Metallic Coating
Electrolytic metal finishes applied to printed circuit board contacts provide highly conductive paths for signal transmission. In high-frequency designs, electroplated silver offers low electrical resistance and excellent surface planarity. The coating prevents oxidation of the underlying copper during storage.
Solderability Profile
Thermal bonding during board assembly relies on the metal dissolving into the liquid solder to establish a joint. When board designers specify electroplated silver, the dissolution rate must be controlled to prevent the creation of voiding or weak intermetallic zones. The solder alloy rapidly scavenges the surface layer, leaving a clean copper surface behind for the primary structural connection.
High temperatures accelerate this migration, making thermal profiling a critical control step in reflow ovens.
Interface Integrity
Atmospheric exposure represents the main limitation of this finish due to the high reactivity of the metal with sulfur compounds in the air. Over time, the silver tarnishes to form silver sulfide, a compound that degrades the solderability and increases contact resistance. Fabricators prevent this degradation by applying organic surface protectants or by packaging the completed boards in sealed, desiccant-filled bags immediately after the plating process.
This step ensures that the assemblies remain reliable until they reach the assembly line.
