US20140138075A1

US20140138075A1 - Heat exchanger and semiconductor module

Info

Publication number: US20140138075A1
Application number: US13/853,073
Authority: US
Inventors: Shu-Jung Yang; Yu-Lin Chao; Chun-Kai Liu; Chi-Chuan Wang; Kun-Ying Liou
Original assignee: Industrial Technology Research Institute ITRI
Current assignee: Industrial Technology Research Institute ITRI
Priority date: 2012-11-19
Filing date: 2013-03-29
Publication date: 2014-05-22
Also published as: TW201421622A; TWI482244B

Abstract

A heat exchanger suitable for cooling a heat source is provided, wherein a bypass channel formed in the heat exchanger has a width greater than a width of other channels to reduce a flow resistance of a fluid and a pumping power for driving a system. That is, under the same pumping power loss, more fluid is driven to achieve a better heat dissipation effect. By applying the heat exchanger, electronic devices are bonded to a top of the heat exchanger through a supporting substrate. In this way, heat generated when the electronic devices are is transferred to the heat exchanger through the supporting substrate and dissipated to the outside via the heat exchanger. Since the distance of heat transfer is decreased, the thermal resistance generated by an interface between the devices is reduced to improve heat transfer efficiency and heat dissipation effect.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 101143144, filed on Nov. 19, 2012. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

TECHNICAL FIELD

The disclosure relates to a heat exchanger and a semiconductor module that uses the heat exchanger to achieve a good heat dissipation effect.

BACKGROUND

In recent years, the rapid progress of the fabricating techniques of integrated circuits (ICs) leads to great improvements in the functions of electronic devices. However, with the enhancement of the processing speed and performance of the electronic devices, the heat generated when the electronic devices are working also increases. If the waste heat cannot be effectively dissipated, an electronic device failure may occur, or the electronic devices may not achieve the best performance.
Power electronic devices, such as insulated gate bipolar transistors (IGBTs) are widely used in electric motor vehicles. The development of the electric motor vehicles focuses on reduction of weight, volume and power consumption. One of the key points to achieving the above goals is the operating performance of the IGBT power module. Since the IGBT power module is under environmental effects of high temperature, vibration, humidity and dust pollution and, in addition, is itself a high-voltage high-current module, whether the heat dissipation is good has always greatly influenced the operating performance thereof.
A conventional IGBT power module includes one or more IGBT chips, one or more diode chips, a control chip, a direct bond copper (DBC) substrate and a base plate, combined with a cooling module such as a heat sink. The heat generated when the IGBT chips and the diode chips are working is first transferred to the DBC substrate, is spread on the DBC substrate and then is transferred to the base plate. Thermal grease is adhered to a cooling module such as a heat sink, and in this way the base plate of the power module dissipates the heat to the outside through the heat sink. In other words, the heat sink, the IGBT power module, the thermal grease adhered to the heat sink and the base plate of the power module generate significant thermal resistance, which limit the heat dissipation performance of the IGBT power module.
On the other hand, because of the high heat-generating power of the IGBT power module, liquid cooling heat sinks are also known to be used in the heat dissipation design of the IGBT power module. However, in addition to the above-mentioned issue of thermal resistance, such design further requires the consumption of pumping power to drive the fluid in the liquid cooling heat sink, which increases energy consumption of the entire system.

SUMMARY

According to an embodiment of the disclosure, the heat exchanger includes a base plate, a cover plate, a plurality of first heat dissipation fins, a plurality of second heat dissipation fins and a fluid. The base plate has a supporting surface and a back side opposite to the supporting surface, wherein the supporting surface supports a heat source, such as an electronic device. The cover plate is disposed on the back side of the base plate, and the cover plate and the base plate form a chamber. The chamber has an inlet and an outlet located at the same side of the chamber. The first dissipation fins are intervally disposed between the base plate and the cover plate, forming a plurality of first channels and a bypass channel in the chamber. Each of the first channels and the bypass channel extend from the inlet to a mixed flow area in the chamber, and a width of the bypass channel is greater than a width of each of the first channels. A ratio of the width of the bypass channel to the width of the first channels is, for example, less than or equal to 9. The second dissipation fins are intervally disposed between the base plate and the cover plate, forming a plurality of second channels in the chamber. Each of the second channels extends from the mixed flow area to the outlet, and the width of the bypass channel is greater than a width of each of the second channels. The fluid flows into the chamber through the inlet, wherein a portion of the fluid passes through the first channels, another portion of the fluid passes through the bypass channel, and the portion of the fluid and the another portion of the fluid mix in the mixed flow area, enter the second channels, and leave the chamber through the outlet.
Several exemplary embodiments accompanied with figures are described in detail below to further describe the disclosure in details.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments and, together with the description, serve to explain the principles of the disclosure.

