JPH0464199B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a flexible multilayer wiring board used in various electronic devices.

[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]

However, when copper plating is used to connect the conductive patterns of each layer in a flexible multilayer wiring board, there is an inconvenience that the flexibility, which is a characteristic of the board, is significantly impaired. Furthermore, due to the structure of the flexible multilayer wiring board, there was a problem in that when insulating films (cover films) were thermocompression bonded (hot pressed) to the front and back surfaces of the flexible multilayer wiring board, the copper plating of the through holes could be significantly damaged.

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

[Means for solving problems]

In the flexible multilayer wiring board of the present invention, as shown in FIG. 1, required conductive patterns 1b and 2b are formed on flexible supports 1a and 2a, respectively, and conductive patterns 1b and 2b are formed on these conductive patterns 1b and 2b, respectively.
First and second flexible wiring boards 1 and 2 are provided with insulating films 1c and 2c having through holes 1e and 2e at positions corresponding to the interconnection parts of 2b, and the first and second flexible wiring boards The first and second flexible wiring boards 1 and 2 are crimped together via an insulating adhesive 3 containing conductive particles 3a between the first and second flexible wiring boards 1 and 2. conductive patterns 1b and 2b of the first and second flexible wiring boards 1 and 2.
The interconnection portions of the conductive particles 3a are electrically connected to each other by the conductive particles 3a.

[Effect]

According to the present invention, the conductive patterns 1b and 2 of the first and second flexible wiring boards 1 and 2, respectively.
Since the interconnection parts b are electrically connected by the conductive particles 3a, the flexibility of the flexible multilayer wiring board is not impaired and it can be effectively used in parts of electronic equipment that require flexibility. Further, according to the present invention, in the step of bonding the first and second flexible wiring boards 1 and 2, the conductive patterns 1b of the first and second flexible wiring boards 1 and 2 are bonded together.
and 2b can be electrically connected.

〔Example〕

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

In FIGS. 1 and 2, 1 and 2 indicate flexible wiring boards, respectively, and these flexible wiring boards 1 and 2 are made of flexible supports 1a and 2a made of polyimide, polyester, etc. and having a thickness of, for example, 25 μm.
A copper foil having a thickness of, for example, 18 μm or 35 μm is adhered thereon using adhesives 1d and 2d (the layers of adhesives 1d and 2d are approximately 10 μm), and pattern printing and etching are performed on this to form the required conductive pattern 1b. , 2b, and further has through holes 1e, 2e on the conductive patterns 1b, 2b at portions corresponding to the interconnections of the conductive patterns 1b, 2b. 1c and 2c are adhered with adhesives 1f and 2f (layers of adhesives 1f and 2f have a thickness of about 10 μm). In this case flexible support 1
Exposed portions of conductive patterns 1b and 2b such as land portions, terminal portions, and component mounting portions are formed on a and 2a in the same manner as in the conventional art.

In this example, through holes 1e and 2 are provided at predetermined positions in the flexible wiring boards 1 and 2, respectively.
The adhesive sheet S has solder metal particles 3a with the insulating films 1c and 2c sides facing each other and having solder metal particles 3a.
This flexible wiring board 1 is bonded by thermocompression through
and 2 are glued together.

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.

Acrylic rubber (manufactured by Teikoku Kagaku Co., Ltd., Teisan Rubber #5001)...45 parts by weight Epoxy resin (manufactured by Nippon Ciba Geigy Co., Ltd.,
GY260)...50 parts by weight Polyvinylphenol (manufactured by Maruzen Oil Co., Ltd., Resin M)...4.5 parts by weight Undeciimidazole (Shikoku Huain Chemical Co., Ltd.)...0.5 parts by weight MEK...100 parts by weight Toluene...100 parts by weight Ethanol...50 parts by weight This adhesive sheet S is prepared by mixing and dispersing 12 parts by volume of solder metal particles 3a (Pb-Sn alloy, melting point 230°C) with an average particle size of 40 μm to 100 parts by volume of the solid content of the insulating adhesive 3. For example, 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.

