Electronic – When is it OK for connectors to be SMT instead of TH

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A lot of boards with predominantly SMT components have TH connectors on them for things like headers and power connectors. Take a standard barrel power jack for example:

TH:

Through-hole power jack

SMT:

Surface-mount power jack

When designing a board, how do you decide whether a connector can be SMT or not?

Best Answer

The choice of through-hole versus surface-mount comes down to you, the designer of the PCB. To make that choice, you have to consider things like:

  • Assembly and tooling. Does the company or person assembling the PCB have the necessary tooling for the desired form factor?

  • Device construction and clearance. Does the device ultimately need to be space-saving? Are through-hole leads going to cause clearance problems in a restricted form factor? Is there another PCB or something nearby which through-hole leads and the resulting solder could be too close to?

  • Strain/durability. Is the DC jack going to be regularly exposed to physical wear and tear? Are users going to be plugging and unplugging the device often? Through-hole may afford some additional strain resistance and durability.

  • Cost. If you're building 100k units, a small difference in cost between the TH and SMT version of this component might matter.

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