Technology Research on Automatic Alignment of BGA Ball Mounting Machine Based on Visual Servo

Abstract

Currently, ball grid array (BGA) is the mainstream technology of semiconductor package. The alignment accuracy of BGA ball mounting processing has a great impact on the rate of finished products. In order to reduce the accuracy requirement for mechanism and increase the automation level, visual servo technology is introduced to BGA ball mounting processing in tins paper. Coaxial lighting is adopted to emphasize the characteristics of positioning hole, and parallel processing flow is designed for image capture. Image smoothing and histogram equalization technology are used in image preprocessing to clear up image noise and increase image contrast. Template matching technology is used to identify the positioning hole and calculate the coordinates of positioning hole. And the difference between the coordinates of header and substrate is used as the driving signal to achieve the automatic alignment. Double-closed-loop feedback is adopted in servo system to improve positioning accuracy. And S-shape acceleration curve reduces the impact in the movement. Based on the research on the above technology, an effective scheme for automatic orientation of BGA ball mounting processing is put forward, and it will provide the great support to the development of BGA ball mounting machine.