Conformal coating aerosol spraying

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Conformal coating aerosol spraying is one of the widest methods used in low and medium volume application.
Photo courtesy of SCH Technologies

Conformal coating aerosols are one of the widest used techniques used in low volume conformal coating processing.

An aerosol is a portable spray gun with self-contained conformal coating.

Using an aerosol can of conformal coating offers a very fast entry to low and medium volume processing.

Similar to batch spraying, the coating is applied across the whole of the circuit. It is not selective.

Therefore, masking may be required to protect components that must not be coated.

Normally, aerosols are not required to be shaken since there is little separation of the constituent parts and the bubbles introduced into the process can be slow to dissipate.

The key areas for aerosol spraying

Which conformal coatings can be used in aerosol spraying?

Most traditional solvent-based conformal coatings are supplied in an aerosol can.

It is the Manufacturer who chooses whether a coating material is available in aerosol format.

Alternative materials like UV cure, moisture cure and two part coatings do not easily lend themselves to aerosol coatings and are rarely packaged this way.

What equipment do you need for aerosol spraying?

For aerosols, the product is all self contained.

The only requirement is an area that is safe to spray atomised coating such as a spray booth.

This is a low cost set up that can handle a fairly high volume of product.

Is aerosol spraying of conformal coating a complex process?

There is no blending of the coating for aerosols that is required like a spray batch process so this does simplify the process a little.

However, spraying in general of coatings is a skilled process.

It requires training and knowledge to achieve good quality coating finish.

Also, there is no setting up of the spray gun with the right amount of atomisation pressure and material feed that is critical to ensure a good coating finish.

How cost effective is the conformal coating aerosol process?

Spraying aerosols within a spray booth is a very cost effective process for low and volume coating.

However, if masking is required, then the cost of processing must be considered with this in mind.

Also, aerosols tend to be expensive option for coating coverage compared to batch spraying.

So, there is a critical point where the volume of circuit boards makes the cost of processing more expensive than using a spray booth and spray gun.

Is aerosol spraying of conformal coating a low, medium or high volume technique?

Aerosols are really a low volume process.

They can be used in medium and high volume but the cost per PCB for the process is higher compared to other methods.

What variables control the quality of the conformal coating finish in aerosol spraying?

Variables that influence the quality of the coating process in aerosol spraying are:

  • The operator skill. Spraying in general of coatings is a skilled process. Conformal coating application is no different.
  • The volume of solids. Some aerosols have more solvent percentage than others. This makes the coating thickness variation high.
  • The level of masking required. If the masking is complex then there are more likely to be problems due to the application of the coating due to leakage of the masking.

What are five advantages of the aerosol spray conformal coating process?

  1. Low cost process to set up.
  2. Fast speed of set up
  3. Simpler process compared to batch spraying
  4. Flexibility for low volume application
  5. Quality of Finish due to excellent edge coverage gives best protection to circuits

What are five disadvantages of the aerosol spray conformal coating process?

  1. The operator still needs skill in spraying the conformal coating correctly
  2. Quality Control is dependent on the operator
  3. Costs are high for volume compared to other methods
  4. Limited control of process with fixed aerosol nozzle.
  5. Masking costs can be high