Abstract: In this paper, the improvement of the pass rate of PCB board has been introduced, and the key point is to introduce the latest research progress of short- circuit phenomenon caused by compression depression. By analyzing the defects of the intermediate test, it is found that compression depression is an important factor affecting the intermediate test yield. The main reasons (PP powder, fiber wire, coating agent and other dust and debris) for short-circuit caused by compression depression are further analyzed, and the improvement measures are proposed to reduce the short circuit defect caused by compression depression and to improve the passing rate.