Mask coating thickness

[amjad]

Hi all,

What is the mask coating thickness generally followed above subtrate and above trace? Since this is considered in impedance calculation, can anyone answer me?

Thanks.

 

[House_Cat]

You would have to talk to you fabricator to get a decent estimate. There are several types of mask that are used, and several different ways of applying the mask.

Dry film mask comes in various thicknesses. LPI, since it is liquid, can be applied thick or thin. Typically, you would find dry film at about 1-1.4 mils uniform thickness across the board. LPI could be 1-3 mils and uneven thickness as a result of uneven application, or board position during curing. The effect of mask on impedance is measurable, but not great.