AVR-Chat

On 11/6/2010 11:54 AM, Chuck Hackett wrote:
> I know this is dangerous, but ... :-)
>
> I'm looking for a critique of the board layout for my first significant project.
>

A few suggestions

   - Consider adding power and ground planes.  It frees up your 
available routing space considerably.  Also keeps supply impedances low. 
  That will likely mean not using milling but in my experience milling 
PCBs is overrated.
   - Use Eagles via restrict layer to keep layers from underneath 
connectors and chips.  Especially valuable when hand populating since it 
considerably reduces the chances of a short and since vias are now 
accessible the are available for adding test points or patches.  You may 
have to accept some vias in unfortunate places but I'd at least try to 
remove the issue. Auto-routers will relieve you of tedious work but they 
need a lot of guidance to work well.
   - I'd be worried about the size of the heat sink on the regulator. 
You won't need much of a voltage drop or current draw to overwhelm it. 
Consider more copper on multiple layers with thermal vias.
   - I don't trust crystals to sockets, I'd solder it to the board.
   - Unlike some other's I would keep the supply monitor but I'm paranoid :)
   - On silk screen less is more. Eagle's are overly ornate.  They do 
have it split into several layers as I recall.  All you really need and 
all the is actually useful is an extents indicator, a pin 1 or polarity 
indicator and an ID.
   - Add a silkscreen rectangle (or several) for notes in marker such as 
stuff date, version etc...
   - I normally put PCB part number and rev in copper (the stuffed board 
gets a part number and rev written by marker on silkscreen rectangles)
   - Samtec has a nice sealed connector with a pigtail to a board 
mounted socket that might work for your application, I can look up the 
part number if you like.
   - Don't be afraid to put components on the back of the board, 
particularly passives.  That can free up considerable room if you are 
using surface mount and if you are hand stuffing it's not usually harder 
to handle.

Robert

-- 
http://www.aeolusdevelopment.com/

  From the Divided by a Common Language File (Edited to protect the guilty)
ME - "I'd like to get Price and delivery for connector Part # XXXXX"
Dist./Rep - "$X.XX Lead time 37 days"
ME - "Anything we can do about lead time?  37 days seems a bit high."
Dist./Rep - "that is the lead time given because our stock is live....
we currently have stock."