Embedded circuit board and preparation method thereof

Abstract

The invention provides an embedded circuit board. The embedded circuit board comprises a circuit substrate, an electronic element embedded in the circuit substrate and a heat dissipation piece arranged in the circuit substrate. The heat dissipation piece comprises a first end part and a second end part which are oppositely arranged in a first direction, the first end part is arranged in the circuit substrate, the first end part is adjacent to the electronic element in a second direction perpendicular to the first direction, and the end face, deviating from the first end part, of the second end part is exposed out of the circuit substrate. The heat dissipation piece comprises a heat conduction shell and heat dissipation liquid, a closed cavity is formed in the heat conduction shell, part of the cavity is filled with the heat dissipation liquid, and the boiling point of the heat dissipation liquid under the standard atmospheric pressure ranges from 35 DEG C to 55 DEG C. The embedded circuit board provided by the invention has relatively high reliability. The invention also provides a preparation method of the embedded circuit board.

Description

Technical Field

[0001] The present application relates to the field of circuit boards, and in particular to an embedded circuit board and a preparation method thereof. Background Art

[0002] A circuit board with embedded electronic components usually needs to embed a metal block, such as a copper block, on one side of the electronic component so that the heat generated by the operation of the electronic component can be transferred to the environment through the metal block to achieve internal cooling of the circuit board. However, when the ambient temperature is higher than the internal temperature of the circuit board, the ambient temperature will also be transferred to the circuit board through the metal block, causing the component to overheat, thereby reducing the reliability of the circuit board. Summary of the invention

[0003] In view of this, the present application provides an embedded circuit board that is beneficial for improving reliability.

[0004] The present application provides an embedded circuit board, comprising a circuit substrate and an electronic component embedded in the circuit substrate, the embedded circuit board also comprising a heat sink arranged in the circuit substrate. The heat sink comprises a first end and a second end arranged opposite to each other in a first direction. The first end is arranged in the circuit substrate, the first end is arranged adjacent to the electronic component in a second direction perpendicular to the first direction, and the end face of the second end facing away from the first end is exposed to the circuit substrate. The heat sink comprises a heat-conducting shell and a heat-dissipating liquid, a sealed cavity is arranged in the heat-conducting shell, the heat-dissipating liquid is filled in part of the cavity, and the boiling point of the heat-dissipating liquid at standard atmospheric pressure is 35 to 55°C.

[0005] In some possible embodiments, the heat-conductive shell includes two shell bodies and an adhesive layer bonding the two shell bodies, each of the shell bodies includes a first surface and a second surface connected along a circumferential direction, a portion of the first surface is provided with a first groove, and the first grooves of the two shell bodies are connected to form the cavity.

[0006] In some possible embodiments, the shell body includes a first part, a second part, and a third part connected along the first direction, the first part, the second part, and the third part together form the first groove, the first parts of the two shell bodies are bonded to form the first end part, the first end part is a conical structure, and the third parts of the two shell bodies are bonded to form the second end part.

[0007] In some possible embodiments, the second surface of each shell body is provided with a plurality of protrusions arranged at intervals along the first direction, the protrusions are provided on the second part and the third part, the protrusions provided on the two shell bodies are spliced ​​to form a spiral protrusion together, the shell body and the spiral protrusions together form a chip guide groove, and the chip guide groove has two open ends.

[0008] In some possible implementations, the second end portion is provided with a snap-fit ​​groove spaced from the cavity in the first direction, and an opening of the snap-fit ​​groove is located at the end surface.

[0009] The present application also provides a method for preparing an embedded circuit board, comprising the following steps:

[0010] Providing a substrate, the substrate comprising a circuit substrate and electronic components embedded in the circuit substrate;

[0011] A heat sink is provided, the heat sink comprising a first end and a second end arranged opposite to each other in a first direction, the heat sink comprising a heat-conducting housing and a heat-dissipating liquid, a closed cavity is provided in the heat-conducting housing, a portion of the cavity is filled with the heat-dissipating liquid, and the boiling point of the heat-dissipating liquid under standard atmospheric pressure is 35 to 55° C.; and

[0012] The heat sink is inserted into the circuit substrate from at least one surface of the circuit substrate, so that the first end is embedded in the circuit substrate and arranged adjacent to the electronic component in a second direction perpendicular to the first direction, and the end surface of the second end facing away from the first end is exposed on the circuit substrate.

