Cu-Sn based joint material having IMC forming control capabilities

This paper describes development of joint materials using only base metals (Cu and Sn) for power semiconductor assembly. The optimum composition at this moment is Cu8wt%Sn92wt% (8Cu92Sn hereafter) particles: pure Cu (100Cu hereafter) particles = 20:80 (wt% ratio), which indicates good stability under Thermal Cycling Test (TCT, -55°C~+200°C, 20cycles). The composition indicated to be effective to eliminate voids and chip cracks. As an initial choice of joint material using TLPS (Transient Liquid Phase Sintering), we considered SAC305 might have good role as TLPS trigger. But, actual TCT results indicated that existence of Ag must have negative effect to eliminate voids from the joint region. Tentative behavior model using 8Cu92Sn and 100Cu joint material is proposed. Optimized composition indicated shear force 40MPa at 300°C. Re-melting point of the composition is 409°C after TLPS when there is additional Cu supply from substrate and terminal of mounted die.