Thermal packaging structure for flexible chips

Abstract

This invention discloses a heat dissipation packaging structure for a flexible chip, comprising a flexible chip, a graphene layer, and a hydrogel layer. The graphene layer is attached to the back side of the flexible chip, and the hydrogel layer is attached to the side of the graphene layer away from the flexible chip. By sequentially attaching the graphene layer and the hydrogel layer to the back side of the flexible chip, the graphene layer rapidly and evenly dissipates the heat generated by the flexible chip to its surface, while the hydrogel layer, with its high specific heat, absorbs the heat, effectively reducing the rate of temperature rise of the flexible chip and significantly improving the heat dissipation effect. Moreover, both the graphene layer and the hydrogel layer are flexible materials and do not affect the bending action of the flexible chip.

Description

Technical Field

[0001] This invention relates to the technical field of heat dissipation for flexible chips, and in particular to a heat dissipation packaging structure for flexible chips. Background Technology

[0002] With the rapid development of flexible electronics technology and the semiconductor industry, semiconductor devices are gradually evolving towards ultra-thinness and high integration. Chip thinning technology can not only reduce the thermal resistance and power consumption of chips, but also endow chips with flexible mechanical characteristics within a certain thickness range. This flexibility perfectly meets the current practical engineering needs, such as wearable devices, conformal integrated circuits, and flexible display devices. However, many problems still exist in the actual design, manufacturing, and use of flexible chips. Among them, the heat dissipation problem of ultra-thin flexible chips is a key issue restricting the flexible application of chips with high power consumption levels. Because currently, flexible devices are integrated on flexible substrates made of thin film materials, and the thermal conductivity of such thin film materials is usually low, the heat generated by the chip cannot be effectively dissipated. Excessive temperature can cause the chip to burn out, leading to the failure of the microsystem. However, due to the constraints of the material system, flexible structure and efficient heat dissipation design are contradictory. The concept of flexible chips has only been proposed in recent years, and there are currently no relevant large-scale digital processing or power chip flexibility cases. There are almost no existing structures capable of heat dissipating heat at the chip level. Summary of the Invention

[0003] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide a heat dissipation packaging structure for flexible chips, so as to solve the problem that heat dissipation of flexible chips is difficult in the existing technology.

[0004] The objective of this invention is achieved through the following technical solution: The present invention provides a heat dissipation packaging structure for a flexible chip, comprising a flexible chip, a graphene layer and a hydrogel layer, wherein the graphene layer is attached to the back side of the flexible chip and the hydrogel layer is attached to the side of the graphene layer away from the flexible chip.

[0005] Furthermore, the hydrogel layer is an ionic hydrogel doped with LiCl.

[0006] Furthermore, the materials of the hydrogel layer include solvent, acrylamide monomer, LiCl, methylenebisacrylamide, and ammonium persulfate.

[0007] Furthermore, the method for fabricating the hydrogel layer includes: Prepare an aqueous solution of acrylamide monomer with a concentration of 1-3 mol / L; LiCl was added to the acrylamide monomer aqueous solution to make the LiCl concentration reach 7-10 mol / L, so as to obtain the first mixed aqueous solution; Add 0.05-0.2 mol / L of methylenebisacrylamide to the first mixed aqueous solution, wherein the ratio of methylenebisacrylamide to the first mixed aqueous solution is 1:150-1:250, to obtain a second mixed aqueous solution; Add 0.05-0.2 mol / L of ammonium persulfate to the second mixed aqueous solution, wherein the ratio of ammonium persulfate to the second mixed aqueous solution is 7:900-7:1200, to obtain an ionic hydrogel solution, which solidifies to form the hydrogel layer.

[0008] Furthermore, the method for fabricating the hydrogel layer includes: The ionic hydrogel solution is placed in a mold and heated at 65-85 degrees Celsius for 4-6 hours until fully cured.

[0009] Furthermore, the heat dissipation packaging structure includes a DAF thermally conductive adhesive layer, which is disposed between the graphene layer and the flexible chip, and is used to bond the graphene layer to the back side of the flexible chip.

[0010] Furthermore, the thickness of the DAF thermally conductive adhesive layer is 5-10 μm, and the thickness of the graphene layer is 20-40 μm.

[0011] Furthermore, the heat dissipation packaging structure includes a flexible circuit board, and the flexible chip is bonded to the flexible circuit board and electrically connected to the flexible circuit board.

[0012] Furthermore, the flexible circuit board has through holes, the back side of the flexible chip protrudes from the through holes, and the area of ​​the graphene layer is larger than the area of ​​the through holes and is attached to the back side of both the flexible chip and the flexible circuit board.

