CN1654518A - Preparation method of polyimide film for flexible printed circuit board - Google Patents

Abstract

The invention relates to a preparation method of polyimide film for flexible printed circuit board, which comprises dissolving monomer diamine and plasticizer in polar aprotic solvent, adding dianhydride with equal molar ratio to diamine, mixing for 2-20 hours, synthesizing polyamic acid solution containing plasticizer, uniformly coating polyamic acid solution on glass plate, placing in drying oven, and heating to 200-400 deg.C to obtain polyimide film with similar Coefficient of Thermal Expansion (CTE) and stable size for flexible printed circuit board.

Description

A kind of preparation method of polyimide film for flexible printed circuit board

Technical field:

The invention relates to a preparation method of a polyimide film, in particular to a preparation method of a polyimide film for a flexible printed circuit board.

Background technique:

Polyimide (PI) films have excellent comprehensive properties and are widely used in electrical, electronic and aerospace fields. In recent years, the market of polyimide film has grown significantly, which mainly depends on the market of flexible printed circuit board (FPC).

The application of FPC is changing all the time. It started in the 1970s and was mainly used as a component of cameras. It was used in cameras in the 1980s. In the 1990s, the application of FPC in computers increased significantly. After 2000, it was mainly used in microelectronics industries such as mobile phones. With the continuous expansion of FPC applications, the demand for FPC with fine circuit graphics continues to increase, and higher requirements are placed on the performance of polyimide films. At this stage, dimensional stability has become a key indicator of polyimide films for FPC.

FPC is made of polyimide film coated with adhesive, baked at a certain temperature, covered with copper foil, hot pressed or compounded; there is also a polyamic acid solution directly coated on the copper foil, and directly bonded with the copper foil after heat treatment. copper foil bonded. In the manufacturing process of FPC, polyimide film and copper foil are subjected to high temperature and high humidity environment. The different degrees of dimensional change between polyimide film and copper foil make it difficult to manufacture FPC with fine circuit patterns.

In addition, when PI resin is applied to copper clad laminates, its thermal expansion coefficient is much larger than that of electronic components. In the process of manufacturing and processing, due to the difference in expansion coefficient, there is a large internal stress in the product, circuit peeling or cracking occurs, and even breakage occurs in severe cases, which greatly affects the performance of PI-based CCL products.

In order to improve and broaden the application of PI resin in the copper clad laminate industry, subsequent research has focused on the preparation of low thermal expansion polyimide. Low thermal expansion polyimides are generally prepared from monomers with special structures. The structure of this type of monomer has two characteristics: (1) the diamine structure is composed of a benzene ring or nitrogen heterocycle bonded to the para-position, and does not contain flexible bonds such as ether or methylene; (2) The structure of dianhydride is biphenyl type or homophenyl type.

USPat.No.4725484 discloses a composition of polyimide film that can be used to prepare flexible printed circuit boards. Its monomer dianhydride is biphenyl dianhydride 3,3'4,4'-biphenyl tetra Carboxylic acid dianhydride (BPDA), the thermal expansion coefficient of the prepared polyimide film is 1-25ppm K ^-1 between 50°C and 300°C. However, the recent patent USPat.No. 2004/0126600 A1 points out that the compositions disclosed in USPat.No. 4725484 are obviously "rigid" monomers, and the price of rigid dianhydride BPDA is very expensive compared with ordinary dianhydrides.

In addition, the macromolecular chains polymerized from "rigid" monomers generally have a rod-like structure, which is very rigid, poor in flexibility, and poor in adhesion to inorganic materials. There are still some defects in practical applications. (Fan Heping. Printed Circuit Information 1997. (5): 17.)

In addition, studies have shown that methods such as blending modification, multi-component copolymerization, adding fillers, organosiloxane modification and nanoparticle hybridization can effectively reduce the thermal expansion coefficient of PI resin.

In JP-P2-150 451, rigid diamine and pyromellitic dianhydride are used to prepare PA solution, and then 4,4'-diaminodiphenyl ether and pyromellitic dianhydride are used to prepare PA solution, and the two are mixed and stirred Afterwards, casting and drying to obtain a film with a CTE of 2ppmK ^-1 .

