Hi Inge,
From what I can gather - 85C in 85% relative humidity. After the 1000 hours
they do a controlled linear ramp to 25C/45% RH and then let the sample
stabilize at this level for 4 hours then the test is done. I hope this
answers your question. Regards Steve Kelly
-----Original Message-----
From: Inge [mailto:[log in to unmask]]
Sent: June-25-08 3:31 PM
To: Steve Kelly; 'TechNet E-Mail Forum'
Subject: Re: [TN] Bias voltage test in damp heat
Steve,
you mean a 85/85 test without water vapour?
Inge
----- Original Message -----
From: "Steve Kelly" <[log in to unmask]>
To: "'TechNet E-Mail Forum'" <[log in to unmask]>; "'Inge'"
<[log in to unmask]>
Sent: Wednesday, June 25, 2008 12:21 PM
Subject: RE: [TN] Bias voltage test in damp heat
> Hi Inge,
> The flex circuit has a BGA connector assembled on both ends and the test
> is
> done on the assembly. To my mind this is not a water vapour penetration
> test. Regards Steve Kelly
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
> Sent: June-25-08 2:37 PM
> To: [log in to unmask]
> Subject: Re: [TN] Bias voltage test in damp heat
>
> Was the test performed on the flex itself and not the whole assembly? If
> the
>
> answer is ' yes', I do understand better, because then the test was a
> test
> on the PI's resistance to humidity. With other words, a water vapour
> penetration test.
> Inge
>
>
> ----- Original Message -----
> From: "Eric CHRISTISON" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Wednesday, June 25, 2008 9:50 AM
> Subject: Re: [TN] Bias voltage test in damp heat
>
>
>> Alternatively you could suggest to the customer that they save time on
>> qualification by ditching the 1000 hours 85/85 and simply submerge the
>> equipment in a bucket of warm water for a day. The water uptake will be
>> much the same.
>>
>> Good luck.
>>
>>
>>
>> Douglas O. Pauls wrote:
>>> Steve,
>>> I agree that this is madness, unless the telecom supplier has an end use
>>> environment of 85/85 where power-on in humid conditions is a reality.
>>> Assuming that the equipment is not functioning in a steam environment,
>>> here is the "science" that you are looking for.
>>>
>>> Designers, when they have knowledge of the material characteristics,
>>> will
>
>>> design spacings dependent on the dielectric strength or dielectric
>>> withstanding voltage of the laminate. The values in the data sheets for
>>> the laminates specify these parameters, but only for lab ambient
>>> conditions, not after 85/85 conditioning. When you expose a hydrophilic
>>> material to a long exposure in hot/humid conditions, then you don't have
>>> that same dielectric strength (dramatically reduced) and you have
>>> violated the design assumptions. Polyimide is such a hydrophilic
>>> material. I believe Brian Ellis referred to it as blotter paper, in
>>> which I would concur. If you allow the circuit to dry out, then you
>>> return to the expected dielectric strength. You may already be at an
>>> unrealistic threshold with 2500 volts/mm gradient, as Brian also pointed
>>> out.
>>>
>>> Unless the designer had a firm value for dielectric strength of the
>>> substrate after 85/85 conditioning, which would change as the substrate
>>> rapidly dried out, then the design would not and could not work.
>>>
>>> Doug Pauls
>>>
>>>
>>>
>>>
>>> Steve Kelly <[log in to unmask]> Sent by: TechNet <[log in to unmask]>
>>> 06/25/2008 10:09 AM
>>> Please respond to
>>> TechNet E-Mail Forum <[log in to unmask]>; Please respond to
>>> Steve Kelly <[log in to unmask]>
>>>
>>>
>>> To
>>> [log in to unmask]
>>> cc
>>>
>>> Subject
>>> [TN] Bias voltage test in damp heat
>>>
>>>
>>>
>>>
>>>
>>>
>>> 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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>>
>> --
>> Eric Christison Msc
>> Mechanical Engineer
>> Consumer & Micro group
>> Imaging Division
>>
>> STMicroelectronics (R&D) Ltd
>> 33 Pinkhill
>> Edinburgh EH12 7BF
>> United Kingdom
>>
>> Tel: +44 (0)131 336 6165
>> Fax: + 44 (0)131 336 6001
>>
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