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Subject:
From:
Joyce Koo <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 21 Mar 2017 13:42:54 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (208 lines)
http://www.dtic.mil/dtic/tr/fulltext/u2/249378.pdf

> I have seen the effects of corona consuming carbon impregnated ABS
> plastic, I wish I had the photos to share. The device lasted less than six
> months before the corona consumed the plastic and potting material. This
> was a device that was placed on a high voltage transmission line and a
> portion of it had to be at or near line potential to function correctly. I
> do not think we concluded if it was the actual corona that destroyed the
> plastic and potting material or the high concentration of ozone being
> produced. My guess it was a combination of both.
>
> Ted
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Ahne Oosterhof
> Sent: Tuesday, March 21, 2017 10:16 AM
> To: [log in to unmask]
> Subject: Re: WG: [TN] Screen On Insulation
>
> The high field strength allows corona to develop and corona "eats" plastic
> materials. Therefore no sharp ends on high voltage components and no sharp
> corners in high voltage conductors !!!!!!!!
>
> Experience is a very strict task master,
>
> Bin der, done dat,
> Ahne
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Giamis, Andy
> Sent: Tuesday, March 21, 2017 8:03 AM
> To: [log in to unmask]
> Subject: Re: [TN] WG: [TN] Screen On Insulation
>
> That's very interesting Carl.
>
> I have never considered a polymer degrading and breaking down as a result
> of electric field strength.  I suppose it is possible.  What did it look
> like.  What led you to that conclusion?
>
> Thanks,
> Andy
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Carl Van Wormer
> Sent: Tuesday, March 21, 2017 8:46 AM
> To: [log in to unmask]
> Subject: Re: [TN] WG: [TN] Screen On Insulation
>
> My experience with safety regulation electrical spacing has always
> required guaranteed distances and multiple barriers.  For example, where a
> plastic spacer/insulator had pin-hole fault possibilities, a double layer
> was required.  I would be concerned about a cleanliness fault (a chunk of
> debris, a protrusion from a mechanical impact, or a filament of PCB edge
> fiber) preventing a thin-layer applied coating from achieving its nominal
> protection characteristics.  I have seen double layer spacing requirements
> met by a notch in the PC board with an inserted Kapton shield.
> Also, beware of sharp edges and corners in HV environments.  I had one
> product fault that resulted in long-term (after 1-year) dielectric
> break-down of an insulated video HV anode wire near a sharp sheet-metal
> edge.  The electrical field strength is related to inverse radius of the
> physical elements.  The silicone wire insulation broke down because of the
> field strength, not because of abrasion from the sharp edge.
>
> Later,
> Carl
>
>
> Carl B. Van Wormer, P.E., AE7GD
> Senior Hardware Engineer
> Cipher Engineering LLC
>     21195 NW Evergreen Pkwy Ste 209
>     Hillsboro, OR  97124-7167
>     503-617-7447x303
>     [log in to unmask]     http://cipherengineering.com
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Torsten Hagge
> Sent: Tuesday, March 21, 2017 2:49 AM
> To: [log in to unmask]
> Subject: [TN] AW: [TN] WG: [TN] Screen On Insulation
>
> Hi Bob,
>
> parylene is closed at about 0,6µm, so at 1 mil you have a safety margin
> of about 4200 %.
>
> We have payed about 1500€ for a batch of 32pcs bio sensor PCBs with 40mm
> diameter...
>
> Take care,
> Torsten
>
>
> Best Regards
>
> KRISTRONICS GmbH
>
> Dipl.Ing. (FH) Torsten Hagge
> team leader HW development
> Gewerbegrund 5-9
> 24955 Harrislee
> Telefon +49 (0) 461 7741-624
> Telefax +49 (0) 461 7741-642
> [log in to unmask]
> www.kristronics.de
> Place of jurisdiction: Flensburg, commercial register: HRB 1433 FL CEO
> Dipl.-Ing. oec. Thormod Ohm VAD-Id DE 811182059 Bank account: Deutsche
> Bank AG Flensburg, account 4216610, bank number 21570011
> IBAN: DE32 2157 0011 0421 6610 00, BIC: DEUT DE HH 215  Please consider
> the environment before printing this e-mail
>
>
>
>
> -----Ursprüngliche Nachricht-----
> Von: Robert Kondner [mailto:[log in to unmask]]
> Gesendet: Montag, 20. März 2017 17:06
> An: 'TechNet E-Mail Forum'; Torsten Hagge
> Betreff: RE: [TN] WG: [TN] Screen On Insulation
>
> Torsten,
>
>  Do you know how thick a parylene coating is? My recollection is pretty
> thin.
>
>  So I checked, very high dielectric strength, thickness typically under 1
> mil but it can be built up further with longer processing time.
>
> Any idea wat coating with parylene cost for a small batch of boards?
>
> Thanks,
> Bob Kondner
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Torsten Hagge
> Sent: Monday, March 20, 2017 9:17 AM
> To: [log in to unmask]
> Subject: [TN] WG: [TN] Screen On Insulation
>
> Hi,
>
> cheap solution could be a 1mil kapton tape with the mention risk of air
> gaps, fine and cost expensive solution parylene HT  coating before placing
> the ferrite cores...
>
> Take care
> Torsten
>
>
>
> Best Regards
>
> KRISTRONICS GmbH
>
> Dipl.Ing. (FH) Torsten Hagge
> team leader HW development
> Gewerbegrund 5-9
> 24955 Harrislee
> Telefon +49 (0) 461 7741-624
> Telefax +49 (0) 461 7741-642
> [log in to unmask]
> www.kristronics.de
> Place of jurisdiction: Flensburg, commercial register: HRB 1433 FL CEO
> Dipl.-Ing. oec. Thormod Ohm VAD-Id DE 811182059 Bank account: Deutsche
> Bank AG Flensburg, account 4216610, bank number 21570011
> IBAN: DE32 2157 0011 0421 6610 00, BIC: DEUT DE HH 215  Please consider
> the environment before printing this e-mail
>
>
>
> -----Ursprüngliche Nachricht-----
> Von: TechNet [mailto:[log in to unmask]] Im Auftrag von Robert Kondner
> Gesendet: Freitag, 17. März 2017 21:11
> An: [log in to unmask]
> Betreff: [TN] Screen On Insulation
>
> Hi,
>
>
>
> We have a PCB that turns out to require 2500VAC test for 60 seconds and we
> had some flash over on pads to vias. We also have a planar ferrite
> transformer with primary windings on one side.
>
>
>
> Does anyone know of a screen on insulation material that can be used to
> increase flash over voltages? I would like to get a 2 or 3 mils of
> material.
> My other option is to have a laser cut layer of isolation but that could
> leave air paths under the material.
>
>
>
> Any other ideas welcome.
>
>
>
> Thanks,
>
> Bob K.
>

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