JPS61254038A - Forming method for circuit pattern - Google Patents

Abstract

PURPOSE:To enable fine circuit patterns to be formed, by removing the corner sections from the patterns with electrolytic polishing, and by plating the patterns electrolytically, after the circuit patterns are formed by means of etching. CONSTITUTION:First, on the both surfaces of an insulating layer 1, flexible substrates with formed copper foil layers 2A, 2B are arranged. Second, after the layers are patterned with photoresists 3A, 3B, the layers are treated by means of etching to remove unnecessary sections and to form coil patterns 4A, 4B. Third, after the photoresists 3A, 3B are exfoliated, roundish patterns are obtained by removing the corner sections from the coil patterns 4A, 4B, namely, the shoulder sections of the pattern edges by means of electrolytic polishing. After that, a penetrating slot 5 for a through hole as part of the patterns is formed. Finally, the patterns are electrolytically plated, and coil patterns 6A, 6B are obtained by separating out copper on the surface of the coil patterns 4A, 4B.

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.
For example, it is suitable for manufacturing printed coils for small motors.

B0 Summary of the Invention The present invention relates to a circuit pattern forming method used when forming circuit patterns on both sides of an insulating layer. Form a through hole and electrolyze! By applying the thickness, it is possible to simultaneously perform pattern filling and electrical connection between double-sided patterns, and also to form fine patterns and increase the space factor.

C0 Prior Art Conventionally, motors have been widely used in devices that require a power source. For example, as shown in FIG. 6, the coils of this motor are made by winding a so-called enamelled wire having a enamel layer 12 around a copper wire 11 into a core (not shown).
It is manufactured by wrapping the

On the other hand, in recent years, with the spread of portable cassette tape players and cassette tape recorders (so-called headphone stereos), there has been a demand for the development of motors that are smaller in size and have better performance. However, it is difficult to manufacture the coil for such a Koniwa motor due to the above-mentioned winding method. This is because it is difficult to thin the wire (because the diameter of the copper wire 11 must be 100 μm or more), and it is difficult to perform soldering work for interconnecting each winding.

In contrast, a method has been proposed in which coils (so-called printed coils) are formed on both sides of an insulating substrate by etching or plating. As shown in FIG. 7, the etching method is a method in which, for example, both sides of an insulating substrate 13 made of polyimide or the like on which a copper foil layer is formed are etched to form coil patterns 14A and 14B. As shown in FIG. 8, for example, after patterning photoresists 17A and 17B on both sides of an insulating substrate 16 having electrode metal foil layers 15A and 15B, copper is deposited by electrolytic plating to form coil patterns 18A and 18B.
This is a method of forming.

D1 Problems to be Solved by the Invention According to such an etching method or a plating method, a single winding machine is not required, and a plurality of coils can be manufactured simultaneously. However, each method has the following drawbacks.

(a) In the case of the etching method, in order to obtain the thickness Tg of the patterns 14A and 14B, the original copper foil layer needs to be thick, so it is difficult to obtain the desired shape, and as shown in the figure, the pattern becomes thin due to the side etching phenomenon. I end up. Also, the gap Gg between patterns is 1
The limit is approximately 00μ wind, and it cannot be made smaller than this, making it impossible to form fine patterns. Furthermore, due to these factors, the space factor (conductor occupancy factor), which greatly affects the performance of the motor, becomes low. Furthermore, electrical connections must be made between the patterns (conductors) on both sides via the insulating substrate 13.

(b) In the case of the plating method, electrode metal foil layers 15A and 15B are required for plating, and must be removed after plating.

Also, at this time, it is necessary to peel off the photoresists 17A, 17B, but this is difficult due to the structure. Furthermore, in order to increase the thickness TM of the patterns 18A and 18B, it is sufficient to increase the thickness TMP of the photoresists 17A and 17B.
The resolution of photoresists 17A and 17B may decrease,
There is a risk of contact (short circuit) with adjacent patterns, so the thickness TM cannot be made too thick, resulting in a decrease in space factor. Furthermore, the width WM of the pattern is limited to about 100 μm due to the required thickness TM, making it impossible to form a fine pattern.

Therefore, the present invention has been proposed in view of the above-mentioned conventional problems, and provides a circuit pattern that can be made finer, thicker without causing any inconvenience, and that can increase the space factor. The purpose is to provide a forming method. Another object of the present invention is to provide a circuit pattern forming method that allows easy electrical connection between double-sided patterns.

Means for Solving the E0 Problem In order to achieve the above-mentioned object, the circuit pattern forming method according to the present invention provides a flexible substrate in which conductive layers are formed on both sides with an insulating layer sandwiched between them. A step of etching the layer to form a circuit pattern that is integrally conductive within six planes, a step of removing the corners of the circuit pattern by electrolytic polishing, and a step of etching a part of the circuit pattern from one side. It is characterized by comprising a step of forming a through hole penetrating the other surface, and a step of applying electrolytic plating to the circuit pattern.

F0 Effect According to the present invention, the corners of the circuit pattern formed by etching are removed by electrolytic polishing, and after the through holes are formed, a metal such as copper is deposited on the surface of the pattern by electrolytic plating.

G9 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. In this embodiment, the present invention is applied to a method of forming a coil (printed coil) pattern for a small motor.

