JPH0923048A - Method of manufacturing planar circuit body and planar circuit body - Google Patents

Abstract

(57) Abstract: A fuse part having an arbitrary cross-sectional area can be easily formed without using punching that requires a die or etching that restricts the conductor thickness. SOLUTION: On a base film 23 made of an insulating material,
A desired circuit pattern and a fuse portion 27 having a width narrower than the conductor width of this circuit pattern are printed using the conductive paste 25. The printed conductive paste 25 is dried.
By applying the electrolytic copper plating 26 to the conductive paste 25, the planar circuit body 21 is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a planar circuit body in which a fuse portion is integrally formed, and a planar circuit body manufactured by the method.

[0002]

2. Description of the Related Art Some planar circuit bodies such as printed wiring boards and flat harnesses are designed to be compact and lightweight by directly forming a fuse portion on a part of a conductor forming an electric circuit. For example, in the one disclosed in Japanese Utility Model Laid-Open No. 55-103979, as shown in FIG. 7, the circuit pattern width is narrowed by punching holes 5 at appropriate positions of the circuit pattern 3 provided on the printed wiring board 1. The fuse portion 7 is formed. The punched hole 5 is formed in the printed wiring board 1.
By using a mold together with the mounting hole 8 and the like, it is punched and processed at one time. In addition, JP-A-6-29064
In the one disclosed in Japanese Unexamined Patent Publication No. 2 (1999), as shown in FIG. 8, a conductor 1 made of a long flat copper plate is attached to a flat harness 11.
3 is formed, and a circular hole 15 is formed in the conductor 13 to form a fuse portion 17 having a cross-section orthogonal to the current-carrying direction of the conductor 13 and having a partially small area. In the planar circuit bodies 1 and 11 in which the fuse portions 7 and 17 are directly formed, when an overcurrent tries to flow through the conductor, the fuse portions 7 and 17 having a small cross-sectional area are heated to a high temperature and melted, causing a disconnection. Was becoming.

Further, the fuse portion may be processed by etching in addition to the above punching process. In this method, a copper foil is laminated on an insulating base material, the fuse portion is masked in a desired shape, and unnecessary portions are melted and removed to produce a planar circuit body having a fuse portion with a predetermined cross-sectional area. Was.

[0004]

However, in the planar circuit body manufactured by the punching process described above, it is impossible to control the cross-sectional area of the fuse parts 7 and 17 and stably bring out the fusing characteristics required for the fuse. It was difficult. That is, the punching position has to be adjusted with high accuracy, and if the position shift occurs, the fusing characteristic of the fuse changes immediately. Moreover, in order to process the fuse parts 7 and 17 by punching, an expensive mold is used.
This is necessary for each circuit pattern, and there is a problem that the manufacturing cost increases. Further, since the flat conductor 13 in the flat harness 11 has a large surface area, it has a high heat dissipation property, and even if a large current flows and the fuse part 17 dissipates heat, it takes a long time to melt and the insulating material Melting, fuming,
There is a risk of ignition, and there is a problem that it is difficult to obtain a good function as a fuse. On the other hand, in the method of manufacturing the fuse portion by etching, although high dimensional accuracy can be obtained, it is limited to the manufacturing of the conductor thickness of 100 μm or less.
Originally, there was a problem that manufacture was difficult in a large current circuit that requires the most fuse. This is because reducing the etching area is an important factor for cost reduction in the manufacturing method of the printed wiring board, but when the conductor thickness is 100 μm or more, the amount of copper to be removed is large, which is economical and economical. This was because the speed was significantly reduced. The present invention has been made in view of the above circumstances, and a fuse portion having an arbitrary cross-sectional area can be easily formed without using a punching process that requires a die or etching that restricts the conductor thickness. An object of the present invention is to provide a method for manufacturing a planar circuit body that can be manufactured and a planar circuit body manufactured by the method, to secure good fusing characteristics, reduce manufacturing cost, and improve productivity.

[0005]

In order to achieve the above object, a method of manufacturing a planar circuit body according to the present invention has a desired circuit pattern on a substrate made of an insulating material and a width narrower than a conductor width of the circuit pattern. The method is characterized by including a step of printing the fuse portion using a conductive paste, a step of solidifying the printed conductive paste, and a step of subjecting the conductive paste to electrolytic copper plating. Further, the planar circuit body includes a base film made of an insulating material, a circuit pattern printed on the base film with a conductive paste, and a part of the circuit pattern having a width wider than a conductor width of the circuit pattern. The present invention is characterized by comprising a narrow fuse portion, copper plating deposited on the conductive paste, and tin plating deposited only on the fuse portion of the copper plating.

[0006]

In the method of manufacturing the planar circuit body, the circuit pattern is
The fuse portion is integrally formed, and a homogeneous fuse portion can be manufactured simultaneously with the conductor portion. Further, the conductor thickness is set by electrolytic plating, and it becomes possible to manufacture a planar circuit body in a wide conductor thickness range from a minute current circuit to a large current circuit. Furthermore, because the conductor thickness is set by electrolytic plating,
It is also possible to change the conductor thickness of each circuit by controlling the current density in one planar circuit body. Also,
By performing the plating process in multiple steps, it is possible to form a fuse part having a thickness different from that of the conductor part. In the planar circuit body, the fuse part is manufactured with high accuracy and homogeneity, and the fuse part is tin-plated, and when the fuse part generates heat, the electric resistance increases due to tin diffusion, and the good fusing time is short. Fuse characteristics can be obtained.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a method for manufacturing a planar circuit body and a planar circuit body according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining a manufacturing process of a planar circuit body according to the present invention, FIG. 2 is an enlarged view of a fuse portion after printing a conductive paste, FIG. 3 is an enlarged view of a tin-plated fuse portion, and FIG. 1 is a sectional view taken along the line AA of FIG. 1, FIG. 5 is a sectional view taken along the line BB of FIG. 1, and FIG. The method of manufacturing the planar circuit body 21 according to the present embodiment is
As shown in FIG. 1, first, a conductive paste 25 is printed in a desired circuit pattern shape by screen printing on a base film 23 serving as an insulating substrate.

At this time, the fuse portion 27 is printed on at least one place in the circuit. When the conductor thickness of the fuse portion 27 is the same as that of the circuit, the fuse portion 27 has a range of 50% to 10% of the circuit conductor width W as shown in FIG.
Preferably, it is formed by narrowing it to 45% to 30%.
Then, after the conductive paste 25 printed on the base film 23 is dried or cured to be solidified, the conductive paste 25 is subjected to electrolytic copper plating 26. The electrolytic copper plating 26 can be applied in a plating thickness range of 5 μm to 500 μm.

After the electrolytic copper plating is completed, the fuse portion 27 is partially tin-plated 29, as shown in FIG. The tin plating 29 is applied to the fuse portion 27 only by 1 μm or more. After tin plating 29 is applied to the fuse portion 27, an insulating coating 31 (see FIG. 4) is applied on the base film 23. The base film 23 provided with the insulating coating 31 is cut into a predetermined shape and formed into a desired planar circuit body 21.

That is, in the thus-fabricated planar circuit body 21, the conductor portion is formed in the state where the conductive paste 25, the copper plating 26, and the insulating coating 31 are laminated in this order as shown in FIG. To be done. On the other hand, the fuse portion 27
As shown in FIG. 5, the conductive paste 25, the copper plating 26, the tin plating 29, and the insulating coating 31 are laminated in a width narrower than that of a normal conductor portion.

In this manufacturing method, the circuit pattern is integrally formed including the fuse portion 27, and unlike the conventional punching process, the fuse portion 27 and the die are not required to be aligned with high precision, and a uniform pattern is obtained. The fuse portion 27 can be easily manufactured simultaneously with the conductor portion. Further, in this manufacturing method, since the conductor thickness can be set by electrolytic plating, it is possible to manufacture the planar circuit body 21 in a wide conductor thickness range from a minute current circuit to a large current circuit. Further, since the conductor thickness is set by electrolytic plating, one planar circuit body 21
It is also possible to change the conductor thickness of each circuit by controlling the current density to each circuit.
Further, it becomes possible to perform the plating step in a plurality of steps, and as shown in FIG. 6A, the fuse portion which can be formed only in the same thickness as the conductor portion by the conventional manufacturing method by etching is used. As shown in (b), the fuse portion 27 can be formed with a thickness different from that of the conductor portion. As a result, the fusing characteristic of the fuse portion 27 can be freely set according to the characteristic of the electric circuit.

