JPH0660163U - Heat dissipation type double sided circuit board - Google Patents

Abstract

(57) [Summary] [Construction] A printed circuit board 3 having two component mounting areas 3a, 3b and a flexible crossover wiring area 3c for electrically connecting the two component mounting areas 3a, 3b.
The flexible crossover wiring region 3c was bent into a U shape, and the two component mounting regions 3a and 3b were bonded to both surfaces of the heat dissipation metal plate 1 sandwiched therebetween. [Effect] Since the component mounting area of the printed circuit board adhered to both sides of the heat dissipation metal plate is electrically connected by the flexible transition wiring area, a through hole penetrating the heat dissipation metal plate as in the conventional case. Since it is not necessary to form the heat-dissipating double-sided circuit board, the heat-releasing double-sided circuit board is easily manufactured, and the reliability is improved.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a heat radiation type double-sided circuit board in which printed circuit boards are arranged on both sides of a heat radiation metal plate.

[0002]

[Prior art]

 When mounting heat-generating components such as power transistors on the printed circuit board, use a heat-radiating circuit board in which the printed circuit board is bonded to a heat-dissipating metal plate, and use the heat-generating parts of the heat-generating components through the holes formed in the printed circuit board. Is directly bonded and fixed to the metal plate for heat dissipation, and the leads of heat-generating components are soldered to the pads of the printed circuit board.

The heat dissipation type circuit board generally has a structure in which a printed circuit board is adhered to one surface of a heat dissipation metal plate. However, when miniaturization and high density of equipment are required, the heat dissipation metal plate is used. A heat-dissipating double-sided circuit board in which printed circuit boards are adhered to both surfaces of An example of a conventional heat radiation type double-sided circuit board is shown in FIG. In the figure, 1 is a metal plate for heat dissipation, such as an aluminum plate, 3A and 3B are printed circuit boards bonded to both sides of the metal plate 1 for heat dissipation with an epoxy adhesive or a heat conductive adhesive (not shown). Reference numeral 5 is a heat generating component. The printed circuit boards 3A and 3B have a multilayer structure having a plurality of copper foil circuit conductors 7.

In the heat dissipation type double-sided circuit board, through holes 9 are formed at appropriate positions because the printed circuit boards 3A and 3B on both sides need to be electrically conducted. Since the through hole 9 penetrates the conductive metal plate 1, it must be electrically insulated from the metal plate 1. Therefore, when forming the through hole 9, a large hole is formed in the metal plate 1, the hole is filled with an epoxy resin 11, and after curing, a hole for forming the through hole 9 is further formed in the epoxy resin 11. After that, the inner surface of the hole is plated with copper.

Holes are preliminarily formed in the printed circuit boards 3 A and 3 B at positions where the heat-generating components 5 are mounted, and the heat-generating portions 5 a of the heat-generating components 5 are radiated by the heat conductive adhesive 13 through the holes. It is directly adhered and fixed to the metal plate 1. The leads 5b of the heat generating component 5 are connected to the pads 15 of the printed circuit boards 3A and 3B by soldering.

A flat hole is formed in the heat radiating metal plate 1, and a flat heat pipe 17 is inserted into the flat hole. A heat conductive adhesive 19 is filled between the heat pipe 17 and the heat radiating metal plate 1 so that no gap is formed. The heat radiating portion of the heat pipe 17 projects from the heat radiating metal plate 1, and a heat radiating fin is formed in the heat radiating portion.

With the structure as described above, the heat generated in the heat-generating component 5 is transmitted to the heat-dissipating metal plate 1, absorbed by the heat-absorbing portion of the heat pipe 17, and sent to the heat-dissipating portion. The heat is dissipated from the heat dissipating part. Therefore, excellent heat dissipation characteristics can be obtained even in the structure having the printed circuit boards 3A and 3B on both surfaces of the heat dissipation metal plate 1.

[0008]

[Problems to be solved by the device]

 In the conventional heat dissipation type double-sided circuit board, printed circuit boards on both sides are electrically connected by through holes, but in this structure, it is necessary to electrically insulate the heat dissipation metal plate and the copper plating of the through holes. Therefore, since it is necessary to form a resin layer for insulation on the inner surface of the hole formed in the heat dissipation metal plate, it takes time and effort to form the through hole, resulting in a high cost. Further, if voids or the like are generated in the resin layer provided on the inner surface of the hole of the heat-dissipating metal plate, the insulating property is significantly deteriorated, which causes a problem in reliability.

[0009]

[Means for Solving the Problems]

 The present invention provides a heat-dissipating double-sided circuit board that solves the above-mentioned problems, and has a structure in which two component mounting areas and a flexible crossover wiring area electrically connecting the two component mounting areas are provided. In the printed circuit board having the above, the flexible wiring area is bent in a U shape, and the heat radiation metal plate is sandwiched between the two component mounting areas, and the two component mounting areas are provided on both sides of the heat radiation metal plate. It is characterized by being adhered to.

[0010]

[Action]

 By doing so, the two component mounting areas of the printed circuit board, which are bonded to both sides of the heat dissipation metal plate, are electrically connected by the flexible crossover wiring area, so that the heat dissipation metal plate is penetrated as in the conventional case. It is no longer necessary to form a through hole to eliminate the conventional problem.

