Homebrew PCBs

ae5ew wrote: 
> How is an IC lead connected to say layer 8 on a 16 layer PCB. A 16
> layer board is built one layer at a time (etching)? Any guidance would
> be appreciated. 


Difficult to see is how the layer stack is interconnected. Some images
of vias, blind vias, buried vias, filled vias from a quick search
http://www.pcb007.com/pages/zone.cgi?a=48518&_pf_=1

Build process varies and is complex. See these two books:
http://books.google.pt/books?id=m8sJBIMtETgC&pg=PA414&lpg=PA414
http://books.google.pt/books?id=g9Q8RekeKaAC&pg=PA16&lpg=PA16

A easy way to see it, is a manufactor start with a core double layer
board, it's imaged and etched and goes to the stack build by over laying
a not cured resin layer and a copper foil on each side and hot pressed.
It became a two layer board again and is re-processed. If you wish
buried vias the board is drilled and plated each time. But there are
stacks of double layers drilled and pressed one time only.
The plating process to deposit copper on the hole wall, is a resin
activation chemical steps followed by a modified copper plating bath
that plates same copper amount on low resistance copper as well
activated resin. (Or old electroless process)