First, as shown in FIG.
A flexible substrate on which A and 2B are formed is prepared. The insulating layer 1 may be made of, for example, polyimide, polyamide,
polyester, diallyl phthalate, polybutadiene,
Materials such as epoxy urethane can be used, and the thickness T
OI is about 5 to 25 μm. In addition, the copper foil layer 2A
, 2B is due to electrolytic plating, rolling, etc., and the thickness T
The oc is about 5 to 40μ doors.

Next, as shown in FIG. 2, photoresists 3A and 3B are
After patterning, an etching process is performed to remove unnecessary parts to create coil pattern 4A.

Form 4B. The above photoresists 3A and 3B include
Although it is preferred to use a liquid resist, a dry film resist can also be used. Note that a thickness TOP of the photoresists 1-3A and 3B of about 1 to 10 μm is sufficient. In addition, the above-mentioned etching treatment may be performed using, for example, an etching solution such as ferric chloride or cupric chloride.
The spray method may be used under the condition of S kg/cm' once.

Next, after peeling off the photoresists 3A and 3B, the corners of the coil patterns 4A and 4B, that is, the shoulder portions of the pattern edges, are removed by electropolishing to obtain a rounded pattern as shown in FIG. As a result, during the electrolytic plating process described later, copper grows abnormally in the horizontal direction and comes into contact with adjacent patterns (
Short circuits) can be prevented, and extremely uniform patterns can be obtained. Note that as the electrolytic polishing, for example, electrolytic etching may be used, and an example of the conditions in this case is shown below.

Current density: 80~50A/di'' Temperature: 20~40'C Time: 1~3 minutes Next, as shown in Figure 4, through holes 5 are formed in part of the pattern. This through hole 5 may be formed to have a diameter of approximately 0.5 to 1.5 mm using a drill, for example.

Finally, electrolytic plating is performed using a plating bath such as copper sulfate or copper pyrophosphate to deposit copper on the surfaces of the coil patterns 4A and 4B, resulting in the final coil as shown in FIG. Patterns 5A and 5B are obtained. Further, at this time, through holes 7 are formed, and electrical connections between the coil patterns on both sides can be made at the same time. An example of conditions for performing copper sulfate plating is shown below.

N current density: 2~5A/dm Temperature: 20~40°
A plating thickness of about 70 μm can be obtained. Also,
In this plating process, the gap GO between the coil patterns 5A and 5A and between the coil patterns 6B and 5B is
It can be set to a minimum of about 30 μm.

As described above, the method for forming the coil pattern of this embodiment uses etching and electrolytic plating in combination, and a good coil pattern can be obtained through a simple manufacturing process. That is, even if the thickness Toe of the original copper foil layers 2A, 2B and the thickness TOP of the photoresists 3A, 3B are thin, thick coil patterns 5A, 5B with a thickness TO can be obtained, the pattern can be reinforced, and the pattern can be reinforced. A pattern with a shape can be easily formed. In addition, by removing the corners of the original coil patterns 4A and 4B by electrolytic polishing to give the patterns a rounded shape, it is possible to prevent copper deposited in the electrolytic plating process from coming into contact with adjacent patterns. The gap Go between patterns can be set to a minimum.

Furthermore, because of these factors, it is possible to make the pattern finer and to increase the space factor.

Here, the space factor of each coil formed by the above-mentioned etching method (see Figure 7), plating method (see Figure 8), and this example (see Figure 5) is expressed as the cross-sectional area ratio of the conductor. An example of comparison is shown below. The conditions are as follows. The unit is μ door.

(a) Etching method Wm = 100 0g = 100 TR = 100
Φ) Plating method WM=100 GM=80' TM=60(T
MP=25) (C) This example Wo=l? As a result of calculating each cross-sectional area 8E, SM, and So under the conditions of OGo=80 To=100 or more, the cross-sectional area ratio is 8 E: SM: So = 1: 1-15
: L65, and it can be seen that the space factor of the coil formed in this example is extremely high. Therefore, a high-performance compact motor can be obtained.

Further, in the electrolytic plating process, the coil patterns 5A and 6B of a predetermined thickness can be obtained, and electrical connection (continuity) between the patterns on both sides can be made simultaneously, which is very efficient.

Note that the present invention can be applied not only to printed coils but also to a method for forming a normal circuit pattern on a flexible substrate.

H1 Effects of the Invention As is clear from the description of the embodiments described above, according to the present invention, after forming a circuit pattern by etching, the corners of the pattern are removed by electropolishing and electrolytic plating is applied. It is possible to form a circuit pattern with a wide range of characteristics, the thickness of the pattern can be increased without causing any inconvenience, and the space factor can be increased. In addition, electrical connections between double-sided patterns and pattern filling can be performed simultaneously, reducing the number of man-hours.

[Brief explanation of drawings]

1 to 5 are cross-sectional views showing an embodiment of the present invention in the order of steps. Figures 6 to 8 are cross-sectional views showing coils formed by conventional methods, with Figure 6 showing the winding method, Figure 7 the etching method, and Figure 8 the plating method. It is. 1......Insulating layer 2A, 2B...Copper foil layer

Claims (1)

[Claims] In a flexible substrate in which conductive layers are formed on both sides with an insulating layer sandwiched between them, a step of etching the conductive layers on both sides to form a circuit pattern that is integrally conductive within each surface. , a step of removing the corners of the circuit pattern by electrolytic polishing, a step of forming a through hole penetrating from one surface to the other in a part of the circuit pattern, and electroplating the circuit pattern. A circuit pattern forming method comprising a step of applying.