Conformal coating bubbles why

The drying and cure schedule can also affect bubble formation. Sometimes air cure is needed to permit solvent evaporation; sometimes immediate thermal cure is more desirable because of lower material viscosity caused by higher temperature. Spray coating, being more thinly applied, is not as susceptible to bubbling caused by solvent and air entrapment as are dip coating and brush coating.

For thicker coating applications, degassing in a vacuum chamber will remove entrapped air. One of the major causes for failure during conformal coating inspection are bubbles. Bubbles are trapped pockets of air under coating.

The bubbles can cause voids in the coating and Here we will identify the six largest causes of bubbles. My account Login View Cart 0. Dewetting - This is caused by contamination on the substrate that is incompatible with the coating. The most likely culprits are flux residues, process oils, mold release, and fingerprint oils.

Dewetting can be recognized simply by observing areas of good coating application next to areas where the coating beads up and moves away from the contaminated area. Think of it as putting a drop of detergent in oily water — the oil immediately moves away from the single drop.

Cleaning the substrate thoroughly prior to coating application will resolve this. Photo courtesy of NPL Delamination - This is characterized by an area of the coating losing adhesion to the substrate, which can cause the coating to lift from the surface.

Though there are a couple of common causes for this problem, one main cause is again a contaminated surface. Usually, you will only notice delamination after the part is out in the field, as it is not immediately observed in the majority of cases. Proper cleaning can prevent delamination. Another cause is insufficient tack time between coats. In this scenario, the solvent would not have had the proper time to flash off prior to the next coat.

Solvents eventually will disappear in to the atmosphere when curing. The less solids content the coating has, the more solvents it contains. Thus, more solvents could mean more possibilities of generating bubbles. Solvent Type: Solvent vapor evaporation rate will affect bubble formation. Sometimes the solution lays in the combination of solvents used and oven profiles.

Since there are many combinations of these variables, contact us to help you with thinner selection. Curing recommendations: Regularly, the product manufacturer would include some recommendation on how to cure the material. Whether you should cure it at RT room temperature , heat to accelerate or through a chemical reaction, it is important to know and understand all these recommendations. For example: curing too fast may generate bubbles by trapping solvent vapor under the coating surface.

They are all over the board. They make the coating look like sparkling water; sometimes the bubbles are great in number that they can form a foam. Big bubbles. Usually near large components.