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coefficient. Of course, it is also possible to change the material that the surrounding assembly is made from (case, PCB, etc.) so that it can expand with the connector at elevated temperatures. The chosen connector footprint also has a large effect when operating at high temperatures. For example, a large connector fixed to multiple points across a PCB will generate more stress than a smaller connec- tor as it expands. One real-world example that Omnetics faced was when a customer needed to solve “ Thermal expansion is one of the first headaches that engineers need to overcome
creep, and crystalline structures shift in ways that degrade long-term reliability. Add thermal expansion into the mix, and tolerances that seemed safe on paper can turn into mismatches that prevent reliable mating. Expansion can also induce serious mechanical failures, placing unwant- ed stress on the PCB or enclosure, especially where different materials expand at different rates. Thermal soak and requalification tests for crimped contacts exist because assumptions about stability rarely survive a prolonged heat cycle.
films on conductive surfaces that further degrade electrical perfor- mance. This ties into the final, and perhaps, most insidious issue: der- ating. As connectors heat up, resis- tance increases, reducing their safe current-carrying capacity. In short, high heat erodes both mechanical and electrical performance, forcing engineers to confront trade-offs that don’t exist at room temperature. Design considerations Connectors should be rated for the highest expected operating tem- perature, plus a margin for safety, but in mission-critical applications, that’s the bare minimum. Engineers need to make deliberate design choices to ensure the connector re- mains mechanically and electrically reliable when the environment is actively hostile, all while considering the many physical and electrical impacts that changing temperatures have on materials and equipment. Thermal expansion is one of the first headaches that engineers need to overcome, as they need to choose connectors that expand at the same rate (or as close as possible) to the PCB, or select a connector that has a low thermal expansion
Multiple miniature connector types mounted on a printed circuit board. Connector footprint size, mounting style, and contact density all influ- ence how thermal expansion forces are transferred to the PCB during high-temperature operation. Careful connector selection and placement help reduce mechanical stress during thermal cycling. Then there’s the less obvious solde- rability problem. A connector built to withstand extreme temperatures may do so with materials like stain - less steel, which don’t readily accept solder. Even if the surface is tech- nically solderable, the connector’s bulk thermal mass can act as a heat sink, making it nearly impossible to raise the joint to reflow temperature with conventional tools. Hobbyists will work around this with external heat sinks and brute force, but for those who are designing for mis- sion-critical applications, brazing territory is outside the realm of stan- dard electronics assembly practices. Oxidation also accelerates at elevat- ed temperatures, creating resistive
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