Kari,

I'm afraid I don't have the time to expound on how to qualify the manufacturing process, but I do recommend that you get a copy of IPC-HDBK-830, "Guidelines for Design, Selection and Application of Conformal Coatings". You can find much valuable information in that guideline.

Per-Erik Tegehall

-----Ursprungligt meddelande-----
Från: Kari Rambo [mailto:[log in to unmask]]
Skickat: den 11 september 2003 16:12
Till: 'TechNet E-Mail Forum.'; Tegehall Per-Erik
Ämne: RE: [TN] Silicone conformal coating


Per-Erik, 

Any amount of information you would care to share regarding qualification of
the manufacturing process for conformal coating would be greatly
appreciated. 

Kari Rambo


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Tegehall Per-Erik
Sent: Thursday, September 11, 2003 6:16 AM
To: [log in to unmask]
Subject: Re: [TN] Silicone conformal coating

David,

Visual requirements are not very useful for this purpose since you cannot
inspect beneath area array components and even when you have leaded
components you cannot incpect the backside of the leads. Furthermore,
"openings" my also form if field environments for example by blistering and
cracking of the coating. Therefore, in my opinion, you need to do some sort
of experimental verification that will show you that the coating gives
adequate protection during the expected life. That is difficut to do on a
product that will be sold to a customer. Thus, you should focus on
qualifying the manufacturing process rather than the finished product. 

How should you then do that? That is another question that would require a
very long answer.

Per-Erik

-----Ursprungligt meddelande-----
Från: David Douthit [mailto:[log in to unmask]]
Skickat: den 10 september 2003 15:08
Till: TechNet E-Mail Forum.; Tegehall Per-Erik
Ämne: Re: [TN] Silicone conformal coating


Per-Erik,

"(as long as you don't have opens in the coating)" This raises an
interesting question. Just exactly how
do you determine if there are "openings" (microscopic pinholes and/or
inadequate coverage of sharp edges and points)?

Then, if you do determine there are, what is done about it?

David A. Douthit
Manager
LoCan LLC

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