How do you clean up those 20 years old IC's pin - RC Groups
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Mar 17, 2005, 01:52 AM
Registered User

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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Mar 17, 2005, 02:40 AM
Registered User
solder with flux? though you prolly knew that thats my guess, ive never found a surface i couldnt solder
Mar 17, 2005, 02:46 AM
Acetronics's Avatar
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

Mar 17, 2005, 03:06 AM
Registered User
You can try Acetilsolicilum acid (Tablet of Aspirin). Plase pins on it and heat with soldering iron. But good ventilation required, bad smell
Mar 17, 2005, 08:29 AM
Registered User
die fliedermaus's Avatar
The aspirin trick does work.
WHOOOOOOOOOOOEEEeeeeeeee what a stink though.
Mar 20, 2005, 10:48 PM
Registered User
Guys.....Thanks for all your advice.. I should try ASPIRIN next time.....Its much easier than filing or sandpaper.
Mar 21, 2005, 09:56 PM
Dimension Engineering
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.
Mar 24, 2005, 09:34 PM
Too lazy to repair!
jperch's Avatar
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.

Mar 25, 2005, 01:30 AM
Registered User
I clean them with the green scrubbing pads in the kitchen section of my supermarket.

Mar 28, 2005, 01:58 AM
Registered User
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.


Mar 28, 2005, 10:12 AM
York Electronics
Gary Warner's Avatar
BTW, the fiberglass spot sanding pen is available from Pro Motocar Products. PH# 1-800-334-2843 or on the web at . 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.

Mar 30, 2005, 11:01 AM
Registered User

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.
Mar 31, 2005, 05:27 PM
Registered User
> 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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