Customer Challenge
Electronics used in sound amplification devices, such as hearing aids, require ruggedized materials that can withstand exposure to sweat, moisture and chemicals involved in their fabrication. Though copper is an excellent conductor and ideal for use as a grounding stud, its susceptibility to corrosion makes its use problematic in harsh environments. In particular, environments rich in moisture and salts can quickly patina and subsequently oxidize copper metal, compromising not only electrical conductivity but also mechanical strength. Electrically conductive coatings offer solutions for harsh environments as the combination of conductive flake and polymer binder can be tailored to offer ruggedization superior to bare metal. For this customer, the challenge was to find an electrically conductive coating that bonded to copper grounding studs and could withstand exposure to simulated sweat while maintaining sufficient conductivity to act as a grounding path
Key Customer Requirements
- High electrical conductivity
- Withstand exposure to artificial salts, chemical attack and reflow temperatures
- Bonds well to copper metal
Solution
MG Chemicals’ 842ER is a 2-part, electrically conductive, epoxy-based silver coating. The epoxy binder ensures the coating will adhere well to metallic substrates like copper and withstand exposure to harsh chemicals, unlike other polymers such as acrylics or polyurethanes. Further, the silver flake imparts very high electrical conductivity yet its relatively low redox potential ensures it will remain conductive and not oxidize when exposed to salts like simulated sweat. The customer coated copper grounding studs with the 842ER and exposed the chips to multiple conditions, including reflow, acetone soak and IPA soak all followed by a 24-hour cycle of exposure to simulated sweat. After testing, the 842ER coating showed no loss in electrical conductivity or delamination, meaning it could effectively ground excess current without loss of performance due to exposures like sweat, chemicals or reflow conditions.
Conclusion
Substrates like copper are prone to oxidation in humid, corrosive environments rendering them ineffective as electrical conduits for grounding. With sound amplification devices, resistance to sweat is especially important to demonstrate feasibility. Electrically conductive coatings like the 842ER can be used as a topcoat to ensure the sustained electrical performance of grounding studs.
