Adhesion and Reliability Study of Different EMC and Pre-plated Leadframe Surface Combination for Au and Cu Wire Bonded Leadless Package

Abstract

In this study, different molding compounds and pre-plated leadframe surface combinations were characterized in terms of adhesion and its impact on package delamination. Furthermore, Au and Cu wire bonded devices assembled using different EMC and leadframe surface treatment combinations were also assessed to evaluate the quality and reliability performance of these BOM as packaging materials for a DFN package. Key features of the different molding compound materials investigated in this study includes advanced formulation for improved delamination resistance, better fluidity, and copper wire compatibility. Full material characterization was conducted to compare the physical and thermo-mechanical properties of the EMCs. Button shear test on standard and rough pre-plated lead frame surfaces and tab pull test on PPF, Au and Cu substrates were performed to compare the interfacial adhesion performance and typical shear failure modes of various molding compounds. Adhesion data was further supported by subjecting the assembled of DFN package with different BOM combination to Moisture Sensitivity Level 1 (MSLI). Scanning Acoustic Microscopy (SAM) was then used to check the delamination performance on all mold interfaces at zero hour and after MSLI. The delamination level difference between samples built with different EMC types and pre-plated leadframe combinations were summarized in this study. A 23um diameter Au-wire and Cu-wire bonded transistor was used as test vehicle to evaluate the material reliability performance on package level. Moldability check was done to inspect any external voids, incomplete fill, or wire sweep occurrence for all BOM combinations. Reliability performance was assessed by subjecting the assembled units to 1000 cycles Temperature Cycling Test (TCT), 96 hours Highly Accelerated Stress Test (HAST), and 1000 hours High Temperature Reverse Bias (HTRB) at a junction temperature of 150°C. Overall, the material study was able to successfully assess the adhesion, moldability, delamination and reliability performance of different molding compounds and pre-plated leadframe combinations on Au-wire and Cu-wire bonded DFN package.