JPS6149499A - Flexible multilayer circuit 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] [Industrial application field] It relates to a pull multilayer wiring board.

[Conventional technology]

Multilayer wiring boards have conventionally been used in various electronic devices.

In such conventional multilayer wiring boards, the conductive patterns in each layer are interconnected by copper plating through holes.

[Problem that the invention seeks to solve]

By the way, what is the conductivity of each layer in a flexible multilayer wiring board? When through-holes are copper-plated to connect turns to each other, there is an inconvenience that the flexibility, which is a characteristic of the through-holes, is significantly impaired. There is a problem in that when the film (cover film) is thermocompressed (hot pressed), the copper plating of the through hole may be significantly damaged.

In view of this point, the present invention aims to improve the above-mentioned disadvantages.

[Failure to solve the problem]

The required conductive patterns (lb) and (2b) are formed on the flexible supports (1m) and (2a), respectively, and further conductive patterns (lb) and (2b) are formed on the conductive patterns (1b) and (2b), respectively. Provided are first and second flexible wiring boards (1) and (2) provided with insulating films (LC) and (2c) except for the interconnection portions of 2b), and the first and second flexible wiring boards (1)
and (2) press-bond the first and second flexible wiring boards (1) and (2) via an insulating adhesive (3) containing conductive particles (3a) between them. The second flexible wiring boards (1) and (2) are bonded together with an adhesive, and the conductive patterns (1b) and (2b) of the first and second flexible wiring boards (1) and (2) are
) are electrically connected to each other by the conductive particles (3a).

[For production]

According to the present invention, the first and second flexible wiring (conductive patterns (1b) and (1) of the wiring boards (1) and (2), respectively
Since the interconnection parts 2b) are electrically connected by conductive particles (3a), there is no need to impair the flexibility of the flexible multilayer wiring board.It can be effectively used in parts of electronic devices that require flexibility. . Further, according to the present invention, the first and second
In the process of bonding the flexible wiring boards (1) and (2), the first and second flexible wiring boards (
1) and (2) conductive/mother turns (1b) and (2b)
The interconnects can be electrically connected.

〔Example〕

Hereinafter, one embodiment of the flexible multilayer wiring board of the present invention will be explained with reference to FIGS. 1 and 2.

In Figures 1 and 2, (1) and (2) respectively indicate flexible wiring boards;
1) and (2) are flexible supports (lB) made of polyimide, polyester, etc. with a thickness of, for example, 25 μm;
(2a) A copper foil having a thickness of, for example, 18 μm or 35 μm is placed on top of the adhesive (ld), (2d) (this adhesive (xd
), the layer (2d) is deposited with a thickness of about 10 μm),
Pattern printing and etching are performed on this to form the required conductive pattern (lb).

(2b), and further this conductive pattern (lb), (
2b) through-holes (1e), (
2e) an insulating film (le) made of polyimide, polyester, etc. having a thickness of, for example, 25 μm, and (2c) an adhesive (If).

(2f) (The layer of adhesive (If) and (2f) is about 10 μm). In this case, the flexible support (la), (2a) has a land portion,
Conductive i4 turns (1b) for terminals, parts mounting parts, etc.
The exposed portion (zb) is formed in a conventional manner.

In this example, this flexible wiring board (1) and (
2) through holes (1e) and (2) at respective predetermined positions.
The insulating films (1c) and (2c) having the insulating films (1c) and (2c) having the solder metal particles (3a) are made to face each other, and the flexible wiring board (1) is bonded by thermocompression via the adhesive sheet S having the solder metal particles (3a).
and (2) are glued.

The adhesive sheet S described below was used. That is, the composition of the insulating adhesive (3) of this adhesive sheet S was as follows.

This adhesive sheet S has a solid content of 1 of this insulating adhesive (3).
00 parts by volume, 12 parts of solder metal particles (3a) (Pb-8m alloy, melting point 230°C) with an average particle diameter of 40 μm
The volumetrically mixed and dispersed mixture is formed into a sheet having a predetermined thickness, for example, such that the thickness of the insulating adhesive (3) after drying is 30 μm. In this case, the insulating adhesive (3) of the adhesive sheet S is melted by heating.

When the flexible wiring boards (1) and (2) are heated to a predetermined temperature and pressed to a predetermined pressure via the adhesive sheet S, the solder metal particles (3a) between the insulating films (1c) and (2c) are The conductive pattern (1b) of this insulating film (le) and (2c) deforms into a flat shape.
Through hole (1) corresponding to the interconnection part (2b)
The upper and lower parts of the solder metal particles (3&) present in e) and (2e) are directly applied to the conductive patterns (1) and (2) of the flexible wiring boards (1) and (2), excluding the insulating adhesive (3).
1b) and (2b), the interconnecting parts of the conductive patterns (1b) and (2b) are electrically connected, and the other parts are adhered to the insulating adhesive (3). .

According to this example, the interconnections of the conductive patterns (1b) and (2b) of the flexible wiring boards (1) and (2) are connected in a spot-free manner by the solder metal particles (3a). To obtain a multilayer wiring board that fully satisfies the inherent characteristics (flexibility) of a flexible multilayer wiring board without impairing its flexibility, and can be effectively used in parts of electronic equipment that require flexibility. Also, according to this example, in the process of bonding these two flexible wiring boards (1) and (2), the conductive A turns (1b) and (2b) of the flexible wiring boards (1) and (2) are bonded simultaneously.
) are electrically connected, which has the advantage of simplifying the manufacturing process.

In this example, conductive patterns (1b) and (2b)
Through-holes (1
e) and (2e), the effective area of the conductive part can be made larger with the same space compared to the conventional method that relies on plating on the inner periphery of the through hole, so this electrical connection can be made much easier. There is a benefit of improved reliability.

FIG. 3 shows another embodiment of the invention. This example in Figure 3 is the flexible wiring board (1) in the examples in Figures 1 and 2.
or (2). In the example in Figure 3, the insulating film (IC) on the conductive pattern (lb) of the flexible wiring board (1) is removed, and even in this case, the conductive pattern (1b) is ) and (2b) are insulated by an insulating film (2c), and the conductive pattern (
The electrical connection of the interconnections of 1b) and (2b) is made via through-holes (2e). The rest of the structure is the same as in FIGS. 1 and 2.

In FIG. 3, the same effects as in FIGS. 1 and 2 can be obtained, and there is also the advantage that the insulating film (IC) can be removed.

In the above-mentioned embodiment, an example was described in which two layers of flexible wiring boards were provided, but it is easily understood that a plurality of layers, such as three layers, four layers, etc., can be provided in the same manner. Further, in the above example, an insulating adhesive containing solder metal particles (3a) was used, but it goes without saying that other conductive particles can be used in place of the solder metal particles (3a). Furthermore, it goes without saying that the present invention is not limited to the above-described embodiments, and can take various other configurations without departing from the gist of the present invention.

〔Effect of the invention〕

According to the present invention, flexible wiring boards (1) and (2)
Since the interconnection parts of the respective conductive patterns (1b) and (2b) are electrically connected by the solder metal particles (3a), the flexibility of the flexible multilayer wiring board is not impaired and the original flexibility of the flexible multilayer wiring board is maintained. A multilayer wiring board that fully satisfies the characteristics (flexibility) can be obtained, and can be effectively used in electronic circuits that require flexibility. Further, according to the present invention, the interconnection portions of the conductive patterns of the flexible wiring boards are electrically connected at the same time in the process of bonding a plurality of flexible wiring boards, so the manufacturing process is simplified and the manufacturing process is easy. There is.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of a flexible multilayer wiring board according to the present invention, FIG. 2 is an exploded cross-sectional view of FIG. 1, and FIG. 3 is an exploded cross-sectional view showing another embodiment of the present invention. (1) and (2) are flexible wiring boards, (la
) and (2a) are respectively flexible supports, (1b) and (2b) are respectively conductive patterns, (1c) and (2c)
(le) and (2e) are through holes, (3) is an insulating adhesive, (3a) is a solder metal particle, and S is an adhesive sheet.

Claims (1)

[Claims] First and second flexible wiring boards each having a required conductive pattern formed thereon are provided on a flexible support; An insulating film is provided on one of the first and second flexible wiring boards, and the first and second flexible wiring are interposed between the first and second flexible wiring boards via an insulating adhesive containing conductive particles. The substrates were crimped, and the first and second flexible wiring boards were bonded together with an adhesive, and the interconnection portions of the conductive patterns of the first and second flexible wiring boards were electrically connected by the conductive particles. A flexible multilayer wiring board characterized by: