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November 2002

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Tue, 12 Nov 2002 13:23:36 +0800
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Gottcha! Thanks Werner - and a good point to remember. I guess ramp rates
will have to come down to accommodate the thermal inertia, without
over-cooking other components - or we're going to have to come up with all
kinds of masking or shielding ("sun shade") requirements and techniques.

Thank goodness the lead-free zone hasn't expanded as far as Singapore yet
(except for US customers).

Peter



Werner Engelmaier <[log in to unmask]>    12/11/2002 12:20 PM
Sent by: TechNet <[log in to unmask]>

Please respond to "TechNet E-Mail Forum."; Please respond to Engelmaier

              To:  [log in to unmask]
              cc:  (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
              Subject: Re: [TN] profiling BGAs








Hi Peter,
You are right, 'the reason why one drills up into the central ball of a BGA
to place a T/C, is because it's these central contacts that generally
suffer
from insufficient heating owing to the shading effect of the overlying body
of the component.'
The question I answered was how to determine the temperature of a component
body. This will be even more important given the idiotic drive towards
lead-free solders, when solder reflow temperatures need to be higher and
thus
component temperatures as well. Thus, knowing the component temperatures
will
be even more important than now.

Werner Engelmaier

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