Characterization of a polyurethane as a space approved encapsulant for electronic components

The present investigation has the objective to find and characterize new encapsulants suitable for space applications. The new encapsulants are to replace or upgrade existent materials. A previously employed material, PR 1535, was found to have two major drawbacks. These drawbacks are related to the employment of a restricted-use curing agent and the poor ability of the material to withstand specific mechanical stresses. Past experience has shown that this negative characteristic led to solder joint failure. During the first phase of the investigation, potential encapsulant systems were subjected to a series of mechanical and electrical tests. It was found that the filled Uralane 5753-LV formulations have advantages over the unfilled PR 1535 formulation. The advantages are related to greater flexibility, greater dimensional stability, and nonrestricted use. During the second phase the selected system was further tested and evaluated.