Chromate Film Used for Chemical Corrosion Control on Gold-Plated PCB connectors,
Abstract
Electrical intermittencies in nuclear submarine navigational computers can result from degradation of gold-coated contacts by insulating films, the latter identified as principally composed of organics and silver sulfide. The films can be removed, but without appropriate measures, they recur. To retard insulating film build-up, a protective, noninsulating chromate surface treatment was developed; it has proven effective in extending service life. Because protection arises from a surface modification, investigation of the chromating process requires the use of surface-sensitive techniques. Analysis by AES, SAM, XPS, EMA and RBS reveals the presence of a thin (< 30 Angstroms) layer, rich in Cr(3+) on top of the gold. This contrasts with much thicker films incorporating Cr(6+) species found in chromate films grown for the protection of Zn, Cd and Al. The absence of Cr(6+) species suggests the chromate film on gold protects via a physical rather than electrochemical mechanism. The chromate film continuity and composition can be adversely affected by mechanical contact, tarnish growth, and substrate microheterogeneity. Copper compounds are implicated in the occasional development of insulating films during field application of the chromate treatment.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1980
- Accession Number
- ADA095645
Entities
People
- E. G. Shafrin
- J. D. Guttenplan
- J. S. Murday
- L. N. Hashimoto
Organizations
- United States Naval Research Laboratory