You've covered it pretty well. Getting "down" to very small and fine pitch device types often does
exceed flex circuit limits. I won't get into the tolerance factors as the opening and tooling
inconsistencies you have stated make for wide variations may often overcome the device size alone -
notwithstanding solder termination area requirements. Another important factor, not mentioned, is
that of material thermal charactestic variabilities adding to the mix.

One costly (always a relative term) suggestion I would make is to use rigid/flex where small, fine
pitch device types are required. This provides an obvious solution as you now have a "normal" PCB
surface where component placement is concerned and flexibility to fit or function where needed. Will
it fit or flex where you want is another story.

Earl Moon

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################