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Reply To: | TechNet E-Mail Forum. |
Date: | Tue, 9 Apr 2002 08:37:18 +0100 |
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If you carry out weight loss trials you will find that temps above 105 degC
and dwells of approx 4 hours are required to fully remove moisture from
saturated PCB's, but in practice 2-2.5 hrs is usually sufficient to dry a
board prior to coating. These times and temps will not impact on the
reliability of product.
Ian Fox
TRW AS
-----Original Message-----
From: Phil Nutting [mailto:[log in to unmask]]
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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