Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Patent
1992-03-26
1993-11-16
Thompson, Gregory D.
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
165 803, 165185, 174 163, 361690, 361707, 257712, H05K 720
Patent
active
052629228
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a heat radiation structure for a semiconductor device to be surface-mounted on a printed circuit board.
DESCRIPTION OF THE RELATED ART
As shown in FIG. 8, an electronics apparatus, such as a telecommunication apparatus, comprises a box-like shelf 100 in which a plurality of printed circuit boards 102, each provided with semiconductor devices 101, such as LSI or others, are accommodated in parallel to each other. In line with recent developments in the surface-mounting technology, electronics parts have been miniaturized and can be installed on the printed circuit board at a high density, while keeping the height thereof at a low level. Nevertheless, there is a need for the provision of a heat-radiation fin 101b, for effectively cooling the semiconductor device, because the heat generated by the semiconductor device 101 increases as the degree of integration thereof increases, but this makes the mounting height H of the semiconductor device 101 larger. Accordingly, the pitch of (i.e., the space between) the adjacent printed circuit boards 102 in the shelf must be made larger, to receive this height, and this contradicts the primary object of reducing the total size of the electronics apparatus by the miniaturization of the electronics parts.
Further, when the semiconductor device is installed on the printed circuit board by an automatic mounting machine, the height of the heat-radiation fin inhibits the effective operation of the automatic mounting machine.
To suppress the increase of the installation height of the semiconductor device, a structure is proposed in which, as shown in FIG. 9, an opening 103 is formed in the printed circuit board 102, through which a heat-conductive member 104 adhered to a backside of the semiconductor device 101 protrudes from the back surface of the printed circuit board 102, and a heat-radiation plate 105 is fixed on a protruding end surface of the heat-conductive member 104 by screws 106. According to this structure, a heat-radiation fin can be eliminated whereby the height of the semiconductor device is substantially decreased. Moreover, both surfaces of the printed circuit board 102 can be utilized as an area for mounting electronics parts.
This structure, however, has a drawback in that the screw 106 is utilized for fastening the heat-radiation plate 105 to the heat-conductive member 104, which causes the assembly/disassembly thereof troublesome and reduces the mounting space in the height direction to an extent corresponding to the protrusion of the screw head. Furthermore, if a relative position of the heat-conductive member 104 and the semiconductor device 101, which are adhered to each other, has not been correctly controlled, a threaded hole on the heat-conductive member 104 and that on the heat-radiation plate 105 may not be aligned with each other, and this results in a failure of the screwing operation or in an excessive stress on leads of the semiconductor device, which may cause a bad contact of the leads.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above problems of the prior art by further reducing a mounting height of a semiconductor device on a printed circuit board to thereby increase the accommodation density of printed circuit boards in a shelf so that a compactness of an electronics apparatus is enhanced as a whole.
Another object of the present invention is to provide a heat radiation structure for the electronics apparatus in which the mounting/dismounting operation of a heat-radiation fin, or plate, is easily carried out.
These objects of the present invention will be achieved by a heat-radiation structure for cooling a semiconductive device, such as an LSI, mounted on a surface of a printed circuit board so that an opening formed in a predetermined area of the printed circuit board exposes the bottom surface of the semiconductor device, which is brought into tight contact with a heat-conductive member so that an end surface of the heat-conductive member is
REFERENCES:
patent: 3958155 (1976-05-01), Bagholtz et al.
patent: 4150440 (1979-04-01), Bonnie et al.
Hongho Tomoyuki
Kanno Takashi
Magome Riichi
Sato Takashi
Yamaji Hiroshi
Fujitsu Limited
Thompson Gregory D.
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