Desoldering braid that won't

[Windmill]

I have some desoldering braid which is supposed to assist in removing solder from circuit boards by using capillary action to wick the solder away from a soldered joint.

It never worked.

Maybe there were some instructions which I should have received (or kept); anyway instead of the solder 'wetting' the copper and spreading along the braid, which is what I assume is supposed to happen, it barely penetrated it at all.

Maybe I needed a much bigger and hotter iron for desoldering than I would use to solder.

Maybe the copper has become too oxidised after long disuse; I don't know how old it was when I got it, and now it's years older.

I've now got some SMD devices to remove/fit (alas) so having braid that works may become important. Apparently the suction tool I used to use on larger components isn't so good at removing solder from these tiny new parts.

Is one supposed to treat the braid in some way? Soak it in a suitable flux? Or just buy some new pre-treated variety ?

[The Other Mike]

I've only ever used it successfully with a 50W Weller temperature controlled iron set to around 270 deg C. Anything piddly like the low thermal mass 15W iron I had to use at the weekend might cause problems on anything but the smallest pad.

Oxidisation won't help but a wipe with some fluxite or other resin type plumbing flux might help, but its dirt cheap to buy - Chemtronics stuff is good quality and available from Farnell and CPC for a couple of quid.

Depending on what you are soldering you might get away with a suction tool maybe with a smaller nozzle. The pads don't always need to be

100% flat and solder free before applying solder paste and the replacement component.

[fred]

In article , Windmill writes

All the stuff I've used is fluxed but I do give it a wipe over with a flux pen immediately before use for better effect (you could equally well dip it in flux).

You don't say what size you're using, I use a temperature controlled iron of 35-40W but anything 25W+ should do the but watch for overheating if not temperature controlled.

Are these just discretes or multipin devices? If simple 2 pin stuff then don't try to desolder them but add a bit more solder to each pad then flip the bit of the iron between each end of the device until the solder at both ends is molten and flip/slide the component off. Then use braid to clean up the pads. For multi leaded devices either use well constrained hot air reflow device or cut all the pins, remove the body then wipe the pins off with the iron and clean up the pads with fluxed braid.

Watch the heat or the pads will lift. If v delicate, (particularly on multipin) wipe the pad in the direction away from the attached track. Practice on some scrap veroboard or similar to get the feel of what you can get away with.

What size are the components, what's the lead pitch if multipin and what size is the braid? Is the braid branded?

[Dave Plowman (News)]

Re-flow the joint with a spot of multicore before using the braid. You also need an iron powerful enough.

[Dave Plowman (News)]

If the normal resistors etc use a bit large enough to do both ends at once, and use tweezers etc to remove. If an IC snip all the leads first and then remove them individually. Clean up with solder braid afterwards. Basically, you aim to avoid damage to the PCB even at the expense of the component being removed.

If you do this a lot get a hot air re-work station - they've come down in price dramatically.

[Jules Richardson]

I've never had much success with the stuff, either. OTOH a *good* solder sucker works well for me (I also had a cheapo plastic-bodied thing that was a freebie. It sucked, but not in the right sense. I took a hammer to it)

cheers

Jules

[Dave Plowman (News)]

If you do a lot, a de-solder station make life easy. If you don't mind a large old unit they can be bought quite reasonably secondhand.

[Derek G.]

If the braid is a new reel snip off couple of cm or so to start with a fresh end.

If it's an old reel first unwind a couple of turns of old oxidised braid.

Either way tin the first cm or so and snip the tinned bit down to half it's length to present a fresh end of newly tinned braid to make a start with.

If removing big components with heavy leads first remove as much solder from the copper pads as you can snipping used braid off as you go.

Then quickly repeat the process before the joints cool. :-)

Derek G.

--

This Looks like Finito Ruperto.

[Mike Tomlinson]

In article , Windmill writes

Braid is totally unsuitable for removing SMD components. You'll need such a hot iron you'll vaporise the component and wreck the pads.

Don't use a solder sucker either, you'll wreck the pads with that too. Use a hot-air gun (a paint stripper may do if you can fashion a nozzle that comes to a point). Heat the component until the solder melts, turn the board over and give the back a tap with a screwdriver handle. The component will fall off leaving you with nice clean pads to solder the replacement to.

[The Natural Philosopher]

If you strip the braiding from coax and have some sort of resin flux you can soak it in, it works well with a hot iron.

But so does a solder pump or heating the joint and banging the PCB on the bench to flick the hot solder off.

So does a matchstick used to crack a drying joint and make it a really dry joint.

[Windmill]

Sounds like great advice, thank you. I'd half forgotten how easy it was to cause a track to lift (it's been years).

Varies. Some filter capacitors, some double diodes, and some tiny multipin stuff. (There are actually two different jobs, which I thought I'd combine to avoid forgetting and relearning).

I'll need to look it up, but ISTR .065

I just went looking for it, and can't find it. Maybe I threw it away in disgust last time!

[Windmill]

May have to buy another. 6W not on, 15W still too small, 150 and 500W way too big.

[Windmill]

Goes against all instinct, for someone who grew up when components were very expensive, but you're clearly correct.

Hopefully it'll be a one-shot job.

[Windmill]

The one I have (or had; where is it anyway? Scratches head) tended to kick back excessively, but removed solder. However I gather that braid may be the only way to remove solder bridges across tiny multi-lead SMD ICs.

In which case I need to get some that can work, and learn how best to use it.

[Windmill]

Solder paste! That may help.

[Windmill]

Saved your advice where I can find it again.

[Windmill]

I know nothing about SMD stuff, really (valve sockets, yes!) but some advice seems to suggest that when "pins" are 0.05 apart, solder bridges can easily appear unless you're very lucky, but can be removed with braid.

Something I'll bear in mind if I have to remove an IC; it sounds like it might be a non-destructive approach.

[Windmill]

So maybe a toothpick/cocktail stick to scrape away solder from the

0.01 (?) gap between traces?

[Dave Plowman (News)]

A good 15 watt like an Antex with a suitable bit would do it - but you might have to wait for it to re-heat between 'hits'.

A 50 watt low voltage temperature controlled is the norm for electronics. If cash is tight, I'd go for a good make secondhand (Weller, Antex) rather than a new cheapie. Spares more easily available.

[Dave Plowman (News)]

I tend to use a small diameter (0.5mm) multicore. But it's not the sort of thing you'll get in Maplin. The standard 1.2mm stuff is way too big. And leaded, of course. Stay well clear of lead free solder.

However, this is for very limited use. If doing much in the way of surface mount repairs, you really need the correct equipment and materials.