C-section pins are crescent-shaped and tapered so they expand or contract to contact the circumference of the through-hole. Other compliant designs are the C-section and action pin. The most popular compliant pin design is the “eye of the needle,” which features flexible beams on each side. In addition, the joint’s high local pressure produces a cold weld effect that provides mechanical and electrical integrity. Once inserted, the pin expands and presses against the rigid sides of the hole to form a gastight joint. To combat the problem, suppliers developed compliant pins that are several thousandths of an inch greater than the diameter of the PCB hole but compress during insertion. Originally, the pins were solid with a rectangular cross-section that deformed the through-hole during insertion. Press-fit pins are made of copper alloy, and each pin carries three to 50 amps. The pins’ compliance also provides some beneficial flexibility, including slight movement to compensate for high vibration and thermal cycling environments. Lynch points out that compliant press-fit pins provide a direct contact interconnect without any metal filler or voids in the connection. Also eliminated are all fumes, gases or cleaning fluids needed for soldering that often reduce contact reliability. Press-fit assembly can be easily automated, whereas secondary soldering processes are often done manually and are slow, expensive and lacking in quality control. For starters, solder is now lead-free and must be reflowed at high temperatures, which can damage the connectors and board. Press-fit technology offers many other advantages over pin-through-paste and selective soldering. “By using press-fit instead of solder, manufacturers eliminate thermal stress on the board, heat development on sensitive components, cold solder joints and shorts caused by solder bridging.” Much Better Than Soldering “According to the IEC1709 norm, press-fit connections are at least 10 times more reliable than soldered connections,” claims Glenn Nausley, president of Promess Inc. ![]() Bar code scanning enables complete product traceability. The completed housing is then transferred to an unload location. If the components are compatible, the housing is uploaded to a 420 ServoPress and its ram presses the PCB onto the pins in 1.5 seconds.Īfter assembly, the camera performs pin height inspection to verify accuracy to within 0.003 inch. ![]() If the components are not compatible, a “not OK” message appears on an HMI and the fixture returns the housing to the slide table. Upon cycle initiation, a camera takes a picture of the housing and PCB, and a scanner reads the PCB’s bar code. The PCB is positioned so the connector’s pins are properly aligned with the through-holes. A worker places either housing (with PCB on top) onto a slide table, which transfers the housing to a nesting fixture. Assembly and testing is done in a semiautomatic workstation made by Schmidt Technology Corp.
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