All, At Harris we mount PWB to metal plates very often. Two methods are used. 1. Blind vias for all non GND connections. 2. Dimpling the metal plate where the non GND connections are is usually the least expensive method. Hopefully the PWB will not change and you won't have to remake the plate. We don't generally do controlled depth drilling. Most fabricators are not very good at it or price our boards to fund their research. Use the KISS method for all designs when possible. The second approach I mentioned above satisfies this. Regards, Jerry Schwartz, CID IPC Certified Interconnect Designer "May the Schwartz be with you" Jerry Schwartz, CID Designer 3 Harris Corporation GCSD Voice (321)-727-5474 P.O. Box 37, MS 1/9843 Fax (321)-729-5990 Melbourne, FL 32902-0037 Pager (321)-690-9797 mailto:[log in to unmask] http://harris.com -----Original Message----- From: David Cary [mailto:[log in to unmask]] Sent: Thursday, January 04, 2001 6:58 PM To: [log in to unmask] Subject: Re: [DC] Controlled depth drilling Dear Roy Beckman, I think I heard about something like this before ... ah, here it is. _Surface-Mount Technology for PC Boards_ book by James K. Hollomon, Jr. p. 317 <blockquote> <p> ... NASA's Jet Propulsion Lab ... One circuit in particular was fascinating. For a spacecraft, it was a relatively large card. And, it was fully planar mounted with single-side population. The back side of the board was bonded to a metallic plate. The circuit was part of the electronics of the Voyager space probe. ... the metallic backside of the substrate was used as an outer skin of the spacecraft, as well as a support and a heat sink for the electronics. Therefore, surface mounting of the components was a must if they were to achieve a smooth hole-free skin for the spacecraft. </blockquote> I wish I knew where to get more details on the Voyager space probe. Maybe Andrew J Jenkins <[log in to unmask]> could help ? You also might look into "blind vias". ... One of our board shops has suggested an alternative strategy to handle through-hole vias for a PCB mounted on a flat metal plate. They suggest that we remove the bottom pads on all non-ground vias and then they will drill the plated holes out to a depth of 0.010". (The finished hole sizes for these vias are 0.012" and 0.018".) The previous strategy was to drill holes in the mounting plate at the via locations. Has anyone had any experience with this scenario? Can you recommend any board shops that do this? How reliable are the vias after this drilling? Thanks for your feedback, Roy Roy H. Beckman, C.E.T., C.I.D. Senior PCB Designer ... -------------------------------------------------------------------------------- - 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 ---------------------------------------------------------------------------------