Heat pipe

1. A heat pipe comprising:

a first metal layer having a first surface, and forming a liquid layer configured to move a working fluid that is liquefied from vapor; and

a second metal layer, provided on the first surface of the first metal layer, and forming a vapor layer configured to move the vapor of the working fluid that is vaporized,

wherein the first metal layer includes

a plurality of first cavities caving in from the first surface of the first metal layer and arranged apart from each other, each first cavity of the plurality of first cavities caving in from the first surface towards a center part of the first metal layer in a first direction to a first bottom surface, wherein the first direction is taken along a thickness of the first metal layer and coincides with a direction in which the second metal layer is stacked on the first metal layer,

a plurality of second cavities caving in from a second surface of the first metal layer, opposite to the first surface of the first metal layer, and arranged apart from each other, each second cavity of the plurality of second cavities caving in from the second surface towards the center part of the first metal layer in the first direction to a second bottom surface,

a plurality of first pores linking by passageways to communicate with the plurality of first cavities and the plurality of second cavities, respectively, each first pore of the plurality of first pores linking by a passageway to communicate the first bottom surface and the second bottom surface in a plan view of the first metal layer viewed in the first direction, and

a plurality of second pores linking by passageways to communicate inner walls of adjacent second cavities of the plurality of second cavities that are adjacent to each other along a second direction perpendicular to the first direction, respectively,

wherein the plurality of second pores are located at positions not overlapping the plurality of first pores along each of the first direction, the second direction, and a third direction which is perpendicular to each of the first and second directions,

and

wherein the second metal layer has a picture-frame shape in the plan view, an inner sidewall defining an inner contour of the picture-frame shape in the plan view, and an opening defined by the inner sidewall and penetrating the second metal layer in the first direction, thereby exposing the plurality of cavities through the opening in the plan view.

2. The heat pipe according to claim 1 , further comprising:

a third metal layer provided on a first surface of the second metal layer opposite from a second surface of the second metal layer in contact with the first surface of the first metal layer, and

a fourth metal layer provided on the second surface of the first metal layer,

wherein the plurality of first cavities, the plurality of second cavities, and the plurality of first pores form a plurality of through-holes arranged in a matrix arrangement.

3. The heat pipe according to claim 2 , further comprising:

a plurality of pillars provided within the opening, between the first surface of the first metal layer and the third metal layer.

4. The heat pipe according to claim 1 , wherein an area of a part of each first cavity of the plurality of first cavities opening at the first surface of the first metal layer is smaller than an area of a part of each second cavity of the plurality of second cavities opening at the second surface of the first metal layer.

5. The heat pipe according to claim 1 , wherein

each first cavity of the plurality of first cavities has a tapered shape defined by inner walls thereof that widen from a corresponding first pore of the plurality of first pores towards the first surface of the first metal layer, and

each second cavity of the plurality of second cavities has a tapered shape defined by the inner walls thereof that widen from a corresponding first pore of the plurality of first pores towards the second surface of the first metal layer.

6. The heat pipe according to claim 1 , wherein two or more first cavities of the plurality of first cavities link by passageways to communicate with one second cavity of the plurality of second cavities.

7. The heat pipe according to claim 1 , wherein the plurality of first cavities include first cavities opening at the first surface of the first metal layer with mutually different areas.

8. The heat pipe according to claim 1 , further comprising:

a first region having the plurality of first cavities arranged at a first density in the plan view; and

a second region having the plurality of first cavities arranged at a second density lower than the first density in the plan view.

9. The heat pipe according to claim 2 , further comprising:

a first region having the plurality of first cavities arranged at a first density in the plan view; and

a second region having the plurality of first cavities arranged at a second density lower than the first density in the plan view.

10. The heat pipe according to claim 5 , further comprising:

a first region having the plurality of first cavities arranged at a first density in the plan view; and

a second region having the plurality of first cavities arranged at a second density lower than the first density in the plan view.

11. The heat pipe according to claim 1 , wherein the first metal layer has a single-layer structure.

12. The heat pipe according to claim 1 , wherein the inner sidewall of the second metal layer surrounds the opening in the plan view.

13. The heat pipe according to claim 1 , wherein an outer contour of the picture-frame shape, defined by an outer sidewall of the second metal layer, has a rectangular shape in the plan view.

14. The heat pipe according to claim 1 , wherein the opening in the second metal layer has a rectangular shape in the plan view.