This is a subject close to my own heart. Myself and my colleague often get hassled to put a time on a particular job and we have a decision to make - tie yourself to a date and be responsible for any failiure to meet deadlines or over estimate and stand the chance of other less knowledgeable people jumping to conclusions about your abilities as a PCB layout engineer! Seven times out of ten the "over estimate" turns out to be a more realistic estimate than at first thought. So, more often than not, it turns into a game of chance. Not a particularly favourable situation. Any, more experienced designers', input/advice on estimating job duration would be a Godsend.....! > -----Original Message----- > From: Matthias Mansfeld [SMTP:[log in to unmask]] > Sent: Thursday, August 27, 1998 4:52 PM > To: [log in to unmask] > Subject: [DC] How to estimate the time and place needed for a layout? > > help..... > Dear colleagues, > > I just work at a layout that is one of these layouts which > need much much more time and trouble than initially > estimated. I hope I'm not the only one who knows this problem. > > My question is: Are there any good thumb rules for a good estimate in > advance how long it takes to make a layout for a given schematic/ > partlist/ mechanical constraints drawing and how many layers are > necessary? I get usually a schematic and mostly a partlist and with > these informations I must make a good estimate for my customer how > much time it will take and (depends on time indirectly) how much cash > I want. The customers want the estimate ASAP, that means, I have not > much time to check out placement/routing density, the necessary number > of layers etc. And later it ends up with two layers more than the > customer wants to pay for and a lot of unplanned, unpaid night > sessions on my layout PC to get it ready in time or only few days > late. > > There are in IPC-2221 3.6.2 "Feasability Density Evaluation" (old > IPC-D-275 : 5.1.1) some calculations based on the size of the parts. > Is this good usable for determining how much routing area > is available? Has anybody any additional thumb > rules which consider e.g. the electrical structure > (many address/data buses across the board or only analog circuits with > mostly short point-to-point connections) or SMD parts pitch (can I > route between the leads or is the top layer really blocked by 0.5mm > pitch rows, as it is now with my actual nightmare layout - customer > wants 4 layers only with two of them Vcc and GND planes and no routing > - thus I have in reality only one and a half layers effectively for > routing :-( )? > > My dream would be an easy formula which says exactly, how routable is > the board, how many layers are necessary , and how much time/cash > needs the layout. > > Thanks, regards > Matthias Mansfeld > ----------------------------------------------- > Matthias Mansfeld Elektronik > * Leiterplattenlayout, Bestueckung > Am Langhoelzl 11, 85540 Haar; Tel.: 089/4620 093-7, Fax: -8 > Internet: http://home.t-online.de/home/matthias.mansfeld > > ################################################################ > DesignerCouncil E-Mail Forum provided as a free service by IPC using > LISTSERV 1.8c > ################################################################ > To subscribe/unsubscribe, send a message to [log in to unmask] with > following text in the body: > To subscribe: SUBSCRIBE DesignerCouncil <your full name> > To unsubscribe: SIGNOFF DesignerCouncil > ################################################################ > Please visit IPC's web site (http://www.ipc.org) "On-Line Services" > section for additional information. > For technical support contact Hugo Scaramuzza at [log in to unmask] or > 847-509-9700 ext.312 > ################################################################ ################################################################ DesignerCouncil E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE DesignerCouncil <your full name> To unsubscribe: SIGNOFF DesignerCouncil ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################