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Old Mar 17, 2005, 12:52 AM
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Manila, Philippines
Joined Jul 2004
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How do you clean up those 20 years old IC's pin

Guys: How do you clean up those old ICs pins. to make it solderable, beside using a files and sandpaper......I have a bunch of 4N35 opto-coupler, its difficult to solder...its very difficult to clean those individual pin one by one....I was thinking of just droping the whole ICs in a Special Solution to clean up those pins?

I just wonder what kind of Solution should I use?
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Old Mar 17, 2005, 01:40 AM
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Joined Mar 2005
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solder with flux? though you prolly knew that thats my guess, ive never found a surface i couldnt solder
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Old Mar 17, 2005, 01:46 AM
"MAYONNAISE"
Acetronics's Avatar
Le Treport, France
Joined Jun 2004
1,408 Posts
Hi, lazy-b

Many solutions from the designer's drawer:
1) an old secretary's ink rubber ( for it's Remington's faults )
2) a fiber glass eraser pen
3) a special eraser to clean copper on PCB boards before hand design

from your favourite car painter
very fine grain ( 400 or more ) emery sheets or polishing paper

Regards
Alain
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Old Mar 17, 2005, 02:06 AM
Registered User
Smolensk, Russian Federation
Joined Aug 2004
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You can try Acetilsolicilum acid (Tablet of Aspirin). Plase pins on it and heat with soldering iron. But good ventilation required, bad smell
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Old Mar 17, 2005, 07:29 AM
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die fliedermaus's Avatar
Kansas
Joined Jul 2002
539 Posts
The aspirin trick does work.
WHOOOOOOOOOOOEEEeeeeeeee what a stink though.
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Old Mar 20, 2005, 09:48 PM
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Manila, Philippines
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Guys.....Thanks for all your advice.. I should try ASPIRIN next time.....Its much easier than filing or sandpaper.
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Old Mar 21, 2005, 08:56 PM
Dimension Engineering
Akron, Ohio
Joined Jan 2002
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Before you do that, try changing the solder you're using. Some fluxes are relatively whimpy.

I'm very partial to Kester 44. Its a little bit more than the crap you find at radio shack, but worth every penny.
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Old Mar 24, 2005, 08:34 PM
Too lazy to repair!
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Round Rock, Tx
Joined Oct 2002
3,396 Posts
What is coating the pins? Is it black?

Way back in the day, when I used to repair computers for a living, some chips pins would turn black over time. If they were soldered in place this was not a problem. But back then, many computer boards used sockets. This would cause connection problems. The thing is only certain manufacturers chips would turn black. Usually TI chips were the worst. The thing is that TI used to (maybe still do?) silver plate their pins. The black build up was silver tarnish. Just like your mom's good silver. What we used to do was to take the cips and dip them in a silver cleaner, then dip them in rubbing alcohol, then in hot water. Then we would let them dry. The alcohol would remove any residue from teh silver cleaner. The water would remove the alcohol. The parts would come out nice and shiny and work for several years after that.

But, I got to tell you, silver cleaner doesn't smell very good either.

JOe
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Old Mar 25, 2005, 12:30 AM
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San Carlos, California, United States
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I clean them with the green scrubbing pads in the kitchen section of my supermarket.

Toshi
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Old Mar 28, 2005, 12:58 AM
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Manila, Philippines
Joined Jul 2004
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guys: the pin is not coated by Black, its color is Grey, when I try to Tin it with solder, the solder do not adhere to the pin. the ICs is made by PHILIPS......sometimes its too much work to clean up 40 pcs x 6 pins, thats 240 pin.....I rather buy new one.

next time will try the ASPIRIN or Silver clean as suggested by you guys.

Thanks.

Ellion
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Old Mar 28, 2005, 09:12 AM
York Electronics
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Dallas Tx USA
Joined Apr 1999
2,505 Posts
BTW, the fiberglass spot sanding pen is available from Pro Motocar Products. PH# 1-800-334-2843 or on the web at www.promotorcar.com . This is the same kind of product used be car-guys to clean the coms of the car motors. I use it to cut away PBC paint on boards that are broken and need to be jumpered. It's a very useful product for anyone who solders.

Gary
--
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Old Mar 30, 2005, 10:01 AM
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San Diego Lindberg, California, United States
Joined Jan 2002
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black-->silver oxide

FYI black coloration on a silver plated pin is not an issue. Silver oxide is a good conductor.
I've seen more discoloration of the pins of chips that were placed in the black antistatic foam. Don't know if it a coincidence but my older chips that were left in the black foam seemed to have dirtier looking leads ?

I've seen the funny discoloration, ie splotchy grey/tan color. I though it was just the under plating of the pins. I am not sure, how common it was a long time ago, but pins were often tin (Sn) plated over coppper. If you are really interested you can go to the last few pages of the manufacture's spec sheets and it should list the final finish of the pins and sometimes also the material used in the lead frame. If it is not listed in the back of the spec sheet, you will have to go to the package information catalog of that manufacturer.
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Old Mar 31, 2005, 04:27 PM
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> discoloration of the pins of chips that were placed in the black antistatic foam<

I read somewhere that some of those antistatic foams, especially the older types, were subject to some kind of chemical breakdown that would actually corrode the pins of chips left in them for a long time. -Wayne
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