Rapid sintering by thermo-compression in air using a paste containing bimodal-sized silver-coated copper particles and effects of particle size and surface finish type

To rapidly form a highly thermal-conductive line structure that could be sustained even at high temperatures such as 300 °C, the compression (5 MPa)-assisted sintering of a Ag-finished die on an Ag-finished substrate was performed in air employing a paste containing bimodal-sized Ag-coated Cu (Cu@Ag) particles at a ratio of 6 (1.5 µm):4 (800, 400, and 200 nm). The 200-nm particles among the submicrometer-sized particles provided the most enhanced sinterability on both joint strength and microstructure. Accordingly, the 1.5-µm/200-nm Cu@Ag paste exhibited excellent shear strength surpassing 20 MPa, accompanied with a near full-density structure, even by the short sintering for 3 min. The strength eventually exceeded 45 MPa after 10 min. These results demonstrate the successful development of an effective paste to achieve rapid sintering even in air with low material cost.