New soldering alloy without lead for Microelectronics applications: in situ X-ray microtomography at high temperature for reliability testin

Two lead-free substitution alloys have been developed. We would like to see how they perform under real brazing: in particular the integrity of the interface with the substrate (presence of cracks or not) and when and how pores occur in the joint, because these are key points for their potential use for industrial applications. The number and the localization of pores are important since a certain level of pores can help for residual stress relief in the joint, but too many of them can lead to dramatic failure; the thermal expansion coefficient of the solder alloy has been chosen to be very close to that of the most used substrates, but the evolution of the microstructure at high temperature and the formation of intermetallics can be prohibitive for service life. It is thus crucial to carry out in situ X-ray microtomography during heating and cooling/solidification to detect the presence of pores and cracks in the solder joints.