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October 2000

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Subject:
From:
Darrel Therriault <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 13 Oct 2000 07:58:45 -0700
Content-Type:
text/plain
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text/plain (58 lines)
Charles,

Good question.  I just recently had some boards baked at 125c for 24 hours
to do BGA replacement
only to find when they came out of the oven that the shrink wrap on several
electrolytic caps had
cracked and peeled.  I found the upper operating environment for the caps
was stated at 85c, although I
don't believe that means it is the max temp they can stand.  The spec sheet
did not indicate a max
temp for prolonged periods (e.g. bake time) other then to provide an
assembly thermal profile, which had
ramp/dwell time at around 150 seconds and max temp around 260c for 30
seconds.

I hope I missed something in the data sheet that will shed some light on
this spec, as we rework BGAs
often and I don't want to be destroying or degrading anything on the board.

Regards....DT



At 09:34 AM 10/13/00 -0400, you wrote:
>Hello TechNetters!
>
>I am interested in the baking parameters being used for assembled PCBs
>prior to BGA rework in order to reduce risk of moisture-related damage.
>
>Component vendors often suggest 125'C for 24 hours, but this is based on
>component level requirements for drying out unmounted components.  I
>have heard of baking assembled PCBs at 90'C for 48 hours.
>
>Your input is most appreciated.
>Charles.
>
>--
>Charles Elliott, P.Eng.
>Physical Technology Engineer, Alcatel CID
>[log in to unmask]
>
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