Unsolderability

Unsolderability refers to the condition where a component or a pad on a printed circuit board (PCB) cannot be properly soldered using standard soldering techniques. This means that solder will not wet or adhere to the surface, preventing a reliable electrical and mechanical connection. Several factors can contribute to unsolderability.

One common cause is oxidation of the metal surfaces. When copper or component leads are exposed to air for extended periods, they can form oxides that act as a barrier, preventing solder from making direct contact. Plating finishes on PCBs, such as tin, nickel, or gold, can also degrade over time or if stored improperly, leading to unsolderability. Contamination from oils, grease, or flux residues can also create a surface that solder cannot bond to.

Manufacturing defects can also result in unsolderable components or pads. Inadequate plating thickness, improper surface treatment, or damage during handling can all compromise solderability. For components, internal issues within the component itself, such as contamination of the lead material or poor manufacturing processes, can lead to unsolderability.

Diagnosing unsolderability often involves inspecting the surface for discoloration, pitting, or a dull appearance. Attempting to solder the area with appropriate flux and temperature will also confirm the issue. Solutions typically involve cleaning the surface, if possible, or using specialized fluxes designed to remove stubborn oxides. In cases of severe contamination or degradation, the component or PCB may need to be replaced.