A Laser-Assisted Thermal Gradient Transient Liquid Phase Bonding Process Design for Thermally Sensitive Components in Hermetic Packaging

In this article, we propose a thermal gradient mechanism-based laser-assisted bonding (TG-LAB) process, which can be used for the hermetic package of thermally sensitive components. The traditional transient liquid phase (TLP) method can realize the hermetic package of electronic devices. However, the whole structure needs to be heated during the packaging process, and it needs to be kept at a high temperature for a certain time. This method may adversely affect the activity and stability of the thermally sensitive materials and components in the structure, so it is not perfectly suitable for the hermetic packaging of thermal-sensitive devices. In this article, the thermal gradient TLP bonding of silver-indium (Ag-In) material system can be realized by introducing a laser heat source to achieve local heating and generate a large temperature gradient in the bonding region. In addition, to further stabilize the active components, a thermoelectric cooler (TEC) is integrated at the bottom of the package, which can significantly reduce the temperature in the chip region and has almost no effect on the TLP bonding process. We used multiphysics finite element analysis (FEA) simulation software to model the laser heat source, package, and TEC and explored the effects of laser power, laser spot radius, laser moving speed, and TEC current on the bonding process. Finally, we propose a complete set of hermetic packaging processes, in which the temperature of the chip region can be stabilized below 23 °C while satisfying the requirements of Ag-In thermal gradient TLP bonding. This research provides a new method for thermal management and hermetic package integration for thermally sensitive components in the future.