Influence of the solder volume and reflow process on solderability of the aluminum solder paste and reliability of Sn-0.3Ag-0.7Cu/6061Al solder joints in packages of LED lighting components and structures

Low-temperature soldering of 6061Al by an aluminum solder paste consisting of a purpose-designed flux and Sn-0.3Ag-0.7Cu (SAC0307) solder alloy powder with different reflow process parameters (such as the heating rate, peak soldering temperature and joint thickness) and the reliability of the soldered joints were investigated in this study. With increasing the heating rate, the spreading performance of the paste on 6061Al increases, and the tensile strength and shear strength of 6061Al/SAC0307/6061Al solder joints increase observably, which is due to the fact that the activity of the aluminum solder paste increases with the increase of heating rate in reflow process. However, the effects of peak soldering temperature on the solderability of the aluminum solder paste and the reliability of the soldered joints may be negligible. There is no intermetallic compound or transition layer formed at the interface. In addition, the shear strength of the joints increases with the increase of joint thickness because of the less voids formed in the solder matrix.