Soldering and connectors: what I wish I knew earlier
When I started tinkering with electronics I thought soldering was just melting a bit of metal and sticking things together. It isn’t. A few small habits and better equipment transform weak, intermittent joints into reliable connections that last years. These are the practical lessons I wish I’d learned sooner — everything from kit choices to step-by-step technique, plus the common pitfalls that waste time and money.
Essential kit (buy once, buy right)
- Temperature-controlled soldering iron (25–60W) — crucial for consistent joints.
- Quality solder: 60/40 tin/lead for ease, or 99.3% tin lead-free if required; 0.6–0.8mm for general work.
- Rosin flux and a no-clean flux pen for corrosion-free joints.
- Good side cutters, precision wire strippers, and a ratchet crimper for crimps.
- Heat-shrink tubing and a small heat gun for strain relief.
- Spare tips, tip cleaner (brass sponge) and safety glasses.
Actionable steps: reliable solder joints every time
- Clean and prepare: strip 2–3mm of insulation, twist strands lightly. Clean PCB pads with isopropyl if greasy.
- Tin the wire: heat the wire briefly and apply solder until strands are coated — this prevents stray fibres and improves heat transfer.
- Apply flux to pad and wire: even a little rosin makes solder flow beautifully.
- Heat both parts: press the iron so it contacts the pad and the wire at once. Heat for a second or two.
- Feed solder to the joint, not to the iron: the solder should flow onto the heated parts. Remove solder, then iron, and let cool undisturbed.
- Inspect: a good joint is shiny and concave, not blob-like or dull. Trim excess and add heat-shrink for strain relief.
Choosing connectors: match method to purpose
Connector choice affects reliability and serviceability. For permanent, high-current or vibration-prone installations, crimping with the right ferrules wins. For prototypes and small hobby boards, soldered headers and JSTs are fine. Terminal blocks are handy for quick swaps but can loosen over time.
Common pitfalls and how to avoid them
- Cold joints: caused by insufficient heat or moving the joint while cooling. Solution: heat properly, let cool naturally.
- Overheating: destroys pads, melts plastics and ruins connectors. Use temperature control and a suitable tip size.
- Poor crimping: cheap tools give inconsistent crimps. Use ratcheting crimpers and ferrules for stranded wire.
- Wrong solder: too thick or wrong alloy leads to poor wetting. Choose 0.6–0.8mm and appropriate alloy for your work.
- No strain relief: cables flex and break joints. Use heat-shrink or cable ties to protect joints.
Quick comparison
| Connector type | Best for | Pros | Cons |
|---|---|---|---|
| Crimp (Ferrules) | High vibration, automotive, power | Consistent, strong, serviceable | Needs good tool and ferrules |
| Soldered (JST, wires to pads) | Prototypes, small PCBs | Compact, low cost | Harder to disconnect, heat-sensitive |
| Screw terminal | Field wiring, quick swaps | Tool-free, reusable | Can loosen; less compact |
Conclusion
Soldering well is more about preparation and the right tools than raw skill. Invest in a temperature-controlled iron, learn to tin and use flux, and choose connectors that match the application. That small extra spend on a good crimper or proper ferrules pays off in reliability — and saves hours of fiddly rework. If you’re buying kit, look for reputable brands and kits that include extra tips and spares; if you need help with a larger job, a professional wiring or electronics service can be worth the cost.
FAQ
Do I need lead-free solder?
Not always. Leaded 60/40 solder is easier to work with and gives better wetting. Use lead-free where regulations or safety policies require it.
How hot should my iron be?
Around 320–360°C for most electronics. Lower for delicate boards, higher for heavy joints — use a temperature-controlled iron to adjust as needed.
When should I crimp instead of solder?
Choose crimping for high-vibration or power connections and when you need a repeatable, serviceable joint. Solder is fine for small signal wires and prototypes.
Why is my joint dull and flaky?
That’s a cold joint. It means the parts weren’t heated enough or they moved while cooling. Reheat, add flux, and rework the joint.
How do I prevent melted plastic connectors?
Use the correct tip size, heat briefly, and consider soldering wires to pads rather than directly on plastic housings. Use heat sinks or clamp the plastic away when possible.