Very high soldering temperatures and components/boards

J

jameuwissen

New member
Hello - novice builder and solderer here with some questions. I'm working with a Yihua 926 solder station and Weller lead free solder (SnCuNi alloy, 3.5% flux). I understand that lead free is far, far, far harder to work with- especially as a beginner, but lead vs lead free is not the question here. I understand it is important because I know you need much higher temps for soldering while using lead free. But I’m needing to push to temp levels that have me questioning myself and many other things... I cannot even get the solder wire to melt directly on the solder tip of any shape or size unless I am at >/= 820 deg F, and I have found that I get the most timely weld when I go at 839 deg F, and that is after heating up the through hole + component lead for anywhere between 8-15 seconds.

So…am I completely frying my boards and components at these temperatures? I looked at the data sheet for the 1k resistors I just soldered, they say the solderability is 245±5°C for 3±0.5 Sec. I’m currently soldering at 447 deg C to make it work within that 8-15 seconds. And I’m creating what appear to be OK joints, but again… did I fry everything here in the process? Does anyone else need that much time or heat, especially if using lead free? Any guidance is very appreciated.


Some other context : I’m using one of the standard conical tips that came with the iron (it’s 1.5mm diameter at the tip). I clean and tin it basically every 1 to (maybe) 2 components because I know I’m running super hot. I’ve watched a ton of videos, scoured forums just to make sure my technique and approach is at least adequate for a novice. I feel good with what I am supposed to be doing, but I am surprised at the temps.
I also had my dad give it a go too, since he has >40 years of welding experience that does include some soldering, and he was needing the same temps to get a weld. One thing he brought up is maybe the temp at the tip isnt exactly matching the temp that the iron’s thermostat is reading? I dont have any tools to test this, and I dont want to blame the tool when the vast majority of the time it is the user, not the tool, that is the issue…but I am just shocked that even trying to tin any tip with some wire, I cannot get the wire to melt directly onto the tip below 820 deg F when this stuff should melt somewhere in the neighborhood of 450 deg F.

Thanks so much, I am super grateful for these forums. I spent a lot of time here learning as much as I could before I made the jump.
 
I'm surprised you need to run this hot, especially if you're saying you can touch solder to directly to your iron and not have it melt until you have it up this high.

I use lead-free exclusively (SAC305, melting point ~220C). I keep my soldering station set to 360C and it works great, within seconds.
For hot air I go higher, about 400C.

I would imagine one of a few things going wrong:

- Your soldering iron is mis-calibrated and you're actually nowhere near your set point temperature. I'm not sure how to test this without some kind of high-temp thermocouple.

- Your tip has a layer of schmutz/oxidation on it that is preventing good heat transfer. Is your tip tinned? When you are heating a joint, do you have a layer of solder on your tip to help transfer the heat?

- Something going wrong with your technique, though it's hard to imagine what technique is required for "holding solder against my iron and it don't melt"

The Amazon Special Yihua 926s might be a bad knockoff/cheap clone. I wonder if you could borrow/beg something different and try it out.
 
Wonder if that 450 C is actually 450. Yihua can be fine, but I think cheap chinese brands usually are a bit off with what temp they show and actually is. I solder at 400 mostly, sometimes 375. I definitely don't struggle for 8-15 seconds to solder a resistor, something is off here.


Never soldered SnCuNi, but I struggled a bit finding solder that is satisfyingly easy to work with.

I have a roll of Chipquik SAC305 that is frustratingly hard to solder with and results in solid but very dull looking joints, I assume that it depends on the flux because I have some Goobay SAC305 that isn't hard to work with.

My current favorite is a roll of 0.6mm diameter Velleman 99.7% Sn, 0.3% Cu, but I've had better that I was not able to replace when I ran out of it.
 
I've found that going with what the technical specifications of the solder is the best course of action. The Indium brand 63/37 no clean core I've got says 350°C, so that's what I go with and it works like a charm.
 
My first thought was a tip that’s not mirror shiny. But a bad thermostat could also be the culprit. I don’t use lead free, basically I wash my hands when I’m done. I also use an exhaust fan for the rosin fumes—lead doesn’t vaporize until well beyond what your soldering iron can heat it to, so there are no lead fumes to worry about.

Also, get a small screwdriver or chisel tip; conical really doesn’t work as well for most things.
 
Alan W said:
My first thought was a tip that’s not mirror shiny. But a bad thermostat could also be the culprit. I don’t use lead free, basically I wash my hands when I’m done. I also use an exhaust fan for the rosin fumes—lead doesn’t vaporize until well beyond what your soldering iron can heat it to, so there are no lead fumes to worry about.

Also, get a small screwdriver or chisel tip; conical really doesn’t work as well for most things.
Click to expand...
This is my setup as well. The fan really helps to prevent clouded judgment if you're spending some time soldering away into the night
 
Alan W said:
I don’t use lead free, basically I wash my hands when I’m done.
Click to expand...

For me, switching to lead-free was about tracking tiny pieces of trimmed solder around the house (on my clothes, on my feet, etc).
When I'm trimming leads, especially under pots where I want them to lay flat, I trim them close to the board and sometimes cut some of the solder blob along with the lead. It can be hard to prevent those little pieces from flying off in random directions.
 
I use lead free solder exclusively, with a haako fx888 run at 750 F. Works very well, very easy to work with even if having to desolder something and wick it away with copper braid helped with some flux. Had trouble in past due to a bad iron tip. Chipped or dirty tips don't transfer heat well. I also put a tiny bit of solder on the iron before soldering a joint, which helps a lot.
 
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