Bad solder? Thinner solder barely melts

[laserpon3]

Hello Guys,

I work with leaded solder and it melts like a butter, the thickness I have worked with for a long time is 0.7mm.
Recently I wanted to try thinner solder and see if it would help with precision for very small joints.
Picture of it here:


So the logical step for me was to go for a much thinner solder.
I wanted to stick to lead like the previous one and so I did.
Me having having no past issues with many other solders (thus barely any experience with them) went on ebay and bought some cheap 60/40 0.3mm solder.
Picture of it here:


However this solder was bad as soon as I tried it...
I even had my soldering iron at 255°C  ( 491°F ) and It would still barely melt, unless there was some solder from the other one still stuck to the iron.

Why is this solder barely melting and what should I look for to prevent this from happening? (Is there no flux in this solder? How can I detect this)
I know some people will say: "stick to the big brands" personally I agree but I'd like to know whats causing it and how I can detect it lacking or having the thing needed for it to melt properly (So I can learn from it).

Cheers guys!

[UPI]

We run 700°F STTC-140 tips in our Metcals with .020" solder.

[ejeffrey]

250C is too cold.  While it is above the melting point, it is hard to transfer heat effectively enough to melt the solder.  Remember, you have to heat your workpiece hot enough to melt the solder for it to wet properly and make a good joint.  Try increasing the temperature to 325-350.  You can go even hotter, but you shouldn't need to for tin-lead solder.

If you still have problems getting solder to melt properly, it could be a dirty or corroded tip surface, or the heater or thermocouple could be malfunctioning, keeping the tip from reaching the right temperature.

[cwalex]

I don't recognise the brand. I have had mixed luck with unknown solder brands but great results with brand named 63/37 solder. I got some 63/37 solder on ebay from sure electronics web store and it is great but they don't have it anymore. It came without a spool LOL but it works really nice. Now I only buy 63/37 instead of the more common 60/40.

Try multicore or kester brand and you shouldn't have any problems. I haven't tried kester but others here swear by it.

[G7PSK]

Easy enough to check for flux in solder cut it and look at cut end with magnifying glass you should be able to see the flux cores, one reason it does not melt as easily as your previous solder is drawing lubricant residue which id quite likely silicone based. Try cleaning the solder before use.

[ConKbot]

We run 700°F STTC-140 tips in our Metcals with .020" solder.

+1

600F for SMT/small thoughhole PCB work, 700F for heavy SMT (soldering TO-220 or the SMT equivalent pads) and heavier though hole stuff, on my metcal iron at work. 

On conventional thermocouple/thermistor based irons I'd start at 650 for everyday soldering and creep upto 750 as stuff got heavier.

[lapm]

badly melting solder is sign of too low tempereature. personally the little soldering i do i run mu station at 350 celsius (about 660 farenheit). This usually ensures plenty of heat energy ready to flow in soldering joint... After all, your soldering iron is sort of heat capasitor with small heat generator... Narrower the tip, harder it usually is to move heat from soldering iron to where you really want it...

[mariush]

Yes, you want the temperature of the tip high enough to melt the solder, but at the same time you don't want it so hot as to make the flux boil or go in a puff of vapor the moment you put the tip on the solder. The flux is supposed to go liquid and hit the surfaces you want to solder, not vaporize on the tip.

That roll of solder is not only thin diameter, but it's also just 1.2% flux, and considering it's a no-name spool, the flux may be inconsistently spread in the wire or even missing at certain points. The solder wire surface may also be somewhat oxidized or dirty, so it wouldn't hurt to drag the solder wire through a cloth impregnated with isopropyl alcohol before actually using it.
 

[nukie]

If your solder wire is working properly and this new wire is same composition but thinner, I say bin the crap. Usually thinner wire melts easier. This might not even be purely 60/40.

[mikeselectricstuff]

I just received some of this very cheap 0.3mm solder - seems pretty good.

http://www.ebay.com/itm/160619728934?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649