JP2009092344A - Vapor chamber with superior heat transport characteristic - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vapor chamber with a superior heat transport characteristic, thanks to large transport amount of a working liquid. <P>SOLUTION: In the vapor chamber transporting heat by phase change between vaporization and condensation of the working liquid sealed in a container, a wick provided in an inner wall of the container is comprised of a porous sintered body having a frame formed by sintering metal powder around a pore, and silicon oxide is applied to the surface of the frame. The vapor chamber with the superior heat transport characteristic can be applied to cooling of a multiprocessor (MPU) or the like of a computer server, or application needing quietness in an apparatus wherein noise in using a fan for cooling becomes a problem such as a large liquid crystal or plasma display. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vapor chamber used, for example, as a heat dissipation means for a semiconductor chip.

  In recent years, as the performance of semiconductor chips increases, the amount of heat generated per unit area has been increasing. Therefore, as a heat dissipation means, there has been a limit in the heat diffusion by the conventional metal plate, so a heat pipe that dissipates the heat away from the semiconductor chip by moving the heat in the longitudinal direction has been proposed. Yes. Recently, a vapor chamber that can diffuse heat not only in the longitudinal direction but also in a two-dimensional direction has attracted attention.

The vapor chamber transports heat by the phase change of evaporation and condensation of the working liquid sealed in the container. And the inner wall of a container has the basic structure provided with the wick for performing evaporation and condensation of said working liquid (patent document 1).
Japanese Patent Laid-Open No. 2004-238672

  The method of Patent Document 1 is an effective technique for increasing the efficiency of evaporation and condensation of the working liquid by adopting a porous body in the wick. However, the porous body used in this wick has room for further improvement in terms of increasing the transport amount of the working liquid. In other words, the conventional wick manufactured by simply sintering metal powder transports the working liquid to the heat source by using the capillary force of the pores formed by the gaps between the old raw material powder after sintering. It was a structure. In this case, the void ratio of the wick is about 50% at the maximum, and thus the transport amount of the working liquid is limited.

  In addition, in a wick made of a porous metal body, the metal itself exposed on the surface comes into contact with the working liquid, so if a reactant is generated by this contact, it will block the wick's pores and operate. This will inhibit the movement of the liquid. Furthermore, since it can be a corrosive factor for the container, the durability is remarkably impaired.

  Accordingly, an object of the present invention is to provide a vapor chamber with improved heat transport properties and improved heat transport performance.

  As a result of considering the above-mentioned conventional drawbacks, the present inventor has improved the transportability of the working liquid of the wick itself by a predetermined sintered structure and surface modification, and the heat transport characteristics of the vapor chamber as a whole. It has been found that it contributes greatly to the improvement of

  That is, according to the present invention, in the vapor chamber that transports heat by the phase change of evaporation and condensation of the working liquid sealed in the container, the wick provided on the inner wall of the container has the metal powder sintered around the pores. A vapor chamber having excellent heat transport characteristics, characterized in that it is made of a porous sintered body having a skeleton, and silicon oxide is applied to the surface of the skeleton.

  According to the present invention, by improving the structure and surface form of the wick itself, the capability of transporting the working liquid by the capillary force is improved, so that it is possible to achieve excellent heat transport characteristics of the vapor chamber.

  As described above, an important feature of the present invention is that, in addition to the skeleton structure of the wick incorporated in the vapor chamber, the surface morphology is also improved. In other words, a wick made of a porous sintered body having a skeleton obtained by sintering metal powder around the pores and having a silicon oxide added to the surface of the skeleton, for example, a vapor chamber as shown in FIG. The wick is disposed on the evaporation section side and / or the aggregation section side (in FIG. 1, wicks are disposed on both the evaporation section side and the aggregation section side). That is, in the vapor chamber 1 that transports heat by the phase change of evaporation and condensation of the working liquid 3 enclosed in the container 2, the wick 4 is provided on the inner wall of the container 2. The present invention will be described below.

  First, a porous sintered body having a skeleton formed by sintering metal powder around the pores was applied to the basic structure of the wick. FIG. 2 is a scanning electron micrograph showing an example of a porous sintered body constituting the wick used in the present invention. The used metal powder is an electrolytic copper powder having an average particle size of 103 μm, and as will be described later, the average particle size of the resin particles used for forming the pores is 180 μm. In other words, by forming this structure, in addition to the conventional pores consisting of the gaps between the old raw material powders of the sintered portion, there are also the above-mentioned pore portions having a diameter larger than the pores, so that Due to the excellent capillary force, a high transport capacity of the working liquid is achieved.

