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Electronics => Beginners => Topic started by: little_carlos on October 16, 2015, 03:54:16 am

Title: Question about isolation on pcb
Post by: little_carlos on October 16, 2015, 03:54:16 am

Hey guys
After i saw some pcb, a big question came into my mind
Ive seen that when some optoisolator is used to isolate a signal on a pcb, a track is cutted below the ic, why is this being done ?

Title: Re: Question about isolation on pcb
Post by: Neilm on October 16, 2015, 02:40:23 pm

Quote from: blueskull on October 16, 2015, 04:17:33 am

Creepage means path ON BOARD between point a and b, enough creepage makes sure in high humidity environment the PCB itself won't breakdown. Also, enough creepage makes sure dust and dirt won't create an unintended path of leakage.

Creepage also applies across the body of the component. However, materials have a different tracking indexes (which determines how much creepage is needed). This is called the comparative tracking index (CTI). It is expressed in volts due to the way it tends to be measured (what voltage causes it to track). PCBs tend to be lower values of tracking index - usually about 175V. Components tend to be better tracking which means the designer needs less clearance.