Thin fan structure

A thin fan structure comprising:

• a case having a receiving space and a bearing cup protruding from a center of the case into the receiving space, the bearing cup being formed with a bearing hole;
• a fan impeller having a hub section and multiple blades outward extending from a circumference of the hub section, a shaft axially extending from a center of the hub section, the shaft being rotatably disposed in the bearing hole, a magnetic member being annularly disposed on inner circumference of the hub section;
• a circuit board disposed in the receiving space and fitted around the bearing cup;
• a silicon steel sheet disposed on the circuit board, the silicon steel sheet having a base section and multiple first magnetic conductive sections upward protruding from a circumference of the base section, the base section and the first magnetic conductive sections together defining a receiving space;
• and
• a winding assembly fixedly disposed in the receiving space, the winding assembly having a bottom section and a side section, the bottom section being attached to the base section, the side section being correspondingly attached to the first magnetic conductive sections.