VAPOR CHAMBER AND METHOD FOR PRODUCING VAPOR CHAMBER

A vapor chamber has a working fluid in an internal space formed between a first metal sheet and a second metal sheet, in which the first metal sheet includes a recessed channel and at least one projecting part. The recessed channel is provided at an inner surface of the first metal sheet; the projecting part projects from the inner surface of the first metal sheet toward the second metal sheet, and a top face of the projecting part abuts the second metal sheet. The vapor chamber includes at least one top face joining part and gap flow channel part, the top face joining part joins part of the top face of the projecting part and the second metal sheet, and the top face and the second metal sheet are separated at the gap flow channel part.

TECHNICAL FIELD

The present disclosure relates to a vapor chamber and a manufacturing method of a vapor chamber.

BACKGROUND ART

Electronic components such as semiconductor elements mounted in electrical/electronic devices such as notebook computers, digital cameras and mobile telephones are in a trend of increasing heat generation amount, due to the high-density mounting accompanying improved performance. In order to correctly drive an electrical/electronic device over a long period, it is necessary to efficiently cool the electronic components.

For example, Patent Document 1 discloses a vapor chamber having a first metal sheet and a second metal sheet, and including a liquid flow passage part in a sealed space provided between the first metal sheet and the second metal sheet. In the vapor chamber of Patent Document 1, for each groove constituting the liquid flow passage part, the width of a first communication groove is larger than the width of a first main flow groove and the width of a second main flow groove, the width of a second communication groove is larger than the width of the second main flow groove and the width of a third main flow groove, the depth of the first communication groove is deeper than the depth of the first main flow groove and the depth of the second main flow groove, and the depth of the second communication groove is deeper than the depth of the second main flow groove and the depth of the third main flow groove.

In the vapor chamber of Patent Document 1, the first metal sheet and the second metal sheet are joined by diffusion bonding, brazing or the like. When performing diffusion bonding or brazing, the first metal sheet and the second metal sheet are heat treated and annealed as a whole. Since the entirety of the vapor chamber is annealed in this way, the mechanical strength of the vapor chamber decline. In addition, in the vapor chamber of Patent Document 1, an improvement in heat transport efficiency is achieved by each groove constituting the liquid flow passage part satisfying a predetermined relationship. However, it is insufficient in addressing the demand of cooling performance of the electrical/electronic device which are increasing in recent years.

DISCLOSURE OF THE INVENTION

Problems to be Solved by the Invention

An object of the present disclosure is to provide a vapor chamber superior in mechanical strength and heat transport characteristic and a manufacturing method of the vapor chamber.

Means for Solving the Problems

According to a first aspect of the present disclosure, a vapor chamber includes a working fluid in an internal space formed between a first metal sheet and a second metal sheet, in which the first metal sheet comprises a recessed channel and at least one projecting part; the recessed channel is provided at an inner surface of the first metal sheet; the projecting part projects from the inner surface of the first metal sheet toward the second metal sheet, and a top face of the projecting part abuts the second metal sheet; the vapor chamber includes at least one top face joining part and gap flow channel part; the top face joining part joins part of the top face of the projecting part and the second metal sheet; and the top face and the second metal sheet are separated at the gap flow channel part.

According to a second aspect of the present disclosure, in the vapor chamber as described in the first aspect, the gap flow channel part is provided between a top face abutting part not joined to the second metal sheet in the top face of the first metal sheet, and an inner surface abutting part of the second metal sheet abutting the top face abutting part; the gap flow channel part has a sealed part at a top face joining part side of the top face abutting part; and the gap flow channel part has an opening part at a projecting part lateral face side of the top face abutting part.

According to a third aspect of the present disclosure, in the vapor chamber as described in the second aspect, the gap flow channel part has a longer gap length from the sealed part to the opening part than a gap width between the top face abutting part and the inner surface abutting part.

According to a fourth aspect of the present disclosure, in the vapor chamber as described in the second or third aspect, the gap flow channel part has an average value of a gap width between the top face abutting part and the inner surface abutting part of 1.0 μm or more and 100.0 μm or less.

According to a fifth aspect of the present disclosure, in the vapor chamber as described in any one of the second to fourth aspects, the gap flow channel part has an average value of a gap length from the sealed part to the opening part of 40.0 μm or more.

