Abstract:
Reliability evaluation of 8 types of commercial operational amplifiers encapsulated in SOIC-8 style plastic packages for space applications revealed multiple humidity-related failures in one of the part types. Two lots of this part type had 90% and 100% failures after highly accelerated stress testing (HAST) performed at 130 oC and 85% RH. To estimate the acceleration factors for these failures, the parts were subjected to monitored HAST testing at 85% RH and three temperatures (110 oC, 130 oC, and 150 oC) for up to 800 hours. Two groups of the parts were tested at each temperature: one group was tested under bias conditions and another at unbiased conditions, followed by bias testing at room temperature and relative humidity of ~ 50%. A failure analysis indicated that the failures were due to corrosion of the silicon/chrome thin film resistors under the silicon nitride/oxide passivation layer. The parametric degradation and failures were observed only at bias conditions, both during biased HAST and during room temperature bias testing after unbiased HAST. Analysis indicates that moisture diffusion through the passivation layer is the limiting factor of the degradation process. In this presentation the mechanism and acceleration factors of failures are reported. The risk of application of the parts for space projects is discussed. It is suggested to use a combination of unbiased HAST with RT bias testing as an alternative to biased HAST for QA of parts intended for space applications especially if it cannot be confirmed via the traveler (especially applicable to COTS parts) that the manufacturer has performed a passivation integrity test at the wafer level.
Related Project(s):
EPAC (Electronic Packaging)
Related Area(s) of Emphasis:
Newly Available Technologies and COTS
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