How Stencil Design and Reflow Profiles Affect Variation in QFN Voiding Data: A Case Study
Authors: Brook Sandy-Smith Company: Indium Corporation Date Published: 5/9/2016
ICSR (Soldering and Reliability)
Abstract: When comparing solder paste material performance, how do we design a test to limit process-related variation to yield a better "apples-to-apples" voiding comparison? Many investigations have been conducted to find materials that offer the lowest voiding in large ground plane solder joints. In addition, there are many process modifications that have been proposed over the last decade to alleviate voiding in BTC components. These include, but are not limited to: pad design, pad patterning, stencil design, via positioning, solid solder addition, and reflow profile optimization.
This study will review several cases where changing the stencil design or reflow profile dialed in the variation of comparative results. The same typical, commercially available test vehicle was used with the provided stencil as well as with modified designs. Due to the nature of the comparison testing, we observed the effects with both high-voiding and low-voiding pastes. In cases where the stencil design balanced the inclusion of venting channels and the optimal solder volume, the lowest variation (and best comparison) was achieved.