is solder mask effect impedance control

[henryc]

Hi
if calculate the impedance control ,do I need to count with thickness on solder mask ,is it soldermask effect impedance ,because my fab house give me data on impedance control ,they alway are
calculate with thickness of soldermask .please tell me about that .

thanks
henry

[cadpro2k]

Hi Henry,

Soldermask has little effect, if any at all regarding impedance. I never calc it in. Your impedance tolerance will certainly account for any variation the soldermask might make. I vote - Don't worry it.

Good day.

[henryc]

Thanks I ' m not worry now