[0013] In some possible embodiments, the preparation of the heat sink includes the following steps: providing two heat dissipation substrates, each of the heat dissipation substrates including a shell body, the shell body including a first surface and a second surface connected along a circumferential direction, and a portion of the first surface being provided with a first groove; adding the heat dissipation liquid into a first groove under vacuum conditions where the ambient temperature is lower than the boiling point of the heat dissipation liquid; forming an adhesive layer on an area of ​​the first surface of at least one of the shell bodies where the first groove is not provided; stacking and pressing the two shell bodies facing each other so that the adhesive layer bonds the two shell bodies to obtain the heat-conducting shell, and the first grooves of the two shell bodies are connected to form the cavity.

[0014] In some possible embodiments, the shell body includes a first part, a second part and a third part connected along the first direction, and the first part, the second part and the third part together form the first groove; in the step of forming the cavity, the first parts of the two shell bodies are bonded to form the first end part, and the first end part is a conical structure, and the third parts of the two shell bodies are bonded to form the second end part.

[0015] In some possible embodiments, the second surface of each of the shell bodies is provided with a plurality of convex edges arranged at intervals along the first direction, the convex edges are provided on the second part and the third part, and the plurality of convex edges are twisted along the same clockwise direction; in the step of forming the cavity, the convex edges provided on the two shell bodies are spliced ​​to jointly form a spiral convex edge, and the shell body and the spiral convex edge jointly form a chip guide groove, and the chip guide groove has two open ends.

[0016] In some possible embodiments, the first surface of each of the shell bodies is also provided with a second groove that passes through the end surface of the third part away from the second part along the first direction, the second groove is arranged spaced apart from the first groove in the first direction, and the adhesive layer is arranged in an area of ​​the third part where the second groove is not provided; in the step of forming the cavity, the second grooves provided in the two shell bodies are connected to form a snap-fit ​​groove, and the opening of the snap-fit ​​groove is provided on the end surface.

[0017] In the present application, a heat sink is inserted into a circuit substrate with embedded components, so that the heat generated by the components is conducted away through the heat sink. The heat sink includes a heat-conducting shell and a heat-dissipating liquid. The heat-dissipating liquid is filled in a closed cavity provided in the heat-conducting shell. In addition, the boiling point of the heat-dissipating liquid under standard atmospheric pressure is 35 to 55°C, so that the heat-dissipating liquid will undergo a gasification reaction after absorbing a certain amount of heat. By utilizing the convection difference of the gas in the first direction (pressure causes the gas to flow faster from bottom to top and slower from top to bottom), the heat sink's ability to conduct the heat of the circuit substrate to the environment is much greater than conducting the heat of the environment into the circuit substrate. Therefore, the embedded circuit board of the present application can still effectively dissipate heat when the ambient temperature is higher than the internal temperature of the circuit board, so that the embedded circuit board has higher reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the structure of a heat dissipation substrate formed by a forming mold provided in an embodiment of the present application;

[0019] Figure 2 for Figure 1 A schematic diagram of the structure of the heat dissipation substrate shown;

[0020] Figure 3 For Figure 1 A schematic structural diagram of adding heat dissipation liquid into the first groove of the heat dissipation substrate shown;

[0021] Figure 4 For Figure 3 The schematic structural diagram of the heat dissipation substrate having the first groove formed on the surface thereof;

[0022] Figure 5 For the general Figure 1 as well as Figure 4 The schematic diagram of the structure in which the heat dissipation substrates are stacked facing each other is shown;

[0023] Figure 6 Reason Figure 5 A side view of a heat sink obtained by stacking the heat dissipation substrates to form a heat-conducting housing;

[0024] Figure 7 For Figure 6 A side view of a heat conductive housing having a reinforcement layer formed thereon;

[0025] Figure 8 A cross-sectional view of a substrate provided in one embodiment of the present application;

[0026] Fig. 9 For the general Figure 7 Heat sink insert shown Figure 8 A cross-sectional view of the embedded circuit board obtained in the substrate shown;

[0027] Fig.10 for Fig. 9 An enlarged view of part A is shown.

