Heat dissipation sheet, circuit board, and electronic device

Abstract

To provide a flexible and bendable heat dissipation sheet bonded to a bendable region of a circuit board, and to provide a circuit board and an electronic device having the heat dissipation sheet.SOLUTION: The heat dissipation sheet 10 includes a first adhesive layer 20 adhered to the circuit board 1 and / or the chip 2, a heat dissipation layer 30 disposed on the first adhesive layer 20, a protection layer 50 disposed on the heat dissipation layer 30, and a plurality of heat dissipation holes 100 extending downwardly from an upper surface of the protection layer 50, wherein bottoms of the plurality of heat dissipation holes 100 are not lower than an upper surface of the first adhesive layer 20 or a lower surface of the heat dissipation layer 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a heat dissipation sheet, a circuit board having the heat dissipation sheet, and an electronic device. [Background technology]

[0002] In the prior art, chips are generally placed on printed circuit boards, and flexible circuit boards (e.g., tape carrier packages (TCP) or chip-on-film (COF)) are frequently used in electronic devices where there is little space to carry the chips due to their flexibility.

[0003] Chips or other electronic components on a circuit board may generate heat during operation, and to optimize the heat dissipation effect, a heat dissipation sheet is usually attached to the circuit board to cover the heat-generating chips or other electronic components.

[0004] In this regard, for example, see Patent Document 1, which specifically discloses in Figure 3 a display device including a flexible circuit board in a COF package. The flexible circuit board is provided with a chip that serves as a driver integrated circuit (IC) for the display panel, and a heat dissipation sheet that is adhered to the circuit board and covers the chip (see Figures 2A and 2B of Patent Document 1 for details). In particular, the heat dissipation sheet is also flexible and can be bent together with the flexible circuit board to suit electronic devices with small spaces. For other similar heat dissipation sheets, reference can also be made to Patent Document 2 of the applicant. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Taiwan Patent Application Publication No. 202207383 [Patent Document 2] Taiwan Patent Application Publication No. 202221868 Summary of the Invention

[0006] Through extensive research, the applicant has discovered that the above-mentioned prior art actually faces numerous problems. For example, in Patent Documents 1 and 2, the downward surface of a heat dissipation sheet is adhered to a circuit board or chip with an adhesive (e.g., a pressure-sensitive adhesive or a thermosetting resin), and an insulating protective layer is provided on the upward surface of the heat dissipation sheet. The insulating protective layer is generally formed of an insulating material, primarily related to polymer materials such as polyimide (PI), to provide the heat dissipation sheet with insulation and sufficient mechanical strength. The heat dissipation sheet can include an internal heat dissipation layer (e.g., a metal layer or graphite) to assist in heat dissipation from the underlying circuit board or chip. However, compared to the heat dissipation layer, polyimide itself is not considered a good thermal conductor (having a thermal conductivity of approximately 0.2 to 2 W / m·k). Therefore, heat transferred from the circuit board or chip to the heat dissipation layer cannot be transferred to the outside more quickly due to natural convection. Therefore, the heat dissipation effect of such conventional heat dissipation sheets still has room for improvement.

[0007] It was also found that such conventional heat dissipation sheets do not remain flat when adhered to a circuit board, and are often subject to bending as shown in Figures 2A and 2B of Patent Document 1. In addition, when such conventional heat dissipation sheets are adhered to a bendable region of the circuit board, as shown in Figure 3 of Patent Document 1, the degree of bending becomes more severe. In this case, a heat dissipation sheet with a small area is prone to peeling off from the circuit board due to stress, which is also a drawback that needs to be improved.

[0008] In view of the above, one embodiment of the present disclosure provides a novel heat dissipation sheet, more specifically, a flexible and bendable heat dissipation sheet that is adhered to a circuit board, more specifically, to a bendable region of the circuit board. The heat dissipation sheet includes a first adhesive layer that is adhered to the circuit board, a heat dissipation layer disposed on the first adhesive layer, a protective layer that is disposed on the heat dissipation layer, and a plurality of heat dissipation holes extending downward from an upper surface of the protective layer, the bottoms of the plurality of heat dissipation holes being no lower than the upper surface of the first adhesive layer or the lower surface of the heat dissipation layer on both sides. Preferably, the bottoms of the plurality of heat dissipation holes may be located within the heat dissipation layer, and more preferably, the bottoms of the plurality of heat dissipation holes are no lower than the upper surface of the heat dissipation layer.

