Hi Virgil,

I'm curious to know why you feel that moisture is unlikely at this point.
Excessive moisture will typically cause similar cracks and delaminations
during reflow. A moisture-related problem is even more likely if you place
moisture-sensitive devices on the first side of the board and have a
significant delay prior to the second side reflow.

Do you know if these parts are classified as moisture-sensitive by the
manufacturer ? (i.e. do you receive them in sealed dry bags with desiccant
and a moisture sensitive label indicating the level of sensitivity ?). Keep
in mind that the maximum specified floor life must not be exceeded between
the time that the parts are first removed from their sealed dry bags until
the final reflow process. In addition, placing previously exposed components
in dry storage does not necessarily stop the clock of exposure time.

You could easily rule out the possibility of moisture induced defects by
baking your components for 48 hours at 125C prior to placing them on the
boards.

Good luck !
Francois Monette
Cogiscan Inc.
Tel : 450-534-2644


From: "Virgil Lenton" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, January 16, 2003 10:43 AM
Subject: Re: [TN] Cracking SOT-23


> I apologize for the vagueness in my original posting.
> This is what we know so far about this problem.
>
> - It does not appear to be Z-height related - nozzles are spring loaded
and
> we have double checked.
> - Breaks are complete breaks through the center of the body. Sometimes
> the 'lid' comes off, but most often they crack top to bottom right
through.
> - We have *not* explored the possibility of moisture, but at this pont we
> feel moisture is unlikely.
> - The components in question are all placed on pass 1. We havent yet
> checked to see if they are cracked before pass 2.
> - It is not always the same part, but always SOT-23.
> - The profile used is our 'standard' profile that has been used for about
3
> years.
>
> Regards
> Virgil
>

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