CHARACTERIZATION STUDY OF STRAIN GENERATED DURING PRESS FIT CONNECTOR INSERTION IN PRINTED CIRCUIT BOARD ASSEMBLY

摘要

The wide use of press fit connector technology has made the assembly process the intersection of fine pitch, high I/O IC packaging, high density interconnect, and PCB materials performance. Press fit is a process where connectors with pins are inserted through the Plated Through Hole (PTH) of a Printed Circuit Board substrate to establish mechanical and electrical contact instead of the traditional soldering process. The clearance between the PTH and the connector pin diameters are intentionally made close to zero so that intimate contact is made between the connector pin and the PTH after insertion. A controlled force is used to push the connector through the PTH. One of the consequences of such a process is damage to adjacent solder joints due to strain generated during the press fit insertion process. Experimental investigation was conducted to characterize the impact of strain generated during connector press fit. Tri-axial rosettes were attached to adjacent solder joints located at 0 mm, 5 mm and 10 mm away from the press fit site. Three PCB assemblies, one for each location were used for the study. The rosettes were placed at 4 corners of adjacent solder joints to capture all the strains. Strain gauge measurements were taken as the connector is pressed. The experimental results revealed that locations closer to the insertion site experienced the highest level of strain and the strain progressively decreased further from the insertion location. Furthermore, advanced x-ray inspection and computer tomography were demonstrated as a technique to evaluate and characterize failure sites.