Abstract: The disclosure provides a bolt including a main body, a head portion and a thread portion. The main body has a central axis. The head portion connects the main body. The thread portion is connected to the main body and runs around the central axis. The thread portion has a bearing surface facing toward the head portion. The bearing surface is a continuous curved surface or has an inflection point. The bearing surface includes a concave curved surface, a convex curved surface and a flank surface. The concave curved surface connects the main body. The convex curved surface is located further away from the main body than the concave curved surface. One side of the convex curved surface connects the concave curved surface, and another side of the convex curved surface connects the flank surface.

Abstract: The disclosure provides a bolt including a main body, a head portion and a thread portion. The main body has a central axis. The head portion connects the main body. The thread portion is connected to the main body and runs around the central axis. The thread portion has a bearing surface facing toward the head portion. The bearing surface is a continuous curved surface or has an inflection point. The bearing surface includes a concave curved surface, a convex curved surface and a flank surface. The concave curved surface connects the main body. The convex curved surface is located further away from the main body than the concave curved surface. One side of the convex curved surface connects the concave curved surface, and another side of the convex curved surface connects the flank surface.

Abstract: A chemical conversion coating is provided. The chemical conversion coating is disposed on a surface of a magnesium alloy substrate. The chemical conversion coating includes a first protecting layer. The first protecting layer contains manganese, magnesium and oxygen, and a manganese content of the first protecting layer is between 10 at. % to 20 at. %.

Abstract: A chemical conversion coating is provided. The chemical conversion coating is disposed on a surface of a magnesium alloy substrate. The chemical conversion coating includes a first protecting layer. The first protecting layer contains manganese, magnesium and oxygen, and a manganese content of the first protecting layer is between 10 at. % to 20 at. %.

Abstract: A quad flat package (QDP) structure having an exposed heat sink is provided. The QDP structure includes a leadframe, a chip, a heat sink, an insulating layer and a molding compound. The leadframe includes a die pad and multiple leads surrounding the die pad. The chip is disposed on the die pad and electrically connected to the die pad and the leads. The heat sink has a top surface, a bottom surface opposite thereto, and a side surface connected to the top and the bottom surfaces. The die pad is disposed in a central area of the top surface of the heat sink and electrically connected to the heat sink. The molding compound encapsulates the chip, the die pad, an inner lead portion of each lead and heat sink, and exposes the bottom surface of the heat sink and an outer lead portion of each lead.