Performance and reliability study of Pd-coated copper wire bonding on ENEPIG substrate

Pd-coated copper wire bonding is getting more practical applications in electronic packaging because of advantages, such as ease of use, better bonding performance and reliability. ENEPIG (Electroless Ni Electroless Pd Immersion Au) is a prevalent surface finish technique that can realize more flexible substrate design, increase wire density and hence achieve device miniaturization. Study had been focused on the evaluation of bonding performance and reliability of Pd-coated copper wire bonding on ENEPIG substrate in this paper. Design of Experiment (DOE) had been performed to investigate effects of bonding parameters such as USG current, friction amplitude, friction frequency and force on shear strength and yield. The optimized parameter set was determined after comparison and analysis. Among four bonding parameters, friction amplitude showed more significant impact on bonding quality. High Temperature Storage (HTS) test had been carried out to inspect reliability of Pd-coated copper wire bonding on ENEPIG substrate. After thermal aging at 175°C for 128 hours, the Cu-Au interface showed excellent bonding performance.