Cavity-down thermal-enhanced package reliability evaluation for low-k dielectric/Cu interconnects IC

It has been well recognized that IC packaging materials have a great impact on the IC chip integrity of chips fabricated by low dielectric constant inter-metal-dielectric (Low-k IMD) materials. To understand the effect of the package process and material in the cavity-down thermal-enhanced BGA package on Low-k IMD chip integrity, packages characterization by both encapsulation process and transfer-mold process was performed. The package samples were built with two different encapsulants and two different molding compounds. The test result showed that encapsulants induced chip corner defects due to the high shrinkage rate and free-body movement of the encapsulant during curing process. The defects led to package early reliability fail with Low-k IMD delamination failure mode. The transfer-mold type cavity-down BGA with low coefficient of thermal expansion (CTE) compound yielded most promising package reliability test results to realize the cavity-down package solution for Low-k chip.