A circuit board includes a first circuit area, a first processing unit and a conductive pattern. The first circuit area includes a plurality of first electrically contacts. The first processing unit, which includes a ball grid array (BGA) substrate, is disposed on the first circuit area and is electrically connected to the first electrically contacts. The BGA substrate has a plurality of solder balls and a bypass circuit. The conductive pattern is electrically connected to the first electrically contacts.