FIG. 1A illustrates a semiconductor module according to an embodiment of the disclosure.

FIG. 1B is a bottom view of a heat exchanger depicted in FIG. 1A.

FIG. 1C is a perspective view of a structure of FIG. 1B.

FIG. 1D is an enlarged view of an area A of FIG. 1B.

FIG. 1E is a perspective view of a heat exchanger according to another embodiment of the disclosure.

FIG. 2 illustrates a heat exchanger according to another embodiment of the disclosure.

FIG. 3 illustrates a heat exchanger according to still another embodiment of the disclosure.

FIG. 4 illustrates a semiconductor module according to another embodiment of the disclosure.

FIG. 5A illustrates a semiconductor module according to still another embodiment of the disclosure.

FIG. 5B is a bottom view of a heat exchanger depicted in FIG. 5A.

FIG. 5C is an enlarged view of an area B of FIG. 5B.

FIG. 6 illustrates a semiconductor module according to still another embodiment of the disclosure.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS

It should be first noted that the heat exchanger of the disclosure may be applied in various compatible semiconductor modules to dissipate heat generated by electronic devices in the semiconductor module. In the following, only an arrangement in which the heat exchanger of the disclosure is applied in an IGBT power module is described as an example, but the disclosure is not limited thereto.
According to a design of the heat exchanger of the disclosure, we may integrate a base plate of the IGBT power module with the heat exchanger (that is, the original base plate of the IGBT power module is omitted) and directly bond a supporting substrate that supports electronic devices to a top of the heat exchanger. In this way, heat generated when the electronic devices are working is transferred to the heat exchanger through the supporting substrate and dissipated via the heat exchanger. Since the base plate of the IGBT power module and the heat exchanger are integrated, and the original base plate of the IGBT power module is omitted, the number of interfaces between devices may be reduced, thereby reducing the thermal resistance generated by the interfaces between the devices, and heat dissipation efficiency is improved.
FIG. 1A illustrates a semiconductor module according to an embodiment of the disclosure. A semiconductor module 100 includes a heat exchanger 110, a supporting substrate 120 and electronic devices 132 and 134. The electronic devices 132 and 134 are, for example, a diode chip and an insulated gate bipolar transistor (IGBT) chip, respectively, and are respectively disposed on the supporting substrate 120. The supporting substrate 120 is a ceramic metal substrate such as a direct bond copper (DBC) substrate or a direct plated copper (DPC) substrate, i.e. a composite substrate that includes a ceramic core layer 122 and double-sided copper coating layers 124 and 126. A material of the ceramic core layer 122 is, for example, aluminum oxide (Al₂O₃), aluminum nitride (AlN) or aluminum silicon carbide (AlSiC). The electronic devices 132 and 134 are bonded to the copper coating layer 124 through a first solder layer 142, and the copper coating layer 124 may be patterned to be a surface circuit 124 a to provide connections to the electronic devices 132 and 134. The electronic devices 132 and 134 of the present embodiment are electrically connected to each other through a solder wire 192, and the electronic device 132 is electrically connected to the surface circuit 124 a formed by the copper coating layer 124 through a solder wire 194.
Herein, the number, types and connection ways of the electronic devices 132 and 134 are only used as examples. In other embodiments of the disclosure, the number of the electronic devices may be one or three or more, and the types of the electronic devices 132 and 134 are not limited to a diode chip or an IGBT chip. The electronic devices 132 and 134 may be connected to the outside through the supporting substrate 120 or other circuit devices or may be directly connected to the outside. In addition, the electronic devices 132 and 134 of the present embodiment share one supporting substrate 120, but in other embodiments, the electronic devices may be disposed on two independent supporting substrates or on intermediary substrates of other possible types.
The electronic devices 132 and 134 are disposed on a base plate 112 of the heat exchanger 110 through the supporting substrate 120. The supporting substrate 120 and the heat exchanger 110 are bonded to each other through, for example, a second solder layer 144.
The structure of the heat exchanger 110 is further described below.
FIG. 1B is a bottom view of the heat exchanger 110. In order to clearly show the inner structure of the heat exchanger 110, FIG. 1B omits a cover plate 114. FIG. 1C is a perspective view of the structure of FIG. 1B. FIG. 1D is an enlarged view of an area A of FIG. 1B.
