Connector Reliability Modeling

Project Number: C96-07

Point of Contact: pecht@calce.umd.edu

Objective

Enhance and reinforce the "first cut" physics of failure based connector reliability model. Using data generated by the automated contact resistance probe (ACRP) developed at the CALCE EPRC, contact resistance with respect to environmental exposure, normal force, plating thickness, interface geometry and wipe at low normal forces will be investigated. This data will be used to make the connector reliability model more comprehensive.
 

Background

The reliability of electronic systems is largely dependent on and significantly impacted by the performance of various metal contacts in the system. Electrical contacts and connectors must have low and stable contact resistances during service life. The useful life of a contact ceases when the contact resistance exceeds a certain limit value. Models have been developed by the CALCE EPRC to assess the reliability of contacts subjected to different ambient conditions. These models will be reinforced with additional experimental contact resistance behavior studies to expand their scope. The Automated Contact Resistance Probe has been developed to facilitate these studies.
 

Work Accomplished

• Established test procedures including such variables as maximum normal force, loading rate, and wipe length.
• Calibrated probe to AMP probe and ASTM B539.
• Gathered test data on coupons provided by AMP.
• Investigated contact directly on corroded pore sites on gold plated finishes to determine if any combinations of wipe and geometry can make reliable contact at low loads.
• Analyzed data to determine the significant factors and interactions with respect to contact resistance.
• Incorporated the mixed flowing gas (MFG), coupon geometry, plating thickness, and wipe resistance data into a contact resistance model.
• Test procedures established.
• Probe calibrated to AMP probe.
• Baseline data on clean gold and tin-lead samples has been taken.
• Probe was used to collect data from aged palladium samples as a "shake down" project. Results to be published by AT&T in paper titled "A High Temperature Electrical Contact Finish for Automotive Applications".
• Test matrix finalized.
• Nickel plated samples have been tested and initial data analysis completed.
• Investigated contact resistance both on and off corroded pore sites on gold plated finishes to determine if any combinations of wipe and geometry can make reliable contact at low loads.
• Analyzed data to determine the significant factors and interactions with respect to contact resistance.
• Incorporated the mixed flowing gas (MFG) exposure, coupon geometry, plating thickness, and wipe data into the contact resistance model.
• Enhanced the connector reliability software by incorporating the more comprehensive contact resistance model.
• The available coupons have two geometry types and have variable exposure times to the Battelle Mixed Flowing Gas (MFG 3 gas) as well as 0, 15, 30, and 90min of gold plating. The nickel plated samples (no gold finish) have been tested.
• Results from testing the nickel plated samples have been summarized in The Effects of Wipe on Corroded Nickel Contacts.
• Data reduction has shown that stable electrical contact can be established on thin layers of gold plating provided that contact is not made on a corroded pore. If contact is made on or near a corroded pore, open circuit conditions will result.