According to a sixth aspect of the present disclosure, in the vapor chamber as described in any one of the second to fifth aspects, the gap flow channel part includes a gap enlarged part at a sealed part side; and an average value of a gap width between the top face abutting part and the inner surface abutting part at the gap enlarged part is larger than an average value of the gap width at the gap flow channel part other than the gap enlarged part.

According to a seventh aspect of the present disclosure, in the vapor chamber as described in any one of the first to sixth aspects, a ratio (t2/t1) of a sheet thickness t2at the projecting part of the first metal sheet relative to a sheet thickness t1at the recessed channel of the first metal sheet is 0.1 or more and 10.0 or less.

According to an eighth aspect of the present disclosure, in the vapor chamber as described in any one of the first to seventh aspects, the projecting part extends along a longitudinal direction of the vapor chamber.

According to a ninth aspect of the present disclosure, in the vapor chamber as described in any one of the first to eighth aspects, the vapor chamber includes a plurality of the top face joining parts at one of the projecting parts.

According to a tenth aspect of the present disclosure, in the vapor chamber as described in any one of the first to ninth aspects, the second metal sheet includes at least one projecting part at an inner surface; and the projecting part of the second metal sheet projects from the inner surface of the second metal sheet toward the first metal sheet, and a top face of the projecting part abuts the recessed channel of the first metal sheet.

According to an eleventh aspect of the present disclosure, a manufacturing method of the vapor chamber as described in any one of the first to tenth aspects includes: a laser bonding step of forming the top face joining part by laser.

According to a twelfth aspect of the present disclosure, the manufacturing method of the vapor chamber as described in the eleventh aspect further includes a laser welding step of welding an outer edge of the first metal sheet and an outer edge of the second metal sheet by laser, before or after the laser bonding step.

According to a thirteenth aspect of the present disclosure, the manufacturing method of the vapor chamber as described in the eleventh or twelfth aspect further includes a press processing step of forming the recessed channel and the projecting part of the first metal sheet by press molding, prior to the laser bonding step and the laser welding step.

Effects of the Invention

According to the present disclosure, it is possible to provide a vapor chamber superior in mechanical strength and heat transport characteristic and a manufacturing method of the vapor chamber.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment will be explained in detail.

The present inventors, as a result of thorough examination, achieved an improvement in mechanical strength and heat transport characteristics, by focusing on the configuration of a joining part which joins the first metal sheet and the second metal sheet.

A vapor chamber of the embodiment includes a working fluid in an internal space formed between a first metal sheet and a second metal sheet, in which the first metal sheet comprises a recessed channel and at least one projecting part; the recessed channel is provided at an inner surface of the first metal sheet; the projecting part projects from the inner surface of the first metal sheet toward the second metal sheet, and a top face of the projecting part abuts the second metal sheet; the vapor chamber includes at least one top face joining part and gap flow channel part; the top face joining part joins part of the top face of the projecting part and the second metal sheet; and the top face and the second metal sheet are separated at the gap flow channel part.

First Embodiment

FIG.1is a perspective view showing an example of a vapor chamber according to a first embodiment.FIG.2is an enlarged cross-sectional view of a plane A inFIG.1. For convenience,FIG.1shows an aspect partially penetrating so that the internal structure of the vapor chamber is understood. In addition,FIGS.1and2show the flow direction of the gas-phase working fluid F(G) by the black arrows, and show the flow direction of the liquid-phase working fluid F(L) by the white arrows.

As shown inFIGS.1and2, the vapor chamber1of the first embodiment has a first metal sheet10and a second metal sheet20. The first metal sheet10and the second metal sheet20are joined so that an inner surface10aof the first metal sheet10and an inner surface20aof the second metal sheet20are opposing. In other words, the first metal sheet10and the second metal sheet20have the insides closed. In addition, the vapor chamber1has a working fluid in an internal space S formed between the first metal sheet10and the second metal sheet20. The internal space S is sealed by the first metal sheet10and the second metal sheet20. The working fluid is enclosed in the internal space S provided inside of the vapor chamber1.

As the working fluid enclosed in the internal space S, pure water, ethanol, methanol, acetone, etc. can be exemplified from the viewpoint of cooling performance of the vapor chamber1.

The first metal sheet10constituting the vapor chamber1includes a recessed channel11and at least one projecting part12.

