Resin Core Solder — 60/40 Sn/Pb 1.6mm

Q: What does "resin core" solder actually mean?
The flux is built into the centre of the wire. When the wire melts, the flux comes out, cleans the copper surface, and lets the solder flow and stick. Resin flux leaves a mild, non-corrosive residue safe for electrical work, so no cleanup is needed on exposed joints.

Q: What does "60/40" mean?
60% tin, 40% lead by weight. This ratio sits close to the eutectic point so it melts cleanly at around 183 to 190°C instead of going through a mushy slushy stage like other ratios. Easier to control, less likely to cold-joint.

Q: Why 1.6mm and not something thinner?
1.6mm suits medium-to-heavy automotive cable sizes: 3mm, 4mm, 6mm, 8mm, up to 10mm single cores. Thinner solder (0.7 to 1.0mm) is for PCBs and fine electronic work. 1.6mm feeds enough metal into a cable joint without needing ten in-and-out passes.

Q: What temperature should I set my iron to?
300 to 350°C tip temperature covers most automotive solder work. A hotter tip (380°C plus) is fine for heavy cable but risks damaging insulation. If the solder beads up and will not flow, the tip is too cold or the copper is dirty. Usually not the solder's fault.

Q: Do I still need extra flux?
For clean, new copper, no. The resin core carries enough. For old, oxidised, or re-worked wire, a dab of extra rosin paste flux helps the solder flow. Never use acid flux (plumbing flux) on electrical joints. It corrodes copper over time.

Q: Is this lead-free?
No. This is a leaded alloy (60% tin, 40% lead). Lead solder is the industry standard for automotive and 12V DC electrical work because it flows cleaner and sets at a lower temperature than lead-free. Lead-free solder (SAC305) is used where lead is restricted, such as consumer electronics for the EU market. For a wiring joint behind a dash or in a trailer loom, lead is still the trade pick.

Q: Can I use this for the 240V mains wiring in my caravan?
No. AS/NZS 3000 (the Australian wiring rules) bans soldered joints in fixed mains-voltage installations. Mains joints are crimped, screwed into terminals, or made in approved junction connectors. Leaded solder is for the 12V and 24V DC side of the build only. For 240V work on a caravan, bring it to our Perth workshop (we're EC17073 licensed) or any qualified sparky.

Q: Solder vs crimp, which is better for a wiring joint?
Both work; use the right one for the job. Crimp with heatshrink is faster, more flexible, and the industry standard for in-vehicle looms (it resists vibration fatigue when done well). Solder makes a lower-resistance joint but turns the wire rigid at the joint, and vibration can crack it over time. Rule of thumb: solder plus heatshrink for a permanent one-off (battery terminals, grounding points); crimp plus heatshrink for anything that moves, flexes, or might need to come apart later.

Q: Do I need to clean the joint after soldering?
With resin flux, no. The residue is non-corrosive and electrically safe. It leaves a slight yellow or amber tint on the joint. Only clean it off if the joint will be visible or you want a tidy finish. Isopropyl alcohol or flux remover takes it off.

Q: What size solder should I use for finer cable like 1mm?
1.6mm is on the heavy side for a 1mm or 2mm single core. You'd feed too much metal in. For fine wiring (PCB work, LED strips, sensor cables), use a 0.7mm or 1.0mm solder. For medium automotive wiring (3 to 6mm cable), 1.6mm is spot on. For heavy battery cable (16mm plus), use a torch and a stick solder, not a wire feed.