JPS61253893A - Circuit pattern formation - 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 A. Field of Industrial Application The present invention relates to a circuit pattern forming method used when forming circuit patterns on both sides of an insulating layer.
This is an improved method of electrical connection between patterns on both sides, especially when the thickness of the insulating layer is thick.

B6 Summary of the Invention The present invention is a circuit pattern forming method used to form circuit patterns on both sides of an insulating layer, in which a circuit pattern is formed by etching, the insulating layer is partially thinned, and through holes are formed. By applying electrolytic plating after forming the pattern, it is possible to simultaneously thicken the pattern and make electrical connections between the patterns on both sides, and it is also possible to easily obtain a fine pattern with low conductor resistance. be.

C5 Prior Art Conventionally, so-called double-sided substrates in which circuit patterns are formed on both sides of an insulating layer are generally known. The circuit pattern on this double-sided board is usually formed by selectively etching metal foils such as copper provided on both sides of the insulating layer.

D2 Problems to be Solved by the Invention By the way, in the above-mentioned double-sided substrate, it is generally necessary to establish electrical connection (continuity) between the circuit patterns formed on both sides. This electrical connection can be made, for example, by creating a through hole in a predetermined part of the board where the circuit pattern is present, electrolessly plating the wall surface of the insulating layer with palladium colloid, etc. to metallize it, and then electrolytically plating it. This is done by However, with this method, it is difficult to deposit the electroless plating substance only inside the through-hole, and it is necessary to mask areas other than the through-hole, which makes the manufacturing process extremely complicated and increases costs. .

In addition, in order to form fine circuit patterns, the metal foil layer that serves as the base must be thin, but if it is thin, the conductor resistance is high, making it difficult to easily obtain fine patterns. There is a point.

Therefore, the present invention has been proposed in view of the above-mentioned conventional problems, and in particular, it provides a circuit pattern forming method that allows easy electrical connection between circuit patterns on both sides even when the thickness of the insulating layer is thick. The purpose is to provide Another object of the present invention is to provide a method for forming a circuit pattern by which a fine circuit pattern with low conductor resistance can be easily obtained.

Means for Solving Problem E1 In order to achieve the above-mentioned object, the circuit pattern forming method according to the present invention provides a circuit pattern forming method according to the present invention, in which a metal foil layer is formed on both sides of a substrate with an insulating layer sandwiched therebetween. a step of etching the substrate to form a circuit pattern that is integrally conductive within each surface; a step of pressurizing a predetermined portion of the substrate to thin the insulating layer; and a step of forming a through hole in a predetermined portion of the substrate. It consists of a step of forming the circuit pattern and a step of electrolytically plating the circuit pattern, and is characterized in that the circuit patterns on both sides are electrically connected through the through hole.

11.According to the present invention, after the insulating layer at a predetermined portion of a substrate on which circuit patterns are formed on both sides is thinned and through holes are formed, a metal such as copper is electrolytically plated on the surface of the circuit pattern. It is precipitated by

G. Example Hereinafter, an example of the circuit pattern forming method according to the present invention will be described in detail with reference to the drawings.

First, as shown in FIG.
A substrate on which A and 2B are formed is prepared.

The insulating layer 1 may be made of, for example, polyimide, polyamide,
Materials such as polyester and polybutadiene can be used, and the thickness TOI is about 15 to 100 μm. Further, the copper foil layers 2A and 2B are formed by electrolytic plating, rolling, etc., and have a thickness Toe of about 5 to 40 μm.

Next, as shown in FIG. 2, photoresists 3A and 3B are
pattern. Although it is preferable to use a liquid resist as the photoresists 3A and 3B, a dry film resist can also be used.

゛ Next, an etching process is performed and the photoresist 3A is
, 3B is peeled off to form a circuit pattern 4 as shown in FIG.
A, form 4B. The above etching process may be performed in, for example, 1. Using an etching solution such as ferric chloride or cupric chloride, 2kl? It may be carried out by a spray method under conditions of about /cm.

