Yes, it's madness. A gradient of 2500 V/mm on a substrate that absorbs 
humidity like blotting paper? Even in prehistoric days, MIL specs on G10 
substrates (better than PI for humidity absorption), translated into 
real units, talked about gradients of ~150 V/mm and even that was 
considered hairy by some (myself included), as it tore apart any ionics 
that happened to be in the neighbourhood.

Brian

Steve Kelly wrote:
> Good Day To All,
> 
> Back in April I posted some queries on the tech-net about high voltage
> testing after 85C/85RH testing and was basically told this test was
> impossible and I agree with that assessment. But some things have a life of
> their own.
> 
> To re-iterate: We are building a 4 layer flex circuit. All layers are 18
> micron copper and all lines and spaces assuming perfect etch are 100 micron
> lines and 100 micron spaces. My customer for some reason signed up to pass a
> 250 volt test after 1000 hours of 85C/85RH damp heat test. My premise is
> being in this case a polyimide build if they dried the circuit after this
> test it should pass. They do not want to dry it and still have it pass. 
> 
> The previous threads in summary said this test was "madness" - I agree but
> what is the scientific explanation of why this is madness. 
> 
> Please note this requirement is being driven by very large telecom companies
> and the worlds largest provider of internet gear. 
> 
> Thanks again for the help.
> 
> Regards Steve Kelly
> 
>  
> 
> Steve Kelly
> 
> (416) 750-8433 (work)
> 
> (416) 750-0016 (fax)
> 
> (416) 577-8433 (cell)
> 
>  
> 
> 
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