Circuit board assembly

A circuit board assembly comprising:

• a motherboard defining a plurality of plug slots;
• and
• a fixing mechanism for securing a heat sink, the fixing mechanism being positioned between two adjacent plug slots and comprising:
• a support member mounted on the motherboard;
• two fixing brackets mounted on opposite ends of the support member, respectively, and each fixing bracket comprising a hook;
• two bars rotatable relative to the fixing brackets and capable of being received in and being released from the corresponding hooks ;
• a connection member detachably connected to the support member via the engagement of the bars and the corresponding hooks;
• wherein opposite borders of the support member extend in the same direction parallel to the plug slots, and the support member forms four connecting portions for securing the heat sink on opposite sides thereof, and the connecting portions are located between the opposite borders, thereby the total width of the fixing mechanism is defined by the opposite borders.