What temp do I set my soldering station for these solders?

I finally bought a decent temperature controlled soldering station, a Hakko FX-888D. Up till now I've just used the right iron (among many that I have) with a big enough tip and heat transfer for the job I was working on. Experience taught me over time which one to use for what.

Now that I have the Hakko I have started looking at the recommended melting points for the various solders I use. I use mostly either Cardas Quad Eutectic or RS Silver Bearing. I like the Cardas because it never fails to make a nice shiny joint. But the data on these solders doesn't look right. The Cardas melting point is ~370F, the RS about 420F. These temps seem too low. My recollection is that most solders (of a Pb type) do best around 550-600F - not that I've ever been able to measure this before.

I tried setting the Hakko to 420F for the RS Silver and once the temp was set I couldn't even get a smooth fluid flow on a small ball tip. It sort of clumped up and didn't "flick" off the tip when I scrubbed it against the damp sponge. So I don't know what to make of the published numbers. I'm assuming the Hakko is working correctly. What temp do I set for either of these solders? Assume standard through hole type work.
 

rif

Member
Paid Member
2003-01-27 2:36 am
South NJ
See if you can get a hold of the materials data sheets.

I know you're not using it, but as an example, Kester 44 (63/37) says:
"Solder iron tip temperatures are most commonly between 315-371°C (600-700°F) for Sn63Pb37 and Sn62Pb36Ag02 alloys."

That's a wide range, but gives a good starting point or confidence you're in the ballpark.
 

rif

Member
Paid Member
2003-01-27 2:36 am
South NJ
Before you bump it up, maybe too high, try using the side of the solder tip:

Heat transfer also depends on surface area of contact between tip and joint -- the end of a conical tip of the tip transfers heat slower than if you use the tip's side, which will have a larger area of contact.

I'm not a very experienced solderer, but this is what I have gathered from others.
 
Tony -

Bear in mind that the things that you're soldering are absorbing the thermal energy from the soldering iron tip and cooling it down. If you try to solder at the melting point of the solder (or slightly above), as you have discovered, the joint never really gets hot enough to make a good connection. You probably could, if you wait all day and heat the bejesus out of everything associated with the joint, but you'd also fry your parts.

The manufacturer's suggestion of about double the melting point of the alloy is to let you make good, quick joints. Up to a point, hotter is actually BETTER, and lets you make connections faster and with LESS potential damage to the parts being soldered. Think of it this way - you need 'X' temperature to melt the solder (and this means that you need to get whatever you're soldering to that temp, so the solder melts in and wets it rather than just globbing on the surface). You can hit it with an iron at 'X' plus 10 degrees, and have the heat flow out of the joint and into the surrounding components almost as fast as your iron can add it, in which case you'll *eventually* be able to solder when the surrounding components get nearly as hot as the joint and the outflow of heat slows, or you can blast it with 2 'X', and basically ram the thermal energy in so fast that it doesn't have time to dissipate out through the leads, the joint gets hot and the solder melts very quickly. The second method uses a hotter iron, but in fact adds less overall heat to whatever you're soldering because that high heat has such a short dwell time.

I hope that makes sense.

-Pat
 
And as an addendum to the above, if you're soldering small joints, you can get away with a lower tip temperature because they have less of a heat sinking effect. Bump the temp up to get faster transfer when you're doing something larger that will suck the heat out of the joint. I use regular old 60/40 or 63/37, and generally have the iron (an 80W Weller) set to 660*F. For something bigger, like for instance a banana plug or heavy gauge wire, I'll bump it up to 780-850*F depending on the mass of what's being soldered to.

-Pat