[0028] Main component symbols

[0029] Molding mold 200 Embedded circuit board 100

[0030] Circuit board 10 Carrier board 11

[0031] Circuit unit 12 Base material layer 121

[0032] Circuit layer 122 Accommodating cavity 111

[0033] Substrate 101 Electronic component 20

[0034] Heat sink 30 cavity 301

[0035] Snap-fit ​​groove 302 Heat dissipation base 303

[0036] First groove 304 Second groove 305

[0037] First end 35 Second end 36

[0038] Heat-conducting housing 31 Shell body 311

[0039] Part 1 3111 Part 2 3112

[0040] Adhesive layer 312 Chip guide groove 313

[0041] Open end 314 heat dissipation liquid 32

[0042] Spiral ridge 33 Reinforcement layer 34

[0043] First direction X convex edge 331

[0044] Part 3 3113 Second Direction Y

[0045] First surface 306 Second surface 307

[0046] The following specific implementation methods will further illustrate the present application in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0048] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. When an element is considered to be "set on" another element, it may be directly set on the other element or there may be a central element at the same time.

[0049] Embodiment 1:

[0050] The present application provides a method for preparing an embedded circuit board. According to different requirements, the order of steps of the preparation method can be changed, and some steps can be omitted or combined. The preparation method comprises the following steps:

[0051] Step 1: Reference Figure 1 , heat dissipation substrates 303 are respectively formed in two molding dies 200 (only the female mold of the molding dies is shown in the figure). Exemplarily, the heat dissipation substrate 303 can be formed by compression molding metal (such as copper). A heat dissipation substrate 303 is formed in a molding die 200.

[0052] Reference Figure 2, each heat dissipation substrate 303 includes a shell body 311. The side of the shell body 311 is divided into a first surface 306 and a second surface 307. The first surface 306 and the second surface 307 are connected in the circumferential direction of the shell body 311. Part of the first surface 306 is provided with a first groove 304. In some embodiments, the shell body 311 includes a first portion 3111, a second portion 3112 and a third portion 3113 connected along the first direction X. The first portion 3111, the second portion 3112 and the third portion 3113 together form the first groove 304. Specifically, the first portion 3111 can constitute the bottom surface of the first groove 304, and the first portion 3111 and the third portion 3113 respectively constitute two opposite side surfaces of the first groove 304 in the first direction X. In some embodiments, the first surface 306 of each shell body 311 is also provided with a second groove 305 that penetrates the end surface of the third portion 3113 away from the second portion 3112 along the first direction X. The second groove 305 is arranged in the first direction X spaced from the first groove 304.

[0053] In some embodiments, the second surface 307 of each shell body 311 is provided with a plurality of convex edges 331 arranged at intervals along the first direction X. The convex edges 331 may be provided on the second portion 3112 and the third portion 3113. The plurality of convex edges 331 are all twisted in the same clockwise direction. Exemplarily, the plurality of convex edges 331 may be all twisted in the clockwise direction.

[0054] Step 2: Reference Figure 3 , add heat dissipation liquid 32 into a first groove 304. Exemplarily, the heat dissipation liquid 32 can be added by dripping with a dropper. The operating condition for adding the heat dissipation liquid 32 is a vacuum condition where the ambient temperature is lower than the boiling point of the heat dissipation liquid 32, thereby ensuring that the heat dissipation liquid 32 does not vaporize and volatilize during the addition process. In some embodiments, the boiling point of the heat dissipation liquid 32 at standard atmospheric pressure is 35 to 55° C. Exemplarily, the heat dissipation liquid 32 can be one of pentane, methyl formate, 3-methyl-1-pentene or 4-methyl-1-pentene. Exemplarily, the heat dissipation liquid 32 can fill part of the first groove 304.

[0055] Step 3: Reference Figure 4 , an adhesive layer 312 is formed in an area where the first surface 306 of at least one shell body 311 is not provided with the first groove 304 and the second groove 305. In this embodiment, the adhesive layer 312 can be formed by brushing on the first part 3111, the second part 3112 and the third part 3113. Exemplarily, the material of the adhesive layer 312 can be one of anaerobic glue, polyurethane glue, modified phenolic glue or α-cyanoacrylate glue, such as quick-drying glue ergo5922, ergo5901 or ergo5923.