Referring to FIGS. 1A to 1D, the base plate 112 of the heat exchanger 110 has a supporting surface 112 a and a back side 112 b opposite to the supporting surface 112 a, wherein the supporting substrate 120 is disposed on the supporting surface 112 a of the base plate 112. The cover plate 114 is disposed on the back side 112 b of the base plate 112 and is bonded to the base plate 112 to form a chamber 119. A plurality of first dissipation fins 116 and a plurality of second dissipation fins 118 are disposed between the base plate 112 and the cover plate 114 to form a plurality of channels between the base plate 112 and the cover plate 114. In addition, a housing 150 is disposed on the base plate 112 of the heat exchanger 110 to cover the electronic devices 132 and 134 and the supporting substrate 120. The surface circuit 124 a is connected to terminals 184 a and 184 b on a surface of the housing 150 through conductive wires 182 a and 182 b.
The chamber 119 formed by the cover plate 114 and the base plate 112 together has an inlet 119 a and an outlet 119 b. The present embodiment takes into consideration the design restriction that the inlet and the outlet allow entry and exit only at a single side when the system is assembled and thus disposes the inlet 119 a and the outlet 119 b at the same side adjacent to the chamber 119 and allow entry and exit at a side of the chamber 119.
In other embodiments of the disclosure, holes that serve as the inlet 119 a and the outlet 119 b may also be selectively formed on the cover plate 114 or the base plate 112. For example, FIG. 1E illustrates another structure in which the disclosure disposes the inlet 119 a and the outlet 119 b on the base plate 112.
Because of the design of the present embodiment in which the inlet 119 a and the outlet 119 b are located at the same side of the chamber 119, the first dissipation fins 116 and the second dissipation fins 118 from a plurality of U-shaped channels in the chamber 119. In detail, the first dissipation fins 116 are disposed between the base plate 112 and the cover plate 114 side by side to form in the chamber 119 a plurality of first channels 162 parallel to one another and a bypass channel 164. Each of the first channels 162 and the bypass channel 164 extend from the inlet 119 a to a mixed flow area 166 in the chamber 119, and a width W1 of the bypass channel 164 is greater than a width W2 of each of the first channels 162. Specifically, a ratio of the width W1 of the bypass channel 164 to the width W2 of the first channels 162 is, for example, less than or equal to 9, so as to achieve a good balance between heat dissipation and reduction of flow resistance.
In addition, in the present embodiment, in order for a fluid to be uniformly distributed in the channels, a height of the first dissipation fins 116 and the second dissipation fins 118 may be varied, and channels of different depths may be formed therebetween, so that the fluid has different flow resistances when entering the channels, and a more uniform flowing distribution of the fluid is achieved.
In the present embodiment, the inlet 119 a and the outlet 119 b are located at a first side S1 of the chamber 119, and the mixed flow area 166 is located at a second side S2 of the chamber 119. Each of the first dissipation fins 116 is L-shaped, for example, and each of the first dissipation fins 116 includes a first portion 116 a and a second portion 116 b. The first portion 116 a extends from the first side S1 to the second side S2 along a first direction D1, and the second portion 116 b is connected to the first portion 116 a and extends to the mixed flow area 166 along a second direction D2. The first direction D1 intersects the second direction D2; for example, the first direction D1 is perpendicular to the second direction D2. In addition, the location of the bypass channel 164 may be adjusted according to needs. For example, the present embodiment chooses to dispose the bypass channel 164 at an outermost side of the first channels 162 and adjacent to an inner wall of the chamber 119.
The second dissipation fins 118 are disposed between the base plate 112 and the cover plate 114 side by side to form a plurality of second channels 168 parallel to one another in the chamber 119. Each of the second channels 168 extends from the mixed flow area 166 to the outlet 119 b, and the width W1 of the bypass channel 164 is greater than a width W3 of each of the second channels 168.
In the present embodiment, each of the second dissipation fins 118 is L-shaped disposed in a mirror manner to the first dissipation fins 116, and each of the second dissipation fins 118 includes a third portion 118 a and a fourth portion 118 b. The third portion 118 a extends from the first side S1 to the second side S2 along the first direction D1, and the fourth portion 118 b is connected to the third portion 118 a and extends to the mixed flow area 166 along a third direction D3. The third direction D3 is opposite to the second direction D2.
A fluid 170 flows into the chamber 119 through the inlet 119 a, wherein a first portion of the fluid 172 passes through the first channels 162, a second portion of the fluid 174 passes through the bypass channel 164, and the first portion of the fluid 172 and the second portion of the fluid 174 mix in the mixed flow area 166, enter the second channels 168, and leave the chamber 119 through the outlet 119 b.
