Yvon,
A typical dielectric constant value for an 0.062 FR-4 laminate would be 4.5.
As you proceed with your microstrip design, the impedance will be effected by
the solder mask coating (if you plan on using one).  Typical solder mask
materials have a dielectric constant of 3.5. One last consideration for a
microstrip design is the dielectric constant of air that would be on top of
the solder mask.  When these three mixed dielectric constants and thicknesses
are considered, you should be able to predict the impedance for a given line
width and metal thickness.
If you would like to drop me a note with the required impedance, line width,
metal thickness and if a solder mask is used, I will be happy to run a mixed
dielectric impedance calculation for you.

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