AVR-Chat

Don't even try to attempt gluing boards together as this is far more hassle
than having a board house do 4 layer board for you. There is also the hassle
of trying to do this in your software. You effectively have 3 PCB designs.
As I said, not recommended.
 
Looking at the website, Eagle supports multiple layers and most places offer
4 layers for about 2-3 times a 2 layer board which is a pretty reasonable
price for small runs and as Robert says, connecting VCC and GND is a lot
easier than trying to route tracks all over the board. You can also have
other power rails in the power planes using SPLIT PLANE technology but best
left out if you have not done this before.
 
I am now moving all my current and future designs to 4 layer because the
cost now is considerably less than it used to be.
 
Dave.
 
From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Robert Adsett
Sent: 09 November 2010 09:56
To: AVR-Chat@yahoogroups.com
Subject: Re: [AVR-Chat] Looking for critique on board layout
 
  
> How do power and GND planes prevent using isolation routing (I use
pcb-gcode)?

Well, you could glue boards together after routing them to produce a 
four layer board. I know it can be done but I've never been tempted to 
try. The usual technique, I understand, is to route the inner planes 
(usually power and ground) first on a double sided board and then route 
the signal layers on single sided boards before glueing the whole thing 
together. I don't recall how connections were made to the inner layers.

Me, I let a board house take care of it, they have proper plating 
equipment to plate the vias to connect to the inner layers.

Proper power and ground planes do help routing a lot. Since power 
traces are never very long, just long enough to drop a via to the plane, 
your signals never need to crawl all over the place to weave in amongst 
power and ground traces.

I really recommend you at least try routing with separate power and 
ground planes (IE a four layer board) and see how it frees things up for 
you.




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