[Elecraft] Cleaning capacitor goop from PC board

[Gary K9GS]

Hello Vic,

I work in electronics manufacturing so cleaning of PCBAs is something I 
know a little bit about.  Without knowing exactly what the goop is, I 
would recommend the following:

1)  Gently scrape off as much of the material as possible using a soft 
scraping tool.  I recommend a wooden popsicle stick.  The key here is to 
not damage anything.  Be GENTLE.

2)  Once you have most of the goop cleaned off, I recommend using 
alcohol to remove any remaining residue.  You can use store bought 
Isopropyl alcohol but the problem is that the stuff you buy in a store 
is only 70%...with the remaining 30% being water.  A much better thing 
to use is to buy some Ethyl alcohol.  Go to your local liquor store and 
buy a pint of grain alcohol.  Brand name around here is "Everclear".  
This is 95% Ethyl alcohol...about as high as you can get outside of a 
chemistry lab.  Alcohol is naturally hygroscopic (absorbs water) so 
you'll never get 100%.

3)  Use the alcohol liberally, flooding the area to be cleaned.  If its 
near the edge of the board, tilt the board so that most of the alcohol 
runs off into a bowl.  What you want to do is wash the alcohol over the 
goop and let the residue flow off of the board instead of getting 
trapped under other parts.

4)  Use a soft brush, like a clean toothbrush, in a circular motion to 
get the remaining part of the board really clean.  Soak up any remaining 
alcohol with paper towel, getting as much off as possible.

5)  Depending on how much crud you have to remove, you can give a final 
rinse with some distilled or de-ionized water.  i wouldn't use tap 
water.  The water won't hurt most electronics...we use water to clean PC 
boards all the time.  You want to keep the water away, alcohol too, from 
any parts that are not sealed like switches, connectors and relays.  
Normal surface mount components are fine.

6) Finally, soak up as much of the remaining liquid with more clean 
paper towels and gently dry the area of the board with a little warm 
air.  A hair dryer is ideal.  Don't go overboard with the heat...you 
definitely don't want to reflow the solder :))

Once you have the circuit traces exposed you'll be able to assess any 
corrosion or damage.  This part will be another story depending on what 
repairs you have to make.

Finally, you can drink the remaining **unused** Ethyl alcohol...not 
Isopropyl :))  Just be careful...it's strong!!

On 12/26/2010 1:04 AM, Vic K2VCO wrote:
> I have a board (not an Elecraft product!) which has several SMD electrolytics that have
> failed, leaking brown, corrosive goop. The board is hard to find and expensive. I am going
> to try to fix it.
>
> Question: how do you clean the brown capacitor goop off the board?  Some of the traces may
> be corroded, but I can't tell without getting this stuff off! And I don't want to damage
> them by scraping.

-- 


73,

Gary K9GS

Check out K9NS on the web:  http://www.k9ns.com
Greater Milwaukee DX Association: http://www.gmdxa.org
Society of Midwest Contesters: http://www.w9smc.com

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