JPS6125835A - Flexible printed wiring board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to flexible printed wiring boards used in various electronic devices.

BACKGROUND TECHNOLOGY AND PROBLEMS Generally, a 7-lexiple printed wiring board is used as an individual wiring cable between rigid printed wiring boards, in which electrical wiring is adhered to a base film made of a flexible insulating film using a metal conductor. In recent years, it has become common practice to mount semiconductor devices, resistors, capacitors, etc. on such flexible printed wiring boards by soldering them. As a flexible base film for flexible printed wiring boards to which such semiconductor devices, resistors, capacitors, etc. are soldered, a resin with good heat resistance, such as the ability to withstand temperatures of 260°C or higher during soldering, is required. . Polyimide resins having a general structural formula are used as such resins with good heat resistance. When polyimide resin having this structural formula (1) is used as a base film, it has high heat resistance, but this flexible printed wiring board (1)
When mounting the board by folding it as shown in Figures 1 and 2 (flexible printed circuit boards are often used by folding them in narrow spaces), this structural formula Printed wiring board (1
1 has a limit to the curvature of the bent part due to its rigidity, and cannot be mounted in a narrow space.Also, as shown in Figure 2, this flexible printed wiring board (1) is connected to the rigid printed wiring board (2) by bending it. When this occurs, stress is applied to the connection portion due to this repulsive force, and there is a risk that the connection at this portion may become defective. As shown in Figure 3, a wiring pattern (lb) is formed on a polyimide resin base film (Ia) of structural formula (1).
When the polyimide resin coverlay film (1c) having the structural formula flJ was applied thereon, the above-mentioned disadvantages were further exacerbated. In this case, it is conceivable to thermoform this flexible printed wiring board (1) by applying heat to, for example, about 280°C, but this structural formula (1)
The polyimide resin had no glass transition temperature and could not be thermoformed.

OBJECTS OF THE INVENTION In view of the above, an object of the present invention is to provide a flexible printed wiring board that has good heat resistance and can be thermoformed.

Summary of the Invention The present invention is a flexible printed wiring board using a polyimide base film having a glass transition point of 260°C to 300"C, which has good heat resistance and can be thermoformed. Since it is easy to bend, it can be mounted in narrow spaces.

EXAMPLES Hereinafter, examples of the flexible printed wiring board of the present invention will be described with reference to the drawings.

Example 1 As a base material for the base film (la) and coverlay film (1c) in FIG. It is a condensation product.

...(2) A polyimide resin having the structural formula was used. The glass transition temperature of the polyimide resin having this structural formula (2) is 2
It is 05℃.

A flexible printed wiring board (11) as shown in FIG. 3 was formed using a base film (la) and a cover film (lc) made of a polyimide resin having the structural formula (2).Such a flexible printed wiring board (1) Using a 280'C @ degree pot plate as shown in Fig. 4 with K, we tested the bending properties and found that thermoforming was possible up to a bending radius R of about 11III as shown in Fig. 5, and it could be used in narrow spaces. Although mounting was possible, the heat resistance was not very good when immersed in a 260° C. solder bath for 30 seconds.

Example 2 As a base material for the base film (la) and coverlay film (Ic) shown in Figure 13, the structural formula of the polycondensation product obtained by adding 4,4-diaminodiphenyl ether to biphenyltetracarboxylic dianhydride was used. A polyimide resin having the following properties was used. The glass transition temperature of the polyimide resin having this structural formula (3) is 285°C.

A flexible printed wiring board (1) as shown in FIG. 3 was formed using a base film (la) and a cover film (1c) made of a polyimide resin having the structural formula (3). The flexible printed wiring board (1) with K was tested for bending properties using a hot plate at 280°C as shown in Figure 4, and it was found that thermoforming was possible to a bending radius R of approximately IW as shown in Figure 5. It was possible to implement it in a narrow space. The heat resistance was also good when it was immersed in a solder bath at a temperature of 30°C for 30 seconds.

