Effects of Extreme Temperature Swings ( $-hbox{55} ^{circ}hbox{C}$ to 250 $^{circ}hbox{C}$) on Silicon Nitride Active Metal Brazing Substrates

摘要

Reliability of power electronic substrates has been one of the main issues of high-temperature packaging technologies. Widely used direct bonded copper (DBC) substrates, if subjected to wide temperature swings, suffer from copper layers peeling off from a ceramic because of the large thermal stresses resulting from the difference in coefficient of thermal expansion (CTE) between the copper and the ceramic (e.g., $hbox{Al}_{2}hbox{O}_{3}$ or AlN). Recently, silicon nitride active metal brazing ( $hbox{Si}_{3}hbox{N}_{4}$-AMB) substrate has been developed with the aim to utilize power electronic substrates for extreme environmental conditions. $hbox{Si}_{3}hbox{N}_{4}$-AMB has superior reliability because of the high mechanical strength of $hbox{Si}_{3}hbox{N}_{4}$. In this paper, the effects of extreme temperature swings ( $-hbox{55} ^{circ}hbox{C}$ to 250 $^{circ}hbox{C}$) on $hbox{Si}_{3}hbox{N}_{4}$-AMB substrates were investigated to evaluate their applicability to harsh environment. Their high resistance to the peeling off of copper layers was confirmed. However, the surface-roughening phenomenon was observed on the surface of copper layers after the temperature cycling test. The mechanism of surface roughening was analyzed. It was found that the out-of-plane displacement of single grains, which is called the orange-peel phenomenon, occurred on the surface of the copper layers.