Based on the above, because the width W1 of the bypass channel 164 is greater than the width W2 of each of the first channels 162, a flow resistance experienced by the second portion of the fluid 174 flowing in the bypass channel 164 is lower than a flow resistance experienced by the first portion of the fluid 172 flowing in the first channels 162. In other words, pressure loss of the second portion of the fluid 174 in the bypass channel 164 is lower than pressure loss of the first portion of the fluid 172 in the first channels 162. The heat generated when the electronic devices 132 and 134 are working is transferred to the heat exchanger 110 through the supporting substrate 120, and the base plate 112, the cover plate 114, the first dissipation fins 116 and the second dissipation fins 118 may exchange heat with the fluid 170, so that the fluid 170 carries the heat away.
In addition, since the second portion of the fluid 174 in the bypass channel 164 has a lower pressure loss and a higher flowing speed, a temperature of the second portion of the fluid 174 passing through the bypass channel 164 is lower than a temperature of the first portion of the fluid 172 passing through the first channels 162. Besides, an inlet temperature when the first portion of the fluid 172 and the second portion of the fluid 174 mix in the mixed flow area 166 and enter the second channels 168 is lower than an inlet temperature of a structure without the design of the bypass channel 164. In this way, the fluid 170 may provide a better heat exchange effect in the second channels 168.
In other words, the bypass channel 164 of the present embodiment reduces pressure loss of the fluid 170 in the channels, effectively decreases a flow resistance that drives the fluid 170 to flow, and decreases a pumping power required to drive the system, or the bypass channel 164 of the present embodiment, compared with a conventional design, provides a greater fluid flow and heat transfer amount and achieves a better heat dissipation effect under the same pumping power consumption. In addition, the semiconductor module 100 of the present embodiment, when serving as an IGBT power module of an electric motor vehicle, lowers a power consumption of the electric motor vehicle and prolongs a traveling time and distance of the electric motor vehicle.
In the manufacturing process, the heat exchanger 110 may be manufactured by techniques such as machining, welding and sealing. First, machining such as computer numerical control (CNC) is used to manufacture the channels, the mixed flow area, and the dissipation fins on a metal plate. That is, the base plate 112, the first dissipation fins 116 and the second dissipation fins 118 are integrally formed. Furthermore, the cover plate 114 is manufactured by machining and then combined to the base plate 112 by ways of welding and sealing, for example, to form the heat exchanger 110. In the present embodiment, the chosen metal plate may be a copper plate or other metal materials with good heat conductivity. In addition, a composite material may replace the metal plate for the manufacture of the heat exchanger 110.
Multiple embodiments are described below to illustrate possible varied examples of the semiconductor module and the heat exchanger of the disclosure. The parts described in the previous embodiment are omitted, and the description focuses on major differences, and the same or similar reference numerals are adopted to represent similar elements.
FIG. 2 illustrates a heat exchanger according to another embodiment of the disclosure. FIG. 2 omits the cover plate to clearly show the inner structure of the heat exchanger.
As shown in FIG. 2, a heat exchanger 210 of the present embodiment is similar to the heat exchanger 110 shown in FIG. 1B, and the difference between the two mainly lies in that the present embodiment changes structures of second heat dissipation fins 218 to adjust a shape of a mixed flow area 266. To be more specific, the present embodiment omits the fourth portion 118 b (as shown in FIG. 1B) of the second heat dissipation fins 118 in the heat exchanger 110 of the previous embodiment, so that the mixed flow area 266 of the present embodiment is expanded by leaving unoccupied an area where the fourth portion 118 b is originally disposed. Each of the second heat dissipation fins 218 is in a linear shape and extends from the first side S1 to the mixed flow area 266 along the first direction D1.
Indeed, the shape, size and location of the mixed flow area 266 may be adjusted according to actual needs. In response to the design of the mixed flow area 266, structures of first dissipation fins 216 and the second dissipation fins 218 may be changed correspondingly.
In addition, the disclosure may choose to dispose an additional turbulence structure in the mixed flow area to improve a mixing effect of the fluid in the mixed flow area. A heat exchanger 310 of another embodiment of the disclosure as shown in FIG. 3 illustrates a design with a mixed flow means 367 additionally disposed in a mixed flow area 366. Herein, the mixed flow means 367 is a partition, for example, and the mixed flow means 367 is separated from first dissipation fins 316 and second dissipation fins 318 and lies in a flowing path of a fluid 370. Furthermore, the disclosure does not limit the number, shape, location and height of the mixed flow means 367. In other embodiments, the number, shape, location and height of the mixed flow means 367 may be changed to achieve an expected flow mixing effect.