[0009] In addition, another embodiment of the present disclosure provides a novel heat dissipation sheet, more specifically, a flexible and bendable heat dissipation sheet that is adhered to a circuit board, more specifically, adhered to a bendable region of the circuit board. The heat dissipation sheet includes a first adhesive layer that is adhered to the circuit board, a heat dissipation layer disposed on the first adhesive layer, a protective layer that is disposed on the heat dissipation layer, and a plurality of heat dissipation holes that extend downward from an upper surface of the protective layer, the heat dissipation sheet having two opposing edges, and the distance between the plurality of heat dissipation holes and one of the two edges is less than 25% of the distance between the two edges.

[0010] According to an embodiment of the present disclosure, there is further provided a circuit board including a substrate and the above-described heat dissipation sheet adhered to the substrate. According to an embodiment of the present disclosure, there is further provided an electronic device including the above-described circuit board and a chip disposed on the circuit board. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a structural schematic diagram of a heat dissipation sheet according to a first embodiment of the present disclosure. [Figure 2] 2 to 10 are schematic structural diagrams of heat dissipation sheets according to other different embodiments of the present disclosure. [Figure 3] 2 to 10 are schematic structural diagrams of heat dissipation sheets according to other different embodiments of the present disclosure. [Figure 4] 2 to 10 are schematic structural diagrams of heat dissipation sheets according to other different embodiments of the present disclosure. [Figure 5] 2 to 10 are schematic structural diagrams of heat dissipation sheets according to other different embodiments of the present disclosure. [Figure 6] 2 to 10 are schematic structural diagrams of heat dissipation sheets according to other different embodiments of the present disclosure. [Figure 7] 2 to 10 are schematic structural diagrams of heat dissipation sheets according to other different embodiments of the present disclosure. [Figure 8] 2 to 10 are schematic structural diagrams of heat dissipation sheets according to other different embodiments of the present disclosure. [Figure 9] 2 to 10 are schematic structural diagrams of heat dissipation sheets according to other different embodiments of the present disclosure. [Figure 10] 2 to 10 are schematic structural diagrams of heat dissipation sheets according to other different embodiments of the present disclosure. [Figure 11] FIG. 11 is a top view of a heat dissipation sheet according to one embodiment of the present disclosure. [Figure 12] FIG. 12 is a schematic diagram of an electronic device according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. In order to avoid obscuring the content of the present disclosure, conventional elements, related materials, and related processing techniques are omitted from the following description. Meanwhile, in order to clearly illustrate the present disclosure, various elements in the accompanying drawings are not necessarily drawn to actual scale or relative proportions.

[0013] 1, which shows a side view of a heat dissipation sheet 10 according to a first embodiment of the present disclosure. The heat dissipation sheet 10 is adhered to a circuit board 1 and / or a chip 2. For reference, the circuit board 1 and the chip 2 may each be a flexible circuit board (e.g., a tape carrier package (TCP) or a chip-on-film (COF)) in the prior art, and the heat dissipation sheet 10 may be adhered to a bendable region (not shown) of the circuit board 1.

[0014] As shown in the figure, the heat dissipation sheet 10 includes a first adhesive layer 20, a heat dissipation layer 30, a second adhesive layer 40, and a protective layer 50. In one embodiment, the first adhesive layer 20 is bonded to the circuit board 1 and / or the chip 2 with its bottom facing downward, and in another embodiment, it is bonded to the heat dissipation layer 30 with its top facing upward. The first adhesive layer 20 is formed from a material selected from adhesive materials such as double-sided tape, pressure-sensitive adhesive, and thermosetting resin, and typically has a thickness of 1 μm or more. For example, the first adhesive layer 20 is 8805 thermal conductive tape manufactured by 3M.

[0015] The heat dissipation layer 30 may be made of a material selected from thermally conductive / heat dissipative materials such as metal or graphite, etc. Preferably, the heat dissipation layer 30 may be copper foil or aluminum foil.

[0016] In one embodiment, the second adhesive layer 40 is bonded to the heat dissipation layer 30 with its downward facing contact, and in another embodiment, the second adhesive layer 40 is bonded to the protective layer 50 with its upward facing contact. The second adhesive layer 40 may be formed from the same or similar material as the first adhesive layer 20.

[0017] The protective layer 50 may be formed from a material selected from insulating materials such as organic polymer materials, and is also called an insulating layer. Preferably, the protective layer 50 may be a polyimide (PI) film.

