Effects of rheology of compound materials on passivation cracking of micro-structure of IC packages

Thermo-mechanical failures are the root cause of failures in integrated circuits. A major cause for these failures is the different coefficients of thermal expansion (CTE) of package materials. Compound material is necessary when assembling, which has different elastic modulus, poisson ratios and coefficients of temperature expansion under different temperatures. Therefore, the rheology of compound material used here is expected to have a pronounced influence on the local stress distribution in the passivation layer. The finite element simulations and the maximum principal stress theory are applied to investigate this influence, which paves the way for compound materials selection in IC packages.