One of the biggest challenges facing assembly of SMT interconnects is maintaining lead coplanarity over a distance. The greater the distance, the more likely the PCB surface may display the effects of warp, twist, and thickness tolerances. If the device lead is seated too high above the solder paste, then this will be either a poor solder joint, cold solder joint or worse, an open circuit due to no solder joint. For a gull-winged interconnect, the device leads are visible, making them somewhat accessible for emergency repair, but if the device leads are part of an inline array, and an inaccessible pin location does not have a solder joint. This may make the entire assembly unusable and require external white wiring to physically jump the dead pin location.
There is a technique for screw machine socket receptacles that will allow the shell to achieve vertical travel inside the molded cavity. This is referred to as “Floating Pin” technology. It is an ideal solution for attaching interconnects on uneven surface PCBs.
Floating pins are designed to move in a vertical direction inside counter-bore openings. This interconnect method is ideal in manufacturing situations where the SMT surface is uneven. This technique can be easily applied to pins, receptacles and spring pins. This simple method is a proven solution to assembling on uneven surfaces.
Pictured are examples of inline interconnects (SMT pin base concentric to body) and Gull-Wing termination (leads flank package outline).
Martin Houlroyd is Principal Engineer/Marketing Specialist at Preci-Dip. He has worked in the interconnect industry for 35 years. Email him at firstname.lastname@example.org.