JPH10192773A - Method for drying polyimide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide film which is never foamed due to the vaporization of the remaining solvent and moisture in one step, excellent in productivity without deteriorating the resin and reduced in remaining solvent. SOLUTION: This drying method consists in bringing the solvent and moisture remaining in a polyimide film or a polyimide laminated film into contact with a supercritical fluid below the glass transition temp. of the resin and removing them. In this case, the polyimide film and a highly air-permeable spacer film are couple, wound and brought into contact with the supercritical fluid. Carbon dioxide is used as the supercritical fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyimide film used for a flexible printed wiring board or a TAB tape, an adhesive sheet for bonding printed wiring boards (so-called bonding sheet), a coverlay film or a semiconductor chip to a lead frame. The present invention relates to a method for drying a polyimide adhesive film used for an adhesive tape for bonding (so-called LOC tape) and the like.

[0002]

2. Description of the Related Art A polyimide film is used as a base material of a flexible printed wiring board or a TAB tape, and a polyimide adhesive film is used as a bonding sheet or a coverlay film for a rigid flexible printed wiring board, or a semiconductor chip is bonded to a lead frame. LOC tapes and the like have been widely used in applications requiring reliability with the reduction in size and weight of electric and electronic devices. However, while polyimide-based films have excellent heat resistance, film production requires extremely expensive equipment because the solvent contained inside cannot be sufficiently removed unless heated sufficiently at a temperature higher than the glass transition temperature of the resin. This was a major factor in reducing sex.
In addition, in the case of a polyimide adhesive film to which other resin than polyimide is added for the purpose of lowering the adhesiveness and processing temperature, if the resin is dried at a high temperature for a long time, the resin inside hardens or decomposes, and the original purpose adhesiveness Therefore, it is necessary to dry at a high temperature that does not cause a reaction for a long period of time, which causes a significant decrease in productivity. In applications using these polyimide resins, high temperature processes such as soldering and thermocompression are often performed in the post-process in order to take advantage of the high heat resistance of the polyimide, but at this time the solvent or moisture is sufficiently removed in advance. If not, there is a problem that the remaining solvent and water vaporize at a stretch and foam.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyimide-based film which is excellent in productivity without deteriorating the quality of the resin and has a small amount of residual solvent.

[0004]

According to the present invention, there is provided a polyimide film characterized in that a solvent and moisture remaining in a polyimide film or a polyimide composite film are removed by contact with a supercritical fluid having a temperature lower than the glass transition temperature of the resin. A method for drying a polyimide film, wherein a pair of a spacer film having good air permeability and a polyimide film are brought into contact with a supercritical fluid in a wound state at this time. A supercritical fluid to be used is carbon dioxide, which is a method for drying a polyimide film.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a polyimide resin is a polyimide having an imide skeleton, a polyether imide, a polyamide imide resin or the like, and a polyimide resin is used to reduce the processing temperature and improve the adhesiveness. Examples of the purpose include a resin to which another resin such as an epoxy resin, an acrylic resin, a polyamide resin, and a polyamideimide resin is added. However, the resin film is not particularly limited as long as it is a resin film containing polyimide as a main component. The polyimide resin used in the present invention is generally obtained by thermally or chemically ring closing a precursor polyamic acid, but is not particularly limited. The polyamic acid is usually obtained by reacting a diamine with an acid anhydride. Examples of the diamine include phenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, diaminodiphenylether, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, and 1,3-bis (3-aminophenoxy) benzene , 4,4'-diaminodiphenylmethane,
3,3'-dimethylbenzidine, 4,4'-diamino-P-terphenyl, 4,4'-diamino-P-quarterphenyl, 2,8-diaminodiphenylene oxide or α, ω-bis (3
Siloxane diamines such as -aminopropyl) polydimethylsiloxane, and as acid anhydrides, trimellitic anhydride, pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, benzophenonetetracarboxylic dianhydride, oxydiphthalic acid A dianhydride or the like can be used, but is not limited thereto. In addition, one kind or two or more kinds can be used in appropriate combination.

