Marie-Josie:

IPC-SM-786A indicates that, unless otherwise specified by the component 
manufacturer, bake the units shipped in high temperature shipping media 
for 24 hours at 125C. Units packed in shipping media which will not 
withstand these temperatures may be placed in an oven at 40C (+5/-0C) for 
192 hours at <5% relative humidity. (It is critical that oven humidity be 
controlled at this low temperature.)

The time required to desorb moisture down to the target level can vary 
from one week to a month depending on the starting moisture level and 
package thickness.

Please keep in mind that the growth of oxides and lead finish 
intermetaalics are the main causes of lead finish 
degradation, which leads to poor solderbaility. These are thermally-activate 
processes. Therefore, limiting the time at 125C is curcial to maintaining 
good solderability. Also, take care to ensure that outgassing of the 
shipping and carrier media (e.g., trays) does not impact solderability. 
Verify use temperatures of carrier materials with the componen supplier 
before using the carriers in high temp applications.

I believe Jedec specs call for similar treatment.

Mike Buetow
IPC Staff
2215 Sanders Road
Northbrook, IL 60062
P: 847-509-9700, ext. 335
F: 847-509-9798
[log in to unmask]

On Thu, 22 May 1997, Marie-Jose Lambert wrote:

> Hello,
>            I would like to know if anyone has a baking procedure for 
components that have absorbed moisture (QFPs).  We are thinking of baking 
them in an oven under vacuum or nitrogen but we are not sure for how 
long and at which temperature we would get the best results.
> 
> Any information would be greatly appreciated.
> 
> Thank you.
> 
> Marie-Josée Lambert
> B.Eng.
> E-mail: [log in to unmask]
> 
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