Micro-Voids

Formation Mechanism

Organic additives in the electroplating bath or trapped volatiles during the soldering process often cause the nucleation of these internal cavities. During copper electroplating, organic compounds like brighteners and levelers can become entrapped in the deposited metal. When the board undergoes thermal cycling or subsequent reflow passes, these entrapped materials outgas, creating micro-voids.

In solder joints, outgassing of flux residues or moisture on the circuit board pad can similarly leave behind small pockets of empty space. The size and density of these cavities are highly dependent on the plating chemistry and board cleanliness.

Structural Impact

Localized voids concentrate stress and promote early crack propagation under thermal or physical loads. High density of micro-voids at the copper-solder boundary reduces the load-bearing area of the joint. This reduction accelerates solder joint fatigue, resulting in open-circuit failures in assemblies subject to harsh operational conditions.