Why does the solids content of my conformal coating matter for costing a printed circuit board for application?
The amount of solids content in a conformal coating is the amount of actual material available to be applied to the circuit board and that will protect the circuit board assembly.
The more solids you have the more circuit boards you can coat.
So, you want to have as much solids as possible per liter when you buy the material.
Caution –Check the conformal coating solids is at the right viscosity for application!
You also need to take care when comparing individual materials from different companies.
The differences in both solids content and viscosity can be striking and you can be wasting a lot of money on solvents that literally evaporate away.
The first stage in checking this is to determine the final solids content of the material that you will use in production. That is the correctly blended coating ready for application at the right viscosity.
Take the following example that is typical of conformal coatings sold commercially around the world.
Material X is 35% solids as sold.
Its viscosity is 190 cps approx. at this solids content.
However, to spray the coating it must be at 24 cps approx. So, the coating must be diluted by 50% with thinners to reach this viscosity.
This means material X is now 17.5% solids and a viscosity of 24 cps approx. This also means there is >80% of the material that evaporates away!
Check the market!
You cannot assume that all conformal coating materials are similar.
For example, SCH have a UL approved acrylic conformal coating that is 44% solids at 24 cps and ready to spray.
Comparing Material X (17.5%) and this particular material means that the higher solids coating has more than twice as much coverage power for the same liter of material.
If the coatings are similar in price at this viscosity then you need to buy at least 2x more of material X than the higher solids product to get the same coverage.
Quite a saving can be made if care is taken!
Want to find out more about coating coverage?
If you would like a spreadsheet that you can just punch the values in to calculate coating coverage and costs per PCB then contact us directly and we can send it through to you to help you.
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