Analysis of signal integrity of UBM and bump interconnection

The simulation model of UBM bump interconnect structure was built. Its signal integrity under the high-frequency condition was studied based on HFSS software. The electric field strength distribution of UBM bump interconnect structure was obtained, the impact of UBM thickness and different material combinations on signal integrity of UBM bump interconnect structure was also studied. The results show that the electric field strength distributions on the bump surface and UBM under different frequencies are uneven,the more close to the top of UBM the stronger of the electric field strength is. The return loss of UBM bump interconnect structure increase as the signal frequency increases but the insertion loss decreases with the increase of the frequency. With the increase of the thickness of nickel layer, copper layer and titanium layer, the insertion loss decreases. The signal integrity of Ti-Wu-Au combination is the best, the Ti-Cu-Ni combination is the second and the Cr-Ni-Au combination is the worst.