Design and Demonstration of an Ultrasonic-Laser Coupled Microjoining Platform for Electronic Device Packaging

The design, assembly, and operation of the ultrasonic-laser coupled microjoining platform are reported, along with its effectiveness in enhancing metallurgical reactions within solder joints. The platform is primarily intended for applications requiring high-precision, hermetic interconnections in electronic components. For instance, infrared sensor chips, widely used in infrared temperature measurement, medical diagnostics, and remote rescue, benefit from high-precision packaging that maintains thermal stability and mitigates thermal drift. Hermetic sealing further shields these sensors from external temperature and pressure fluctuations, thereby improving measurement accuracy and ensuring long-term stability and reliability. To achieve this, the ultrasonic and laser modules have been integrated into a unified platform for the first time. Positioning and pressure application modules are used to achieve precise modulation of the heat source loading and interconnect pressure. With the silver-indium interlayer, two silicon chips were rapidly and reliably bonded using this platform. Propelled by the unique acoustic cavitation effect of ultrasonic waves that promote metallurgical reactions, the solder joint strength reached 27 MPa, conforming to the MIL-STD-883E standard. Phase analysis of the ultrasonic-laser coupled microjoints showed that, under the same laser power and bonding pressure, the previously residual pure indium phase completely disappeared, the solid solution phase content increased, and the joint strength improved by up to 55%, confirming that the ultrasonic energy accelerated element diffusion and metallurgical reactions within the solder joint.