JPH07115257A - Formation of conductive circuit - Google Patents

Abstract

PURPOSE:To halve the amount of consumption of a base layer by providing a plurality of electrolytic plating base layers at specified intervals on an insulated substrate, dipping them in an electrolytic plating bath to charge the base layer with electricity and forming a thick film of the electrolytic plated layer by precipitation. CONSTITUTION:A plurality of printed layers 2 are arranged at specified intervals and the entire width e is set at a narrower width than the circuit pattern width a of a conductive circuit. Electrolytic plating, by charging printed layer 1 of a conductive paste with electricity, precipitates an electrolytic plating layer 3 due to the dog bone effect in a way that an edge part of the conductive paste builds up. Further, the electrolytic plating layer 3 is mutually pulled by the printed layers of the conductive paste to become a thick film b in anticipation of the dog bone effect and formed so as to send a current through the printed layers 2 of each conductive paste, on which it is deposited with a specified circuit width.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a conductive circuit having a circuit pattern formed on an insulating substrate and suitable for a circuit requiring a current capacity such as a power circuit.

[0002]

2. Description of the Related Art Conventionally, a circuit board has been used for various electronic devices as a replaceable element on which electronic parts are mounted or for connecting electronic parts to each other. Such a circuit board generally has a copper circuit body pattern formed on an insulating substrate, and in particular, a circuit board pattern formed on a flexible substrate,
It has been widely used in recent years because it can be arranged in, for example, a narrow space corresponding to miniaturization of devices and the like, and thus the degree of freedom in mounting is improved.

By the way, in order to form a circuit body pattern, for example, a copper foil is adhered on the entire surface of the substrate, and a resist agent is printed on a screen of an image corresponding to a desired circuit body pattern. There is a method in which copper in a region not covered with a film is removed by etching, and finally a resist agent is removed to form.

[0004]

When forming a circuit body pattern by the above method, a copper foil of about 25 μm is generally used in consideration of the etching rate of copper foil and productivity, and a thickness of at least 75 μm is used. It is the limit. Therefore, the conventional circuit body is used for a signal circuit, a minute current circuit, or the like, and cannot be used for a power circuit or the like that requires a current capacity.

Therefore, it is possible to further electrolytically plate a copper foil circuit and laminate an electrolytic plating layer to obtain a thick film circuit. However, when such a thick film circuit is formed, it is shown in FIG. As described above, in the thick film circuit 20, a ridge called a dock bone is formed on the end portion 23a of the electrolytic plating layer 23 on the copper foil 22, and it becomes difficult to make a coverlay as a post-process, and it is difficult to create a circuit body. Becomes Reference numeral 21 in the figure indicates an insulating substrate.

An object of the present invention is to form a circuit pattern at a low cost with a uniform thick conductive layer to form a good conductive circuit.

[0007]

The above object of the present invention is to provide a plurality of layers serving as a base for electrolytic plating on an insulating substrate in parallel at a predetermined interval, and then to dip in an electrolytic plating bath to form the base layer. This is achieved by a method for forming a conductive circuit, which is characterized by forming a predetermined circuit body pattern by applying a current to deposit a thick film of an electrolytic plating layer.

[0008]

[Function] When the electrolytic plating is formed as a thick film on the underlying layer for electrolytic plating which is arranged in parallel at a predetermined interval, the plating layer is concentrated on the edge portion of the underlying layer due to the dogbone effect. . Therefore, adjacent base layers mutually pull out the concentration of the deposited plating layers to flatten them to obtain a uniform circuit body. Therefore, the dogbone generated when a thick film is formed by electrolytic plating as in the conventional art is suppressed, the unevenness of the circuit body is eliminated, and the post-process insulation process can be easily performed. Further, the base layer for electrolytic plating is a paste or toner containing a conductive paste or a catalyst for electroless plating and is expensive. Therefore, by arranging a plurality of layers as the base of the above-mentioned electrolytic plating side by side at predetermined intervals, the amount of use of the base layer is halved and the manufacturing cost can be reduced.

