Sunil, Without knowing more specifics about your geometry, here are a few generic considerations: As with most things in signal integrity, it is not the absolute values that matter, rather values in relation to others. In your case, the 6 mil drill is meaningless without knowing the feature sizes around the via on the other layers. If the middle layers are planes, you need openings to carry the via barrel through. The ratio of via barrel to the size of these openings is a good starting point estimate the via performance. The overall board thickness in relation to the number of plane layers is another key factor. Also, if your signals are differential, the location of the other via in the pair and the ground stitching via distance(s) all make a difference. Specifically, unless you have a very thin board and access to special technology, you may not be able to get your PCB fab house to make a plated through hole with 6 mil drill. If you increase the drillsize, you may need to increase also the size of the square pad on the other side. If the pitch of square pads is fixed, you may be better off using short escape traces leading to the vias. Regards, Istvan Novak SUN Microsystems sunil bharadwaz wrote: > Hi , > I'am doing a form factor board where few signals are brought from top layer > to > the bottom layer with thru hole Via's.On the bottom layer these signals will > be connected to the square pads laying on the edges of the PCB.The Via > from the top layer directly goes to the bottom side square pad.The PCB's > are 4 to 6 layers. > > These form factor boards with sqaure pads will be soldered to another Mother > board , where you can access these signals. > > I have a 100 Mhz clock as one signal.I'am using via sizes of 6 mil drill & > 10 mil pads. > Would be safe to increase the drill size & the pad size. > > If one of the signal is an 5.0 Ghz RF signal , is it safer to use bigger > via's. > I have no access to EM simulator at this time.. > > Can some one pls throw some light on this.I would also like to know the > approx inductance & capacitance for these Via's. > > Thanks in Advance !! > > Best Regards > Sunil.b > > > > > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List technical documents are available at: http://www.si-list.net List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu