I hope the following information can be of some help to you. (1) With reference to "Printed Circuit Handbook by Clyde F. Coombs Jr" : Consider a 0.04" diameter hole plated to a 2-oz internal power plane with 0.001" minimum copper in the hole. The copper hole wall is equivalent to: 0.04" x 0.001" x PI = 125 x 10 exp -6 sq.in At the interconnection to the power plane, there will be : 0.04" x 0.0028" x PI = 352 x 10 exp -6 sq. in (Note : 0.0028" is the thickness of 2-oz copper) With reference to the current-carrying capacity chart of MIL-STD-275 or now IPC-D-275, a 125 x 10 exp -6 sq. in conductor will carry approximately 2A with a 10 deg. C rise above ambient. (2) With reference to " Handbook of Printed Circuit Design, Manufacture, Components & Assembly by Giovanni Leonida" : I = (W/K) exp0.538 where the value of K = 3.60 for 1-oz/10 deg C above ambient 1.97 for 2-oz/10 deg C above ambient 1.97 for 1-oz/20 deg C above ambient 1.10 for 2-oz/20 deg C above ambient 1.45 for 1-oz/30 deg C above ambient 0.80 for 2-oz/30 deg C above ambient 1.20 for 1-oz/40 deg C above ambient 0.65 for 2-oz/40 deg C above ambient 1.30 for 3-oz/10 deg C above ambient 0.80 for 3-oz/20 deg C above ambient 0.53 for 3-oz/30 deg C above ambient 0.45 for 3-oz/40 deg C above ambient W is the width of the conductor in mils. Example : Current which can flow through a conductor with W = 0.15in, 3-oz/sq. ft at temperature rise of 40 deg C is I = (150/0.45)exp0.538 = 333.3exp0.538 = 22.8A. Since the conductor width is more than 0.04", the value obtained should be decreased by 50%. Regards. Scott Holthausen wrote: > Hey TechNeter's > > Does anybody have an equation that could help a person determine the > current handling capability of through hole vias? Our practice has > normally been to use multiple vias to connect components with high current > paths to plane layers. However, that isn't good enough for one of our > engineers who wants more than an approximation, and wishes to find out > whether we are putting more vias on the board than we need to. > > Thanks, > Scott Holthausen > > ################################################################ > TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c > ################################################################ > To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: > To subscribe: SUBSCRIBE TechNet <your full name> > To unsubscribe: SIGNOFF TechNet > ################################################################ > Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. > For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 > ################################################################ ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################