The laser ultrasonic method is highly applicable to in-process and in-line measurement as a technology that enables non-contact ultrasonic detection. Previous studies have reported measurements using laser ultrasonic for various applications, however, most were measurements using fixed systems. There is a need for a dynamic UT system in which the laser ultrasonic measurement system itself can move. Therefore, we made it possible to mount the laser system on a robot arm by using a compact microchip laser as the ultrasonic generation source. We measured the artificial back surface slit and verified its detectability performance as a dynamic robot UT system.

View full abstract

 The utilization of transient liquid phase bonding has rendered numerous intermetallic compounds (IMCs) employed as die-attach joints in wide band gap power modules. However, the distinct thermo-mechanical behavior of these IMC joints under thermal cycling conditions has not been investigated. In this study, a comparative study of the thermo-mechanical behavior of six categories IMC joints: Ni₃Sn₄, Ag₃Sn, Cu₆Sn₅, Cu₃Sn, Ag₉In₄, and Ag₃In under thermal cycling conditions were studied through finite element modelling analysis. The thermal stress that induced in IMC joint, and thermal stress/accumulated plastic strain in SiC/direct bonding copper (DBC) were specifically investigated. The results revealed a clear hierarchy among these IMCs concerning their suitability for die attachment when considering thermal cycling conditions. Notably, the Ag₃Sn joint emerged as the most promising choice due to the lowest induced thermal stress within the IMC layer and less damage on SiC/DBC. Conversely, Ni₃Sn₄ exhibits the least favorable thermos-mechanical behavior among the IMCs.

View full abstract