Wire-to-board connectors are used to interconnect printed circuit boards (PCBs) by using connectors attached to wires. Specifications for a wire to board connector include wire-entry angle, wire size, circuits or positions, pitch or center spacing, lock to mating style, and maximum current. There are three wire-entry angle styles: vertical, right-angle, and bottom-entry. Wire size is usually measured in American wire gauge (AWG), a standard for non-ferrous wire conductor sizes. The term "gauge" refers to the wire’s diameter. The higher the gauge number, the smaller the diameter and the thinner the wire. With wire to board connectors, the number of circuits or positions may range from 1 to 120. Pitch or center spacing is measured in millimeters (mm) or inches. There are three basic lock-to-mating styles: positive, friction, and friction ramp. The maximum current or current-carrying capacity is measured in amperes (A) and ranges from 1.0 A to 50. A.
Selecting Wire to Board Connectors
Selecting wire to board connectors requires an understanding of termination methods and PCB mounting styles. Crimp is the physical compression of a contact wire around a conductor to make an electrical and mechanical connection. Insulation displacement connectors (IDC) slice through the cable insulation to make a connection. Choices for termination method also include cage clamp, screw, tabs, and solder cups. With wire to board connectors, there are four choices for PCB mounting: through-hole technology (THT), surface mount technology (SMT), PCB edge, press-fit, and straddle. THT mounts components on a PCB by inserting component leads through holes in the board and then soldering the leads in place on the opposite side of the board. SMT adds components to a PCB by soldering component leads or terminals to the top surface of the board. SMT components have a flat surface that is soldered to a flat pad on the face of the PCB. Typically, the PCB pad is coated with a paste-like formulation of solder and flux. Press-fit and compression-style board to board connectors are also commonly available.
Wire-to-board connectors carry approvals from various national and international organizations. In North America, they often bear marks from Underwriters Laboratories (UL) and/or the Canadian Standards Association (CSA). A wire to board connector for the European marketplace should comply with the Restriction of Hazardous Substances (RoHS) and Waste Electrical and Electronic Equipment (WEEE) directives from the European Union (EU). Wire-to-board connectors that comply with other requirements are also available.