A flexible heat dissipation board and manufacturing method thereof

Abstract

The present invention discloses a heat dissipation flexible printed circuit board and a manufacturing method thereof, which includes at least two flexible printed circuit boards. Each flexible printed circuit board includes an upper cover layer, a lower cover layer, a core board layer disposed between the upper cover layer and the lower cover layer, and multiple columns of shape memory alloy strips arranged in the width direction of the core board layer. The shape memory alloy strips extend along the length direction of the core board layer. When the temperature of the shape memory alloy strips is lower than the transformation temperature, they are in an unfolded state, and when the temperature is higher than the transformation temperature, they return to a shape with continuous waveforms. The waveforms on the core board layers of each layer are consistent in the width direction, and the waveforms on the adjacent core board layers are staggered in the length direction to form several heat dissipation spaces between the flexible printed circuit boards. In the present invention, shape memory alloy strips are provided on the flexible printed circuit boards, and the memory characteristics of the shape memory alloy are used to generate heat dissipation spaces between adjacent flexible printed circuit boards, so that the heat generated by the flexible printed circuit boards can be effectively dissipated from the heat dissipation spaces, thereby improving the heat dissipation efficiency of the multi-layer flexible printed circuit board.

Description

Technical Field

[0001] The present invention relates to the field of PCB manufacturing, and particularly to a heat-dissipating flexible board and a manufacturing method thereof. Background Art

[0002] With the development of technology, electronic products tend to be thinner, more integrated and multifunctional. With the progress of society and the improvement of people's living standards, electronic products have become an indispensable item in people's lives. Among the basic components of electronic products, the circuit board plays a dominant role. A rigid-flex board is composed of a flexible circuit board and a rigid circuit board combined through processes such as lamination, forming a circuit board that simultaneously has the characteristics of a flexible printed circuit (FPC) and a printed circuit board (PCB). Since the rigid-flex board has both a certain flexible area and a certain rigid area, it has great advantages in saving internal space of products, reducing the volume of finished products, and improving product performance. However, while flexible boards are widely used, heat dissipation problems have also arisen.

[0003] The flexible board in the flexible board area is composed of an upper cover film layer, a core board layer and a lower cover film layer. For multi-layer flexible boards, overall lamination is often required, which means that during the manufacturing process of the flexible board, it shows a form of flat and close contact. Generally, especially for relatively wide flexible boards, due to the smooth and flat surface of the flexible boards, they cannot spontaneously separate from each other to provide more heat dissipation space due to vacuum pressure or electrostatic adsorption, resulting in difficult heat dissipation. Summary of the Invention

[0004] The purpose of the present invention is to provide a heat-dissipating flexible board and a manufacturing method thereof to solve one or more technical problems in the prior art, and at least provide a beneficial choice or create conditions.

[0005] The technical solutions adopted to solve the above technical problems are as follows:

[0006] The present invention provides a heat-dissipating flexible board, including at least two layers of flexible boards. Each layer of the flexible board includes an upper cover layer, a lower cover layer, a core board layer disposed between the upper cover layer and the lower cover layer, and multiple columns of shape memory alloy strips arranged in the width direction of the core board layer. The shape memory alloy strips extend along the length direction of the core board layer. The shape memory alloy strips are in an unfolded state when the temperature is lower than the transformation temperature, and return to the initial shape when the temperature is higher than the transformation temperature. The initial shape is set to have a continuous waveform. The waveforms on the core board layers of each layer are consistent in the width direction, and the waveforms on the core board layers of adjacent layers are staggered in the length direction to form several heat dissipation spaces between the flexible boards.

[0007] The beneficial effects of the present invention are as follows: Shape memory alloy strips are arranged on the flexible board. By utilizing the memory characteristics of the shape memory alloy, a heat dissipation space is generated between adjacent flexible boards, and the heat generated by the flexible board can be effectively dissipated from the heat dissipation space, thereby improving the heat dissipation efficiency of the multi-layer flexible board.

