Correlation Study of Mobile DRAM Warpage

POP (Package on Package) technology can integrate logic and memory chip in the same package, becoming a choice to deal with the trend of thinning the volume of semiconductor packages, and the ultra-thinning trends increased the control difficulty of warpage. In the SMT (Surface Mount Technology) reflow process, the excessive high temperature warpage would lead to the coplanarity mismatch of top and bottom package components, namely, the gap between the two components was too large, resulting in the occur of non-wet open. In response to the package high temperature warpage problem, the effects of EMC (Epoxy Molding Compound) thickness, EMC warm up time (Aging Time), and high temperature stress creep of material (Mold Demolding Stress and Test Socket Stress) on high temperature warpage were analyzed in this paper. The results showed that the increase of EMC thickness and EMC aging time would both make the warpage more warped towards the ball surface at high temperature. When mold was demolding, the warpage under the high temperature warped towards the EMC surface because the PCB was affected by the reverse tension; test socket latch and adapter applied pressure and support force to the package, and different stress states could cause changes in the high temperature warpage. At the same time, it was found that there was a correlation between normal temperature warpage and high temperature warpage, namely, normal temperature warpage changes would induce changes in high temperature warpage, therefore, high temperature warpage changes could be controlled by normal temperature warpage prediction analysis.