Lead-Free Surface Finish and Low-VOC Conformal Coating (CCAMTF)
Project Number: J-96-EM-008

The purpose of the Lead-free Surface Finish and Low-VOC Conformal Coating JG-PP project was to demonstrate and validate lead-free organic and metallic surface finishes and low-VOC conformal coatings for use on circuit card assemblies. Surface finishes containing tin and lead are applied to circuit cards to prevent oxidation of exposed copper; this helps to ensure a solderable surface when components are added during later stages of processing. Conformal coatings are thin layers of synthetic resins or polymers that are applied to electronic devices for protection against a variety of environmental, mechanical, electrical, and chemical conditions such as humidity and moisture, contamination, stress, mechanical shock, vibration, thermal cycling, and corrosion.

Three lead-free surface finishes were tested:

• Benzimidazole
• Immersion gold/palladium/copper (Au/Pd/Cu)
• Immersion silver (Ag).

Four low-/no-VOC conformal coating options were tested:

• Silicone
• Parylene
• Urethane
• No conformal coating.

Circuit card test vehicles were coated and subjected to various accelerated environmental conditions ranging from vibration to corrosive environments, and then tested for electrical performance, reliability, and conformal coating adhesion. Overall, testing results have been positive. The alternative surface finishes all performed as well as lead and the low-VOC conformal coatings provided environmental protection for circuit boards.

All surface finishes and conformal coatings tested have advantages dependent on individual situations. Application specific testing should be completed and reviewed before making any process modifications.

The intelligent use of environmentally compliant conformal coatings will decrease manufacturing costs, simplify rework, and reduce pollution at the source without degrading circuit card quality or performance. A potential cost avoidance of $3 million per year has been estimated for the four participating defense contractors if an alternative is implemented. Rockwell Collins has implemented immersion silver as a replacement for lead.

This JG-PP project is a partnership with the CCAMTF. JG-PP began working with CCAMTF in 1997 to help facilitate the transition of the CCAMTF efforts into the DoD community.

Testing results have been posted on the CCAMTF Website. This website is a repository of CCAMTF reports, appendices, and articles written by Dr. Ronald L. Iman, Southwest Technology Consultants, and other CCAMTF members covering the results and analyses of CCAMTF testing of low-VOC conformal coatings and lead-free surface finishes.

This site last updated February 28, 2008.