FIG. 4 illustrates a semiconductor module according to another embodiment of the disclosure. As shown in FIG. 4, a semiconductor module 400 of the present embodiment is similar to the semiconductor module 100 shown in FIG. 1A, and the difference between the two mainly lies in that a base plate 412 of the present embodiment is a vapor chamber. That is, a chamber 412 a having a capillary structure 490 and a low vacuum level is formed inside the base plate 412, and when heat is transferred to the base plate 412 from a heat source, a liquid working substance in the chamber 412 a absorbs the heat and vaporizes in the environment with a low vacuum level. At this time, the working substance absorbs the heat and then it phase changes to form the vapor, and the vapor working substance quickly fills the whole chamber 412 a. When the vapor working substance is exposed to an area of a lower temperature, the vapor working substance condenses to release the heat absorbed in vaporization. The condensed liquid working substance returns to where evaporation has occurred through capillarity of the capillary structure. In this way, the above-described cycle is repeated so that the heat generated by the heat source is spread to each part of the base plate 412 rapidly. In other words, the base plate 412 of the present embodiment is a flat heat pipe structure having good two-phase flow characteristics and providing an excellent lateral heat conduction effect. Even if the base plate 412 carries a distributed heat source with a high working temperature, the base plate 412 is able to spread the heat generated by the heat source rapidly to prevent a hot spot from forming in a localized area and to extend life of the product.
FIG. 5A illustrates a semiconductor module according to still another embodiment of the disclosure. FIG. 5B is a bottom view of a heat exchanger of FIG. 5A. In order to clearly show the inner structure of the heat exchanger, FIG. 5B omits a cover plate. FIG. 5C is an enlarged view of an area B of FIG. 5B. As shown in FIGS. 5A to 5C, a semiconductor module 500 of the present embodiment is similar to the semiconductor module 100 shown in FIGS. 1A to 1D, and the difference between the two mainly lies in that the present embodiment disposes electronic devices 532 and 534 on a first supporting substrate 520 a and a second supporting substrate 520 b, respectively, and that the present embodiment chooses to form a plurality of cavities 502 on a surface of first dissipation fins 516, a surface of second dissipation fins 518 or in an inner wall of a chamber 519. To be more specific, the electronic devices 532 and 534 of the present embodiment are, for example, an IGBT chip and a diode chip, respectively, and may be connected to an external circuit in the ways introduced in the previous embodiments or in any known feasible way. The cavities 502 may be selectively formed on surfaces of a base plate 512, a cover plate 514, the first dissipation fins 516, or the second dissipation fins 518 by machining, for example, at the same time when a heat exchanger 510 is manufactured, and the cavities 502 are preferably located closer to the front of the place where a fluid 570 enters the dissipation fins In this way, the cavities 502 may change laminar flow characteristics of the fluid 570 in the chamber 519 because the cavities result in a sinking phenomenon in an original thermal boundary layer and in a boundary layer of a flow field when the fluid 570 flows through the cavities. Therefore, the thermal boundary and the boundary of the flow field are thinned. When the thermal boundary layer is thinned, the heat transfer effect is naturally improved (due to a lower thermal resistance). When the boundary layer of the flow field is thinner, a separation phenomenon is unlikely to occur, so that the resistance of the fluid 570 is reduced, and the heat dissipation ability of the fluid 570 is enhanced.
FIG. 6 illustrates a semiconductor module according to still another embodiment of the disclosure. As shown in FIG. 6, a semiconductor module 600 of the present embodiment is similar to the semiconductor module 500 shown in FIG. 5A, and the difference between the two mainly lies in that the present embodiment chooses to form cavities 602 on locations corresponding to heat sources (electronic devices 632 and 634) and make the cavities 602 penetrate through a base plate 612 to be connected to bottoms of the heat sources. To be more specific, the cavities 602 may penetrate through the base plate 612 and reach bottoms of supporting substrates 620 a and 620 b directly, so that a fluid cools the supporting substrates 620 a and 620 b under the electronic devices 632 and 634 directly to improve a heat dissipation effect. In addition, if the supporting substrates 620 a and 620 b are bonded to the base plate 612 through a solder layer 644, bubbles may be generated on a bonding surface. The bubbles may be discharged by the cavities 602 in the manufacturing process, and the reliability and heat dissipation ability between the supporting substrates 620 a and 620 b and the base plate 612 are enhanced. Indeed, the present embodiment may incorporate the design of the cavities 502 of the embodiment shown in FIGS. 5A to 5C. That is, the present embodiment may form cavities on surfaces of the base plate 612, the cover plate 614 and the dissipation fins 616 of the heat exchanger 610.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.

