The cleaning of a printed circuit board (PCB) before conformal coating application is normally done for two key reasons:
- Contamination removal
- Process improvement
They have different effects on the lifetime of the circuit board but can be equally important.
The removal of contaminants from the surface of a printed circuit board before coating application could be important.
The contamination may be harmful and affect the long-term reliability of the circuit. Defects like corrosion can be devastating to a circuit performance in the field.
Also, applying the coating over the contamination will not necessarily improve the reliability.
Therefore, cleaning the PCB before coating could be advantageous.
Cleaning can aid the conformal coating application process.
It could avoid conformal coating defects like de-wetting and delamination. It can also help promote adhesion of the coating to the PCB.
The surface preparation can be extremely important, especially where some conformal coatings may have compatibility issues with the circuit board.
Therefore, cleaning a PCB before conformal coating may improve the coating quality and minimise defects.
What types of contamination may be present on a circuit board?
Cleaning is used to remove many different types of contaminants from the manufacturing and assembly processes.
They can affect the long-term reliability of the circuit after conformal coating.
The residues can come from many areas including:
- Board laminate manufacture
- Component manufacture
- Soldering assembly processes (fluxes)
- Glue and ruggedizing processes
- Operator handling (finger prints, hair)
- Machine contamination (oils and greases)
- Environmental contamination (dust)
Removing the contamination may be a priority depending on their harmfulness.
How should I clean the printed circuit board?
Cleaning circuit boards before coating is a huge topic by itself.
Successful cleaning of circuits can be achieved by a variety of techniques.
These cleaning techniques include:
- Solvent & chemical
The key to success in cleaning is similar to the success made with coating.
You need to match the cleaning process, materials and the circuit board together.
This will give the best results for application of the conformal coating.
How do I validate my cleaning process?
There are many techniques that can be used to measure cleanliness. They include many IPC test methods.
The techniques available include:
- Ionic Contamination Testing (ROSE)
- Ion Chromatography (IC) or High Performance Ion Chromatography (HPLC)
- Surface Insulation Resistance (SIR) testing
Further information can be found in the IPC HDBK 001 on different cleanliness assessment methods or talk to us.
Need to find out more?
Click conformal coating cleaning for further information or contact us directly and we can help you.