High temperature Au-based solder reliability in electronic packages for harsh environments

摘要

The operation of electronic packages in high temperature environments is a significant challenge for themicroelectronics industry, and poses a challenge to the traditional temperature limit of 125°C for high electronicsystems, such as those used in down-hole, well-logging and aero-engine applications. The present work aimsto develop understanding of how and why attach materials for Si dies degrade/fail under harsh environmentsby investigating high temperature Au based solders. Au-2wt%Si eutectic melts at < 400°C and offers hightemperature stability but high temperature processing and complex manufacturing steps are the major drawbacks.Changes in the die attach material were investigated by isothermal ageing at 350°C, thermal shock and thermalcycling treatments. Die attach reliability investigated by thermal shock and thermal cycling showed that thebonded area degraded. Nevertheless, most of the samples tested had high bonded area ranging from 92.5 to 97.5%.The failure behaviour of the die attach materials included cracking of die and/or attach material, delaminationand voiding. Scanning acoustic microscopy images provided a rapid assessment of delamination and other defectsand their location within the package. Microstructural analysis and die shear testing were also carried out, alongwith the high temperature endurance of a SOI test chip for signal conditioning and processing applications at250°C. All functions evaluated have shown stable performance at 250°C for up to 9000 hours.