Backplane PCBs are special type of multilayer PCBs. Typically they have connectors where daughter cards can be plugged in. Unlike soldering the pins into the holes these connectors are press fit into the backplane PCB holes. This approach prevents the PCBs from experiencing high soldering temperatures. Allows them to be thicker without worrying about the plated through holes fail in Z-axis expansion.
Currently most of the backplane PCBs are utilized in large scale routers, switches and servers that form the backbone of the Internet. The need for high data path bandwidth has resulted in signal speeds reaching, up to 28 Gb/s on these backplanes. However at speeds the parasitic capacitance caused by the plated through holes required for press fit connectors can impact performance negatively. To address this issue fabricating these backplanes often involves removing parts of plated through holes through drilling making the fabrication process more complex.