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

[Karel Kulhavy <clock@xxxxxxxxxxxxx>]

On Sat, Mar 11, 2006 at 07:27:52PM -0300, Xtian Xultz wrote:
> 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. 

Would it be possible to put this guide on the website (possibly stating
that this is an innovative novel method that other programs are not
having in their help)? ;-)

I guess that there shouldn't be any problem with gas pressure inside
because the hole is unplated and the gas can dissipate into/from the
porous laminate.

CL<
> 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.