CTI Comparative Tracking Index.
Standard FR4 has a CTI > 175 V but you may need an higher value,
in our pcb online calculator you can order pcb with CTI > 500.
What we mean by CTI ?
50 drops of water are leaked on the laminate,
CTI is the maximum voltage (V) the laminate withstands
Complete test method is described on Underwriters Laboratories site :
Laminates are grouped as described below :
|PLC group||CTI value (Volt)|
|1||400 - 599|
|2||250 - 399|
|3||175 - 249|
|4||100 - 174|