A backplane connector has a housing and multiple terminal assemblies. The housing has a top, a bottom and an expansion slot defined in the top. The terminal assemblies are mounted in the bottom of the housing and each terminal assembly has a first insulating base, a second insulating base and two pairs of signal transmission terminals. The first and second insulating bases are connected to each other. The pairs of the signal transmission terminals are mounted respectively through the first and second insulating bases. Each signal transmission terminal has a curved guide element and an angled protruding element. The curved guiding elements smoothly contacts and guides an electrical connecting portion of a PCB expansion card to move so that the PCB expansion card is installed easily in the expansion slot of the backplane connector.