As shown inFIG.1, the recessed channel11is provided at the inner surface10aof the first metal sheet10. The recessed channel11provided on the side of the inner surface10aindents from an outer edge10cof the first metal sheet10along the center of the inner surface10a.For example, the recessed channel is a space from the internal space S excluding the projecting part12and gap flow channel part14. The gas-phase working fluid mainly flows in the recessed channel11.

The projecting part12projects from the inner surface10aof the first metal sheet10toward the inner surface20aof the second metal sheet20. A top face13of the projecting part12abuts the inner surface20aof the second metal sheet20. For example, the projecting part12is a square columnar shape.

As shown inFIG.2, the vapor chamber1includes at least one top face joining part13aand a gap flow channel part14.

The top face joining part13ajoins part of the top face13of the projecting part12and the second metal sheet20. In this way, at the abutting surface between the top face13of the projecting part12and the inner surface20aof the second metal sheet20, the top face joining part13ajoins part of the top face13of the projecting part12and part of the inner surface20aof the second metal sheet20.

The vapor chamber1locally possesses an annealed part50at a portion adjacent to the top face joining part13a,rather than over the entirety of the vapor chamber1. The annealed part50is produced by heating when forming the top face joining part13awhich joins the first metal sheet10and the second metal sheet20. For example, as shown inFIG.2, the vapor chamber1possesses the annealed part50formed at the second metal sheet20adjacent to the top face joining part13a.The metallographic structure of the annealed part50and the metallographic structure of the portion other than the annealed part50clearly differ when observed by SEM.

The first metal sheet10and the second metal sheet20are joined via the top face joining part13a.The length13axof the top face joining part13awhich joins part of the top face13and part of the inner surface20ais smaller than the length12xof the projecting part12. From the viewpoint of suppressing a decline in mechanical strength of the vapor chamber1, the ratio (13ax/12x) of the length13axof the top face joining part13arelative to the length12xof the projecting part12is preferably smaller than 0.5. The length13axof the top face joining part13aand the length12xof the projecting part12are distances in a direction perpendicular to the thickness direction of the vapor chamber1, in a cross section of the vapor chamber1including the top face joining part13asuch as that shown inFIG.2.

At the gap flow channel part14, the top face13of the first metal sheet10and the second metal sheet20are separated. The liquid-phase working fluid flows in the gap flow channel part14.

Such a gap flow channel part14is provided between the top face abutting part13bof the top face13of the projecting part12and an inner surface abutting part21of the second metal sheet20. The top face abutting part13bof the first metal sheet10is a portion of the top face13of the first metal sheet10which is not joined to the inner surface20aof the second metal sheet20. The inner surface abutting part21of the second metal sheet20is a portion of the inner surface20aof the second metal sheet20which abuts the top face abutting part13b.

The top face abutting part13band the inner surface abutting part21are separably abutting each other without being joined. The gap flow channel part14is a gap occurring at the abutting of the top face abutting part13band the inner surface abutting part21. It should be noted that, herein for convenience, a state in which the top face abutting part13band the inner surface abutting part21are clearly distanced is shown so as to facilitate understanding the gap flow channel part14.

In addition, the gap flow channel part14has a sealed part14aat a top face joining part13aside of the top face abutting part13b.The sealed part14ais a portion at which the top face abutting part13band the top face joining part13aconnect, and is sealed by the top face joining part13a.In addition, the gap flow channel part14has an opening part14bat a projecting part lateral face side of the top face abutting part13b.The projecting part lateral face side is a lateral face12aside of the projecting part12, which is a recessed channel11side. In this way, in the gap flow channel part14, the top face joining part13aside of the top face abutting part13bis sealed, and the projecting part lateral face side of the top face abutting part13bis open.

The gap flow channel part14is provided at a top face13side of the projecting part12, between the recessed channel11and the top face joining part13a.At the top face13side of the projecting part12, the gap flow channel part14provided at the circumference of the top face joining part13aextends in a direction perpendicular to the thickness direction of the vapor chamber1. The gap flow channel part14communicates with the recessed channel11via the opening part14b.More specifically, the gap flow channel part14communicates with the recessed channel11at a side of the second metal sheet20.

