Hmmm, that's interesting. I've never heard anyone mention this subject
before.
If I DID have the time and inclination to try this, how big would the hole
need to be? Some of our BGAs have a center section of ground connections,
but there is a space off to the side before it gets to the real stuff. Can
the hole or holes be  off-center?


                -----Original Message-----
                From:   Dom Bragge [mailto:[log in to unmask]]
                Sent:   Wednesday, August 25, 1999 7:45 PM
                Subject:        Re: PCB designs using BGAs

                On Wed, 25 Aug 1999, Bob Walker wrote:

                > I'd like to know how many designers provide an unplated
hole under each BGA
                > component in a design, so that a thermocouple can be
placed to monitor
                > temperature. I'm thinking of doing this in all of my
designs to help make it
                > easy to create a temperature profile on a new design. Do
you use more than
                > one hole or is one sufficient?

                We don't design a hole in. We just sacrifice a board to get
it right (with
                a dummy bga component). This gets us pretty close, pretty
quickly.

                It saves having to design that hole in for all boards.


                --
                Dom Bragge      (VK2JNA)   Lucent Technologies (SAS)
                Senior PCB Designer(R&D)   16 Smith St Chatswood NSW 2067
                Tel: (+61 2) 9935 5792     AUSTRALIA  [log in to unmask]
                Fax: (+61 2) 9417 3862      E-:-I  http://www.jna.com.au