Fabrication of Sn-Bi-Ag Micro-Bumps for High-End Power Chips
Compared with conventional solder balls, Sn-Bi-Ag solder balls feature a lower melting point, better wettability and superior thermal fatigue resistance. With a lower solidification shrinkage rate and enhanced thermal fatigue performance, Sn-Bi-Ag solder balls can effectively reduce the risk of solder joint cracking caused by temperature cycling, making them particularly suitable for application fields with stringent long-term stability requirements such as automotive electronics and aerospace.
A leading domestic chip manufacturer adopted Sn-Bi-Ag as the material for micro-bumps during the R&D of high-performance power chips. The conventional laser ball placement solution delivers extremely low throughput at less than 10 balls per second. In addition, the higher viscosity of molten Sn-Bi-Ag material tends to clog the ball placement nozzles, resulting in ball jamming, ball stacking or material feeding interruption. It also causes deflected jet trajectories, scattered landing positions and solder splashing, which directly undermine the ball placement efficiency, positional accuracy and production yield.
The company adopts Shaoke Laser's micro-bump printing equipment. It uses pulsed laser to induce droplet ejection from metal thin films, completely breaking the bottleneck of traditional ball placement technology, which cannot produce bumps smaller than 50 μm due to solder ball nozzle clogging. Meanwhile, the bumping efficiency is boosted to over 1,000 units per second. Chip samples with tin-bismuth-silver micro-bumps fabricated by Shaoke Laser's micro-bump printing equipment have passed the micro-bump testing for high-end chip packaging at the client's site.