The gap width14wof the gap flow channel part14is very small compared to the groove interval p of the recessed channel11. The gap width14wof the gap flow channel part14is the distance between the top face abutting part13band the inner surface abutting part21. The groove interval p of the recessed channel11is the distance between adjoining projecting parts12or the distance between a projecting part12and an outer edge10c.As described above, the gap flow channel part14is a gap occurring at the abutting of the top face abutting part13band the inner surface abutting part21, and the gap width14wof the gap flow channel part14is very small. For this reason, the gap flow channel part14exhibits a capillary phenomenon relative to the liquid-phase working fluid.

The vapor chamber1cools the heat generating body30mainly by the following cooling path.

The heat generated by the heat generating body30thermally connected with the outer surface20bof the second metal sheet20is transferred to the evaporation part41positioned at the inner surface20aof the second metal sheet20. The evaporation part41causes the liquid-phase working fluid flowing in the gap flow channel part14to evaporate and phase change to gas-phase working fluid as shown by the arrow F(G) as shown inFIG.2, by the heat transferred from the heat generating body30. The gas-phase working fluid heated by evaporation flows to the condensation part42at a position distanced from the evaporation part41, as shown by the arrow F(G) inFIG.1. In the course of the gas-phase working fluid flowing toward the condensation part42, the temperature of the working fluid drops. In the condensation part42, the gas-phase working fluid which has dropped in temperature is condensed and phase changes to the liquid-phase working fluid. The latent heat generated by phase change is transferred to the first metal sheet10or the second metal sheet20, and is radiated to outside of the vapor chamber1. The condensed liquid-phase working fluid easily infiltrates into the gap flow channel part14by the capillary phenomenon as shown by the arrow F(L) inFIG.2. The liquid-phase working fluid migrates in the gap flow channel part14and returns to the evaporation part41again. By such favorable circulation of the liquid-phase working fluid and the gas-phase working fluid, the vapor chamber1can efficiently cool the heat generating body30.

When the vapor chamber1includes the gap flow channel part14at the top face13side of the projecting part12, the liquid-phase working fluid easily infiltrates the gap flow channel part14from the recessed channel11and the liquid-phase working fluid in the gap flow channel part14hardly leaks to outside of the gap flow channel part14, by the capillary phenomenon of the gap flow channel part14relative to the liquid-phase working fluid. On the other hand, in a conventional vapor chamber not including such a gap flow channel part14, since a configuration corresponding to the gap flow channel part14of the vapor chamber1is not provided, the liquid-phase working fluid flows in the recessed channel. In this way, compared to conventional, in the vapor chamber1including the gap flow channel part14, the retention amount of the liquid-phase working fluid increases, and the recirculation amount of the working fluid increases. For this reason, the heat transport amount in the internal space S improves. Furthermore, in the internal space S of the vapor chamber1, it is possible to suppress a state in which the liquid-phase working fluid is not present in the evaporation part, i.e. dry-out, the flow of circulation of the liquid-phase working fluid and the gas-phase working fluid become favorable, and the heat transport improves. Based on such a fact, the vapor chamber1can have superior heat transport characteristic.

Furthermore, the gap flow channel part14easily takes in the liquid-phase working fluid inside and hardly leaks the liquid-phase working fluid taken inside to outside of the gap flow channel part14by the capillary phenomenon. For example, even if the vapor chamber1is in any posture, such as a state in which the vapor chamber1shown inFIG.1inclines 90 degrees within the paper plane, or a state up-side down, the liquid-phase working fluid easily enters the gap flow channel part14, and the liquid-phase working fluid hardly leaks to outside from the gap flow channel part14. In this way, the heat transport characteristic of the vapor chamber1is superior, due to the flow of circulation of the liquid-phase working fluid and the gas-phase working fluid being favorable, independently of the arrangement state of the vapor chamber1.

Furthermore, the vapor chamber1locally includes the annealed part50produced by heating when forming the top face joining part13a,at a portion adjacent to the top face joining part13a,rather than the entirety of the vapor chamber1. The annealed part50made by heat treatment causes the mechanical strength of the material to decline. The conventional vapor chamber does not locally provide an annealed part to a portion adjacent to the top face joining part13aof the vapor chamber1, but rather provides an annealed part over a wide area of the first metal sheet or the second metal sheet. In this way, compared to conventionally, in the vapor chamber1, the region of the annealed part50is small, and it is possible to suppress a decline in mechanical strength by annealing. For this reason, the vapor chamber1can have superior mechanical strength.

