The morphology and growth behavior of interfacial intermetallic compound (IMC) layer for the Sn3.0Ag0.5Cu0.05Cr (SACCr)/Cu joints after isothermal aging at 150 °C for 0, 168, 500 and 1000 h were investigated, and they were compared with Sn3.0Ag0.5Cu (SAC). The results show that the trace Cr dispersed or dissolved in SAC solder effectively inhibits the IMC layer growth at the interface of SACCr/Cu joints. The longer the aging time, the more obvious the inhibiting effect of Cr on the overgrowth of IMC layer of solder/Cu joints. The average thickness of IMC layer of SACCr/Cu solder joints is about 5.13 μm after aging for 1000 h, only 45% of that of the SAC/Cu solder joints.