Why the Cu2 in Sn60Pb38Cu2 solder?

[motzu]

Hello,

I'm trying to figure out if there's any benefit (or drawback) in using Sn60Pb38Cu2 solder vs. regular Sn60Pb40 solder. I have assumed in the past that the added Cu2 helps conductivity, but recently I've heard claims that 1) it can decrease the lifespan of soldering iron tips, and 2) that it only helps when soldering copper wires, by not disolving as much copper when soldering as regular solder would (which also sounds good for soldering copper PCB traces).

Is the Cu2 solder better for general purpose soldering? Worse? The same? The joints do look quite ordinary (no different than the 60/40 ones).

Thanks for reading!

[tedmich]

word is the Cu used to be required because of the tip plating/metallurgy and that now it isn't required. Some say the Cu introduces impurities but if its avaliable it likely works AOK. Its not like the Rohs tin whisker crap some are stuck with...

[motzu]

Oh yeah, it works just fine, the joints look OK and I've tested some of them for continuity and mechanical strength, no problems whatsoever.
I was just curious about the added Cu.

I agree about the RoHS solder.

Thanks for the post!

[jrfrond]

I've got to tell you, I've never even seen copper-bearing tin/lead solder. Most RoHs solders contain .5%Cu, but I've never seen 2% Cu in a tin/lead alloy.

I'll stick with 62/36/2 silver-bearing solder. It's all we use here.

[motzu]

I've pretty much just given up on it and I'm using only eutectic Sn63Pb37 solder now, but it's got nothing to do with it's performance. As long as you don't move the parts being soldered together for a while the joints are clean and shiny and seem to work well (as with any regular 60/40 solder), but just for the peace of mind I've switched to eutectic solder.

In case you're interested in more details about the Cu2 solder, mine's called Stannol HF-32, and here's its datasheet: http://www.soselectronic.hu/a_info/r...f/ine/hf32.pdf

[Bill Moore]

I don't currently have any Cu bearing solder, but I think it's a good thing. Our mines haven't started rehiring yet, but maybe if we all switch, it will put people back to work! You know when they started making mostly zinc pennies, it hurt.
There used to be a bumper sticker put out here in the 80's. "Eat beef, use copper, and buy Fords"
Seriously, it's only function could be to add a very small amount of strength to the joint.

[Albert Kreuzer]

Hot solder "eats" copper tips. The Cu is added to the Sn/Pb to prolong life of the solder tips.
Of course, this applies to copper tips only, not the plated, "wear-free" kind.