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ArcticMyst Security by Avery

LPC-815 diode woes (desoldering?)

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Mar 10, 2009
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After much poking and prodding, I got my Red diode decanned and out of the sled.

(Why oh WHY do they use so much glue!!??!!)

New problem: The pins are soldered to the old cable (the one i cut).

What's the best way of getting the solder and the cable remnants off?

(I have desoldering wick, not a solder sucker).

What temperature should I set the soldering iron to (what solder do they use, anyway - 60/40?)

I have this horrible thought that if I just put the soldering iron on the solder until it melts then pull the cable off:
a) diode overheats. no more laser.
b) cable remnants come off, solder goes all over diode.

Normally, I'd just put on desoldering wick over the solder, lay the iron on it, and get all of it that way - but the placement of the pins makes this difficult, and besides, I don't want to heat kill the thing.

Anyone who's taken apart these things has got to have run into this, but I don't see any ideas in the forums - what did you all do?

Thanks,
Zithras
 





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Mar 8, 2009
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I've desoldered a combined red/IR diode with the method you describe - it's got 4 pins and two ribbon cables, so it's a lot more difficult. Took me 20 minutes... but the diode lived. These little thingies aren't quite as sensitive as people believe.

However, there are better methods as I've learned:

1. The "solder blob method": put a blob of solder on the tip of your iron, then touch it to the diode pins so that the solder around all of them melts, then pull the ribbon cable off (removing the molten solder at the same time).

It's best to do that before removing the diode from the heatsink.

2. The "snip method": don't desolder, just cut away at cable and solder with a small sidecutter until the pins are free. The advantage is that there is no danger of overheating the diode, but you'd have to be careful to not snap off the pins.
 

Benm

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I think the solder 'blob' method is preferable - and easiest when the diode is still in its sled or otherwise mounted so it stays put during the process.

Try to position the diode with its pins pointing up, melt 60/40 flux core solder connecting all the pins. You should be able to remove a ribbon cable by just lifting it up at this point, taking any molten solder with it upwards.

The danger of thermal damage is very limited this way, and its preferable to work quickly at high temperature over tinkering for minutes at lower temperatures. Make sure to use lead based solder with flux in it, otherwise it will prove quite difficult.
 
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the LPC-815 is one of the easier to desolder.....

i use a pick (like the dentist has) and i stick it underneath the ribbon, in between the two pins that have solder on them, i then apply a little upwards pressure and maintain the pressure while putting a decent sized drop of molten solder on the two pins to melt them at the same time, as soon as they melt the pressure your applying will cause the ribbons to slide right off.......

i like this method cause the ribbon pulls all the solder off of the diode...and your left with very clean pins to work with.

also, it's best to remove the ribbon while it's still in the heatsink......since it is best to do this while it is in a heatsink and putting it in an aixiz is a bit hard with it's ribbon still on...

i've prob done it a few hundred times...this sit the best i think.
 
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a solder sucker works very well and the ribbon cable can be removed with needle nose pliers.
 
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Zithras;

Mohrenberg has a similar technique to the one I use.

I usually use a pick and heat one diode pin at a time.

It requires less heat transfered to the diode.

If you are new to soldering, I would cut off all the excess flat cable.

Then heat the pin while prying off the end of the flat cable.

LarryDFW
 
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I think the pick and iron idea sounds like a winner - especially since I already have some picks I use to clean old coins.

Thanks!
Zithras
 




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