Through-Hole vs. Surface-Mount Soldering Explained

If you’ve looked at any modern circuit board, you’ve seen two very different kinds of components: ones with legs poking through holes, and tiny ones sitting flat on the surface. These represent the two families of soldering — and knowing the difference shapes which kit and tools you should buy.

Through-hole (THT)

Through-hole technology uses components with wire leads that pass through holes in the board and are soldered on the other side.

Pros for learners:

• Larger, easier to handle
• Forgiving — there’s room for error
• The mechanical grip of the leads holds parts in place while you solder
• Perfect for understanding what a good joint looks and feels like

Almost every beginner practice kit and project kit is through-hole for exactly these reasons. The Elenco SP-1A is a textbook example.

Surface-mount (SMD / SMT)

Surface-mount devices (SMD), assembled using surface-mount technology (SMT), sit directly on pads on the board’s surface. They’re how nearly all modern electronics are built because they’re smaller and cheaper to manufacture.

What’s different for the solderer:

• Parts are small — sometimes the size of a grain of rice or less
• You hold the part with tweezers while you tack one pad, then solder the rest
• Flux matters much more
• A fine tip and a magnifier or microscope help enormously

It’s a real step up, which is why dedicated SMD/SMT practice boards exist. They give you rows of footprints to practice on cheaply.

Which should you learn first?

Through-hole, without question. It teaches the fundamentals — heat the joint, feed the solder, watch it flow — with components you can actually see and grip. Build a couple of through-hole kits until clean joints feel automatic.

Then graduate to surface-mount. Buy an inexpensive board (a multi-pack gives you several attempts), add a fine tip, good flux and tweezers, and practice placing and reflowing the smallest parts you can.

Tools that bridge the gap

To move into SMD work you’ll want:

• A fine conical or small chisel tip for your iron
• Liquid or gel flux — it makes solder flow exactly where you want
• Fine-tip tweezers for placing parts
• A magnifier or USB microscope — your eyes will thank you
• Thin solder (0.5 mm or finer)

Through-hole vs surface-mount at a glance

Common SMD package sizes

Surface-mount passive parts are named by their size in hundredths of an inch:

Chips are described by pin spacing (pitch): SOIC parts at 1.27 mm are manageable by hand, finer TSSOP and QFP parts need drag soldering with plenty of flux, and leadless QFN parts are easiest with hot air.

How to hand-solder an SMD resistor

1. Add a little flux to both pads.
2. Tin one pad with a small amount of solder.
3. Hold the part with tweezers, reheat the tinned pad and slide the part into it. Remove the iron and let it set — the part is now tacked.
4. Solder the other end normally.
5. Reflow the first end with a touch of flux so both joints are clean.

Start at 1206 and step down only when the larger parts come out flat and shiny every time. A graded board such as the Gikfun EK7028 or the QLOUNI kit with iron is designed for exactly that progression.

Master both families and there’s almost no electronics project you can’t tackle. Start with our beginner soldering guide, then pick the right board for the skill you’re building.