A Source of Degradation of Plastic Encapsulated Devices

Abstract

Some chemical degradation effects in plastic encapsulated semiconductor devices are analysed by the use of pressurecooker tests. After summarising the possible sources of chlorine contamination and its degradation effects, our new results are presented indicating that chlorine contamination of semiconductor devices can also be caused by some washing and cleaning operations. Considering the sensitivity of semiconductor devices in plastic package against different chlorinated hydrocarbons, a group of safe cleaning agents is defined and recomended to device users and manufacturers. A CONSIDERABLE ATTENTION HAS BEEN PAID recently to the effects and origins of chlorine contamination of semiconductor devices. Failure analysis with dedicated instruments /EDS, SEM/ have shown the presence of chlorine in several degraded devices. It has been found, that the interconnecting metallization of semiconductor devices /Au-Al and Al-Al systems/ corrodes incomparably faster if chlorine impurities are present in addition to moisture traces. As possible sources of the chloride contamination mostly impurities, originating from the chip technológy and assembly or the encapsulat ing plastic material itself /-and in special cases , at devices built in circuits, the salt envia ronment-/ has been made responsible. 1,2 In this paper we intend to call attention to some physicochemical and chemical conditions which shall be observed in order to avoid chloride contamination during the cleaning, degreasing and plating operations of the plastic encapsulated devices, and also at post solder cleaning of assembled printed circuit boards.