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December 2006

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Subject:
Re: Membrane keypad failures
From:
Carl VanWormer <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Carl VanWormer <[log in to unmask]>
Date:
Fri, 15 Dec 2006 15:25:39 -0800
Content-Type:
text/plain
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text/plain (54 lines) 
 



The dielectric is Electordag 452SS UV Curable Dielectric Coating.  The manufacturer says they coat with 2 layers to reduce the chances of a pinhole opening allowing a short circuit.  Is this a possible clue of something to chase for my humidity related shorts?


Carl Van Wormer
Cipher Systems
1800 NW 169th Place, Suite B-100
Beaverton, OR  97006
Phone (503)-617-7447 extension 20    



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Lazzara
Sent: Thursday, December 14, 2006 6:08 AM
To: [log in to unmask]
Subject: Re: [TN] Membrane keypad failures

In a message dated 12/13/2006 2:01:54 P.M. Eastern Standard Time, [log in to unmask] writes:

have two  membrane keypads that have shown intermittent "short circuit"  
failures. 
Hello, Carl:
 
OK, you've probably already looked for residual conductive ink between conductors, but look closer for dust. Over-cured thick film conductive  polymers lose ductility and become [relatively] brittle. The "...wiggling,  banging..." 
you described could produce enough conductive particulate between  the circuits to yield an intermittent high-resistance short.
 
I'm also wondering about your dielectric: What is the dielectric  material (e.g., is it solder mask)?
 
 
ROBERT LAZZARA
VP, Business Development
T: (800) 560-9457
F:  (800) 878-5566 (y servicio de mensaje espaņol)
E:  [log in to unmask]
W:_  www.CircuitConnectUSA.com_ (http://www.CircuitConnectUSA.com) 

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