Quote:
Originally Posted by RudolfXC
Solder, whether lead-free or otherwise is flux cored as you have stated so why use flux paste?
Lead free solder is not horrible to use and makes perfect joints with an iron tip temperature below 380 deg C - Leaded solder is horrible to use with toxic fumes and lead covered hands just by touching it.
I was sceptical at first, but after trying a few types at work, we have found a perfect lead-free solder that I use on all my RC cars and have had no joint failures.
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Flux paste to clean the iron tip. A damp sponge doesn't cut it, and leave impurities and residue, which blacken the tip. Dip the iron tip in the flux before you are about to make a joint gives you a perfectly clean tip ready to tin and use straight away.
Flux paste to clean and draw solder into the wire. Often the flux in the solder core isn't enough. Again it depends on the thickness of the solder, and cleanliness of the items being soldered. Sometimes its not needed, sometimes it helps.
The OP was asking for advice on why he was having problems soldering. Using flux can help, as will quality high temperature controlled irons with large tips, and decent solder. Using too low a power iron, with a small tip and lead free solder is a recipe for bad solder joints and problems making them. Others posted above me had offered constructive advice to the OP, most of which said use flux and leaded solder...
In my experience lead free solder is awful to use. It's melting point is higher, and flow rate is slower, and requires a much longer period of heat contact to make the joint. It sets very fast, sometimes too fast to get a tidy joint, where you end up with part of it molten, and part set. My temperature controlled solder station goes upto 480 deg C, and its just awful to use with lead free solder at all temps I've tried. Sure it may be fine for small electronic joints, but large 10awg or 12awg wire contacts, or making up nicad/nimh packs for example with a large tip its just horrible to use, when good old leaded solder allow for perfect joints where the solder flows and allows perfect joints to be made. I've tried lead free with the six soldering irons I have, both electric and gas, of various powers, sizes and tip types.
Lead free solder is typically suited to flow or wave soldering process for circuit board manufacture, and they all use flux, either screened or sprayed on in these processes. more modern methods (reflow soldering) user a flux and solder paste, but that's getting off topic.
Lead free was introduced as part of the RoHS directive, where hazardous substances were removed from workplace and manufacturing process, and rightly so for the sake of those people exposed to it every day. Using a bit of leaded solder on the occasion when needed for your hobby certainly won't kill you, providing you use it in a ventilated place, and don't breath the fumes, or give it to children to eat, etc. It's certainly easier to use leaded than get burned fingers trying to get lead free solder to flow to make the joint.
I won't get into an argument about who's the better solderer, but I learned to solder at 7 years old, and 30 years later consider myself experienced. Hey, I even won a prize for my soldering in my first year of my electronic engineering degree at university ;-) I'll happily put up examples of my work for inspection.
If you've found a good lead free solder, please detail the stuff, and i'll go out and buy some to try, or accept a sample in the post if you like? I'd happily try some and change to it if it works. The several different rolls I've bought and used were utter rubbish.
