Design Ratio
Ratio of conductive copper area to the total board area on a given circuit layer determines the distribution of current and resin flow during manufacturing. Pattern factor measures this spatial distribution of copper across the panel surface to guide both etching and electroplating processes. This dimensionless value varies across different regions of a layout depending on trace density.
Highly concentrated circuit paths increase the local value, while sparse regions lower it. Engineers calculate this value to optimize copper distribution.
Manufacturing Influence
Uneven trace density across a layer causes imbalances in the electroplating bath where regions of low pattern factor receive excessive current density. This imbalance leads to over-plating, resulting in thick traces and potential short circuits. Conversely, regions of high density receive less current, leading to under-plated features that may fail electrical testing.
During laminate compression, areas with low copper density require more resin flow to fill the empty spaces, which can lead to local resin starvation if not balanced. Laying down copper dummy pads, also known as copper thieving, resolves these local imbalances.
Plating Boundary
Computer-aided manufacturing software analyzes the layout to identify areas with extreme values of this metric before production. Designers add auxiliary copper shapes to bring the overall layout into a balanced range. Ensuring a uniform pattern prevents localized plating variations.
Balanced designs yield consistent board thicknesses.