  More specifically, in addition to the pores of the skeleton formed by sintering the metal powder, by introducing pores having a larger diameter than the pores, pores of an appropriate size can be obtained. By increasing the porosity of the wick, this ensures more space that contributes to the transport of the working liquid. Since the holes communicate with each other, the resistance when the working liquid passes through the flow path can be reduced, so that the transporting ability of the working liquid is further improved. In addition, depending on the usage environment, if the above pore diameter is set large and communicated with the surface more, even if a sufficient amount of working liquid is absorbed, the air permeability due to the presence of additional space can be increased. Ensured and the surface area for evaporation or agglomeration of the working liquid can be increased.

  The diameter and volume ratio of the pores in the skeleton and the pores surrounded by the skeleton can be designed according to the transport capacity and cohesiveness of the wick working fluid required according to the specifications of the vapor chamber. is there. Furthermore, it is also possible to have these distributions in the thickness direction and the surface direction of the wick.

  The skeleton surface of the porous metal sintered body constituting the wick is coated with a hydrophilic substance so that the capillary force achieved by the skeleton structure is maximized by the interaction. The That is, this is a technique of coating the skeleton surface with silicon oxide having excellent wettability. If the silicon oxide film is densely coated, the reaction with the above-described working liquid can be prevented, so that the durability is improved.

  In addition, the technique of coating the skeleton surface with silicon oxide has further advantages. That is, if copper, copper alloy, etc. with high heat conductivity are employ | adopted for the metal powder which forms a porous body, those metal seed | species shows water repellency depending on conditions. However, even in such a case, with the present invention in which the surface of the skeleton in contact with the working liquid is coated with silicon oxide having excellent hydrophilicity, the wick substrate having high thermal conductivity has a stable capillary force. It can be achieved.

  In addition to the oxidation treatment, chemical conversion treatment, and chemical vapor deposition (CVD) treatment, a solution such as silicon alkoxide may be used as the silicon oxide film coating means of the present invention. In the case of a coating treatment with an alkoxide, it is important to adjust the viscosity so that the coating substance does not block the pores of the skeleton.

  As a method for manufacturing the vapor chamber of the present invention, for example, the following method can be applied.

  First, a metal powder as a raw material is prepared. As a kind of metal powder, copper or copper alloy with high heat conductivity, or aluminum or aluminum alloy is preferable. The average particle size is preferably about 100 μm or less.

  Next, resin particles for forming pores and a binder are mixed with the metal powder to prepare a kneaded body. The average particle size of the resin particles is preferably 100 to 1000 μm. A binder made of resin can also be used, but on the other hand, especially when the amount of resin particles is increased to increase the amount of pores, the removal of the resin particles depends on the solvent before heating and degreasing. Applying the dissolution extraction method is effective in obtaining a sound sintered body that generates less gas during heat degreasing and has no defects such as cracks. Therefore, when applying an effective method of removing the resin particles with a solvent, it is effective to use a binder that does not dissolve in the solvent, for example, methyl cellulose or polyvinyl alcohol and water as main components. is there.

  Then, a wick-shaped molded body, for example, a sheet-shaped molded body is produced from the kneaded body, and this is heated and degreased and sintered to obtain a wick. Here, when the binder contains water, it is preferable to put a drying step after molding, and when removing the resin particles with a solvent, it is possible to provide a solvent extraction and drying step before heat degreasing, preferable.

  Then, the wick obtained by sintering is bonded to the inner wall (the working liquid evaporation part and / or the agglomeration part) of the container part before assembly in the vapor chamber by, for example, thermal diffusion or brazing material. In this bonding step, the wick is placed in the inner wall of the container part in the state of the molded body before heating degreasing and sintering, and then heat degreasing and sintering are performed. It can also be bonded and integrated.

  Then, after applying a silicon oxide coating process to the wick part (frame surface), these parts are assembled to complete a vapor chamber spare body, and finally, through a process such as sealing of the working liquid, The vapor chamber is completed.

  The vapor chamber of the present invention having excellent heat transport characteristics has a problem of noise when a fan is used for cooling, such as a large liquid crystal or a plasma display, in addition to cooling for a multiprocessor unit (MPU) of a computer server. In such a device, application to uses that require quietness is also conceivable.

It is a schematic diagram which shows an example of cross-sectional structure of the vapor chamber of this invention. It is a scanning electron micrograph which shows an example of the wick used for the vapor chamber of this invention.

Explanation of symbols

  1. 1. vapor chamber; Container, 3. 3. working liquid; Wick

Claims (1)

In the vapor chamber that transports heat by the phase change of evaporation and condensation of the working liquid enclosed in the container, the wick provided on the inner wall of the container has a porous structure with a metal powder sintered around the pores. A vapor chamber having excellent heat transport characteristics, wherein the vapor chamber is made of a sintered body and silicon oxide is applied to the surface of the skeleton.