Investigation on FCBGA package with vertical-aligned carbon fiber thermal pad as thermal interface material

Abstract

Flip chip ball grid array (FCBGA) is the current main packaging form of CPU and GPU. With the miniaturization and intelligence of artificial intelligence chips, chip power consumption of FCBGA continues to increase (the power consumption of H100 has exceeded 800 W) and the heat dissipation problem has become increasingly serious. In the heat dissipation system of the entire chip, the thermal conductivity of thermal interface material (TIM) is a key bottleneck that limits the improvement of FCBGA package heat dissipation capability. Currently commercial TIMs such as X-23 have a thermal conductivity of 3.8–6 W/MK, which is not enough to cope with the high heat dissipation needs of existing FCBGAs. In this article, we introduced oriented carbon fibers into a silicone oil matrix to prepare a thermal pad with a thermal conductivity of 21.0 W/mK, and used it as TIM1 in FCBGA package. By optimization the key process including lid attach, dicing saw and package structure design, coverage rate reached 88.22 % after packaged. Thermal simulation shows that replace TIM in FCBGA from X-23 to homemade thermal pad, junction temperature (Tj) is reduced from 69.9 to 66.8 °C. In addition, reliability test was used carried out on FCBGA packaged incorporating carbon fiber thermal pad as TIM.