Paul,
For point number one, wouldn't you qualify it much the same way you would a big BGA with a PCB base layer?
For point two, see a paper by David Hillman et al from this year's APEX.
Bev Christian
Research in Motion

-----Original Message-----
From: Paul Brown [mailto:[log in to unmask]]
Sent: March 8, 2004 7:36 AM
To: [log in to unmask]
Subject: [TN] Questions concerning piggy-back PCBs and SMD sardine
mounting


All,

I am looking for prescribed procedures and guidelines for the following modifications to an existing PCBA :

* Mounting a piggy-back PCB (probably about 25mm x 25mm) over the space left by two DIL ICs being replaced.

* Sardine mounting two SMD capacitors rather than piggy-back mounting (if you can't guess, sardine mounting is with the smallest faces on the PCB surface, largest faces together (legend out in both cases).

I do not see either of these techqniques mentioned in the tables of content that I have downloaded for IPC-7711 and IPC-7721.

I am particularly interested in the re-qualification requirements that would be necessary, such as shock, vibration, acoustic, thermal cycling.

Regards,
Paul.

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