Radiation Effects in Epoxies Used as Encapsulants for Electronic Packages

Abstract

Scotchcast-type epoxies are among those encapsulants which are being considered for applications in outer space. It is expected that these epoxies will be exposed to a considerable dosage of radiation when flown in space. At LMSC we radiated Scotchcast-type epoxies in a cobalt source and tested the influence of this radiation to the epoxy. A special microtransducer was embedded into the material as a sensor, which allowed monitoring the behavior of the sample under test. It is shown that radiation leads to an after-curing effect, which decays exponentially with time. After a dosage of approximately 10⁶ roentgens, the material is completely cured. Besides these curing effects, a shift of the secondary transition point from +10 to +25°C was experienced. This shift of the secondary transition point from a low temperature into the room-temperature range can lead to difficulties for the circuit designer. The results of the test indicate that electronic components embedded into Scotchcast-type materials are not too greatly affected by changes in the epoxy due to radiation.