[0009]

EXAMPLE An example of the method for forming a conductive circuit of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to this. 1 to 4 are circuit cross-sectional views showing an embodiment of a method of forming a conductive circuit of the present invention in the order of circuit manufacturing steps. In FIG. 4, a conductive circuit 10 according to the present invention has a circuit body pattern in which a printed layer 2 of a conductive paste, which is a base of electrolytic plating, an electrolytic plated layer 3, and an insulating layer 4 are sequentially laminated on an insulating substrate 1. Form.

As shown in FIG. 1, the printed layer 2 is formed in a narrow width, and a plurality of the printed layers 2 are arranged in parallel at a predetermined interval 2d, and the overall width e arranged in parallel is a circuit body pattern width a of a desired conductive circuit. It is set to a narrower width (see FIG. 3). In the electroplating, the printed layer 2 of the conductive paste is energized to deposit the electroplated layer 3 so that the edge portion of the conductive paste rises due to the dogbone effect as shown in FIG. Further, as shown in FIG. 3, the electroplating layer 3 is pulled between the printed layers of the conductive paste to form a thick film b in consideration of the dogbone effect, and is formed so as to connect the printed layers 2 of the conductive pastes. Is
The conductive paste is applied onto the printed layer 2 so as to have a predetermined circuit body width a.

Incidentally, when the present inventors conducted an experiment,
Thickness of conductive paste is 30μm, narrow width c is 500μm
It was confirmed that when the copper electroplating layer 3 was provided so that the thick film b had a thickness of 200 μm, the copper plating layer 3 was broadly deposited by about 210 μm from the printed layer 2 of the conductive paste. In addition, the width a of the circuit body and the printed layer 2 of the conductive paste
It has been found that the relationship with the narrow width c of is generally obtained as shown in the following mathematical formula.

[0012]

## EQU1 ## a = n (c + 2d) d = (1.0 to 1.2) b Note that n.gtoreq.2, c.gtoreq.printing accuracy limit of the printing layer (varies depending on the paint, usually ten or more .mu.m or more)

However, the establishment of the above-mentioned mathematical expression changes depending on the type of electrolytic plating solution. The circuit body width a and the thick film b are different with respect to the required electric capacity. General screen printing can be applied to the formation of the printed layer with the conductive paste. The insulating layer 4 covers the circuit pattern and protects the circuit, and is provided by adhering an insulating film or by uniformly applying an insulating paste.

FIG. 5 is a process diagram more specifically showing the method for forming a conductive circuit according to the present invention. Conductive circuit 10
First, a circuit is designed by CAD, a predetermined circuit body pattern is formed, and then a screen corresponding to this circuit body pattern is formed to be formed. Using this screen, the printed layer 2 of the circuit body pattern is screen-printed on the film to be the insulating substrate. The form of the printing layer 2 formed by screen printing is shown corresponding to FIG. Then, after the printed layer 2 is dried and cured, it is immersed in an electrolytic plating bath to deposit the electrolytic plated layer 3 in a thick film.

The form of the circuit body pattern described above is shown in correspondence with FIG. And finally, the conductive circuit 1
0 is formed by punching the insulating substrate 1 into a predetermined shape after the insulating layer 4 is formed. In the above embodiment, the circuit of the copper foil which is the base of the electrolytic plating is described as being provided by printing the conductive paste, but instead of this, the present invention is the whole surface on the insulating substrate by a method such as vapor deposition. It is naturally applicable to the case where the copper foil provided on the substrate is formed by etching and electrolytic plating is performed on the copper foil.

Next, another embodiment of the present invention will be described with reference to FIG. In this embodiment, instead of the copper foil as the underlayer for electrolytic plating, a paste containing a catalyst for electroless plating is used as the underlayer. That is, the conductive circuit 1
0A is a method in which a printed layer 2A of a paste containing a catalyst for electroless plating is formed on the insulating substrate 1 by screen printing, and the electroless plated layer 5 is deposited by immersing the printed layer 2A in a copper electroless plating bath. To be done. At this time, the electroless plating layer 5
May have a small thickness, for example, 2 μm evenly on the printed layer 2A.
It suffices to deposit about m. Then, the electroless plating layer 5 is formed on the electroless plating layer 5 by the same processing as in the previous embodiment.
After the thick film is immersed in the electrolytic plating bath to be energized and deposited, the insulating layer 4 is provided to form the conductive circuit 10A.

