PCB Terminal Blocks

PCB terminal blocks are modular, insulated devices that mount on printed circuit boards (PCBs) and secure two or more wires together. Some have integral pin terminals and mount through holes in the board. Others plug into PCB-mounted pin strips. Screw clamps, spring clamps, insulation displacement, and tab terminals are used to make electrical connections. Pluggable and stackable units are also available. Most PCB terminal blocks are mounted horizontally, vertically, or at a 45° angle. Voltage rating, current rating, and operating temperature are important performance specifications. Additional considerations include number of contacts or pins, contact pitch and conductor size. American wire gauge (AWG), a U.S. standard for non-ferrous wire conductor sizes, is used to indicate wire diameter. The higher the gauge number, the smaller the diameter and the thinner the wire. In North America, organizations such as Underwriters Laboratories (UL) and the Canadian Standards Association (CSA) provide approvals and certifications. PCB terminal blocks that bear the CE Mark and the VDE Mark are also available. 

There are many types of PCB terminal blocks. Single feed-through devices have one input contact and one output contact. They are used in wire-to-wire connections where a wire is fed through one side and out the other. Dual level or two-tier devices have two levels of contacts in order to save space and simplify wiring. Three level or three-tier devices are also available. Bridged PCB terminal blocks connect multiple levels and increase circuit flexibility. Ground circuit terminals are interchangeable with standard blocks and permit the grounding of equipment. Disconnect or switch blocks can be disconnected without removing wires. They usually include a knife switch, sliding link, or removable plug. Fuse blocks or fuse holders are circuit protection devices that contain short circuits and provide visual indications of fuse condition. Thermocouple blocks connect temperature-sensing thermocouples and use reliable metal connections. Input/output (I/O) blocks provide communication between controllers and sensors. Actuator blocks are used with three-wire and four-wire devices such as proximity sensors and photoelectric sensors. Transformer terminal blocks mount on coiled bodies and adapt coil ends to screw or push-on tab connections for power connections. Electronic circuit blocks provide functionality such as rectification and voltage indication. Power distribution blocks are designed specifically for the power distribution industry.

Selecting PCB terminal blocks requires an analysis of termination options. Screw clamps use a screw to tighten the wire against the bar with or without a pressure plate. They are used with fuse holders, electronic component holders, signal conditioning modules, surge protection modules, and many other types of devices. Spring clamps are less popular than screw clamps, but well-suited for top-entry connections and applications that use small wire sizes. The wire is retained in the clamp by the force of a spring that pushes the wire against the connection bar. Insulation displacement connections (IDC) push an insulated wire between two sharp, blade-like pieces of metal so that the conductor touches the connector without exposing bare wire. Tab terminals (spade terminals, blade terminals) are designed to be inserted and removed rapidly because they do not require soldering. Other specialized and proprietary termination options are also available.

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Part Numbers for PCB Terminal Blocks