The impact of wafer back surface finish on chip strength

A correlation between the wafer back surface roughness and the resistance of the chip to stress-induced failures is discussed. Chip strength was measured using the simply-supported beam method for chips of different backside roughness. Encapsulated samples were subsequently subjected to mechanical impact loading and thermal stresses as in vapor phase flow. The results show that the chip strength bears an inversely proportional relationship with the roughness of the wafer back. Hence, it is important to control the wafer back surface roughness for reliability improvement, especially for surface mount devices