[0008] As a further improvement of the above technical solution, at least one row of shape memory alloy strips is arranged on each of the two side edges of the core board layer in the width direction to better realize the deformation of the flexible board.

[0009] As a further improvement of the above technical solution, preferably, the distance between two adjacent shape memory alloy strips is set to be 3 mm to 5 mm.

[0010] As a further improvement of the above technical solution, the initial shape is a continuous sine wave shape, or a rectangular wave shape, or a trapezoidal wave shape, or a triangular wave shape.

[0011] As a further improvement of the above technical solution, the trough of the shape memory alloy strip located in the upper layer is arranged opposite to the peak of the shape memory alloy strip located in the lower layer. In this way, the formed heat dissipation space is more stable, not easily collapsed and deformed, which is beneficial to better heat dissipation.

[0012] As a further improvement of the above technical solution, the shape memory alloy strip is arranged on the upper side or the lower side of the core board layer.

[0013] As a further improvement of the above technical solution, the shape memory alloy strip located at the middle position in the width direction can also penetrate through the core board layer in the height direction.

[0014] As a further improvement of the above technical solution, when using a flexible board with three or more layers, the deformation amount of the outer flexible board is set to be smaller than that of the inner flexible board.

[0015] In addition, the present invention also provides a manufacturing method for manufacturing the heat dissipation flexible board described in the above technical solution. The manufacturing method includes:

[0016] Manufacture a single-layer flexible board, provide the upper cover film layer, the core board layer, the lower cover film layer, and the shape memory alloy strip. Arrange the shape memory alloy strip along the length direction on the core board layer. The shape memory alloy strip is arranged in multiple rows in the width direction, and then cover the upper cover film layer and the lower cover film layer, and press them to form a single-layer flexible board. Among them, when the number of layers of the flexible board is three or more, the initial shape of the shape memory alloy strip is prepared according to the rule that the deformation amount of the outer flexible board is small and the deformation amount of the inner flexible board is large;

[0017] Press the multi-layer flexible board, provide a rigid board, stack the flexible boards in the order that the flexible board with a small amount of deformation is placed on the outside and the flexible board with a large amount of deformation is placed on the inside, and finally press the multi-layer flexible board and the rigid board together.

[0018] As a further improvement of the above technical solution, a deformation allowance is reserved for the flexible board so that the flexible board will not pull on the rigid boards at both ends after deformation. Brief Description of the Drawings

[0019] The present invention will be further described below with reference to the drawings and embodiments;

[0020] Figure 1 It is a schematic structural diagram of the rigid-flex board of Embodiment 1 of the present invention;

[0021] Figure 2 It is a schematic diagram of the laminated structure of the heat dissipation flexible board of Embodiment 1 of the present invention;

[0022] Figure 3 It is a schematic exploded view of the single-layer flexible board of Embodiment 1 of the present invention;

[0023] Figure 4 is Figure 1 The top view of the flexible board in

[0024] Figure 5 It is an example diagram of the initial shape of the shape memory alloy strip of Embodiment 1 of the present invention;

[0025] Figure 6 It is a schematic diagram of the deformed structure of Embodiment 1 of the present invention;

[0026] Figure 7 It is another schematic diagram of the deformed structure of Embodiment 1 of the present invention;

[0027] Figure 8(a) is a symmetric arrangement pattern of the shape memory alloy strips of the embodiment of the present invention;

[0028] Figure 8(b) is a staggered arrangement pattern of the shape memory alloy strips of the embodiment of the present invention;

[0029] Figure 8(c) is another staggered arrangement pattern of the shape memory alloy strips of the embodiment of the present invention;

[0030] Figure 8(d) is a complementary arrangement pattern of the shape memory alloy strips of the embodiment of the present invention;

[0031] Figure 9 It is a schematic cross-sectional view of the single-layer flexible board in the width direction of Embodiment 1 of the present invention;

[0032] Figure 10 It is a schematic diagram of the deformed structure of the heat dissipation flexible board of Embodiment 2 of the present invention;

[0033] Figure 11 It is a schematic diagram of the deformed structure of the heat dissipation flexible board of other embodiments of the present invention. Specific Embodiments

[0034] This part will describe the specific embodiments of the present invention in detail. The preferred embodiments of the present invention are shown in the accompanying drawings. The function of the drawings is to supplement the description in the text part of the specification, enabling people to intuitively and vividly understand each technical feature and the overall technical solution of the present invention. However, it should not be construed as a limitation on the protection scope of the present invention.

