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Increasing Electronics Reliability With Conformal Coatings

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Nancy Golden
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Very Informative Article - showing SR may be best choice...
Nancy Golden   3/11/2013 11:41:15 AM
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Kent, thanks for the very informative article on a very relevant topic. Initially I was confused by what seemed like conflicting statements:

Regarding Silicones – "However, these superior properties do come at a cost, which is typically a higher price per kilogram."

And "Yet, several factors are influencing engineers to choose silicone conformal coatings over other options to provide greater reliability and durability to electronic devices. These factors are low stress, lower production costs..."

But you did an admirable job explaining why despite the higher cost per kilogram, that silicone may still be the most cost-effective choice, along with its many advantages. It is also a good lesson for those of us who tend to just look at the surface. Initial cost is often the determining factor for a process and Kent's explanation proves that is not always the best case...

My only question is in regards to the final sentence of the summary which states "Studies have shown..." it leaves me wondering which studies are being referred to...is this information internal to Dow Corning specifically or are there some industry studies that have been done by other sources as well that are available?

Ann R. Thryft
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Re: Very Informative Article - showing SR may be best choice...
Ann R. Thryft   3/11/2013 12:20:57 PM
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The discussion of cost reminds me of so many instances I've seen where the initial price/cost of an item itself may be higher than competitive items, but due to various characteristics it costs less to use over time. That appears to be the case here, with a higher initial cost of the material itself vs a lower overall production cost, i.e., cost of using it during production. I think Nancy's right; it's so easy to just look at the material or product cost, not the cost of ownership or cost of use.

Nancy Golden
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Re: Very Informative Article - showing SR may be best choice...
Nancy Golden   3/11/2013 12:37:56 PM
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Unfortunately Ann, on the flip side, sometimes I think the manufacturer is cognizant of the advantages but has to go with the lower cost at start up simply because they can't afford to do otherwise, or if they do go with the higher costing product then they can't market their product at a price to make them profitable...for example we went with the higher cost of furniture grade pvc pipe with our horse trail obstacle business because we knew it was a better and safer product but because we were small fish, we could not afford to buy in volume. This drove our prices higher even with a ridiculously small profit margin and we could not become profitable...

Making good business decisions is a very difficult task especially when you are first starting out and have a very small budget...

Ann R. Thryft
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Re: Very Informative Article - showing SR may be best choice...
Ann R. Thryft   3/13/2013 4:47:46 PM
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Nancy, I know what you mean. Seems like that subject--engineers want a better product/component/material, but management/beancounters won't go for the slightly higher cost--comes up a lot in the comment boards. But your point about smaller companies buying smaller quantities is a good one, too. I know that from having run a small business for several years.

Nancy Golden
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Re: Very Informative Article - showing SR may be best choice...
Nancy Golden   3/13/2013 4:55:06 PM
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Having run a small business Ann, I am sure you did not get to take advantage of volume pricing like Walmart. That is what is running the Mom and Pop shops out of business and it's a shame - usually the quality is so much better since they take personal pride in their product. What was really frustrating is that we chose the better material, knowing we wouldn't be able to compete but refusing to compromise. Unfortunately initial cost will often call the shots even when it makes sense to do otherwise...and if you don't let it, you'll fail because you can't be profitable.

Ann R. Thryft
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Re: Very Informative Article - showing SR may be best choice...
Ann R. Thryft   3/13/2013 5:23:08 PM
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You're right about that, of course. Both that I didn't get to take advantage of volume pricing, and the effects of the Walmartization of America. Personally, I don't shop there as my own form of boycotting. The practice of only caring about large numbers especially burns me living in a low-population density area where the whole point is individualized tastes and service--or it should be. Instead, I'm told that YXZ product has disappeared from my local store because volumes aren't high enough. Those practices may work, and make sense, in NYC,  but not in a small town of 4000 or 6000 people.

tekochip
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Wicking and other issues.
tekochip   3/11/2013 12:38:32 PM
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Something not covered in the article is that conformal coatings have a way of creeping into places they don't belong.  Connectors, of course, are the biggest problem.
 
That said, conformal coatings offer so many advantages that I prefer to use them even when not designing outdoor products.  The coatings prevent humidity damage that can be seen even with indoor applications, as well as protection from dust and smoke (some people still do).  Lastly, conformal coatings also provide mechanical support for components preventing damage from vibration.
 
