JPS6246080B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a multilayer wiring board having a rigid circuit portion and a flexible circuit portion.

When electrically connecting a rigid wiring board to another wiring board, it is desirable that the connection end be a flexible portion. For example, if a flexible circuit part 2 is laminated on a rigid wiring board 1 as shown in FIG.
There are advantages such as easy and reliable interconnection with the substrates 1 and 4, and a greater degree of freedom in the placement of both substrates 1 and 4. Note that 5 and 6 are circuit patterns of the respective substrates, and 7 is a conductive material such as solder filled through the opening.

The conventional manufacturing method for this type of multilayer circuit board is as follows:
For example, as shown in FIGS. 2A and 2B, a rigid circuit section 10 is formed by forming a first layer circuit 9 on one main surface of a hard Bakelite substrate 8, and a second layer circuit 12 made of copper foil is formed on a polyimide film 11. The formed flexible circuit portions 13 are provided separately, and the connecting portions (openings) of the flexible circuit portions 13 are provided separately.
14 with a drill, apply adhesive 15 to the back side and attach it to the rigid circuit part 10, then fill the connection part 14 with solder 16 and drill a through hole 17 through the connection part of the required circuit. Electrical parts 18
I am trying to connect. Alternatively, as shown in FIGS. 3A and 3B, double-sided circuits 20 and 21 using through-hole plating 19 on polyimide film 11
A flexible wiring board 22 is provided, which is bonded to a hard Bakelite board 8 via an adhesive 15, and then a through hole 17 is drilled through the connection portion of the required circuit to connect the required electrical component 18. I'm trying to connect.

However, in the former case, the accuracy of bonding the rigid circuit portion 10 and the flexible circuit portion 13 is poor (the flexible circuit portion requires drilling before bonding), and the circuit formation of the flexible circuit portion 13 lacks rigidity. The solder connections between the first layer circuit 9 and the second layer circuit 12 are made by manually filling each hole with solder, which is not suitable for mass production. It is difficult to connect the circuits 12, and the hole diameter cannot be made small due to drilling, which increases the area occupied by the circuit 12 and impedes high density.
There are problems such as the inability to create a continuous production process.

In the latter case, the flexible wiring board 2
The manufacturing process of No. 2 is complicated and requires wastewater treatment equipment, which is undesirable; the circuit formation is not rigid, making it difficult to handle; and the holes are drilled into the flexible wiring board, so there is a limit to the hole diameter. However, there were problems such as the difficulty in forming high-density circuits and the inability to create a process with continuous productivity.

The present invention solves the above-mentioned problems and provides a method for manufacturing a multilayer wiring board that is suitable for mass production and enables high-density circuit formation.

Hereinafter, a method for manufacturing a multilayer wiring board according to the present invention will be explained using FIGS. 4A to 4E.

In the present invention, first, as shown in FIG. 4A, a so-called copper-clad laminate 33 is prepared by laminating a copper foil 32 on a rigid insulating substrate 31 made of, for example, paper phenol, paper epoxy, or glass epoxy. This copper foil 32 is selectively etched to form a first layer wiring pattern 34, and a mechanical part is formed between a first part 35 having this wiring pattern 34 and a second part 36 which is later separated from the first part 35. Separation means 37 are provided which can be separated by force. In the illustrated example, this separation means 37 is constructed with so-called perforations 38, which are holes made at regular intervals, but it is also possible to provide V-shaped grooves along the separation line on the back surface. It is.

Next, as shown in FIG. 4B, a release layer 39 is formed on the second portion 36 of the substrate 31 by release printing or taping. For release printing, for example, epoxy resin containing 10% or more silicone resin liquid, silicone ink using phenol resin paint, epoxy containing Teflon powder (particle size 5 to 50μ), ink using phenol resin, etc. can be used. .
Further, as the taping, a silicone film (silicon tape) or a Teflon film (Teflon tape) coated with an acrylic emulsion adhesive may be used.

Next, as shown in FIG. 4C, almost the entire surface of the substrate 31, that is, the connection portion 40 with the second layer wiring pattern to be formed after the first layer wiring pattern 34, and the electrical component connection portion (not shown) are formed. Further, a flexible insulating resin layer 42 is formed by printing on the entire surface except for a portion 41 corresponding to a connection portion with another wiring board. As this insulating resin layer 42, for example, epoxy polyamide, epoxy acrylate, urethane acrylate, blend resin, or the like can be used.

