Harness-floor IDC for 18 AWG — what this connector is
The TE Connectivity MTA-156 3-644878-6 is a 6-position receptacle that terminates 18 AWG discrete or ribbon cable through an IDC slot — no wire stripping, no crimp. It sits in the MTA-156 series at a 0.156" (3.96mm) pitch, wider than the common 0.100" IDC, which means the contact spacing and the wire gauge are matched for power distribution and heavier signal circuits on a harness. The housing is orange, closed-ended with a polarizing key, so the operator cannot load the wire from the wrong side or reverse the connector on the header.
Termination and wire prep — what the press operator needs
This is an IDC termination — the wire is pushed into the slot and the insulation is displaced by the tin-plated contact. 18 AWG is the specified wire gauge; the slot geometry is cut for that diameter, so stepping down to 20 AWG leaves a loose fit and stepping up to 16 AWG risks splitting the housing. The closed-end design means the wire stops at the back wall of the slot; there is no through-hole for the wire to poke out the other side.
Contact finish and mating cycles
The contact finish is tin at 80.0 µ" (2.03 µm). That is a heavy tin layer — thick enough to survive multiple insertion and extraction cycles without the galling you get from a thin tin flash. It is not a gold contact, so it is not rated for hundreds of mate cycles in a corrosive environment, but for a harness that is mated during assembly and then stays connected for the life of the equipment, the tin finish is the standard choice.
The 3-644878-6 is an active TE part, ROHS3 compliant. No official cross-reference or second-source equivalent is on record; the MTA-156 series is TE-specific tooling, so the header and receptacle are a closed system.