Dear Colleagues: Currently, I am assigned for the backplane development of a new project, occasionally, I am told that the 'via' is not permitted to put on in the whole backplane. I wonder much that on what considerations the inhibition is based. As a high frequency engineer, I surely understand that the via will cause transit effects on the high-speed lines, however, there are still many signal lines merely running with low frequency, say, some control signals. If this inhibition is wholly, the possible factor I can think about is the limitaion of manufacturing capability. After all, for a backplane with 4.5~5mm thickness, is it possible to use common via or even 'blind vias'? If the 'vias' are totally not allowed to be used, large space will be wasted. Appreciate for your possible echo. C.-H. Huang ################################################################ DesignerCouncil 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 DesignerCouncil <your full name> To unsubscribe: SIGNOFF DesignerCouncil ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################