New-Tech Europe | Oct 2016 | Special Edition For Electronica 2016

Considerations In Selecting The Right Contact For Your Interconnect System

Danny Boesing, Samtec, Inc.

Many articles on interconnects discuss bleeding edge new technologies, new products, or provide guidelines on optimizing system performance. Having said that, standard pitch (2.54, 2.00, or 1.27 mm centerline) board-to-board interconnects are still huge sellers and ubiquitous in the electronics industry. These two-piece connectors are not as sexy as using ultra-high-density interconnects with PAM4 to achieve 56 Gbps serial channels, but they look mighty appealing if your job is to identify and design-in reliable board- to-board interconnect systems. There are several design factors that determine the success of the interconnect system. Two of the most important considerations are selecting the right contact, and selecting the right plating for that contact.

greater yield/tensile strength would be desired, and in other applications a more cost effective option would be appropriate. Brass is generally only recommended for simple, low-cycle applications. While not as conductive as brass, phosphor bronze boasts a higher tensile strength. For the best of both worlds, beryllium copper not only offers the highest strength of the three, but its conduction is close to that of copper, making it well-suited for strong, reliable connections. CONTACT DESIGN BY END- APPLICATION: High reliability, high cycle contacts are usually made of beryllium copper. BeCu provides a strong combination of mechanical and electrical properties for high reliability interconnections. High reliability contact systems frequently have multiple points

Selecting the right contact helps ensure your interconnect system will meet the standards it is supposed to meet – whether it is a high- cycle application, or high shock and vibration, or an interconnect that is going to see very little stress in its life. The following is a basic overview of contact design considerations: CONTACT BASE METAL: Three commonly used contact base metals include phosphor bronze (PhBr), beryllium copper (BeCu), and brass. Brass has a tensile strength of 69 MPa - 434 MPa (Mega Pascal, unit of pressure and tensile strength). Compare this to Phosphor Bronze with 131 MPa - 552 MPa, and BeCu with 965 MPa - 1205 MPa. Obviously, in industrial, high-risk, hostile-environment applications, a

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