[0056] Step 4: Reference Figure 5 and Figure 6, the two shell bodies 311 are stacked and pressed relative to each other to obtain the heat sink 30. The adhesive layer 312 bonds the two shell bodies 311 to obtain the heat-conducting shell 31. The first grooves 304 of the two shell bodies 311 are connected to form a closed cavity 301, so that the heat dissipation liquid 32 fills part of the cavity 301. The first parts 3111 of the two shell bodies are bonded to form a first end 35. The first end 35 is a cone structure. Exemplarily, the cone structure can be a triangular pyramid, a circular cone or a quadrangular pyramid. The third parts 3113 of the two shell bodies 311 are bonded to form a second end 36. The convex edges 331 provided on the two shell bodies 311 are spliced ​​together to form a spiral convex edge 33, and the spiral center of the spiral convex edge 33 is arranged along the first direction X. The shell body 311 and the spiral convex edge 33 together form a chip guide groove 313. The chip guide groove 313 has two open ends 314. One open end 314 is provided at the second end 36. The other open end 314 is disposed in the area of ​​the second portion 3112 adjacent to the first portion 3111. The second grooves 305 disposed in the two shell bodies 311 are connected to form a snap-fit ​​groove 302. The opening of the snap-fit ​​groove 302 is disposed at the end surface of the second end portion 36 away from the first end portion 35. Exemplarily, the snap-fit ​​groove 302 can be a straight groove, a hexagonal groove or a cross groove.

[0057] Step 5: Reference Figure 7 , a reinforcement layer 34 is formed on the surface of the first end portion 35. The reinforcement layer 34 is used to improve the hardness of the heat sink 30. Exemplarily, the material of the reinforcement layer 34 can be one of tungsten steel alloy, tungsten cobalt alloy or tungsten titanium cobalt alloy. The reinforcement layer 34 can be formed by chemical vapor deposition or physical vapor deposition.

[0058] In another embodiment, a heat sink 30 may be provided directly. The heat sink 30 includes a first end 35 and a second end 36 that are arranged opposite to each other in the first direction X. The heat sink 30 includes a heat-conducting housing 31 and a heat-dissipating liquid 32. A sealed cavity 301 is provided in the heat-conducting housing 31. The heat-dissipating liquid 32 fills part of the cavity 301. The boiling point of the heat-dissipating liquid 32 at standard atmospheric pressure is 35 to 55°C.

[0059] Step 6: Reference Figure 8 , providing a substrate 101. The substrate 101 includes a circuit substrate 10 and an electronic component 20 embedded in the circuit substrate 10. Exemplarily, the electronic component 20 may be an active component, such as a chip.

[0060] Exemplarily, the preparation of the substrate 101 may include the following steps: providing a carrier 11 having a receiving cavity 111. Exemplarily, the material of the carrier 11 may be one of polyimide and liquid crystal polymer. The receiving cavity 111 may be formed by laser drilling. The electronic component 20 is placed in the receiving cavity 111. A circuit unit 12 covering the receiving cavity 111 is formed on at least one surface of the carrier 11. The circuit unit 12 includes a stacked substrate layer 121 and a circuit layer 122. The circuit unit 12 may be obtained by a semi-additive method, an additive method or a subtractive method.

[0061] Step 7: Reference Fig. 9 , insert the heat sink 30 into the circuit substrate 10 from at least one surface of the circuit substrate 10, so that the first end 35 is embedded in the circuit substrate 10 and is arranged adjacent to the electronic component 20 in the second direction Y perpendicular to the first direction X, thereby obtaining the embedded circuit board 100. The end surface of the second end 36 facing away from the first end 35 is exposed to the circuit substrate 10. The first end 35 is arranged adjacent to the electronic component 20, so that the heat generated by the electronic component 20 when working can be at least transferred to the first end 35 along the second direction Y. In this embodiment, since the first end 35 is a cone structure, a screwdriver can be directly used to engage with the engaging groove 302 to rotate and twist the heat sink 30 into the circuit substrate 10. At this time, there is no need to first form an opening for accommodating the heat sink 30 in the circuit substrate 10. In some embodiments, the first end 35 of the heat sink 30 is inserted into the carrier 11 along the first direction X. The heat sink 30 avoids the circuit pattern of the circuit layer 122 in the second direction Y.

