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From:
Douglas Pauls <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 16 Mar 2010 12:38:20 -0500
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Wellllll,

Yes we clean the assembly, usually multiple times in a hot saponified 
in-line aqueous cleaner.  The part where we leave residues is often 
something like a BNC connector.  Minimal.  We do have a few true no-clean 
assemblies, but the bare boards are washed prior to start of the assembly 
operation.  Those assemblies have no cleaning and are conformally coated. 

Specifically, we use Indium SMQ-92J low residue paste, a variety of low 
solids fluxes for wave soldering, and Kester 245 or Alpha Telecore Plus 
for hand soldering.  Our present saponifer of choice is Kyzen Aquanox 
A4625. 

For the conformal coating, while we have a number that we use depending on 
application, by far the most get either Humiseal 1B31 solvent based 
acrylic, or Humiseal 1H20AR1 water based acrylic-urethane.

Doug Pauls



"Reyes, Angel LAM2 4429" <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
03/16/2010 12:03 PM
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Subject
Re: [TN] Conformal Coatings: Resistance to Humidity and Moisture






Hi Doug

 

Thanks for your answer; any document book that you can recommend about 
this matter will help.

 

Hopefully you could help with the following questions:

 

When you applied CC, do you clean the board assemblies? 

If cleaning is yes, what type of process do you use?

What type of coating would you recommend to be applied?

 

Some of our applications are for outdoor use, and harsh environment 
protection is very important

 

Regards,

Angel Reyes

 

________________________________

From: [log in to unmask] [mailto:[log in to unmask]] 
Sent: Tuesday, March 16, 2010 9:57 AM
To: Reyes, Angel LAM2 4429
Cc: TechNet E-Mail Forum
Subject: RE: [TN] Conformal Coatings: Resistance to Humidity and Moisture

 


Yes, we do this, but again, we know our residues very very well and have 
studied the compatibility of the flux residues with the coatings we use. 
It can be done, done reliably, and with decent adhesion of coating to flux 
residue. 

Doug Pauls 



"Reyes, Angel LAM2 4429" <[log in to unmask]> 

03/16/2010 11:39 AM 

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"TechNet E-Mail Forum" <[log in to unmask]>, <[log in to unmask]> 

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Subject

RE: [TN] Conformal Coatings: Resistance to Humidity and Moisture

 

 

 




Doug

This is a different question, but related with the same thing, is anyone 
have experience with CC applied on top of no clean flux

Regards,
Angel Reyes



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Tuesday, March 16, 2010 9:15 AM
To: [log in to unmask]
Subject: Re: [TN] Conformal Coatings: Resistance to Humidity and Moisture

We use silicone conformal coatings for some of our products.  The most 
common applications for the silicones is when you have liquid water 
running across the assembly.  Applications like our weather radar, which 
is in the nose cone of the plane and it rains inside the nose cone as you 
come down from the cold.  Other places it has been used when the assembly 
is likely to sit in liquid water, such as the bottom side of a 
motherboard.  Against liquid water, it is superior.  Against water vapor, 
not so much.  They also have a tendency to be very porous to sulfur 
compounds, which is very important if you are using any silver.  Like any 
other material, it has its positives and negatives and you have to weigh 
them with respect to the design life of the product, the end use 
environment, and the consequences of failure.  Dow Corning has a good 
knowledge base on its web site (www.dowcorning.com) that I often use.

What is your end use application?

Doug Pauls
Rockwell Collins



Jean-François Bissonnette <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
03/16/2010 10:44 AM
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[TN] Conformal Coatings: Resistance to Humidity and Moisture






Hello Technetters,



I'm preparing a informative document on conformal coatings so I did some 
searching around the Net.  There seems to be diverging opinions on the 
pros and cons for Silicone coatings.  Some places that they have a good 
moisture/humidity resistance, some other say that they are not the best 
for moisture resistance.  Anyone with hands on experience can share a bit 
of knowledge on that matter?



Thanks!



JF




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