A fastening system for a heat sink mounted on a circuit board utilizes a self-clinching stud assembly constructed by axially interfitting two flat sheet metal members. Each member has forked ends which when axially plugged together in criss-cross fashion create a unified fastener with side structures that can permanently clinch into a heat sink. After attachment to the heat sink, the stud presents two opposite attachment ends with tines which extend from the top and bottom of the heat sink. As finally assembled, a fan attaches to the top end of the studs above the heat sink while the opposite end of the stud which extends from the bottom of the heat sink passes through the circuit board to attach to a retaining leaf spring which presses against the back side of the board. Thus, all of the components are joined by a single stud.