JP2782576B2 - Method of forming conductive circuit - Google Patents

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 suitable for a circuit requiring a current capacity, such as a power circuit, in which a circuit pattern is formed on an insulating substrate.

[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 components are mounted or as a device for interconnecting electronic components. Such a circuit board generally has a copper circuit pattern formed on an insulating substrate, and in particular, a circuit 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 has a higher degree of freedom in mounting.

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

[0004]

When a circuit pattern is formed by the above-mentioned method, a copper foil of about 25 μm is generally used, and a thickness of 75 μm at most is used in view of a balance between the etching rate of copper foil and productivity. 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.

[0005] Therefore, it is possible to obtain a thick film circuit by further electrolytic plating the copper foil circuit and laminating an electrolytic plating layer, but when such a thick film circuit is formed, it is shown in FIG. As described above, in the thick-film circuit 20, a bulge called a dock bone is formed at the end 23a of the electrolytic plating layer 23 on the copper foil 22, and it is difficult to form a circuit body by making it difficult to form a coverlay as a post-process. Becomes Reference numeral 21 in the drawing indicates an insulating substrate.

An object of the present invention is to form a good conductive circuit by forming a circuit body pattern at a low cost and using a uniform thick conductive layer.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to provide a method and a method for arranging a plurality of layers as bases for electroplating on an insulating substrate at predetermined intervals, and then immersing the layers in an electroplating bath to form the base layers. Apply current to build up the electrolytic plating layer at the edge of the underlayer.
Adjacent to each other by depositing on a thick film so that it rises
This is achieved by a method of forming a conductive circuit, wherein a circuit pattern having a predetermined width is formed by connecting the underlayer with the electrolytic plating layer .

[0008]

When a thick layer of electrolytic plating is formed on a plurality of underlying layers of electrolytic plating at predetermined intervals, the plating layer is concentrated on the edges of the underlying layer by the dogbone effect. . Therefore, the underlying layers adjacent to each other pull flatten the concentration of the deposited plating layer to obtain a uniform circuit body. Therefore, a dog bone generated at the time of forming a thick film by electrolytic plating as in the related art is suppressed, the unevenness of the circuit body is eliminated, and the post-processing insulation can be easily performed. 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 serving as bases for the above-described electrolytic plating at predetermined intervals, the amount of the base layers used can be reduced by half, and the manufacturing cost can be reduced.

[0009]

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

As shown in FIG. 1, a plurality of printed layers 2 are formed in a narrow width, and a plurality of printed layers 2 are juxtaposed at a predetermined interval 2d, and the juxtaposed overall width e is a circuit pattern width a of a desired conductive circuit. The width is set to be narrower (see FIG. 3). Then, in the electroplating, when a current is applied to the printed layer 2 of the conductive paste, the electroplated layer 3 is deposited so that the edge of the conductive paste is raised by the dog bone 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 anticipation of the dogbone effect, and is formed so as to communicate the printed layers 2 of the respective conductive pastes. And
The conductive paste is applied on the printed layer 2 so as to have a predetermined circuit width a.

Incidentally, when the present inventors conducted experiments,
The thickness of the conductive paste is 30 μm, and the narrow width c is 500 μm.
When the electrolytic plating layer 3 of copper was provided so that the thick film b was 200 μm, it was confirmed that the copper plating layer 3 was deposited to be wider than the printed layer 2 of the conductive paste by about 210 μm. In addition, the circuit body width a and the conductive paste printed layer 2
It has been found that the relationship with the narrow width c can generally be obtained as shown in the following formula.

[0012]

A = n (c + 2d) d = (1.0-1.2) b Note that n ≧ 2, c ≧ the limit of printing accuracy of the printing layer (depending on the paint, usually more than tens of μm)

However, the establishment of the above equation varies depending on the type of the electrolytic plating solution. The circuit width a and the thick film b are different from the required electric capacity. General screen printing can be applied to the formation of the print layer using the conductive paste. The insulating layer 4 covers the circuit pattern and protects the circuit, and is provided by bonding an insulating film or uniformly applying an insulating paste.

