Precoated stainless steel improves tactile domes forming

By Kate Bachman

September 6, 2010

Situation

Tactile domes are used in communication devices as the switch element incorporated into membrane switches and control panels. Generally, they are made of 301 stainless steel preplated with 3 to 7 microns of nickel or silver.

A global electronics stamper with business in the tactile domes segment encountered problems while forming tactile domes of silver and also nickel-plated stainless steel. The problems included yield loss caused by issues with the plating. A poor adhesion between the coating and the base material and a large variation in the coating thickness along and across the strip (dog-bone effect) resulted in flaking and uneven contact performance. Customers perceived these defects as evidence of poor performance.

Resolution

The stamper switched the work material to Sandvik Materials Technology’s Santronic™, which is an alternative technology for coating stainless steel strip with diverse metal layers such as silver and nickel used for stamping electronic components such as tactile domes, contact springs, and EMI shielding.

The material is engineered to have excellent adhesion between the base material and coating to prevent cracking and flaking, as well as excellent fatigue and relaxation resistance, the company said. Its smooth, flat surface created by the optimized coating process is designed to increase electrical contact.

“Using Sandvik Santronic, we were able to increase our yield, lower our production costs, and improve the finished products’ performance for our clients. Because of this, we have strengthened our leadership role in the marketplace and expanded our production capacity,” the stamper’s production manager said.