Hi Ray, The aspect ratios you mention are mostly for uVia technologies, and even that is being addressed to get to more layers. I've done some deisgns in the past using "mechanically drilled" (same technology as thru holes, same drills) .010" FHS holes. I've done boards going from layer1 to layer2; layer1 to layer3; and layer1 to layer5, all on the same board WITHOUT going to uVias. I've dealt with many fab shops that could do this, and the cost isn't outrageous either. I haven't run into a fab shops lately that's quivered at my designs. I like the technique much better than uVia applications, especially regarding costs. Hope this helps. Mitch ---------Included Message---------- > Date: Fri, 22 Jun 2001 08:14:27 -0700 > From: "Ray Humphrey" <[log in to unmask]> > Reply-To: "DesignerCouncil E-Mail Forum." <[log in to unmask]>, "Ray Humphrey" <[log in to unmask]> > To: <[log in to unmask]> > Subject: Re: [DC] Burried via hole > > A major concern for blind vias is the aspect ratio; typically, .7:1 for most > PCB fab shops that can do them. (Notice that's less than 1:1 compared to > 10:1 and greater for standard TH vias.) So, you will be using some very > thin prepreg between layers. If you also have controlled impedance in the > 50 -75 ohm range, it's a challenge. > > You can download or otherwise obtain the DFM manual from most fabricators. > Select the ones you will be considering to build your boards and become > familiar with what they can/cannot do. A good resource is the Resource > Center at Merix, http://www.merix.com/main_res.html. You should also > discuss your needs with the fab shop's tooling and engineering department. > > Best of luck! > > Ray > > > -----Original Message----- > From: DesignerCouncil [mailto:[log in to unmask]]On Behalf Of > Flatfield, Cadcam > Sent: Friday, June 22, 2001 2:35 AM > To: [log in to unmask] > Subject: [DC] Burried via hole > > Hi, > > I am looking for design specifications for blind and burried via holes. > Also am i looking for design specifications for flex and rigid flex. > > Thank you, > > Gerard Goossens > Flatfield multi print > Tel :0344-622556 > Fax :0344 613652 > > ----------------------------------- > Mail : [log in to unmask] > Website : www.flatfield.nl > ----------------------------------- > > ---------------------------------------------------------------------------- > ----- > DesignerCouncil 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 DesignerCouncil. > To set a vacation stop for delivery of DesignerCouncil send: SET > DesignerCouncil 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 > ---------------------------------------------------------------------------- > ----- > > --------------------------------------------------------------------------------- > DesignerCouncil 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 DesignerCouncil. > To set a vacation stop for delivery of DesignerCouncil send: SET DesignerCouncil > 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 > --------------------------------------------------------------------------------- > ---------End of Included Message---------- _____________________________________________________________ Tired of limited space on Yahoo and Hotmail? Free 100 Meg email account available at http://www.dacafe.com --------------------------------------------------------------------------------- DesignerCouncil 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 DesignerCouncil. To set a vacation stop for delivery of DesignerCouncil send: SET DesignerCouncil 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 ---------------------------------------------------------------------------------