Hi,

I have done many 2-layer SMD designs, but I have never done a 4-layer design. I agree with Melanie that the preferred way to go is to use many vias with 2-layer boards. There are many useful design tips in the next PDF document.

http://www.alternatezone.com/electro...torialRevA.pdf

I use pad2pad instead of expressPCB. Their software is very user friendly and it has features to check your design for flaws.

Also, there are ways for programing your chip on board without having to solder a connector for programming purposes. Well, keep us posted about your project.

Robert