A circuit board (1) is provided comprising a plurality of insulating layers, at least one ground layer and at least one layer comprising signal traces. The circuit board comprises at least a first conductive via (17) and a second conductive via (17). The first conductive via and the second conductive via penetrate through at least a first insulating layer of the plurality of insulating layers and are connected to a signal trace. The first conductive via and the second conductive via are arranged adjacent each other. At least in the first insulating layer the first conductive via and the second conductive via are separated in a first direction of separation (R) by a first adjustment portion comprising a dielectric material property different from the first insulating layer.