Accelerated thermal cycling (ATC) tests were conducted to investigate an effect of thermal cycle conditions on thermal fatigue life of a chip size package (CSP) lead-free solder joint. A ternary Sn-Ag-Cu alloy was used as a lead-free solder material. For frequency of thermal cycle (1~3 cycles/h) and maximum (388~423 K) and minimum (223~273 K) temperatures investigated, the effects of them on thermal fatigue life of the solder joint were slight. On the contrary, correlation was recognized between temperature amplitude and thermal fatigue life of the solder joint. The thermal fatigue life increased with decreasing temperature amplitude. The relationship obeyed the Coffin-Manson’s type equation.