Per the results of a DOE, we are not baking anything less than 12 layers.

>>> BOB HAYNES <[log in to unmask]> 02/24/98 11:43am >>>
Ladies and Gentlemen,

This issue was the subject of a lively amount of discussion a couple
of years ago. The question has once again come up in the company I
work for so thought would get the opinion of others. There does not
seem to be any exact guidance in any of the IPC publications that I
am aware of.

When we worked to MIL-C-28809B Par. 3.5.7 left no doubt of what
to do. One was required to bake at 105 Deg. C for an unspecified
time to remove absorbed moisture. Also if the time interval between
baking and soldering was greater than 8 hours you were required to
rebake.

My company set this unspecified time as  12 hours (overnight) and has
continued to use the same process even though most of our production
is now commercial. Also most of the assembly is now surface mount
and
when MIL-C-28809 was written (1988) most assembly was TH.

What are other assembly houses doing baking or not baking?

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