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March 2007

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Subject:
From:
Phil Kinner <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Phil Kinner <[log in to unmask]>
Date:
Mon, 5 Mar 2007 15:39:37 -0000
Content-Type:
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text/plain (197 lines)
Too true.  It's due to the fact that UR materials are generally
solvent-resistant, whereas AR materials generally have little or no solvent
resistance, hence the ease of rework.

All that you are doing adding a UR over an AR is re-solvating the acrylic
material with the solvents in the UR.  So you then have a mixture of acrylic
and UR polymers in solvent and as the solvent evaporates you get a
combination of chemistries left behind.

The two polymer types are rarely compatible, and you would usually end up
with either a very hazy coating or a gooey mess as Ramon describes
(technical term, we use it often ;-)

Best Regards,

Phil.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Dehoyos, Ramon
Sent: 05 March 2007 14:15
To: [log in to unmask]
Subject: Re: [TN] Use of Type AR Conformal Coating for Military PCBs

    
	UR over AR does not work. The coating combination becomes gooey.
AR over UR works well. Ed Mines can explain the chemical aspects of this
result.
	Ramon

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar
Sent: Monday, March 05, 2007 8:51 AM
To: [log in to unmask]
Subject: Re: [TN] Use of Type AR Conformal Coating for Military PCBs

Echo...
Except for Toluene....banned in Europe...we use a Thinner.
Inge 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas O. Pauls
Sent: den 5 mars 2007 14:36
To: [log in to unmask]
Subject: Re: [TN] Use of Type AR Conformal Coating for Military PCBs

Good morning Les,

Rockwell Collins is one such company.  Many of our military products
require a type AR coating for reworkability.  We have used Humiseal 1B31
successfully on military product for many years.  We have applied by
HVLP spray, automated/programmable spray, dip coating, and brush
coating.  You can get the minimum 1 mil by brush coating with the
as-supplied viscosity.
You have to thin the material to spray, but you can usually get the
minimum
1 mil in a single pass.

Any adverse concerns (e.g., solder joints, solder mask, etc.)?    Not
really.  The biggest concerns are flooding of connectors as the material
spreads and wicks.

Any humidity test results?   Yes.  We regularly pass MIL-STD-810 and
DO-160E humidity testing.

Method of coating removal?  The material dissolves in toluene so most
rework methods involve first dissolving the material in toluene.

Rework using either AR or UR coatings.   We recoat with 1B31 after
rework.
I have not investigated rework with a UR over 1B31.

Doug Pauls



 

             - Bogert

             <[log in to unmask]>

             Sent by: TechNet
To 
             <[log in to unmask]>         [log in to unmask]

 
cc 
 

             03/02/2007 04:55
Subject 
             AM                        [TN] Use of Type AR Conformal

                                       Coating for Military PCBs

 

             Please respond to

              TechNet E-Mail

                   Forum

             <[log in to unmask]>

             ; Please respond

                    to

                 - Bogert

             <[log in to unmask]>

 

 





March 2, 2007

I am seeking info on any military folks who coat their assemblies with
Type AR coating.  How do you apply it/  how many spray coats on each
side of the assembly are needed to achieve the min J-STD-001 thickness?
Any adverse concerns (e.g., solder joints, solder mask, etc.)?  Any
humidity test results? method of coating removal?  Rework using either
AR or UR coatings.


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