Parylene works rather well for an insulator. I have had customers send
high-power devices purely for that reason. That fact that it does so much
so thin and it is virtually pin-hole free is usually why it is chosen.
Cleanliness is important but nothing more than normal IPC-650 cleaning is
required. Most of the product we coat is washed sufficiently before it
arrives here. Of course, we use adhesion promotion as well.
It is definitely not the best option for every application but it does come
in handy and can be quite economical.
Lloyd Duso
Plant Manager
Diamond-MT
(814) 535-3505
www.Diamond-mt.com
On Mon, Mar 20, 2017 at 3:57 PM, Theodore J. Tontis <
[log in to unmask]> wrote:
> Bob,
>
> I have not heard of a PCBA coating which is UL approved as an electrical
> insulator, but I am not a coating expert. I do know that coatings have
> electrical insulating properties but I wouldn’t trust them to protect
> myself or my equipment.
>
> I have not worked much with the parylene coatings but do know the entire
> assembly has to be cleaner than clean so the coating to effectively adhere
> to all the surfaces. This means more process steps, more handling, more
> scrap and more money.
>
> Whatever process you chose to provide the insulation, there will be some
> variation and failures. If possible, redesign the transformer or PCB and
> save yourself future headaches. The results will be more consist and in the
> long run, be less costly. I do not know what the end use of the product is
> but, if there is potential for the end user to be shocked or risk of
> equipment damage, you are better off choosing the redesign path. One
> failure in the field could have horrible results.
>
> Ted T
>
> -----Original Message-----
> From: Robert Kondner [mailto:[log in to unmask]]
> Sent: Monday, March 20, 2017 12:39 PM
> To: 'TechNet E-Mail Forum' <[log in to unmask]>; Theodore J. Tontis <
> [log in to unmask]>
> Subject: RE: [TN] WG: [TN] Screen On Insulation
>
> Hi,
>
> Is the use of parylene NOT recommended as an insulating layer? It sure
> has a high dielectric strength.
>
> Does anyone have comments? I knid of like the parylene ide as it gets into
> all the itty bitty places.
>
> Bob
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Theodore J. Tontis
> Sent: Monday, March 20, 2017 12:38 PM
> To: [log in to unmask]
> Subject: Re: [TN] WG: [TN] Screen On Insulation
>
> Coating is not to be used as an insulator. There is no guarantee that
> consistent coating thickness can be controlled meaning the ability to
> insulate/electrically isolate cannot be controlled.
>
> If the concern is the planar core shorting to the board, ask the supplier
> to place kapton tape under the core.
>
> All of our planar transformer drawings call out kapton on the bottom of
> the core for this very reason.
>
> Ted T
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
> Sent: Monday, March 20, 2017 11:06 AM
> To: [log in to unmask]
> Subject: Re: 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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