Ahhh, I love the sound of a Deweyism early in the Morning. All the questions on adhesives and now this bonding too; what a cohesive group. A friend of mine's wife didn't want to dignify what we did when we got together with the term Male Bonding, so she called it "weiner welding". Since she hated my Deweyisms, I would always reply "you always think the wurst". Dewey -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Nutting Sent: Friday, August 17, 2007 6:49 AM To: [log in to unmask] Subject: Re: [TN] NTC Seeking design information on PWB conductor spacing for high voltage (500-1000 VDC) applications Ahhh, a Deweyism. Very good. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar Sent: Friday, August 17, 2007 9:46 AM To: [log in to unmask] Subject: Re: [TN] Seeking design information on PWB conductor spacing for high voltage (500-1000 VDC) applications with such good marginals, one will phil nuthing when heat is on... Inge -----Original Message----- From: Phil Nutting [mailto:[log in to unmask]] Sent: den 17 augusti 2007 14:30 To: TechNet E-Mail Forum; Hernefjord Ingemar Subject: RE: [TN] Seeking design information on PWB conductor spacing for high voltage (500-1000 VDC) applications To add to this, we will frequently route a slot between two traces or pads to increase the creepage clearance when a large physical distance is not possible. For numbers we use 10 kV per inch for surface creepage and clearance in air. For boards submerged in dielectric oil we use 20 kV for surface creepage and 50 kV for clearance in oil. For hipot tests (4 kV) to satisfy medical requirements we use 8 mm spacing between SELV and ground. Conformal coating can help, but we typically don't need it. Phil -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Hernefjord Ingemar Sent: Friday, August 17, 2007 3:07 AM To: [log in to unmask] Subject: Re: [TN] Seeking design information on PWB conductor spacing for high voltage (500-1000 VDC) applications We have a rather simple thumb rule for top conductors: flashover 1,250 VDC/mm for dry air flashover 2,500 VDC/mm for solder mask flashover 7,500 VDC/mm for potted board to avoid creep current you need following distance between top conductors: 7 mm/kV up to 3,000 meter altitude without protection, clean air 15 mm/kV up to 3,000 meter " " " , dusty air 25 mm/kV up to >3,000 meter " " " , std environment 5 mm/kV up to 3,000 meter " with protection, std environment 2.5 mm/kV up to >3,000 meter " " " " We make MIL products, UL and other commercial requirements are of course different. The cleanliness of the boards is mainly the deciding basis for the isolation distances. This information is based on rather old stuff, but I think not much is changed. Inge -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Gerald Bogert Sent: den 17 augusti 2007 00:24 To: [log in to unmask] Subject: [TN] Seeking design information on PWB conductor spacing for high voltage (500-1000 VDC) applications August 16, 2007 IPC-2221 section 6.3 and the associated table provides specific electrical conductor spacing requirements for voltages up to 500 volts. However, for voltages > 500 volts, it defaults to a formula in section 6.3. What is the technical basis for the minimum spacing requirements that are listed in the table? How reliable is the formula for voltages > 500 volts. How valid is the formula if we have 1000 VDC on the PWB? Since the table does not specifically list minimum electrical spacing for voltages > 500 volts is the formula just a "SWAG" or based on real data? If so, what is the formula based on? Does anyone have design standards for high voltage PWB spacings that they are willing to share? We had an OEM that had recent field failures (shorts to internal traces) of a conformal coated multilayer FR4 PWB (0.062 in) that has both low (logic voltage) and high (approx 780 VDC nominal) circuits. The board was required to be designed to IPC-D-275 requirements, and the table in 275 is basically the same as in IPC-2221. The PWB is being redesigned and I need to verify the new design meets reliable and valid minimum conductor spacing requirements. Are there any design standards other than IPC-2221 that could be used for high voltage PWB? --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 ----------------------------------------------------- --------------------------------------------------- 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 -----------------------------------------------------