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Conformal Coatings for PCBs

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DWILSON373
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Safety Agency Approvals
DWILSON373   1/30/2014 9:44:58 AM
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Don't overlook the need to have a Safety Agency approval of the coating material.  One spray on product I have used required a brush on primer be used to comply with the safety agency's "Conditions of Acceptability."

salbayeng
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nice posed photo
salbayeng   1/29/2014 8:42:05 PM
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I used to work at a reasearch lab and we had promo photos like this done

(a) Find the cleanest part of the lab , and move all the "real work" out of the shot

(b) Find the prettiest girl in the lab , get her to put on jewellry and makeup (not usually done in a lab due solvents in makeup, and jewellry tarnishes / snags on stuff)

(c) Make up some pretty colored tap water (usually just food coloring)

(d) Get the most impressive bit of glassware and assemble it in an interesting way, get new lab jacks out of the store, new clamps, new colored silicone hose.

(e) deck out the model in a new, ironed labcoat , new (nice looking wraparound style)  safety glasses , and rubber gloves

(f) Have the model gaze intently straight ahead , whilst turned to the camera, and adjusting something with the hand furtherest from the camera.

In reality , it would be a ratty lab coat , it would be done in a fume hood, and most importantly she would be looking at the bottom beaker  as that's were the action would be , the labjacks would be filthy as stuff dribbles over them,  wearing stained goggles but no jewellery or make-up  ... 

.......... 

As for conformal coatings , you really need UV tracers. And you need to pick your employees carefully, it requires a certain aptitude and attitude to apply clear coatings.

For "commercial " grade I normally use spray on acrylic, for "industrial" grade I use the thicker TRV brush-on. Both baked at 60C after drying , both can be removed with alchohol if you are desperate. Both are reasonably good for poking testprobes through and can be soldered through , ( a bit messy, but not impossible). Solder suckers struggle a bit though with gunking up, so connectors can be a nightmare, I've had to destroy the connector housing, then remove the pins one at a time. Using a hot air gun for SMD rework  can be very "interesting" as the coating can melt or burn.

The silicone coatings are more problematic, as solder won't generally stick properly, and you need to scrape away around the problem coating. 

 

 

 

_hm
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CEO
Re: repairing conformally coated boards
_hm   1/25/2014 5:36:51 AM
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We have machine that removes conformal coating for specific part or from whole board without damaging any of electronics parts or connectors. After repair one needs to redo conformal coating. It should not be difficult with proper tools.

elizabethsimon
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CEO
Re: repairing conformally coated boards
elizabethsimon   1/23/2014 4:33:36 PM
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Yes you are right that for repair of units from the customer, the old conformal coated boards are usually replaced.And for development we usually have boards that are not conformally coated.

Unfortunately there is occasionally a need to troubleshoot failed boards (if the failure rate is too high). At that point we have to remove enough of the coating to diagnose the problem.

 

prabhakar_deosthali
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CEO
Re: repairing conformally coated boards
prabhakar_deosthali   1/23/2014 11:59:23 AM
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Regarding the repairing of the boards protected by conformal coating - Yes ! It is a very difficult job and many times you just cannot remove this coating without damaging the PCB.

Conformal coating is normally used for industrial grade PCBs which have assured long life any way.  So it is best to replace them with new boards as removing conformal coating, repairing is certainly going to compromise on the reliability of the board.

Same thing applies for the POTTED sub assemblies used especially in automotive applications. If they fail, you just throw them out.

 

Garcia-Lasheras
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Blogger
Tropicalization
Garcia-Lasheras   1/23/2014 6:40:59 AM
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Thank you very much for this info -- it's amazing the plethora of conformal coating possibilities in the market coming from big chemical companies...

Once upon a time, I worked for a company where "tropicalization" was applied by hand by production line workers using different sizes of brushes and a "varnish" can.

By the way... conformal coating is a pain when you need to repair/refurbish a PCB that has previously been protected -- I wonder if somebody is working on this issue or maybe repairing a coated PCB is not worthy anymore!! 

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