JP3076060B2 - Flexible printed circuit board and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Technology] The present invention comprises a base film layer and a conductor layer made of thermoplastic polyimide, and has excellent heat resistance, electrical properties and mechanical properties, and production of the same. About the method.

[Conventional technology]

2. Description of the Related Art In recent years, electronic devices have been on the road to miniaturization and weight reduction according to user needs. Therefore, the electronic components or wiring materials used therein are also required to be reduced in size and, of course, to have higher density. There is no exception for a flexible printed circuit board which is thinner and softer than a rigid printed circuit board, and the importance of a double-sided board and a multilayer board is increasing, and the importance thereof is increasing.

A flexible printed circuit board currently used is generally manufactured by bonding a metal foil such as a copper foil and an insulating film such as an organic polymer with an acrylic or epoxy adhesive. Therefore, the heat resistance of the flexible printed circuit board is affected by the adhesive, and the polyimide base film cannot exhibit the excellent heat resistance, flame retardancy, and the like inherent to the polyimide base film.

Therefore, a flexible printed circuit board having no adhesive layer is being studied, for example, Japanese Patent Application Laid-Open No. 58-199001,
JP-A-58-190092 and the like. However, a flexible printed circuit board having sufficient heat resistance and adhesiveness has not been obtained.

In addition, there is a method of obtaining a flexible printed board by casting a polyimide precursor solution on a metal foil. However, when this method is used, a multilayer flexible printed board cannot be obtained in principle.

[Problems to be solved by the invention]

The present invention has been made in view of the above problems,
The object of the present invention is to eliminate the adhesive layer contained in the conventional flexible printed circuit board, having an insulating layer and a conductor layer made of thermoplastic polyimide, excellent in heat resistance, electrical properties and mechanical properties, double-sided and multi-layered The present invention relates to a flexible printed board and a method for manufacturing the same.

[Means for solving the problem]

The present inventors have conducted various studies in order to solve the above problems, and as a result, completed the present invention.

"That is, a first aspect of the present invention is to provide a conductive layer having the following general formula [I]
A flexible printed circuit board having a unit structure represented by and having a thermoplastic resin insulating layer having a glass transition temperature of 200 ° C. or higher alternately laminated, wherein the conductor layer and the insulating layer are each at least one layer. It is assumed that.

(Where R ₁ is -O-, -S-, At least one group selected from direct connection. R ₂ is Or at least one group selected from the group consisting of: A second aspect of the present invention is to apply a precursor solution of a thermoplastic polyimide resin having a unit structure represented by the following general formula [I] and having a glass transition temperature of 200 ° C. or more to the conductor layer, followed by drying and drying. Manufacturing of a flexible printed circuit board characterized by laminating at least one kind of a circuit formed on a conductor layer by imidization, laminating a conductor layer on the outermost thermoplastic polyimide resin layer, and then heating and pressing. The contents of the method.

(Where R ₁ is -O-, -S-, At least one group selected from direct connection. R ₂ is Or at least one group selected from the group consisting of: The thermoplastic polyimide resin used in the present invention requires a glass transition temperature of 200 ° C. or higher for the heat resistance of the flexible printed circuit board. Specifically, the thermoplastic polyimide resin is represented by the following general formula [I]: It is preferable to use polyimide from the balance between heat resistance and adhesiveness.

Here, specific examples of R ₁ include, for example, Or direct connection can be mentioned.

Specific examples of R ₂ include, for example, -O-, -S-, Or direct connection can be mentioned. The number of repetitions of the general formula [I] is preferably from 100 to 10,000.

Thermoplastic polyimide is obtained by a dehydration ring closure reaction of a polyamic acid as a precursor. This polyamic acid can be synthesized by a conventionally known method, that is, by polymerizing the corresponding diamine and tetracarboxylic dianhydride in an equivalent ratio of 1: 1. For example {2,2-bis [4- (4-aminophenoxy) phenyl] propane}
And 2,3-bis [4- (4-aminophenoxy) phenyl] sulfone or the like and 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride or the like.

Organic solvents used in the polymerization reaction include N, N-dimethylformamide, N, N-dimethylacetamide, N, N
-Diethylformamide, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, tetrahydrofuran, pyridine and the like, and these solvents are used alone or in combination of two or more. .

Polyamic acid, a thermoplastic polyimide precursor,
It is dissolved in the above solvent in an amount of 40% by weight, and is applied to the conductor layer by a blade coater, knife coater, rod coater or the like to a uniform thickness of 30 to 500 μm. Subsequently, it is imidized after drying by heating. The temperature at this time is preferably from 150 to 250 ° C. in order to complete the imidization reaction. A conductor is further laminated thereon and heated and pressed. As a method of heating and pressurizing, a method using a press or a roll can be used. The heating temperature is preferably higher than the softening point of the thermoplastic polyimide and lower than the thermal decomposition temperature. The heating method may be a continuous method or a step method, and the pressure is preferably up to 100 kgf / cm ² in order to prevent embrittlement of the copper foil.

