Anne, Comparitive Tracking Index (CTI} is by definition the voltage at which 50 drops of a 0.1% solution of ammonium chloride causes failure (ASTM D-3638). The CTI is used to compare the performance of insulating materials, against the formation of carbonneous tracks on the surface, under wet contaminated conditions. From this value a material can be assigned a Perfomance Level Catergorie (PLC)per UL 746A. In which 175> is at least a PLC 3. From this you can go to EN 60 950?? to determine your minimum spacing at a given voltage. I had to read through all the specs for a customer shipping product to the U.K. Believe you don't want to read them. To me, the procedure seems as flakey as a 3 $ bill. Even though there is a huge range among like materials most fr4 runs from 200-400 volts. See your material supplier or the materials yellow card under UL QMTS2. Good luck and hope this helps. Robert E. Welch Process Specialist Waytec Electronics Corp. Phone 804-237-6391 ext. 138 Fax 804-237-3048 > -----Original Message----- > From: TechNet [mailto:[log in to unmask]]On Behalf Of Anne Ledger > Sent: Thursday, March 18, 1999 10:21 AM > To: [log in to unmask] > Subject: [TN] Comparative Tracking Index? > > > Good Morning TechNet, > > I have a fabrication drawing with a note with the following note. > > Material: .062 laminated glass (woven fabric) base, epoxy resin, Flame > retardent, FR4. > copper clad 2 oz./sq ft. Laminate must be certified to > have a minimum comparative > tracking index of 175. Microsection demonstrating > compliance with copper weight, > dielectric spacing, line width and use of CTI 175 or > better material shall be shipped > with each lot. > > I am at a loss on the CTI 175 stuff. I have reviewed IPC 4101 and don't > find a reference. I have > placed a call to our material supplier but no response yet. The TechNet > seems much faster. > Can anyone provide me with a clue? Thanks in advance for the help. > > Anne Ledger > EMDS, Inc. > [log in to unmask] > > ################################################################ > TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c > ################################################################ > To subscribe/unsubscribe, send a message to [log in to unmask] with > following text in the body: > To subscribe: SUBSCRIBE TechNet <your full name> > To unsubscribe: SIGNOFF TechNet > ################################################################ > Please visit IPC's web site (http://www.ipc.org) "On-Line > Services" section for additional information. > For technical support contact Hugo Scaramuzza at [log in to unmask] > or 847-509-9700 ext.312 > ################################################################ > ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################