[0018] Furthermore, as shown in FIG. 1 , the heat dissipation sheet 10 is characterized by having a plurality of heat dissipation holes 100. In one embodiment, the opening of the heat dissipation holes 100 is at least 0.5 mm, e.g., 1 mm or 1.2 mm, and the spacing between the plurality of heat dissipation holes 100 is at least 1 mm. The heat dissipation holes 100 extend downward from the upper surface of the protective layer 50 to the upper surface of the heat dissipation layer 30, completely exposing the heat dissipation layer 30. This allows heat collected by the heat dissipation layer 30 to be more quickly transferred to the outside via a path other than the second adhesive layer 40 and the protective layer 50 (i.e., the heat dissipation holes 100). The heat dissipation holes 100 can be formed, for example, by mechanical drilling or laser drilling. Note that for illustrative purposes, only three heat dissipation holes 100 are depicted in FIG. 1 . However, the actual number of heat dissipation holes 100 may be greater and is not specifically defined by the present disclosure.

[0019] 1, it should also be noted that the heat dissipation holes 100 penetrate the protective layer 50 and the second adhesive layer 40, and their bottoms are located on the upper surface of the heat dissipation layer 30, exposing the heat dissipation layer 30. Additionally, with regard to the shape of the heat dissipation holes of the present disclosure, reference can be made to the embodiment of FIG. 2, which depicts heat dissipation holes 102, 104, and 106 having three different depths.

[0020] 1 , the heat dissipation hole 102 in FIG. 2 is deeper and penetrates the heat dissipation layer 30, exposing the first adhesive layer 20. The bottom of the heat dissipation hole 102 is located on the top surface of the first adhesive layer 20. The heat dissipation hole 104 in FIG. 2 is deeper than the heat dissipation hole 100 in FIG. 1 , but does not penetrate the heat dissipation layer 30 like the heat dissipation hole 102. As shown, the bottom of the heat dissipation hole 104 is located within the heat dissipation layer 30 but does not yet expose the first adhesive layer 20. Compared to the prior art, both of the above-mentioned approaches allow the heat collected by the heat dissipation layer 30 to be more quickly transferred to the outside via a path other than the second adhesive layer 40 and the protective layer 50 (i.e., the heat dissipation hole 102 or the heat dissipation hole 104).

[0021] The heat dissipation holes 106 in FIG. 2 are shallower than the heat dissipation holes 100 in FIG. 1 . On the one hand, their bottoms do not reach the heat dissipation layer 30 and do not expose it. On the other hand, they are located lower than the underside of the protective layer 50 and are located within the second adhesive layer 40. Although the heat dissipation path for the heat dissipation layer 30 provided by the heat dissipation holes 106 passes through a small portion of the second adhesive layer 40, it avoids passing through the protective layer 50, which has poor thermal conductivity, thereby improving heat dissipation. However, to ensure effective heat dissipation, it is optimal to minimize the second adhesive layer 40 on the heat dissipation path. Preferably, the depth of the heat dissipation holes 106 into the second adhesive layer 40 may be greater than one-third of the total thickness of the second adhesive layer 40. That is, the bottom of the heat dissipation holes 106 is located lower than two-thirds of the total thickness of the second adhesive layer 40.

[0022] Reference is now made to FIG. 3, which illustrates a heat dissipation sheet 10 according to another embodiment of the present disclosure. Compared to the embodiment of FIG. 1, the heat dissipation sheet 10 of this embodiment differs primarily in that the multiple heat dissipation holes 100 of the heat dissipation sheet 10 are filled with a heat dissipation adhesive 60 having a thermal conductivity of less than 100 W / m·k and a viscosity of less than 25,000 Pa·s, thereby enhancing the heat dissipation effect of the heat dissipation holes 100 as heat dissipation paths. Preferably, the heat dissipation adhesive 60 may be a thermosetting sealing adhesive made of, for example, epoxy resin / silicone and metal oxide powder (or a mixture of other metals and non-metals).

[0023] Reference is now made to Fig. 4, which illustrates a heat dissipation sheet 10 according to another embodiment of the present disclosure. Compared with the embodiments of Figs. 1 and 3, the heat dissipation sheet 10 of this embodiment differs primarily in that the multiple heat dissipation holes 100 of the heat dissipation sheet 10 are further filled with a thermally conductive metal 70, thereby enhancing the heat dissipation effect of the heat dissipation holes 100 as heat dissipation paths. The thermally conductive metal 70 may be, for example, a copper paste, a silver paste, or a tin paste, and can be filled into the heat dissipation holes 100 by screen printing, electroplating, or sputtering.

