PBGA SUSCEPTIBILITY TO IR REFLOW-INDUCED DAMAGE AS A FUNCTION OF MOISTURE CONTENT

摘要

In an effort to determine a corporate Plastic Ball Grid Array (PBGA) factory floor life specification, a study has been performed to evaluate the sensitivity of 27 - 35 mm package sizes to IR reflow assembly processing. The study was designed to determine a common floorlife specification for 27 - 35 mm PBGA packages of various pin count and construction. Test samples were either pre-conditioned with a 24 hour bake cycle at 125℃ (OOB) or removed from dry pack (OOD) and placed directly into a moisture absorption chamber. Devices were pulled from the testing chamber at varying moisture contents. Some samples were run through three passes of standard IR reflow; some were run through non-standard IR profiles, i.e., worst case peak temperatures and dwell times. Non-destructive evaluation - scanning acoustic microscopy - was utilized to observe popcorn delamination failures.rnThe results of this study indicated that the definition of each moisture weight gain curve is dependent on the material property set and construction of the PBGA device under consideration. At peak IR temperatures of 215℃ to 220℃, popcorn delamination failures were detected in some OOD devices at 96 hours and some OOB devices at 120 hr. of 30℃/70% relative humidity (RH) exposure. Under non-standard reflow conditions, it was found that both peak IR temperature and moisture content can independently affect the integrity of the PBGA device, though the severity of the damage is increased when these parameters are combined.