======== Original Message ======== I am looking for some helpful hints in pursuing a design using Orcad Layout 7.10a with Blind and Buried Vias. This particular design is densely populated with SM components on Top & Bottom. Probably an 8-10 layer board ( 2 planes ) This will be my first shot at using B&B vias and I don't want to get too carried away ( 5 or 6 different drill tapes ) . I understand that with Orcad, I can just define several vias, assign them to the nets, and the Router will select The appropriate via as needed. Are there any recommendations/suggestions as to how deep the blind vias should go? How many layers should the buried vias traverse? Are there "good" strategies to approach the definition of the vias? Or is this strictly design dependent and 'I'm on my own'? How about recommendations from the fab point of view ? Thanks.......... MARK RADLEY Rick Pray & Associates 96 Lock Street Port Crane, New York 13833 607-648-8594 (voice) // 607-648-2535 (fax) [log in to unmask] www.rpaeng.com ======== Fwd by: Richard MacCu ======== From a fab standpoint, the easiest/cheapest way to do blind/buried vias is to limit the layers they traverse to two if possible. As you add more layers you must pay for extra lamination steps to build up the padstacks you require. It is relatively easy to create buried vias. Blind vias are more difficult whether controlled depth drilling or some other blind via technique is used. Each subsequent lamination can impact board price as much as 30%. As far as definition of vias. Having separate drill drawings reflecting the via locations and a table showing each drawing's relationship is usually easy to interpret. If you use a particular supplier I would suggest having one of their Manufacturing Engr. types evaluate the docs on a preproduction basis to get their input. Good Luck