JPH0529502A - Printed board - Google Patents

Abstract

PURPOSE:To improve the heat dispersion efficiency of a surface mount LSI, by diffusing heat generated from an LSI chip, to the whole substrate from the whole rear of the LSI chip, directly via a metal plate. CONSTITUTION:A first metal plate 8 for heat dispersion which is sandwiched by insulators 1 of a wiring board, and can move parallel with a parts fixing surface, and an aperture part 11 which is formed for connecting a second metal plate 9 for heat dispersion fixed on the rear of a surface mount LSI chip 7, and penetrates the printed board from the surface to the rear are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board,
In particular, the present invention relates to a printed circuit board that enhances the heat dissipation effect of a surface mount LSI.

[0002]

2. Description of the Related Art Conventionally, a printed circuit board of this type is shown in FIG.
As shown in (a), a metal plate 30 for lowering the thermal resistance of the board is sandwiched inside the insulator 29 of the printed board in parallel with the component mounting surface. The heat generated from the surface-mounted LSI chip 28 thus generated is connected to the leads 25 connected around the chip.
It was supposed to diffuse to the printed circuit board through.

FIG. 3 (b) shows L in addition to the example of FIG. 3 (a).
In this example, a heat sink 31 is attached to the upper surface of the sealing resin 27 of the SI chip to enhance the heat radiation effect.

[0004]

In this conventional printed circuit board, the LSI chip and the metal plate sandwiched by the insulators of the printed circuit board cannot be connected to each other.
The heat generated from the chip diffuses to the printed board through the thin leads connected around the LSI chip.
Therefore, since the heat dissipation of the LSI chip is poor and it usually has a thermal resistance of about 50 ° C./W, the temperature of the LSI chip rises to 95 ° C. at an ambient temperature of 70 ° C. when a CMOS LSI operating at 20 MHz and 0.5 W is mounted. Then, the maximum operating temperature is reached. Therefore, there is a problem that an LSI that consumes more power than the above-mentioned LSI cannot be mounted.

In order to avoid the above problems, the LS
There is also a conventional example in which a heat sink is attached to the upper surface of the I chip, but this has a problem that a large mounting space is required and the device cannot be downsized.

[0006]

The printed circuit board of the present invention includes a first heat radiating metal plate which is sandwiched inside an insulator of the board and is movable in parallel with a component mounting surface, and the first heat radiating metal plate. And a second heat-dissipating metal plate attached to the back surface of the surface-mounting LSI, the opening portion penetrating from the front surface to the back surface of the printed circuit board.

[0007]

The present invention will be described below with reference to the drawings. 1 (a), 1 (b) and 1 (c) show a TAB (tape automa) using a printed circuit board according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view showing a procedure for mounting a ted bonded) LSI. A metal plate 9 is fixed to the back surface of the TABLSI chip 7, and the leads 4 of the TABLSI are connected to the conductive film 2 of the printed board by a known technique. Next, the metal plate 8 sandwiched between the insulators 1 of the printed circuit board is moved so as to come into contact with the metal plate 9 fixed to the back surface of the LSI chip 7 at the opening 11 of the printed circuit board. Next, the contact surfaces of the metal plate 9 and the metal plate 8 are joined by soldering so that the heat generated from the LSI chip 7 is directly guided to the metal plate 9.

FIG. 2A shows a printed circuit board according to the present invention with TA
FIG. 2 is a plan view showing an example in which a BLSI is incorporated into a device after mounting, and FIG. 2B is a sectional view taken along line AA of FIG. By extending the metal plate 8 sandwiched between the insulators 1 of the printed circuit board to the outside of the printed circuit board and providing screw holes 14 and screwing it into the metal case 12 outside the printed circuit board, the heat of the metal plate 8 is transferred to the printed circuit board. Leading to the outside.

According to this embodiment, the heat generated by the LSI chip is radiated directly through the metal without passing through the high thermal resistance portion, so the thermal resistance is 10 ° C./W or less, although it depends on the type of metal. . 20MHz operation 0.5W CMOS LSI mentioned above
In the above, if the same chip temperature rise is allowed, up to 2.5 W is allowed, and high-speed operation with the same chip is possible. Alternatively, the above-mentioned 5 times larger L
It is also possible to implement SI, and in that case, it can contribute to downsizing of the entire apparatus.

[0010]

As described above, according to the present invention, the first heat radiating metal plate sandwiched inside the insulator of the printed circuit board and movable parallel to the component mounting surface, and the surface mounting L.
Since the second heat-dissipating metal plate attached to the back surface of the SI can be connected at the opening of the printed circuit board, the LSI
The heat generated from the chip is not
Since it is diffused from the entire back surface of the I-chip directly to the entire substrate through the metal plate, the thermal resistance is 1/5 or less of the conventional one.
The permissible heat generation amount per mounting location is improved, it becomes possible to operate at higher speed and to mount a large-scale LSI in a narrow area, and it is possible to simultaneously realize miniaturization and high performance of the device.

[Brief description of drawings]

FIG. 1 is a perspective view of a printed circuit board according to an embodiment of the present invention, TA
It is sectional drawing which shows the procedure of mounting BLSI.

2A and 2B are diagrams showing an example in which a printed circuit board is incorporated into an apparatus, in which FIG. 2A is a plan view and FIG. 2B is a sectional view taken along line AA in FIG. 2A.

FIG. 3 is a cross-sectional view showing a conventional example.

[Explanation of symbols]

 1,29 Insulator 2,23 Conductive film 3,10,24 Solder 4,25 Lead 5,26 Bump 6,27 Encapsulating resin 7,28 LSI chip 8,9,30 Metal plate 11 Opening 12 Metal case 13 Screw 14 screw hole 31 heat sink

Claims (1)

Claim: What is claimed is: 1. A first heat-dissipating metal plate sandwiched inside an insulator of a substrate and movable parallel to a component mounting surface, and the first heat-dissipating metal plate and surface. A printed circuit board comprising: an opening penetrating from the front surface to the back surface of the printed circuit board, which is provided to connect the second heat dissipation metal plate attached to the back surface of the mounting LSI.