Hi Bob,
Glad to hear you are not corresponding from the 'other side'.  I was
reluctant to reply on jumpering BGA's because I had hoped some one had a
better way, like the application of a liquid, conductive trace.  Maybe not.

What I did was to actually use 30 Ga. magnet wire and route the jumper
between solder balls.  I performed this under a microscope and epoxy tacked
the jumper at various places, taking care to keep the epoxy from the solder
balls.  The BGA was a 1.27 mm pitch, 313 pin PBGA.  After a few tries, it
took me about 5 minutes to complete one jumper.  I have no idea what this
would do to the reliability of the assembly, never did any thermal stress
testing.  Fortunately I have never had to actually use this trick.   This
would obviously not work with the  0.8mm and 0.5mm pitches now being used.

Jim Kittel

> -----Original Message-----
> From: Bob Vanech [SMTP:[log in to unmask]]
> Sent: Friday, August 13, 1999 5:04 AM
> To:   [log in to unmask]
> Subject:      [TN] Outsourcing of Conformal Coating
>
>   Hi all...
>       Happy, happy Friday..I'm above ground and typing..
>   that's good! I still have not had any takers on the
>   incorporation of jumpers as related to BGAs. Maybe
>   next week?? ;->
>        However, I have a new concern. We are looking to
>   out-source the conformal coating of our assembilies on
>   our new product. We have two part numbers in low
>   quantity, prototypes at this time, that need to be
>   coated. However, our assembler hasn't done this before
>   and doesn't what to start. His other customers have
>   never required c/c on product. So, is there someone
>   out there in TN land that has a lead?? Thanks in
>   advance and have a great weekend.
>
>                                  Regards,
>                                            Bob
>   Bob Vanech
>   BVAN Enterprise
>
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