US20030121644A1

US20030121644A1 - Heat transport device

Info

Publication number: US20030121644A1
Application number: US10/258,499
Authority: US
Inventors: Minehiro Tonosaki; Koji Kitagawa; Hiroichi Ishikawa; Kazuhito Hori
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 2001-02-28
Filing date: 2002-02-28
Publication date: 2003-07-03
Also published as: JP3941537B2; JP2002349975A; WO2002068318A1

Abstract

A heat mass transport device, utilizing microchannels and micropumps, achieving a thinner form and offers a higher thermal conductance. The heat mass transport device (1) has a structure in which the microchannels for passing through a coolant and the micropumps for transporting the coolant form a single unit. For example, a channel layer (2), in which the microchannels (2 a) are formed, and a pump layer (4), in which the micropumps (4 a) are formed, may be laminated in a multi-layer structure, or a large number of single units in which a microchannel and a micropump are combined, may be placed in an array. Moreover, the heat mass transport device is made flexible, as the microchannels and micropumps are formed on a resin substrate utilizing flexible material.

Description

TECHNICAL FIELD

The present invention relates to a technology for reducing a thickness of a heat mass transport device that uses microchannels and micropumps.

BACKGROUND ART

Heat pipes, heat sinks, and radiators are widely used as heat releasing and cooling devices and basically heat exchange and cooling is performed by repetitive cycles of returning back flows of steam, fluid after heat release or the like.

By the way, technology commonly known as MEMS (micro electromechanical system) technology is receiving increased attention, as a result of recent advances in the electron device technology and micromachining technology, for taking advantage of the silicon process technology in order to develop devices having a better thermal conductance in a smaller form factor. For example, a device called microchannel is used as a cooling element for a localized, high-density source of heat, the cooling being performed by making a coolant fluid pass through each of a channel (path) upon forming a plurality of microscopic fins, which are tens of μm (microns) wide and approximately 100 μm deep, on a silicon substrate. Furthermore, a closed microchannel, that includes a forced oscillating plate for the fluid, achieves a nominal thermal-conductance performance that far exceeds copper.

However, conventional devices faces a constant limitation in terms of reducing thickness and compaction of heat releasing devices and cooling devices, and, as a result, when attached to sources of heat, these devices caused difficulty in making the device sizes smaller.

For example, a heat pipe that is 1 mm thick, 10 mm wide, and 50 mm long has a limited capacity of only several Watts per square centimeter and requires large areas for heat realizing or for thermal conductance, and cannot be used in very small scale devices.

Furthermore, some forms of a device having a pumping mechanism (for example, a micropump) is required for forcibly circulating a coolant in a device having a microchannel. When a circulation path for the coolant is set up for each (device) by installing a microchannel and a micropump independently, it would be difficult to reduce the size of the space taken up by the entire heat transporting system. This issue leads to a difficulty in achieving a higher heat transporting density.

In view of that, the present invention addresses the problem of achieving a smaller thickness and improving thermal conductance with a heat mass transport device that relies on microchannels and micropumps.

DISCLOSURE OF THE INVENTION

In order to address the issue described above, the present invention includes a single-unit structure that includes microscale channels for passing a coolant and microscale pumps for transporting the coolant. For example, a unit structure may combine a channel layer, that includes the microscale channels, and a pump layer, that includes the microscale pumps, that are laminated in a multi-layer structure; or the unit structure may combine a microscale channel and a microscale pump in a single-unit.

