OPTIMIZATION OF VOIDS IN SOLDER JOINTS AT BOARD-LEVEL BGA ASSEMBLY
Author: Sarathy Rajagopalan Company: Solectron Corporation Date Published: 4/28/1997
Surface Mount International
Abstract: PBGA packages have increased in popularity and now have become commonplace in many board level assembly operations. A concern in industry is the formation of voids in eutectic PBGA solder joints. A Design of Experiment (DOE) was initiated to determine the control parameters of void creation on PBGA assembly. A test vehicle with multiple PBGA packages totaling over 3000 BGA 1/0s was chosen. The two designs came from two different suppliers. One was an overmolded cavity-up design and the other was cavity-down. The solder paste was held constant as it was the approved solder paste of choice in manufacturing. The control parameters chosen for the DOE were the soak and reflow temperature zone settings and the conveyor speed. The results of the 15 DOE runs showed varying degree of voiding. The void responses for the BGA suppliers were drastically different. However when verifying the “sweet spot” regions, all packages resulted in nearly zero voids.