Thermotropic liquid crystalline polyimides toward high heat conducting materials for 3D chip stack

Abstract

Novel thermotropic liquid crystalline semi-aliphatic polyimide containing polysiloxane unit has been developed. The polyimide film exhibits high thermal stability and liquid crystallinity with lower transition temperature. Poly(amic acid) solution used as a precursor of the polyimide has very good surface wetting properties for a silicon wafer, resulting in homogeneous polyimide thin film formation on the wafer after thermal imidization below 200 °C. The silicon wafer coated with the polyimide thin film can be bonded to another silicon wafer, or to another polyimide film on heating at 270 °C with relatively low pressure. Moreover the bonding is repairable on heating again. It is proposed that the polyimide can be utilized as a polymer adhesive for three dimensional chip stack.