Claims

What is claimed is:

1. A heat exchanger, comprising:

a base plate having a supporting surface and a back side opposite to the supporting surface, wherein the supporting surface supports a heat source;

a cover plate disposed on the back side of the base plate, the cover plate and the base plate forming a chamber, wherein the chamber has an inlet and an outlet located at the same side of the chamber;

a plurality of first dissipation fins intervally disposed between the base plate and the cover plate forming a plurality of first channels and a bypass channel in the chamber, wherein each of the first channels and the bypass channel extend from the inlet to a mixed flow area in the chamber, and a width of the bypass channel is greater than a width of each of the first channels;

a plurality of second dissipation fins intervally disposed between the base plate and the cover plate forming a plurality of second channels in the chamber, wherein each of the second channels extends from the mixed flow area to the outlet, and the width of the bypass channel is greater than a width of each of the second channels; and

a fluid flowing into the chamber through the inlet, wherein a portion of the fluid passes through the first channels, another portion of the fluid passes through the bypass channel, and the portion of the fluid and the another portion of the fluid mix in the mixed flow area, enter the second channels, and leave the chamber through the outlet.

2. The heat exchanger according to claim 1, wherein a flow resistance of the fluid in the first channels is greater than a flow resistance of the another portion of the fluid in the bypass channel.

3. The heat exchanger according to claim 1, wherein the chamber has a first side and a second side opposite to each other, the inlet and the outlet are located at the first side, and the mixed flow area is located at the second side.

4. The heat exchanger according to claim 1, wherein each of the first dissipation fins is L-shaped, and each of the first dissipation fins comprises:

a first portion extending from the first side to the second side along a first direction; and

a second portion connected to the first portion and extending to the mixed flow area along a second direction, wherein the first direction intersects the second direction.

5. The heat exchanger according to claim 4, wherein each of the second dissipation fins is L-shaped, and each of the second dissipation fins comprises:

a third portion extending from the first side to the second side along the first direction; and

a fourth portion connected to the third portion and extending to the mixed flow area along a third direction, wherein the third direction is opposite to the second direction.

6. The heat exchanger according to claim 4, wherein each of the second dissipation fins is in a linear shape and extends from the first side to the mixed flow area along the first direction.

7. The heat exchanger according to claim 1, further comprising a mixed flow means disposed in the mixed flow area and being separated from the first dissipation fins and the second dissipation fins

8. The heat exchanger according to claim 7, wherein the mixed flow means comprises a partition lying in a flowing path of the fluid.

9. The heat exchanger according to claim 1, wherein the bypass channel is located at an outermost side of the first channels and is adjacent to an inner wall of the chamber.

10. The heat exchanger according to claim 1, wherein the base plate comprises a vapor chamber.

11. The heat exchanger according to claim 1, wherein at least one of a surface of the first dissipation fins, a surface of the second dissipation fins and an inner wall of the chamber comprises a plurality of cavities.

12. The heat exchanger according to claim 11, wherein the cavities correspond to a location of the heat source and penetrate through the base plate to be connected to a bottom of the heat source.

13. The heat exchanger according to claim 1, wherein a material of the base plate comprises metals or composite materials.