Hi Roger, IPC 2221 part 3.2 and 3.21 refer to the need to review and establish the 'end product requirements', of which the 'specifications' would be a part, at the BEGINNING of any project or PRIOR to the Design phase. You do it exactly right, of course. Most of the designers I know that work on contractual basis provide a quote based on 'first pass' and charge by the hour for ANY deviation from the original design quote, including all changes thereafter. Sort of like the Earl Scheib "I will paint your car for 29.95.. 'BUT, in the fine print... if you want anything extra, you tack on the additional charges at the shop labor rate of 60.00 an hour.' Etc.. etc.. Otherwise you have the unfortunate experiences like the one you went through... I'm sure there are testimonials to that effect out there... I think as an engineer you are not so rare, there are other PCB Designers that have engineering degrees and do their own boards, too.. Bravo! Now if you can train someone to support you... there will be an increase your throughput.. instead of just being an "Army of one" - :) The Impedance question I'll leave to someone else.. I've been flapping by virtual jaw too much today already.. :) Bill Brooks -----Original Message----- From: Roger Gathright [mailto:[log in to unmask]] Sent: Monday, June 09, 2003 1:29 PM To: [log in to unmask] Subject: [DC] When to request specifications? When not provided up front! Hi everyone.... I was wondering at what point in the design cycle for a board layout is it appropriate to request specifications? AND: Should the specification for the Impedance to the Board house be in stack data, or Impedance value? To clarify the reason for the question: A recent layout (done as a favor for a friend) with his firm resulted in much rework due to several people making changes as work progressed. It was a fixed Price and Should have been renegotiated based on the changes, I know! I actually laid out the board seven times, with an additional five sessions of major rework. This board had a 14 pin equivalent density of 125 parts on 4 square inches. Almost all surface mount, and was impedance controlled. After much indecision the placement was approved and I did the first of many layouts. After the third engineer was assigned to "Shepard the board / circuit" into production reviewed it, and more major changes were made, and a faraday shield was added, with much rearrangement to connect it in place. I realize now, that my "Friend" was only trying to get off the hook. But the original questions remains! Oh yes, I am an Electronic Engineer, with experience in Emissions and virtually all phases of design and Fabrication and test. I also lay out almost all my OWN boards, and occasionally (Rarely) for a customer. For myself, I always have ALL requirements called out BEFORE starting any layout! Roger Gathright Sr. Project Engineer Astromation Company ---------------------------------------------------------------------------- ----- 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 ---------------------------------------------------------------------------------