[0062] In some other embodiments, an opening penetrating a surface of the circuit substrate 10 may be formed first, and then the heat sink 30 may be inserted into the opening.

[0063] Embodiment 2:

[0064] Reference Fig. 9 , an embodiment of the present application further provides an embedded circuit board 100. The embedded circuit board 100 includes a circuit substrate 10, an electronic component 20 and a heat sink 30. The electronic component 20 is embedded in the circuit substrate 10. Exemplarily, the circuit substrate 10 may include a carrier 11 of a accommodating cavity 111 and a circuit unit 12 stacked at opposite ends of the carrier 11. The circuit unit 12 may include a stacked base material layer 121 and a circuit layer 122. The electronic component 20 may be disposed in the accommodating cavity 111, and the circuit unit 12 covers the electronic component 20. The heat sink 30 is disposed in the circuit substrate 10. The heat sink 30 includes a first end 35 and a second end 36 that are oppositely disposed in a first direction X. The first end 35 is disposed in the circuit substrate 10. The first end 35 is disposed adjacent to the electronic component 20 in a second direction Y that is perpendicular to the first direction X. The end surface of the second end 36 facing away from the first end 35 is exposed to the circuit substrate 10. Referring to Fig.10The heat sink 30 includes a heat-conducting housing 31 and a heat-dissipating liquid 32. A sealed cavity 301 is provided in the heat-conducting housing 31. The heat-dissipating liquid 32 fills part of the cavity 301. The boiling point of the heat-dissipating liquid 32 under standard atmospheric pressure is 35-55°C.

[0065] The heat dissipation principle of the embedded circuit board 100 is as follows: when the electronic component 20 generates heat during operation, the heat can be transferred to the heat-conducting housing 31 through the medium (such as the substrate layer 121 and the carrier 11). The heat dissipation liquid 32 absorbs heat from the heat-conducting housing 31 and vaporizes, so that the heat dissipation liquid 32 is transformed from liquid to gas. Driven by the pressure difference in the cavity 301, the gas moves toward the second end 36. When the rising gas hits the second end 36 (because the second end 36 is exposed to the circuit substrate 10, the temperature of the second end 36 is lower than the first end 35), the latent heat of vaporization is released. The latent heat of vaporization is transferred to the atmosphere through the second end 36 to achieve heat dissipation and cooling of the embedded circuit board 100. When the ambient temperature is higher than the temperature in the embedded circuit board 100, the heat dissipation liquid 32 absorbs heat from the environment through the second end 36 and vaporizes. However, due to the effect of the pressure difference, the convection of the gas from top to bottom is very small, so that the rate at which the heat of the environment is transferred to the embedded circuit board 100 is very slow. Therefore, the embedded circuit board 100 of the present application can still effectively dissipate heat when the ambient temperature is higher than the internal temperature of the circuit board. Therefore, the embedded circuit board 100 provided by the present application has high reliability.

[0066] In the present application, a heat sink 30 is provided in the circuit substrate 10 in which the electronic component 20 is embedded, so that the heat generated by the electronic component 20 during operation is conducted through the heat sink 30. The heat sink 30 includes a heat-conducting housing 31 and a heat-dissipating liquid 32. The heat-dissipating liquid 32 is filled in a closed cavity 301 provided in the heat-conducting housing 31. And the boiling point of the heat-dissipating liquid 32 under standard atmospheric pressure is 35-55°C, so that the heat-dissipating liquid 32 will undergo a gasification reaction after absorbing a certain amount of heat. By utilizing the convection difference of the gas in the first direction X (pressure causes the gas to flow faster from bottom to top and slower from top to bottom), the heat sink 30 is able to conduct the heat of the circuit substrate 10 to the environment much more than conducting the heat of the environment into the circuit substrate 10. Therefore, the embedded circuit board 100 of the present application can still effectively dissipate heat when the ambient temperature is higher than the internal temperature of the circuit board, so that the embedded circuit board 100 has a higher reliability.

