Stock material or miscellaneous articles – All metal or with adjacent metals – Having variation in thickness
Patent
1999-01-26
2000-10-31
Jones, Deborah
Stock material or miscellaneous articles
All metal or with adjacent metals
Having variation in thickness
428547, 419 28, 361709, 264274, B22F 324, B22F 500, H01L 2336
Patent
active
061399752
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a sheet member and a method of manufacturing such a sheet member by the powder metallurgical method, specific examples of which sheet member includes a heat dissipating plate such as a heat spreader, a heat sink, or the like, with or without fins. The present invention also relates to such a heat dissipating plate.
BACKGROUND ART
Recently, in the field of semiconductor technologies, integrated circuit boards (IC) have been demanded to become a highly integrated design and a widely versatile design. Along with this tendency, IC packages for placing an IC chip thereon have also been remarkably rapidly enhanced in their performance such as, for example, small design, increased capacity, thin design, increased number of pins, and the like. As the performance has been enhanced, their heating value also tended to be consistently increased. For example, IC packages having a heating value of several W have been increasingly provided with a heat dissipating plate called "heat spreader". IC packages having such a large heating value as exceeding 10 W have been increasingly provided with a heat dissipating plate called "heat sink".
For example, the heat spreader is typically a regular square sheet having a side length dimension of about 25 to 45 mm and a thickness of about 0.5 to 1.0 mm and has a recess formed in the center of its single surface which recess is intended for an IC to be placed therein. Such a heat spreader is mounted on a substrate with an IC placed thereon and molded with resin so as to form an IC package. In that state of the IC package, the surface of the heat spreader is exposed outside to dissipate heat. Some heat spreaders are formed on their upper surface or lower surface with fins which are adapted to enhance the effect of heat dissipation or heat absorption. Fins are sometimes formed on a lower surface of each heat spreader which lower surface is embedded in resin. A plurality of holes for filling the resin therein are also occasionally formed in the lower surface of the heat spreader, so that the heat spreader will not peel off the resin. Conventionally, such heat spreaders are produced by plastic working, for example, punching, drawing, rolling a metal sheet with high thermal conductivity, such as copper, aluminum, or the like. The aforementioned heat sink is, in use, placed on the IC package on which the heat spreader is placed, in order to further enhance the heat dissipation of the heat spreader. Such heat sinks are also produced likewise by plastic working, for example, bending, extruding, punching a metal sheet with high thermal conductivity, such as aluminum, or the like. In particular, in the case that the fins are comparatively large in height, they are conventionally formed by engraving through machining.
As previously discussed, IC packages have been tended to be consistently increased in heating value. Along with this tendency, more enhanced effect of heat dissipation for heat spreaders and heat sinks has naturally been increasingly demanded. One approach was made for this purpose to increase the number and length dimension of the fins. However, it is difficult to increase the number and length dimension of the fins by the plastic working technique. If machining is employed in order to obviate this shortcoming, another shortcoming is encountered in that the cost is increased. Additionally, there is still another shortcoming in that the holes formed in the heat spreader for the purpose of preventing the heat spreader from peeling off resin is not good enough when a large force is applied or in other similar cases.
With plastic working, distortion created during plastic working occasionally inevitably remains in final products in the form of residual stress. If such residual stress is left as it is, the heat spreader would be warped or flexed because the residual stress is released by heat when a circuit is formed on a substrate on which the heat spreader is placed, by bonding, or the like. Such deformation has the risk to degrade the a
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patent: 5049184 (1991-09-01), Harner et al.
patent: 5481136 (1996-01-01), Kohmoto et al.
patent: 5783316 (1998-07-01), Colella et al.
patent: 6035524 (2000-03-01), Suppa et al.
Ichikawa Jun-ichi
Ishijima Zenzo
Mawatari Osamu
Shikata Hideo
Hitachi Powered Metals Co., Ltd.
Jones Deborah
Savage Jason
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