Re: gEDA-user: an unplated via - a capacitor inside a board

[Xtian Xultz <xultz@xxxxxxxxxxxx>]

Em Sáb 11 Mar 2006 18:34, Karel Kulhavy escreveu:
> Let's say I have a ground plane on the solder side and power plane on
> the component side. I want to place a blocking capacitor between those
> two with the minimum parasitic inductance.
>
> The solution with minimum parasitic inductance is to make a via, but not
> plate it through, just leave the rings around the hole. Make the hole
> big enough for a 1206 capacitor to fit, insert a capacitor and solder on
> both sides.
>
> Is this possible with PCB?
>
> CL<

I dont know if I understanded what you want, it is a little... strange :D
Well, I tryed with Xaw PCB (the latest version), didnt create the output 
files, but I think it will work.
First, create a footprint with two pads, every pad must be big enough to fit 
the hole where you will insert the capacitor, and have sufficient solder 
area. Make one pad on the solder layer, and send the other pad to the 
component layer. Give the first the padnumber (n key) 1 and the other 
padnumer 2. Put one pad over the other. If you like, create a silkscreen 
around him, select all, cut selection to buffer, convert buffer to element.
Put the part where you want. Connect the pads to the polygons with thermals, 
or if you like, connect them with a line, join the line with the polygon (j 
key) and increase the size until he covers the entire pad. 
Then, create a via with the hole size enough to insert the capacitor, convert 
him to mounting hole (control+h) and place over the part. 
Thats it.
But, you must assure that your pcb fab does drilling process for plated holes 
and for unplatted holes. 
For example, my fab does not. In that case, I would insert a normal via (but 
only after the complete routing is done, because to PCB its a big short 
circuit). The hole will be metalized, but I rework the boards redrilling the 
holes with a bit a little big.