[0067] In some embodiments, reference Figure 5 , Fig. 9 and Fig.10The heat-conducting housing 31 includes an adhesive layer 312 and two housing bodies 311. Each housing body 311 includes a first surface 306 and a second surface 307 connected in a circumferential direction, and a portion of the first surface 306 is provided with a first groove 304. The adhesive layer 312 can be provided in an area of ​​the first surface 306 where the first groove 304 is not provided. The first grooves 304 provided in the two housing bodies 311 are connected to form a cavity 301. The heat-conducting housing 31 is formed by bonding the housing bodies 311 with the adhesive layer 312, which facilitates the molding of the heat sink 30.

[0068] In some embodiments, reference Figures 5 and 6 as well as Figures 9 and 10 The shell body 311 includes a first portion 3111, a second portion 3112 and a third portion 3113 connected along a first direction X. The first portion 3111, the second portion 3112 and the third portion 3113 together form a first groove 304. The first portions 3111 of the two shell bodies 311 are bonded to form a first end portion 35. The first end portion 35 is a cone structure. Exemplarily, the cone structure can be a triangular pyramid, a circular cone or a quadrangular pyramid. The shape of the first end portion 35 is set to facilitate the heat sink 30 to be directly inserted into the circuit substrate 10.

[0069] In some embodiments, the second surface 307 of each shell body 311 is provided with a plurality of flanges 331 arranged at intervals along the first direction X. The flanges 331 may be provided at the second portion 3112 and the third portion 3113. The plurality of flanges 331 may be twisted in the same clockwise direction. Exemplarily, the plurality of flanges 331 may all be twisted in a clockwise direction. The flanges 331 provided at the two shell bodies 311 are spliced ​​to form at least two spiral flanges 33 together. The shell body 311 and the spiral flanges 33 together form a chip guide groove 313. The chip guide groove 313 has two open ends 314. One open end 314 is provided at the second end portion 36. The other open end 314 is provided at the area of ​​the second portion 3112 adjacent to the first portion 3111. The provision of the chip guide groove 313 facilitates the direct insertion of the heat sink 30 into the circuit substrate 10 so that the debris generated can be guided out from the chip guide groove 313.

[0070] In some embodiments, reference Figures 5 and 6 as well as Figures 9 and 10 , the second end portion 36 is provided with a snap-fitting groove 302 spaced from the cavity 301 in the first direction X. The opening of the snap-fitting groove 302 is located at the end surface of the second end portion 36 away from the first end portion 35. In some embodiments, each shell body 311 is provided with a second groove 305 penetrating the end surface of the third portion 3113 away from the second portion 3112 in the first direction X. The second groove 305 is spaced from the first groove 304 in the first direction X. The second grooves 305 provided in the two shell bodies 311 are connected to form the snap-fitting groove 302. The provision of the snap-fitting groove 302 facilitates the heat sink 30 to be completely screwed into the circuit substrate 10, thereby reducing the interference of the heat sink 30 with the circuit substrate 10.

[0071] In some embodiments, a reinforcement layer 34 is further provided on the outer surface of the first end portion 35 to increase the hardness of the heat sink 30. The provision of the reinforcement layer 34 facilitates the insertion of the heat sink 30 into the circuit substrate 10.

[0072] The materials of the components in this embodiment are the same as those of the corresponding components in Embodiment 1, and thus they will not be described in detail.

[0073] The above description is only an optimized specific implementation of the present application, but it cannot be limited to this implementation in the actual application process. For ordinary technicians in this field, other variations and changes made according to the technical concept of the present application should all fall within the protection scope of the present application.

Claims

1. An embedded circuit board, comprising a circuit substrate and electronic components embedded in the circuit substrate, characterized in that: The embedded circuit board also includes a heat sink arranged in the circuit substrate, the heat sink includes a first end and a second end arranged opposite to each other in a first direction, the first end is arranged in the circuit substrate, the first end is arranged adjacent to the electronic component in a second direction perpendicular to the first direction, and the end surface of the second end facing away from the first end is exposed to the circuit substrate, the heat sink includes a heat-conducting shell and heat-dissipating liquid, a closed cavity is arranged in the heat-conducting shell, the heat-dissipating liquid fills part of the cavity, and the boiling point of the heat-dissipating liquid under standard atmospheric pressure is 35 to 55°C.

