Effects of Package Warpage on Head-in-Pillow Defect

Abstract

Head-in-pillow (HiP) is a BGA defect which happens when solder balls and paste can't contact well during reflow soldering. Package warpage was one of the major reasons for HiP formation. In this paper, package warpage was measured and simulated. It was found that the package warpage was sensitive to the thickness of inside chips. A FEM method considering viscoelastic property of mold compound was introduced to simulate package warpage. The CTE mismatch was found contributes to more than 90% of the package warpage value when reflowing at the peak temperature. A method was introduced to measure the warpage threshold, which is the smallest warpage value that may lead to HiP. The results in different atmospheres showed that the warpage threshold was 50 µm larger in N 2 than that in air, suggesting that under N 2 atmosphere the process window for HiP defects was larger than that under air, which agreed with the experiments.

Predicting contact-without-connection defects on printed circuit boards employing ball grid array package types: a data analytics case study in the smart manufacturing environment

“…The second type of articles considered was those discussing BGA defects in any manner whatsoever. Of the 20 articles in this group, eight focused on x-ray or other optical technology to detect existing defects [12][13][14][15][16][17][18][19], four explored the metallurgical properties of the solder [6,10,20,21], three involved somewhat specific subsets of the BGA package type [22][23][24], three involved rework of BGA defects [4,5,25], and two focused on the stencil-printing process [8,26].…”

“…Industry practitioners have explored the various potential contributing factors for BGA defects such as package warpage [5,6], PCB and stencil printing parameters [7,8], and solder paste or solder alloy composition [6,9,10].…”

Investigation of Impacts on Printed Circuit Board Laminated Composites Caused by Surface Finish Application

“…It helps to avoid connection failure following re-design of a product. Moreover, in the case of a relatively larger component with more soldered connections (e.g., ball grid array) that undergoes warpage itself due to the fact of CTE mismatch of the component, mechanically weak solder joints (called head-in-pillow) may occur [ 15 ]. Tearing off of the soldering pad from the substrate may appear during soldering while the joint has already solidified and warping of the assembly is still ongoing or at field conditions when CTE differences in the substrate and mounted components raise the stress concentration [ 16 , 17 ].…”