In the present invention, the polyimide resin can be generally obtained via a polyamic acid. In this case, the solvent is usually obtained in an organic polar solvent which does not react with tetracarboxylic dianhydride or diamine. In addition to being inert to the reaction system and being a solvent for the product, the organic polar solvent must be a good solvent for at least one of the reaction components, preferably both. Typical solvents of this type include N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfone, dimethylsulfoxide, N-methyl-2-pyrrolidone, and the like, and these solvents may be used alone or in combination. used. In addition, non-polar solvents such as benzene, dioxane, xylene, toluene, and cyclohexane may be used in combination as solvents, as a dispersion medium of a raw material, a volatilization regulator from a reaction regulator or a product, a volatilization regulator from a product, a film smoother, and the like. used.

The polyimide composite film in the present invention is a composite film in which a polyimide-based film and a metal foil or another resin film are laminated. A flexible printed circuit board or a TAB tape in which a copper foil and a polyimide film are laminated. And a bonding sheet in which a polyimide-based film is formed on PET or aluminum foil, but is not particularly limited as long as the polyimide-based film is laminated on another film.

As the supercritical fluid in the present invention, carbon dioxide is preferable. However, a supercritical fluid which exhibits a supercritical state below the glass transition temperature of the resin, has a solubility constant close to that of the above-mentioned solvent, and has low toxicity and flammability is particularly preferred. Not limited. The temperature and pressure for removing the solvent differ depending on the type of solvent and the type of supercritical fluid, but when using carbon dioxide,
The temperature is preferably from 31 to 150 ° C and from 75 to 300 kgf / cm ² .

Materials that can be used as the spacer film include plastic films such as polypropylene, polyester, polyethersulfone, polyimide, polyetherimide, polyamide, and polyethylene, and metal foils such as aluminum foil, copper foil, and stainless steel foil. Can be mentioned. The shape of the spacer film is not particularly limited as long as it improves the contact area between the polyimide resin and the supercritical fluid, but is generally embossed, has protrusions (dimples) at its ends, or has a mesh shape. And the like.

[0010]

【Example】

(Example 1) 1428 g of dehydrated and purified N-methyl-2-pyrrolidone (NMP) was placed in a four-necked flask equipped with a dry nitrogen gas inlet tube, a cooler, a thermometer, and a stirrer, and nitrogen gas was allowed to flow therethrough. While stirring the 2,2-bis (4- (4
-Aminophenoxy) phenyl) propane (BAPP)
82.1 g (0.10 mol), 38.7 g (0.20 mol) of 1,3-bis (3-aminophenoxy) benzene (APB), α, ω-bis (3-aminopropyl) dimethyldisiloxane ( (APDS) 24.9 g (0.10 mol) is added and stirred until uniform. After uniformly dissolving, keeping the system at 20 ° C., 82.4 g of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA).
(0.28 mol), 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride (BTDA) 38.7 g
(0.12 mol) in the form of a powder over 15 minutes, followed by stirring for 8 hours. During this time the flask is 20
C. After that, remove the nitrogen gas inlet tube and cooler,
A Dean-Stark tube filled with toluene was attached to the flask, and 612 g of toluene was added to the system. The system was heated to 175 ° C. instead of the oil bath, and the generated water was removed from the system. 6
After heating for an hour, no water was generated from the system. By cooling the system, the polyimide solution PI-
1 was obtained.

In a glass flask, a polyimide resin PI-
1, 500 g of bisphenol A type epoxy compound (Epicoat 828, manufactured by Yuka Shell Epoxy) at room temperature
0 g, xylenol resin (trade name: Xyloc) 10 g
Was gradually added while stirring the system, and subsequently stirred for 2 hours to prepare a polyimide resin solution. The glass transition temperature of the obtained resin was 170 ° C. according to thermomechanical analysis.
(Hereinafter, all the glass transition temperatures are determined by thermomechanical analysis.) Apply this modified polyamic acid solution to one side of a commercially available polyester film (manufactured by Mitsubishi Diafoil) using a bar coater so that the thickness after imidization becomes 100 μm with a bar coater. Then, drying was performed at 110 ° C. for 30 minutes, 130 ° C. for 30 minutes, and 160 ° C. for 60 minutes to obtain a polyimide-based adhesive film having a polyester film on one side (Film 1). When the solvent content in the obtained polyimide-based adhesive film was subjected to thermogravimetric analysis (temperature range: 30 to 400 ° C .; hereinafter, the solvent content was measured using the same apparatus and under the same conditions), 1.3% of the solvent still remained. I knew I was doing it. This polyimide film is wound 100 m inside a spacer having a protrusion having a height of 2 mm at the end of a stainless steel plate, pressure 100 kg / cm ² , temperature 35
The solution was treated with carbon dioxide in a controlled critical state at a temperature of 1 ° C. for 1 hour, and the content of the solvent in the resin was measured and found to be 0.018%.

