By Gordon Vinther, Ardent Concepts -- In an economic climate where every spreadsheet dares R&D managers to find new ways to drive costs out of systems, the need for less expensive compression mount connectors is still a formidable challenge. Engineers with massively parallel node and pitch programs have to make intelligent trade-offs between mechanical robustness and electrical performance, often with little or no relevant domain experience or access to vendors who clearly understand their challenges.
Higher signal speeds, more challenging cross-talk and matched impedance requirements, and the ever decreasing footprint for smaller devices and boards can be major concerns in the design of systems with detachable components. The use of traditional pin and socket connectors still requires significant z-axis real estate, and has limitations in both pitch capability and mounting options. “Pogo” style spring probes can be very effective both electrically and mechanically, but the inherent complexity in their design offers little in the way of cost reduction when compared to off-the-shelf connector alternatives. Reducing the number of components in a compression mount connector while retaining its electrical and mechanical integrity are significant challenges for engineers with custom designs and rigorous specifications.
In many cases, the shorter the z-height of the connector requirement, the shorter the list of compelling solutions available. Some low node count or low cycle life applications allow for the use of technologies such as conductive elastomerics or stamped finger connectors. In larger densities, the overall normal force required to make good contact using elastomerics can be an enormous challenge for projects with thinner boards or highly sensitive devices. Stamped finger connectors, while commonly used for large volume detachable applications - such as processor zif sockets - are typically available in a small range of stock styles that are tooled and inventoried. Engineers attempting to make a compression mount connection with a custom device, custom board layout or super low z-height are frequently left searching for acceptable, proven solutions that don’t absorb a lion’s share of the project budget. Add in factors such as tri-temp, outgassing concerns, and CTE compatibility, and the risk factors for success rise considerably.
Developing compression mount solutions with fewer components lends naturally to reducing overall connector costs. Historically, the challenge has been to create a solution which is both electrically AND mechanically viable, while still providing the high degree of connector design integrity necessary to pass extensive environmental testing. A focus on contact technology with fewer moving parts, but enough movement to make a reliable connection, is an important means of achieving the goal of cost reduction in the overall system. Mechanically, fewer moving parts also means more focus on downscaling for density (pitch) and height. Electrically, it means shorter signal paths and higher degrees of electrical invisibility. As for your budget, well, the age-old engineering mantra of “Simple is Better” should help you keep your focus.
Gordon Vinther is an inventor, entrepreneur, and connector design expert. He can be reached at Gordon@ardentconcepts.com
