Help getting rid of flux

Well i soldered some boards up and im selling them but they have all the left over flux on them? What kind of chemical can i use to get it off. Its a pain to wipe because all the pin heads sticking up makes the rag get stuck in the sharp ends.

I use isopropyl alcohol. takes the flux right off. use a small brush to get at the hard to reach places.

Use good quality, water soluble flux based solder, and scrub the bare boards thoughourly in warm water after mounting the components, or at the very least use a "no clean" type. Flux residue left behind on boards and wiring will only cause problems later in the life of the product.

I've used no-clean flux and it still leaves a mess - dust sticks to it. I worry that high humidity causes the dust to become conductive.

ya, im using some of this no-clen flux and it is still everywhere. I have used alcohol with like 95% isopropyl and scrubbed it like no tomarrow with no resaults. I think is time to find new flux.

Are you using some sort of high-flux solder??. Ive never left even a hint of flux on any new boards that I have soldered.
If I have a older board that has a bit of flux left after resoldering a component, I just use a drop of isopropyl alcohol, and a dollar store tooth brush, and its gone with a few wipes.
Are you certain that you are not overheating the copper on the board during soldering, and the glue that bonds the copper to the board is not escaping...looking like burned flux?
I remember that in the 80,s and 90's, cheap copper clad boards sold thru mail order surplus places often had this problem, of whatever was used to bond the copper to the board bubbling out from under the pads while soldering, even at low iron temps. It too was a terror to clean off.

The stuff I am using just now still contains lead (60/40) , but uses a Hydrox flux, 0.7mm made by Multicore. It washes off with a little warm water and a small brush to agitate it, leaves your joints all shiney and new, assuming they were soldered properly to begin with. The other stuff I used was also a Multicore solder, same gauge, same content, but used a no clean flux. I found that it still leaves a little residue, but again washes off without any trouble.
The stuff I am using just now can be left on a board overnight and still washes off no problem, the no clean stuff had to be washed off within say 4-5 hours otherwise it got stuck on there and needed some alcohol to completely remove it.

Well i have never used the corret way of soldering, i just tin the tip and use the solder on the tip to solder the components to the board. For flux i use this stuff that used to be liquid but i left the top open and now its more of a gooey paste. I have no problems with any of it just that it leaves a mess. I have never soldered the correct way of heating up the component and applying solder just becasue i dont want to get anything too hot and fry things.
Im thinking that i just need to go buy a new flux and see what works.

No, you need to start soldering properly! - there's no need for any extra flux on normal leaded components - just heat the joint and apply the solder to the joint.

Your 'spooning' method is only suitable for eating soup! - NOT soldering!.

markland556 said:

Well i have never used the corret way of soldering, i just tin the tip and use the solder on the tip to solder the components to the board. For flux i use this stuff that used to be liquid but i left the top open and now its more of a gooey paste. I have no problems with any of it just that it leaves a mess. I have never soldered the correct way of heating up the component and applying solder just becasue i dont want to get anything too hot and fry things.
Im thinking that i just need to go buy a new flux and see what works.

Click to expand...

Uhhh...yeah...learn to solder properly. You'd be suprised how much heat the ICs can handle. Your work is probably nothing but cold joints- you must heat up both the component lead and the PCB pad for the solder to adhere correctly.

Im just afraid of killed LED's and resistors. But im gunna try to do it right now. I should probably turn the heat down on my iron, i have it all the way up and it supposidly goes to 400 degrese.

400F or C? 400C is a tad high but not destructively so as long as you don't hold there longer than around 15 seconds. I doubt your iron is all that accurate, anyway. just play with the temperature so that your joint heats up in no more than 2 or 3 seconds. remember to apply the solder to the joint, not the iron though I usually get a small blob on the iron to help heat transfer. Also, if you are soldering big stuff, you might want to use a larger tip (more thermal mass) - those little tips take forever to heat up the big stuff.

If you are soldering TH components using rosin core solder, you don't really need liquid flux. I only use liquid for surface mount components.

markland556 said:

Im just afraid of killed LED's and resistors. But im gunna try to do it right now. I should probably turn the heat down on my iron, i have it all the way up and it supposidly goes to 400 degrese.

Click to expand...

That's way too hot, I run mine about 300 degrees - the fears of damaging components only really applied to the old germanium transistors, modern silicon semiconductors can stand FAR more heat, and it never applied to resistors at all. Having the iron too hot will make soldering difficult as well, it's not critical, but much too hot, or much too cold, will really make you struggle.

Bear in mind, if you've got the slightest level of soldering ability (and you probably haven't, because you've never soldered yet!), then a joint should only take around 0.5 second to 1 second - it's that fast and simple.

