SMD vs SMT vs THT — Differences, Costs, When to Use Each
SMD is the component, SMT is the manufacturing process that places it, and THT is the older through-hole technique where leads pass through the board and solder on the back side. They are not competing terms — modern PCBs use all three on the same board.
This guide clears up the vocabulary, shows the real cost gap, and explains when through-hole still earns its place on a 2026 design.
The three terms, defined precisely
| Term | Stands for | What it actually is |
|---|---|---|
| SMD | Surface Mount Device | The physical component — 0402 resistor, QFN IC, BGA package |
| SMT | Surface Mount Technology | The factory process — solder paste, pick-and-place, reflow oven, AOI |
| THT | Through-Hole Technology | Leaded components inserted through PTH holes and soldered on the underside |
People mix SMD and SMT in conversation, and that is usually harmless. They are tightly linked — you use the SMT process to assemble SMD components. THT is the odd one out: different parts, different process, different tools.
How SMT works on our line
Our SMT line in Strumica is a DDM Novastar setup: solder paste printer (SPR-45), pick-and-place (LS60), reflow oven, in-line AOI. A bare PCB enters one end, exits the other 60-180 seconds later with up to several thousand SMD components soldered and inspected.
The economics are brutal in favor of SMT:
| Metric | SMT (modern line) | THT (hand soldering) | THT (wave soldering) |
|---|---|---|---|
| Cost per joint | 0.005 - 0.01 EUR | 0.10 - 0.30 EUR | 0.02 - 0.04 EUR |
| Placements per hour | 20 000 - 60 000 | 60 - 200 | n/a (continuous) |
| Smallest part | 01005 (0.4x0.2 mm) | DIP-8 (~10 mm) | DIP-8 |
| Setup time per job | 30-90 min | 5 min | 45-90 min |
| Defect rate | ~50 ppm | ~2000 ppm | ~500 ppm |
At our capacity of 4.8M placements per year single-shift (14.4M three-shift), SMT is the dominant process. THT exists on most boards but as a finishing step — typically 2-20 leaded parts soldered by hand after the SMT side is complete and AOI'd.
When THT still wins
Through-hole is not dead. There are three honest reasons to use it in 2026:
1. Mechanical stress. Power connectors, USB-C jacks, big screw terminals, and 5+ amp barrel jacks take repeated insertion force. SMT pads can lift; THT through-holes do not. Almost every product with a user-facing connector uses THT for that connector even if everything else is SMT.
2. Power and thermal mass. Big electrolytic capacitors (470 µF and above), inductors handling several amps, TO-220 power FETs, transformers — these parts are physically large and thermally demanding. THT distributes heat into the board and gives mechanical anchoring.
3. RF shields and cage frames. Press-fit or soldered shield cans almost always use THT to clip the shield mechanically to the ground plane.
4. Repairability. Field-replaceable parts (fuses, batteries, relays) sometimes specify THT so a technician with a basic iron can swap them.
| Part class | Typical choice | Why |
|---|---|---|
| 0402 / 0603 / 0805 passives | SMT | Cost, size |
| QFN, BGA, QFP ICs | SMT | Only available as SMT |
| Crystals, MEMS | SMT | Both exist; SMT cheaper |
| Headers, connectors (signal) | SMT | Saves space |
| USB-C, RJ-45, DC barrel jack | THT | Mechanical stress |
| Big electrolytic > 100 µF | THT or large SMT | Designer's call |
| TO-220 power FET / regulator | THT | Heatsink, thermal |
| RF shield can | THT | Mechanical clipping |
| Fuses (5x20mm) | THT | Replaceability |
SMD vs THT cost — what it actually means for your bill
For a typical Class 2 industrial board with 400 SMD + 8 THT components:
- SMT side: 400 placements x 0.008 EUR = 3.20 EUR
- THT side (hand): 8 joints x 0.20 EUR = 1.60 EUR
- Total assembly labor: ~4.80 EUR per board
If the same board were 100% through-hole (hypothetical — most modern ICs do not exist in THT): 408 joints x 0.20 EUR = 81.60 EUR. That is the ~17x cost gap that killed THT as a primary process in the 1990s.
For more on European pricing structure, see our PCB assembly cost guide and the JLCPCB-alternative comparison.
Mixed-technology assembly — how a real board flows
A typical mixed board passes through our manufacturing process like this:
- SMT top side — paste print, place, reflow, AOI. 60-180 sec cycle.
- SMT bottom side (if double-sided) — flip, paste, place, reflow with adhesive-held top parts, AOI.
- THT insertion — operator hand-inserts leaded parts into through-holes.
- THT soldering — selective solder, wave solder, or hand soldering depending on volume and joint count.
- Cleaning if required (no-clean flux typically skipped).
- Test — functional test or in-circuit per customer spec.
- Inspection and packout — final visual, label, ESD bag.
For low-volume runs (50-500 units), hand soldering THT is most economical. Above ~2000 units of the same board, selective soldering pays back.
So — is SMD the same as SMT?
Strictly speaking, no. SMD is a component classification; SMT is a process. But in industry conversation people use "SMD assembly" and "SMT assembly" interchangeably, and that is fine. When you request a quote from us, "SMD" and "SMT" will be read as the same thing. THT is always called out separately because it changes the bill of materials and the process flow.
If you have a BOM with a mix of SMD and THT parts and want a price, the quote estimator handles both — or send the full BOM and Gerbers for a formal quote.
Frequently asked questions
Is SMD the same as SMT?
Not strictly — SMD refers to the component itself (a surface-mount device like a 0603 resistor or a QFN chip), while SMT refers to the technology and process used to assemble those components (solder paste, pick-and-place, reflow). In everyday conversation the terms are used interchangeably and that is generally fine.
What is THT?
THT stands for Through-Hole Technology. The component leads pass all the way through plated holes in the PCB and are soldered on the opposite side. It is the original PCB assembly method from the 1950s-1980s and is still used today for connectors, power components, and any part that takes mechanical stress.
SMD vs THT — which is cheaper?
SMT (assembling SMD parts) is roughly 20-50x cheaper per joint than hand-soldered THT, because the SMT process is fully automated. THT only stays cost-competitive when you need its mechanical strength or thermal mass benefits, or when running wave soldering at high volume.
When should I use THT components?
Use THT for high-current connectors, large electrolytic capacitors, TO-220 power devices, RF shield cans, fuses, and any part that experiences user-applied mechanical stress (USB ports, headers being repeatedly mated). Almost every modern PCB is mixed-technology with mostly SMT plus a handful of THT parts at the connectors.