In addition, the gap flow channel part14preferably has a gap length14xfrom the sealed part14ato the opening part14blonger than the gap width14wbetween the top face abutting part13band the inner surface abutting part21. For the gap flow channel part14, if the gap length14xis longer than the gap width14w,the retention amount of the liquid-phase working fluid in the gap flow channel part14increases, and the capillary phenomenon of the gap flow channel part14improves. For this reason, the heat transport characteristic of the vapor chamber1further improves.

From the viewpoint of improving the heat transport characteristic of the vapor chamber1, the ratio (14x/14w) of the gap length14xrelative to the gap width14wis preferably 1.0 or more and 30.0 or less, and more preferably 2.0 or more and 10.0 or less.

In addition, the average value for the gap width14wof the gap flow channel part14is preferably 1.0 μm or more and 100.0 μm or less, more preferably 3.0 μm or more and 50.0 μm or less, and even more preferably 5.0 μm or more and 20.0 μm or less. When the average value of the gap width14wis 1.0 μm or more, it is possible to easily form the gap flow channel part14. When the average value of the gap width14wis 100.0 μm or less, since the capillary phenomenon of the gap flow channel part14improves, the heat transport characteristic of the vapor chamber1further improves.

In addition, the average value for the gap length14xof the gap flow channel part14is preferably 40.0 μm or more, more preferably 80.0 μm or more, and even more preferably 150.0 μm or more. In addition, the average value of the gap length14xis preferably 1.0 mm or less, more preferably 500.0 μm or less, and even more preferably 200.0 μm or less. When the average value of the gap length14xis 40.0 μm or more, since the retention amount of the liquid-phase working fluid in the gap flow channel part14increases, and the capillary phenomenon of the gap flow channel part14improves, the heat transport characteristic of the vapor chamber1further improves. When the average value of the gap length14xis 1.0 mm or less, it is possible to easily form the gap flow channel part14.

In addition, it is preferable that, as shown inFIG.2, the gap flow channel part14includes a gap enlarged part15at a sealed part14aside, and the average value of the gap width15wbetween the top face abutting part13band the inner surface abutting part21at the gap enlarged part15is larger than the average value of the gap width14wbetween the top face abutting part13band the inner surface abutting part21at the gap flow channel part14other than the gap enlarged part15. When the average value for the gap width15wof the gap enlarged part15is longer than the average value of the gap width14wbetween the top face abutting part13band the inner surface abutting part21at the gap flow channel part14other than the gap enlarged part15, the retention amount of the liquid-phase working fluid in the gap flow channel part14and the gap enlarged part15increases, and the capillary phenomenon of the gap flow channel part14improves. For this reason, the heat transport characteristic of the vapor chamber1further improves.

From the viewpoint of improving the heat transport characteristic of the vapor chamber1, the ratio (15w/14w) of the gap width15wrelative to the gap width14wis preferably 1.1 or more and 2.0 or less. When the ratio (15w/14w) is 1.1 or more, the heat transport characteristic of the vapor chamber1improves. When the ratio (15w/14w) is 2.0 or less, it is possible to easily form the gap enlarged part15.

In addition, from the viewpoint of improving the heat transport characteristic of the vapor chamber1, the gap enlarged part15is preferably provided at the closest portion of the top face abutting part13bto the top face joining part13aas shown inFIG.2, i.e. at the sealed part14a.Similarly, from the viewpoint of improving the heat transport characteristic of the vapor chamber1, the shape of the gap enlarged part15is preferably spheroidal, as shown inFIG.2.

In addition, as shown inFIG.1, the projecting part12preferably extends along the longitudinal direction L1of the vapor chamber1. When the projecting part12extends along the longitudinal direction L1of the vapor chamber1, the distance from the evaporation part41toward the condensation part42becomes longer, and the recirculation amount of the working fluid increases. For this reason, the heat transport characteristic of the vapor chamber1further improves.

In addition, the vapor chamber1preferably includes a plurality of top face joining parts13aat one of the projecting parts12. When a plurality of the top face joining parts13ais provided to one projecting part12, the bonding strength of the first metal sheet10and the second metal sheet20improves. When a plurality of the top face joining parts13ais provided to each projecting part12, the bonding strength of the first metal sheet10and the second metal sheet20further improves.

