JPH04162491A - Flexible printed board and its manufacture - Google Patents

Abstract

PURPOSE:To improve heat resistance electric characteristics, mechanical proper ties and economical efficiency by laminating a base film layer made of polyim ide resin, a middle layer made of thermoplastic polyimide resin and a conductive layer. CONSTITUTION:A flexible printed board is composed of a base film layer made of polyimide resin, a middle layer made of thermoplastic polyimide resin which has the unit structure expressed by a formula I, and a conductive layer. The precursor solution of the thermoplastic polyimide resin expressed by the formula I is coated on the base film layer made of polyimide, dried and permitted to be imide. Then, the substrate is formed by hot pressing with the conductive layer.

Description

Detailed Description of the Invention [Industrial Application Technique] The present invention provides a flexible printed circuit board that is composed of a polyimide layer, a thermoplastic polyimide layer, and a conductor layer and has excellent heat resistance, electrical properties, mechanical properties, and economic efficiency. and its manufacturing method.

[Conventional technology]

In recent years, electronic devices have been on the path to becoming smaller and lighter in line with user needs. Therefore, regarding the electronic components or wiring materials used therein, it is natural that
There is a demand for smaller size and higher density. Flexible printed circuit boards, which are thinner and softer than rigid printed circuit boards, are no exception.

Flexible printed circuit boards currently in use are generally manufactured by bonding metal foil such as copper foil and insulating film such as organic polymer with adhesive, and the adhesive used in this case is acrylic or epoxy. etc. are used. For this reason, the heat resistance of the entire flexible printed circuit board is determined by the heat resistance of the adhesive, and the excellent heat resistance, flame retardance, etc. of the polyimide heath film cannot be fully demonstrated.

As a method to improve these problems, Japanese Patent Application Laid-Open No. 60-17547
8 and JP-A No. 61-98782, and symmetric aromatic meta-substituted primary amines and symmetric aromatic aromatics as disclosed in JP-A No. 62-208690. There is a method using a copolymer using a group para-substituted primary amine. Further, as an improvement to the manufacturing method, Japanese Patent Application Laid-Open No. 62-104840 discloses an example in which a thermoplastic polyimide film is used as an adhesive layer. However, the reality is that a flexible printed circuit board that is excellent in heat resistance, electrical properties, mechanical properties, and economic efficiency has not yet been proposed.

[Problem to be solved by the invention]

〉The invention was made in view of the above-mentioned circumstances, and the present invention provides a flexible printed circuit board that uses a thermoplastic polyimide layer as an adhesive layer and has excellent heat resistance, electrical properties, mechanical properties, and compatibility with bathing and other purposes. The purpose is to provide a manufacturing method.

[Means to solve the problem]

The present inventors conducted intensive research to solve the above problems, and as a result, they arrived at the present invention.゛That is,
The first aspect of the present invention is a base film layer made of a polyimide resin, and a compound having the general formula (I) (wherein R1 is -C-, -O-, -S-).

CF3 CH: At least one group selected from lCH, CH3 direct bond. R2 is CH,
At least one group selected from CF3 0 or directly connected. ) The second aspect of the present invention is to provide a base film layer made of a polyimide resin with a flexible printed group consisting of an intermediate layer made of a thermoplastic polyimide resin having a unit structure represented by the formula (I) and a conductor layer. ) (wherein, R3 is -C-, -O-, -S-.

At least one group selected from F 3 directly connected. R2 is at least one group selected from or directly bonded. ) A method for manufacturing a flexible printed circuit board, characterized in that the thermoplastic polyimide resin precursor solution shown in (1) is applied, dried, imidized, and then heated and pressurized with a conductive layer. It is.

Used as a hair film layer in the present invention"
The polyimide resin used for rAl is not particularly limited as long as its glass transition temperature is higher than the glass transition temperature of the thermoplastic polyimide resin used for the intermediate layer, and specific examples include polyamideimide, polyetherimide, polyesterimide, and other copolymers and monomers. Examples include polyimide modified by modification of
Preferred is a polyimide represented by the general formula (II) which is flexible and has a linear expansion coefficient close to that of metal. In general formula (II), m is 100-10000, n is 100-1000
0 and m/n is preferably 1 to 5.

The polyimide represented by the general formula (n) can be obtained by imidizing its precursor, polyamic acid. This polyamic acid can be obtained by reacting phenylene diamine and 4,4'-diaminodiphenyl ether with pyromellitic dianhydride.

The thermoplastic polyimide used as the intermediate layer in the present invention is
Although it exhibits thermoplasticity due to the introduction of a bending group, it does not have a meta-substituted structure and maintains heat resistance. Specifically, it has the general formula (I
) has the structure shown in

Here, as a specific example of R1, CF3 0 CH3CH, CH.

etc. can be mentioned.

Specific examples of R2 include CH3CF3CH, CF3-3-1, or a direct connection. - The thermoplastic polyimide resin represented by formula (I) is, for example, (2,2-bis(4-(
4-aminophenoxy)phenyl]propane) and (2,
2-bis[4-(4-aminophenoxy)phenyl]sulfone and 3.3'.

It can be obtained by reacting 4.4'-henzuphenone tetrasulfoxy dianhydride F and the like. Furthermore, other thermoplastic resins may be partially copolymerized or blended.

Thermoplastic polyimide is obtained by a dehydration ring-closing reaction of its precursor, polyamic acid. 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.

Are there any compounds used during polymerization reactions? As a tr medium, N is used.

N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, N.

