Electromigration and Flux Residues

Electromigration and its subcategory electrochemical migration is a serious problem in electronic industry working with printed circuit boards (PCB). Smaller equipment with high density of interconnection (HDI) is assembled with surface mounted devices (SMD) and through hole components (THC) Assembly techniques are realised mainly by soldering process with no clean fluxes. Result is not only a reliable solder joint, but also flux residues. The first part of the article after short theory is focused on gatering basic knowledge about fluxes and surface finishes by using cyclic voltammetry (CV) and electrochemical impedance spectrometry (EIS). The second part of the experiments is oriented on practical test with different fluxes for wave and reflow soldering. These tests are associated with the reduction of surface insulation resistance, corrosion, dendrite/fiber growth and the formation of subsequent short circuits. The acceleration of these electrochemical reactions is helped by higher working temperatures, higher humidity, and magnitude \ and frequency of electrical voltage between the conductors.