Therefore, according to the present invention, it is possible to make a device having smaller thickness by combining the microscale channels and microscale pumps into a single unit in a multi-layer structure or an arrangement of a single-unit structure. Furthermore, thermal conductance can be easily enhanced by increasing the number of microscale channels in the channel layer and microscale pumps in the pump layer in the multi-layer structure or by increasing the number of single-unit structures, each of which includes a microscale channel and a microscale pump.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an example of a structure of the heat transporting device of the present invention, with (A) showing a multi-layer structure, (B) showing a top view of each layer, and (C) showing a side view from a direction D. [0010]
FIG. 2(A) through FIG. 2(C) are diagrams showing a basic structure of a bubble-driven pump. [0011]
FIG. 3(A) through FIG. 3(F) are diagrams showing a method of forming microchannel and micropump flow paths. [0012]
FIG. 4(A) through FIG. 4(D) are diagrams showing a method of forming a piezo driven pump. [0013]
FIG. 5(A) through FIG. 5(B) are simplified drawings of a micropump array. [0014]
FIG. 6 is a simplified drawing of an example of structure of a heat mass transport device, including a side view and the shape of each portion. [0015]
FIG. 7 is a diagram showing an example of a structure of a heat mass transport device constituted by repetitive arrangement of a unitary structure. [0016]
FIG. 8 is a diagram showing an example of application of a heat mass transport device of the present invention. [0017]
FIG. 9 is a diagram showing another example of application of the heat mass transport device of the present invention. [0018]
FIG. 10 is a diagram showing an example of application of a micropump array. [0019]
FIG. 11 is a conceptual drawing showing a structure having a microchannel formed in closed loop. [0020]
FIG. 12, along with FIG. 13 and FIG. 14, shows an example of a closed-loop structure and FIG. 12 shows a simplified view from the top. [0021]
FIG. 13 shows enlarged views of portions of a microchannel and a micropump in a heat mass transport device. [0022]
FIG. 14 is a diagram showing a key portion of a micropump. [0023]
FIG. 15 is a perspective view showing an example of an embodiment of the present invention in which each of a plurality of heat sources has a heat mass transport device, which are connected to each other.[0024]

