IEC 950 defines CIT (comparative tracking index) in terms of material groups for the determination of creapage distance. Specifically groups I, II, IIIa and IIIb. are mentioned. In paragraph 2.9.3 (note 3) the actual index (CTI) is referred to as <600 or <400. My questions are as follows:
1. Is this CTI (as assigned by UL in the yellow book) actually a voltage level? 2. The FR4 laminate we use has been rated at 205. As such the maximum creapage distance is mandated. Is it common to find better material? Is this 205 level typical of common FR4 materials? Thanks Rick Busche Evans & Sutherland rbus...@es.com