Roland, In the old D-275 there was a good explanation and detail. I'm having trouble finding it in the new IPC documents. This is a similar issue I'm having. Keep in mind that the lead to hole diameter spacing, type of flux, preheat temp, pot temp and conveyor speed are all factors in the soldering too. I'll be interested to see what other responses you get. Phil -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Roland Jaquet Sent: Wednesday, November 28, 2007 9:05 AM To: [log in to unmask] Subject: [TN] Thermal Pads Dimension versus size / Copper Thickness Dear Technetters, I am having an issue with the very different sizes of Thermal Pads used on a Power PCB mix. A 4 Layer PCB with 2 Oz Copper for the inner layers and 1 Oz. + Plating on the outside. At the Soldering, the small components get too hot while solder (Lead-Free) does not get up high enough on the component side. I am wondering if there is a formula to calculate the size / shape and dimension of the optimum Thermal Pad (Frein Thermique). Thank you for your input Meilleures Salutations Very Best Regards Roland www.PCBspecialist.com Roland Jaquet 14 Champ Budin 1258 Perly, GENEVA SWTZERLAND GSM+41-79-203-3723 --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------