BEST MODES FOR CARRYING OUT THE INVENTION

The present invention relates to a thin heat mass transport device that relies on microscale channels (microchannels) for passing through a coolant and microscale pumps (micropumps) for transporting the coolant and may be widely used for device cooling and heat exchange. [0025]
In addition, the heat mass transport device of the present invention has the microscale channel and the microscale pump combined into a single unit in following forms: [0026]
1. A form in which a channel layer and a pump layer are laminated, and the laminated layers may be formed into a multi-layer structure; [0027]
2. A channel and a pump are formed into a single unit to form a unit structure, and a plurality of unit structures is placed next to each other. [0028]
First, FIG. 1 shows an example of the [0029] form 1. This example has a structure in which a channel layer, on which the microchannels are formed, and a pump layer, on which the micropumps are formed, are superposed. This structure is used as a heat mass transport device 1 (for example, a cooling or heat removal device) for a heat source HG. FIG. 1(A) shows its side view.
The heat [0030] mass transport device 1 has a multi-layer structure that includes a microchannel layer 2, a microvia and throughhole layer 3, and a micropump layer 4, and the layers are attached by fusion bond or the like.
FIG. 1(B) shows top views of each layer. In addition, FIG. 1(C) shows a side view of the heat [0031] mass transport device 1 seen from the direction of arrow D. Out of the three layers, the microchannel layer 2 is in direct contact with the heat source HG, and a plurality of microchannels 2 a, 2 a, . . . are formed in parallel to each other. Heat is transmitted from the heat source HG to each channel, as a coolant (for example but not limited to freon materials like FC72 or FC75, or water, air, or ethanol) flows through each channel.
The microvia and [0032] throughhole layer 3 is formed over the microchannel layer 2 and includes throughholes 3 a, 3 a, . . . , shown with black circles, and via holes 3 b, 3 b, . . . , shown with white circles, which are formed in a substrate made of a heat-insulating material. It should be noted that the throughholes 3 a are formed towards both ends in a longer direction of the heat mass transport device 1 (or along the directions of formation of the microchannels), thereby connecting the flow paths of the microchannels and the micropumps. In addition, each of the via holes 3 b is used for supplying heat required for driving a micropump, and a material having preferable thermal conductance, such as copper, is embedded in the holes.
A plurality of [0033] micropumps 4 a, 4 a, . . . is formed in the micropump layer 4. In the present example, a bubble-driven thermal pump (micropumps that are driven solely by thermal effect) is used as each micropump.
FIG. 2A through FIG. 2C are descriptive diagrams of its basic structure and the [0034] micropump 4 a is formed with a structure having a constricted portion in its flow path.
In addition, [0035] heater 5 is placed before a flow outlet in FIG. 2A and, as shown in FIG. 2B, bubble 6 is generated upon application of heat by such heater. By making use of a pumping effect resulting from vibration of this bubble, fluid is pumped out as shown in FIG. 2C.
It is well known that a maximum pressure generated in such a micropump can be well described by the Laplace Equation determined by surface tension, as well as the maximum radius and the minimum radius of the flow path. There is however a problem in which, if a heater is used as shown in FIG. 2A through FIG. 2C, an external power supply is needed, thus efficiency is affected. In view of this, it is desirable to make use of heat from the heat source HG, instead of such a heater, as shown in FIG. 1. In the present example, heat is transmitted directly from the [0036] microchannels 2 a to the micropumps 4 a through the via holes 3 b.
Therefore, in the present example, the coolant circulates between the [0037] microchannel layer 2 and the micropump layer 4 and the throughholes 3 a between the two layers, and, as a result, a cooling system is formed, in which heat is transported by the coolant from the heat source HG through the various microchannels.
An example of a method of forming the microchannel layer and the micropump layer are shown in FIG. 3A through FIG. 3F. A [0038] substrate 7, made of a plastic material, is prepared (FIG. 3A), and stop layers 8, 8 (or surface modifying layers) are formed on both sides thereof by an ion implanting method (PBII treatment), as shown in FIG. 3B. Then, mask patterning is performed as shown in FIG. 3C. A photoresist resin, metal, ceramic material or the like may be used as a mask MP. After a subsequent formation of an opening 9 is performed by dry etching method such as O₂(oxygen) beam etching, a portion of the substrate is removed through this opening by a chemical etching method using, for example, limonene (d-C₁₀H₁₆), as shown in FIG. 3E. In other words, a path 10 for a channel or pump flow path is formed, as shown in FIG. 3F, by dissolution with immersion in an etching solvent bath.
In addition, flexible microchannels and micropumps can be formed by using a flexible material (for example, a resin material used for polymer films, flexible substrates an the like) as substrates for the channel layer and the pump layer. In other words, the various devices may be formed on film layers. As a result, it would be possible to bend the heat mass transport device or have the heat mass transport device conform to a prescribed contour in a wide range of applications. This is especially effective in devices with limited space for their arrangement as a result of downsizing or thinner shape. [0039]
Although a structure relying on bubble-driven pumps is presented in the above-mentioned example, there is no limitation thereto, thus apiezoelectric driven pump (or piezo-driven) micropump may also be used. [0040]
FIG. 4A through FIG. 4D show an example of an overview of a method of forming such a pump. [0041]
Firstly, as shown in FIG. 4A, ion implanted [0042] layers 12, 12 are formed on each of both sides of a substrate 11, and thin films 13, 13 are deposited on top thereof. Then, after an opening 14 is formed by ion beam etching, as shown in FIG. 4B, a tapered circular hole 15 (or, more accurately, a truncated-cone-shaped hole with a bottom) is formed by limonene etching, as shown in FIG. 4C. FIG. 4C shows the circular hole 15 viewed from bottom. Next, as shown in FIG. 4D, a piezoelectric body 16 (or a piezoelectric thin film) is fixed (or formed) in the circular hole 15, and a piezo-driven pump 18 a is formed by attaching driver electrodes 17, 17. The piezo-driven pump 18 a may be able to pump the coolant by driving the piezoelectric body 16 with external signals so as to make the thin film 13 vibrate. In other words, the coolant is pumped out along a path facing the pump.
