Brian -
I don't know what your experience with conformal coatings are and I do not intend to contradict that experience, but UL1446 does not apply to conformal coatings on printed wiring boards. Refer to the scope of UL1446 at: http://ulstandardsinfonet.ul.com/scopes/1446.html which applies primarily to wound part (transformer, motors and the like). The applicable standard would be UL796 or UL746C (my memory is a little fuzzy on this, but Greg Galluccio can certainly let us know). The UL product category for conformal coatings is: Coatings for Use on Recognized Printed Wiring Boards - Component (QMJU2) I recommend interested parties read the UL Guide Card for QMJU2. The primary consideration, other than suitability for use in lieu of some fraction of the otherwise required creepage distance, is flammability of the combined board/coating. Even when used for customer reasons and not otherwise, the flammability consideration should be taken into account. Regards, Peter L. Tarver, PE [email protected] From: Brian O'Connell Sent: Tuesday, December 16, 2003 8:04 AM UL tends to view conformal coating as part of an insulation system, but this is not a requirement according to UL60950-1. Even if not required for spacing, you still must perform all Type Tests using conformal-coated PWBs, and the material should be described in the FUS report. If you do not want to always CC the PWB, carefully select which Type Tests are to be repeated using PWBs both with and without CC. This will demonstrate that CC should not affect the system safety. The UL specialist for insulation systems is Mr. A.J. Baig. He will be able to determine if UL1446 even scopes this issue... luck, Brian This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
