The cleanliness of a Printed Circuit Board (PCBA) is crucial to the assembly’s performance and reliability.

Contamination of the printed circuit board can cause severe degradation of insulation resistance and dielectric strength. Harmful residues and contaminants are separated into two main categories: ionic and non-ionic. 

Ionic residue can be described as residue that contains molecules or atoms which are conductive when in a solution.  Exposure to moisture makes ionic residues disassociate into either negatively or positively charged elements, changing the solution’s overall conductivity.

Common sources of ionic residue:

  • Salts
  • Inorganic and organic acids
  • Ethanolamines
  • Perspiration
  • Flux activators
  • Plating chemistries

Non-ionic residues are not conductive and are usually organic species that can remain on the PCB after board fabrication or assembly.

Common sources of non-ionic residue:

  • Resin
  • Oils
  • Greases
  • Hand lotion
  • Silicone

While both ionic and Non-ionic contamination can impact the operation and reliability of the device on which they are present, the effects of ionic contamination is of greater interest to most PCB manufacturers. A higher failure rate is associated with ionic contamination than its Non-ionic counterpart. Corrosion and dendrite growth are the two most common failure modes resulting from ionic contamination. Either can lead to shorts and opens in an electronic circuit, particularly in fine pitch applications or assemblies with high component packing density.

Non-ionic (nonpolar) residue will lead to unwanted impedance because of its insulative properties. This is an issue particularly where plug-in contacts or connectors are utilised. In addition to acting as an unwanted insulator, non-ion contamination on an assembly can cause poor adhesion of solder mask and conformal coating, physical interference with moving parts, encapsulation of ionic contaminants, and retention of foreign debris.

Arrling Services offers you the choice of cleaning.  The cleaning method will depend on the PCB contamination and the coating solution requested.

Printed circuit boards (PCB) in cleaning process to remove ionic and non ionic residue

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