Next, after pasting a conductive foil layer, for example, copper foil, on the entire surface of the insulating resin layer 42, the copper foil is selectively etched as shown in FIG. 4D to form the second layer wiring pattern 4.
3 and an opening 44 reaching the connection portion 40 of the first layer wiring pattern 34 is formed. Note that in the opening 44 of the second layer wiring pattern 43, the adhesive 50 from when the copper foil was pasted remains, so the adhesive in that area is further removed with an organic solvent and the first layer wiring pattern 43 is removed. 34 connection parts 40 are exposed. At the same time when this second layer wiring pattern 43 is formed, an opening 5 is formed at a position corresponding to the connection part with another wiring board.
It is possible to form 1.

Next, as shown in FIG. 4E, the opening 44 of the second layer wiring pattern 43 is filled with a conductive material 45 to connect the upper and lower wiring patterns 43 and 34.
Thereafter, the second portion 36 is separated from the perforation 38 of the substrate 31 by mechanical means and removed.
This second portion 36 is also released from the insulating resin layer 42 by the release layer 39 .

As the conductive material 45, a conductive material such as a gallium alloy, a solder dip, a silver paste, a metal spraying of a low melting point metal such as CU, Zn, or Sn can be used.
In particular, in the case of gallium alloys, gallium Ga, which is liquid at room temperature below 30°C, a metal that is eutectic with this gallium, and a metal powder (single metal powder or alloy powder) that can be alloyed with gallium and raise its melting point. ). This gallium alloy conductive substance has the property of initially forming a paste-like form at the working temperature, and then becoming alloyed and solidifying over time. When this gallium alloy is used, the problem of silver migration that occurs with silver paint is avoided, and the conductivity is equivalent to that of Cu plating, making it possible to form high-quality circuits.

As a method for separating the second portion 36 of the substrate 31, for example, as shown in FIGS.
3 and 54, and push up the second portion 36 from below with the presser 55, it can be easily separated from the perforation 38.

By doing so, as shown in FIG. 4E, a first layer is formed on the rigid circuit portion 56 having the first layer wiring pattern 34 so that the connection end 57 to another wiring board protrudes from the edge thereof. 2 layer wiring pattern 4
A target multilayer wiring board 59 is obtained in which flexible circuit portions 58 having a thickness of 3 are laminated. When connecting this multilayer wiring board 59 to another wiring board,
The flexible circuit portion 5 is similar to that shown in FIG. 1 above.
8 over the connection end 57 of another wiring board 4 (see FIG. 1) so that the opening 51 of the second layer wiring pattern 43 is aligned with the required circuit pattern of the other wiring board 4. Then, the opening 51 is filled with the conductive material 45.

According to the manufacturing method of the present invention described above, a first layer wiring pattern 34 is formed on a rigid insulating substrate 31, and a second layer wiring pattern 43 is further formed thereon via a flexible insulating resin layer 42. By separating and removing the second portion 36 corresponding to the connecting portion of the insulating substrate 31 with other wiring boards, this type of multilayer wiring board can be manufactured with high productivity while simultaneously forming high-density circuits. Can be manufactured. In particular, the opening 44 used for connection between both wiring patterns 34 and 43
Since the holes are formed by chemical etching without using the conventional drilling process, the hole diameter is fine, and therefore the area occupied by the wiring patterns 34 and 43 including the connection parts is small, making it possible to increase the density. Become. Moreover, since the opening 44 can be formed in the rigid substrate state, handling during the manufacturing process is facilitated.

In addition, both wiring patterns 34 are connected by the insulating resin layer 42.
and 43 because the distance between them is small, the conductive material 45
For example, when filling with gallium alloy, it can be easily filled by printing means, which enables continuous production and is suitable for mass production.

Furthermore, since an opening 51 can be provided in advance at the connection end for connection to another wiring board, the connection can be easily made using this opening 51.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the wire connection state of different wiring boards for explaining the present invention, and FIGS. 2A and B and 3 A and B are steps showing an example of a conventional method for manufacturing a multilayer wiring board, respectively. 4A to 4E are process diagrams showing the manufacturing method of the present invention, and FIGS. 5A and 5B are sectional views showing an example of the separation process of the present invention. 31 is a rigid insulating substrate, 34 is a first layer wiring pattern, 35 is a first part, 36 is a second part,
38 is a perforation, 39 is a release layer, 43 is a second layer wiring pattern, and 44 is an opening.

Claims (1)

[Claims] 1. A first part with a required wiring pattern,
forming a release layer on the second part of the substrate, the second part being connected to the first part but separated by mechanical force; a step of printing an insulating resin layer except for at least the upper and lower connecting portions of the part and the second portion and the electrical component connecting portion; a step of depositing a conductive foil layer on the insulating resin layer; and a step of depositing a conductive foil layer on the insulating resin layer. A multilayer wiring comprising the steps of forming and connecting an opening in a layer to a wiring pattern formed on at least the first portion, and mechanically separating the second portion from the first portion. Substrate manufacturing method.