Unsoldering from double sided PCBs?

[Axtman]

What is the trick to unsoldering from double sided printed circuit boards? Thanks!

[Tom Phillips]

What is the trick to unsoldering from double sided printed circuit boards? Thanks!

You learn to apply the proper amount of heat to the joint such that the solder melts all the way through to the other side. The part lead can be pulled out while the solder is liquid and then the remaining solder can be sucked or wicked though the hole. Multi lead parts can be very difficult to remove intact. One trick for that situation is to cut out the part then remove the individual leads one at a time. The process requires good soldering equipment and practiced skill to prevent damage to the board.

I think that you can find demonstrations on you tube.

Tom

[Jazz P Bass]

Skill. Experience. Technique. Proper equipment.
There is no 'trick'.
A good 'pencil' soldering iron is a must.
For removing the solder I use a solder pump (sucker)
Desoldering Pump 370-030
The component that you are trying to remove has a lot to do with it.
Big leads tend to remove the heat from the iron tip.
IC's can be a pain to get all of the solder out of the hole.
Some tech's use a braided solder wick to get the last bit out, although the extra time of applied heat can ruin the copper pads.

[1ampman]

+1 ..... Pencil iron with adjustable heat. Solder sucker and do everything you can do to save the circuit board. Growing a 3rd arm is recommended.

[olddawg]

I always used a Pace vacuum desoldering station with a foot control. But that's kind of expensive if you don't do a lot of work. It my be more practical to just cut the leads off of defective parts to heat and remove the leads one at a time. Flux helps. A good Exacto type knife is good fore cutting leads off of ICs. I would suggest practicing on junk boards.

[52 Bill]

And the use of a low temp solder additive like Chip Quik will make removal easier as well.

[philbo]

It depends on what you're unsoldering. I assume you're trying to unsolder thru-hole parts...

If it's a large cap, very often it will have one lead connected to one or more ground plane layers inside the board, which suck heat away from the lead as fast as you can apply it.

One trick is to use two irons at once, one topside and the other bottomside.
Another trick is to heat the whole board (in an electric oven) to 150 deg F or so (uncomfortably hot to the touch, but won't burn you if you handle it gingerly - - be careful; you don't want to melt any plastic parts or wire insulation), then pull it out and unsolder while it's still hot (so you need less additional heat to get to the solder melt temperature).

If it's a leaded part (resistor/diode/small cap/IC/transistor), cut the leads off the old part right next to the part itself, leaving legs in the board that can then be individually desoldered. (If you need to save the part, it gets harder. )

[Mark Hammer]

Unsoldering chips from a double-sided board is several orders of magnitude more annoying than unsoldering discrete components.

And yes, philbo is absolutely spot on regarding the way in which ground planes impede the process. Which raises the question of whether one is simply "harvesting" components from a no-longer-needed double-sided board or repairing/swapping. If the board is destined for the wastebin and there are components worth removing and saving, then one simply cuts or dremels out a gap between the component and the ground plane so that the heat is contained, rather than sinked off.

I always find it helps to melt a little additional solder onto the joint, kind of like a running start. As well, I cannot recommend highly enough use of solder wick with some liquid flux rubbed on it. The flux greatly enhances the solder wick's action. And, much like the way ground planes can reduce iron-heat efficiency, use of oversized solder wick is contr-indicated. Narrower gauge stuff can be very handy for getting into tight spaces and confining/focussing the heat.

[paleeman]

This tool is very helpful. One of the few desoldering guns, that really work. (And won't empty your pocket )

DENON INSTRUMENTS - SC7000Z - DESOLDERING GUN

[guitardad]

on a budget? This place is pretty friendly and their stuff actually works. I've had their DLX Hot air system for 5 years now, and two Temp Controlled solder stations.

Through-Hole Suction & Desoldering Stations | Circuit Specialists

plus you get free stuff

[T9c]

Yeah, I wish I'd seen them before I went and spent a wad on a Hakko desoldering iron-but is still a Godsend! I did find them when I needed a hot air rework station and triple reg. pwr supply, though. The equipment they sell is good and reasonably priced, but free stuff you say? What'd you get?

on a budget? This place is pretty friendly and their stuff actually works. I've had their DLX Hot air system for 5 years now, and two Temp Controlled solder stations.

Through-Hole Suction & Desoldering Stations | Circuit Specialists

plus you get free stuff

[booj]

Pre-heat the board with a heat gun