Degradation of Molding Compound and Wire Bonds in PEMs
File Name: Effect of Environments on Degradation of MC and WB. NEPP.pdf | Date Submitted: 02/01/08
Description:
Effect of Environments on Degradation of Molding Compound and Wire Bonds in PEMs
Abstract:
Degradation of wire bonds (WBs) is one of the major factors limiting reliability of plastic encapsulated microcircuits (PEMs) at high temperatures. Use of PEMs in military and aerospace applications requires extended and thorough evaluation of encapsulating materials and reliability of packages in harsh environments. However, the effect of environmental conditions on characteristics of molding compounds (MCs) and reliability of wire bonds has not been studied sufficiently to date.
In this work, two types of PEMs in QFP-style packages have been stored in different environments at temperatures from 130 oC to 225 oC for up to 4,500 hours in some cases. To assess the effect of oxygen, the parts were aged at 198 oC in air and vacuum chambers. The effect of humidity was evaluated during long-term highly accelerated temperature and humidity stress testing (HAST) at temperatures of 130 oC and 150 oC.
Thermo-mechanical and thermo-gravimetrical analyses were used to evaluate the effect of environment on characteristics of molding compound. Contact resistances of wire bonds and their mechanical strength were used to monitor degradation of wire bonds throughout the testing. Correlation between degradation of MC and WB failures has been analyzed. The effect of environmental conditions on accelerating factors of WB failures has been assessed, and the mechanism of wire bond degradation due to the presence of moisture and oxygen is discussed.
Related Project(s):
Related Area(s) of Emphasis:
High Density Packaging Technologies
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