Normally we have three kinds of thicknesses for VOID film material, 25u, 36u, 50u.
Partial transfer VOID film material: 25u/50u
Total transfer VOID film material: 25u/50u
Non transfer VOID film material: 36u
Why these three thicknesses? Because during our long time experiment, these are most suitable statistics for films to perform perfect.
Also about partial and total transfer VOID film material, 25u/50u which we shall choose, this will be depended on the practial situations where we use it. We can discuss about it and find the best solution.