Interconnection method based on solder-filled nanoporous copper as interlayer for high-temperature applications

Abstract

In this study, the nanoporous copper (NPC) sheets were fabricated by dealloying Cu40Al60 precursor alloy in 1.45 mol/L dilute hydrochloric acid solution under water bath at 80 °C for 12 h. The NPC sheets had a typical homogeneous ligament-pore microstructure with the average pore size of 320 nm. The NPC sheet was sandwiched between two Cu substrates with Sn3.0Ag0.5Cu (SAC305) solder paste. The melted solder infiltrated the NPC sheets and reacted with the Cu ligaments rapidly. A Cu/Cu-Sn IMCs/Cu interconnection can be achieved after reflow at 240 °C for 10 min under a pressure of 5 MPa. The average shear strength of the bondlines was 37.68 MPa, and the maximum shear strength can reach up to 57.38 MPa. The average resistivity of the bondlines was measured to be 13.38 μΩ·cm. At last, the evolution of microstructure, Vickers hardness and shear strength of the bondlines during aging test at 200 °C for 15 days were characterized. The bondline can be fabricated at a low temperature but can service at a much higher temperature with a high re-melting point, which can provide a new die attach method for high temperature power device packaging.