[0013] Furthermore, the heat dissipation packaging structure includes a sealant, which is disposed on the front side of the flexible chip and the flexible circuit board and covers the flexible chip and the through hole.

[0014] The beneficial effects of this invention are as follows: by sequentially attaching a graphene layer and a hydrogel layer to the back of the flexible chip, the graphene layer rapidly and evenly heats the heat generated by the flexible chip to the surface of the graphene layer, and the hydrogel layer, which has a large specific heat, absorbs the heat, effectively reducing the rate of temperature rise of the flexible chip and greatly improving the heat dissipation effect of the flexible chip; moreover, both the graphene layer and the hydrogel layer are flexible materials and will not affect the bending action of the flexible chip. Attached Figure Description

[0015] Figure 1 A schematic diagram of the heat dissipation packaging structure of the flexible chip in this invention.

[0016] Figure 2 This is a heat dissipation test diagram for flexible chips that do not have a heat dissipation structure in existing technology.

[0017] Figure 3 The heat dissipation curve of the flexible chip heat dissipation packaging structure in this invention.

[0018] Figure 4 A comparison diagram of the heat dissipation packaging structure of the flexible chip in the prior art and the invention. Detailed Implementation

[0019] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of the flexible chip heat dissipation packaging structure proposed according to the present invention: Figure 1 A schematic diagram of the heat dissipation packaging structure of the flexible chip in this invention. (See diagram below.) Figure 1 As shown, the present invention provides a heat dissipation packaging structure for a flexible chip, comprising a flexible chip 10, a graphene layer 30, and a hydrogel layer 40. The graphene layer 20 is attached to the back side of the flexible chip 10, and the hydrogel layer 30 is attached to the side of the graphene layer 20 away from the flexible chip 10. The side of the flexible chip 10 with pads for bonding is the front side, and the opposite side is the back side.

[0020] This application involves sequentially attaching a graphene layer 30 and a hydrogel layer 40 to the back of a flexible chip 10. Because the graphene layer 30 has extremely high thermal conductivity (2000 W·mK) throughout its plane, the heat generated by the flexible chip 10 can be rapidly and evenly distributed across the entire surface of the graphene layer 30. The hydrogel layer 40, with its high specific heat, absorbs this heat. During heating, the water in the hydrogel material rapidly dissipates, carrying away a significant amount of heat and effectively reducing the temperature rise rate of the flexible chip 10. This greatly improves the heat dissipation effect of the flexible chip 10. The overall heat dissipation structure can effectively control the temperature of the flexible chip 10 for a period of time, ensuring that the flexible chip 10 does not burn out due to high temperatures. Furthermore, both the graphene layer 30 and the hydrogel layer 40 are flexible materials and do not affect the bending motion of the flexible chip 10.

[0021] Furthermore, the graphene layer 20 has a thickness of 20-40 μm. The graphene layer 20 is a composite film containing a single layer of graphene material. The ultra-thin graphene layer 20 can significantly improve the heat transfer from the flexible chip 10 to the hydrogel layer 40. Because graphene has extremely high lateral thermal conductivity, it can greatly reduce the rate of heat accumulation in the flexible chip 10.

[0022] In this embodiment, the heat dissipation packaging structure includes a DAF thermally conductive adhesive layer 20, which is disposed between the graphene layer 20 and the flexible chip 10, and is used to bond the graphene layer 20 to the back side of the flexible chip 10. The thickness of the DAF thermally conductive adhesive layer 20 is 5-10 μm. DAF (Die Attach Film) is a high-performance adhesive film with excellent adhesion and thermal conductivity, maintaining stability in high-temperature environments, providing reliable mechanical connections and thermal management for the chip, and further improving the speed of heat transfer from the chip to the graphene layer 30.

[0023] In this embodiment, the hydrogel layer 30 is an ionic hydrogel doped with LiCl (lithium chloride). The materials of the hydrogel layer 30 include a solvent, acrylamide monomer, LiCl, methylenebisacrylamide, and ammonium persulfate. The cooling mechanism of the hydrogel material has two parts: the water mass fraction in the hydrogel material is approximately 86%, and the high specific heat of water effectively slows down the overall temperature rise; simultaneously, during heating, the water in the hydrogel material dissipates rapidly, carrying away a large amount of heat. Considering that the hydrogel material will fail after water loss, this application has specially formulated an ionic hydrogel doped with a large amount of LiCl. This hydrogel material absorbs moisture from the air under natural conditions to replenish itself, thus solving the storage problem of this packaging design and providing the possibility of reusing the hydrogel material. During the high-power operation of the flexible chip 10, a large amount of water evaporates; however, during the non-operational or low-power operation of the flexible chip 10, the hydrogel material can slowly replenish itself with water from the air, restoring it to its initial state. After testing, the hydrogel material showed no change in mass and no water loss after being placed in a normal temperature and humidity environment for 14 days. At the same time, the hydrogel material that lost water during the previous test also recovered to its original mass at room temperature, proving that the hydrogel material has the ability to be stored and reused.

