Pick-and-Release: A Novel Contactless Bonding Method for Die Attachment

The rapid advancement of semiconductor technology has driven the use of thinner chips to reduce package thickness. However, as chips become thinner, they also become more fragile and susceptible to cracking. To address this packaging challenge, we propose a novel air drop technique for chip attachment that minimizes mechanical stresses during die placement. The 'pick-and-release' method eliminates the direct application of pressure during die mounting and ensures minimal stress throughout the entire die attach process. $1 \text{mm}^{2}$ dies with silver, copper, and gold finishes were bonded using lead-free solder, and both pressure-based and pressure-less attachment methods were evaluated. Bond quality was assessed through bond line thickness, die tilt, void detection, die shear strength, failure analysis, and electrical characterization, providing a comprehensive understanding of the effects of the attachment methods and surface finishes on chip assembly. Our investigation shows that, for the used bonding material, the mounting pressure has no significant influence on bond quality. However, some current limitations of the pick-and-release method were detected and need to be addressed before suggesting its suitability for a specific applications.