The paper presents the results of studies on the microstructure, chemical composition and mechanical properties of the Ni/SnAuCu/Ni interconnections obtained due to the conventional soldering at 300 °C for different times and subsequent aging at 150 °C. The EDX microanalysis allowed to detect at the Ni/solder interface the (Ni,Cu,Au)3Sn4 phase which transformed to (Cu,Ni,Au)6Sn5 after longer time of soldering. In the central part of the interconnection AuSn4 brittle phase was present. This phase was responsible for the significant decrease of the shear strength in the joints subjected to aging at 150 °C for 1000h, 1500 hours. The fracture behavior of such joints appeared to be caused partly by the coalescence of the microvoids in the bulk solder, cleavage of η-phase grains and decohesion at the interface.