Moisture sensitivity characterization of build-up ball grid array substrates

The Joint Electron Device Engineering Council (JEDEC)-developed industry standard, JESD22-A113-B, classifies plastic packaged devices into six levels of moisture sensitivity based on the amount of exposure to moisture they can withstand before becoming susceptible to moisture-induced damage during solder reflow. Plastic ball grid arrays (PBGA) could not meet the JEDEC level 3 requirements for moisture sensitivity at the time of the establishment of the JEDEC standard. This study demonstrates that the substrates of some PBGA's will not meet the JEDEC level 3 requirements. Thus, the substrate may be a limiting factor in PBGA moisture sensitivity ratings. The purpose of this study is to characterize the moisture sensitivity level of various next generation build-up BGA substrates. The occurrence of moisture-induced swelling and thermal-expansion-mismatch effects including delamination and cracking are correlated to the moisture absorbed into the substrates during preconditioning. Visual observations of the degradation are verified by post-reflow scanning acoustic microscopy and environmental scanning electron microscopy inspection.