2. The embedded circuit board according to claim 1, characterized in that: The heat-conducting shell includes two shell bodies and an adhesive layer bonding the two shell bodies. Each of the shell bodies includes a first surface and a second surface connected along a circumferential direction. Part of the first surface is provided with a first groove. The first grooves of the two shell bodies are connected to form the cavity.

3. The embedded circuit board according to claim 2, characterized in that: The shell body includes a first part, a second part and a third part connected along the first direction, the first part, the second part and the third part together form the first groove, the first parts of the two shell bodies are bonded to form the first end part, the first end part is a cone structure, and the third parts of the two shell bodies are bonded to form the second end part.

4. The embedded circuit board according to claim 3, characterized in that: The second surface of each shell body is provided with a plurality of convex edges arranged at intervals along the first direction, the convex edges are provided on the second part and the third part, the convex edges provided on the two shell bodies are spliced ​​to form a spiral convex edge together, the shell body and the spiral convex edges together form a chip guide groove, and the chip guide groove has two open ends.

5. The embedded circuit board according to any one of claims 1 to 4, characterized in that: The second end portion is provided with a snap-fitting groove spaced from the cavity in a first direction, and an opening of the snap-fitting groove is located at the end surface.

6. A method for preparing an embedded circuit board, characterized in that: The steps include: Providing a substrate, the substrate comprising a circuit substrate and electronic components embedded in the circuit substrate; A heat sink is provided, the heat sink comprising a first end and a second end arranged opposite to each other in a first direction, the heat sink comprising a heat-conducting housing and a heat-dissipating liquid, a sealed cavity is provided in the heat-conducting housing, the heat-dissipating liquid fills part of the cavity, and the boiling point of the heat-dissipating liquid under standard atmospheric pressure is 35 to 55° C.; as well as The heat sink is inserted into the circuit substrate from at least one surface of the circuit substrate, so that the first end is embedded in the circuit substrate and arranged adjacent to the electronic component in a second direction perpendicular to the first direction, and the end surface of the second end facing away from the first end is exposed on the circuit substrate.

7. The method for preparing an embedded circuit board according to claim 6, characterized in that: The preparation of the heat sink comprises the following steps: Providing two heat dissipation substrates, each of the heat dissipation substrates comprises a shell body, the shell body comprises a first surface and a second surface connected along a circumferential direction, and a portion of the first surface is provided with a first groove; Adding the heat dissipation liquid into the first groove under vacuum conditions where the ambient temperature is lower than the boiling point of the heat dissipation liquid; forming an adhesive layer on a region of the first surface of at least one of the shell bodies where the first groove is not provided; The two shell bodies are stacked and pressed against each other so that the adhesive layer adheres the two shell bodies to obtain the heat-conducting housing, and the first grooves of the two shell bodies are connected to form the cavity.

8. The method for preparing an embedded circuit board according to claim 7, characterized in that: The shell body comprises a first portion, a second portion and a third portion connected along the first direction, wherein the first portion, the second portion and the third portion together form the first groove; In the step of forming the cavity, the first parts of the two shell bodies are bonded to form the first end, the first end is a cone structure, and the third parts of the two shell bodies are bonded to form the second end.

9. The method for preparing an embedded circuit board according to claim 8, characterized in that: The second surface of each shell body is provided with a plurality of convex edges arranged at intervals along the first direction, the convex edges are provided on the second portion and the third portion, and the plurality of convex edges are twisted along the same clockwise direction; In the step of forming the cavity, the convex edges provided on the two shell bodies are spliced ​​together to form a spiral convex edge, and the shell body and the spiral convex edge jointly form a chip guide groove, and the chip guide groove has two open ends.

10. The method for preparing an embedded circuit board according to claim 8, characterized in that: The first surface of each shell body is further provided with a second groove penetrating the end surface of the third part away from the second part along the first direction, the second groove is arranged spaced apart from the first groove in the first direction, and the adhesive layer is arranged in the area of ​​the third part where the second groove is not provided; In the step of forming the cavity, the second grooves provided on the two shell bodies are connected to form a snap-fit ​​groove, and the opening of the snap-fit ​​groove is provided on the end surface.

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