AKSt.Clair added lanthanum chloride to the PI composed of benzophenone tetraacid dianhydride and 4,4'-oxybenzidine according to the ratio of metal ion to polymer repeating unit of 1:4, and the addition amount was 1% of the film 11.3% to 11.6% (mass), the CTE of DuPont's film dropped from 35ppmK ^-1 to 18ppmK ^-1 , and the CTE of Seiko's film dropped from 39ppmK ^-1 to 17ppmK ^-1 . (Polym. Mater. Sci. Eng., 1996, 71: 725; Polym. Mater. Sci. Eng., 1997, 76: 185; J. Mater. Res., 1996, 11: 841)

Nihon Susu Co., Ltd. used pyromellitic dianhydride, biphenyltetraic dianhydride, diamine and 4-aminophenyltrimethoxysilane to copolymerize, and the modified PI obtained had excellent adhesion and low CTE. (JP 64-6 025)

The Toyota Research Center in Japan used 4,4'-diaminodiphenyl ether and pyromellitic acid to synthesize PI/Clay hybrid materials, and the CTE was about 50% lower than that before hybridization.

The above methods of blending modification and multi-component copolymerization have been adopted by some manufacturers of polyimide film, but they basically introduce monomers with a rigid structure, which increases the cost of raw materials. In addition, the introduction of chloride ions has adverse effects on the electrical properties of the film. Secondly, methods such as adding fillers, organosiloxane modification, and nanoparticle hybridization all change the basic composition of the film-polyimide. The excellent performance of the printed circuit board increases the difficulty of the preparation process and increases the cost of raw materials. Methods such as adding fillers, organosiloxane modification, and nanoparticle hybridization have not yet been applied to industrial production.

In addition, biaxial stretching is an effective method for preparing polyimide films with high dimensional stability. DuPont, a major foreign polyimide film manufacturer, has adopted a biaxial stretching process. However, the biaxial stretching process is complex and the equipment has high precision.

Invention content:

The technical problem to be solved by the present invention: the purpose of the present invention is to provide a method for preparing a polyimide film with high dimensional stability for flexible printed circuit boards.

The technical solution of the present invention is: on the basis of preparing polyimide film by the two-step method, by adjusting the amount of high-temperature plasticizer added to control the crystallinity and orientation of the film, and finally obtain a polyimide film with a CTE similar to that of copper foil, Dimensionally stable polyimide film.

The method for preparing polyimide film is characterized in that, on the basis of preparing polyimide film by two-step method, by adding plasticizer in the process of preparing polyamic acid, the temperature range of molecular chain orientation is expanded, Adjust the crystallinity or orientation of the film to obtain a dimensionally stable polyimide film with a CTE similar to that of copper foil. The steps are:

(a) dissolving monomeric diamine and plasticizer in a polar aprotic solvent, adding dianhydride in an equimolar ratio to diamine, mixing for 2-20 hours, and synthesizing a polyamic acid solution containing plasticizer; Wherein, wherein the addition of plasticizer accounts for the mass percent of synthetic polyamic acid to be 0.05%-5%,

(b) Apply the above-mentioned polyamic acid solution containing plasticizer evenly on a glass plate, put it into a drying oven and heat up to 200°C-400°C, preferably 250°C-400°C. A dimensionally stable polyimide film for flexible printed wiring boards was obtained.

Wherein the plasticizer is phthalates, terephthalates, dibasic esters, alkyl sulfonates, epoxy esters, chlorinated paraffins, phosphates; the plasticizer is preferably triphosphate Phenyl ester, triphenyl phosphite, triethyl phosphate, tricresyl phosphate, phenyl alkyl sulfonate, dioctyl phthalate, dibutyl phthalate or diisooctyl terephthalate ; The amount of plasticizer added is preferably 0.05% to 2% of the mass percentage of the synthetic polyamic acid. The diamine is one of the following aromatic diamines, 4,4'-diaminodiphenyl ether (ODA), bis(3-aminophenoxy)diphenylsulfone (BAPS), 1,3-bis(3 -aminophenoxy)benzene (BAPB), diaminodiphenylsulfone (DDS), diaminobenzophenone (DABP), diaminobenzene (PDA), dianilinemethane (MDA); dianhydrides are the following A kind of aromatic dianhydride, pyromellitic dianhydride (PMDA), 3,3',4,4'-diphenyl ether tetracarboxylic dianhydride (ODPA), 3,3',4,4'- Biphenyl tetracarboxylic dianhydride (BPDA), bisphenol A dianhydride (BPADA), benzophenone tetracarboxylic dianhydride (BTDA). The polar aprotic solvent is N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc) or N-methyl-pyrrolidone (NMP);

The beneficial effects of the present invention are: by adding a certain amount of plasticizer in the process of preparing polyamic acid, the crystallinity and orientation degree of the film are adjusted, that is, the molecular chain in the film structure is controlled by adjusting the amount of plasticizer added. The degree of order can be obtained to obtain a dimensionally stable polyimide film with a CTE similar to that of copper foil. Compared with the polyimide film prepared by the traditional method, the polyimide film prepared by the present invention has the following characteristics: 1. High dimensional stability, and its CTE is controlled at 10ppmK ^-1 ~ 30ppmK ^-1 ; 2. Monomer The structure of dianhydride is less restrictive; 3. The raw material cost is low and the process is simple.

