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Desoldering Guide
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Welcome to the EPE Online |
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| De-soldering is
required when electronic components need to be removed from a circuit, usually because
they are faulty. It may sometimes be necessary during testing or assembly, if a wrong part
has been fitted or a modification has to be made. In the field, it's not uncommon for
faulty components to be swapped out, or poor joints (perhaps "dry" joints) to
need re-making properly, months or years after manufacture. Experienced engineers can
often diagnose a particular faulty joint immediately, because they may have seen the same
problem on similar equipment before, especially if it has a "reputation". A
proper desoldering technique can soon be acquired with practice - all you need to do is
buy some scrap boards to have a go with, and desolder to your heart's content! The photo sequence below illustrates the basic steps for desoldering a printed circuit board, in order to remove a faulty part. Both a desoldering pump as well as desolder braid are illustrated. Some real-life examples of poor soldering are shown too, in my Black Museum of Bad Soldering! Remember that "Practice-makes-Perfect", and in the long run it costs less to get it right than it does to get it wrong! |
Enjoy! -- Alan Winstanley. |
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The two solder joints to be desoldered, to enable a faulty component to be removed. |
| If using a desoldering pump, apply the iron first to melt the solder (1-2 seconds). Ensure the pump is 'primed' and ready to go... |
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The nozzle of the desoldering pump is applied to the molten solder and the spring-loaded plunger is then released, drawing the solder up into the pump. Repeat if needed. |
| The first joint, now desoldered. The second joint will be desoldered using braid... |
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Select a suitable width of braid, and press it down onto the COLD joint using the hot tip of the iron. |
| Molten solder is drawn up by capillary action into the braid. Care not to overheat, or 'drag whiskers' of solder over the board, nor let the braid solidify on the joint! |
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The component dropped out of the board after desoldering. Sometimes, it may need persuading with pliers.... |
| Close-up shot of both joints, now desoldered and ready for the replacement part to be fitted. |
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The Black Museum of Bad Soldering |
| The following are all genuine examples of bad soldering which have not been retouched or reworked in any way. |
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Tenfold excess of solder, and (extreme left) incomplete joint with poor coverage. There is no need to add more solder "for luck". |
| One example of several dry joints found within a commercial PSU adaptor for a computer peripheral. |  |
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Hmmmm... this joint looks somewhat suspect as well... |
| A close-up reveals the terrible standard of soldering (and quality control), with a fracture visible on this ground/ earth joint. |  |
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How not to make a mains voltage soldered joint. This went "dry" and starting arcing, nearly zapping the equipment. It is also a fire hazard. |
| The same mains connection, the wire merely being 'tacked on' with a blob of solder. |
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| All
photos are Copyright © Alan Winstanley 1997. You may download them for personal use, or
for training or educational purposes only. They may not be used on a commercial or
sponsored web site without the prior permission of the author (conditions apply). If you
wish to use these pictures for any commercial reasons, e.g. to enhance any commercial
product, enframe in any external commercial web site or apply for any other commercial
use, you must seek the author's prior approval first (email Alan Winstanley at alan@epemag.demon.co.uk). Very high resolution photos with licence for
reproduction are also available on CD from the author, on payment of a royalty. Please
enquire if you have similar macro photography assignments you would like to be quoted for
and undertaken. For any interested photographers: the photographs were taken by the author using a Minolta X-700 SLR with 50mm Minolta MC manual-focus macro lens at f11-16, coupled to a Minolta Auto 80PX macro ring flash gun. Film was 3M Colour Print 200. The prints were scanned using an HP ScanJet 6250 flatbed scanner, and enhanced using JASC Paintshop Pro 5 with filters, before uploading. |
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