[0024] Next, reference is made to FIG. 5 , which illustrates a heat dissipation sheet 10 according to another embodiment of the present disclosure. Compared to the embodiment of FIG. 1 , the heat dissipation sheet 10 of this embodiment differs primarily in that the heat dissipation sheet 10 further includes a heat diffusion layer 80 disposed between the heat dissipation layer 30 and the second adhesive layer 40. In this embodiment, the heat dissipation holes 100 extend downward from the upper surface of the protective layer 50 to the upper surface of the heat diffusion layer 80, exposing the heat diffusion layer 80. The function of the heat diffusion layer 80 is to serve as a thermal interface material to more quickly dissipate heat accumulated in the heat dissipation layer 30 to the outside. Preferably, the thermal conductivity of the heat diffusion layer 80 in the horizontal direction (X-axis and Y-axis) is at least 50% greater than the thermal conductivity of the heat diffusion layer 80 in the vertical direction (Z-axis). The heat diffusion layer 80 may be, for example, graphite having a thickness of approximately 50 μm.

[0025] Please refer to Fig. 6, which shows a heat dissipation sheet 10 according to another embodiment of the present disclosure. Compared with the embodiments of Figs. 1 and 5, the heat dissipation sheet 10 of this embodiment differs mainly in that a heat spreading layer 85 is disposed at the bottom of the heat dissipation holes 100. The heat spreading layer 85 may be formed from the material referenced for the heat spreading layer 80 in Fig. 5.

[0026] It should further be noted that the embodiment having the heat spreading layer 80 of Figure 5 may be supplemented with the thermal adhesive 60 of Figure 3, i.e., the embodiment shown in Figure 7. Similarly, the embodiment having the heat spreading layer 85 of Figure 6 may be supplemented with the thermal adhesive 60 of Figure 3, i.e., the embodiment shown in Figure 8.

[0027] On the other hand, the embodiment having the heat spreading layer 80 of Fig. 5 may be supplemented with the heat conductive metal 70 of Fig. 4, i.e., the embodiment shown in Fig. 9. Similarly, the embodiment having the heat spreading layer 85 of Fig. 6 may be supplemented with the heat conductive metal 70 of Fig. 4, i.e., the embodiment shown in Fig. 10.

[0028] 1 to 10, which show side views, Fig. 11 shows a top view of a heat-dissipating sheet 10 according to another embodiment. As shown in Fig. 11, the heat-dissipating sheet 10 has a substantially rectangular shape and a specific size that can be adjusted according to actual conditions. Since bending occurs mainly at the long sides of the rectangle, large stresses act on both sides of the long sides (i.e., at the positions of the short sides).

[0029] As shown in FIG. 11 , the heat dissipation sheet 10 has a plurality of heat dissipation holes 100 (or heat dissipation holes 102, 104, or 106) in FIG. 1 arranged in a linear array along the short edge of the heat dissipation sheet 10. The heat dissipation holes 100 have the effect of relieving stress because a portion of the structural material has been removed. Preferably, the shorter the distance D1 between the array formed by the heat dissipation holes 100 and one short edge of the heat dissipation sheet 10, the more effectively the stress can be relieved. Preferably, the distance D1 is less than 6 mm, for example, 6 mm, 3 mm, or 1 mm. In other embodiments, the distance D1 between the heat dissipation holes 100 and one short edge of the heat dissipation sheet 10 is less than 25% of the distance D2 between the short edge and the opposite short edge. For example, the distance D1 may be 10% or 25% of the distance D2. It should also be noted that, for purposes of illustration, Figure 11 depicts only two arrays, one on the left and one on the right, each having 5 x 1 heat dissipation holes 100. However, in other embodiments, a greater number of heat dissipation holes 100 (or heat dissipation holes 102, 104, or 106 in Figure 2) may be provided, arranged in other locations.

