Not sure about the 100um diameter balls , but I've used the number 816pH/mm for 65um dia. solder balls (actually C4 joints). For a height of 70um this would be about 57 pH. For 100um balls I'd guess the inductance would be somewhat less. The number was derived from the twin lead transmission line formula where the loop inductance L=0.4*uR*ln(D/a) where D is the distance between conductors (balls) and a is the radius of the conductor (balls). uR is the relative permiability (1.0 for air). Using this equation assumes the balls can be approximated as cylinders. Note that this will give you an approximation for the partial inductance contributed by the solderball, but says nothing about total loop inductance. Perhaps someone has some better approximations or formulas. -Ray Anderson Firas Azrai wrote: >Hello everyone, >Does anyone have a rough estimate or a first order equation that calculates >the inductance of a reflowed solderball with a base diameter of 100um and a >height of 70um. Can this structure be approximated to a cylindrical one? > >I appreciate any response and input. > >Firas S. Azrai >Electrical Engineer >Integral Wave Technologies > >108 Wild Basin Rd. >Suite 218 >Austin, TX 78746 > >Tel : 512-416-9700 >Fax: 512-437-2792 > > ------------------------------------------------------------------ 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 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