Phil

What is your end application?

Leaving moisture in the board / assembly can lead to "milking or blooming",
a slight matt finish or milky appearance to the coating. This would be a bad
thing. Baking before coating, you could happily expose them to lower temps.,
provided that you increase the air movement over them as this will permit a
reduced drying time. e.g. 80 degC + >~ 2 M/sec air flow should work well,
maybe 10 to 15 minutes, but it will depend upon the geometry of the
assembly.

We have plenty of customers who clean and coat within 20 minutes or less,
without pre-baking - including automotive high-rel.

Regards Graham Naisbitt

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> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Phil Nutting
> Sent: 08 April 2002 17:13
> To: [log in to unmask]
> Subject: [TN] Bake before Conformal Coat
>
>
> Good day, Technet
>
> After reviewing past threads regarding baking boards before
> conformal coating I come up with quite a varied selection of ideas.
> I found 1 hour @100°C, 4 hours at 150°C, and 4-5 hours at 125°C.
> My design engineer is concerned about the boards being exposed to
> this temperature for an extended time. Yes, in the wave solder it
> sees much higher temperatures... for a short period of time.  Our
> aqueous wash system dries at about 65°C for 20 minutes.
> Our product normally is tested to 40 - 50°C depending on the
> customer needs.
> The past threads suggested raising the temperature above 100°C to
> "boil off" any remaining water.
>
> Can this time/temperature be narrowed down any?
>
> And if we use a lower temperature are we possibly trapping moisture?
>
> How will the reliability be affected by these elevated temperatures.
>
> Thanks in advance,
>
> Phil Nutting
>
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