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Subject:
From:
"lduso - Diamond-MT.com" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, lduso - Diamond-MT.com
Date:
Tue, 28 Feb 2017 18:27:14 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (278 lines)
That dots look fine, good coating around the hole. We use EZ-peel from
Caplugs by the way.

Are you using a rattle can or mixing it yourself?

On Feb 28, 2017 16:58, "Steve Gregory" <[log in to unmask]> wrote:

> Hi Phil,
>
> We've been using Shercon KD Kwiky Dot Discs which are supposed to have an
> acrylic adhesive:
>
> http://www.all-spec.com/Catalog/Adhesives-Sealants-Tapes/Tapes/Dots-Discs/
> KD00312-45075
>
> Those aren't the ones you are using are they?
>
> Steve
>
> On Tue, Feb 28, 2017 at 2:35 PM, Nutting, Phil <[log in to unmask]
> >
> wrote:
>
> > With our acrylic conformal coating I noticed a blooming effect around the
> > masking tape dots.  It turned out that the tape dots had changed from
> > acrylic adhesive to silicon adhesive.
> >
> > Phil
> >
> > -----Original Message-----
> > From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
> > Sent: Tuesday, February 28, 2017 4:19 PM
> > To: [log in to unmask]
> > Subject: Re: [TN] Baking before conformal coating
> >
> > I don't know what the heck is going on here, but try these links!
> >
> > Arrrrrrrrrgh!
> >
> > http://stevezeva.homestead.com/Conformal_dark_spots.jpg
> >
> > http://stevezeva.homestead.com/Conformal_dark_spots_close.jpg
> >
> > http://stevezeva.homestead.com/Conformal_dark_spots_
> > close_reflected_light.jpg
> >
> > Steve
> >
> > On Tue, Feb 28, 2017 at 2:14 PM, Steve Gregory <[log in to unmask]>
> wrote:
> >
> > > Oh shoot, I sent thumbnail links! Here try these:
> > >
> > > http://stevezeva.homestead.com/Conformal_dark_spots.jpg
> > > <http://stevezeva.homestead.com/Conformal_dark_spots_thumb.jpg>
> > >
> > > http://stevezeva.homestead.com/Conformal_dark_spots_close.jpg
> > > <http://stevezeva.homestead.com/Conformal_dark_spots_close_thumb.jpg>
> > >
> > > http://stevezeva.homestead.com/Conformal_dark_spots_close_
> > > reflected_light.jpg
> > > <http://stevezeva.homestead.com/Conformal_dark_spots_
> > close_reflected_light_thumb.jpg>
> > >
> > >
> > > Steve
> > >
> > >
> > > On Tue, Feb 28, 2017 at 2:07 PM, Steve Gregory <[log in to unmask]>
> > wrote:
> > >
> > >> Hi Doug, Lloyd and everyone,
> > >>
> > >> Here are some photos:
> > >>
> > >> Area under UV light (BTW, that's my Ray-O-Vac pet pee-pee detector
> light
> > >> I bought at Walmart):
> > >>
> > >> http://stevezeva.homestead.com/Conformal_dark_spots_thumb.jpg
> > >>
> > >> Close-up of area under UV light:
> > >>
> > >> http://stevezeva.homestead.com/Conformal_dark_spots_close_thumb.jpg
> > >>
> > >> Close-up of the same area under reflected light:
> > >>
> > >> http://stevezeva.homestead.com/Conformal_dark_spots_close_
> > >> reflected_light_thumb.jpg
> > >>
> > >> So you can see that the area is indeed coated. This is Humiseal
> 1B73....
> > >>
> > >> Steve
> > >>
> > >> On Tue, Feb 28, 2017 at 1:51 PM, Douglas Pauls <
> > >> [log in to unmask]> wrote:
> > >>
> > >>> Argggh Steve, we know ye to be a pirate anyways......
> > >>>
> > >>> I had the same question come to mind as Lloyd asked.  Pinholes or
> > >>> dewetting?  Pinholes can be due to moisture coming out of the board,
> > but is
> > >>> most often point sources of contamination, like droplets of oil or
> some
> > >>> other adulterating contaminant in the coating.  A picture would help.
> > >>>
> > >>>
> > >>> Doug Pauls
> > >>> Principal Materials and Process Engineer
> > >>> Rockwell Collins
> > >>>
> > >>> On Tue, Feb 28, 2017 at 2:20 PM, Steve Gregory <[log in to unmask]>
> > >>> wrote:
> > >>>
> > >>>> Hi all,
> > >>>>
> > >>>> I'm not trying to hijack this thread, but since we're talking
