2016/05/26 by Keiichiro Iwanabe, Kenichi Nakadozono, Yousuke Senda +1
Engineering · #3D IC and TSV technologies #Acoustics #Advanced MEMS and NEMS Technologies #Composite material #Crystallite #Electronic Packaging and Soldering Technologies #Materials science #Metallurgy #Perpendicular #Softening #Strain gauge #Substrate (aquarium) #Ultrasonic sensor
paper · pdf · doi:10.7567/jjap.55.06gp22
openalex publication_date 2016/05/26 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Abstract The bonding dynamics of a cone-shaped microbump during ultrasonic bonding are investigated by in situ measurements of the strain generated in a substrate using a piezoresistance strain sensor. The strain sensor is composed of a pair of p- and n-type piezoresistance gauges to extract strain components in the ultrasonic vibration along the plane parallel to the substrate surface and along the direction perpendicular to the surface. Flip-chip bonding is performed at room-temperature. The time evolution of the strain generated in the substrate according to the load-up of pressing force and application of ultrasonic vibration is clearly detected. The softening of the bump metal during the application of ultrasonic vibration is clearly observed. Results of a comparative study between the bonding of a cone-shaped microbump and that of a flat-top microbump suggest mechanical stress concentration near the top end of the cone-shaped microbump, which results in the transformation of the crystal texture of the bump from grains to fine crystallites.