Can a board use both SMT and through-hole parts?

Yes, and most industrial boards do. The SMT side is printed, placed and reflowed first, then through-hole parts are inserted and soldered by selective or wave solder. The design rules for each side differ, so the assembly drawing should state which process applies where.

Is an SMD always smaller than a through-hole part?

Usually, but not always: power resistors and connectors can be large in either package. What changes is how the part is attached, and therefore which process, stencil and inspection method the board needs.

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SMT vs SMD: What the Terms Mean

One is a process, the other is a part. Mixing them up hides the fact that a through-hole design can still be assembled on an SMT line.

Hitech Circuits Engineering Desk

Shenzhen, China · PCB fabrication and assembly

2 min read

Published: 2018-10-10

Last updated: 2026-10-18

Technical review: Process figures checked against our published capability sheet. View capability sheet

WHAT IS THE DIFFERENCE BETWEEN SMT AND SMD

SMT is the process

Surface-mount technology describes printing paste, placing components on pads and reflowing the assembly. It applies to any package that can be soldered on the surface.

SMD is the part

A surface-mount device is a component designed for that process: chip resistors, SOICs, QFNs, BGAs, and so on. The package determines the footprint, the stencil aperture and the inspection method.

Why the distinction matters

When a drawing says "SMT assembly", it describes the process; when the BOM lists an SMD, it describes the part. A mixed board needs both processes documented, and the through-hole side must not be reflowed with parts that cannot take the profile.

Technical Specifications

SMT: surface-mount technology — the assembly process
SMD: surface-mount device — the component package
Mixed builds: SMT reflow followed by selective or wave solder

Frequently Asked Questions

Can a board use both SMT and through-hole parts?
Yes, and most industrial boards do. The SMT side is printed, placed and reflowed first, then through-hole parts are inserted and soldered by selective or wave solder. The design rules for each side differ, so the assembly drawing should state which process applies where.
Is an SMD always smaller than a through-hole part?
Usually, but not always: power resistors and connectors can be large in either package. What changes is how the part is attached, and therefore which process, stencil and inspection method the board needs.

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