Reduced total cost of ownership with copper sintering

Abstract:
For copper sintering to be attractive to the industry and adapted on a large scale, not only the material costs, but also the overall cost of ownership should be low. The sintered interconnect must ensure improved reliability over silver, high thermal conductivity and most importantly compatibility with existing silver sintering equipment. This paper presents a novel microscale copper sinter paste with excellent thermo-mechanical fatigue resistance and details the overall process flow, starting from paste storage up to sintering which are substantially simplified compared to a traditional silver sinter process. Enhanced surface modifications on microscale particles together with the use of innovative organic binder chemistry offers excellent low temperature, low pressure sintering capabilities and an average shear strength of approximately 40MPa across the standard metallizations, namely gold (Au), silver (Ag) and copper (Cu) and the capability to also sinter at temperatures as low as 220 degrees celcius, thereby allowing for a single solution for both die-attach and substrate attach. The material are observed to sustain harsh thermal shock conditions of +175/-65 degrees celcius for die-attach and +125/-40 degrees celsius for substrate attach with zero delaminations after 1500 cycles.