SMTA International Conference Proceedings

The Effect of Thermal Pad Patterning on QFN Voiding

Authors: Derrick Herron, Yan Liu, Ph.D., and Ning-Cheng Lee, Ph.D.
Company: Indium Corporation
Date Published: 10/14/2012   Conference: SMTA International

Abstract: Voiding under QFNs is a major challenge in the electronics industry. However, voiding can be suppressed by improving venting accessability on the thermal pad by using solder mask dividing strips. Venting accessability is defined as the perimeter length per unit area of the metal pad. Regardless of the shape and the number of subpads, increasing venting accessability results in a decrease in the total number of voids, the largest voids, and discontinuity. Voiding caused by peripheral vias is comparable to voids caused by hidden vias. Voiding increases with decreasing print coverage and is attributed to insufficient solder. Voiding also decreases with an increase in the number of thermal vias. This phenomenon is attributed to volatiles bleeding through the small voids around the thermal via.

Key Words: 

Solder joint, soldering, solder paste, lead-free, SMT, QFN, reflow, void, voiding, venting accessibility, thermal pad

Members download articles for free:

Not a member yet?

What else do you get when you join SMTA? Read about all of the benefits that go along with membership.

Notice: Sharing of articles is restricted to just your immediate work group. Downloaded papers should not be stored on an external network or shared on the internet.


SMTA Headquarters
6600 City West Parkway, Suite 300
Eden Prairie, MN 55344 USA

Phone +1 952.920.7682
Fax +1 952.926.1819