CNC routing is great.  With a fine point engraver and a low runout 
spindle, doing a QFP with 11mil pads and 13 mil separation is no sweat 
as long as the board is small.

Larger boards do run into flatness issues unless you have a floating 
head that presses the board down around the engraver.  If the board is 
not flat against the table, the engraver goes deeper than intended.  
That not only routes out more of the FR4 core but if it's a fine-point 
engraver it's going to be V-shaped so it will cut wider than intended 
when it's going in deeper.

Danny

Vasile Surducan wrote:
> Looking to the attached picture I see there is a very large insulation
> between routes.
> Component footprint is ugly. That's partially because of the etching
> process. Choose such dillution for the solution to keep the etching
> process slow.
> A 0.5 oz PCB is better for high pitch density than 1 oz.
> However the picture still shows a low quality homebrew process. If you
> really want to use 0.5mm pitch or lower and large number of pin
> package, my recommandation is to forget this methode and use CNC,
> which is much better for low quantity of PCB even if the CNC machine
> is homebrewed (of course using proffesional drill&mill bits)
>
> Vasile
>   

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist