Dear Technetter, I'm not sure there is a conflict between IPC-2221 voltage spacing and SIR test acc. to IPC-TM-650, § 2.6.3.3. The voltage gradient of the SIR test isn't nessecary the same as the maximal allowed voltage gradient. Otherwise a voltage gradient for electrochemical migration test (see IPC-TM-650, § 2.6.14, addressed by IPC-SM-840, § 3.9.2; and most in-house-standards uses also low voltage gradients for el.chem.migration) would limit the the voltage gradient of the design to 10V / 0.635mm. So it seems the design isn't limited by the qualification voltage gradient of SIR or el.chem.migration qualification. However, may be there resists a conflict or risk, because I can't see a overall qualification which tests SIR, dielectric breakdown etc. after a comprehensive test containing thermal aging AND thermal cycling AND moisture. And this is a question because a current field experience with dielectric breakdown between different layers as well into the same layer of a 14-layer multilayer used as transformer winding. Can anyone tell me: 1. Are the voltage spacings availabe without restrictions? This means particular: are the voltage spacings acc. IPC-2221 table 6.1 availabe/safe also after a long time (some years) application at 120°C resp. 130°C (for FR-4 according to IPC-2222, §4.3, and table 4-1)? 2. May be such overall qualifications are defind in IPC-6011 or IPC-6012? Craig, for reduced voltage spacing see also "www.fed.de/0x3e906990_0x00028ade" (in german). Thereafter the IEC document "Insulation Co-Cordination for Low-Voltage Equipment" (Committee Draft, Reg.No. 28A/127/CD, by SC 28A, issue date 5.6.1998) defines voltage spacings smaller as IPC-2221. Bernhard ---------- Von: KK Chin[SMTP:[log in to unmask]] Gesendet: Montag, 21. Juni 1999 18:57 An: [log in to unmask] Betreff: Re: [TN] IPC-2221 Conductor Spacing - More Questions - Further Questions Dear Technetter, Graig asked a very good question. I actually experienced problem following the IPC-2221 table 6.1. Analytically, 0.6mm spacing in column B2 for 100 volt seems too aggressive when the SIR test (IPC-TM-650 para 2.6.3.3 with coupon IPC-B-24) guarantees up to only 50V for 0.5mm. Practically we also saw problem with the 100V/0.6mm voltage gradient but our present findings have not been conclusive yet. My question is, is the IPC-2221 voltage spacing really in conflict with the SIR test? Graig, my apology for opening another can of worms without answering your question. K.K. Chin Artesyn Technologies Fremont, CA Craig Hillman <[log in to unmask]> on 06/18/99 03:00:00 AM Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to Craig Hillman <[log in to unmask]> To: [log in to unmask] cc: (bcc: KK Chin) Subject: [TN] IPC-2221 Table 6.1 Conductor Spacing I was wondering if anyone could provide me with information on the research used to determine the conductor spacing requirements of IPC-2221. More specifically, why is it not material dependent and is there a safety factor provided in the spacing determination? Any help would be greatly appreciated. Thanks in advance, Craig Hillman University of Maryland Dr. Craig Hillman CALCE Electronic Products and Systems Consortium University of Maryland College Park, MD 20742 (301)-405-5316 [log in to unmask]