JPH07221411A - Printed circuit board and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a low-cost, small printed-circuit board, which allows large current to flow locally. CONSTITUTION:High-current conductor patterns 2 and low-current conductor patterns 3 are formed on a substrate 1. The high-current conductor patterns are rectangular pieces of copper foil that overlap the low-current conductor patterns in a predetermined manner, and they are connected by soldering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board, and more particularly to a printed wiring board capable of locally supplying a large current and a method for manufacturing the same.

[0002]

2. Description of the Related Art Generally, a printed wiring board electrically connected to a power semiconductor element that drives a large current has a wiring pattern for a large current through which a main current of the power semiconductor element flows and a control current for the power semiconductor element. And a wiring pattern for a small current for passing the like. The wiring pattern for a large current needs to have a large cross-sectional area in order to prevent heat generation. As one means for that, as shown in FIG. 5, the thickness of the wiring pattern 12 of the printed wiring board 11 is set to the standard. The printed wiring board may be formed to be thicker than the maximum thickness (105 μm), for example, about 1 mm.

Further, as in the above structure, as a means for increasing the cross-sectional area of the large current wiring pattern of the printed wiring board, as shown in FIG. 6, the width of the large current wiring pattern 22 is set to the small current wiring. It is also formed to be wider than the pattern 23. However, since the printed wiring board 11 having the thick wiring pattern 12 as shown in FIG. 5 is not available as a standard product, it has to be specially manufactured by etching or machining, which increases the cost of the printed wiring board 11. Was one of the causes.
Further, when the wiring pattern 22 for large current having a wide width as shown in FIG. 6 is provided, the area of the entire printed wiring board 21 becomes large, and the printed wiring board 21 becomes large. It was happening.

As measures against these problems, for example (Japanese Patent Laid-Open No. 62-2591) and (Japanese Patent Laid-Open No. 63-96).
995) and (Japanese Patent Application Laid-Open No. 1-253293). This configuration
By applying a thick film of copper plating only to the large-current circuit wiring on the printed wiring board, it becomes possible to locally flow a large current, and the printed wiring board can be made higher in density, that is, downsized. It has become a thing.

[0005]

However, even in this configuration, since the manufacturing process of the printed wiring board includes the step of applying copper plating, the manufacturing process of the printed wiring board composed only of the wiring pattern for the small current is When compared, there was a problem that the production efficiency was low. The present invention has been made to solve the above problems, and an object thereof is to enable miniaturization of a printed wiring board capable of locally supplying a large current and to efficiently and inexpensively manufacture the same. It is to be able to do it at cost.

[0006]

In order to solve the above problems, the invention according to claim 1 provides a wiring pattern for a small current and a thin plate-shaped conductor on a printed wiring board or a wiring pattern for a small current. The gist of the present invention is that a printed wiring board is composed of a large-current wiring pattern provided by joining.

According to a second aspect of the present invention, a step of forming a wiring pattern for a small current on a printed wiring board, and a wiring pattern for a large current and a surface mount component made of a thin plate conductor are provided by an electronic component mounting device. The gist is a method for manufacturing a printed wiring board, which comprises a step of mounting on a board or a wiring pattern for a small current via a bonding member.

[0008]

Therefore, according to the first aspect of the present invention, first, a wiring pattern for a small current is formed on the printed wiring board by etching or the like. Next, a thin plate-shaped conductor is bonded onto a printed wiring board or a wiring pattern for a small current to form a wiring pattern for a large current.

According to the second aspect of the present invention, first, a wiring pattern for a small current is formed on the printed wiring board by etching or the like. Next, a large-current wiring pattern made of a thin plate conductor is mounted on the substrate or a small-current wiring pattern via a joining member using an electronic component mounting device as in the mounting process of surface mounting components. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment in which the present invention is embodied in a printed wiring board on which a power semiconductor element for controlling a small motor of an automobile is mounted will be described with reference to FIGS. Board 1
Is formed of glass epoxy resin, and a wiring pattern 2 for large current and a wiring pattern 3 for small current are respectively formed on the surface thereof to form a printed wiring board 4. The wiring pattern 2 for a large current is formed by forming a wiring pattern 3 for a small current and further joining a substantially rectangular copper foil 2a as a thin plate conductor by soldering.

The power semiconductor element 5 is electrically connected to the wiring pattern 2 for large current by a wire 6.
Therefore, the main current of the power semiconductor element 5 flows through the wiring pattern 2 for large current. The power semiconductor element 5 is joined to the die pad 7 on the substrate 1 by solder 9 and electrically connected to a small motor of an automobile (not shown) so as to drive and control the small motor.

A surface mount component 8 such as a chip resistor is mounted on the wiring pattern 3 for small current by solder 9. The power semiconductor element 5 is electrically connected to the wiring pattern 3 for a small current via a wire 10. Therefore, the power semiconductor element 5 is drive-controlled according to a control signal from a signal processing circuit (not shown).

