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November 2007

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From:
Sylvain Kaufmann <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Sylvain Kaufmann <[log in to unmask]>
Date:
Fri, 9 Nov 2007 08:48:52 +0100
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Hello Genny,
Here is my thought about it.

Baking receipt and maximum ratings are related to both moisture extraction needs and metallurgical limitations, if I well understood it; in this case the two only concerns I would think about are:
- Do I have any electrolytic capacitor that could have dry at such temperature for such time on my assembly? Half an hour at 135°C would certainly not be critical, otherwise 125°C for 24h would also be critical (general baking receipt), so I guess your answer to this question is no
- Is excess intermetallic growth a problem? Regular MSL rules state that you should bake your component for a maximum of cumulated 48h at 125°C related to excessive intermetallic growth and other factors I don't know of, so in your case, half an hour would not be critical from my point of view.

Regards
sly
S. Kaufmann

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Sylvain Kaufmann
CERN / European organisation for nuclear research
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Genny Gibbard
Sent: jeudi, 8. novembre 2007 22:17
To: [log in to unmask]
Subject: [TN] Higher bake

Let's say there was a board was in an oven being baked prior to reworking a component, due to the fact that there were MSL devices installed on the board.
It was discovered that the oven temperature was about 10C higher than it should have been, for up to half an hour.
Other than components that might show visible damage (ie a plastic connector melting some from the higher heat), would you be at all concerned about this???

My initial impression, if you can't see damage, they are probably OK.
It was only baking temperatures (135), and only for 1/2 hour, and these components are rated for/have seen much higher temperatures (albeit only for seconds or minutes) when going through a reflow cycle.

TIA for your responses.

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