SMT PRINTING · GEOMETRY
SMT Stencil Aperture Area Ratio & Paste Volume Calculator
Calculate area ratio, aperture wall area and theoretical filled aperture volume for rectangular or circular SMT stencil openings.
Aperture dimensions
Calculated results
Parameters changed; calculate again to update the results.
| Aperture area | 0.12 mm² |
|---|---|
| Aperture wall area | 0.14 mm² |
| Area ratio | 0.85714286 |
| Theoretical filled aperture volume | 0.012 mm³ |
| Theoretical volume converted | 12 nL |
Assumes straight walls, uniform cross-section and a completely filled aperture. Theoretical hole volume is not the actual paste volume deposited on the pad.
Formulas and units
Area ratio = aperture area ÷ aperture wall area. Rectangle: L × W ÷ [2 × (L + W) × t]; circle: D ÷ (4 × t).
Theoretical filled volume = aperture area × thickness. Convert thickness from μm to mm by dividing by 1000. 1 mm³ = 1 μL = 1000 nL.
How to use the result
An area ratio around 0.66 is often used as a release guideline, not a universal pass/fail guarantee. Paste, aperture wall finish and fabrication, print settings, separation and pad design also matter; verify the specific process with trial prints and solder paste inspection.
This calculation covers one straight-walled rectangular or circular aperture with uniform thickness. It does not model tapered walls, rounded corners, stepped stencils, divided apertures, fill fraction or transfer efficiency.