Examples include N-diethylacetamide, N,N-dimethylmethoxyacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, tetrahydrofuran, and pyridine, and these solvents may be used alone or in combination of two or more.

Polyamic acid, which is a thermoplastic polyimide precursor, has 5 to 4
It is dissolved in a concentration of 0% by weight and coated on a polyimide film as a base film to a uniform thickness of 30 to 500 μm using a blade coater, knife coater, rotary coater, etc. Subsequently, it is heated and dried and then imidized. The temperature at this time is preferably 80 to 250°C, and 100 to 200°C.
°C is more preferred. At this time, if a chemical ring-closing agent or the like is added, the imidization time can be shortened and workability can be improved.

Next, conductor layers are laminated and heated and pressurized. As the method of heating and pressing, a method using a press or a roll can be used.

The heating temperature is desirably higher than the softening point of the thermoplastic polyimide and lower than the thermal decomposition temperature of the polyimide of the base film. The heating method may be continuous or stepwise, and the pressure is 1
00 kgf/cffl or less is preferable.

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

The metal foil may be mechanically or chemically surface treated by sanding, nickel plating, or aluminum alcoholade, aluminum chelate, silane coupling agent, or the like.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these examples.

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

Beer strength: Beer strength at high temperatures was measured by placing the beer in a constant temperature bath at a predetermined temperature for 30 minutes in accordance with the method of JIS C5016.

Line insulation resistance: Measurement was performed according to JIS C5016.

Volume resistivity: Measurement was performed according to JIS C6481.

Dielectric constant: Measurement was performed according to JIS C6481.

Water absorption rate: Measurement was performed according to JIS C5016.

Example 1 0DA (4,
4'-diaminodiphenyl ether) was dissolved, and PMDA (pyromellitic dianhydride) 1 was dissolved therein.
After adding 02.07 g of p-PDA and stirring for 1 hour,
Add about 12.65 g (para-phenylenediamine),
The viscosity was adjusted to 2500 poise. ODA:
p-PDA=3:1.

After casting this polyamic acid solution, 80°C110
0°C, 150°C, 200°C, 250'C, 300
The mixture was dried and imidized by heating at 1350°C, 1400°C, and 450°C for 5 minutes each. This was used as a base film (thickness: 2511 m).

Next, 244.5 g of N,N-dimethylborumami F'
to BAPP (2,2-bis(4-(4-aminophenoxy)phenyl)propane 31.), and here BTDA (3,3',4,4'-henzphenonetetrapower report). xydianhydride) 24.41
g and stirred for 1 hour. The viscosity of this polyamic acid solution was 600 poise. This polyamic acid solution was applied to the above base film and heated at 80°C 1100°C.
The mixture was dried and imidized by heating at 150°C and 1200°C for 5 minutes each.

Copper foil (35 μm) was superimposed on the obtained film and heated and pressed using a pot press. Pressing conditions are 300°C
, 30 minutes at 50 kg/c. The properties of the obtained flexible printed circuit board were as shown in Table 1.

Example 2 BAP to 244.5 g of N,N-dimethylformamide
S (2,2-bis[4-(4-aminophenoxy)phenyl]sulfone 131.8g was dissolved, and BT
23.7 g of DA was added and stirred for 1 hour. The viscosity of the solution was 400 poise.

This polyamic acid solution was applied to the base film used in Example 1 at 80°C, 1100°C, 1150'C, and
The mixture was dried and imidized by heating at 0°C for 5 minutes each.

The obtained film was placed on a copper foil (35 μm) and heated and pressed using a pot press machine. Press conditions are 300
30 minutes at 850 kg/c sheath.

The properties of the obtained flexible print 1 substrate were as shown in Table 1.

Comparative Example 1 The base film used in Example 1 and copper foil were bonded together using an epoxy adhesive to create a flexible printed circuit board. The characteristics are shown in Table 1.

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 has excellent heat resistance, electrical properties, and mechanical properties. A flexible printed circuit board with excellent properties can be manufactured economically.

Patent applicant Kanebuchi Chemical Industry Co., Ltd.

Claims (1)

[Claims] 1. A base film layer made of polyimide resin and a general formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R_1 is ▲There are mathematical formulas, chemical formulas, tables, etc.▼), or at least one type selected from direct connection. Group.R_2 can be selected from ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, -O-, -S-, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, or directly connected A flexible printed circuit board comprising a conductor layer and an intermediate layer made of a thermoplastic polyimide resin having a unit structure represented by: 2. 2. The flexible printed circuit board according to claim 1, wherein the polyimide resin as the base film layer has a unit structure represented by the general formula (II) ▲A mathematical formula, a chemical formula, a table, etc.▼. 3. Claim 2, wherein m/n of general formula (II) is a value of 1 to 5.
The flexible printed circuit board described. 4. The flexible printed circuit board according to claim 1, wherein the conductor layer is a copper foil. 5. The base film layer made of polyimide resin has the general formula (I) ▲Mathematical formula, chemical formula, table, etc.▼ (In the formula. R_1 has ▲Mathematical formula, chemical formula, table, etc.▼,
-O-, -S-, ▲There are mathematical formulas, chemical formulas, tables, etc.▼,
or at least one group selected from directly connected. R_2 is ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, -O-, -S-, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, or at least one selected from direct connections One type of group. ) A method for producing a flexible printed circuit board, comprising applying a precursor solution of a thermoplastic polyimide resin, drying and imidizing the resin, and then heating and pressurizing it with a conductor layer. 8. 6. The manufacturing method according to claim 5, wherein the conductor layer is a copper foil.