desoldering double sided boards

[daz]

Can anyone school me on this? I have run into some these that are extraordinarily hard to desolder. I have sever wick sizes and a desoldering tool (sucker) and some of these are just impossible to get out when you are trying to remove things with multiple joints like pots and jacks. Especially the gear with surface components which tend to be space saving and the pots and jacks have small holes that are even tougher. I tried very small wick sizes and the desoldering tool and often it's impossible. I often end up cutting the pot or jack up to separate the legs so they can come out one at a time. But there are several situations where i need to keep them intact which makes it seem impossible. Any tips? Thanks !

[Jazz P Bass]

You hit the nail on the head with 'hole size'.

I don't know where some of these layout guys went to school, but they should go back.

Then again the last item on a lot of amps is 'repairability'.

Anywho, sometimes it helps if you can wiggle the component before the solder rehardens.

Also, a heat gun can help for the final removal.

I am not a big fan of solder wick. You end up with too much heat applied to the pad.

[52 Bill]

Chip Qwik is a good way to get all of the old solder removed without too much trouble. It's meant for use with surface mount stuff, but the same principal applies to thru hole work, reduce the melting point of the solder to make removal easier.

Or you could invest in a good vacuum desoldering station.

[daz]

You hit the nail on the head with 'hole size'.

I don't know where some of these layout guys went to school, but they should go back.

Then again the last item on a lot of amps is 'repairability'.

Anywho, sometimes it helps if you can wiggle the component before the solder rehardens.

Also, a heat gun can help for the final removal.

I am not a big fan of solder wick. You end up with too much heat applied to the pad.

Yeah, but thats the only thing that works sometimes. can't get the desoldering sucker on it fast enough when the hole is so small that it hardens super quick once the iron is removed. And yes, the pad/trace often pulls up and i end up with wires all over the place. But with these tiny surface mount components the traces are so small and often hard to see where they go when the go under things that you don't even see where they terminate. And even if you do theres so little area to solder a wire to. It's just nearly impossible. I guess i'm not alone. I was thinking i may be missing something. But I've tried everything i can think of including rocking them as you mentioned. I'll hit a joint while putting pressure on the jack or pot so that it pulls out a tad and let go when it hardens. then do the same to each leg trying to gradually rock it out. But god what a pain, and the trace/pad often gets screwed there too.

You guys who make a living off this stuff gotta be worried ! It's getting more and more that everything is repairable via board replacement only, making most things throw away and buy a new one items.

[daz]

Chip Qwik is a good way to get all of the old solder removed without too much trouble. It's meant for use with surface mount stuff, but the same principal applies to thru hole work, reduce the melting point of the solder to make removal easier.

Or you could invest in a good vacuum desoldering station.

never heard of that but i'll look into it, thanks.

[daz]

Wow, that chip qwik looks great ! heres a good youtube video for anyone reading this who's in the same boat. I believe this stuff is indispensable for my purpose. SMD Removal using a Chip Quik kit - YouTube

[Mick Bailey]

As mentioned above, Chipquik is one answer. I've found the lead version to be much better in all situations than the lead-free version; it flows better and alloys more readily with the parent metal. The thing that it offers is to give increased working time at a lower temperature and a wider plastic phase to the molten metal. I've got a vacuum desolder station but even that won't remove the solder from a pin that's closely sized to the through-hole. An even bigger problem is where a component leg is a press-fit into the hole.

My technique is to apply Chipquik to alloy with the visible solder (on both sides of the board if it's possible) and then remove this with your normal desoldering method; braid, pump or machine. This is done at a much lower temperature than regular soldering, so you need a temperature regulated iron, or solder station. I then reapply chipquik - effectively to re-solder each component leg. Removing the initial alloy gives the Chipquik a better chance of getting into the through hole. Now I quickly reheat each joint and remove the component. A tip is to heat the component leg and not the joint and to make sure the solder on both sides of the board has melted.

Sometimes though, the only safe way is to snip the leads. Where the component is more valuable than the board I'll perform surgery on the board to recover the component intact.

[Enzo]

daz, you don't remove the iron then apply the sucker. You heat the hole until solder melts, then put the sucker right down on the iron tip over the hole. Leave the iron on the hole to keep it melts WHILE the suction removes the molten metal.



