Barbara Not really relevant to your question but slightly so. In the 1960s, when PTHs were a novelty and I was in a different life, our standard test procedure was to daisy-chain, on the edge of the panel, half-a dozen holes of each diameter on the boards, minimum 0.65 mm (times have changed!). We would connect this series of holes to a 6 V supply through a 6 V 36 W headlamp bulb. This gave a surge current of about 20 A for a fraction of a second, tailing off to a steady 6 A. We kept this on for 20 sec. If the connection survived this brutality, we knew the copper plating (nominal 25 µm) and the hole quality were good. The smaller holes did heat up a few tens of °C with this. I would conclude from this that the amount of copper in a 0.65 mm hole was amply sufficient to carry 1 A in service, provided the IR drop was acceptable. You could pro rata this down linearly for smaller holes (assuming the same Cu thickness). Brian Brian Barbara Burcham wrote: > > Anyone out there have any models, formulas, or charts. > > Barbara Burcham > > --------------------------------------------------------------------------------- > Technet Mail List provided as a free service by IPC using LISTSERV 1.8d > To unsubscribe, send a message to [log in to unmask] with following text in > the BODY (NOT the subject field): SIGNOFF Technet > To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL > Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives > Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 > --------------------------------------------------------------------------------- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------