Detailed ways:

Example 1.

Add 2.4g of 4,4'-diaminodiphenyl ether (ODA), 0.67g triphenyl phosphite and 30ml N,N'-dimethylformamide (DMF) into a clean Erlenmeyer flask, stir until Dissolve completely, add 2.62g of pyromellitic dianhydride (PMDA) in batches according to the batching ratio, stir and react for 4-5 hours, and generate a viscous light yellow polyamic acid solution. Spread the polymer solution evenly on a glass plate, put it in an oven, and heat it with a temperature program: 130°C for 2 hours, 170°C for 0.5 hour, 200°C for 0.5 hour, 280°C for 1 hour, and 350°C for 2 hours to finally get the CTE at Between 50°C and 250°C is 24-28ppmK ^-1 polyimide film.

Example 2.

In a clean Erlenmeyer flask, add 2.4g of 4,4'-diaminodiphenyl ether (ODA), 1.34g of triphenyl phosphite and 30ml of N, N'-dimethylformamide (DMF), and stir until Completely dissolved, the following preparation method is the same as that of Example 1, and finally a polyimide film with a CTE of 18-22ppmK ^-1 between 50°C and 250°C is obtained.

Example 3.

Add 24.8g of diaminodiphenyl sulfone (DDS), 1.5g of triphenyl phosphite and 200ml of N, N'-dimethylacetamide (DMAc) into a clean Erlenmeyer flask, stir until completely dissolved, and mix according to the ingredients 29.4 g of 3,3,4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added in batches, and stirred for 5-6 hours to generate a viscous polyamic acid solution. Spread the polymer solution evenly on a glass plate, put it in an oven, and heat it with a temperature program: 100°C for 2 hours, 170°C for 1 hour, 200°C for 1 hour, 300°C for 1 hour, and 400°C for 2 hours to finally get the CTE at 14-18ppmK ^-1 polyimide film between 50°C and 250°C.

Claims (10)

1, a kind of preparation method of polyimide film for flexible printed wiring board, it is characterized in that on the basis of preparing polyimide film in two steps, by adding plasticizer in the process of preparing polyamic acid, In order to obtain a polyimide film with a thermal expansion coefficient close to that of copper foil and a dimensionally stable polyimide film; the specific steps are: (a) dissolving monomeric diamine and plasticizer in a polar aprotic solvent, adding dianhydride in an equimolar ratio to diamine, mixing for 2-20 hours, and synthesizing a polyamic acid solution containing plasticizer; Wherein the addition amount of plasticizer is 0.05%-5% to the mass percentage of synthetic polyamic acid; (b) Apply the above-mentioned polyamic acid solution containing plasticizer evenly on a glass plate, put it into a vacuum drying oven and heat it up to 200°C to 400°C to obtain a dimensionally stable polyamic acid for flexible printed circuit boards. imide film. 2. The preparation method of polyimide film according to claim 1, characterized in that the plasticizer is phthalates, terephthalates, dibasic acid esters, alkyl sulfonate , Epoxy esters, chlorinated paraffins or phosphate esters. 3. The preparation method of polyimide film according to claim 1, wherein the plasticizer is triphenyl phosphate, triphenyl phosphite, triethyl phosphate, tricresyl phosphate, alkylsulfonic acid Phenyl esters, dioctyl phthalate, dibutyl phthalate, or diisooctyl terephthalate. 4. The method for preparing polyimide film according to claim 1, characterized in that the added plasticizer is 0.05%-2% of the mass percentage of the synthetic polyamic acid. 5. The method for preparing polyimide film according to claim 1, characterized in that the temperature is programmed to rise to 250°C-400°C. 6. The preparation method of polyimide film according to claim 1, characterized in that the polar aprotic solvent is N, N-dimethylformamide, N, N-dimethylacetamide or N-formaldehyde Base-pyrrolidone. 7. The method for preparing polyimide film according to claim 1, characterized in that the diamine is an aromatic diamine. 8. The preparation method of polyimide film according to claim 7, characterized in that the aromatic diamine is 4,4'-diaminodiphenyl ether, bis(3-aminophenoxy)diphenyl sulfone, 1,3-bis(3-aminophenoxy)benzene, diaminodiphenylsulfone, diaminobenzophenone, diaminobenzene or diphenylaminomethane. 9. The method for preparing polyimide film according to claim 1, characterized in that the dianhydride is an aromatic dianhydride. 10. The preparation method of polyimide film according to claim 9, characterized in that the aromatic dianhydride is pyromellitic dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic dicarboxylic acid anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, bisphenol A dianhydride or benzophenone tetracarboxylic dianhydride.