Destructive and non-destructive evaluation of copper diffusion bonds

The current study reports diffusion bonding phenomena of copper to copper (Cu/Cu). The bonding was conducted in the temperature range varying between 700 °C and 850 °C at varying soaking time (30–120 min) under uniaxial pressure of 5–15 MPa in vacuum atmosphere. The bonded regions were characterised, using light and scanning electron microscopic (SEM) studies. The bonded strength was evaluated through destructive testing using micro tensile and microhardness tests. In addition, the bond quality was also assessed by nondestructive testing (ultrasonic C-scan test) method. The grain growth equation was used to understand the bonding mechanism. The investigational results were compared with the model developed by Pilling, observing void closure by creep flow and diffusion mass transfer. The superior bond strength ratio of 91% was observed at bonding temperature of 750 °C for the applied pressure of 15 MPa of 60 min soaking period. The correlation between destructive and non-destructive tests was studied.