The flexible wiring boards 1 and 2 are heated to a predetermined temperature (at least the temperature at which the insulating adhesive 3 melts or higher) via the adhesive sheet S, and a predetermined pressure is applied (at least under this temperature condition, the solder metal particles 3a
When the solder metal particles 3a between the insulating films 1c and 2c are pressed with a pressure greater than the pressure necessary to deform the insulating films 1c and 2c, the solder metal particles 3a between the insulating films 1c and 2c are flattened and formed through holes corresponding to the interconnections of the conductive patterns 1b and 2b of the insulating films 1c and 2c. Halls 1e and 2e
The upper and lower parts of the solder metal particles 3a present in the conductive patterns 1b and 2 contact directly with the interconnection portions of the conductive patterns 1b and 2b of the flexible wiring boards 1 and 2, excluding the insulating adhesive 3.
The interconnection portion b is electrically connected, and the other portions are bonded to an insulating adhesive 3.

According to this example, since the interconnection portions of the conductive patterns 1b and 2b of the flexible wiring boards 1 and 2 are electrically connected by the solder metal particles 3a, the flexibility of the flexible multilayer wiring board is not impaired. A multilayer wiring board that satisfies the original characteristics (flexibility) of a flexible multilayer wiring board can be obtained.
It can be effectively used in parts of electronic equipment that require flexibility. Further, according to this example, in the process of bonding these two flexible wiring boards 1 and 2, the conductive patterns 1 of these flexible wiring boards 1 and 2 are bonded together.
Since the interconnections b and 2b are electrically connected, there is the advantage that the manufacturing process is simpler. Further, in this example, the through hole 1 is used to electrically connect the interconnection portions of the conductive patterns 1b and 2b.
Since the inside of e and 2e is used, the effective area of the conductive part can be made larger in the same space compared to the conventional one that relies on plating on the inner circumference of the through hole, which has the advantage of improving the reliability of this electrical connection. There is.

FIG. 3 shows another embodiment of the invention. This third
The example shown is one in which the insulating film 1c on the conductive pattern 1b of the flexible wiring board 1 in the example shown in FIG. 3 has been removed from either the flexible wiring board 1 or 2 in the example shown in FIGS. 1 and 2. In this case, insulation between the conductive patterns 1b and 2b is provided by an insulating film 2c, and electrical connection between the conductive patterns 1b and 2b is made via a through hole 2e. The rest of the structure is the same as in FIGS. 1 and 2.

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

In the above embodiment, an example in which two layers of flexible wiring boards were provided was described, but three layers were similarly provided.
It is easily understood that multiple layers, such as four layers, etc., can be provided. Further, in the above example, an insulating adhesive containing solder metal particles 3a was used, but instead of the solder metal particles 3a, conductive particles such as nickel particles, silver particles, or plastic particles plated with nickel or gold may be used. Of course, it can be used. Note that the same effect as in the above embodiment can be obtained not only when the average particle size of the solder metal particles 3a and other conductive particles is larger than the thickness of the insulating adhesive 3, but also when it is the same or smaller than the thickness of the insulating adhesive 3. 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 original characteristics (flexibility) of the flexible multilayer wiring board can be maintained without impairing the flexibility of the flexible multilayer wiring board. A fully satisfactory multilayer wiring board can be obtained and can be effectively used in electronic circuits that require flexibility. Further, according to the present invention, the interconnection parts 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 that the manufacturing process is simplified and there is an advantage that the manufacturing process is facilitated. .

[Brief explanation of drawings]

FIG. 1 is a sectional view showing one embodiment of the flexible multilayer wiring board of the present invention, FIG. 2 is an exploded sectional view of FIG. 1, and FIG. 3 is an exploded sectional view showing another embodiment of the invention. 1 and 2 are flexible wiring boards, 1a and 2a are flexible supports, 1b and 2b, respectively.
1c and 2c are insulating films, 1e 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] 1. First and second flexible wiring boards each having a required conductive pattern formed thereon are provided on a flexible support, and a through-hole is provided at a position corresponding to the interconnection portion of the conductive pattern of the first and second flexible wiring boards. An insulating film provided with a hole is provided on at least one of the first and second flexible wiring boards, and an insulating adhesive containing conductive particles is interposed between the first and second flexible wiring boards. The entire first and second flexible wiring boards are crimped, and the first and second flexible wiring boards are bonded together with an adhesive, and the interconnection portions of the conductive patterns of the first and second flexible wiring boards are bonded together. A flexible multilayer wiring board characterized by electrical connection using conductive particles.