Next, a method of manufacturing the printed wiring board 4 having the above structure will be described. First, a wiring pattern 3 for a small current is formed on a substrate 1 by etching a copper plate. Next, cream solder is applied to a predetermined position where the surface mount component 8 on the wiring pattern 3 for small current and the copper foil 2a as the wiring pattern 2 for large current are joined. Then, the surface mount component 8 and the copper foil 2a are placed on the cream solder by an electronic component mounting device (hereinafter simply referred to as a mounter). After that, the surface mount component 8 and the copper foil 2a are bonded to the substrate 1 by reflow or the like, and then the power semiconductor element 5 and the wiring patterns 2 and 3 for large current and small current are electrically connected by the wires 6 and 10. Connecting.

At this time, since the copper foil 2a is formed in a substantially rectangular shape as described above, it can be supplied to the production process in a taped state like the surface mount component 8. Therefore, the mounter used in the mounting process of the surface mount component 8 can be shared in the bonding process of the copper foil 2a, and there is no need to increase new processes and facilities when forming the wiring pattern 2 for large current. , The production efficiency can be increased.

As described above, according to this embodiment, the wiring pattern 2 for a large current is the copper foil 2a and the wiring pattern 3 for a small current.
Since it is formed by bonding to, it is not necessary to form the wiring pattern 2 for large current in a wide width, and the printed wiring board 4 can be downsized. Also, since the copper foil 2a can be joined using an existing mounter, it does not lead to an increase in cost, and the production efficiency can be improved.

The present invention is not limited to the above embodiment, but may be modified as follows without departing from the spirit of the present invention. (1) In the above embodiment, the copper foil 2a was used as the thin plate conductor, but the thickness thereof is not particularly limited, and may be what is called a copper plate or a copper thin film. You may make it select according to the amount of flowing currents by making use of the fact that each thickness is different.

The conductive material is not particularly limited to copper, but may be a conductor made of aluminum or the like, for example. In this case, by using the same material for the wiring pattern 2 for large current and the wiring pattern 3 for small current, the contact resistance at the joint portion between the two can be lowered. (2) In the above embodiment, the wiring pattern 2 for large current was formed by joining the copper foil 2a on the wiring pattern 3 for small current, but as shown in FIG. 3, it is a thin plate-shaped conductor. The wiring pattern 2 for large current may be configured only with a certain copper foil 2a. In this case, the adhesive 9a is used to bond the copper foil 2a to the substrate 1. The adhesive 9a is not particularly limited in terms of conductivity and the like, but when an adhesive made of epoxy resin filled with a ceramic having a high thermal conductivity, such as beryllia, is used, the adhesive 9a has a large size. The heat dissipation of the current wiring pattern 2 can be improved. In the case of this embodiment, it is necessary to make the thickness of the copper foil 2a larger than that of the above-mentioned embodiment. Further, also in this embodiment, the thin plate conductor is not limited to the copper foil 2a, but may be a copper plate or a copper thin film.

(3) In the above embodiment, the substrate 1 of the printed wiring board 4 is made of glass epoxy resin, but the material is not particularly limited,
It may be applied to the case of a ceramic substrate or the like. in this case,
Since the ceramic substrate has good heat resistance, reliability when the power semiconductor element 5 generates heat is further enhanced. (4) In the above-described embodiment, the copper foil 2a, which is a thin plate-shaped conductor, having a constant thickness is used at a plurality of locations, but the invention is not particularly limited to this, and the following changes may be made. Good.

That is, as shown in FIG. 4, a plurality of thin plate-shaped conductors 2a may be stacked and mounted to adjust the thickness. In these cases, an optimal wiring shape can be formed according to each part of the wiring pattern, and when a plurality of sheets are stacked and mounted, a thin plate-shaped conductor 2a having a single thickness can be used, which leads to low cost. It is possible to improve productivity together.

[0020]

As described in detail above, according to the first aspect of the present invention, it is possible to miniaturize a printed wiring board capable of locally supplying a large current, and to achieve high efficiency and low cost. There is an excellent effect that a printed wiring board can be manufactured. According to the invention described in claim 2, the step of joining the thin plate-shaped conductors forming the wiring pattern for the large current can be performed at the same time as the step of mounting the surface mount component, so that the production efficiency of the printed wiring board can be improved. It has an excellent effect.

[Brief description of drawings]

FIG. 1 is a partially omitted plan view showing an embodiment embodying the present invention.

2 is a cross-sectional view taken along the line AA of the printed wiring board in FIG.

FIG. 3 is a sectional view of a printed wiring board showing another embodiment of the present invention.

FIG. 4 is a sectional view of a printed wiring board showing another embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a conventional printed wiring board.

FIG. 6 is a partially omitted plan view showing a conventional printed wiring board.

[Explanation of Codes] 1 ... Board, 2 ... Wiring pattern for large current, 2a ... Copper foil,
3 ... Wiring pattern for small current, 4 ... Printed wiring board,
9 ... Solder as a joining member, 9a ... Adhesive as a joining member.

Claims (2)

[Claims] 1. A printed wiring board comprising a wiring pattern for a small current and a wiring pattern for a large current provided by joining a thin plate-shaped conductor on the printed wiring board or a wiring pattern for a small current. 2. A step of forming a wiring pattern for a small current on a substrate, and a wiring pattern for a large current consisting of a thin plate-shaped conductor and a surface mount component for a printed wiring board or a small current by an electronic component mounting device. A method of manufacturing a printed wiring board, comprising the steps of mounting on a wiring pattern via a joining member.