--- In
Homebrew_PCBs@yahoogroups.com, "ballendo" <ballendo@y...>
wrote:
> Stefan,
>
> Mariss Friemanis of Gecko drives mentioned some good information
> about how he lays out his SMD VERY densely populated drives. It
> involved some "strange" values for the layout grid, and included
soem
> thought about where to run vias and ancillary parts...
>
> Un fortunately, I'm not sure where I filed it. But he's known to be
> quite helpful, and hangs out at several groups including the
> electronics 101 group that I think belongs to our list owner here?
correct, it was on Electronics-101
Here it is as a copy
"quote from post # 5905 from Electroncis-101
Re: PCB design - good practices?
Bret,
I use ACAD for PCB layout design and a program called Autogerb to
convert the results to a gerber format (.gbr).
You may want to use a .008333" grid. If you use thru-hole parts, (DIP
ICs), then use .058333" dia. pads with a .032" dia. plated-thru holes.
Make the traces and spaces .008333" wide. This will permit you to
sneak two traces between IC pins, (.100" between pins, .041666" space
between pads, leaving room for .008333" space, trace, space, trace
and space.
Use 45 degree turns instead of 90 degrees for traces.
Inspecting finished (stuffed) circuits is easier from the bottom.
Place most of your circuit interconnect traces there. Use the top
side for power distribution (fat traces).
Use plated-thru "vias" where necessary to complete circuit
connections. Via holes can be .025", with a via pad dia. of .041666"
(.025" hole, .008333" annular ring). Solder-mask the via pads (no
solder).
These rules also work for SMT components but only a single trace will
fit between surface-mount IC pins.
Mariss