Example 3 As a base material for the base film (1a) and coverlay film (1c) in FIG. 3, 2.
A polyimide resin having the structural formula (4), which is a polycondensation product with the addition of 2-bis(4-(4-aminophenoxy)phenyl)propane, was used. The glass transition temperature of polyimide resin is 3
The temperature is 50°C.

A flexible printed wiring board +11 as shown in FIG. 3 was formed using a base film (la) and a cover film (1c) made of a polyimide resin having the structural formula (4). 2 per such flexible printed wiring board (1)
When immersed in a solder bath at 60°C for 30 seconds, the heat resistance was good, but when tested for bending properties using a hot plate at about 280°C as shown in Figure 4,
Thermoforming could only be performed up to a bending radius R of about 3 - as shown in the figure, and mounting in a narrow space was not very good.

Comparative Example 1 As a base material for the base film (la) and coverlay film (1c) in FIG. 3, 4.
A polyimide resin having the structural formula +1), which is a condensation product with the addition of 4-diaminodiphenyl ether, was used. The polyimide resin having this structural formula (1) has no glass transition temperature.

A flexible printed wiring board (1) as shown in FIG. 3 was formed using a base film (1a) and a cover film (1c) made of a polyimide resin having the structural formula (1). 2 per such flexible printed wiring board (1)
When immersed in a solder bath at 60°C for 30 seconds, the heat resistance was good, but when the bending characteristics were tested using a hot plate at about 280°C as shown in Figure 4, the bending radius was as shown in Figure 5. Thermoforming was only possible up to an R of about 9W, making it impossible to mount it in a narrow space.

Comparative Example 2 Polyethylene terephthalate (polyethylene terephthalate) was used as the base material for the base film (LA) and coverlay film (IC) in Figure 3.
(PET) to form a flexible printed wiring board (1) as shown in FIG. When testing the bending properties of the flexible printed wiring board (1) using a hot plate at about 280°C as shown in Fig. 4, it was possible to thermoform the board to a bending radius R of about 1s11 as shown in Fig. 5. When it was immersed in a 260°C solder bath for 30 seconds, it had poor heat resistance and was unusable.

Based on the above, polyimide resin having a glass transition temperature in the vicinity of 260°C to 300°C is used as the base material for the base film (Ia) and coverlay film (1c) in Fig. 3. (When 11 is formed, it can be thermoformed at around 280℃, is easy to bend, can be mounted well in a bent state, and is a flexible material with heat resistance that can withstand soldering. A printed wiring board (11) can be obtained.

In addition, in the above-mentioned example, the coverlay film (1c)
I have described an example in which this coverlay film (
Of course, the present invention can also be applied to flexible printed wiring boards that do not have ICs. Further, the present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

Effects of the Invention According to the present invention, thermoforming is possible at around 280°C, bending is easy, mounting can be performed well in a bent state, and heat resistance that can withstand soldering etc. It is advantageous to be able to obtain a flexible printed wiring board with

[Brief explanation of drawings]

FIG. 1, FIG. 2, FIG. 4, and FIG. 5 are diagrams for explaining the present invention, respectively, and FIG. 3 is an exploded perspective view showing an example of a flexible printed wiring board. (1a) is a base film, (1b) is a wiring turn, and (IC) is a coverlay film. Hidemori Matsukuma (1':
T 'j-,,: "・Kotoyama: 4' -F continuation?ii Original book September 40, 1982 Patent application No. 147411 2°' Akio
s +tr 7-Wow5. 13th Spring, Board 3, Relationship with the amended person's case Patent applicant address 6-7-35, Kitashina, Tokyo Parts Store Name (2
1B) Norio Ohga, Representative Director of Sony Corporation 4, Agent address: 1-8-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo. Location 03-343-5B21fl15 (Shinjuku Hill)
6. The number of inventions will increase due to the amendment.In the specification, page 4, line 9, stomach is corrected to [E]. (2) Same, page 6 lines 11-12 and page 7 lines 15-1
In line 6, the words "pyromellitic anhydride" should be corrected to "pyromellitic anhydride."that's all

Claims (1)

[Claims] A flexible printed wiring board characterized in that a base film is made of polyimide having a glass transition point of 260°C to 300°C.