Copper trace cracking under die perimeter of BGA packages: a combined effect of mold and die attach materials

This research examines the combined effect of mold and epoxy die attach materials on the cracking formation of fine copper traces routed under the die perimeters of plastic BGA packages, under different thermal ramping rates. A designed plastic BGA package with specific traces routed and coupled with the active silicon device procured is used. The objective is accomplished by the use of the methods of finite elemental analysis coupled with the design of experiment. For the JEDEC's MRT L4 and TC Condition B reliability stressing, it is found that a lower CTE and a lower dynamic tensile modulus combination of both mold and die attach materials tends to reduce the occurrence of trace cracking, while the effect of thermal ramping rate is found to be insignificant until 1000 cycles of TC is exceeded. Furthermore, a detailed failure analysis is performed on the stressed parts through continuity testing, mold decapsulation, high magnification X-ray, CSAM, SEM, and parallel polishing to confirm the modeling results and experimental findings.