Evaluation of Adhesives for Hybrid Microcircuit Package Sealing

A study was performed to evaluate the suitability of adhesives for sealing hybrid packages for NASA/MSFC applications. This study consisted of three parts. 1) Screening ten selected adhesives on the basis of their ability to seal gold-plated Kovar packages that retain their seal integrity after individual exposures to four increasingly severe temperature-humidity environments. 2) Screening the four best adhesives, as determined from the temperature-humidity screen, on the basis of their ability to seal gold-plated Kovar packages and ceramic packages that retain their seal integrity after both individual and sequential exposure to Class A test environments specified in Method 5004.2 of MIL-STD-883A. 3) Subjecting the best adhesivepackage combination, as identified by the MIL-STD-883A screen, to a 60°C/98% RH environment and continuously monitoring the moisture content using Panametrics Aquamax-type moisture sensors to determine susceptibility to moisture permeation. Results showed that while there are adhesives that can seal packages that retain their seal integrity (i.e., pass the MIL-STD-883A Seal Test) after exposure to temperaturehumidity environments, including 10 days at 85°C/85% RH and all MIL-STD-883A, Class A, test environments, the seals are not hermetic (i.e., moisture permeates through them).