FIG.3is an enlarged cross-sectional view showing another example of the second metal sheet20constituting the vapor chamber1. It is preferable that, as shown inFIG.3, the second metal sheet20includes at least one projecting part22at the inner surface20a,and the projecting part22of the second metal sheet20projects from the inner surface20aof the second metal sheet20toward the first metal sheet10, and the top face23of the projecting part22abuts the recessed channel11of the first metal sheet10.

The top face23of the projecting part22of the second metal sheet20abuts the recessed channel11, i.e. the inner surface10aof the first metal sheet10. For this reason, the mechanical strength relative to the thickness direction of the vapor chamber1further improves. In addition, the gap due to abutting is provided between the top face23of the projecting part22and the inner surface10aof the first metal sheet10. Since this gap also exhibits the capillary phenomenon relative to the liquid-phase working fluid similarly to the gap flow channel part14, the liquid-phase working fluid is easily taken in this gap. For this reason, the heat transport characteristic of the vapor chamber1further improves.

In addition, the inner surface10aof the first metal sheet10and the inner surface20aof the second metal sheet20preferably have a roughened structure or a groove structure. The roughened structure is formed by roughening treatment on the inner surface10aor the inner surface20a.When the inner surface10aor the inner surface20ahas a roughened structure or a groove structure, the liquid-phase working fluid tends to flow along these structures, and the circulation of the liquid-phase working fluid and the gas-phase working fluid become favorable. For this reason, the heat transport characteristic of the vapor chamber1further improves.

In the formation of the top face joining part13aand the gap flow channel part14improving the heat transport characteristic of such a vapor chamber1, as well as local formation of the annealed part50, a process using a laser is preferable, and thereamong, a process using a fiber laser is more preferable. In a process by laser, it is possible to suppress formation enlargement of the annealed part50, and to form the top face joining part13aand the gap flow channel part14into a desired shape in a short time. As a result thereof, the annealed part50is not formed over a wide area of the vapor chamber1, but is rather formed locally. On the other hand, in the joining of the first metal sheet and the second metal sheet by using of diffusion bonding adopted in a conventional vapor chamber, the processability is very low compared to laser processing, such as the formation of the top face joining part13aand the gap flow channel part14, particularly the formation of the gap flow channel part14, being difficult, and the annealed part being formed over the entirety of the vapor chamber.

In addition, the material constituting the first metal sheet10and the second metal sheet20is preferably copper, copper alloy, aluminum, aluminum alloy or stainless steel, from the viewpoint of high thermal conductivity, processing ease by laser, etc. Thereamong, for the purpose of achieving weight reduction, aluminum or aluminum alloy is more preferable, and for the purpose of raising the mechanical strength, stainless steel is more preferable. In addition, depending on the use environment, tin, tin alloy, titanium, titanium alloy, nickel, nickel alloy, etc. may be used in the first metal sheet10and the second metal sheet20.

The heat generating body30mounted to the vapor chamber1is a member such as an electronic component which generates heat during operation, such as a semiconductor element, for example.

Next, a manufacturing method of the above-mentioned vapor chamber1will be explained.

The manufacturing method of the vapor chamber1has a laser bonding step of forming the top face joining part13aby laser. The laser bonding step preferably forms the top face joining part13awhich joins the first metal sheet10and the second metal sheet20by a fiber laser. In the laser processing, the top face joining part13atends to be process controlled to the desired shape, and the top face joining part13acan be formed in a short time. Furthermore, in the laser processing, since the portion desired to be joined can be heated locally, the annealed part50produced by heating is not formed over a wide area of the vapor chamber1, but rather is locally formed at a portion adjacent to the top face joining part13a.Among lasers, the fiber laser is more superior in processing control and short-time processing. When the top face joining part13ais formed, the gap flow channel part14is also formed as a result. Since the step of independently mounting a capillary structure (wick structure) such as conventionally is unnecessary, it is possible to achieve a reduction in production cost and production time, and simplification in production.

More specifically, in a state in which the inner surface10aof the first metal sheet10including the recessed channel11and the projecting part12, and the inner surface20aof the second metal sheet20are opposing each other, and the top face13of the projecting part12of the first metal sheet10is abutting the inner surface20aof the metal sheet20, the laser is irradiated to part of the top face13. For example, the laser may be irradiated from the first metal sheet10side to the part of the top face13, the laser may be irradiated from the second metal sheet20side to the part of the top face13, or the irradiation of these lasers may be combined.

