Temperature setting for soldering?

[swordfishy]

Hi all,

I have always used cheap uncontrolled soldering irons with great success but recently went all out and bought a temperature controlled unit. Can someone please provide some insight or a rule of thumb for what temperature should be used when soldering 60/40 tin/lead solder? A quick google tells me that the melting point for this solder is 374 deg F (190 deg C), but this temperature is clearly too low judging by the results it gave me. I got much better results using 400 deg C, but I fear this may ruin sensitive components (such as my LM3875 chips). What are your thoughts?

Thanks,

Greg.

[Enzo]

The melting point of the solder is one thing, but the iron's job is to heat the joint hot enough to melt the solder.

Water freezes at 0 degrees, but if you want to freeze some you don't set the cooler to 0 degrees.

You are more likely to damage a circuit board or even parts with heat too low, honest. You want the iron hot enough to heat the joint quickly, so that solder melts into it freely, but also so heat doesn't have as long to move down the wires into the parts.

"I have always used cheap uncontrolled soldering irons with great success" is the most important thing you said. Your uncontrolled cheap iron has done a good job for you. That tells you your technique must be good enough, and that the iron temperature, whatever it was, was OK. It is not that critical.

I run a commercial repair shop, and I always use 700 degree tips in my irons. Sometimes I turn my desolder station up to 750 degrees, in particular when I have to suck out something on heavy wide traces, like a bridge rectifier snug against the board.

The key is to solder with confidence, Get on there, heat the thing up, flow solder into it and leave. When we start to worry about is it 8 seconds? or 10? or some such, I think we are more likely to underheat the joint leaving a poor joint. ANd when we solder confidently, we don't get into that pattern of solder, look at it, add some more solder, look at it, try and smooth it out with more heat, etc. ON it, and back off it.

Sorta like cooking rice, don;t lift the lid to look. Just do it and be done.

I have been soldering for about 55 years now, and I can;t say I have ever destroyed a component with heat. I make my share of mistakes, and I will admit to melting the contact out of the end of a fuse holder, but that isn't circuit board soldering. On a board I am more concerned over lifting a trace or pad than the parts themselves.

I think if you look at some IC data sheets there will be solder specs, so many degrees, so many seconds.

[Bakmeel]

Hand soldering always takes some practice yes. In our lab we usually set the irons a bit cooler than Enzo said: about 350C (660 F). That's usually enough to solder most components like resistors and semiconductors. Sometimes if we need to heat up large copper areas we turn up the iron to 400C (750 F).

Note that if you start using lead free solder (according to the new RoHS regulations for comercial electronics), you need higher temperatures..

[swordfishy]

Thanks for your replies.

It seems my guess at 400 deg C wasn't too bad. No wonder it worked so much better.

I've always soldered rather well (in my humble opinion) with my cheap irons. It's ironic that going to a better iron nearly ruined one of my projects due to a lack of experience!

Thanks,

Greg.

[AndrewT]

don't use 60/40.
It is not eutectic. It goes pasty as it sets and disturbing the joint during this pasty phase will destroy the electrical characteristics.

Use 63/37. The eutectic is designed for electrical/electronic work.

[richie00boy]

60/40 is designed for electrical/electronic work. But having recently tried 63/37 I will be sticking with that from now on, it does give a nicer joint.

[wintermute]

I use pretty much the same settings as Bakmeel, 350 for normal and 400 when there is something heavy to do. One sign that you have turned it up too far is when the tip blackens really quickly, if the temperature is ok it tends to stay shiny

My favourite solder actually had 2% copper, but I can't recall which of the lead or the tin was lower to make up for the copper. Not sure you can get it any more though.

Tony.

[Bakmeel]

Originally Posted by swordfishy

Thanks for your replies.

It seems my guess at 400 deg C wasn't too bad. No wonder it worked so much better.

I've always soldered rather well (in my humble opinion) with my cheap irons. It's ironic that going to a better iron nearly ruined one of my projects due to a lack of experience!

Thanks,

Greg.

You know, I actually think it's better to learn soldering using a crappy iron rather than using the top notch from day one. When you're forced to use a crappy iron, you automatically develop skills to get good results without relying on technology to do the job.

Then, when you finally get yourself a good solder station, you can appreciate it's better performance and you get the best out of it.

[Adrculda]

I use Kester 285 Medium and i never had any problems with my iron set at 600'F

[coloradosound]

Certainly try to use a eutectic blend and also make sure you are selecting a tip
size that is proper for the job. A wide trace / large component with too small a tip
is very difficult to transfer heat. Also wet the tip so there will be some hot solder to
form a thermal bridge.