IDC Receptacle for 18 AWG Wire Harnesses
The TE Connectivity 3-644878-3 is a 3-position MTA-156 IDC receptacle designed for terminating discrete or ribbon cable. The housing is orange, carries a closed end to prevent wire push-through, and includes a polarizing key that aligns with the matching header to prevent mis-mating on the assembly line.
Termination and Retention
Termination is IDC — the wire is pressed into a slotted contact beam that displaces the insulation and grips the conductor. The 80.0µin (2.03µm) tin contact finish provides enough material for the cold-flow displacement during termination and gives corrosion resistance in indoor equipment environments.
Harness Assembly Fit
This 3-position receptacle mates with any standard MTA-156 header of the same circuit count and pitch. The 0.156" (3.96mm) pitch is the defining dimension for the board footprint — the header pins are on that spacing, so the harness plugs into a matching footprint on the PCB. The closed end means the receptacle accepts wire only from the open side, which prevents a wire from being pushed through the back of the housing during assembly. The polarizing key on the receptacle aligns with a slot on the header, so the connector can only be mated in the correct orientation.