Paper describes use of organic metal finish deposited onto copper pads to provide protection against oxidation and preserve solderability. Materials Tech
Jim Kenny, B. Wessling, Karl Wengenroth
Joe Abys, John Fudala, Robert Farrell
Enthone, West Haven, CT USA
Summary
The use of an Organic Metal finish only a few nano-meters deposited onto copper pads of printed circuit boards provides effective protection against oxidation and preserves solderability. The Nano layer has a thickness of only 50 nm, and contains the Organic Metal (conductive polymer) and a small amount of silver. Being more then 90% (by volume), Organic Metal is the major component of the deposited layer; Ag is present equivalent to a thickness of 4 nm. This Organic Metal - Ag complex final finish performs as well as any of the established surface finishes with a significant reduction in energy and environmental impact
Conclusions
The Organic Metal based Nanofinish is the first described example of a nanoparticulate complex between an Organic Metal and Ag. Although it does not form a closed nanolayer, it completely and effectively protects the Cu and prevents it from being oxidized even after four lead free reflow steps. Its aging resistance and wetting (soldering) performance is excellent and equal to or better than other well-established metallic finishes. This finish should be considered by anyone currently struggling with the cost and soldering inconsistencies of ENIG or attempting to use OSP on demanding multilayer PCBs
