Metal Distribution
Inclusion of non-functional copper dots or grids in open areas of a circuit board layout balances the metal distribution across the panel during manufacturing. Thieving pad arrays prevent the concentration of current in isolated regions of the board during the electroplating process. The placement of sacrificial metal patterns draws excess current away from active traces, reducing the likelihood of over-plating.
Their presence ensures a more uniform layer thickness across the entire panel. Designers place these shapes in low-density zones.
Electroplating Efficiency
Without these dummy pads, isolated circuit lines act as high-current areas, attracting more copper ions and growing thicker than the dense areas of the board. This non-uniform plating causes uneven surface heights, which degrades the accuracy of solder paste printing during component assembly. In addition, uniform copper coverage helps to maintain even heat absorption during reflow soldering, reducing the risk of board warping.
By distributing the thermal mass evenly, the array prevents local thermal stress. Mechanical stability is thus maintained across the assembly.
Acceptance Rule
Quality specifications require that these non-functional features remain disconnected from any electrical networks on the board. Electrical testing verifies that no accidental short circuits exist between the active traces and the adjacent pads. Visual inspection ensures that the shapes are complete and free from lifting defects.
Correct layout balancing improves yield.
