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August 2005

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Subject:
From:
Steve Hodge <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steve Hodge <[log in to unmask]>
Date:
Thu, 25 Aug 2005 08:21:29 -0600
Content-Type:
text/plain
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text/plain (58 lines)
Loan, are you talking solder mask blisters or de-lamination blisters. No
matter which condition, a 250 C excursion or 2 should not produce a problem
with mask or lamination.


At 08:18 AM 08/25/2005, you wrote:
>Hi Technos,
>
>wanted to start a pilot run, but the first PCB that we soldered ended up
>full of blisters when it came out of the oven. It is a 6 layers, full
>ground and power planes, about 6"x7", not a high density one, pretty light
>stuff on it, the toughest part is a transformer which needs a little more
>heating. The profile peaks at 250C on the PCB itself and the PCB is made
>out of FR4, Tg 170.
>
>I said to myself that it must be humidity, so I baked 1 board, 8H @ 125C,
>and passed it through the reflow again. Same blistering, almost to the
>same extent. Then I took a totally different PCB that was hanging around
>on my desk for about 3 months, reflowed it at 250C and got just a tiny
>blister, probably due to humidity this time.
>
>The questions I have are:
>
>is 250C too much for a properly manufactured PCB?
>
>If it's not the humidity what else could it be?
>
>Any other test that I could do to get a better idea of the root cause?
>
>Thanks,
>Ioan
>
>
>
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