JPS6312192A - Method of forming electric circuit - 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 OBJECTS OF THE INVENTION (Industrial Field of Application) The present invention relates to a method of forming electrical circuits as an alternative to conventional printing or photography methods.

(Prior Art) Conventionally, methods for forming circuits such as printed circuit boards, flexible printed circuit boards, and circuit boards in which metal is covered with an insulating layer on a metal plate are as shown in the case of the printed circuit board shown in FIG. 4, for example. Insulating material (e.g. glass epoxy resin) 11
A resist 14 is formed on the portion of the conductive metal foil (for example, copper foil) 12 pasted thereon, which will become the circuit section 13, by a method such as a printing method or a photographic method (FIGS. 4a and 4b), and etching is performed to form a resist 14 on the portion that will become the circuit portion 13. Generally, the melted portion 15 not covered by the resist 14 is dissolved and removed (FIG. 4C), and finally the resist 14 is peeled off to form the circuit portion 13 on the insulating material 11 (FIG. 4D). Met.

(Problems to be Solved by the Invention) This conventional printing method or photographic method requires a complicated process for forming a resist film, requires a large amount of cost for treating waste etching solution, and furthermore, However, since an undercut 16 occurs during the etching process, a highly accurate circuit section cannot be obtained. Recently, there has been a demand for a high-precision circuit forming method to obtain fine circuit parts that can cope with the rapid development of integrated circuits.

The present invention has been made in view of these points, and it is an object of the present invention to provide a circuit forming method that can form a highly accurate circuit section.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a method for forming a circuit on a substrate by pasting a conductive metal foil 22 on an insulating material 21 shown in FIG. By providing a notch 23 in accordance with the circuit pattern only in the foil 22, the metal foil 22 is separated into a circuit portion 24 and a melting portion 25 and electrically insulated, and then DC voltage is applied using the circuit portion 24 as a cathode. This is an electric circuit formation method in which etching is performed on the melted part while applying

(Function) The present invention electrically insulates the circuit portion 24 from the melting portion 25 by the notch 23 formed in the metal foil 22, and applies a cathode potential only to the circuit portion 24. 24 remains on the insulating material 21 without being etched even if it is in the etching solution, and only the dissolved portion 25 is eluted into the etching solution.

(Example) Hereinafter, the present invention will be explained in detail with reference to the example shown in FIGS. 1 to 3.

As shown in FIG. 1A, conductive metal foil (for example, copper foil) is applied to the entire surface of the insulating material (for example, glass epoxy resin) 21.
22, cutouts 23 shown in FIG. 1B are formed only in the metal foil 22 using a cutter, laser, high-pressure water, press, etc. according to the circuit pattern. As a result, the metal foil 22 is separated into the circuit portion 24 and the melting portion 25, and the circuit portion 24 and the melting portion 25 are electrically insulated.

Next, as shown in FIG. 2, the substrate and an insoluble conductor 33 such as titanium or carbon are immersed in an etching solution 32 such as an ammonium persulfate solution in an etching tank 31, and then the substrate is etched. By connecting the circuit portion 24 as a cathode and the insoluble conductor 33 as an anode to a DC power source 34, and performing etching while applying a DC voltage, only the dissolving portion 25 can be etched without forming a resist. is eluted into the etching solution 32, and since the cathode potential is applied to the circuit portion 24 even though it is in the etching solution, it remains without being etched, and as a result, as shown in FIG. A circuit section 24 is obtained.

The above is just one embodiment of the present invention; for example, by increasing the DC voltage, even if the initial metal foil (copper foil) 22 is thin, the circuit section 24 can be etched into the etching solution from the dissolving section 25. It is also possible to obtain the circuit portion 24 of thick metal foil (copper foil) by plating with the eluted metal (copper). Since metal plating is performed in the etching solution in this way, etching and plating can be performed simultaneously in one step, and furthermore, the metal (copper) ions eluted from the melting section 25 can be deposited on the circuit section 24 again as a plating material. This is extremely advantageous in terms of resource saving and pollution prevention, and provides a high-precision circuit section 2 with no undercuts.
4 can be obtained efficiently.

Further, by controlling the DC voltage, the cathode circuit portion 24 can be easily controlled in any manner such as etching, no change, plating, or an intermediate stage thereof.

Further, although the above embodiment was carried out in the etching solution 32,
As shown in the figure, etching may be carried out in a dew atmosphere sprayed into the etching bath 31. In this case, a spray nozzle (for example, made of titanium) 41 may be used as an anode, and a pump 42 is attached to this nozzle 41. The etching liquid 32 in the tank is supplied under pressure.

As described above, the present invention includes all methods that perform etching while applying a voltage, regardless of the embodiment.

Furthermore, although a single cathode circuit section 24 is shown in FIG. Different voltages may be applied to the portions 24.

Further, in the above embodiments, an ammonium persulfate solution was used as an etching solution, but it goes without saying that any etching solution other than this can be used depending on the target metal.

〔Effect of the invention〕

According to the present invention, by providing cuts corresponding to the circuit pattern only in the metal foil on the insulating material, the metal foil is separated into the circuit part and the melting part and electrically insulated, and then the circuit part This is a circuit formation method in which the molten part is etched while a DC voltage is applied to the molten metal as a cathode. Unlike conventional methods, no resist is used at all, and the circuit part is separated from the molten part. No undercuts occur during the etching stage. Therefore, a highly accurate circuit section can be formed. In addition, complicated resist film formation processes such as conventional printing methods or photographic methods (e.g. resist coating,
(exposure processing, etc.) is not required. Furthermore, since DC voltage is applied using the circuit section as a cathode, etching and plating can be performed simultaneously in one step, and metal ions eluted from the dissolving section into the etching solution can be deposited on the circuit section as plating again. It has excellent effects in terms of resource saving and pollution prevention.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a substrate showing the steps of the electric circuit forming method of the present invention, FIG. 2 is a cross-sectional view showing an example of etching in the method, and FIG. 3 is a cross-sectional view showing another example of etching. 4 are cross-sectional views of a substrate showing the steps of a conventional electric circuit forming method. 21...Insulating material, 22...Metal foil, 23...Notch, 24
...Circuit part, 25...Dissolution part.

Claims (1)

[Claims] (1) In a method of forming a circuit on a board made by pasting conductive metal foil on an insulating material, this metal foil is 1. A method for forming an electric circuit, which comprises separating the circuit part and the melting part and electrically insulating them, and then etching the melting part while applying a DC voltage using the circuit part as a cathode.