Root Cause Analysis of Wrong Component Defect in Surface Mount Technology (SMT) Assembly Process

Abstract

Wrong Component defects are one of the critical issues in Surface Mount Technology (SMT) production, assembly can significantly affect product quality and production yield. This study analyzes a wrong component at location C49 using Root Cause Analysis (RCA) with Fishbone Diagram and 5-Why Analysis. Based on production data, 11 defective units were identified out of 192 units, resulting in a yield of 95%. The investigation revealed that the defect was caused by abnormal pickup or release behavior during the pick and place process, leading to component carry-over, while improper classification during AOI inspection allowed the defect to escape detection. To address these issues, the Intelligent Pickup Sensor (IPS) was activated, and an AOI caution point was recommended to strengthen inspection verification. Following implementation, monitoring was conducted for two months across eight production orders with a total output of 2,340 boards. During the monitoring period, no wrong component defects were observed in the final product output. In addition, IPS recorded 13 pickup error events out of 10,773 component usage transactions (0.12%). These results demonstrate that IPS improves early detection capability and effectively prevents defect recurrence in SMT production.