Design for conformal coating process

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Designing for the conformal coating process involves having Instructions for production

Once the product reliability requirements have been defined as part of the conformal coating design procedure then the resulting information needs to be combined with the data from the holistic approach.

The holistic approach examines many factors that when combined with the product reliability requirements give us exact information for designing for process.

The conformal coating process defined

Combining reliability requirements and holistic information gives us the following information:

  • Coating coverage of the circuit board
  • Conformal coating material to be used
  • Application method that is suitable for the material and circuit board
  • Masking requirements if necessary
  • Production line stages required
  • Process parameters to be met
  • Inspection criteria to be used

This data is then combined into a set of conformal coating instructions that can be used to implement the conformal coating process.

Coating coverage of the circuit board

The conformal coating coverage can be defined by three types of areas. These are:

  • Where coating must be applied
  • Where coating must not be applied
  • Where it doesnt matter if coating is present or not

Defining these areas carefully can have a huge impact on production and the associated costs.

Conformal coating material to be used

The conformal coating is defined, along with the key points such as viscosity to be used, preparation instructions etc.

Application method that is suitable for the material and circuit board

Defining the right equipment to apply the conformal coating is crucial. This information will include any options required for the systems plus any special details.

Masking requirements if necessary

If conformal coating is required, then the exact details are laid out here including the type of masking, the methods to be used and the masking materials (tapes, latex, dots, boots).

The information will be combined into a set of masking drawings.

Production line stages required

This is all of the conformal coating production stages including cleaning, priming, surface adhesion preparation, masking, application, de-masking, curing and inspection.

It will also detail any special stages required.

Process parameters to be met

This section will detail the production process factors such as viscosity of coating, machine settings, environmental parameters required etc that help keep the production line under control.

Inspection criteria to be used

The conformal coating inspection stage will examine the standards to be met and the inspection criteria to be used in inspecting the conformal coated circuit boards.

This information will include both written guidelines, pass / fail criteria and graphic examples to help the inspectors be effective.

This section will detail factors such as the conformal coating thickness that may be needed to be measured plus the measurement process.

Designing for conformal coating process

The combined information from the process provides us the conformal coating process design.

This information can be presented in a package forma

The process has been designed from combining the product reliability requirements with the holistic information of the material, application method and circuit board design.

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