Ichio Shimizu

Structural design system for thermally enhanced LSI packages

A program practical that enables design engineers to simply design thermal resistance of IC packages has been developed. Template solid models of IC packages and an automatic system for determining heat transfer coefficient are included in the program. The program does not require the design engineers to have a special knowledge of thermal analysis, and it runs on a personal computer with a 200-MHz PowerPC 604 using 13 MB of RAM. It takes only about 10 seconds to calculate thermal resistance of a quad flat package (QFP) mounted on a printed circuit board (PCB). The error between the calculated and measured values was confirmed to be within about /spl plusmn/20% by 144-case investigations. A thermally enhanced QFP with a heat spreader (JEDEC code: MO-204) has been developed using this program.

Thermal design of plastic LSI packages with fins

As a result of recent progress in electronic equipment and devices, the power dissipation of LSI chips has tended to increase. Therefore, it has become more important to improve their heat transfer characteristic. Methods already used to enhance heat transfer in manufactured packages involve adding a heatspreader or using heat radiating lead-frames. In this paper, we propose two kinds of thermally improved packaging designs. One has molded plastic fins on the top of the surface. The other has lead-frame fins that extend from the heat radiation lead-frames. We designed these thermal structures using a previously reported thermal resistance analysis of LSI packages, and then built trial models and measured their thermal resistance by suspending them in a wind tunnel. According to the measurements, the thermal resistance of the package with plastic fins is about 34 percent lower than that of a fin-less package, and the resistance of the package with lead-frame fins is about 20 percent lower than that of a package with only radiation leads.