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April 2002

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Subject:
From:
"FOX, Ian (York Rd)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 9 Apr 2002 08:37:18 +0100
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text/plain (67 lines)
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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