Transient liquid phase (TLP) bonding (or solid-liquid interdiffusion bonding) is capable of producing joints with excellent mechanical and thermal properties, and with operation temperatures at or even above the bonding temperature. Due to its comparatively low bonding temperatures (≤ 300℃) and the high reliability of the resulting joint, the TLP system Ag-Sn is of particular interest, e.g., for die attach of next-generation SiC-based power-electronics modules. However, broad application of TLP bonding technologies requires reduction of the comparatively long processing times necessary to achieve reproducible high-quality TLP joints. This work demonstrates the successful transfer of a furnace-based Ag-Sn TLP bonding process with rather long processing times to a very fast TLP bonding process onto a manual flip-chip bonder. By employing a rapid heating rate of 20 K/s, as offered by the flip-chip bonder, a total process time of less than 4 min at 240℃ could be reached, with an average joint shear strength as high as (58 ± 22) MPa. In addition, application of a short, low-intensity ultrasound (US) pulse at the onset of Sn melting promotes intermetallic Ag3Sn formation and efficiently removes entrapped gas, thereby avoiding large-scale bond defects. This way, a substantially enhanced shear strength of (104 ± 8)℃ could be achieved.
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