The invention discloses a circuit board assembly and a mobile terminal. The circuit board assembly comprises a circuit board, an antenna and a proximity sensor, wherein the circuit board comprises a top layer, a bottom layer and at least one middle layer; the top layer is arranged on the opposite side of the bottom layer, and the middle layer is positioned between the top layer and the bottom layer; the antenna is connected to the bottom layer, and the antenna and the bottom layer are connected to a feed point; the proximity sensor is arranged on the top layer, the proximity sensor is arrangedat the position corresponding to the feed point, and the proximity sensor comprises a plurality of packaging pings; A connecting circuit electrically connected with the packaging pins is paved on thecircuit board, the middle layer comprises a paving layer, a shielded area covered with a conductive material is formed on the paving layer, and the orthographic projections of the connecting circuitand the packaging pins on the paving layer are positioned in the shielded area. Due to the fact that the shielded area is arranged between the feed point of the antenna and the proximity sensor, and radiation emitted by the circuit between the feed point and a matching circuit from the feed point to the antenna is shielded by the shielded area but cannot influence the proximity sensor, so that normal operation of the proximity sensor is guaranteed.