Abstract: Failures of ceramic ball grid array(CBGA) devices are attributed to the thermal expansion mismatch between ceramic and printed circuit board,so the reliability of CBGA has been paid more attention to the problem at all times.The effects of thermal cycling on shear strength and microstructures of soldered joints of CBGA package were studied under the condition of thermal cycling between-55℃ and 125℃.The results indicate that with the increase of thermal cycling times,the shear strengths of the soldered joints of CBGA package decreased and the cracks in soldered joints of CBGA package emerged at the borderline all around the soldered ball and expanded along the grain boundary and led to failure of the CBGA devices.The results are also made clear that the evolving mechanism of the microstructures of the soldered joints of CBGA package subjected to thermal cycling resulted from that the grain grew up,the microstructures became coarse and the thickness of intermetallic compounds increased with the increase of thermal cycling times.