Conformal PCB Coating: The Process Matters

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Michael Allen
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Re: I Wonder
Michael Allen   11/25/2012 9:49:52 AM
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A lot of good questions and comments here.  I typically see the cost of conformal coating individual boards below $5.00 in 100 to 1K quantity.  Boards that can be conformally coated in arrays obviously have a much lower cost depending on the piece size.  We usually use our robotic coating equipment so having keep outs does not raise the cost.  Many of today's coatings such as acrylic are easily repairable.  UV tracers make it very easy to see where you have adequate coverage.  The increased life of the board depends greatly on the environment that the boards will see.  I have seen boards that were used in a machining application that by design were in dust proof enclosure.  These boards had not been conformally coated and covered in metallic dust and filings leading to the boards failure.  How often does a company inspect and repair seals on a 20 year old machine?  This machine could have not been taken down if these boards were coated.  In addition to protecting the boards the conformal coating can provide additional mechanical protection.  All of the parts are held to the board by their bodies via the coating, not just by the solder.  This can certainly enhance the reliability of boards used in applications like aviation.

elctrnx_lyf
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Re: Conformal coating
elctrnx_lyf   11/24/2012 7:33:40 AM
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Many contract manufacturing companies have been making investments for the process of conformal coating. As there is robotic technology becomes more and more matured, there will be more improvements in the reliability of conformal coatings.

Ed Branco
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Conformal coating
Ed Branco   11/22/2012 2:08:39 PM
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Over the years I have found printed circuit assemblies have pushed the limits of all of the materials used to and processes used to apply them. I have researched several of the CNC machines on the market and found they fall short of for filling all the needs for all designs. Many designs have to lower the acceptance criteria for the sake of full automation. We have several automated machines the coat selected areas, but the high end parts at this point still requires very skilled sprayers, and maskers. Most designs we see today have conformal coating is an after thought.

_hm
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Some application do require Conformal coating
_hm   11/22/2012 4:41:11 AM
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Some application like defense, industrial control etc. do require conformal coating. However, some of electronics used in office and home may not require conformal coating.

prabhakar_deosthali
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Re: serviceability of PCBs with conformal coating
prabhakar_deosthali   11/21/2012 11:52:43 PM
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Thanks David for enlightening me on this issue of repair and rework. As far automated tools for surface coating is concerned, I designed a robotic work station for surface hardening by chemical spray by a robot. This robot had a teach and learn function whichwas very useful in determining the exact depth of the coat with precision and repeatability. I guess similar tools can be employed for conformal coating

bobwillis
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Conformal Coating Matters
bobwillis   11/21/2012 12:04:56 PM
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Many thanks for the overview on coating and the issues to consider. Readers may be interested in the video on quality control for coatings processes see
 my video on measurement

IPC sell inspection standards wall charts for conformal coating, interactive CD ROM and photo CD ROMs used for creating training content. I am not sure if anyone else offers this range of training products? We have been running webinars on coating for the last couple of years which look like a good training medium for worldwide consumption see webinars

Many thanks again

Bob Willis

 

David G Allen
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Re: serviceability of PCBs with conformal coating
David G Allen   11/21/2012 11:29:00 AM
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 Prabhakar,

You are most certainly correct, but there are ways to mitigate this concern. Depending on the requirements for coating and the coating material chosen, there are ways to manage any rework or repair after coating.

Urethane, being the more chemically resistant of the coatings may require a micro abrasion system for removing the coating within the suspect area where acrylic is VOC based and therefore will soften with the appropriate solvent.

David

FLYINGSCOT
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good stuff
FLYINGSCOT   11/21/2012 5:01:01 AM
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Thanks for writing this article as I never thought too much before about conformal coating.  How much does it cost as a percentage of the average base board material and how environmentally sound are the coating materials?

prabhakar_deosthali
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serviceability of PCBs with conformal coating
prabhakar_deosthali   11/21/2012 12:53:49 AM
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This is quite an informative article on conformal coating. The conformal coating has assumed a significance not only in Industrial and military products but in consumer products such as home appliances - washing machines , dish washers and such things.

 

One of the disadvantage of conformal coating that I have experienced is that once the conformal coating is done, the boards become difficult to service and repair.  So such board design should take into account .

 



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