Comparative Example 1 Using the film 1 of Example 1
After drying at 180 ° C. for 30 minutes and at 200 ° C. for 30 minutes, the solvent content was still 0.18%. On the other hand, when drying was further performed at 240 ° C. for 30 minutes, the solvent content was reduced to 0.03%, but the epoxy resin in the resin was cured and the adhesive strength was lost, so that it could no longer be used as an adhesive film.

EXAMPLE 2 108 g of purified anhydrous paraphenylenediamine and 4,4'-diamino were placed in a four-neck separable flask equipped with a thermometer, a stirrer, a reflux condenser and a dry nitrogen gas inlet. Take 200 g of diphenyl ether, add thereto a mixed solvent of 90% by weight of anhydrous N-methyl-2-pyrrolidone and 10% by weight of toluene, and add an amount such that the solid content ratio in all the raw materials becomes 20% by weight. In addition, it dissolved. Dry nitrogen gas was allowed to flow throughout the entire process from the preparation of the reaction to the removal of the product. Next, 294 g of purified anhydrous 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and 218 g of pyromellitic dianhydride are added little by little with stirring. The mixture was cooled by circulating cold water at about 15 ° C. After the addition, the internal temperature was set to 20 ° C., and the mixture was stirred for 5 hours, and the reaction was completed to obtain a polyamic acid solution. The glass transition temperature of the obtained resin after imidization was 312 ° C. according to thermomechanical analysis. This polyamic acid solution was applied on a commercially available copper foil with a bar coater so that the thickness after imidization became 25 μm, and was applied at 110 ° C. for 15 minutes, 1 minute.
Heating and drying at 50 ° C. for 15 minutes, 200 ° C. for 15 minutes, 250 ° C. for 15 minutes, and 300 ° C. for 15 minutes, a polyimide composite film 2 (flexible printed circuit board) was obtained. A thermogravimetric analysis of the solvent content in the obtained polyimide composite film showed that 3.3% of the solvent still remained. 100m wound pressure 100 kg / cm ² to the copper foil of this polyimide film to the spacer interior which is provided a protrusion height of 2mm on the end of the stainless steel plate is brought into close contact with the stainless steel spacer strip, the critical state regulating temperature 35 ° C. Carbon dioxide For 1 hour, the content of the solvent in the resin was measured and found to be 0.008%.

Comparative Example 2 The polyimide composite film 2 of Example 2 was dried at 350 ° C. for 30 minutes, but the solvent content was still 0.78%. On the other hand, when the solvent was further dried at 380 ° C. for 30 minutes, the solvent content was reduced to 0.014%. However, a high-temperature furnace which can always be replaced with a nitrogen atmosphere so as not to oxidize the copper foil is indispensable. Because of the high temperature, it was annealed and softened, and could not be used for applications requiring the rigidity of copper foil such as TAB.

[0015]

According to the present invention, a polyimide film or a polyimide composite film is wound into a pair with a spacer film having good air permeability, and the supercritical state of carbon dioxide or the like which becomes a supercritical state below the glass transition temperature of the resin is obtained. Is a method for drying a polyimide film characterized by removing the solvent and moisture remaining in contact with the fluid,
This method is an industrially superior method of drying a polyimide-based film that can remove a small amount of residual solvent, which was usually difficult to remove, with little heat or mechanical damage to the polyimide-based film and efficiently remove the film without deteriorating the film. It is.

Claims (4)

[Claims] 1. A method for drying a polyimide film, comprising removing a solvent and moisture remaining in the polyimide film by contacting the solvent and water with a supercritical fluid having a glass transition temperature of the resin or lower. 2. The method for drying a polyimide composite film according to claim 1, wherein the polyimide film is a composite film with a metal or another resin. 3. A method for drying a polyimide-based film according to claim 1, wherein the polyimide-based film is brought into contact with a supercritical fluid in a wound state while being paired with a spacer film having good air permeability. 4. The method for drying a polyimide film according to claim 1, wherein the supercritical fluid is carbon dioxide.