> > conformal
> > >>>> coating here, what could cause an acrylic to appear that there are
> > tiny
> > >>>> little fisheyes in the coating, but when you hold the board at an
> > angle,
> > >>>> you can clearly see that the area is coated. I know pictures would
> > help,
> > >>>> I'll see if I can get some....
> > >>>>
> > >>>> Steve
> > >>>>
> > >>>> On Tue, Feb 28, 2017 at 12:59 PM, lduso - Diamond-MT.com <
> > >>>> [log in to unmask]> wrote:
> > >>>>
> > >>>> > We do not pre-bake as an internal rule and never a complaint.
> > Obvious
> > >>>> > exceptions: We are washing or cleanliness testing the boards. Then
> > we
> > >>>> will
> > >>>> > bake them dry before masking and coating. Or the customer
> > specifically
> > >>>> > requires a pre-bake on the drawing. (I always then ask the
> question;
> > >>>> "How
> > >>>> > long after the bake do I have to coat them before they need to be
> > >>>> baked
> > >>>> > again?" Strangely, only a few have an answer for that.)
> > >>>> >
> > >>>> > I have visited many facilities that conformal coat and I have
> > >>>> witnessed it
> > >>>> > both ways but mostly on the "no pre-bake" side. One customer even
> > >>>> pre-baked
> > >>>> > their boards before coating with a water based acrylic.
> > >>>> >
> > >>>> > Lloyd Duso
> > >>>> > Plant Manager
> > >>>> > Diamond-MT
> > >>>> > (814) 535-3505
> > >>>> > www.Diamond-mt.com
> > >>>> >
> > >>>> > On Tue, Feb 28, 2017 at 2:39 PM, Douglas Pauls <
> > >>>> > [log in to unmask]> wrote:
> > >>>> >
> > >>>> > > Lee,
> > >>>> > > It Depends.
> > >>>> > >
> > >>>> > > We have one facility that has never baked prior to coating
> > >>>> application.
> > >>>> > No
> > >>>> > > evidence of any conformal coating related problems.  We have
> > several
> > >>>> > > facilities that bake religiously prior to coating application,
> > also
> > >>>> for
> > >>>> > > acrylic.  No evidence of any conformal coating related problems.
> > >>>> > >
> > >>>> > > I think the biggest factor is how much residual water you
> have.  I
> > >>>> don't
> > >>>> > > think your assemblies have to be bone dry before coating.  We
> do a
> > >>>> lot
> > >>>> > with
> > >>>> > > in-line aqueous cleaners, which have heated air knifes that
> remove
> > >>>> the
> > >>>> > bulk
> > >>>> > > of the water.  Now, there might still be some entrapment areas,
> > but
> > >>>> if
> > >>>> > so,
> > >>>> > > we find them and then blow out those entrapment areas with
> ionized
> > >>>> air.
> > >>>> > >
> > >>>> > >
> > >>>> > > Doug Pauls
> > >>>> > > Principal Materials and Process Engineer
> > >>>> > > Rockwell Collins
> > >>>> > >
> > >>>> > > On Tue, Feb 28, 2017 at 10:20 AM, Lee Hitchens <
> > >>>> > > [log in to unmask]
> > >>>> > > > wrote:
> > >>>> > >
> > >>>> > > > Hi all
> > >>>> > > >
> > >>>> > > > I've recently been asked about baking pcbs before conformal
> > >>>> coating and
> > >>>> > > > whether there is any quantified data on the effect on coating
> > >>>> > > performance.
> > >>>> > > >
> > >>>> > > > Does anyone know of any public studies on this or can shed
> some
> > >>>> light
> > >>>> > on
> > >>>> > > > its effectiveness beyond anecdotal experience ? I would be
> very
> > >>>> > grateful
> > >>>> > > to
> > >>>> > > > you on this.
> > >>>> > > >
> > >>>> > > > Best Regards
> > >>>> > > >
> > >>>> > > > Dr Lee Hitchens
> > >>>> > > >
> > >>>> > > > SCH Technologies is a Division of SCH Services Limited
> > >>>> > > >
> > >>>> > > > www.conformalcoating.co.uk
> > >>>> > > > Skype: leehitchens
> > >>>> > > >
> > >>>> > >
> > >>>> >
> > >>>>
> > >>>> --
> > >>>>
> > >>>>
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> > >>>
> > >>
> > >
> >
> > --
> >
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>
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