Keep in mind Mark, MOT is NOT equal to Tg.
Tim Reeves
-----Original Message-----
From: Mark Hargreaves [mailto:[log in to unmask]]
Sent: Wednesday, May 14, 2003 12:37 PM
Subject: Re: Hot Boards!
Additional Comment-
IPC-4101 sheet 24 is a higher temp FR4 spec (Tg minimum 150 C).
In addition, the spec sheet for the FR4 we use indicates "typical Tg" of 175
C, which equals the rating of your component.
Mark
-----Original Message-----
From: Mark Hargreaves [SMTP:[log in to unmask]]
Sent: Wednesday, May 14, 2003 2:59 PM
To: [log in to unmask]
Subject: Re: [TN] Hot Boards!
Carl and Mike,
Far as I know, 130 C is the highest continuous operating temperature
rating
that UL will give any FR4 material.
Regards,
Mark
-----Original Message-----
From: Mcmaster, Michael [SMTP:[log in to unmask]]
Sent: Wednesday, May 14, 2003 2:30 PM
To: [log in to unmask]
Subject: Re: [TN] Hot Boards!
Carl
You got the 120C number from Table 4-1 in IPC-2222, right?
What's
the minimum dielectric thickness in the board? It's also important
to note
that this chart just lists FR4 and doesn't have a separate listing
for
Higher Tg materials. I think this is why they include footnote 6
"Other
materials in the same classification with higher operating
temperatures may
be available." You want to avoid low Tg FR4 materials since you'll
be very
close to that transition point. The best thing to do is find out
from the
laminate manufacturer what the maximum continuous operating
temperature for
their material is. This information is not usually on the standard
data
sheets but it is available.
One other thing you need to watch out for is to make sure
you're
fabricator has UL recognition for high enough Maximum Operating
Temperature
(MOT) for the materials used in this board. It's not enough to ask
for
flammability. You also need to specify a specific MOT if you want
it and
you probably want at least 130C for this board.
Mike McMaster
RF Product Engineer
Merix Corporation
503-992-4263
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