Effects of Extreme Temperature Swings ( <tex-math notation="TeX">-55\ ∘C</tex-math> to 250 <tex-math notation="TeX">∘C</tex-math>) on Silicon Nitride Active Metal Brazing Substrates

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., Al2O3or AlN). Recently, silicon nitride active metal brazing (Si3N4-AMB) substrate has been developed with the aim to utilize power electronic substrates for extreme environmental conditions. Si3N4-AMB has superior reliability because of the high mechanical strength of Si3N4. In this paper, the effects of extreme temperature swings (-55 °C to 250 °C) on Si3N4-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.