I taught my daughter to solder when she was about 8 years old, she's built various Velleman kits since - it only took 10 minutes or so to teach!. At school, on the VERY odd occasions they did some electronics, she was the best solderer in the class, including the teacher!. She's NEVER killed a component by overheating, and I've never actually seen anyone who has!.

Nigel Goodwin said:

She's NEVER killed a component by overheating, and I've never actually seen anyone who has!.

Click to expand...

though it is possible to lift PCB traces with too much heat. especially desoldering...

philba said:

though it is possible to lift PCB traces with too much heat. especially desoldering...

Click to expand...

Yes, I do it purposely - to lift unused tracks on veroboard - heavily tin the unwanted track and give it plenty of heat, you can then easily peel it off with a sharp blade.

Certainly some of the very thin PCB tracks are easily damaged when removing components.

Well it looks like all my real fears are nothing more than me acting up. Thanks for the info guys. Ill post some before and after. LOL

Holy Crap guy...you mention that you are selling these boards. I dont know how they will work....for long, as the chemical you are slapping on is slowly eating away at the solder joints, AS WELL AS THE COPPER ON THE BOARD...and will eventually break down the connections. How the hell can you be a "experienced member"...if you dont even know how to solder?!!!!!!!???.
Its a bit like saying that ur a Prostitute...yet still a Virgin.

The soldering technique that you are using is best suited for plumbing, not PCB work....PERIOD...and wouldnt even make particulary good connections in the plumbing field
If you are concerned about cooking components....its practically guaranteed that you will, with the technique that you are using!

Do yourself a favour....go out and get yourself a good quality, low-wattage soldering iron, or a adjustable temperature unit...specifically for pcb work, and a good quality electronics solder.

Once again GOOGLE saves the day
(just 1 example...there are literally hundreds of soldering guides available)
http://www.epemag.wimborne.co.uk/solderpix.htm

HEAT THE JOINT....NOT THE SOLDER. JUST PUT A SMALL AMOUNT OF SOLDER ON THE TIP JUST PRIOR TO SOLDERING, TO HELP WITH THERMAL TRANSFER....this will allow the solder to flow onto the pad much quicker, and at a lower temperature. The amount of solder on the tip should NEVER be enough to actually make the joint. Keep touching the solder to the joint, until it begins to melt, then just let the solder flow over the joint...nice and smooth, and shiney...and dont use a ton of solder, just enough to make a good quality joint. Inspect your joints with a magnifying glass, until you get good at it. Buy a solder sucker as well, so if you have a bad joint, or have too much solder, that reheating, and resoldering will not help, you can slurp up the connection and start again
Follow these simple rules of soldering....with the right size pencil, and solder....KEEP WIPING YOUR TIP WITH A WET SPONGE OR CLOTH, BEFORE AND AFTER EACH JOINT, and you will NEVER cook a component, and the amount of left over Rosin will be almost neglegable.
REMEMBER...A CLEAN TIP IS YOUR BEST FRIEND...CONSTANT WIPING OF THE TIP BEFORE AND AFTER EACH JOINT WILL MAKE THE BEST CONNECTION...BOTH VISUALLY, AND MECHANICALLY. AS WELL, TINNING OF THE TIP PRIOR TO EACH SOLDERING SESSIONAND AT THE END OF EACH SESSION, WILL PROLONG THE LIFE AF THE TIP, AND WILL GUARANTEE A TIP THAT IS EASY TO KEEP CLEAN DURING THE SOLDERING PROCESS. YOU DONT NECESSARILY NEED ANY SPECIAL TINNING PASTE, LIKE SHOWN IN THE GOOGLE LISTING....FINE SANDPAPER, OR STEEL WOOL WILL ALSO DO.

You seem to be almost as bad as a friend of mine that I had in grade school. Whenever he soldered, he would hold the iron abouut 1 inch above the connection, heat the solder on the tip until enough melted, and dripped onto his connection. He always wondered why my circuits worked, and his didnt. I made a lot of money resoldering his projects over one summer.

Oh dear...

Learn to solder properly, using the right tools for the work in hand. It will save you a whole lot of hassle in the long run.

OK, if you address the solder before the iron, you won't damage the componet(solder on iron on, iron off solder off) it's all to do with latent heat. IPA is very good at removing flux but if you can't get hold of any then nail varnish remover (acetone), without lanolin, will do the trick.

be careful with acetone, it will also disolve some paints and plastics. IPA (that's isopropyl alcohol, not India Pale Ale) is a much better choice.

But I do recommend India Pale Ale when soldering.