Degradation effects of humidity and storage on anhydride cured epoxies

A zinc oxide filled epoxy system was developed for use as a heat sink adhesive for thermally enhancing IC packages. An experimental study showed that the importance of controlling the exposure of the thin films of ZnO/epoxy to humidity is evident. Exposure of the anhydride cured epoxy to ambient humidity in thin films can have disastrous effects on the material´s performance. A 60% RH (relative humidity) exposure for 2-4 h turns thin films of this material into a plastic sheet of unreactive material while the bulk material is relatively unaffected. Fortunately, this material was developed for high-speed, high-volume production. To guarantee that no problems will occur in manufacturing, an exposure of the screened material to a maximum of 1 h to a maximum RH of 60% has been added to the process specifications. In addition, DSC (differential scanning calorimeter) and Shore D criteria have been added to these specifications to further ensure the quality of the product. New parts made and retested with the above specifications showed that the internal thermal resistances did meet the criteria