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Reply To: | TechNet E-Mail Forum. |
Date: | Tue, 24 Feb 1998 12:07:46 -0800 |
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We bake for 4 hours at 125 degrees C. We must then either vacuum pack
or use within an hour. This is working wonderfully. No problems. We
bulid to Class II.
Thanks,
Kathy Palumbo
> ----------
> From: BOB HAYNES[SMTP:[log in to unmask]]
> Sent: Tuesday, February 24, 1998 9:43 AM
> To: [log in to unmask]
> Subject: [TN] [ASSY} Prebake
>
> 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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