Soldering Basics
Introduction
Breadboards are great for learning, but real prototypes and kits need soldered joints — header pins on a dev board, wires to a motor driver, or your first PCB. Good soldering is a skill: hot iron, clean tip, flux, and patience. Bad soldering looks like a cold grey lump and fails when the robot vibrates.
This article covers tools, the basic through-hole technique, common mistakes, and when to desolder a mistake. Pair with Lab tools for prototyping.
Tools you need
| Tool | Purpose |
|---|---|
| Soldering iron | 60–80 W adjustable; fine tip for headers |
| Solder | 60/40 or lead-free; 0.6–0.8 mm diameter for students |
| Flux | Helps solder flow (often inside solder wire) |
| Sponge or brass tip cleaner | Wipe oxidized tip |
| Helping hands / PCB holder | Holds board while both hands work |
| Desoldering pump or wick | Remove excess solder |
Ventilation — solder fumes are not perfume. Work in a ventilated lab or use a small fan.
In plain terms
Soldering is gluing metal with molten metal. Heat the pad and pin together, then feed solder until it flows shiny — not a ball sitting on top.
Five steps (through-hole)
- Tin the tip — thin shiny coat on iron tip; wipe excess.
- Heat the joint — touch iron to both pad and component lead for ~2 seconds.
- Feed solder — add wire to the joint (not to the iron tip alone) until filled.
- Remove iron — hold still ~1 second; let cool without blowing on it.
- Inspect — shiny, concave fillet; no bridge to neighbor pad.
Headers on dev boards: solder one pin first, check alignment, then do the rest.
Common mistakes
| Mistake | Result |
|---|---|
| Cold joint (moved too soon) | Grey, cracked, intermittent |
| Too much solder | Bridges between pins |
| Iron too cold | Does not wet pad |
| Iron too hot / too long | Lifted pad, damaged PCB |
| Dirty tip | Solder beads instead of flowing |
SMD (surface mount) — later step
Student kits often start with through-hole. SMD needs finer tip, tweezers, and sometimes hot air. Practice on scrap boards before your main PCB.
Desoldering
Everyone bridges a pin or puts a resistor in the wrong hole.
| Method | When |
|---|---|
| Solder wick (braid) | Soak up solder from one pad |
| Suction pump | One-shot remove on through-hole |
| Hot air | SMD removal (advanced) |
Heat, remove solder, then gently lift the part. Do not yank a component while solder is solid.
Videos — soldering
Beginner five steps
Soldering Tutorial for Beginners: Five Easy Steps
Header pins on a dev board
Tools overview (EEVblog)
EEVblog #180 - Soldering Tutorial Part 1 - Tools
Using flux
Mistakes to avoid
10 STUPID ERRORS To AVOID in Soldering and TIPS
Videos — desoldering
Relevant topics
Starting points
- Practice on a scrap PCB or broken header strip before your main board.
- Solder headers onto your MCU board; continuity-test GND and 3.3 V pins.
- Film your joint in good light — grey vs shiny is obvious on camera.
- Desolder one intentional bridge with wick — know the recovery path.
Focus points
- Iron safety — assume hot; use stand; unplug when done.
- Lead-free needs slightly higher temp — follow solder manufacturer guidance.
- Wash hands after handling leaded solder in older lab stock.
- Joint quality beats speed — one good pin beats ten cold ones.
Key points
- Heat pad + lead, then add solder until the joint is shiny and filled.
- Flux, clean tip, and steady hands fix most student problems.
- Desoldering is normal — wick and pump are part of the toolkit.
- Soldered boards belong in your BOM and wiring diagram like any other assembly step.