How can I determine how much board coverage I can achieve using a conformal coating?
This is a rough formula for estimating conformal coating coverage, based entirely upon a bare, unpopulated board and does not compensate for any transfer inefficiencies, components or wastage.
- In one Litre there are 1,000 cubic centimetres (1ml = 1cm3).
- 1cm = 10,000μm, therefore 25μm (approx 1 mil) = 0.0025cm.
- To obtain the coverage, if the coating is 100% solids, you would divide the 1,000 cubic centimetres (1 litre) by 0.0025 – thereby obtaining coverage of 400,000 square centimetres at 25μm (~1 mil) thick.
- If you are seeking a thickness of 50μm or 75 μm ( approx 2 or 3 mils) you would simply divide the 1,000 cubic centimetres by the desired thickness; i.e. 0.005 (50μm / 2 mils) = 200,000 square centimetres of coverage and 0.0075 (75μm /3 mils) = 133,333 square centimetres of coverage.
THE ABOVE ASSUMES 100% SOLIDS – TO COMPENSATE FOR THE SOLVENT LOSS YOU NEED TO MULTIPLY ANY OF THE ABOVE COVERAGE NUMBERS BY THE PERCENT OF SOLIDS CONTAINED IN THE COATING – AS FOLLOWS:
As an example Conformal Coating A is 35% solids therefore coverage at 25μm (1 mil) would be 140,000 square centimetres (400,000 x 35%), coverage at 75μm (3 mils) would be 46,667 square centimetres (133,333 x 35%). This method will work for all conformal coatings. The only variable is the percent of solids within the different coatings.