Nick,

are you placing the new BGA on paste or do you use flux only (paste rework
flux)?
If on paste, check the insertion pressure (or Z). This could give shorts.

Also, do not rely on transferring profiles from one BGA to the other. And I
mean between different pin counts or different BGA packages. There are never
the same!

Do you see sloder balls on the VIAs on the opposed side, under the BGA? If
yes, you have an overheating.
Do preheat the board during rework? Ten layers is something!

I'm not familiar with your rework station, but on mine the best way to
develop a profile is to place the thermocouples on the BGA you want to
remove and partly copy the results on the profile for reflowing the new
component.

Hope this helps, Ioan

> -----Original Message-----
> From: Nick D'Onofrio [SMTP:[log in to unmask]]
> Sent: Tuesday, July 13, 1999 9:52 AM
> To:   [log in to unmask]
> Subject:      [TN] BGA rework
>
>   I'm wondering if anyone can assist us or offer any advice to deal with
> our
> little dilemma. Reworking BGA's is fairly new process for us.
>   I'm attempting to rework a 313 contact plastic BGA on a 10 layer board.
> I end up
> having either cold solder or shorts between contacts. We are using a
> SNIPER
> SMD-7007 rework station at 375 F degrees. We have used the same heat
> profile our
> other ceramic BGA's without having any problems..
>
>   Any comments would be greatly appreciated.
>
> Regards,
> Nick D'Onofrio
> Quality Assurance