[0030] FIG. 12 illustrates an electronic device 3 according to one embodiment of the present disclosure. The electronic device 3 includes a flexible circuit board 1, a chip 2 disposed on the flexible circuit board 1, and a heat dissipation sheet 10. For details about the heat dissipation sheet 10, please refer to the descriptions related to FIGS. 1 to 11 above. The electronic device 3 may be, for example, a flat display, a wearable device, a mobile phone, a tablet computer, a laptop computer, an in-vehicle panel, or an industrial control panel, and the chip 2 may be, for example, a chip for driving an image display. As shown in FIG. 12, due to the small space within the electronic device 3, the circuit board 1 must be bent for use therein. Related details are well known to those skilled in the art and are therefore omitted herein. Furthermore, in embodiments not illustrated, the electronic device 3 is not necessarily a product for immediate use by an end user, but may be a semi-finished product requiring subsequent processing as long as the chip 2 is already disposed on the circuit board 1. In other embodiments not shown, the heat dissipation sheet 10 may be adhered to the back surface of the circuit board 1 (i.e., the surface on which the chip 2 is not located), and it should be further noted that the present disclosure is not particularly prescriptive in this regard.

[0031] The above description merely provides preferred embodiments of the present disclosure and should not be construed as limiting the scope of the claims of the present disclosure. All equivalent changes or modifications made without departing from the spirit disclosed by the present disclosure shall be encompassed within the scope of the appended claims.

Claims

1. A heat dissipation sheet that is adhered to a circuit board, a first adhesive layer adhered to the circuit board; a heat dissipation layer disposed on the first adhesive layer; a protective layer disposed on the heat dissipation layer; a plurality of heat dissipation holes extending downward from the upper surface of the protective layer; wherein the bottoms of the plurality of heat dissipation holes are not lower than the top surface of the first adhesive layer.

2. The heat dissipation sheet according to claim 1 , wherein the bottoms of the plurality of heat dissipation holes are located within the heat dissipation layer.

3. The heat dissipation sheet according to claim 1 , wherein the bottoms of the plurality of heat dissipation holes are not lower than the upper surface of the heat dissipation layer.

4. 4. The heat dissipation sheet of claim 3, further comprising a heat diffusion layer disposed between the heat dissipation layer and the protective layer, wherein the bottoms of the plurality of heat dissipation holes are not lower than the top surface of the heat diffusion layer, and the horizontal thermal conductivity of the heat diffusion layer is at least 50% greater than the vertical thermal conductivity of the heat diffusion layer.

5. The heat dissipation sheet of claim 1, further comprising a heat diffusion layer located at the bottom of the plurality of heat dissipation holes, wherein the horizontal thermal conductivity of the heat diffusion layer is at least 50% greater than the vertical thermal conductivity of the heat diffusion layer.

6. The heat dissipation sheet according to claim 1 , further comprising a second adhesive layer disposed between the heat dissipation layer and the protective layer, wherein the bottoms of the plurality of heat dissipation holes are lower than the lower surface of the protective layer.

7. The heat dissipation sheet according to claim 6 , wherein the bottoms of the plurality of heat dissipation holes are lower than a position two-thirds of the thickness of the second adhesive layer.

8. The heat dissipation sheet according to any one of claims 1 to 7, wherein the plurality of heat dissipation holes are further filled with a heat dissipation adhesive.

9. The heat dissipation sheet according to any one of claims 1 to 7, wherein the plurality of heat dissipation holes are further filled with a thermally conductive metal.

10. The heat dissipation sheet according to any one of claims 1 to 7, wherein the openings of the plurality of heat dissipation holes are at least 0.5 mm.

11. The heat dissipation sheet according to any one of claims 1 to 7, wherein the distance between the plurality of heat dissipation holes is at least 1 mm.

12. The heat dissipation sheet according to any one of claims 1 to 7, wherein the distance between the plurality of heat dissipation holes and the edge of the heat dissipation sheet is 6 mm or less.

13. The heat dissipation sheet according to any one of claims 1 to 7, wherein the heat dissipation sheet has two opposing edges, and the distance between the plurality of heat dissipation holes and one of the two edges is 25% or less of the distance between the two edges.

14. A heat dissipation sheet that is adhered to a circuit board, a first adhesive layer adhered to the circuit board; a heat dissipation layer disposed on the first adhesive layer; a protective layer disposed on the heat dissipation layer; a plurality of heat dissipation holes extending downward from the upper surface of the protective layer; wherein the heat dissipation sheet has two opposing edges, and the distance between the plurality of heat dissipation holes and one of the two edges is less than 25% of the distance between the two edges.

15. a substrate having a circuit layer; The heat dissipation sheet according to claim 1 or 14 adhered to the substrate. A circuit board comprising:

16. The circuit board according to claim 15; a chip disposed on the circuit board; An electronic device comprising:

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