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Technique for Manufacturing High-Aspect-Ratio Finned Ceramic Caps

IP.com Disclosure Number: IPCOM000038562D
Original Publication Date: 1987-Feb-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Hultmark, EB: AUTHOR

Abstract

A procedure has been developed which uses injection molding to produce finned cap/heatsinks with a high aspect ratio for use in semiconductor modules. A top strap structure is used to support the fins during firing which reduces any warping tendency. In producing finned ceramic caps/heatsinks an aspect ratio of 4:1 has been a limiting factor. The aspect ratio is the fin height 1 (Fig. 1) of the cap 2 relative to the fin width 3 and spacing 4. This limitation occurs because the ceramic powder and binders are forced into a mold using a pressed technique which results in a non-uniform density. When fired, warpage and breakage of the fins may result. The injection molding technique proposed makes it possible to produce caps with high, virtually unlimited, aspect ratios.

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Technique for Manufacturing High-Aspect-Ratio Finned Ceramic Caps

A procedure has been developed which uses injection molding to produce finned cap/heatsinks with a high aspect ratio for use in semiconductor modules. A top strap structure is used to support the fins during firing which reduces any warping tendency. In producing finned ceramic caps/heatsinks an aspect ratio of 4:1 has been a limiting factor. The aspect ratio is the fin height 1 (Fig. 1) of the cap 2 relative to the fin width 3 and spacing 4. This limitation occurs because the ceramic powder and binders are forced into a mold using a pressed technique which results in a non-uniform density. When fired, warpage and breakage of the fins may result. The injection molding technique proposed makes it possible to produce caps with high, virtually unlimited, aspect ratios. Injection molding is used to produce a configuration 3 (Fig. 1) with open spaces 4 which will serve as the fin spacing in the final cap. A support 6 (Fig. 2) across the top of the structure provides the means to tie the fins together during the firing cycle. This avoids any distortion of the fins which might otherwise take place. After firing, the tie-bar is removed by conventional machining techniques to obtain the final structure of Fig. 3. In this particular sketch the fin height 1 is seven times that of the fin spacing 4 providing an aspect ratio of 7:1. As noted, there is no special limitation to the ratio which may be achieved wit...