Using DIPS in the old days was fine for EIC's and area calculations. But with SMD being predominant you must consider fan-out, or fan-in. Using fan-out as worst case you can typically add 30% to the area of an soic type part or 100% to a chip cap (if both pins have vias). Also, for DIP's we typically used only one side of the board. Now both are common practice. But you still have to add some fudge factor for fan-out/fan-in. Let's NOT get into a discussion of blind or micro-vias. It would hurt ;). 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: Brooks,Bill [mailto:[log in to unmask]] Sent: Friday, March 02, 2001 1:15 PM To: [log in to unmask] Subject: Re: [DC] Board Density Factor Hi Jeffrey, This is an interesting topic... I remember using the 'density factor' back when it actually meant something. When the 14 and 16 pin DIP was the predominant package size used on most PCBs we did calculate 'equiv. IC's per square inch' as a measure of design density. The way you would do that is see how many parts, (i.e. resistors, caps, diodes, etc..) would fit into the same area as a 14 pin dip. This would give you an equiv. IC value for your discretes. Then you divided the number of 'virtual' or equiv. IC's you had and divided them into the square in. of the board surface. This would give you a value to compare between designs to give you an idea of how difficult the board would be to lay out. Today... I think you could do the same with 0805, 1206, sot, sioc, etc. and come up with an equiv. value and it would correlate with the old density factor fairly well. Of course, we can push the envelope more now because of improvements in processes in manufacturing... but anyway, that's how we used to use the density factor calculation when I was doing hand tape and Mylar.. in the early 70's and 80's. Bill Brooks PCB Design Engineer DATRON WORLD COMMUNICATIONS INC. 3030 Enterprise Court Vista, CA 92083 Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510 mailto:[log in to unmask] IPC Designers Council, San Diego Chapter http://www.ipc.org/SanDiego/ http://home.fda.net/bbrooks/pca/pca.htm -----Original Message----- From: McGlaughlin, Jeffrey A [mailto:[log in to unmask]] Sent: Friday, March 02, 2001 9:44 AM To: [log in to unmask] Subject: [DC] Board Density Factor I was recently ask to explain the board density factor calculated by our layout package. It gave a factor of 0.1 sq. in./14-pin DIP. I translated that to be 140 pins per square inch so that it made more sense in the two sided surface mount arena, but was left wondering if there was a better way of figuring board density. What are you using and why? Jeffrey A. McGlaughlin, C.I.D. Sr. PCB Designer Battelle Memorial Institute Columbus Ohio [log in to unmask] ---------------------------------------------------------------------------- ----- 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 -------------------------------------------------------------------------------- - --------------------------------------------------------------------------------- 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 ---------------------------------------------------------------------------------