Cu(3)Sn joint based on transient liquid phase bonding of Cu@Cu(6)Sn(5) core–shell particles

With the development of high-integration and high-power electronics, the lack of matching chip connecting materials that can withstand high temperatures has been a challenge. In this manuscript, a Cu@Cu(6)Sn(5) core–shell bimetallic particles (approx. 1 μm in diameter) are successfully prepared and introduced as a new solder material for the packaging of power devices to obtain a Cu(3)Sn all-IMC solder joint. The joint consisted mainly of equiaxed Cu(3)Sn grains, and a small portion of columnar Cu(3)Sn grains. In columnar-type growth, Sn is the dominant diffusing species, which comes from the depletion of Sn in Cu(6)Sn(5). The depleted Cu(6)Sn(5) is transformed into columnar Cu(3)Sn. In equiaxed-type growth, Cu is the dominant diffusing species. Cu reacts with Cu(6)Sn(5) to grow a Cu(3)Sn layer. This conclusion was confirmed by the orientation relationship. The equiaxed Cu(3)Sn grain nucleates at the Cu/Cu(3)Sn interface have an orientation relationship with the Cu substrate. Columnar Cu(3)Sn grains at the Cu(6)Sn(5)/Cu(3)Sn interface have an orientation relationship with Cu(6)Sn(5).