Diffusion at Cu/Sn interface during sintering process

Abstract

Thermal analysis and metallographic studies were used to describe two aspects of the sintering process of Cu–Sn alloys: (a) the microstructural changes at the Cu/Sn interface and (b) the direction of the diffusion between the elements. Cylindrical couples of copper and tin were used (4.5 × 10⁻³ m in diameter). The couples were sintered in a 20H₂–80N₂ atmosphere at temperatures of 573, 723, 923, 1058 and 1073 K and periods of time ranging from 1·2 to 7·2 ks. The heat treated couples were metallographically evaluated with electronic and optical microscopy. Differential thermal analysis (DTA) was carried out under the same experimental conditions to explain the diffusion process during the particle bonding. The results show that different reactions and phases formed during the thermal process, also, it was observed that the diffusion of copper into melted tin predominates during heating, and that the melted tin (T>505 K) reacts with copper to form a new solid phase. A diffusion mechanism for mixtures of Cu–XSn powders is proposed.