Corrosion

Definition

Author

• Dr Lee Hitchens, Nexus

Corrosion is the chemical or electrochemical reaction between a circuit board, usually a metal, and its environment, that produces a deterioration of the circuit and its properties.

Corrosion can occur without a conformal coating being present.

A conformal coating can help prevent corrosion as a complete process.

Download our PDF guide Solving conformal coating problems in the application process now.

Causes of corrosion in conformal coating

Factors that influence corrosion and, or electrochemical migration, usually revolve around ionic contamination the cleanliness of a circuit.

These contaminants come from electronic processes such as:

• Board fabrication: The Laminate goes through a lot of chemical processes. The cleaning of the chemicals is crucial to ensure the contaminants are removed.
• Components: Components also can get contaminated. Again, cleanliness is critical
• Assembly equipment: the Equipment used to make the circuit board may add contamination
• Soldering: The flux residues can have a major influence on the reliability of the circuit.
• Operator handling: People can add contamination in a variety of ways
• Incorrect cleaning: The cleaning process may not clean the boards correctly or leave cleaning fluid residues on the circuit due to a failure to rinse the board.

How to prevent corrosion in conformal coating

• Clean the board: It is possible to minimise the majority of corrosion effects by using an effective cleaning process before conformal coating.
• Process control: If you are using a no clean process then tightening up the production process is critical.
• Inspection: Full inspection of Incoming boards and components, for solderability and cleanliness.
• Operator Cleanliness: All operators wear gloves.
• Select the right manufacturing materials: Use “low residue” no clean flux/paste that is harmless to the circuit.
• Solder Process: The soldering window fine-tuned and the system controlled.
• Rework: Low residue wire/flux used for rework.

Download our PDF guide Solving conformal coating problems in the application process now.

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