[0035] In the description of the present invention, it should be understood that for the orientation description, such as the upper, lower, front, rear, left, right, etc., the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the present invention.

[0036] In the description of the present invention, "greater than", "less than", "exceeding", etc. are understood as not including the present number, and "above", "below", "within", etc. are understood as including the present number. If there is a description of the first and the second, it is only for the purpose of distinguishing technical features and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0037] In the description of the present invention, unless otherwise clearly defined, words such as "set", "installed", "connected", etc. should be understood in a broad sense. Those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0038] Embodiment 1:

[0039] Refer to Figures 1 to 7 to describe the heat dissipation flexible board of the embodiment of the present invention. Figure 1 As shown, it is a rigid-flexible printed circuit board, including a flexible board 10 and a rigid board 20. The rigid board 20 is laminated at both ends of the flexible board 10. The flexible board 10 includes a first flexible board 11 and a second flexible board 12 laminated together. When the flexible board 10 is laminated with the rigid board 20, the first flexible board 11 and the second flexible board 12 are only relatively closely attached to each other without an adhesive layer. Therefore, the first flexible board 11 and the second flexible board 12 can be separated from each other.

[0040] The first flexible plate 11 includes a first upper cover layer 100, a first lower cover layer 200, a first core board layer 300, and a first shape memory alloy strip 400. The first core board layer 300 and the first shape memory alloy strip 400 are disposed between the first upper cover layer 100 and the first lower cover layer 200, and the first shape memory alloy strip 400 is disposed on the first core board layer 300. Specifically, a plurality of first shape memory alloy strips 400 are arranged in the width direction of the first core board layer 300, and the first shape memory alloy strips 400 extend along the length direction of the first core board layer 300.

[0041] The second flexible plate 12 includes a second upper cover layer 110, a second lower cover layer 210, a second core board layer 310, and a second shape memory alloy strip 410. The second core board layer 310 and the second shape memory alloy strip 400 are disposed between the second upper cover layer 100 and the second lower cover layer 200, the second shape memory alloy strip 410 is disposed on the second core board layer 310, and the arrangement of the second shape memory alloy strip 410 on the second core board layer 310 is the same as the arrangement of the first shape memory alloy strip 400 on the first core board layer 300.

[0042] A shape memory alloy strip is a material composed of two or more metal elements that has a shape memory effect through thermoelasticity and martensitic phase transformation and its reverse transformation. Shape memory alloys have excellent shape memory performance. When the shape memory alloy reaches above the transformation temperature, it is processed into a certain shape, such as a bent shape. Then it is cooled below the transformation temperature, its shape is artificially changed, and then it is heated above the transformation temperature, and the shape memory alloy will automatically return to the original bent shape processed above the transformation temperature.

[0043] In this embodiment, the shape memory alloy is a nickel-titanium alloy. When the shape memory alloy strip reaches above the transformation temperature, it is processed into a shape with a continuous waveform as the initial shape of the shape memory alloy strip. The continuous waveform is a waveform shape formed by connecting the heads and tails of several repeated waveforms. Refer to Figure 5 For example, it can be formed by connecting sine waves or rectangular waves end to end. In this embodiment, the initial shape of the shape memory alloy strip is preferably a continuous waveform shape composed of sine waves. When the temperature is higher than the transformation temperature, the shape memory alloy strip is in a continuous waveform shape. When the temperature is lower than the transformation temperature, the shape memory alloy strip is an unfolded strip without corrugations.

