A Laser Assisted Bonding Process Design with Silver-indium Transient Liquid Phase Method for the Infrared Detectors Hermetic Packaging

Infrared (IR) detection systems were widely used in civilian applications, such as medical diagnosis, remote surveillance and rescue assistance. A good hermetic package protects the active devices from mechanical damage, dust and moisture to ensure the long-term stability and reliability of the IR sensor. More importantly, it would form a good thermal isolation if the active device needs to work at cryogenic environment to maintain its functionality and sensitivity. It has been demonstrated that transient liquid phase (TLP) method can be applied in the hermetic packaging process. However, in the conventional TLP process, the whole packaging structure has to be heated up globally, which may induce a large level of thermal stress due to the coefficient of thermal expansion (CTE) mismatch, adversely affecting the reliability of the components. The global elevated process temperature is also detrimental to the stability of active materials for the thermal sensitive components within the structure.In this current paper, we propose to explore a new hermetic packaging method for the IR detector application, by incorporating the silver-indium (Ag-In) TLP bonding method with a laser-assisted process. In this proposed method, the Ag-In TLP bonding process can be conducted with a highly localized laser heating source, whereby mitigating the thermal impact on the IR active materials and reducing thermal-mechanical stress level simultaneously. The laser heating energy induced temperature contour profile were carefully modelled and analyzed by using finite element analysis (FEA) method. By investigating the laser-assisted bonding (LAB) combined with the Ag-In TLP technology, this research work would provide a new bonding approach in the future development of hermetic packaging for IR detectors.