35th International Symposium for Testing and Failure Analysis(ISTFA 2009), San Jose, CA, November 15-19, 2009

Conductive Filament Formation in Printed Circuit Boards – Effects of Reflow Conditions and Flame Retardants

Bhanu Sood
Michael Pecht

Center for Advanced Life Cycle Engineering (CALCE)
University of Maryland
College Park, MD 20742, USA


Failures in printed circuit boards account for a significant percentage of field returns in electronic products and systems. Conductive filament formation is an electrochemical process that requires the transport of a metal through or across a nonmetallic medium under the influence of an applied electric field. With the advent of lead-free initiatives, boards are being exposed to higher temperatures during lead-free solder processing. This can weaken the glass-fiber bonding, thus enhancing conductive filament formation. The effect of the inclusion of halogen-free flame retardants on conductive filament formation in printed circuit boards is also not completely understood. Previous studies, along with analysis and examinations conducted on printed circuit boards with failure sites that were due to conductive filament formation, have shown that the conductive path is typically formed along the delaminated fiber glass and epoxy resin interfaces. This paper is a result of a year-long study on the effects of reflow temperatures, halogen-free flame retardants, glass reinforcement weave style, and conductor spacing on times to failure due to conductive filament formation.

Complete article is available to CALCE Consortium Members.


[Home Page] [Articles Page]
Copyright © 2009 by CALCE and the University of Maryland, All Rights Reserved