[0044] It can be understood that the shape memory alloy strip can also use shape memory alloys of other materials as long as the shape memory function can be achieved.

[0045] Since the shape memory alloy strips are provided on the core board layer, when the upper cover layer, the lower cover layer, the core board layer, and the shape memory alloy strips are pressed together to form a flexible board, when the temperature of the shape memory alloy strips is higher than the transition temperature and returns to the initial state of the continuous waveform shape, the entire flexible board will be forced to deform according to the shape of the memory alloy strips to form a consistent shape.

[0046] The waveforms on the first flexible board 11 and the waveforms on the second flexible board 12 are staggered with each other in the length direction of the core board layer, so as to form a heat dissipation space between the waveforms of different layers. Refer to 6. Figure 7 , the waveforms being staggered means that the trough of the first shape memory alloy strip 400 and the peak of the second shape memory alloy strip 410 at least partially abut against each other. There should be no superposition of the peaks and peaks, or the troughs and troughs of the upper and lower layers, because in this case, the above-mentioned heat dissipation space will not appear, affecting the heat dissipation effect; in addition, the waveforms on the first flexible board 11 are consistent in the width direction of the core board layer, and the waveforms on the second flexible board 12 are consistent in the width direction of the core board layer. In this way, when the flexible board dissipates heat, the upper and lower flexible boards deform to form several heat dissipation spaces, increasing the contact area between the flexible board and the air, and the heat dissipation spaces penetrate in the width direction. Therefore, the heat generated by the flexible board can be effectively dissipated from the heat dissipation spaces, thereby improving the heat dissipation efficiency of the multi-layer flexible board. In this embodiment, preferably, the trough of the first shape memory alloy strip 400 and the peak of the second shape memory alloy strip 410 are directly opposite and abut against each other. For example Figure 6 as shown in the arrangement, the heat dissipation space formed in this way is more stable, not easily collapsed and deformed, which is beneficial to better heat dissipation.

[0047] The shape memory alloy strips can be arranged in a whole piece along the length direction of the core board layer according to the actual situation, or multiple strips can be arranged discontinuously along the length direction. When the shape memory alloy strips are arranged in a whole piece, the overall control effect on the heat dissipation channels is better. However, there are also some situations where the shape memory alloy strips need to be arranged discontinuously. For example, when the local position of the flexible board is restricted by the surrounding space and there is not enough deformation space, such as when there are other devices with a relatively close distance around the flexible board, then the shape memory alloy strips may not be arranged at the positions restricted by space on the core board layer, that is, the shape memory alloy strips are discontinuously arranged along the length direction of the core board layer; or, the circuit pattern on the core board layer is irregular, and when the shape memory alloy strips intersect with the circuit pattern in the length direction, the shape memory alloy strips are locally interrupted at the intersection positions, so as not to affect the setting of the circuit pattern and the transmission of signals; or, the flexible board is relatively long, with a high heat dissipation temperature in the middle and a low heat dissipation temperature at both ends. Different shape memory alloy strips with different transformation temperatures can be set for different heat dissipation temperature regions, that is, shape memory alloy strips made of different materials are discontinuously arranged along the length direction of the core board layer; or, the shape memory alloy strips are discontinuously arranged in the local stress concentration area to prevent the flexible board from cracking due to fatigue failure after multiple deformations in the stress concentration area.

[0048] The wider the core board layer is, the more shape memory alloy strips are correspondingly arranged in the width direction. Preferably, at least one row of shape memory alloy strips is arranged at each of the two side edges in the width direction to better realize the deformation of the flexible board. More preferably, the adjacent two shape memory alloy strips are arranged at an interval of 3 mm to 5 mm. Refer to Figure 4 When the width of the core board layer is relatively large, the number of shape memory alloy strips can be increased at an interval of 3 mm to 5 mm between the shape memory alloy strips on both its side edges.