[0024] Among them, the modulus of the DAF thermally conductive adhesive layer 20 is in the kPa range and the thickness is relatively thin; the thickness of the graphene layer 20 is about 25 micrometers, so the graphene layer 20 can exhibit flexibility and will not be damaged during bending; the modulus of the hydrogel layer 40 in contact with it is also in the kPa range, which is 6-8 orders of magnitude smaller than the modulus of the flexible chip 10, and will not affect the bending performance of the overall device. Therefore, the structure of the above composite layers can be considered as fully flexible, and has minimal impact on the stress of the flexible chip 10 in the bending state.

[0025] Furthermore, the method for fabricating the hydrogel layer 30 includes: Prepare an aqueous solution of acrylamide monomer with a concentration of 1-3 mol / L (e.g., 2 mol / L); LiCl is added to an aqueous solution of acrylamide monomer to achieve a LiCl concentration of 7-10 mol / L (e.g., 8 mol / L) to obtain a first mixed aqueous solution; Add 0.05-0.2 mol / L (e.g., 0.1 mol / L) of methylenebisacrylamide (MBAA) as a crosslinking agent to the first mixed aqueous solution. The ratio of methylenebisacrylamide to the first mixed aqueous solution is 1:150-1:250 (e.g., 1:200) to obtain a second mixed aqueous solution. Add 0.05-0.2 mol / L (e.g., 0.1 mol / L) of ammonium persulfate (APS) to the second mixed aqueous solution as an initiator. The ratio of ammonium persulfate to the second mixed aqueous solution is 7:900-7:1200 (e.g., 7:1000). Mix and shake for 3 minutes until homogeneous to obtain an ionic hydrogel solution. After the ionic hydrogel solution solidifies, a hydrogel layer 30 is formed.

[0026] The methods for solidifying ion-hydrogel solutions include: Place the ionic hydrogel solution into a mold and heat at 65-85 (e.g. 70) degrees Celsius for 4-6 (e.g. 5) hours until fully cured.

[0027] In this embodiment, the heat dissipation packaging structure includes a flexible circuit board 50, and the flexible chip 10 is bonded to the flexible circuit board 50 and electrically connected to the flexible circuit board 50, thereby providing power and transmitting signals to the flexible chip 10 through the flexible circuit board 50.

[0028] Furthermore, the flexible circuit board 50 has a through-hole 501, through which the back side of the flexible chip 10 protrudes. The graphene layer 20 has an area larger than the through-hole 501 and is attached to both the flexible chip 10 and the back side of the flexible circuit board 50. The area of ​​the graphene layer 20 is more than three times the size of the flexible chip 10, and more than nine times larger, covering not only the flexible chip 10 within the through-hole 501 but also part of the flexible circuit board 50, significantly improving heat dissipation. The DAF thermally conductive adhesive layer 20, the graphene layer 20, and the hydrogel layer 40 have the same planar dimensions, meaning they overlap vertically.

[0029] In this embodiment, the heat dissipation encapsulation structure includes a sealant 60, which is disposed on the front side of the flexible chip 10 and the flexible circuit board 50, covering the flexible chip 10 and the through hole 501. The sealant 60 can be made of silicone, which not only protects the flexible chip 10 but also enhances heat dissipation.

[0030] In this embodiment, the flexible chip 10 includes a chip body 11, a frame 12, and a cover plate 13. The chip body 11 is disposed within the receiving hole of the frame 12, and its top is sealed by the cover plate 13. Both the frame 12 and the cover plate 13 are made of flexible material. The cover plate 13 has circuitry and pads and is electrically connected to the chip body 11. Preferably, the receiving hole of the frame 12 can also be a through hole, exposing the bottom of the chip body 11; alternatively, the bottom wall of the receiving hole in the frame 12 can be thinned to increase heat dissipation.

[0031] Figure 2 This is a heat dissipation test diagram for flexible chips that do not have a heat dissipation structure in existing technology. Figure 3 The thermal curve of the heat dissipation packaging structure of the flexible chip in this invention. For example... Figure 2 and Figure 3 As shown in the figure, the experiment demonstrates that without any heat dissipation structure, the heating pad operates at a steady-state temperature of 164°C at a room temperature of 22°C and a power consumption of 8W. However, after integrating the heat dissipation packaging structure of this invention, the chip temperature did not exceed 100°C during the two-hour heating process, and was kept below 90°C in the first 30 minutes. This experiment shows that for chips with this power consumption level, the heat dissipation packaging structure can effectively reduce the steady-state temperature of the chip package, thereby enabling flexible package design for higher power consumption chips.