Next, after the insulating layer 1 is thinned by applying pressure to a predetermined portion of the substrate, in this embodiment, the central portion thereof, a through hole 5 serving as a through hole is formed as shown in No. 4 (2). The pressure applied to the substrate is, for example, a press pressure of 500 to 2000.
It may be carried out using a pressure press at a temperature of about 20 to 250°C at kli/cm2%.

Further, the through hole 5 is formed by using a drill, for example, with a diameter of 0.5 mm.
It may be formed to have a diameter of about 1.5 mm. Note that the through holes 5 can also be formed by punching while applying pressure.

Finally, electrolytic plating is performed using a plating bath such as copper sulfate or copper pyrophosphate to deposit copper on the surfaces of the circuit patterns 4A and 4B, resulting in the final circuit shown in FIG. Patterns 5A and 6B are obtained. Further, at this time, through holes 7 are formed as shown in the figure, and electrical connection (continuity) between the circuit patterns on both sides can be made at the same time.

An example of the conditions for performing copper sulfate plating is shown below.
A plating thickness of about 0 to 16 μm can be obtained.

As mentioned above, the circuit pattern forming method of this example is as follows:
In the substrate on which circuit patterns 4A and 4B are formed on both sides of the insulating layer 1, pressure is applied to the part where electrical connection between the patterns on both sides is to be made to thin the insulating layer 1 and through holes 5 are formed, and then electrolytic plating is performed. to create circuit patterns 4A and 4B.
Copper is deposited on the surface of the circuit patterns 4A and 4B, and the electrical connection between the patterns on both sides can be performed simultaneously. This is because the thinning of the insulating layer 1 eliminates the need for electroless plating and allows connection using only electrolytic plating.In particular, as in this embodiment, the thickness of the insulating layer 1 To! A great effect can be obtained when the thickness is thick. Furthermore, it goes without saying that if the insulating layer 1 is thin, the pressurizing step is not necessary.

Furthermore, since the circuit patterns 4A and 4B can be fleshed out by electrolytic plating, the original copper foil layers 2A and 2B can be thickened.
Even if the thickness Toc is small, the circuit patterns 5A and 6B finally obtained have low conductor resistance, and a fine pattern can be easily formed. The circuit pattern forming method of this embodiment is suitable for use in manufacturing coils (printed coils) for small motors, for example, and can also reduce costs.

Note that the process of forming the circuit patterns 4A and 4B by etching ζ, the process of thinning the insulating layer 1 by applying pressure, and the process of forming the through holes 5 can be arbitrarily set.

H0 Effects of the Invention As is clear from the description of the embodiments described above, according to the present invention, a predetermined portion of a substrate on which a circuit pattern is formed on both sides of the insulating layer is pressurized to thin the insulating layer, and a through hole is formed. By applying electrolytic plating after formation, even if the insulating layer is thick, it is possible to simultaneously thicken the circuit pattern and make electrical connections between the double-sided patterns. In addition, because electrolytic plating can thicken the circuit pattern and lower conductor resistance, the original metal foil layer may be thin (
A fine circuit pattern with low conductor resistance can be easily obtained.

[Brief explanation of drawings]

1 to 5 are cross-sectional views showing an embodiment of the present invention in the order of steps. 1......Insulating layer 2A, 2B...Copper foil layer

Claims (1)

[Scope of Claims] A step of etching the metal foil layers on both surfaces of a substrate having metal foil layers formed on both sides with an insulating layer sandwiched therebetween to form a circuit pattern that is integrally conductive within each surface; The method comprises the steps of: applying pressure to a predetermined portion of the substrate to thin the insulating layer; forming a through hole in a predetermined portion of the substrate; and electrolytically plating the circuit pattern. A method for forming a circuit pattern, the method comprising making an electrical connection between the circuit patterns on both sides through holes.