Solder braid: width?

I want to solder one TQFP144, but do not have any experience with anything more than DIP40.

This is what I'm planning to do. I will:

  1. apply some tinnol on all the pins on the PCB
  2. remove excess tinnol with dump cloth
  3. place the chip and solder it pin by pin with solder iron

step 3 will certanly solder several pins together which I plan to fix with solder braid. The question is: what width should I buy?

Reply to
aleksa
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Desolder braid risks pulling up pins if you don't keep it fully and uniformly heated.

Hold the board upside down but slanted with the ends of the pins downwards and tease the excess solder away with the tip of the iron, you need enough flux to prevent a skin of oxide forming.

Reply to
ian field

I'm not sure what 'tinnol' is, but assuming it's some kind of liquid flux: Skip step 2. You can readily solder fine pitch parts like that in a puddle of flux. Fine pitch + lots of flux = easy. In fact, the first remedy I would suggest for almost any problem (including bridged pins) is to add flux and reheat it. You can often "pick up" the excess solder with the iron and remove it or redistribute it. With lots of flux, the solder will strongly prefer to stick to the pins rather than itself which can cure the bridge.

If you get braid, make it very fine, and NEVER PULL IT OFF THE BOARD if it resists. If you do, you will remove traces, bend pins, etc. It can help to tin the braid as well, but it will corrode over time.

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Ben Jackson AD7GD

http://www.ben.com/
Reply to
Ben Jackson

Contrary to what Ian and Ben have said (and they're both good guys), when I have to do this I use the following procedure:

  1. Locate the part and tack down opposing pins (i.e. pins 1 and 73) so it sits where it belongs.
  2. Solder all the pins on one side. Just drag the iron and make a big glob of solder across all the pins. Think of it as the Golden Gate of solder bridges.
  3. Wick up the solder (carefully) with some honking big (1/8") solder wick. Just lay it sideways on that Golden Gate of solder and suck it all up.

It's fast, it's easy, I'm up to about a dozen parts on various boards now, and I've never had a problem with it.

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Tim Wescott
Wescott Design Services
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Reply to
Tim Wescott

Hi,

I would not recommend using solder braid. Please have a look at the video at

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for a reliable technique for had soldering TQFPs.

If you don't have a "reservoir tip" for your iron, you can just use a broad chisel tip.

Kind regards, Anthony Burch

Reply to
Tony Burch

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'tinnol' =3D 'solder wire'.

What is liquid flux? SMD solder paste? Schukat has it, 15EUR for only 10ml of paste.

Maybe it is possible to place the braid across all the pins (min 3cm), heat the whole braid and it will pick up all the solder at once? If the braid is enough heated, it won't break the traces.

BTW, the minimum braid width at Schukat is 0.5mm, max 2mm.

Reply to
aleksa

For some alternative videos and tutorials (including using braid) that don't require a "full membership," interested parties may wish to surf on over to

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Disclaimer: I have no association with Sparkfun other than as a satisfied customer.

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Rich Webb     Norfolk, VA
Reply to
Rich Webb

If you make a mistake and have a less-capable iron, it's easy to end up with the solder wick attached to so much thermal mass you can't remove it.

I basically do your steps 1, 2 except I use a more moderate amount of solder in 2. I end up with small groups of pins bridged but not the whole lot.

And for the OP, liquid flux is not solder paste or solder. It's a substance that cleans the pins and pads and makes it easier for solder to "wet". Make sure you get some designed for electronics, not plumbing. And if you can, choose water soluble.

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Ben Jackson AD7GD

http://www.ben.com/
Reply to
Ben Jackson

In message , Tim Wescott writes

You and me both, in fact I've used this technique to rework stuff at home on plenty of occasions now, the only slight difference is that I apply a little pressure to the chip package so the pins are pushed gently onto the pads whilst I solder them on.

I've also used the puddle of solder to remove chips, using a sewing needle apply a little leverage between the chip body and board, drag the puddle of solder along the legs away from the needle, move needle to another corner, rinse and repeat. A little practice and a few cycles of this will remove chips quite easily with no board damage. Clean up with wick and flux remover once the chip is off before you attempt to replace the chip.

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Clint Sharp
Reply to
Clint Sharp

I find it very very interesting that NO ONE is talking about the cursed Lead-free solder !!! "Long-Live eutectic 65/37"

Yukio YANO

Reply to
Yukio YANO

sorry "63/37 tin/lead"

Reply to
Yukio YANO

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