FIG. 5A through FIG. 5B show a [0043] micropump array 18 having a plurality of piezo-driven pumps 18 a, 18 a, . . . on a substrate. FIG. 5A shows a view from the holes for the piezoelectric bodies, while FIG. 5B shows a side view. It is to be noted that reference numerals 19, 19 . . . here refer to the respective coolant paths.
FIG. 6 shows an example of a structure of the heat [0044] mass transport device 20 using the micropump array 18 described above.
The [0045] microchannel layer 2 is attached to the heat source HG, and a microvia layer 21 (a layer in which only via holes 21 a, 21 a, . . . are formed) is provided on top of the channel layer. In addition, flat plate fluid pipes 22 and 23, using, for example, flexible substrates, are placed. It is to be noted that, although the various layers are not shown to be laminated in FIG. 6 for the sake of illustration, an actual configuration comprises a structure having laminated a layer including the microchannel layer 2 and the flat plate fluid pipe 23 and a layer including the micropump layer 24 and the flat plate fluid pipe 22, thus configuring a thin-type heat mass transport device 20. These flat plate fluid pipes are flow paths for the coolant (FC75 or the like) and also function as heat releasing portions.
The [0046] pump layer 24, which includes the above-mentioned micropump array 18, has a function of drawing in the coolant from the flat plate fluid pipe 22 and sending the coolant out against the flat plate fluid pipe 23.
In the present configuration, a forced circulation system for the coolant is formed by placing the [0047] micropump layer 24 in the coolant path utilizing the microchannel layer 2 and the flat plate fluid pipes 22 and 23, so that heat from the heat source HG is transmitted through the microchannel layer 2 into the flat plate fluid pipes and released by the flat plate fluid pipes as well as the microvia layer 21.
In addition, although in the description above, only a basic example, combining each one of the microchannel layer and the micropump layer, has been described, a device having a multi-layer structure can easily be formed by laminating a plurality of layers. [0048]
Next, a structure for the [0049] form 2 mentioned above will be described.
In the present form, there is a unit (unit) structure in which a microchannel and a micropump are combined into one body, so that a it is possible to obtain a so-called multi-structure or expandability by arranging such structures in parallel or ordered in a regular fashion. [0050]
FIG. 7 shows a heat [0051] mass transport device 25 having such configuration having a unit structure in which a micropump 27 is placed over a microchannel 26 (simplified into a long narrow rectangular parallelepiped in the drawing). It is to be noted that, because the present example utilizes bubble-driven micropumps, a via hole 28 is provided between such pump and the microchannel 26 for supplying heat to the micropump. Such a portion is not necessary if piezo-driven micropumps as described above are used instead. Conversely, a wiring substrate (for example, a flexible substrate) would be necessary between the piezoelectric driver electrodes.
It is to be noted that, one of the heat transport units, which includes the [0052] microchannel 26 and the micropump 27, is shown to be shifted upward in FIG. 7 in order to schematically illustrate with arrows the flow of the coolant through such unit. Upon arranging the heat transport units having such structure in parallel to each other, it is possible to make attempts at realizing a multi-unit heat transport path.
In addition, for the sake of representation on the drawing, although a substrate material for the heat transport unit is omitted, each channel, pump and the like may be formed on a flexible substrate utuilizing a flexible material. [0053]
Although FIG. 7 showing a combined configuration in which a microchannel and a micropump are laminated, there is no limitation thereto, so that it is possible to adopt a unit structure in which a single or a plurality of micropumps are formed at a portion of the coolant path formed by a microchannel. For example, the pump portion and the channel portion may form a flow path for the coolant on a single plane surface by forming a loop on a thin and flat substrate (flexible substrate). Such a structure will be described later in detail. [0054]
Furthermore, although the [0055] present form 2 and the above-mentioned form 1 may be used independently, the two forms may be combined to accommodate a wider range of forms, according to the application.
FIG. 8 shows an example of application of the heat mass transport device of the present invention, in which a heat [0056] mass transport device 29 in film sheet form is arranged spread over an exothermic body 30 and a heat realizing plate 31. As shown through an enlarged cross-section structure thereof within the large circular frame in the figure, the heat mass transport device 29 in this case has a multi-layer structure in which the microchannel layers 2 and the micropump layers 4 or layers that include the micropump layers 4 as well as the via hole and throughhole layers are interlaminated and, because a flexible material (e.g., a polymer material) is used as a substrate for each layer, it is user-friendly in terms of flexibility and there is also an advantage of having an ability to withstand deformation under a bending stress. At this event, because the thickness of each layer is of magnitude of tens of μm to 100 μm, a total film thickness of the multi-layer structure does not become significantly large. For example, as the total thickness may be kept within 1 mm or less, it is possible to achieve a thin enough embodiment.
In addition, FIG. 9 shows another example of application in which an [0057] exothermic body 33 and a radiator 34 are attached separately onto a heat mass transport device 32 in film sheet form including a microchannel layer and a micropump layer. In addition, even in this case, as a material of considerable flexibility is used as a substrate for each layer, it is possible to easily cope with bending and the like, in the flow paths for the coolant. For example, in a portable computer apparatus or the like having two chassis coupled by using hinges, the heat mass transport device 32 may be placed against an exothermic body, such as a CPU (central processing unit), while the radiator 34 may be placed in another chassis separated from the exothermic body, thus the present heat mass transport device makes it possible to realize a heat releasing structure and a cooling structure that thermally connects the exothermic body with the radiator.
