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Desoldering how to?

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Andrew Johnston25/01/2020 15:59:13
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5110 forum posts
594 photos
Posted by Nicholas Farr on 24/01/2020 15:33:42:

Hi Andrew, this one hot enough! ?

It's not just temperature but the amount of heat. I'd guess that one is 250W so plenty big enough! I've used one that size once to solder copper busbars, carrying several hundred amps, in an inverter.

I've recently acquired it's baby brother, a Weller 100W iron from an ex-colleague who was closing down his acoustics and vibration consultancy.

Andrew

Grizzly bear26/01/2020 17:02:37
214 forum posts
6 photos

Ian, Have you sorted your desoldering?

If you are still pondering, I could do it. Cost? Postage only.

The only downside, it could get lost on its' journey

. Bear..

Baldric26/01/2020 17:21:39
149 forum posts
11 photos
Posted by Simon Williams 3 on 24/01/2020 16:34:00:

Two tricks you need to know with a sucker, firstly (exactly as Andrew says) use a hot iron and add solder first.

Then put a Hellerman sleeve (butyl sleeve) over the end of the sucker nozzle so it seals to the plated through hole. A bit of silicon tube would be even better,

Using a Hellerman sleeve is exactly what I used to use with a solder sucker when repairing PCBs/cables or anything else in a TV studio. If the pin is hard against one side of the hole sometimes I would have to heat it, force the pin away from the edge, then when cool release the pin.

Baldric

Ian Parkin26/01/2020 18:17:16
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704 forum posts
181 photos

GB

Yes i did manage it eventually

I’ve been messing about with electronics since the early 70’s full subscriber to practical electronics for all the 70’s then on to a degree in electrical and electronic eng

i’ve got irons from 10watts to 200 watts

but suddenly i find modern boards so difficult with smc and double sided boards...I never thought I’d get to the stage where i cant read a resistor colour code now i can hardly see them (smc that is)

anyway the switches were slightly strange in construction (flipped from side to side) the tracks were extremely fine <0.5mm and where the pad was connected to a large mass on one side it was very difficult getting heat in to both sides at once

I’d destroyed the switches but carefully metering the contacts enabled me to trace the wiring sense of them and soldered in flying leads along to panel mounted switches

after all this the circuit still works (surprise)

Its a stepper motor driver controller for a camera slide rail I’ve made up fro video use...but the way those switches are mounted and used made it impossible to mount in a case.

Grizzly bear26/01/2020 18:40:03
214 forum posts
6 photos

Hi Ian,

Congratulations, very satisfying I'm sure.

My interest has been hobby oriented, I too enjoyed the electronic magazines, especially 'Television' the follow-on from Practical Television.

Now, the www. is so useful for gathering information.

Regards, Bear..

John Haine26/01/2020 20:27:50
2833 forum posts
141 photos

Possibly a bit late, but I used to have a very nice tool from Maplin which was a combined iron and sucker. Until the element went it worked very well, but when it did go Maplin had gone too and I couldn't get a spare (even had they stocked 'em).

noel shelley26/01/2020 20:28:52
72 forum posts

Sorry to come in late, Before I'm shot down in flames, I know it can be messy But I have used an airline blow gun with good results. The blow was far more powerful than the suck. Noel

Kiwi Bloke27/01/2020 02:03:48
297 forum posts
1 photos

Interesting thread...

In retrospect, I realise that I have found de-soldering modern equipment to be more of a challenge than it used to be - even allowing for component density, failing eyes, etc. The comments above to first add solder was a lightbulb moment, I think. I customarily use a well-loaded iron to de-solder. I thought it made things easier because it provided better thermal contact, but I bet it's a lot to do with adding lead to the new-fangled lead-free solder joint. I don't use lead-free solder, know that it doesn't flow as well as 60-40 and a repair man I know says the move to lead-free was the stupidest thing ever forced upon manufacturers. The joints are prone to failure, tin whiskers grow between tracks and components and (elderly) joints just seem to fall apart. After a dose of lead into the joint, solder suckers work pretty well.

So, the message is: add solder first, but use good old 60-40 lead-containing solder!

Nicholas Farr27/01/2020 07:31:26
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2067 forum posts
995 photos

Hi Andrew, it is indeed a 250W made by Solon. I also have my fathers 65W one of the same make and style, which is more practical for many jobs and also a variable temperature solder station and a 15W Antex Precision, a Weller Universal, a Black & Decker one in a similar vein to the Weller, and a 12V 17W one that can be clipped onto a battery or suitable 12V supply, plus about three of my fathers that have to be heated up with a flame. The B&D and the 12V one, along with the flame heated ones, very rarely get used now though.

Regards Nick.

Martin Kyte27/01/2020 09:20:47
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1570 forum posts
24 photos

Professionally I use desoldering braid more than I do solder suckers.

Braid

Particularly on delicate tracks/components. The other usefull function for braid is to remove old solder which can get somewhat pasty making it difficult to desolder stuff. A cycle of remeval with braid and then resoldering with new solder often results in a 'fluid joint' which is more ameanable to desoldering by your preferred method.

When removing 'dead' components do cut away whatever you can with side cutters to allow pins to be removed one at a time is possible.

regards Martin

Danny M2Z27/01/2020 10:04:20
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784 forum posts
282 photos

To desolder a through hole component a hollow tipped soldering iron with a vacuum pump is pretty handy.

Many years ago I attended a RAAF course for High Reliability Soldering Instructors. This was based on NASA best practices.

Imagine my amusement when some of the solder joints that the class had made were projected onto a large screen, microscope photos magnified to over 2m across and the class were invited to inspect our work and offer a critique.

This was very educational and as many of the class were working on aircraft instrumentation it was vital that our work was as perfect as humanly possible.

One thing that I did learn was that many (cheap) commercial solder suckers (especially with a Teflon tip) can generate a large ESD (Electrostatic Discharge) pulse if they have a plastic body so nowadays look for an ESD safe solder sucker if that's what you use

As for soldering braid, it;s useful to remove solder from the base of a 1950's valve base and indeed I still have a few reels which are useful for repairing model aircraft fuel tanks but for printed circuit boards it's only good for lifting tracks.

After I left the old job I managed to find a decent soldering station at a mil surplus auction along with lots of tips.

I paid a lot (lot) less than the original price so pretty happy.

soldering station.jpg

* Danny M *

Martin Kyte27/01/2020 10:10:28
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1570 forum posts
24 photos

"As for soldering braid, it;s useful to remove solder from the base of a 1950's valve base and indeed I still have a few reels which are useful for repairing model aircraft fuel tanks but for printed circuit boards it's only good for lifting tracks."

The avoidance of lifting tracks is the precise reason I use it.

regards Martin

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