Differential Copper PCBs have the characteristic of requiring different heights or weights of copper on the same layer.
A subcategory of Differential Copper PCBs are Bump Plated PCB's, wherein selected pads are plated up much higher than the surrounding copper to enable the PCB to stand off the surface of another PCB.
The primary categories of Differential Copper PCBs that we produce are Sculptured Flex PCBs and Bump Plated PCBs. Sculptured flex circuits typically are formed to shape and have exposed metal fingers that allow for bare metal connections (like a plug-in) and remain strong at the solder joint formation. Sculptured fingers provide a more reliable alternative to mechanically fastened crimp pins.
They can also be specially made to have copper conductors varying in depth & thickness in different places. The copper is thin at the most flexible part of the circuit and thick at the interconnection point. They make for an elegant method of combining a flex PCB and pin connector, with a huge benefit in space and assembly time savings. Most often they are created through a sequential etch down process that requires a great deal of pre-engineering and process control.
Bump Plated PCBs make the use of heavily plated SMT pads (plated up > 5 mils) that allow the PCB to be soldered to another PCB. As such, these boards tend to be smaller in side as they are often used as a discrete component that is assembled to another PCB.