STRENGTH OF ELECTRONIC COMPONENTS ENCAPSULATED WITH COMPOUND UNDER THERMAL IMPACTS

Abstract

Electronic packages with complete encapsulation by compound are in the research objective for the represented study. Encapsulation designed to provide reliable protection against all climatic impacts and increases mechanical strength of the package becomes the reason for potentially destructive mechanical stress that appears when packages are subjected to thermal impacts due to internal mechanical interaction between sealed components and sealant caused by difference of their physical and mechanical characteristics. The Lame-Gadolin theory that considers interaction of compound thick-walled cylinders in form of axially symmetric problem has been substantiated for the stress calculations in electronic components represented as the solids of revolution surrounded by the layer of compound and subjected to simultaneous action of pressure and temperature. Statically indeterminate problem was solved with considerations in the material properties and compatibility in deformations in order to define radial, tangential stresses and strain in both electronic components and compound. Calculation formulas for radial and tangential stresses in both electronic component and compound, and the contact pressure at the boundary between two joint cylinders were represented for the case of stabilized temperature drop, which represent the ultimate thermal impact on the encapsulated package. The taken considerations provide stress calculation for sealed components at the arbitrary form of encapsulation, what means irrespective to sealant profile, on only condition that compound thickness is 4 times higher than component’s external radius. Since materials of copmound and compound are in complicated stressed condition their strength assessment is performed by using third strength theory or theory of greatest tangential stresses.