Wettability and interfacial reaction between Si₃N₄ and Cu-based alloys

The effect of additions on the wetting characteristics of liquid Cu on a Si3N4 substrate has been studied in parallel with the study of joining of Si3N4 using Cu/80Ni·20Cr/Cu interlayers. The addition of 80Ni·20Cr alloy and Cr reduced the contact angle of liquid Cu on a Si₃N₄ substrate. The contact angle reduction depended upon the Cr content of the sessile drop and anneal time. A multiphase reaction layer developed at the interface between the Cu-rich solidified droplet and Si₃N₄ when Cr or 80Ni·20Cr was added. The failure of Cu/80Ni·20Cr/Cu interlay er bonded Si₃N₄ occurred along the Si₃N₄/interlayer interface. At near the Si₃N₄/interlayer interface, a multiphase reaction layer has also developed. The strengths of bonded Si₃N₄ are strongly affected by the interfacial reaction products.