It is to be noted that the heat mass transport device is especially effective in removing heat from or cooling an exothermic body having a high thermal density and, in addition to a multi-layer structure utilizing the laminated structure of [0058] form 1 or a multi-unit structure utilizing a unit structure of form 2 that have been described earlier, other structures, are possible in which, for example, as shown in FIG. 10, flexible pumps 35, 35, . . . , which are film-shaped micropump layers (although the example shows the micropump array 18 having piezo-driven micropumps, bubble-driven pumps may also be used), may be placed on the radiator 34 to enhance heat spreading efficiency, thus a wide range of applications are expected as it is possible to conceptualize embodiments resulting from combination of each type. Although being it difficult to describe all possible applications, for example, a heat releasing device to be used in conjunction with a high temperature exothermic motor, or in a device for cooling a removable cartridge disk (whose temperature rises during rotation) in a compact hard disk drive system.
Furthermore, embodiments are possible for the microchannels, which form the flow paths for the coolant, having an open structure or a closed structure. [0059]
FIG. 11 shows a conceptual drawing of closed loop configuration resulting from forming a microchannel in closed loop form (endless loop shape). [0060]
A closed [0061] loop 36 in the figure shows a circulation path for the microchannel, and a portion represented with a symbol ‘P’ within the path represents a micropump.
Although this micropump may be bubble-driven or piezo-driven, the former, which does not require a power supply, would be more desirable. In addition, in this case, the micropump may be formed by making a portion of the microchannel narrower by contriction. In other words, a circulation path may be formed with a microchannel and a micropump formed by making a portion of the microchannel narrower by constriction, in a closed loop, thus heat transport efficiency can be increased using a structure having a plurality of such flow paths disposed on a single plane. [0062]
Although the micropump P is placed near the heat source HG, represented by a square frame drawn with broken lines in the figure, when temperature distribution is not uniform in this heat source HG, and the temperature is locally higher at, for example, a point “Hs,” the coolant would flow from the pump toward the point “Hs” (in a direction shown by an arrow Y), if the pump is a bubble-driven micropump. As a result, the coolant circulates through the path by being cooled by a means of heat spreading or a means of cooling by, for example, a heat spreading plate placed away from the heat source HG, and returning back to the micropump. [0063]
It is to be noted that water or ethanol is a preferred coolant for filling the flow paths, considering user-friendliness and safety and, for example, the coolant would be heated and vaporized near the pump, which is a narrow portion of the microchannel, return back into the fluid phase by subsequent cooling, and circulate back to the heat source in repeating cycles. [0064]
In addition, although heat is applied on the narrow portion of the channel of the bubble-driven pump at a position slightly dislocated from its central position, as shown in FIG. 2A through FIG. 2C, it is also known that a similar pumping effect could be obtained by heating a portion of the channel away from the narrow portion. Therefore, another structure is possible in which a portion of the channel having a constant diameter, and not necessarily the narrow portion of the channel, would be heated. In such case, the flow of the coolant would be determined by the relative positions of the portion that is narrow and the portion that is heated and the coolant flows from the portion that is narrow to the portion that is heated. [0065]
It should be noted that while the micropump is placed at a single location in the circulation path in FIG. 11, a structure having a plurality of pumps is also possible. [0066]
FIG. 12 through FIG. 14 show examples of closed loop structures as described above. [0067]
In FIG. 12, an [0068] exothermic body 37, such as a CPU, is placed on a substrate, and a film-shaped heat mass transport device 38 is pasted on this exothermic body.
The heat [0069] mass transport device 38 has a plurality of closed loop microchannels, which do not intersect with each other, formed thereon by forming microscale grooves on a substrate material utilizing a flexible material like a polymer material. In addition, it has a configuration in which a side of this substrate on which the grooves are formed is coated with a cover material (film material). In FIG. 12 and FIG. 13, a group of closed curves 39 represent circulation paths laid out like tracks for the coolant (e.g., water).
In FIG. 12, a portion of the heat [0070] mass transport device 38 is in contact with a high temperature section 37 a of the exothermic body 37, and a micropump is formed on each circulation path in an area inside a frame 40, shown with dotted lines. Also, although not shown in this figure, heat spreading plate(s), heat removal plate(s), and heat conducting plate(s) are placed on the right hand side of a vertical line T in this figure and a portion of the heat mass transport device (right hand portion) is in contact therewith.
FIG. 13 and FIG. 14 show outlines of cross-sectional structures of the heat mass transport device. [0071]
Each of the circulation paths, represented by a group of [0072] closed curves 39, is made of a microchannel 41, formed as a groove having a prescribed depth and a constant width, and a micropump 42, formed as a narrower portion (a portion with a smaller width or a shallower depth) in this channel.
FIG. 13 shows enlarged views of the microchannel and the micropump, which are schematically shown as made of a transparent material. In addition, FIG. 14 shows only key portions of the micropump (grooves formed on the substrate). [0073]
For example, a [0074] pump 42 a is formed by making a portion of the channel narrower, and the channel is formed having a constant width except for this narrower portion.
It is to be noted that, although a groove in the substrate having a constant width (w) and a constant depth (d), except for the pump portion, is simple to manufacture, in some cases, it is possible to make a design so that the cross-sectional area of the groove may be different by continuously changing according to a position over the flow path or gradual change. [0075]
