Macintosh PCB Software FREE Re: [sdiy] Schematic toPCBproblems

[Happy Harry]

Ditto:

The part placement (both on the board, and in your mind before
running the first trace)... is critical to success. Screw what the
boss or customer thinks. I think first, route later.

What good is it to fill the screen with traces, all wrong and destined
to be erased ???

Good parts placement is 90% of the job.

H^) harry


>From: Jim Patchell <patchell at silcom.com>
>To: Grant Richter <grichter at asapnet.net>
>CC: Joshua Stephen Landau <jslandau at engin.umich.edu>,   
>synth-diy at dropmix.xs4all.nl
>Subject: Re: Macintosh PCB Software FREE  Re: [sdiy] Schematic 
>toPCBproblems
>Date: Tue, 04 Jun 2002 12:13:31 -0700
>
>     Flamed....not by me...I would say that is pretty accurate.  I probably 
>spend a
>bit more time doing schematic capture, but the board placement is right 
>on...I have
>clients that complain about the fact I spend more time on placing the parts 
>on a PC
>board than routing.  And the way I generally work it, placement is 
>itterative with
>the Schematic Capture...if changing the schematic will make the placement 
>better, I
>do it.  I have found if the rats nest looks like...a rats nest, it will be 
>hard to
>route.  Nice and clean is the way to go, if you can.
>
>     -Jim
>
>Grant Richter wrote:
>
> > This is sure to get flamed, but what the heck...
> >
> > Here is a schedule for an experienced layout person doing a 4x6 inch PCB
> > with 15 chips and 100 resistors.
> >
> > Schematic capture  2 hours
> > Error Checking     6 hours
> > Board Placement    6 hours
> > Routing            4 hours
> > Build 1st board    2 hours
> >
> > Total              20 hours
> >
> > Here is a schedule for an inexperienced board layout person doing the 
>same
> > board
> >
> > Schematic Capture  1 hour
> > Error Checking     0 hours
> > Board Placement    1 hour
> > Routing            48 hours
> > Build 1st board    48 hours
> >
> > Total              98 hours
> >
> > I know because both those people are ME.
> >
> > With CAD systems, if your schematic has errors, your board will have 
>errors.
> > You will save the most time by checking your schematic until your eyes 
>bleed
> > (a zero is not an O, and OUTI will not connect to OUT1). Then spend a 
>huge
> > amount of time improving the parts placement. After that you can pretty 
>much
> > sleep through routing, because an optimal parts placement will give you 
>the
> > shortest routing for every trace.
> >
> > Also route your ground nets first, then the balance of the power nets. 
>THEN
> > your signal traces. In practice, funky ground and power routing will 
>create
> > more problems then funky signal routing. Try to avoid running power 
>through
> > other chips pins. In other words, avoid using chip pins as vias for 
>power
> > nets. You may need to add additional decoupling to certain chips 
>(hotwire in
> > a series resistor and tantalum cap), and you can't do that if more than 
>on
> > chip is connected to the trace.
> >
> > > From: Joshua Stephen Landau <jslandau at engin.umich.edu>
> > > Date: Mon, 3 Jun 2002 23:57:34 -0400 (EDT)
> > > Cc: <synth-diy at dropmix.xs4all.nl>
> > > Subject: Re: Macintosh PCB Software FREE  Re: [sdiy] Schematic to 
>PCBproblems
> > >
> > > Speaking for myself, there's at least one beginner who would be *very*
> > > interested in routing lessons.  Sad truth is, at least at UMich, they 
>no
> > > longer teach PCB design to their electrical students.  So any help 
>that
> > > can offered, general practice, tips, design theory, etc, would be much
> > > appreciated.  If I'm the only one, offlist is fine, but I suspect 
>others
> > > on the list would benefit greatly.
> > >
> > > Josh
> > >
> > >> There are  lots of people on this list who could probably help you 
>get
> > >> started
> > >> in manual routing.  Start with some really simple project to get the 
>idea.
> > >> Then
> > >> if
> > >> you want to get an autorouter you'll be better equipped to deal with 
>it. I
> > >> can
> > >> give you some tips if you like (offlist) or if there are other 
>beginners we
> > >> could do a bit
> > >> of an onlist class.  It would probably benefit a lot of folks out 
>there...
> > >
> > >
>




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