Heat sink restraints for calibrated mating pressure and shock absorption

A heat sink restraint that absorbs shock and facilitates the application of a calibrated hold-down force to a heat sink. The restraint comprises a fluid-tight housing and a piston assembly including a piston and a shaft. The shaft has first and second ends extending from the housing through seals that allow axial movement of the shaft. The piston is disposed within the housing for axial movement with the shaft. A dampening fluid fills the housing about the piston assembly and a dampening orifice or passageway establishes restricted fluid communication between regions within the housing above and below the piston. A spring is disposed within the housing between the piston and the housing to bias the housing in a retaining direction. A first end of the shaft is selectively coupled to a circuit board and the second end includes a visual indicator for indicating the amount of the applied hold-down force.