Using BP network for ultrasonic inspection of flip chip solder joints

Flip-chip technology has been used extensively in microelectronic packaging, where defect inspection for solder joints plays an extremely important role. In this paper, ultrasonic inspection, one of the non-destructive methods, was used for inspection of flip chip solder joints. The image of the flip chip was captured by scanning acoustic microscope and segmented based on the flip chip structure information. Then a back-propagation network was adopted, and the geometric features extracted from the image were fed to the network for classification and recognition. The results demonstrate the high recognition rate and feasibility of the approach. Therefore, this approach has high potentiality for solder joint defect inspection in flip chip packaging.

► The image of flip chip was segmented using the correlation coefficients method.
► The images of solder joints were pre-processed based on its structure information.
► Seven characteristics of every solder joint image were extracted.
► The characteristics were fed to the BP network for classification and recognition.
► The results validate the feasibility of this approach for defect inspection.