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Multiple Wash Steps Affecting Resistance Characteristics

Question: We have a customer that believes that multiple wash steps is the cause of 0805 resistor failures. They claim that it is devaluing the part. I have never heard of this issue. Could you shed some light on this?

Answer: Surface mount resistors being impacted by the cleaning operation may happen, but one would need to look at the component itself to make sure the resistive ink is properly cured and that the cleaning solvent is not dissolving the resistive ink. This is all part of the qualification process when component are selected or when cleaning solvents are selected for manufacturing.

For example if the cleaning solvent is an aqueous solution, the pH is very high and this alkalinity may affect the resistive element of the chip resistor.

The other issue may be the glass frit on the resistive element, it may be missing, which would, or could, impact the functionality of the resistive element against the solvent to which it will be exposed. I would also tend to think that the fluxes from the soldering operation could also impact the resistive element, whereas instead of impacting the functionality of the resistive element it remains on the resistive element and changes the electrical functionality of the component, as some of these residues are conductive and could also impact the performance of the chip component.

Many reasons could cause this issue, so my suggestion would be to have the component sent to a lab for surface analysis to determine whether or not the problem is contamination or deterioration of the resistive element.