[sdiy] First PCB....

[Tim Parkhurst]

On Thu, Sep 10, 2009 at 1:44 PM, Tom Adam <tom.adam at thebigear.be> wrote:
> Howdy,
> I just designed my first PCB in an effort to get to know the software
> (expressPCB/SCH). Nothing fancy, and if I would build it I would use MUUB
> pcb's, but I needed something easy for my first try.

Hey Tom,

Not bad for a first attempt. Here are some very general rules for PCB
layout that I like to follow:

1) Lay down your power and ground traces first. I do that by putting
down the ICs and the power input stuff and then routing the power
traces.
2) Keep all your ICs oriented the same way, and keep pin 1 pointed in
the same direction. For example, I always orient ICs horizontally and
keep pin 1 to the lower left. This not only makes the board look
better, but it reduces the possibility of putting an IC in the wrong
way.
3) Try to keep all your axial lead passives (Rs, Cs, Ds) going in the
same direction. Every once in a while I'll need to orient one or two
in a different direction, but I try to keep my passives oriented
vertically. Don't forget that you can use components as "jumpers" and
route traces underneath them (in between the pads)
4) Move the designators on the silkscreen layer so that they aren't
hidden by the components. This takes a little extra time, but it makes
troubleshooting and modding much easier later on.
5) Try to keep traces oriented vertically or horizontally. Avoid sharp
corners, and use a 45 degree 'chamfer' instead when you need to change
direction.

I always breadboard a circuit and prototype it first before commiting
to a PCB. Additionally, before starting the PCB I sketch a rough
layout on paper to see where I want to place the ICs and where the
primary signals will flow. I try to arrange things to get the
straightest, shortest signal paths and eliminate as many crossover
points as possible. You usually can't completely eliminate this sort
of thing, but you can at least minimize it.

Hope this helps, and most of all, keep practicing! Oh, and seconded on
KiCAD. It's free, it outputs Gerber files and AI files for my
documentation, and I'm very happy with it. I've used it for all of my
Magic Smoke stuff, and several other contracting projects.

Tim (Mister Short Traces) Servo
-- 
"Sire, the church of God is an anvil that has worn out many hammers."
- H.L. Hastings