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April 2007

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Subject:
Re: bubbles in conformal coating
From:
Joel Alexander <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Wed, 25 Apr 2007 11:50:09 -0400
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IPC-CC-830 is a standard used by the manufacturer of the conformal coating 
to qualify their material. Can these also be applied to the application by 
the end user. IPC-A-610 states that bubbles are acceptable as long as they 
do not bridge adjacent conductors. 

Also is there a specific reference that states anything about the 
appearance of foam?



Joel Alexander
Quality Assurance Manager
TT APSCO, INC. 




Edward Mines <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
04/25/2007 10:26 AM

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Edward Mines <[log in to unmask]>


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Subject
[TN] bubbles in conformal coating






MIL-I-46058 & now IPC-CC-830 say conformal coatings should be "bubble 
free". Some have interpreted this as meaning that a few small bubbles away 
from components are acceptable.
  Foam is not acceptable.
 
  Some polyurethane conformal coatings generate gas as they cure. They 
should not be coated on very humid days. 
 
  Bubbles are also apt to form in conformal coatings when the coating is 
too thick. I've seen this happen in between closely spaced tall components 
even when the coating on most of the board is within customary limits and 
has no bubbles. The solution was to change the application technique.
 
  Get the coating and equipment manufacturers involved. They want your 
future business.
 
  Ed Mines

 
---------------------------------
Ahhh...imagining that irresistible "new car" smell?
 Check outnew cars at Yahoo! Autos.

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