Sam wrote:
> - how thick should be power and gnd paths

As thick as you can manage within the other constraints.  A whole ground
plane is best.  This gives the board good RF properties in addition to low
impedence between all the ground points.

> - what decoupling capacitors should I use

At least 100nF ceramic for lower power things.  Nowadays I use 1uF ceramic
for anything more than a few milliamps.  New ceramic technology and high
volumes have made these cheap and available.

> - how should be decoupling capacitors placed

As close to the power pins as possible.  If you've got a high current device
with multiple power and ground pins, bring each net together at a single
point and connect only that single point to the rest of the board power and
ground.  By doing that the local loop currents will stay local.

> - how distance between paths influence signal integrity

Longer makes it worse.  At short distances it's mostly an impedence issue.
Once the trace gets to be near 1/2 wavelength or longer you have to consider
antenna effects too.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist