CTI ( Comparative Tracking Index )
CTI Comparative Tracking Index.
Standard FR4 has a CTI > 175 V .
50 drops of water are leaked on the laminate,
CTI is the maximum voltage (V) the laminate withstands
without tracking.
Complete test method is described on Underwriters Laboratories site :
Laminates are grouped as described below :
| PLC group | CTI value (Volt) | ||
| 0 | > 600 | ||
| 1 | 400 - 599 | ||
| 2 | 250 - 399 | ||
| 3 | 175 - 249 | ||
| 4 | 100 - 174 | ||
| 5 | < 100 | ||