Soldering, burnt rosin?
 

I was getting some practice soldering in before installing my new motor and ESC (which has tabs that need to be soldered on) because it had been a while since my last soldering job. After a bit, some kind of brown burnt sugar-like substance was forming, causing the 60/40 rosin core solder to get some kind of brownish stuff in it.

Is this burnt rosin? I don't recall this happening before, is this normal? and how do I get rid of it?

Re: Soldering, burnt rosin?
 

Sounds like excess rosin and should clean off with some Isopropyl alcohol (IPA).

Re: Soldering, burnt rosin?
 

Cleaning the pieces to be soldered, and even the solder itself, with 90% isopropyl alcohol like Rich said will keep that brown substance from forming. Soldering is like painting and welding, prep is 80% of the finished result.

If not, it will scrub off easily after soldering with alcohol.

These acid brushes with a little more than half the bristles cut off at an angle with some scissors and dipped in alcohol work great. This is what we used in Navy circuit board repair school. Clean solder with a 1/8 of a paper towel square moistened with alcohol.

https://www.harborfreight.com/12-in-...UaAvYxEALw_wcB

Re: Soldering, burnt rosin?
 

That's just burnt flux residue. I would use a Rosin Low Activation flux core solder if your surfaces are dirty/oxidized. If your surfaces are relatively clean, just use a no clean flux core solder - that's what I use. AIM and Kester are good brands. Either can be cleaned with IPA (I use 99.8% IPA at work).

Re: Soldering, burnt rosin?
 

You clean the solder and pieces to be soldered with alcohol before doing anything?

Re: Soldering, burnt rosin?
 

I have learned to live with it

Re: Soldering, burnt rosin?
 

Prefaced by saying I was trained to Navy standards so maybe a tad unnecessarily anal, prep goes a long ways toward good solder flow and adhesion. Oxidation forms almost immediately on a soldering tip and solder and impedes both. Is it necessary? No, it shouldn't be, and it likely isn't as often as you and I solder. Brand new solder roll, or left to sit for 4, 6 months, a year, yeah, swiping the solder exposed on the roll while idle with an alcohol dampened paper towel is probably needed. And I always clean anything to be soldered with the modified acid brush lightly soaked with alcohol.

I hate flux, never use it, haven't since 2M school where it was taboo. If you're using good 63/37 solder of an appropriate gauge (and not the flux core crap), a properly tinned clean, dry and thermally shocked tip and cooking at the correct heat it's completely unnecessary and only makes a mess that you have to clean up after cool down to get rid of the sticky brown corrosion magnet it leaves behind.

Re: Soldering, burnt rosin?
 

I see. Now I know! Thanks.

I agree on the flux. I rarely use it.