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

The form of the circuit pattern described above is shown corresponding to FIG. And finally, the conductive circuit 1
No. 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 serving as the base of the electrolytic plating is described as being provided by printing of a conductive paste. However, instead of this, the present invention employs, for example, a method of vapor deposition or the like on the entire surface of the insulating substrate. The present invention is also applicable to a case where the copper foil provided in the above 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 a copper foil, a paste to which a catalyst for electroless plating is added is used as a base layer for electrolytic plating. That is, the conductive circuit 1
0A is a method in which a printed layer 2A of a paste to which an electroless plating catalyst is added is formed on the insulating substrate 1 by screen printing, and this is immersed in a copper electroless plating bath to deposit the electroless plated layer 5. Is done. At this time, the electroless plating layer 5
May have a small thickness, for example, a uniform 2 μm on the printed layer 2A.
It is sufficient if about m is deposited. Next, the electroless plating layer 3 is applied to the electroless plating layer 5 by the same processing as in the previous embodiment.
Is deposited by immersion current in an electrolytic plating bath, and then an insulating layer 4 is provided to form a conductive circuit 10A.

FIG. 7 shows still another embodiment of the present invention. In this embodiment, the underlayer for electrolytic plating is provided by developing a toner to which a catalyst for electroless plating is added by photographic technology. That is, a toner 6 to which an electroless plating catalyst has been added is developed along the positive charge pattern on the insulating substrate 1 and then immersed in a copper electroless plating bath to form the electroless plating layer 5. It is uniformly deposited on the toner 6 to which the catalyst for electrolytic plating is added. Next, as in the embodiment shown in FIG. 6, the conductive circuit 10 </ b> B immerses the electroless plating layer 5 in the electrolytic plating bath and applies a current to the electroless plating layer 5 to thereby form a thick film of the electrolytic plating layer 3 on the electroless plating layer 5. After precipitation
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 is formed by arranging a plurality of layers which are the bases for electrolytic plating at predetermined intervals, thereby increasing the cost of the bases. In the electroplating applied to a thick film, the dog bone seen in the prior art is a flattened electroplating layer that is pulled from each other between a plurality of adjacent underlayers. And a conductive circuit can be formed by facilitating the insulating process without obstructing the insulating process by the post-processing.

[Brief description of the drawings]

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

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

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

FIG. 4 is a cross-sectional view illustrating a method of forming a conductive circuit according to an embodiment of the present invention, which is a final process diagram.

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

FIG. 6 is a circuit 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 illustrating a method of forming a conductive circuit according to still another embodiment of the present invention.

FIG. 8 is a circuit 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 electrolytic plating layer 4 insulating layer 5 electroless plating layer 6 toner

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-179593 (JP, A) JP-A-59-153891 (JP, A) JP-A-54-126959 (JP, A) 4873 (JP, B1) (58) Field surveyed (Int. Cl. ⁶ , DB name) H05K 3/10-3/24, 3/38

Claims (5)

(57) [Claims] [Claim 1] After several juxtaposed serving as a base layer of electrolytic plating on the substrate a predetermined distance, the electrolytic plating layer of underlayer by energizing the layer serving as the underlayer was immersed in the electrolytic plating bath edge
Next to each other by depositing on a thick film so that it rises in the area
The method for forming a conductive circuit, characterized in that the base layer to form a circuit element pattern of Tokoro <br/> constant width communicated by the electrolytic plating layer in contact. 2. A method according to claim 1, wherein a plurality of said base layers are arranged at predetermined intervals by printing a conductive paste.
A method for forming the conductive circuit according to the above. 3. A method for forming a conductive layer by electroless plating after arranging a plurality of pastes containing a catalyst for electroless plating at predetermined intervals by printing and then immersing the paste in an electroless plating bath. The method for forming a conductive circuit according to claim 1, wherein 4. The method according to claim 1, wherein a plurality of layers as the base are arranged at predetermined intervals by developing an electrostatic charge pattern obtained by electrophotographic recording with a toner containing a catalyst of electroless plating.
2. The method for 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 provided with an insulating layer covering the circuit pattern.