"Small Cooling Fan" bearing system generally recommend the best selection of ball bearings, fan heat fan because life often depends on the reliability of its bearings, ball bearing system has been shown to have the characteristics of high efficiency and low heat generation. Belong to rolling friction ball bearing, metal beads by rolling contact surface is small, the friction coefficient is small; and "Small Cooling Fan" oil-bearing sliding friction, a large contact surface, after long-term use, the oil will be volatile, bearing easy to wear, friction coefficient late noisy, short life. Oil-bearing fan used copper-based powder is made by sintering, "Small Cooling Fan" require the use of oil-bearing lubricating sliding friction to reduce the number of modulation by lithium grease lubricating system oil from Stuttgart.