Not detracting from Steve's needs but these very large high layer count boards have been around awhile. Not blowing my horn, but did Amdahl MLB's first in the early 70's as Multi Chip Carrier (MCC) types for the first main frames by Gene Amdahl but later replaced by 10"x10" ceramic substrates supporting chip carriers with cooling towers and manifolds carrying water as the coolant. Cray used 52 layer boards early on in their super computer development and beyond. The density years ago and today, as I marveled working there, is almost beyond belief especially considering the incredible interconnect, to the outside world, system using current induced flex connections on 10 mil centers. A really good engineer did that and is now a damn manager but still highly capable. Bare boards cost $100K. Assembled a bit more. Yikes! Involved in recent Cray 42 layer development boards (we had to have a rework plan as well) for MCM's with 3400 I/O's and "normal" 1200 I/O CCGA's. The MCM's are cooled using the fruoronert stuff used in previous designs but now manifolds deliver coolant as vapor much as in older vapor phase reflow processes. You should see the new system plans. They're almost like the "chunnel" connecting Britain and the continent. Did a 60 layer type but all through hole designed to replace 24 layer boards with wire wrap pins and wire above surface. The attempt was to eliminate the wire wrapping by putting it all internal to the board and eliminate the wire wraps. Missles still flying - only when fired of course. Conversion from through hole to SMT rare for such large high layer count boards. Usually start out and stay surface mount. Has to be done considering high I/O count and all the electrical performance, impedance and all, requirements to be met. Actually somewhat simple but requiring lots of layers and careful design, fab process, and assembly management. Just a few doing it. Damn fun, what? Moonman --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------