In addition, as mentioned above, because the coolant is moved toward the source of heat in the bubble-driven pump, the coolant moves in a counter-clockwise direction in FIG. 12, for example, if a hot spot exists on the left hand side of the pump portion, which is highlighted with a [0076] round frame 40. For example, a CPU or the like does not have a uniform temperature distribution across its surface, and there may be a localized spot with higher temperature. The pump portion (the narrow portion of the channel) should be deliberately positioned away from the spot with higher temperature. As a result, an additional heat source for facilitating a pumping effect would not need to be installed separately.
However, in the present example, the coolant, by repeating the cycle of being transported by the micropump upon been heated by the exothermic body, moving through the circulation path, being cooled by the radiator, and returning back to the pump, the coolant is able to efficiently transport heat from the exothermic body to the radiator. [0077]
Moreover, because the heat [0078] mass transport device 38 is formed into an extremely thin sheet, an even more efficient heat transfer is possible by superposing a plurality of sheets in many layers and also occupying a small disposing space.
Furthermore, because the circulation paths for the coolant can be formed with a relatively high degree of freedom by forming each microchannel and micropump in a closed-loop flow path, there is a high degree of freedom of design. In the example described above, although portions made of concentric semicircles each, are connected with a pair of straight paths to form flow paths that look like a “track field”, the present invention is not limited to such shape and can accommodate a flow path that crosses across a plurality of heat sources and also regardless of existence of branches. [0079]
FIG. 15 shows an example in which a flow path that connects a plurality of heat mass transport device, which are installed for each of a plurality of heat sources, and the heat mass transport device are connected with branching flow paths. [0080]
In the present example, each of the [0081] circuit substrate 43 and 44 has a plurality of ICs (integrated circuits) and among these ICs, those that generate high volumes of heat are to be considered exothermic bodies (heat sources). For example, among the ICs 43 a, 43 a, . . . on the substrate 43, a heat transport apparatus (device) 45 is installed on an IC 43 a 1, and a heat mass transport device 46 is attached to an IC 43 a 2.
Furthermore, out of the [0082] ICs 44 a, 44 a, . . . on the other substrate 44, a heat mass transport device 47 is installed on an IC 44 a 1, and a heat spreading portion (or a heat sink) 48 is also provided on the substrate 44.
The heat [0083] mass transport device 45 through 47 have a basic structure consisting of loop-shaped flow paths that includes planer channels and pump portions (bubble-driven) formed on the surface of their substrate. Therefore, a plurality of flow paths are formed on a same plane, and the pumps are driven by heat from the ICs, which are exothermic bodies.
For example, as shown in this figure, the Heat [0084] mass transport device 46 exchanges heat with the heat spreading section 48 through two flow sections 46A and 46A, which are made of a plurality of microchannels. In other words, a portion of the Heat mass transport device 46 is pasted on a surface of the IC 43 a 2, which is an exothermic portion, and the coolant (i.e., water), heated by the exothermic portion, passes through one of the flow paths 46A, releases heat at the heat spreading section 48, and then returns to the portion pasted to the surface of the IC 43 a 2.
Furthermore, some portions of the flow paths, connected to the [0085] heat spreading section 48, branch out and connect to the seat mass transport devices 45 and 47. In other words, out of the flow path sections 47A and 47B, which connect the heat mass transport device 47 and the heat spreading section 48, the flow path section 47A branches off in a T-shape in a middle and extends toward the substrate 43 and connects with the flow paths 45A, 45A, which extend from the heat mass transport device 45 toward the substrate 44. Therefore, heat exchange takes place between the various heat mass transport devices and the heat spreading section 48 through the microchannels formed in these flow path sections (in other words, the coolant, heated at portions of the substrate where the ICs are mounted, flows through the various flow path portions to arrive at the heat spreading portion, releases heat at the heat spreading portion, and then returns to portions of the substrate where the various ICs are mounted.)
In this way, a high degree of freedom is available in terms of the flow path layout and shapes, even in the presence of a plurality of exothermic portions. Furthermore, highly flexible heat mass transport devices, that can be bent easily, may be created by using a flexible resin material for the substrate, and thin and flat heat mass transport devices can be pasted onto the exothermic bodies. Moreover, it is also possible to use a configuration having a lamination of a plurality of sheet-shaped devices having a plurality of flow paths on a same plane. [0086]
As clearly demonstrated by the descriptions above, according to inventions in [0087] claims 1 through 3, as the overall arrangement space, area occupied by the heat mass transport device and the like can be reduced by combining microchannels and pumps into a single unit, it is possible to make device thinner. Furthermore, thermal conductance can be easily increased by increasing the number of channels and pumps if adopting a multi-layer structure like the invention in claim 2, or by increasing the number of unit structures including the channel and pump if adopting a combined structure like the invention in the scope of claim 3.
According to an invention in [0088] claim 4, the structure becomes simpler as a microscale pump is formed by making a portion of the microchannel path narrower.
According to an invention in [0089] claim 5, as it is possible to perform heat transport by circulating a coolant through closed-loop flow paths made of microchannel and microscale pump, heat-removal and cooling efficiency can be increased by disposing a large number of such closed loops.
According to inventions in [0090] claim 6 through 9, the user-friendliness of the heat mass transport device is enhanced significantly as a substrate is formed with flexible material, so that it is possible to make a device that is flexible with respect to a bending stress and could easily accommodate curved flow paths.

