Help! Solder that doesn't melt

UberFreak

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Hi

I'm trying to revive an A500+ that went through a nasty battery leak.
It was stored vertically, so the acid's trail of carnage is long :(

Anyway, had to do some serious cleaning & replace a few sockets that were eaten alive, but one thing I cannot do, so need some advice!

One IC's legs (to the left of the battery) have been corroded to a point that the solder will not melt.
New solder will not stick to it either, so I'm a bit lost on what to try next!

Any ideas?
 

UberFreak

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I'll take some pics tomorrow.
I've seen the effect acid has on solder before - it becomes dull in color & doesnt respond to heat (at least not heat generated by a solder iron).
 

rkauer

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Things to do:

-Neutralize the corrosion with some lemon juice;

-Sand the leftover of the pin so the contact is shining again;

- Snap a replacement pin from a dead or useless chip and solder it to the remains of the broken pin;

-Done
 

Merlin

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@ Uberfreak

I would try etching the affected area with a solution of hot citric acid (lemon juice). Citric acid is used quite widely in the electroplating industry for metal brightening and remving stubborn deposits. Make a hot lemon juice solution and dab it on with a cotton bud, to see if it has any effect.

I saw Citric Acid used at BNFL in Preston on some magnesium/aluminium alloy nuclear fuel containers after they had been machined (I had developed a special soluble cutting fluid for Shell intended for the machine tools at BNFL that was resistant to splitting from the magnesium making the water hard, and I was running trials there) and afterwards, they came out super shiny, almost as if they had been chromed!

Lemon juice is the chosen weapon to neutralise the crud left behind when the battery leaked and lots of members on here have had success with it.

I am a former industrial chemist that developed products for metalworking and other industries, so rest assured that it's safe to use.
 

r0jaws

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That is so convincing I almost wish I had some battery crud to clean up! :LOL:
 

UberFreak

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Thanks for all the replies!

This board has already gone through several cycles of massive lemon-juicing :LOL:
I'll try hot lemon juice & see if that makes any difference though.
I want to remove the chip intact, no cutting of legs or any other mutilation! :D
 

FOL

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Thanks for all the replies!

This board has already gone through several cycles of massive lemon-juicing :LOL:
I'll try hot lemon juice & see if that makes any difference though.
I want to remove the chip intact, no cutting of legs or any other mutilation! :D

What about resoldering it. I find that being able to mix new with old solder, can help in some situations.
 

d0pefish

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I'd recommend you grab some flux. I prefer the no-clean type, in a pen - example:
http://uk.farnell.com/circuitworks/cw8100/dispensing-pen-no-clean-flux/dp/130692

The flux is an acid and a soldering aid that removes impurities and tarnishing from the metal, and helps the solder flow onto the surface. "No-clean" implies that you don't need to remove the flux after use, and it won't corrode or eat anything if left.

I'd also look on eBay for a fibreglass pen. These are great for rubbing PCB traces, cleaning card edge connectors, and in your case would be ideal for polishing up the legs of any ICs. :)

You won't spend more than a tenner for both of these tools (y)
 

UberFreak

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I'll try with flux (have to buy some).
As for resoldering or using desoldering braid, thats exactly my problem - the old solder would not melt, and fresh solder does not stick to the old one, it just slides off! :mad:
 
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