Buried vias should only be used where the density of the board justifies their additional cost. In general buried vias allow the board to be made with fewer layers but it is like adding additional double sided boards to the build cycle. The fabrication losses on the via layers are like the losses on double sided boards and are very dependent on the lines and space widths chosen. They are helpful if Z axis expansion is a concern and if circuit run lengths are critical they allow interconnection without returning to the board surfaces. Once laminated the losses are just like a comparable multilayer for the continuation of processing both at fabrication and assembly. We once had many designs using them but found our fabricator supplier base to prefer added layers to buried vias as capacity in their shops plus dollar return per square foot processed are important to them. It is like you take a multilayer shop and ask it to run double sided boards mixed in with the normal product. The drill and plating time is used up and they do not get the dollar return for it. Plus it seemed like when we had a internal fabrication shop and made buried via boards you were always short vias when you scheduled the lamination area and had to wait for them to be made. ---------- From: [log in to unmask] To: [log in to unmask] Subject: Users/designer of buried via product Date: Monday, September 16, 1996 1:10PM I am interested in obtaining any information from companies which have designed and used printed circuit boards with buried via construction. Specifically the success or failure of such designs, yield loss at the board shop and assembly levels. Thanks in advance for your advice. Jenni Marcy Sr. Sourcing Engineer Storage Technology Corporation email address:[log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************