You mean under black light there is a dark spot like a "de-wet" area?

Lloyd Duso
Plant Manager
Diamond-MT
(814) 535-3505
www.Diamond-mt.com

On Tue, Feb 28, 2017 at 3:20 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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