Claims

1. A heat mass transport device characterized by having a microchannel for passing through a coolant, and a micropump for passing through said coolant, wherein said microchannel and said micropump are formed into a single unit, and said coolant transports heat by circulating through said microchannel.

2. The heat mass transport device of claim 1, characterized by having a channel layer, in which said microchannel is formed, and a pump layer, in which said micropump is formed, wherein said heat mass transport device comprises a multi-layer structure in which said channel layer and said pump layer are laminated.

3. The heat mass transport device of claim 1, characterized by comprising a unit structure in which said microchannel and said micropump form a single unit, wherein said heat mass transport device includes a plurality of said single unit structures.

4. The heat mass transport device of claim 1, characterized by having said micropump formed by making a portion of said microchannel narrower by constriction.

5. The heat mass transport device of claim 4, characterized by having said microchannel and the said micropump formed in closed loop form.

6. The heat mass transport device of claim 1, characterized by having a constituting material for said microchannel and said micropump formed of a flexible material.

7. The heat transport device of claim 2, characterized by having a constituting material for said channel layer and said pump layer formed of a flexible material.

8. The heat mass transport device of claim 3, characterized by having a constituting material for said microchannel and said micropump formed of a flexible material.

9. The heat mass transport device of claim 4, characterized by having a constituting material for said microchannel and said micropump formed of a flexible material.