Water based conformal coatings FAQs

Summary

Can I use water based coatings in a dip system?

Water based coatings like Humiseal 1H20 AR3 are perfect for dip coating systems. Since they have a very low VOC content (<7%) they have minimal extraction requirements and of course very little losses from solvent evaporation. The only caution that needs to be taken is to check the fittings on the pipe work of the dip system to check that the fittings are stainless steel and not brass. This is because the DI water in the coating will cause corrosion on the part and turn the coating green in a matter of weeks!

I have been told water based coatings don’t adhere as well to PCBs. Is this true?

It can be true that water based coatings can be less effective in adhesion compared to solvent based coatings. This is because the solvents in the coating “clean” the surface of the board more effectively than water and bonding of the coating to the board is slightly improved. However, in most cases the water based coating wets perfectly well and there is no issue. If adhesion is a factor, then SCH have a range of coatings in the Humiseal range that could be selected to help.

I am having trouble brushing the 1H20 AR1 Humiseal waterbased coating and am not sure how to correct it?

There are generally two versions of each waterbased conformal coating from Humiseal. These are spray and dip blend. They are indicated by the letter S or D at the end of the code. For example, 1H20 AR3 / S is for spraying and 1H20 UR5 / D is for dipping. The reason for doing this is that to achieve a high film build in dipping was not possible with the spray version of the 1H20 materials.

However, when it comes to brushing the coating the rules seem to change. Whichever version you are using, you should try the other for brushing since we have found that some customers prefer to brush the dip version and others the spray. Either way try to flow the coating rather than conventionally brush and this will minimise the bubbles.


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