Through the above steps, a double-sided flexible printed board can be obtained. Further, by repeating these series of operations, a multilayer flexible printed circuit board can be produced. Specifically, the layers that have undergone the polyamic acid application step, the imidization step, and the circuit formation step are laminated,
Finally, a multi-layer flexible printed board can be obtained by heating and pressing.

The metal foil used as the conductor layer in the present invention includes copper, aluminum, iron, gold, silver, nickel, chromium, molybdenum, and the like. Copper foil is preferred, and electrolytic copper foil is more preferred in terms of cost and adhesiveness.

The metal foil may be sanded, nickel-plated, or mechanically or chemically surface-treated with aluminum alcoholate, aluminum chelate, silane coupling agent, or the like.

〔Example〕

Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

Various performances as a flexible printed board were measured by the following methods.

Peel strength: The peel strength was measured in accordance with the method of JIS C 5016. The peel strength at a high temperature was measured by placing the sample in a thermostat at a predetermined temperature for 30 minutes.

Line insulation resistance: Measured according to JIS C 5016.

Volume resistivity: Measured according to JIS C 6481.

Dielectric constant: Measured according to JIS C 6481.

Water absorption: Measured according to JIS C 5016.

Example 1 BAPP {2,2-bis [4- (4-aminophenoxy) phenyl] propane} was added to 244.5 g of N, N-dimethylformamide.
31.1 g was dissolved, and BTDA (3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride) 24.4 was added thereto.
1 g was added and stirred for 1 hour. The viscosity of the polyamic acid solution was 600 poise. This polyamic acid solution was added to copper foil (35
μm), heated at 80 ° C., 100 ° C., 150 ° C., and 200 ° C. for 5 minutes each and dried and imidized (film thickness: 15 μm, glass transition temperature: 241 ° C .: DSC, DT- manufactured by Shimadzu Corporation) Evaluated by peak top value using 403). A copper foil was laminated on the polyimide resin layer of the obtained laminate, and was thermally fused by a hot press. The pressing conditions are 300 ° C. and 50 kgf / cm ² . The characteristics of the obtained double-sided flexible printed circuit board are as shown in Table 1.

Example 2 BAPS @ bis [4] was added to 244.5 g of N, N-dimethylformamide.
-(4-aminophenoxy) phenyl] sulfone {3
1.8 g was dissolved, 23.7 g of BTDA was added thereto, and the mixture was stirred for 1 hour. The viscosity of the solution was 400 poise. This polyamic acid solution was applied to a copper foil under the same conditions as in Example 1 and imidized (film thickness 15 μm, glass transition temperature 273 ° C .: evaluated by peak top value using DSC, DT-403 manufactured by Shimadzu Corporation), Further, a copper foil was laminated on the polyimide resin layer to obtain a double-sided flexible printed board. The characteristics of the substrate were as shown in Table 1.

Comparative Example 1 An epoxy adhesive was applied to both sides of a commercially available polyimide film, and copper foil was adhered to both sides to prepare a flexible printed circuit board. The characteristics are shown in Table 1.

[Effects of the Invention] As can be seen from the results in Table 1, the flexible printed circuit board of the present invention is excellent in all of heat resistance, electrical properties, and mechanical properties, and according to the production method of the present invention,
A flexible printed circuit board having excellent heat resistance, electrical properties, and mechanical properties can be manufactured.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05K 3/46 H05K 1/03

Claims (3)

(57) [Claims] A conductive layer having a unit structure represented by the following general formula [I] and a thermoplastic polyimide resin insulating layer having a glass transition temperature of 200 ° C. or higher: And a flexible printed circuit board having at least one insulating layer. (Where R ₁ is -O-, -S-, At least one group selected from direct connection. R ₂ is Or at least one group selected from the group consisting of: ) 2. A precursor solution of a thermoplastic polyimide resin having a unit structure represented by the following general formula [I] and having a glass transition temperature of 200 ° C. or higher is applied to the conductor layer, dried and imidized. A method of manufacturing a flexible printed circuit board, comprising laminating at least one kind of circuit formed on a conductor layer, laminating one conductor layer on the outermost thermoplastic polyimide resin layer, and then heating and pressing. (Where R ₁ is -O-, -S-, At least one group selected from direct connection. R ₂ is Or at least one group selected from the group consisting of: ) 3. The method according to claim 2, wherein the conductor layer is a copper foil.