How to select substrate thickness for phased array.

I gonna design a 60 GHz linear phased array with four microstrip patch antenna on Ferro A6M LTCC, εr=5.99, tanδ=0.002.

What's the substrate thickness should I choose. Any formula?

What if εr=2.2, tanδ=0.0009 then?

Dear,

h ≤ c / ( 4*f*√(Er-1))

You can use this formula for rough estimation and then contact the fabrication company the height available because u can not find height for every value.

check the theory on substrate propagation