Method for fabricating a heat pipe, and instrument of the method

A method for fabricating a heat pipe, comprising:

• providing a hollow tube, wherein the hollow tube has an open end and a closed end;
• disposing a mandril into the hollow tube from the open end, wherein an inside wall of the hollow tube is separated from the mandril by a space, and wherein the mandril comprises at least one first portion and at least one second portion and the first portion has a thermal expansion coefficient larger than that of the second portion;
• filling up the space between the mandril and the hollow tube with a powder;
• performing a sintering process to the hollow tube, forcing the powder to form at least one first agglomeration region and at least one second agglomeration region, wherein the first agglomeration region is directly contacted to the first portion and the second agglomeration region is directly contacted to the second portion during the sintering process, and wherein the thickness of the first agglomeration region is less than that of the second agglomeration region;
• removing the mandril after cooling;
• injecting a working fluid into the hollow tube;
• and
• sealing the open end of the hollow tube.