thru hole

[goodsguys]

Hi. And thanks for taking the time to read this post.

What is the best way to get solder out of a hole. I am trying to get a new capacitor soldered down onto a circuit board, have got the old one out with some difficulty, now there is a stubborn piece of old solder which has set up camp in the hole and will not shift.

I have tried pushing the leads of the new capacitor in, applying flux to both sides of the hole and ofcourse the obvious desoldering pump but none of these will work. I even took out my soldering bit and used a fine nail, but i think because it is so thin it cannot absorb enough heat and melt the solder. Now i have got a black mark on the circuit board from using too much heat. It seems the board or nearby components are absorbing a lot of the heat into themselves.

Can anyone please advise.

Many thanks. John.

[bobbasrah]

Wrap a paperclip around the end barrel of the iron (or whatever size stiff wire fits the hole, lead from old resitor etc?), get it hot, and let it sink through the hole lowering the iron and wire into the hole, remove quickly and blow through or use solder sucker...

[The Grand Wazoo]

As above, but use a piece of fine but multi-stranded wire - it'll soak up the solder better between the strands.

[Barry]

Melt the solder with an iron, then use the tip of a sharpened lead pencil to push the solder out of the way.

This technique works as well as using a solder sucker.

[pete_mac]

As above, but use a piece of fine but multi-stranded wire - it'll soak up the solder better between the strands.

Solder-wick is another option which works along the same lines - basically a 'wick' of woven/meshed fine copper wire. I had to use a bunch of it on a particularly troublesome PCB just the other day and it worked a treat.

[goodsguys]

Hi. Many thanks for the replies.

Unfortunatly the solder is so stubborn the wick is only removing some surface stuff on the pcb, it is not getting right down into the hole and sucking it up

I like the wire/paper clip suggestions and have tried steel ones but cannot get it hot enough It is touching the solder but not melting it, instead the board is heating up and starting to blacken. I remember years ago someone told me to use brass that if you cannot find a suitable bit for your soldering iron get a brass rod and shave the end down, so am thinking brass is a better conductor of heat. I tried this out, unfortunatly the only brass i have at home is in the form of brass screws. I took out my soldering iron bit and inserted a large brass screw versus a steel screw, the brass melted solder on an old circuit board's solder very quickly, the steel one did nothing even after about two minutes of contact.

Think i might experiment with different metals to see which is the best, will get back to you on that. Perhaps copper?

Many thanks for your suggestions. John.

[Puffin]

get a very small drill bit and drill through it. Drill from the pad side of the board if
one-sided.

[bobbasrah]

Really surprised by your result Mark, as the wire should be roasting on the end of your iron, and should melt solder long before the PCB gets hot.... Or at least it has for me even with the little 15w Antex... Unless the wire cannot physically get in the hole as the wire is too big maybe?

If a trial with some copper wire fares no better (conducts heat faster), Rob's suggestion will have it out in a jiffy.

[Barry]

Why don't you use a solder sucker? Or use a lead pencil pushed into the hole, immediately once you have melted the solder. It has always worked for me.

You could well have difficulties using a wire. Athough you may well be able to push the wire through the hole, because the solder will wet it, when you pull the wire out the melted solder will simply re-fill the hole. Solder won't wet graphite, which is why this technique works

[pete_mac]

Can I also suggest applying a generous amount of fresh solder to the offending hole on the PCB and ensuring it makes its way into the hole, and then using the solder wick? This has worked for me in the past.

[goodsguys]

Hi. I must be doing something wrong .

I picked up a stiff piece of copper wire from a diy store, it was actually a length of mains electrical cable the 3 core type the live and neutral were insulated the earth wire was not so i snipped a few inches of earth wire left the live and neutral untouched, then removed the soldering tip and shoved the wire into the hole, managing to force the tip back in as well, so now the wire is protruding from the iron by about an inch.

Does this sound ok.

Thank you.

[bobbasrah]

Hi. I must be doing something wrong .

I picked up a stiff piece of copper wire from a diy store, it was actually a length of mains electrical cable the 3 core type the live and neutral were insulated the earth wire was not so i snipped a few inches of earth wire left the live and neutral untouched, then removed the soldering tip and shoved the wire into the hole, managing to force the tip back in as well, so now the wire is protruding from the iron by about an inch.

Does this sound ok.

Thank you.

So long as the copper is thinner or the same size as the original lead that was removed, the wire should go through also if enough heat is generated on the end. I recollect reading somewhere that a small sewing needle also works for the same reason as Barry said re propelling pencil, solder does not stick to it. A needle is tapered also...

Have never tried jamming a wire between element and bit, as my Antex bits are too long and too tight a fit for such an arrangement (It would not be near enough to where the heat is greatest on the Antex, but YMMV)

Hand drilling with a small bit as Rob suggested is best if that fails....

[goodsguys]

Many thanks for the replies. It is genuinely appreciated.

Following your instructions Should I remove the soldering bit, wrap the wire around the bit, reinsert back into the iron, heat up then plunge the protruding wire into the blocked hole.
I have tried this Unfortunately the solder is not melting. Might be my iron. I have a weller sp80l 80 watts Don’t know perhaps weller are a crap make or not The wire is not getting hot enough Can you let me know which iron you use Perhaps if I purchase the same make and model as you this might alleviate the problem.
The principal you described sounds good and should work might be my stooped old iron is letting me down.
As an alternative what do you think of irons with a built on desoldering attachment. Are these any good.

Thank you.

[bobbasrah]

Good grief Mark, still at it? I'd have spun a drill bit through it by now as Rob suggested, through sheer impatience....

That type of iron should get plenty hot, especially with 80w up the spout.....
The heat is generated mostly at the front end of the bit from where it tapers down from the main barrel.
From the pic on Amazon the end of the bit looks circular, so wrap the wire tight around the end of the barrel as far forward as you can and twist the wire ends so it grips tight. Cut the wire so that a short length projects clear of the iron to avoid burning anything else when you are pushing the wire into the hole.

Heat the iron up, if the wire is hot enough to melt a bit of solder off the spool onto the end, it will melt what is in the hole.....

[YNWaN]

80W is more powerful than you need, so should be ample. Wet the end of the soldering iron with solder, melt some solder back on to the circuit board (so that the solder conducts the heat to that solder which is in the hole) - suck the whole lot up with the solder sucker - job done (assuming you haven't entirely lifted the tracks by heating it so much with your previous efforts).

[NRG]

Can I also suggest applying a generous amount of fresh solder to the offending hole on the PCB and ensuring it makes its way into the hole, and then using the solder wick? This has worked for me in the past.


This is the method I use and it always works except I use a solder sucker to clear the hole. Be careful of a high wattage iron and leaving the heat on to long, it can lift PCB tracks.