Principal Component Analysis-based compensation for measurement errors due to mechanical misalignments in PCB testing

Abstract

Capacitive Leadframe Testing is capable of detecting open solder defects in Printed Circuit Boards (PCB). Principal Component Analysis (PCA)-based approach has been shown to be effective in identifying outlier devices using Capacitive Leadframe Testing measurements. In practice, when a sense plate orientation is shifted or tilted, the resulting measurement variation makes detecting outliers harder. Approaches are introduced to compensate for the ‘abnormal’ measurements due to sense-plate variations. A PCA based technique is developed to estimate the relative amount of tilt and shift in sense plates. Such estimates can be used to compensate for mechanical misalignments. It can also isolate the misalignment related information from the defect related information in the data. The effectiveness of this technique in the presence of the two common forms of mechanical variations is illustrated using experimental measurements from a laboratory setting. The approach is not sensitive to the order of pins, and as such, shows promise for detection of complex but systematic errors introduced by sense plate misalignments.