Desoldering double-sided PCBs.

[newfish]

Hi All,

Whilst de-bugging an Echobase, I've rather stupidly burned through/ lifted off a couple of solder pads - to a point where they can not be glued back in place (I've done this before, and these really are beyond fudging).

I *thought* I had de-soldering down to a 'T', but clearly have much left to learn.

I tried a de-solder pump, a de-soldering iron, and some skinny de-solder braid - and all three methods left a tiny amount of solder mid-hole.

FWIW, the quality of the EB PCB is not in question - my pre-caffeine ham-fistedness is the only culprit.

Does anyone have any tips or advice to help avoid future mistakes?
(I'll also be getting plenty of practice taking the components off the now-spoiled board)

[Hides-His-Eyes]

Leave some solder in the hole, melt it again when you want to put something in there is the best I've managed

[Scruffie]

Leave some solder in the hole, melt it again when you want to put something in there is the best I've managed

I'd go with that, if it doesn't come out cleanly with the first Shot, just forget it and heat it as you push the component in.

I suppose you could also just heat it with wire in and pull the wire back out again to clear it, might work.

[phector2004]

Biggest PITA ever... I think what I ended up doing the first time that happened was sticking a stripped solid core wire in as I melted the solder, putting desoldering braid on the joint, and pulling the wire out as I heated everything. But it was very inefficient, so the next time I just melted the solder, pushed the component in, and properly soldered it.

[newfish]

Cheers guys.

I suppose being a little more careful next time would help too.   

[chi_boy]

I use a de-soldering iron too and have found that it works best with a full pad of solder to suck on.  If I had that problem, and I have in the past, I put more solder on with a regular iron so that the pad looked full, or like the componant was still soldered in.  The de-soldering iron then seems to work best.

[.Mike]

I tried a de-solder pump, a de-soldering iron, and some skinny de-solder braid - and all three methods left a tiny amount of solder mid-hole.

Just curious... what kind of desoldering braid did you use?

I have found that not all braid is created equal. I use Mouser # 1811-5F, and it is excellent.

When I've desoldered from double-sided boards, it literally sucks all the solder out of the hole, making the part fall out, or, worst-case, requires a very gentle tug on the part while still hot to remove the part. A quick touch with the braid afterward cleans up any remaining solder very nicely.

Mike

[G. Hoffman]

Re-tin your iron tip, a bit heavier than usual, then use the solder-braid.  On PCB's, I MUCH prefer solder-braid to anything else.  Use the #2 size so you don't have to put so much heat into the system.  Use a hot-ish iron, and get in and out as quickly as you can.  If it doesn't go in one shot, let it cool off for a few moments, and then give it another go making sure your tip is re-tinned.  It might also be a good idea to add a touch of flux to help things flow.


That's what has worked for me.  Hopefully PRR or R.G. will come in and explain the right way to do it!


Gabriel

[newfish]

I tried a de-solder pump, a de-soldering iron, and some skinny de-solder braid - and all three methods left a tiny amount of solder mid-hole.

Just curious... what kind of desoldering braid did you use?

I have found that not all braid is created equal. I use Mouser # 1811-5F, and it is excellent.

When I've desoldered from double-sided boards, it literally sucks all the solder out of the hole, making the part fall out, or, worst-case, requires a very gentle tug on the part while still hot to remove the part. A quick touch with the braid afterward cleans up any remaining solder very nicely.

Mike

Yes - I used to have some 'Servisol' branded braid, and it was excellent.
I currently have something a bit 'less' I picked up in Maplins, as I was doing a quick (hasty?) re-stock.

This is what I think I *should* have used...

http://www.wiresandstuff.com/tools/servisol-soldamop-no-clean-desolder-braid-wick-sucker.html

Cheers!

[merlinb]

Does anyone have any tips or advice to help avoid future mistakes?

Easy. Modern boards use lead-free solder, which does not always allow you to suck out the last drop from the hole. Simply re-fill the hole with leaded solder and you should then be able to clear the hole easily.

[Hides-His-Eyes]

Does anyone have any tips or advice to help avoid future mistakes?

Easy. Modern boards use lead-free solder, which does not always allow you to suck out the last drop from the hole. Simply re-fill the hole with leaded solder and you should then be able to clear the hole easily.

Just for info, if you're repairing commercially this is "illegal" (against the rules, anyway!) here in the EU.

[newfish]

Does anyone have any tips or advice to help avoid future mistakes?

Easy. Modern boards use lead-free solder, which does not always allow you to suck out the last drop from the hole. Simply re-fill the hole with leaded solder and you should then be able to clear the hole easily.

Just for info, if you're repairing commercially this is "illegal" (against the rules, anyway!) here in the EU.

Ah.  I still have a roll of leaded solder, and did try re-applying and removing solder.

This is not a commercial build / fix - it's me in my 'Shed of Rock'.   

[Ice-9]

The way I do this and for me it's 100% problem free is to heat the solder with the iron from the component side of the board and with small tweezers lift one side of a resistor, which leaves the resistor standing on its end, then heat the other end (still component pcb side) and remove the resistor completely. This of course leaves the hole full of solder you can leave it like this and put in a new component the same way or at this point use desolder braid to remove the solder and leaving the hole.

Caps exactly the same but usually from the bottom of the pcb I apply the iron and with caps you can usually apply heat to both connections at the same time.

Ic's are a little more tricky, if its an ic that is faulty and its junk then i might use a blade to cut the pins right at the plastic ic eclosure which just leaves the IC pins in the PCB which i can remove one at a time with the iron and tweezers. If i need to save the IC then i will use desolder braid to remove as much solder as possible then try and bit by bit free each pin.

[newfish]

The way I do this and for me it's 100% problem free is to heat the solder with the iron from the component side of the board and with small tweezers lift one side of a resistor, which leaves the resistor standing on its end, then heat the other end (still component pcb side) and remove the resistor completely. This of course leaves the hole full of solder you can leave it like this and put in a new component the same way or at this point use desolder braid to remove the solder and leaving the hole.

Caps exactly the same but usually from the bottom of the pcb I apply the iron and with caps you can usually apply heat to both connections at the same time.

Ic's are a little more tricky, if its an ic that is faulty and its junk then i might use a blade to cut the pins right at the plastic ic eclosure which just leaves the IC pins in the PCB which i can remove one at a time with the iron and tweezers. If i need to save the IC then i will use desolder braid to remove as much solder as possible then try and bit by bit free each pin.

Or be wise enough to use sockets when first building...

I wouldn't like to take ICs off a commercially-manufactured board...

[merlinb]

Just for info, if you're repairing commercially this is "illegal" (against the rules, anyway!) here in the EU.

Only if you want to sell the PCB commercially.