I know guys swear by it, but I just HATE wick. If you have an empty hole with only solder in it, I suppose it might clear the hole OK, but I never liked it. My iron has to not only heat up the solder in the hole, but also has to heat up the wick and heat the hole THROUGH the wick. Put all that on a heavy or wide trace with a larger component in the hole and it can be very tough to clear with wick.

Guys like the squeezy bulbs, but I find them ineffective. For solder extractors, I like the cylindrical cock it and press the button solder pumps. For me I prefer the metal ones with a screw off end over the plastic ones that snap apart. These things I think offer much higher suction impulse than the squeezers.

But really, nothing works as well as a desoldering station.


Technique matters, even with my desoldering station. If I have as pot to extract, I will be wiggling it back and forth as I suck solder, otherwise they often sweat themselves to the side of a hole. Same thing with an 11 or 15 leg power IC. Wiggle as I suck each leg dry.

Hole doesn;t clear? Make sure to apply fresh solder. A hole is much easier to clear when it is full of solder than when half the solder is gone.


I imagine chip qwick would work, I never tried it for that. My Pace sucker seems to cover that pretty well.


desoldering stations are getting less expensive, but lets say I spend $500 on one. Sounds like a lot. If I repair one amp a day using it in some way, assuming 50 weeks of 5 days, that adds $2 to each repair for one year. And consider that I can suck a pot off a board or a 64 pin IC of a board in a very short time, versus all the fussing and fuming and repair of torn traces of doing it the hard way, and considering that my time sells for a dollar a minute, if it saves me two minutes each time, I just paid for it. Of course other than replacing tips regularly - as with any iron - this same $500 machine has been on the corner of my bench for 25 years now. So far that is about $20 a year, or about 8 cents off each repair. And that is assuming only one per day.

[salvarsan]

But really, nothing works as well as a desoldering station.

Ditto.

For large solder chunks (usually chassis grounds and guitar pickup frames), I add heat from a 100 watt iron for more thermal mass.

I cannibalized a few junk Pace MBT 200's into a good one and run its vacuum generator on compressed air. Pace's motorized vacuum pumps are barely adequate when new.

Don't buy a used station until you've checked the price of replacement parts like tips, extractors, and repair parts. A station without an extractor tool is no bargain.

[Rhodesplyr]

Vacuum desoldering works best for me on the occasions when I have to work on through-hole plated boards. Fortunately, most of my work is on older gear. Through-hole plated boards make for stronger solder joints, but the downside is the difficulty of repair. As the OP said, if you have a component with a wide, flat lead, like a pot or a voltage regulator, and the edges are tight against the sides of the hole, it's virtually impossible to get the solder out that's between the lead and the pad. Rocking sometimes works, but other times, you just have to sacrifice that component to keep from damaging the board.

I think my Anatek ESR meter is made with a through-plated PCB, and they warn you in the instructions to make sure you've got components in the right hole before soldering.

[Mark Black]

As for a cost effective vacuum desoldering station, some years back I got one of these and it has worked very well:
Hakko 808-KIT Desoldering Gun Kit | TEquipment.NET

Vacuum is very good and heat more than adequate for most operations. Parts & tips seem to still be readily available and this model has been sold for many years.

The only thing that gives it trouble is plated through-holes in heavy ground planes, where I might have to "help" it with another iron due to rapid heat wicking. Pots, IC's, and pretty much any other normal parts on typical traces are a breeze even with through-hole plating.

Gonna have to get me some Chip-Quik to try on the nastiest of the heavy ground plane jobs (think big power supply filter caps in pro audio amps with one-side-only access).

[drewl]

Even though I'm spoiled with killer desoldering equipment at work, if you are replacing a bad part it is still alot easier to clip the part out, remove the piece that goes through the board and then clean the hole for the new part to be soldered in.

Some boards I work with with massive RF shielded pads, after removing the bad part, I have to place my soldereing iron tip on one side of the board and suck the solder out from the other side with a desoldering gun.
PC board vises are great for this and relatively inexpensive.

[rf7]

Here's a trick: When using wick on stubborn holes, I put liquid solder flux on the hole and it helps the hard to get solder to flow into the wick.

[The Dude]

I've got a Pace station on the bench, but if you don't tech for a living and/or can't afford such a thing, the spring loaded solder suckers work pretty well......for the price.

[Mick Bailey]

Here's a trick: When using wick on stubborn holes, I put liquid solder flux on the hole and it helps the hard to get solder to flow into the wick.

I have my flux by me all the time - it really improves desoldering on DS boards even with a desolder station. Indispensible with wick.