FIG. 7 shows still another embodiment of the present invention. In this embodiment, a base layer for electrolytic plating is provided by developing a toner added with a catalyst for electroless plating by photographic technology. That is, after the toner 6 to which the electroless plating catalyst has been added is developed along the positive charge pattern on the insulating substrate 1, the electroless plating layer 5 is removed by immersing it in a copper electroless plating bath. It is uniformly deposited on the toner 6 to which a catalyst for electrolytic plating is added. Next, in the conductive circuit 10B, the electroless plating layer 5 is immersed in an electrolytic plating bath to conduct electricity, so that the electroless plating layer 5 is coated with a thick film of the electrolytic plating layer 3 as in the embodiment shown in FIG. After depositing
The insulating layer 4 is formed and provided.

[0018]

As described above, according to the method for forming a conductive circuit according to the present invention, the conductive circuit has a plurality of layers serving as a base of electrolytic plating arranged at a predetermined interval side by side, thereby making the base expensive. It is possible to reduce the amount of various materials used, and in electrolytic plating applied to thick films, the dogbone seen in the prior art is an electrolytic plating layer in which a plurality of adjacent base layers are pulled together and flattened. The conductive circuit can be formed by facilitating the insulation process without disturbing the insulation process due to the post-processing.

[Brief description of drawings]

FIG. 1 is a circuit cross-sectional view in a first process chart showing a method of forming a conductive circuit according to an embodiment of the present invention.

FIG. 2 is a circuit cross-sectional view in the second process chart showing the method for forming the conductive circuit according to the embodiment of the present invention.

FIG. 3 is a circuit cross-sectional view in a third process diagram showing a method for forming a conductive circuit according to an embodiment of the present invention.

FIG. 4 is a circuit cross-sectional view in a final process drawing showing a method for forming a conductive circuit according to an embodiment of the present invention.

FIG. 5 is a process chart specifically showing one embodiment of the present invention.

FIG. 6 is a circuit cross-sectional view showing a method of forming a conductive circuit according to another embodiment of the present invention.

FIG. 7 is a circuit cross-sectional view showing a method of forming a conductive circuit according to still another embodiment of the present invention.

FIG. 8 is a circuit cross-sectional view of a conductive circuit showing a conventional example.

[Explanation of symbols]

 10, 10A, 10B Conductive circuit 1 Insulating substrate 2 Printing layer 3 Electroplating layer 4 Insulating layer 5 Electroless plating layer 6 Toner

Claims (5)

[Claims] 1. A plurality of base layers for electroplating are juxtaposed on a substrate at predetermined intervals, and then immersed in an electroplating bath to energize the base layers to deposit a thick film of the electroplating layer,
A method for forming a conductive circuit, which comprises forming a predetermined circuit body pattern. 2. The layer as the base is a plurality of conductive pastes arranged in parallel at predetermined intervals by printing.
A method of forming a conductive circuit according to claim 1. 3. The base layer is formed by arranging a plurality of pastes to which a catalyst for electroless plating is added at predetermined intervals by printing and then immersing the paste in an electroless plating bath to deposit a conductive layer by electroless plating. The method for forming a conductive circuit according to claim 1, wherein 4. A plurality of the underlying layers are arranged in parallel at predetermined intervals by developing an electrostatic charge pattern obtained by electrophotographic recording with a toner containing a catalyst of electroless plating,
The method of forming a conductive circuit according to claim 1, wherein the conductive layer is immersed in an electroless plating bath to deposit a conductive layer by electroless plating. 5. The method for forming a conductive circuit according to claim 1, wherein the conductive circuit is a conductive circuit body that covers the circuit pattern and is provided with an insulating layer.