THT vs SMD soldering: what is the difference?

THT and SMD are two ways to mount parts on a circuit board. With THT (through-hole) the leads go through drilled holes and are soldered on the other side - robust, ideal for connectors and power. SMD parts sit on surface pads, are smaller and allow higher density.

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THT

leads through the hole, robust hold

SMD

part on pad, high packing density

Reflow

standard process for SMD in volume

Hand-solderable

both can be soldered by hand

Inhalt

Basics
Comparison table
Tools and technique
Frequently asked questions

What separates THT and SMD?

The difference is how parts are mounted. With THT (through-hole technology) the component leads pass through drilled holes and are soldered on the opposite side. With SMD (surface-mount device) the part sits flat on solder pads on the same surface - no hole.

Terms: THT describes the part, SMT (surface-mount technology) the process, SMD the surface-mounted part. In practice SMD and SMT are often used interchangeably.

THT: mechanically robust, good for connectors, relays and power parts
SMD: small and light, high packing density, both-side placement possible
Many assemblies combine both techniques on one board

THT vs SMD - the direct comparison

THT wins on mechanical load and hand soldering, SMD on miniaturisation and automation. The table sums up size, technique and use:

Feature	THT	SMD
Size	larger, with leads	smaller, no long leads
Mounting	leads through the hole	part on surface pad
Soldering	other side, iron or wave	reflow, hot air or fine tip
Hold	very robust, pull-resistant	flat, less mechanical load
Use	connectors, power, relays	high density, ICs, passives

Which tools and technique do I need?

THT is soldered by hand with an iron and solder wire on the solder side. SMD is soldered in volume in a reflow oven, but can also be done by hand with a fine tip, flux and tweezers, or with hot air.

THT by hand

Iron, medium tip, solder wire - insert the leads and solder on the opposite side.

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SMD with a fine tip

Fine tip, flux and tweezers for individual pads and small parts.

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SMD with hot air

Hot-air station for multi-pin ICs and rework - heat the part evenly.

Hot-air rework

Mind ESD: parts and assemblies are static-sensitive. Work grounded at an ESD bench with dissipative tools - see also Hot-air rework.

Frequently asked questions

What is the difference between THT and SMD?

With THT the component leads pass through drilled holes and are soldered on the other side. SMD parts sit flat on solder pads on the surface, with no hole. THT is more robust, SMD smaller and denser.

Can SMD be soldered by hand?

Yes. In volume SMD is soldered in a reflow oven, but by hand it works with a fine tip and flux or with a hot-air station. Very small packages are demanding but feasible.

When do you use THT instead of SMD?

THT is used for mechanically loaded parts: connectors, relays, large capacitors and power components. SMD dominates where high packing density and automation matter.

The right technique for THT and SMD

Soldering stations, fine tips and hot air for through-hole and surface-mount work - from a single source.

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Reviewed

Content reviewed by soldering specialists.

ESD-safe

Tools for the ESD workstation.

Wide range

For THT and SMD alike.

Expert advice

Personal advice on soldering technique.