Meaning
Electrochemical deposition of metal onto the surfaces and through-holes of a substrate creates the conductive network required for electronic functionality. During printed circuit board plating, copper is typically used to build up the thickness of tracks and to coat the walls of drilled holes. Conductivity is established.
This step follows the initial chemical activation of the non-conductive fiberglass material.
Interconnect Formation
Metal layers deposited in the holes connect the different layers of a multi-layer board to allow signal flow across the entire device. Reliable printed circuit board plating ensures that these vertical interconnect accesses withstand the thermal expansion cycles encountered during soldering. The thickness of the copper must be uniform to prevent signal loss or overheating in high-power circuits.
Deposition Sequence
Immersion in a series of chemical baths prepares the surface before the electrolytic application of the final metal layer. In printed circuit board plating, the board acts as the cathode in a tank where copper ions are reduced and bonded to the surface. Controlling the current density and the chemical balance of the electrolyte is necessary to achieve a smooth and consistent finish.
Surface Protection
Final coatings of gold, silver, nickel or tin-lead are applied over the copper to prevent oxidation and improve solderability for component mounting. Poorly executed printed circuit board plating can lead to issues such as knee-thinning or voiding where the metal does not fully cover the hole walls. Defects are costly.
These defects are often hidden and only become apparent when the finished assembly fails under mechanical stress in the field. Rigid inspection protocols including cross-sectional analysis and x-ray fluorescence testing verify that the plating meets the IPC standards for the specific class of product.
