Because electrochemical failure risk is site-specific, different components need different plans.
Highly dense electronic assemblies incorporate bottom-terminated components. Miniaturized components create numerous challenges, resulting in a shorter distance between conductors of opposite polarity, solder sphere size reduction, low-standoff gaps, flux entrapment under the bottom termination, blocked outgassing channels, and more significant potential for leakage currents.1
In the presence of humidity, moisture (mono-layers of water) hydrogen bonds with ionic contaminants to create an electrolytic solution. Ions such as flux activators can dissolve metal oxides present in the flux residue at the soldered connection.2 When the system is in operation, the electrical field attraction of the positively charged metal ions migrate to the negative conductor. These metal ions can plate small dendrites, resulting in leakage currents and/or parasitic leakage. As such, ionic residue testing is used to test for problematic residues that could hinder reliable circuit function.3
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