A PCB terminal block is a type of electrical connector where a wire is clamped down to metal by a PCB . The wire is sometimes just stripped of electrical insulation at the end, and is bent in a U or J shape to fit around the shaft of the PCB . Alternatively, a lug can be crimped onto the end of the wire to protect it. SetPCB s are also used, as in a luster terminal or lustre terminal, but lugs will not fit into them. For both lugs and bare wire, the PCB is tightened for a secure connection.
Description and usage
PCB terminal blocks are commonly used to connect a chassis ground, such as on a record player or surge protector. Most public address systems in buildings also use them for speakers, and sometimes for other outputs and inputs. They are also used extensively in wiring for electricity, for connecting electrical outlets and switches to the mains, and for connecting major appliances like clothes dryers and ovens to the particular plug installed in a home, or directly hard-wiring to the house, as required by local electrical codes in the US. For reliability reasons, PCB terminal blocks for earth ground connections are preferred on most USA-style outlets, even for those that otherwise have "rear-wire" push-in connections, despite the difficulty of bending heavy-gauge solid copper around a PCB with pliers. Grounding PCB s are often marked green, and when used on consumer electronics often have a washer with gripping "teeth".
Advantages and disadvantages
Terminations to PCB terminal blocks can be made with simple hand tools and do not require a mating connector to be applied to the wire end. The connections are physically and electrically secure because they firmly contact a large section of wire. The connectors are relatively low cost compared with other types of connector and a PCB terminal block can easily be integrated into the design of a building wiring device (socket, switch, or lamp holder).
Disadvantages include the time taken to strip a wire and properly wrap it around the PCB head. This is slower than a plug-in connector, making PCB connections uncommon for portable equipment. If the wire is too small, it can be cut through by an overtightened PCB head. Wire strands may not be contained by the PCB head, so sometimes stranded wires are crimped into a ferrule to prevent bridging of terminals; this partly offsets the economy of a "bare" wire termination. Wires must never be tinned prior to installation in a PCB terminal block, since solder will cold flow resulting in a loose connection and serious fire hazard.
PCB connectors sometimes come loose over time if not done up tightly enough at fitting time. Verifying adequate tightening torque requires calibrated installation tools and proper training. In the UK all PCB connectors on fixed mains installations are required to be accessible for servicing for this reason.