In the thus-fabricated planar circuit body 21, the fuse portion 27 is manufactured with high accuracy and homogeneity, and the fuse portion 27 is tin-plated 29. When heat is generated, the electrical resistance increases due to tin diffusion, and good fuse characteristics with a short fusing time can be obtained.

According to the method for manufacturing the planar circuit body 21 described above, after the conductive paste 25 is transferred onto the base film 23 by screen printing, the conductive paste 25 is subjected to electrolytic copper plating 26. , The conductor thickness is 5μ
It can be formed in a wide range of m to 500 μm, and the conductor thickness can be changed for each circuit in one product. Further, by dividing the plating process into a plurality of processes, it is possible to set the fuse portion 27 having an arbitrary thickness different from that of the conductor portion. This eliminates the need to provide an expensive mold for each circuit pattern, and also eliminates the need for mold alignment, resulting in high dimensional accuracy.
Stable fusing characteristics can be obtained.

Further, in the planar circuit body 21 manufactured by the manufacturing method according to the above-described embodiment, the fuse portion 27 is tin-plated 29, so that the fusing time can be shortened by tin diffusion at the time of heat generation, Even in a flat conductor having a large surface area, the fusing property is good.

In the manufacturing method of this embodiment, the case where the fuse portion 27 is tin-plated 29 has been described as an example. However, in the manufacturing method of the present invention, the tin-plating 29 is not performed and the fuse pattern 27 is printed in a predetermined pattern. Of course, the fuse portion 27 may be formed only by performing electrolytic plating on the conductive paste portion.

[0016]

As described in detail above, according to the method for manufacturing a planar circuit body of the present invention, the conductive paste on the screen-printed base film is subjected to electrolytic copper plating. The thickness of the conductor can be formed in a wide range from thin to thick. Further, by dividing the plating process into a plurality of processes, it is possible to set a fuse portion having an arbitrary thickness different from that of the conductor portion. As a result, it is possible to obtain a fuse portion having high dimensional accuracy and stable fusing characteristics, and to eliminate the use of a mold, so that it is possible to reduce the manufacturing cost and improve the productivity. Also,
According to the planar circuit body, since the fuse part is tin-plated, the fusing time can be shortened, and even in the case of a flat conductor with a large surface area, the fusing characteristics are good, and the insulation material is melted, smoked, and ignited. Can be prevented.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a manufacturing process of a planar circuit body according to the present invention.

FIG. 2 is an enlarged view of a fuse portion after printing a conductive paste.

FIG. 3 is an enlarged view of a tinned fuse portion.

FIG. 4 is a sectional view taken along line AA of FIG. 1;

FIG. 5 is a sectional view taken along line BB of FIG. 1;

FIG. 6 is a comparison diagram of a conductor thickness with a conventional one.

FIG. 7 is a perspective view of a conventional planar circuit body in which a fuse portion is formed by punching holes.

FIG. 8 is a perspective view of a conventional planar circuit body in which a fuse portion is formed by punching holes.

[Explanation of symbols]

 21 planar circuit body 23 base film 25 conductive paste 26 copper plating 27 fuse part 29 tin plating

Claims (5)

[Claims] 1. A step of printing a desired circuit pattern and a fuse portion having a width narrower than a conductor width of the circuit pattern using a conductive paste on a substrate made of an insulating material, and solidifying the printed conductive paste. And a step of subjecting the conductive paste to electrolytic copper plating. 2. The method for manufacturing a planar circuit body according to claim 1, wherein the conductive paste is plated with electrolytic copper, and then only the fuse portion is plated with tin. 3. The planar circuit body according to claim 1, wherein the electrolytic copper plating is performed in a plurality of steps to form the fuse portion with a thickness different from a conductor thickness of the circuit pattern. Manufacturing method. 4. The method for manufacturing a planar circuit body according to claim 1, wherein conductors having different plating thicknesses are formed by changing a current density to an arbitrary conductor in one planar circuit body. . 5. A base film made of an insulating material, a circuit pattern printed with a conductive paste on the base film, and a fuse formed in a part of the circuit pattern and having a width narrower than a conductor width of the circuit pattern. A planar circuit body comprising: a portion, copper plating deposited on the conductive paste, and tin plating deposited only on the fuse portion of the copper plating.