Improved humidity resistance of leaded packages through solder dip process

Humid atmospheres may pose a critical reliability hazard in microelectronic packages, as they are comprised of metals prone to moisture-induced galvanic corrosion. Galvanic corrosion is a global issue that is affecting variety of devices in semiconductor industry. In this paper, we simulated galvanic corrosion via unbiased HAST on flash memory encapsulated in plastic lead frame packages with tin-plated copper leads. We then treated the leads which had corroded during the test with a solder dip and found that failing devices not only can recover but are even able to survive subsequent stress. Throughout the entire reliability stress test, all memory devices demonstrated relatively stable parametric characteristics. Moreover, the normal memory functions of read, erase, and program were perfectly maintained. It is thus proven that solder dip can improve the corrosion resistance of leaded packages and can eliminate defects that are an artifact of the test.