Relationship between Screen and Film
Thickness
The previous section introduced the concept of
the open area ratio. Here, let’s calculate the open
area ratio from mesh size and fiber material
diameter (wire diameter). (Assume here that 1 inch
= 25.4 mm.)
Take the case where 508 mesh has wire diameter
of 25 μm (plate thickness 50 μm).
The size of a single mesh spacing is:
25.4 ÷ 508 = 0.05 mm.
Thus, a single opening size is:
0.05 - 0.025 = 0.025 mm.
The area of a single opening is 0.25 × 0.25 mm2.
Since there are 508 openings along 1 inch of mesh,
there are 508 × 508 openings within a 1-inch square.
Thus, the total area of all openings within a 1-inch
square is:
0.025 × 0.025 × 508 × 508 - 161.29 mm2.
To calculate the open area ratio, we divide this
value by the area of a 1-inch square:
161.29 ÷ (25.4 × 25.4) = 0.25.
We obtain an open area ratio of 25% for this
mesh.
We can also calculate ink thickness as open area
ratio × plate thickness. (This value corresponds to
the volume of ink deposited onto the substrate.)
Since the plate thickness in the above example is
50 μm, the ink thickness is
50 × 0.25 = 12.5 μm.
Thus, the thickness of the ink layer is 12.5 μm.
This value represents the thickness of ink before
drying. To calculate the thickness of the ink after
drying, we need to consider the concentration of
non-volatile components.
If we assume here that the non-volatile
components in this ink are 20%, the thickness after
drying will be 2.5 μm.