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October 2010

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Subject:
From:
David Douthit <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, David Douthit <[log in to unmask]>
Date:
Fri, 22 Oct 2010 14:42:25 -0700
Content-Type:
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Doug,

  | am offering my apologies to members of this forum for my actions  
while dealing with "coating" issues.

The only excuse | can give is very high level of frustration |  
developed while trying to gain information and resolve
difficulties with the attitudes surrounding coatings in general (A lot  
of if the unit makes it past warranty so what).

Coatings can greatly improve the operational efficiency of hardware if  
the limitations and characteristics of the coating material is  
understood.
Unfortunately these issues can be overlooked during design,  
manufacturing, and field operations of equipment.
This results in abnormal operational events that can rank a close  
second to solder joint problems in "harsh environments".

Because testing of hardware in simulated end use environments is  
difficult (if not impossible), expensive, and time consuming
it is difficult to raise the issue with much hope of a positive  
response.

The |PC "stepped up to the plate" and created the "Conformal Coatings  
Handbook" which has clarified and addressed many of the issues | had.

For that | want thank the |PC and all the members of that committee  
for the long hours and hard work (plus putting up with me) that went  
into
and continues to go into that document. |t was a real balm that helped  
"ease a tortured soul".

David A. Douthit

On Oct 22, 2010, at 7:26 AM, Douglas Pauls wrote:

> Yes, I remember Dave Douthit.  I did not always agree with his  
> approaches
> to things, but he did have some interesting data.
>
> The indoor NH3 is not that hard to fathom.  Most of your industrial
> cleaning solutions, especially for glass, have some ammonia in it,  
> so PPB
> levels of NH3 are not unusual.  If you are anywhere in the Midwest  
> in the
> United States, anywhere from April to June, farmers are planting  
> fields
> and most apply anhydrous ammonia during the process.  I am betting  
> Iowa is
> a whole lot higher in NH3 during that time than the PPB range.
>
> Doug Pauls
>
>
>
> Inge <[log in to unmask]>
> Sent by: TechNet <[log in to unmask]>
> 10/21/2010 04:51 PM
> Please respond to
> Inge <[log in to unmask]>
>
>
> To
> [log in to unmask]
> cc
>
> Subject
> Re: [TN] Conformal Coating Board Edges
>
>
>
>
>
>
> "Second, how do you determine how harsh an environment  has to be in  
> order
> to coat the edges? "
> Dough Pauls
>
> Answer:
>
> Do you remember David Douthit? His definition of Harsh was  
> environments
> that belong to the upper range of the values in the 'OUTDOOR'  
> column. His
> work. There exist no true formulas, but the values below shall in
> principle be multiplied with Temperature, Time, barometric pressure  
> and
> local weather conditions (sun radiation for example). We have in  
> principle
> followed similar figures.
>
> Concentration of selected gaseous air constituents (ppb) in the United
> States.
>
> OUTDOOR
>
> O3          4-43
> H2O2     10-30
> SO2        1-65
> H2S        0.7-24
> NO2        9-78
> HNO3      1-10
> NH3         7-16
> HCL         0.18-3
> CL2          0.005-0.08
> HCHO      4-15
> HCOOH   4-20
>
>
>
>
> INDOOR
>
> O3           3-30
> H2O2      5
> SO2         0.3-14
> H2S         0.1-0.7
> NO2         1-29
> HNO3       3
> NH3          13-259
> HCL          0.05-0.18
> CL2           0.001-0.005
> HCHO       10
> HCOOH     20
>
> There is one thing I don't understand: NH3 up to 259 ppb indoor.
>
> Hope this gave you at least an idea.
>
> /Inge
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