Abstract: Ultrasonic imaging technique was adopted to evaluate the joining quality of a target assembly used in microelectronic technology. Dimension, location and variety of defects were determined by its A-scan and C-scan images. Then the testing results were proved by metallographic analysis. Testing results showed that the ultrasonic imaging technique could be used to evaluate the joint state and interior defects, and it is a good nondestructive testing method for the joining quality evaluation of target assembly.