[0032] Figure 4 A comparison diagram of the heat dissipation packaging structure of the flexible chip in the prior art and the invention. Figure 4 The test was based on the FPGA7010 flexible signal chip. The temperature performance of this chip after power-on was compared with the temperature rise of a chip without any heat dissipation treatment. Figure 4 As shown, in terms of heat dissipation, under the same operating time, the junction temperature of the flexible FPGA chip integrating this heat dissipation package structure is lower, remaining below 60℃. In summary, this heat dissipation package structure has strong heat dissipation capabilities and meets the characteristics of flexibility.

[0033] In this document, the directional terms such as up, down, left, right, front, and back are defined according to the position of the structures in the accompanying drawings and the relative positions of the structures, and are only used for clarity and convenience in expressing the technical solution. It should be understood that the use of these directional terms should not limit the scope of protection claimed in this application. It should also be understood that the terms "first" and "second," etc., used herein are only used for distinction in name and are not used to limit the number or order.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content without departing from the scope of the technical solution of the present invention, which are equivalent embodiments with equivalent changes. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the technical solution of the present invention shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A heat dissipation packaging structure for a flexible chip, characterized in that, It includes a flexible chip (10), a graphene layer (30) and a hydrogel layer (40), wherein the graphene layer (20) is attached to the back side of the flexible chip (10) and the hydrogel layer (30) is attached to the side of the graphene layer (20) away from the flexible chip (10).

2. The heat dissipation packaging structure for the flexible chip according to claim 1, characterized in that, The hydrogel layer (30) is an ionic hydrogel doped with LiCl.

3. The heat dissipation packaging structure for the flexible chip according to claim 2, characterized in that, The materials of the hydrogel layer (30) include solvent, acrylamide monomer, LiCl, methylenebisacrylamide and ammonium persulfate.

4. The heat dissipation packaging structure for the flexible chip according to claim 3, characterized in that, The method for preparing the hydrogel layer (30) includes: Prepare an aqueous solution of acrylamide monomer with a concentration of 1-3 mol / L; LiCl was added to the acrylamide monomer aqueous solution to make the LiCl concentration reach 7-10 mol / L, so as to obtain the first mixed aqueous solution; Add 0.05-0.2 mol / L of methylenebisacrylamide to the first mixed aqueous solution, wherein the ratio of methylenebisacrylamide to the first mixed aqueous solution is 1:150-1:250, to obtain a second mixed aqueous solution; Add 0.05-0.2 mol / L of ammonium persulfate to the second mixed aqueous solution, wherein the ratio of ammonium persulfate to the second mixed aqueous solution is 7:900-7:1200, to obtain an ionic hydrogel solution, which solidifies to form the hydrogel layer (30).

5. The heat dissipation packaging structure for the flexible chip according to claim 4, characterized in that, The method for preparing the hydrogel layer (30) includes: The ionic hydrogel solution is placed in a mold and heated at 65-85 degrees Celsius for 4-6 hours until fully cured.

6. The heat dissipation packaging structure for a flexible chip according to any one of claims 1-5, characterized in that, The heat dissipation packaging structure includes a DAF thermally conductive adhesive layer (20), which is disposed between the graphene layer (20) and the flexible chip (10) and is used to bond the graphene layer (20) to the back of the flexible chip (10).

7. The heat dissipation packaging structure for a flexible chip according to claim 6, characterized in that, The thickness of the DAF thermally conductive adhesive layer (20) is 5-10 μm, and the thickness of the graphene layer (20) is 20-40 μm.

8. The heat dissipation packaging structure for a flexible chip according to any one of claims 1-5, characterized in that, The heat dissipation packaging structure includes a flexible circuit board (50), and the flexible chip (10) is bonded to the flexible circuit board (50) and electrically connected to the flexible circuit board (50).

9. The heat dissipation packaging structure for a flexible chip according to claim 8, characterized in that, The flexible circuit board (50) has a through hole (501), and the back side of the flexible chip (10) protrudes from the through hole (501). The area of ​​the graphene layer (20) is larger than the area of ​​the through hole (501) and is attached to the back side of both the flexible chip (10) and the flexible circuit board (50).

10. The heat dissipation packaging structure for a flexible chip according to claim 8, characterized in that, The heat dissipation packaging structure includes a sealant (60), which is disposed on the front side of the flexible chip (10) and the flexible circuit board (50) and covers the flexible chip (10) and the through hole (501).

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