Package with high thermal conductivity of graphite attached onto die surface to solve hot spot issue

Abstract

Currently electrical products such as smart phone and tablet, light weight and thin feature of them are definitely required. To achieve several requirements, size of IC package assembled in limiting space become more crucial and development orientated. So, a lot of IC design factory prefer to make more function loop in one single die to provide high efficient performance application for electric products such as cell phone chip module and graphic card GPU …etc. While, IC with multi function loop in one single die inevitably cause different power dissipation distribution onto die surface and it might accompanies hot spot issue on die surface. Thereby hot spot issue affect overheat problem to reduce IC products performance characteristic during frequently working. Therefore, try to balance die surface temperature distribution is very important work for IC with multi function design. We want to investigate a methodical to find out good solution to balance die surface temperature distribution. However, to add a metal heat sink onto package surface is normal and traditional technique to spread out heat from package surface, but this way can't effectually balance die surface temperature directly. In this paper, we study a new method that to attach a thin heat spreader onto die surface during assembly process. This new method can reduce hot spot issue and balance die surface temperature directly. From this study, we select EDHS-PBGA (Exposed Dropin Heat Sink BGA) package assembly with thin heat spreader on die surface and use Flotherm CAE tool to simulate die surface with different heat spreader material thermal performance comparison. The heat spreader materials are silicon, copper plate, aluminum plate and graphite plate. The graphite plate material is with well specific characteristic of high thermal conductivity as 1600∼1900w/mk for horizontal direction and 6∼10w/mk for vertical direction. Package with graphite plate spreader onto die surface will perform conspicuous temperature balance distribution due to graphite plate with high thermal conductivity parameter index than other material in horizontal direction. We expect this graphite attached onto die surface technology can be popularly apply on IC package process to solve hot spot issue of IC with multi function design.