Leadframe-Epoxy Moulding Compound Adhesion: a Micromechanics-driven Investigation

A typical reliability issue of electronic packages is the decohesion between the encapsulant material, the Epoxy Molding Compound (EMC), and the leadframe. As the EMC is a microstructured composite material, the present computational study is aimed at understanding the influence of the EMC microstructure on the macroscopic mechanical and adhesive properties. Statistical Volume Elements (SVEs) are employed to this purpose, with a random arrangement of spherical particles of varying diameter to represent the filler volume fraction and size distribution. Mechanical properties of the neat polymeric matrix are obtained from experimental data relevant to the EMC through an inverse homogenization scheme, and the effect of a varying filler content is investigated. Finally, microstructural effects on the adhesion are studied with micro-scale models of the leadframe-matrix-filler system, accounting for the leadframe-matrix adhesion through a cohesive approach. The effects of filler content, substrate roughness, and intrinsic adhesive properties on the effective traction-separation law are assessed.