[0049] In this embodiment, there is no limitation on the specific arrangement pattern of the shape memory alloy strips on the core board layer. Each row of shape memory alloy strips is arranged in a whole piece or discontinuously along the length direction, and multiple arrangement patterns can be formed by several rows of shape memory alloy strips on the core board layer, such as the symmetric pattern, the staggered pattern, and the complementary pattern shown in FIGS. 8(a)-8(d).

[0050] In addition, refer to Figure 9 Taking the first flexible board 11 as an example, the first shape memory alloy strip 400 can be arranged on the upper side or the lower side of the core board layer 300. The shape memory alloy strip 401 located at the middle position in the width direction of the core board layer can also penetrate through the core board layer in the height direction. Specifically, the left core board 301, the third shape memory alloy strip 401, and the right core board 302 are assembled together to form a complete core board layer.

[0051] Embodiment 2:

[0052] The difference between Example 2 and Example 1 is that the flexible board 10 in Example 2 includes three layers of flexible boards. Refer to Figure 10 , two first flexible boards 11 are located in the outer layers on both sides, and the second flexible board 12 is located in the middle layer. In order to facilitate the stacking and placement of the flexible boards, the lengths of the first flexible board 11 and the second flexible board 12 in the unfolded state are the same. Of course, in some other embodiments, the lengths can also be set to be different. The deformation amount of the first shape memory alloy strip 400 on the first flexible board 11 located in the outer layer is set to be less than the deformation amount of the second shape memory alloy strip 410 on the second flexible board 12 located in the middle layer. Here, it should be noted that the deformation amount refers to the difference in length between the shape memory alloy strip in the unfolded state and in the initial state. Since the distance between the rigid boards 20 at both ends of the flexible-rigid combined board is fixed when in use, in order for the flexible board to have sufficient deformation space, it can be understood that when the second flexible board 12 in the middle layer deforms, the appearance of the waveform causes the size of the second flexible board 12 to increase in the width direction of the core board layer. Therefore, the first flexible board 11 in the outer layer needs to be generally formed into a shape arched outward to provide a space that can accommodate the initial shape of the second flexible board 12. Therefore, when the deformation amount of the first flexible board 11 in the outer layer is less than the deformation amount of the second flexible board 12 in the middle layer, such an accommodating space can be provided.

[0053] It can be understood that when the flexible board 10 includes more than three layers of flexible boards, the setting principle in Example 2 is applicable, that is, the deformation amount of the flexible board in the outer layer is less than the deformation amount of the flexible board in the inner layer. Refer to Figure 11 , two first flexible boards 11 are respectively located in the outer layers on both sides, and two second flexible boards 12 are located in the middle layer. The deformation amount of the first shape memory alloy strip 400 on the first flexible board 11 located in the outer layer is set to be less than the deformation amount of the second shape memory alloy strip 410 on the second flexible board 12 located in the middle layer.

[0054] In addition, the above embodiments also provide a manufacturing method for a heat-dissipating flexible board:

[0055] Manufacture a single-layer flexible board, provide an upper cover film layer, a core board layer, a lower cover film layer, and shape memory alloy strips. Arrange the shape memory alloy strips along the length direction on the core board layer. The shape memory alloy strips can be arranged in multiple columns in the width direction of the core board layer, and then cover the upper cover film layer and the lower cover film layer, and press to form a single-layer flexible board; among them, when the number of layers of the flexible board is more than three, the initial shape of the shape memory alloy strip is prepared according to the rule that the outer flexible board has a small deformation amount and the inner flexible board has a large deformation amount.

[0056] Press multiple layers of flexible boards, provide rigid boards, stack them in the order that the flexible board with a small deformation amount is placed in the outer layer and the flexible board with a large deformation amount is placed in the inner layer, and finally press the multiple layers of flexible boards and the rigid boards together.

[0057] Since the length of the flexible plate will become smaller after contraction, and the relative distance between the rigid plates at both ends of the flexible plate will not change, therefore, when preparing the flexible plate, sufficient deformation allowance should be reserved for the flexible plate. The deformation allowance reserved for the flexible plate is greater than or equal to the deformation amount of the flexible plate caused by the deformation of the shape memory alloy strip, that is, the length of the flexible plate will not pull on the rigid plates at both ends after deformation.

