Evaluation of mechanical quality of field-assisted diffusion bonding by ultrasonic nondestructive method

The mechanical quality of field-assisted diffusion bonding was tested by an ultrasonic nondestructive method and evaluated in terms of interface bonding ratio. Bond interface was examined by ultrasound of frequency 20 MHz and the C-scan image of interface was obtained. The bonding ratio was calculated after the C-scan image was segmented into bonded region and non-bonded region based on an appropriate threshold. To study the relation between bonding ratio and mechanical strength, the ultrasonic testing and shear testing were performed on the specimens of Al to β-Al2O3. The experimental results show that the bonding ratio linearly increases with the increase in the shear strength. It is proved that bonding ratio can be used to evaluate the bonding mechanical quality, as it is an indicator of bonding mechanical strength. Using this method the mechanical quality of bonding between Si and K4 glass was evaluated. The optimum temperature and applied voltage was found to be 400 °C and 700 V to bond Si to K4 glass with bonding ratio of 96.0%.