On the other hand, in the joining by diffusion bonding which is adopted in a conventional vapor chamber or the like, the first metal sheet and the second metal sheet are entirely heat treated. In such heat treatment, since the entire surface of the top face13of the projecting part12is joined to the inner surface of the second metal sheet20, formation itself of the top face joining part13aand the gap flow channel part14is difficult. For this reason, in addition to the step of joining the first metal sheet and the second metal sheet, it is necessary to separately perform a step of installing a capillary structure. Furthermore, since the first metal sheet and the second metal sheet are entirely annealed by being heat treated, the mechanical strength of the vapor chamber declines.

In addition, the manufacturing method of the vapor chamber1preferably further has a laser welding step of welding the outer edge10cof the first metal sheet10and the outer edge20cof the second metal sheet20by laser, before or after the laser processing step. By welding the outer edge10cof the first metal sheet10and the outer edge20cof the second metal sheet20by laser, a welded part51is formed, and it is possible to easily manufacture the vapor chamber1including the internal space S inside. If the laser used in the laser bonding step and the laser used in the laser welding step are the same, it is possible to easily manufacture the vapor chamber in even shorter time.

More specifically, the laser is irradiated to the first metal sheet10and the second metal sheet20in a state in which the inner surface10aof the first metal sheet10and the inner surface20aof the second metal sheet20are opposing each other and the outer edge10cof the first metal sheet10and the outer edge20cof the metal sheet20are contacting. For example, the laser may be irradiated to a contacting portion of the outer edge10cand the outer edge20cfrom the first metal sheet10side, the laser may be irradiated to a contacting portion of the outer edge10cand the outer edge20cfrom the second metal sheet20side, the laser may be irradiated to a contacting portion of the outer edge10cand the outer edge20cfrom an in-plane direction of the vapor chamber1, or the irradiation of these lasers may be combined.

The vapor chamber1manufactured in this way is suitably used in electronic devices such as portable telephones, for which good heat transport characteristics are required even in various postures. The electronic device equipped with the vapor chamber1has high heat transport characteristics of the vapor chamber1, even in various usage states.

According to the above explained embodiment, since the liquid-phase working fluid easily infiltrates and flows in the gap flow channel part, the flow of circulation of the liquid-phase working fluid and the gas-phase working fluid improves, and the heat transfer within the internal space of the vapor chamber increases. For this reason, the vapor chamber can have superior heat transfer characteristics. In addition, in the vapor chamber, the annealed part is not provided over a wide area of the entire body, but rather is locally provided. For this reason, it is possible to suppress a decline in mechanical strength of the vapor chamber due to the annealed part.

It should be noted that, although the above description illustrates an example mounting the heat generating body30to the outer surface20bof the second metal sheet20as shown inFIG.1, the heat generating body30may be mounted to the outer surface10bof the first metal sheet10.

In addition, it is preferable to install the vapor chamber1so that the second metal sheet20is arranged on the side of the gravity direction, i.e. so that the second metal sheet20is arranged downward and the first metal sheet10is arranged upward along the gravity direction. When the vapor chamber1is installed so as to arrange the second metal sheet20on the gravity direction side, within the internal space S, the gap flow channel part14is arranged on the side of the gravity direction. The liquid-phase working fluid tends to enter the gap flow channel part14by gravity, in addition to the capillary phenomenon of the gap flow channel part14. As a result thereof, the heat transport characteristic of the vapor chamber further improves. In such an installation state of the vapor chamber, when mounting the heat generating body30on the outer surface20bof the second metal sheet20, i.e. lower part of the vapor chamber1, it is possible to efficiently cool the heat generating body30.

In addition, although the above description illustrates an example in which the projecting part12is a square column as shown inFIG.1, the shape of the projecting part12is sufficient so long as the top face13can abut the inner surface20aof the second metal sheet20. For example, the shape of the projecting part12may be a circular column as shown inFIG.4. In addition, in the case of the first metal sheet10including a plurality of the projecting parts12, the shapes of the projecting parts12may all be the same, or at least a part may differ.

Second Embodiment

FIG.5is a perspective view showing an example of a vapor chamber according to a second embodiment.FIG.6is an enlarged cross-sectional view of a plane B inFIG.5.

It should be noted that, in the embodiment shown below, the same reference numbers are assigned to constituent portions identical to the configuration of the vapor chamber of the first embodiment, and redundant explanations will be omitted or abbreviated.

