acid anhydride), ethylene bis (trimellitic acid monoester acid anhydride), bisphenol A bis (trimellitic acid monoester acid anhydride) Products) and their analogs, and these can be preferably used alone or in a mixture in any ratio.

Of these, p-phenylene bis (trimellitic acid monoester anhydride), pyromellitic dianhydride and these are most suitable acid dianhydrides in the polyimide precursor polyamic acid composition used in the present invention. The mixture of is raised. Furthermore, the molar ratio of p-phenylene bis (trimellitic acid monoester anhydride) and pyromellitic dianhydride is 95/5 to 5/95, preferably 80/20 to 5/95, and further 70/30 to 1
When a mixture of 0/90, more preferably 60/40 to 15/85, is used, a polyimide film having an excellent balance of various properties can be obtained.

Suitable diamines which can be used in the polyimide precursor polyamic acid composition according to the present invention include 4,4'-oxydianiline, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 4,
4'-diaminodiphenylmethane, benzidine, 3,
3'-dichlorobenzidine, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 4,4 '
-Oxydianiline, 3,3'-oxydianiline,
3,4'-oxydianiline, 1,5-diaminonaphthalene, 4,4'-diaminodiphenyldiethylsilane,
4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-
Diaminodiphenyl N-methylamine, 4,4'-diaminodiphenyl N-phenylamine, 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene, 1,2-diaminobenzene and their analogues And so on. Among these diamine compounds, 4,4′-oxydianiline and p-phenylenediamine are in a molar ratio of 1/9 to 9/1, preferably 1/7 to
It is preferable to use 7/1, and more preferably 1/4 to 4/1 because a polyimide film excellent in balance of various properties can be obtained. Preferred solvents for synthesizing polyamic acid are 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. Further, as the mica-based inorganic filler used in the present invention, any of natural mica and synthetic mica may be used, but it is particularly preferable to use synthetic mica, especially synthetic fluoromica from the viewpoint of stabilizing the film production process. . Further, the mica can be classified into swelling property and non-swelling property, but according to this classification, it is preferable to use a non-swelling mica in order to achieve a low water absorption coefficient, that is, a low hygroscopic expansion coefficient. Mica-based inorganic filler is
An average particle size of 1 to 100 μm, preferably 1 to 75 μm,
More preferably 1 to 50 μm, particularly preferably 1 to 25
μm, aspect ratio is 10 to 50, preferably 1
It is desirable to use one having a diameter of 5 to 45, more preferably 20 to 45. If the size of the mica-based inorganic filler is out of the above range, the mechanical strength may be reduced, or when used as a base film for TAB, transparency, which is an important characteristic, may be greatly impaired. Further, the addition amount of the mica-based inorganic filler is 30 parts by weight or less, preferably 20 parts by weight or less, more preferably 15 parts by weight or less, and particularly preferably 10 parts by weight or less based on 100 parts by weight of the polyimide. If the amount added exceeds the above range, various properties such as water absorption properties, mechanical strength and transparency may be adversely affected. Addition of mica-based inorganic filler, 0 method of adding to the polymerization reaction solution before or during the polymerization 1 after completion of the polymerization method of kneading the filler using a three-roll etc. 2 prepare a dispersion liquid containing the filler, May be used any method such as a method of mixing with a polyamic acid organic solvent solution, but a method of mixing a dispersion containing a filler with a polyamic acid solution, particularly a method of mixing immediately before film formation causes contamination by the filler in the production line. It is preferable because it requires the least amount. When preparing a dispersion liquid containing a filler, it is preferable to use the same solvent as the polyamic acid polymerization solvent. Also, disperse the filler well,
Further, in order to stabilize the dispersed state, a dispersant, a thickener, etc. may be used within a range that does not affect the physical properties of the film. A conventionally known method can be used as a method for producing a polyimide film from these polyamic acid solutions. Examples of this method include a thermal imidization method and a chemical imidization method, and from the viewpoint of thermal dimensional stability and mechanical strength, imidization by the chemical imidization method is preferable. The chemical curing method includes a polyamic acid organic solvent solution, a dehydrating agent typified by an acid anhydride such as acetic anhydride, and an imidization catalyst typified by tertiary amines such as isoquinoline, β-picoline, and pyridine. Is a method of acting. The thermal imidization method may be used in combination with the chemical imidization method. The heating conditions may vary depending on the type of polyamic acid, the thickness of the film, and the like. As described above, the 0 elastic modulus is 4 GPa or more, preferably 4.5 GPa or more, more preferably 5 GPa or more, and the average linear expansion coefficient at 1100 to 200 ° C. is 18 to 28 pp.
m, preferably 18 to 25 ppm, more preferably 20
-25 ppm 2 Hygroscopic expansion coefficient 15 ppm or less, preferably 12 pp
m or less, particularly preferably 10 ppm or less 3 thickness is 10 to 125 μm, preferably 20 to 100 μm
m, more preferably 25 to 75 μm, particularly preferably 4
A polyimide film having a thickness of 0 to 60 μm can be obtained. By satisfying these characteristics in the above ranges, it is possible to eliminate the above-mentioned inconveniences particularly in the process of processing a TAB tape or a flexible printed circuit board.