It's a big commitment and increased product cost from many angles, but coatings really do improve a product's reliability.


Ann R. Thryft
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Re: Wicking and other issues.
Ann R. Thryft   3/11/2013 4:46:06 PM
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From tekochip's post, it sounds like this general class of coatings decreases cost of ownership for buyers, at least partly from lengthening product life. I wonder under what circumstances the higher product cost is balanced by lower production costs.

tekochip
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Re: Wicking and other issues.
tekochip   3/12/2013 8:24:48 AM
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For me the applications that use coatings are; agricultural, automotive, washroom appliances, dishwashers and washing machines.


CougFan
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Re: Wicking and other issues.
CougFan   3/12/2013 12:56:38 PM
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Aerospace applications use coatings for many reasons - one to help mitigate Tin Wiskers.

Ann R. Thryft
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Re: Wicking and other issues.
Ann R. Thryft   3/12/2013 9:55:56 PM
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What I'm wondering isn't so much what apps these coatings are good for, but in what cases the higher purchase cost of the coating gets offset by the lower production costs. Anybody know?

drsmith_m304
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Iron
Silicone Conformal Coatings
drsmith_m304   3/13/2013 11:41:10 AM
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If boards are ever to be repaired, or parts replaced, the coatings have to be removed. With Acrylic or Polyurethanes removal is relatively easy, so the repair is easy. However, silicone coatings are a different story. From the HumiSeal website:

Silicone - This is the most difficult coating to remove and the coating least compatible with all of the other coating types. There are no solvents to remove silicone so it may only be removed by abrasion and this will leave silicone contamination on the board surface. Complete removal is virtually impossible so local repair is generally all that is attempted.

Also, companies that outsource their board manufacturing typically lose their PCBA fabrication kowledge over the years (if they had any to begin with) and are constrained to initially judge coatings based only on their manufacturing costs, which include the material cost and the extra time, equipment and labor to cure the coating. Surprisingly, some of the most popular non-USA Contract Manufactures have little if any experience with coating, coating chemistry or coating processes - so these CM can offer virtually no well considered advice on coatings. Bean counters ask "Which is the cheapest and easiest to apply?" and the answer is usually "Acrylic" due to the similarity with ordinary acrylic spray paints.

Ann R. Thryft
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Re: Silicone Conformal Coatings
Ann R. Thryft   3/13/2013 12:53:29 PM
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Thanks for the feedback drsmith. Interesting points about the difficulty of silicone removability, since one of the supposed pluses of silicone coatings is it good adherence to typical board substrate materials. OTOH, Design For Disassembly/Recycling are not yet established best practices everywhere. Stay tuned--our upcoming May materials feature article addresses some DFD/R topics.

Nancy Golden
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Platinum
Re: Silicone Conformal Coatings
Nancy Golden   3/13/2013 5:46:25 PM
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I'm just wondering how important it is to be able to remove the coating, drsmith... We used to have the mindset of repairing a product at board level, then we started board swapping, and now we don't even bother to do that in many cases...our it's broke - throw it away mentality may preclude the need for being able to access the board and if the coating is doing its job - I am thinking that the need for repairs should go down.

Ann R. Thryft
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Re: Silicone Conformal Coatings
Ann R. Thryft   3/14/2013 12:01:35 PM
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Removing the coating is not just potentially important in repairs, but it's essential for Design For Disassembly/Design For Recycling practices. Our upcoming May materials feature article addresses some DFD/DFR topics along these lines.

Nancy Golden
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Re: Silicone Conformal Coatings
Nancy Golden   3/14/2013 12:19:15 PM
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Thanks for pointing that out, Ann. I am looking forward to reading more about it in May!

Ann R. Thryft
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Re: Silicone Conformal Coatings
Ann R. Thryft   3/14/2013 1:49:59 PM
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You're welcome, Nancy. You can access the DN editorial calendar here: http://www.designnews.com/document.asp?doc_id=208723

Nancy Golden
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Re: Silicone Conformal Coatings
Nancy Golden   3/14/2013 2:19:31 PM
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That's great, Ann - I love the calendar. There are some great topics coming up!

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