SMTA International Conference Proceedings


SILVER AND SULFUR: CASE STUDIES, PHYSICS, AND POSSIBLE SOLUTIONS

Authors: Craig Hillman, Joelle Arnold, Seth Binfield, and Jeremy Seppi
Company: DfR Solutions
Date Published: 10/11/2007   Conference: SMTA International


Abstract: The reaction of silver platings to atmospheric sulfur has been documented for several decades, but the fundamentals as to its initiation are still poorly understood. This is aggravated by the general inconsistency observed when exposing silver platings to accelerated test conditions and the relatively long incubation period before issues are observed (12 to 48 months). Speculation has also been presented as to the influence of various potting materials and their ability to 'absorb' sulfur-containing gases. This talk will provide an overview of known silver sulfide corrosion failures, with examples for component (resistor), substrate, and printed board. The fundamentals of these case studies will provide a path for a discussion on the physics of this phenomenon, including how sulfur reacts with silver, how this reaction is influenced by humidity, temperature and other reactive gases, how classic corrosion behavior may accelerate this reaction, and how sulfur-containing gases may migrate through and be retained by polymeric materials. Only after an understanding of the observed field failure behavior and a comparison to the known science can possible corrective actions be reasonably identified and implemented.

Key words: Silver, sulfur, immersion silver, corrosion, sulfidation, Ag2S, silver sulfide, mixed flowing gas, flowers of sulfur, hydrogen sulfide, H2S, printed circuit boards, solderability platings



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.


Back


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

Phone +1 952.920.7682
Fax +1 952.926.1819