A vapor chamber2according to the second embodiment is basically the same as the configuration of the vapor chamber1of the first embodiment, other than the configuration of the first metal sheet10differing. For this reason, this differing configuration is mainly explained herein.

As shown inFIGS.5and6, the first metal sheet10of the vapor chamber2has high uniformity in the sheet thickness, compared to the first metal sheet10of the vapor chamber1of the first embodiment. In the first metal sheet10of the vapor chamber1, the sheet thickness at the projecting part12is clearly larger than the sheet thickness at the recessed channel11, as shown inFIG.2.

As shown inFIG.6, in the vapor chamber2, the ratio (t2/t1) of the sheet thickness t2at the projecting part12of the first metal sheet10relative to the sheet thickness t1at the recessed channel11of the first metal sheet10is preferably 0.1 or more and 10.0 or less, more preferably 0.2 or more and 5.0 or less, even more preferably 0.5 or more and 2.0 or less, and most preferably 1.0, i.e. the sheet thickness t1at the recessed channel11and the sheet thickness t2at the projecting part12are equal. When the ratio (t2/t1) is within the above-mentioned range, since the variation in sheet thickness of the first metal sheet10is suppressed, it is possible to lighten the weight of the vapor chamber2. For the formation of the first metal sheet10having such a predetermined ratio (t2/t1), processing by press molding is favorable.

FIG.7is an enlarged cross-sectional view showing another example of the projecting part12constituting the vapor chamber2. As shown inFIG.7, the first metal sheet10may further have a convex part16which projects from part of the top face13toward the inner surface20aof the second metal sheet20. The top face of the convex part16provided to part of the top face13of the projecting part12joins to the inner surface20aof the second metal sheet20. In this case, part of the top face of the convex part16may join to the inner surface20aof the second metal sheet20, and the entire surface of the top face of the convex part16may join to the inner surface20aof the second metal sheet20. A process by press molding is suitable for the formation of the convex part16.

When the vapor chamber2includes the convex part16, since it is possible to easily control the shape of the gap flow channel part14, it is possible to easily take the liquid-phase working fluid into the gap flow channel part14. For this reason, the heat transport characteristic of the vapor chamber can be improved. In addition, compared to the abutting surface area between the top face joining part13aand the inner surface20aof the second metal sheet20in the vapor chamber not including the convex part16, it is possible to easily make the abutting surface area between the top face of the convex part16and the inner surface20aof the second metal sheet20smaller, and to make the annealed part50more locally. For this reason, it is possible to further suppress a decline in mechanical strength of the vapor chamber due to the annealed part.

Next, a manufacturing method of the above-mentioned vapor chamber2will be explained.

The manufacturing method of the vapor chamber2preferably further has a press processing step of forming the recessed channel11and the projecting part12of the first metal sheet10by press molding, prior to the above-mentioned laser bonding step and the laser welding step. By press molding the first metal sheet10, it is possible to easily form the recessed channel11and the projecting part12. In the press processing step, it is more preferable to also form the convex part16for the first metal sheet10, in addition to the recessed channel11and the projecting part12.

After the press processing step, by performing the laser welding step following the laser bonding step, or by performing the laser bonding step following the laser welding step, it is possible to manufacture the vapor chamber2.

According to the above explained embodiment, by making the variation in sheet thickness of the first metal sheet smaller, the vapor chamber can be reduced in weight. The recessed channel and the projecting part of such a first metal sheet can be easily formed in a short time by press molding. For this reason, the vapor chamber can be manufactured more simply.

Although an embodiment has been explained above, the present invention encompasses all aspects included in the gist of the present disclosure and the claims without being limited to the above-mentioned embodiment, and can be modified in various ways within the scope of the present disclosure.

EXPLANATION OF REFERENCE NUMERALS

10first metal sheet

10ainner surface of first metal sheet

10bouter surface of first metal sheet

10couter edge of first metal sheet

12alateral face of projecting part

13top face of projecting part

13atop face joining part

13btop face abutting part

14gap flow channel part

14asealed part of gap flow channel part

14bopening part of gap flow channel part

15gap enlarged part

20second metal sheet

20ainner surface of second metal sheet

20bouter surface of second metal sheet

20couter edge of second metal sheet

21inner surface abutting part

23top face of projecting part

30heat generating body

S internal space

F(L) flow of liquid-phase working fluid

F(G) flow of gas-phase working fluid