Henry,

Another important process/quality consideration relates to moisture
sensitive devices (MSD). Actually, the optimal process window for factory
conditions represent a balance between ESD and MSD controls.

As far as moisture absorption is concerned, the higher the temperature and
humidity the less time it takes for the components to exceed their critical
level. Remember that the maximum floor life stated on the MSD label on the
dry bags is based on ambient condition not exceeding 30C/60%RH. This floor
life is no longer valid when conditions exceed 60%, which is actually more
frequent then one might think. When the 60%RH limit is exceeded the maximum
floor life should be de-rated according to the IPC/JEDEC J-STD-033A, table
7.1. The de-rating varies based on the specific MS level and package body
thickness and it can be quite significant. For example the most common
package, which is a level 3, thin package (less than 2.1mm), will de-rate
from 7 days down to 1 day when conditions increase from 60% to 70%RH. Many
manufacturers are not aware of this fact and as a result they end up with
spikes in defect levels during the more humid season (in some countries this
is 12 months per year).

Francois Monette
Cogiscan Inc.



> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Henry Rekers
> Sent: Wednesday, October 02, 2002 3:24 PM
> To: [log in to unmask]
> Subject: [TN] Temp Humidity Control - Do you?
>
>
> How many of you out there are in full control of your
> temperature and humidity in your SMT facility?
>
> Do you track it?
>
> How tight do you control temperature?
>
> What do you use to control humidity?
>
> Any info would greatly help.  We are uncovering some very
> interesting challenges as we move towards 24-7 and I just
> want to find out what others are doing.
>
> Thanks.
>

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