Virtual Prototyping Approach for Package Delamination Risk Assessment under Simulated High Temperature Exposure using Finite Element Analysis

Abstract

Infineon is currently extending the portfolio of leadless packages platform by developing the next-gen bill of materials (BOM) which are able to withstand longer exposure to high temperatures (e.g. up to 6000 hours at 150 °C) for customer applications demanding very stringent mission profiles (e.g. 10 years of operating life). The molding compounds used to encapsulate the semiconductor devices are a mixture of inorganic fillers (usually silica) and organic resin (usually epoxy-based). The organic components will experience degradation and decomposition when exposed to elevated temperatures for an extended duration, e.g. during High Temperature Storage Life (HTSL) testing. Consequently, the thermomechanical properties (such as CTE, Tg and elastic modulus) of the mold compound will change. This results to a gradual increase in the interfacial stress between the leadframe and the molding compound, eventually leading to delamination. Performing actual HTSL test requires substantial amount of effort and time (up to 8.5 months to complete 6000 hours). Virtual prototyping approach using Finite Element Analysis (FEA) simulation offers an innovative and cost-effective alternative for delamination risk assessment by numerically evaluating the interfacial stresses in a shorter amount of time. Major benefit of this approach is: a significant reduction in engineering resources during pre-selection of materials as candidate for the next-gen BOM. This paper generally describes the observed changes in the thermomechanical properties of three different molding compound types under three different HTSL conditions by discussing the results obtained from material characterizations. The characterization results will later be translated as material inputs for the FEA simulation. The resulting interfacial stresses are then evaluated at the leadframe to different molding compound interfaces under different HTSL conditions.