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cpkotti
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Join Date: Jan 2013
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PCB Board Corrosion

01/17/2013 7:11 AM

Dear sir,

I have a problem, my plant is controlled atmosphere (Humidifcation plant is there)

recently we have faced that the PCB boards in the machines are getting corroded & connections are getting desoldered or getting short,

is there any protective coating that we can apply over the PCB boards

Please suggest

Puniyakotti
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Pathfinder Tags: Corrosion in PCB board
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lyn
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#1

Re: PCB board Corrosion

01/17/2013 7:17 AM

Conformal coating - Wikipedia, the free encyclopedia

  1. Conformal Coatings for Electronics - Dow Corning
  2. What are Conformal Coatings? - Dow Corning
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JPool
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#2

Re: PCB Board Corrosion

01/17/2013 9:07 AM

GA Lyn.

I was going to throw out a plug for our company which has a several plants that do nothing but conformal coatings, but we use paraxylylene which must be vacuum deposited and would require you to send your boards to one of our facilities.

http://www.metalimprovement.com/parylene_coatings.php

What you need is an aerosal based conformal coating that you can apply yourself. It will not have the quality of Parylene but should get the job done.

http://www.humiseal.com/products/aerosol-products

http://www.mgchemicals.com/products/protective-coatings/conformal/silicone-conformal-coating-422a/

http://search.yahoo.com/search;_ylt=AnuaP_5OlU8BSGCi_hK5hW6bvZx4?p=aerosal+conformal+coating&toggle=1&cop=mss&ei=UTF-8&fr=yfp-t-701

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lyn
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#5
In reply to #2

Re: PCB Board Corrosion

01/17/2013 10:56 AM

Ah, a little shameless self-promotion.

Yes, I know Parylene well. I used it in the 1980's on some classified projects for government. We discovered that it was a good Uv filter, too as we wanted to use it to coat some EEPROMS. I was evaluating several coatings at the time and we went with a different type for this application.

The biggest problem we had was selectively masking features and then getting the coating off those spots later.

But, it's great stuff. Is it still MIL-C-46058? Or is there a newer spec?

I have to agree with Fred. This sounds more complicated than just a coating problem.
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JPool
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#7
In reply to #5

Re: PCB Board Corrosion

01/17/2013 11:35 AM

Lyn, spec is now MIL-L-46058C

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lyn
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#8
In reply to #7

Re: PCB Board Corrosion

01/17/2013 12:29 PM

"L"? Did the title change?
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JPool
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#9
In reply to #8

Re: PCB Board Corrosion

01/17/2013 2:23 PM

I got it right off of our website, so I guess it did. I myself was graduating high school and chasing girls in the '80's so I don't know what it was then.

http://www.paryleneinc.com//About-Us.php

I can't tell you about secret government projects of the 80's just the secret government projects that I am working on now... wait, I signed the non-discloser agreement, so no I can't, but some of them are cool.

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lyn
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#10
In reply to #9

Re: PCB Board Corrosion

01/17/2013 4:59 PM

They changed the title from Conformal Coating to Insulating Compound, thus the "I".

I remember the old days. Over the course of my career, I worked for all the agencies whose names had 3 initials, except the FBI.

As far as I know, everything I worked on is obsolete and out of service now. The Shuttle was the last thing in service that I worked on and it wasn't really secret.
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Doorman
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#11
In reply to #10

Re: PCB Board Corrosion

01/17/2013 5:21 PM

What's 'The Shuttle'?

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lyn
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#12
In reply to #11

Re: PCB Board Corrosion

01/17/2013 5:24 PM

How quickly they forget.
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Doorman
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#13
In reply to #12

Re: PCB Board Corrosion

01/17/2013 5:38 PM

Ah, the Endeavour (OV-105), shown landing at Edwards, now housed at the Samuel Oschin Air and Space Center.

Yeah, I guess I read something about The Shuttles in the papers.

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lyn
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#14
In reply to #13

Re: PCB Board Corrosion

01/17/2013 7:03 PM
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redfred
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#3

Re: PCB Board Corrosion

01/17/2013 10:16 AM

Conformal coating is a sound method of sealing electronics from contaminants. However, the common method I can think of a contaminant breaking electrical connections involves contaminations happening during the PCB assembly process. Sealing a contaminated PCB will not help this. If the OP is a PCB manufacturer and their product exhibits these failures then a QA review at the very least is required.

If the failing PCB boards are part of the plant infrastructure then this is a completely different problem that sealing may not help. In this case I suspect that something subtle has changed in the plant that requires some real investigative sleuthing. Replacement PCB boards maybe cheap counterfeit boards. The environment may not be as well controlled as the OP thinks. Humidity levels is only one aspect and having a humidity control system does not guarantee that it is working at the site of these failures. The PCB boards may just be showing the fatigue of having been run for so long, the contamination splashes on these fatigue failures maybe a red herring. The staff maybe overworked and are now making honest operational errors.

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SolarEagle
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#4
In reply to #3

Re: PCB Board Corrosion

01/17/2013 10:44 AM

This sounds more likely to me as well....

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The.Tinkerer
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#6

Re: PCB Board Corrosion

01/17/2013 11:04 AM

Immerse everything in mineral oil!

Do it!

Do it now!

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SolarEagle
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#15
In reply to #6

Re: PCB Board Corrosion

01/17/2013 9:24 PM

What now?!

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gmphadte
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#16

Re: PCB Board Corrosion

01/18/2013 1:03 AM

Connections getting desoldered can be heat related problem.

Gajanan Phadte
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geraldpaxton
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#17

Re: PCB Board Corrosion

01/18/2013 4:40 PM

Back in the '80's I designed and built automated systems used in the welding environment. Typical contaminants were weld fume, grinding dust, moisture, etc. I used a coating of 'glyptal' a high silaca solids varnish. My shop system still functions in this environment 25 years later. It is opaque and difficult to remove, but seals against most contaminants.
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Doorman (2); geraldpaxton (1); gmphadte (1); JPool (3); lyn (6); redfred (1); SolarEagle (2); The.Tinkerer (1)

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