[0011]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 and 2 show an embodiment of the present invention. This heat-dissipating double-sided circuit board does not use two printed circuit boards as in the past, but electrically connects the two component mounting areas 3a and 3b to the two component mounting areas 3a and 3b. A single printed circuit board 3 having a flexible crossover wiring area 3c is used.

The component mounting areas 3a and 3b have a multilayer structure in which a plurality of copper foil circuit conductors 7 are formed, but the flexible crossover wiring area 3c has one side (or both sides) of the thin insulating sheet 21 as shown in FIG. It is in the form of a flexible sheet in which parallel wiring conductors 23 for electrically connecting the two component mounting areas 3a and 3b are formed. The flexible crossover wiring region 3c is bent in a U shape, and the heat radiation metal plate 1 is sandwiched between the two component mounting regions 3a and 3b, and the two component mounting regions 3a and 3b are provided on both sides of the heat radiation metal plate 1. It is attached.

Since the other structure is similar to that of the heat dissipation double-sided circuit board of FIG. 5 described above, the same parts are designated by the same reference numerals and the description thereof will be omitted. Next, a method of manufacturing the heat dissipation type double-sided circuit board as described above will be described. First, the printed circuit board 3 is manufactured as shown in FIG. That is, for example, a flexible printed circuit sheet 25 in which the circuit conductor 7 and the parallel wiring conductor 23 are formed by pattern etching of copper foil on both sides of a flexible thin insulating sheet 21 made of a glass cloth epoxy resin sheet having a thickness of about 50 μm A copper foil 29 is manufactured and laminated on both surfaces of the parts corresponding to the component mounting areas 3a and 3b through a prepreg sheet 27, and hot pressed to integrate the whole.

Next, the copper foil 29 is pattern-etched to form circuit conductors having a required pattern on both surfaces, so that the component mounting areas 3a and 3b become rigid multi-layer circuit boards having four-layer circuit conductors. Then, the component mounting areas 3a and 3b are subjected to drilling, through-hole plating, etc. to complete the printed circuit board 3.

Next, the flexible crossover wiring region 3c of the printed circuit board 3 is bent into a U shape as shown in FIG. 4, and the prepreg sheet 31A and the heat radiating metal plate are placed between the two component mounting regions 3a and 3b. The laminated body of 1 and the prepreg sheet 31B is sandwiched and hot pressed. It should be noted that the prepreg sheets 31A and 31B are also preliminarily formed with holes at the portions where the heat-generating components are mounted. By this hot pressing, the two component mounting areas 3a and 3b are adhered to both sides of the heat-dissipating metal plate 1, and the heat-dissipating double-sided circuit board as shown in FIG. 1 can be obtained.

In order to protect the bent flexible crossover wiring area 3c, a viscous solder resist is applied to the flexible crossover wiring area 3c, dried and cured, and a cover lay is applied. Is effective. In addition to the thin glass cloth epoxy resin sheet, for example, a polyimide film or the like can be used as the insulating sheet 21 serving as a base material of the flexible crossover wiring region 3c.

Further, in the embodiment of FIG. 1, the heat pipe 7 is arranged inside the heat-dissipating metal plate 1, but the heat pipe 7 can be omitted when the amount of heat dissipation is small. Instead of providing the heat pipe, it is also possible to provide a structure in which the component mounting region of the printed circuit board is not adhered to the metal plate for heat dissipation and the heat dissipation fin is attached thereto by adhesion or brazing.

[0018]

[Effect of device]

 As described above, according to the present invention, the component mounting area of the printed circuit board adhered to both sides of the heat dissipation metal plate is electrically connected by the flexible crossover wiring area. Since it is not necessary to form a through hole penetrating the heat dissipation metal plate, there is an advantage that the heat dissipation type double-sided circuit board can be easily manufactured and the reliability is improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a heat dissipation type double-sided circuit board according to the present invention.

FIG. 2 is a perspective view showing a main part of the heat dissipation type double-sided circuit board of FIG.

3 is a cross-sectional view showing a first step of a method of manufacturing the heat dissipation double-sided circuit board of FIG.

FIG. 4 is a sectional view showing a second stage of the same.

FIG. 5 is a cross-sectional view showing a conventional heat radiation type double-sided circuit board.

[Explanation of symbols]

1: Metal plate for heat dissipation 3: Printed circuit board 3a, 3b: Component mounting area 3c: Flexible crossover wiring area 5: Heating component 7: Circuit conductor 17: Heat pipe 21: Insulation sheet
23: Parallel wiring conductor

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Creator Kenzo Kobayashi 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (1)

[Scope of utility model registration request] 1. A printed circuit board having two component mounting areas and a flexible crossover wiring area for electrically connecting the two component mounting areas, wherein the flexible crossover wiring area is bent into a U shape, A heat-dissipating double-sided circuit board, characterized in that a heat-dissipating metal plate is sandwiched between two component mounting areas, and two component-mounting areas are bonded to both sides of the heat-dissipating metal plate.