Furthermore, by using the polyimide film thus obtained, flexible printed circuit boards and T
When the AB tape is produced, the amount of warp after the adhesive is completely cured (without etching the copper foil) is preferably 1.
5 mm or less, more preferably 1.3 mm or less, particularly preferably 1.0 mm or less, and the amount of warp after the copper foil is completely removed by etching is preferably 4 mm.
The following is more preferably 3.5 mm or less, and particularly preferably 3 mm or less. When the amount of warpage with copper foil and the amount of warp after copper foil full etching satisfy these ranges at the same time, it is possible to eliminate defects caused by warpage in the processing and mounting steps.

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples. (Reference example) TAB tape preparation and warp measurement The warp value is the TAB tape 35 prepared by the following procedure.
It was cut out into a square of mm, left for 72 hours in a room with a humidity of 60% RH and a temperature of 23 ° C., and then allowed to stand on a flat surface, and the rising heights of the four corners were measured. 0
Polyamide resin (platabond M12 manufactured by Nippon Rilsan Co., Ltd.)
76) 50 parts by weight, 30 parts by weight of bisphenol A type epoxy resin (Epicoat 828 manufactured by Yuka Shell Epoxy Co., Ltd.), 10 parts by weight of cresol novolac type epoxy resin,
Toluene / isopropyl alcohol 1/1 mixed solution 15
An adhesive solution was prepared by mixing 0 part by weight of the solution with 45 parts by weight of diaminodiphenyl sulfone / dicyandiamide 4/1 20% methyl cellosolve solution.
Adhesive on PET film with a thickness of μm, 11 μm after drying
And was dried at 120 ° C. for 2 minutes. This B
The PET film with the stage adhesive was slit into a width of 27 mm. A PET film with a B-stage adhesive was stuck to the center of a polyimide film having a width of 235 mm, and pressure-bonded at 90 ° C. under a pressure of 1 kg / cm ² . PE
Peel off the T film and remove the copper foil (Mitsui Kinzoku, VLP 18μ
m thickness) and the roll lamination method. The laminating temperature is 120 ° C. and the pressure is 2 kg / cm ² . (TAB tape without etching) 3 Heat the above copper-clad product in steps of 60 ° C for 3 hours, 80 ° C for 3 hours, 120 ° C for 3 hours, 140 ° C for 3 hours, and 160 ° C for 4 hours, and then gradually cool. Then, the adhesive was cured. (Tape without etching) 4 After the adhesive was cured, the copper foil was completely removed by etching. (Copper full etching tape) (Example 1) Pyromellitic dianhydride, p-phenylene bis (trimellitic acid monoester anhydride), 4,4'-oxydianiline, p-phenylenediamine in a molar ratio of 7
To 100 g of a 18 wt% DMF solution of polyamic acid synthesized at a ratio of 0/30/75/25, another 10 g of DM was added.
Synthetic fluoromica on F (MK-200 manufactured by Corp Chemical);
Average particle size 5-8 μm, aspect ratio 20-30) 0.9
The total amount of the dispersion liquid in which g was dispersed was mixed with stirring. A curing agent composed of 20 g of acetic anhydride and 10 g of isoquinoline was mixed with this filler-containing polyamic acid solution, stirred, defoamed by centrifugation, and cast-coated on an aluminum foil. The process from stirring to defoaming was performed while cooling to 0 ° C. The laminate of this aluminum foil and the polyamic acid solution is heated at 120 ° C. for 150 seconds,
A gel film having self-supporting property was obtained. This gel film was peeled off from the aluminum foil and fixed to the frame. This gel film at 300 ℃, 400 ℃, 500 ℃ each 30
A polyimide film was obtained by heating for 2 seconds, and a TAB tape was prepared according to the reference example. Polyimide film and TA
The characteristics of the B tape are shown in Table 1.

