Preparation and Characterization of High Thermal Conductivity and Low CTE Polyimide Composite Reinforced with Diamond Nanoparticles/SiC Whiskers for 3D IC Interposer RDL Dielectric

Low thermal conductivity and large coefficient of thermal expansion (CTE) are the most serious disadvantages of the polymer dielectric for the interposer redistribution layer (RDL). In this paper, a high thermal conductivity and low CTE composite with polyimide (PI) matrix and diamond nanoparticles/SiC whiskers reinforcement is proposed. The preparation and characterization of the composite film are presented and the effects of the composite on the improvement of the interposer properties are investigated. With 10 wt% diamond-nanoparticles and 7 wt% SiC-whiskers, the composite film has a thermal conductivity of 1.63 W/mK and a CTE of 16.7 ppm/degrees C (compared with 0.19 W/mK and 55.6 ppm/degrees C of the PI). Interposers with PI RDL dielectric and the composite RDL dielectric are fabricated, respectively. The simulation result shows that the composite dielectric can significantly enhance the properties of the interposer compared with the PI dielectric. The thermal resistance of the interposer decreases from 8.04 degrees C/W to 1.15 degrees C/W. The maximum von Mises stress decreases from 72.8 MPa to 16.9 MPa and the warpage decreases from 1.13 m to 0.15 m. Thermal distribution tests are performed as well. The results show that the maximum temperature of the interposer decreases from 64 degrees C to 45.1 degrees C. The composite developed in this study can reduce the temperature and enhance the reliability of the chips with interposers. It has the potential to expand the application of the interposers in high thermal density integration and high reliability devices.