how to clean Burnt PCB and Cleaning IC legs

Discussion in 'General Electronics Chat' started by harrison2015, Apr 29, 2015.

  1. harrison2015

    Thread Starter Member

    Apr 22, 2015
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    What Can I use to clean Burnt PCB? I heard to use a fiberglass pencil
    What Can I use to clean off TTL and CMOS IC legs that are rusted, have battery acid, water damage or other dirt issues?
     
  2. ian field

    Distinguished Member

    Oct 27, 2012
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    In experience with CRT type TVs & monitors, I've had to repair some badly charred PCBs.

    Sometimes its best to file the board right through with a needle file, if this takes out print traces - they have to be carefully reconstructed with tinned copper wire secured back to where the print track is stable.

    When its not that bad, sometimes I can dig out the carbonised bits with a Swan & Morton size 10 scalpel.

    You'll need the fiberglass pencil to remove the varnish from tracks you need to attach the TC wire repairs to.
     
  3. Reloadron

    Active Member

    Jan 15, 2015
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    I do believe Ian has covered it well. For light work I used a toothbrush (also an acid brush) trimmed with stiff bristles and isopropanol. When things get bad exactly as Ian mentions including replacing sections of the board.

    Ron
     
  4. harrison2015

    Thread Starter Member

    Apr 22, 2015
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  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    To clean pcb legs, try a pencil eraser. There is fine abrasive in them. Try to use the white eraser with silica - the red/pink have some amount of iron oxide that may cause trouble with soldering if any dust is left behind. Be sure to support the leg flat against the workbench then polish the inside edge of the leg. Find something to support the inside edge before polishing the outside edge (be extremely careful not to bend the pins).
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
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    Your best bet is immersion in an ultrasonic cleaner with water & detergent, or the kitchen sink and a stiff brush - make sure there's no corrosion debris bridging pins, or any pins eaten through. Then dry it thoroughly. You can get various spray on conformal coatings that should prevent any further corrosion.

    Your fiberglass pencil will just make a mess everywhere if you use it on a rough surface.
     
  7. harrison2015

    Thread Starter Member

    Apr 22, 2015
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    Yes i have tried the white pencil erases to clean contacts

    Polishing the legs using what?
     
  8. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    The fine grit in the pencil eraser allows the pencil eraser to polish the metal. You can also try a more aggressive polishing grit or even scraping with a razor blade, Exacto knife, or even a file. Be careful with a file, the metal pins are very soft and will likely clog the file immediately.
     
  9. Reloadron

    Active Member

    Jan 15, 2015
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    Something else to try is a solution of warm water and baking soda. Cut the bristles of an acid brush down on an angle and use it to scrub the pins and around the ICs. Once the heavy stuff is dissolved then rinse with clean water and finally isopropanol alcohol. Dental pics can also help in dislodging chunks of corrosion. Combine that with GopherT's suggestion and you should be able to remove most surface corrosion and rust.

    Ron
     
  10. harrison2015

    Thread Starter Member

    Apr 22, 2015
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    When I use an acid brush on 70's 80's circuit boards it takes off the "green" circuit board masking. What else can I use to clean boards because a tooth brush and acid brush just take off the green circuit board masking
     
  11. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    @harrison2015 Can you post some pictures from a camera with a decent close-up capability? Use a tripod or steady the camera against something firm to minimize blur. I'd like to see how bad the board and pins are.
     
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