(Example 2) 1.8 g of synthetic fluoromica (MK-200 manufactured by Corp Chemical); average particle size 5 to 8 μm
m, aspect ratio 20 to 30), except that Example 1 was used.
A polyimide film and a TAB tape were obtained in the same manner as in. Table 1 shows the characteristics of polyimide film and TAB tape.
Shown in.

(Example 3) 0.9 g of synthetic fluoromica (MK-100 manufactured by Corp Chemical); average particle size 3 to 5 μm
m, aspect ratio 20 to 30), except that Example 1 was used.
A polyimide film and a TAB tape were obtained in the same manner as in. Table 1 shows the characteristics of polyimide film and TAB tape.
Shown in. (Example 4) Pyromellitic dianhydride, p-phenylene bis (trimellitic acid monoester anhydride), 4,4'-oxydianiline, p-phenylenediamine in a molar ratio of 7
A polyimide film and a TAB tape were obtained in the same manner as in Example 1 except that an 18 wt% DMF solution of a polyamic acid synthesized at a ratio of 0/30/80/20 was used. Table 1 shows the characteristics of the polyimide film and the TAB tape.

(Comparative Example 1) Pyromellitic dianhydride, 4,
A polyimide film and a TAB tape were prepared in the same manner as in Example 1 except that an 18 wt% DMF solution of a polyamic acid prepared by synthesizing 4'-oxydianiline and p-phenylenediamine in a molar ratio of 100/75/25 was used. Got
Table 1 shows the characteristics of the polyimide film and the TAB tape. (Comparative Example 2) Pyromellitic dianhydride, p-phenylene bis (trimellitic acid monoester anhydride), 4,4'-oxydianiline, and p-phenylenediamine in a molar ratio of 7
A polyimide film and a TAB tape were obtained in the same manner as in Example 1 except that an 18 wt% DMF solution of a polyamic acid synthesized at a ratio of 2/28/70/30 was used and no synthetic mica was used. Polyimide film and TA
The characteristics of the B tape are shown in Table 1.

[0018]

[Table 1]

[0019]

According to the present invention, it is possible to provide a polyimide film which does not warp or curl in the process of processing a flexible printed circuit board or a TAB tape.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor, Renichi Akahori             23-6 Ogokita, Otsu City, Shiga Prefecture F term (reference) 4F071 AA60 AB26 AE17 AF10Y                       AF20Y AF62Y BC01                 4J002 CM041 DJ056 FD016 GQ00                       GQ01

Claims (4)

[Claims] 1. A composition comprising at least a polyimide resin component and a mica-based inorganic filler, having a tensile modulus of 4 GPa or more, an average linear expansion coefficient from 100 ° C. to 200 ° C. of 18 to 28 ppm, and a hygroscopic expansion coefficient of 15 ppm.
The following polyimide film. 2. A composition comprising at least a polyimide resin component and a mica-based inorganic filler, having a tensile modulus of 5 GPa or more, an average linear expansion coefficient from 100 ° C. to 200 ° C. of 20 to 25 ppm, and a hygroscopic expansion coefficient of 12 ppm.
The following polyimide film. 3. The polyimide film according to claim 1, wherein the mica-based inorganic filler is synthetic mica. 4. The polyimide film according to claim 1, wherein the mica-based inorganic filler is a non-swelling mica.