[0058] The above has specifically described the preferred embodiments of the present invention, but the present invention is not limited to the described embodiments. Those skilled in the art can also make various equivalent variations or substitutions without departing from the spirit of the present invention, and these equivalent variations or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A heat dissipation flexible printed circuit board, characterized in that: It includes at least two layers of flexible plates. Each layer of the flexible plate includes an upper cover layer, a lower cover layer, a core board layer disposed between the upper cover layer and the lower cover layer, and multiple columns of shape memory alloy strips arranged in the width direction of the core board layer. The shape memory alloy strips extend along the length direction of the core board layer. When the temperature of the shape memory alloy strips is lower than the transformation temperature, they are in an unfolded state, and when the temperature is higher than the transformation temperature, they return to the initial shape. The initial shape is set to a shape with continuous waveforms. The waveforms on the core board layers of each layer are consistent in the width direction, and the waveforms on the core board layers of adjacent layers are staggered in the length direction to form several heat dissipation spaces between the flexible plates. The waveforms being staggered means that at least part of the troughs and peaks of the waveforms on the core board layers of adjacent layers are in contact with each other, and the peaks of adjacent layers do not overlap, and the troughs of adjacent layers do not overlap.

2. The heat dissipation flexible board according to claim 1, wherein: At least one column of shape memory alloy strips is arranged on each of the two side edges of the core board layer in the width direction.

3. The heat dissipation flexible board according to claim 1, wherein: Adjacent two of the shape memory alloy strips are arranged with a spacing of 3 mm to 5 mm.

4. The heat dissipation flexible printed circuit board according to claim 1, wherein: The initial shape is a continuous sine waveform, or a rectangular waveform, or a trapezoidal waveform, or a triangular waveform.

5. The heat dissipation flexible printed circuit board according to claim 4, wherein: The troughs of the shape memory alloy strips in the upper layer are arranged opposite to the peaks of the shape memory alloy strips in the lower layer.

6. The heat dissipation flexible board according to claim 1, wherein: The shape memory alloy strips are arranged on the upper side or the lower side of the core board layer.

7. The heat dissipation flexible printed circuit board according to claim 6, wherein: The shape memory alloy strip located at the middle position in the width direction penetrates through the core board layer in the height direction.

8. The heat dissipation flexible board according to claim 1, wherein: When more than three layers of flexible plates are used, the deformation amount of the outer flexible plate is set to be smaller than that of the inner flexible plate. The deformation amount refers to the length difference between the shape memory alloy strip in the unfolded state and in the initial state.

9. A manufacturing method of a heat dissipation flexible printed circuit board, characterized in that, For manufacturing the heat dissipation flexible plate according to any one of claims 1 to 8, the manufacturing method includes: Manufacturing a single-layer flexible plate, providing the upper cover film layer, the core board layer, the lower cover film layer, and the shape memory alloy strips, arranging the shape memory alloy strips along the length direction on the core board layer, arranging multiple columns of the shape memory alloy strips in the width direction, and then covering the upper cover film layer and the lower cover film layer and pressing them together to form a single-layer flexible plate. Among them, when the number of layers of the flexible plate is more than three, the initial shape of the shape memory alloy strips is prepared according to the rule that the outer flexible plate has a smaller deformation amount and the inner flexible plate has a larger deformation amount. Pressing multiple layers of flexible plates, providing a hard board, stacking them in the order that the flexible plate with a smaller deformation amount is placed on the outside and the flexible plate with a larger deformation amount is placed on the inside, and finally pressing the multiple layers of flexible plates and the hard board together.

10. The manufacturing method of a heat dissipation flexible printed circuit board according to claim 9, characterized in that, The flexible plate reserves a deformation margin so that the flexible plate will not pull the hard boards at both ends after deformation.

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