Phase change radio frequency switch
By employing a top-mounted heating structure in the phase-change RF switch, the problem of slow switching speed in GeTe phase-change switches is solved, achieving faster heat dissipation and higher isolation performance, thereby improving the dynamic performance and signal blocking capability of the switch.
Patent Information
- Application Number
- CN202520526972.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-25
- Publication Date
- 2026-02-27
- Estimated Expiration
- 2035-03-25
AI Technical Summary
Existing GeTe phase-change switches have slow switching speeds, resulting in poor isolation performance of the switching devices.
A top-mounted heating structure is adopted, placing the heating layer above the phase change layer. Heat is dissipated directly from the upper surface through a protective layer. The design includes a substrate, a substrate isolation layer, a phase change layer, a thermally conductive layer, a heating layer, and a protective layer. The heat dissipation path is optimized by utilizing the combination structure of the thermally conductive layer and the protective layer.
It significantly improves the switching speed and isolation performance of the switch, optimizes dynamic performance, reduces the possibility of signal leakage, and meets the high isolation requirements of high-frequency radio frequency applications.
Smart Images
Figure CN223957922U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model belongs to microwave switch device technical field, more specifically, it relates to a kind of phase change radio frequency switch. BACKGROUND
[0002] As a new type of microwave switch device, phase change switch utilizes the characteristics of material phase change, and the resistivity changes greatly when phase changes (transitions between crystalline state and amorphous state). The resistivity is low in crystalline state, and the resistivity is extremely high in amorphous state. The change value of switch state resistivity reaches five orders of magnitude, so that the switch control of microwave radio frequency circuit can be realized. It is a switch device with great application potential. In the phase change switch, the phase change material is mostly chalcogenide compounds such as GeTe, GST and GeSbTe. The phase change material can realize the transition between crystalline state and amorphous state by heating. When in crystalline state, the resistivity of the material is low, and the current can be conducted through the circuit. When the phase change material is in amorphous state, the resistivity is high, and the current cannot pass through, so as to realize the disconnection of the circuit.
[0003] Compared with traditional switches, phase change switch has the advantages of high on-off resistance ratio, low high-frequency conduction insertion loss, high off-state isolation, zero power consumption and easy integration, and has significant application value in the field of microwave, millimeter wave and terahertz radio frequency switches. Most of the current designs of GeTe phase change switch are four-port indirect heating structures. The lower two ports apply switching pulses to the heater, and the upper two ports connect the GeTe material to form a radio frequency path. The biggest disadvantage of this structure is that the heat cannot be quickly dissipated from the device structure, causing the switching speed of the device to be delayed and affecting the isolation performance of the switch device. UTILITY MODEL CONTENTS
[0004] The utility model aims at providing a kind of phase change radio frequency switch, to solve the problems of slow switching speed of existing GeTe phase change switch, leading to low isolation performance of switch device.
[0005] To achieve the above-mentioned purpose, the utility model adopts the technical scheme of:
[0006] A phase change radio frequency switch is provided, which includes a substrate, a substrate isolation layer, a phase change layer, a heat-conducting layer, a heating layer and a protective layer stacked from bottom to top. It also includes a radio frequency transmission layer between the substrate isolation layer and the heat-conducting layer. The radio frequency transmission layer is also attached to the outer edge of the phase change layer. The radio frequency transmission layer has a pressure point position outside the heat-conducting layer and the heating layer. The pressure point position is used for electrical connection with external devices. The protective layer has an avoidance hole corresponding to the pressure point position. The avoidance hole exposes the pressure point position to the outside.
[0007] In a possible implementation, the heating layer comprises a heating area and two connecting areas located on opposite sides of the heating area along a first path, the heating area is attached to the heat-conducting layer for heating the phase-change layer, the connecting areas are larger than the heating area in a second path, the second path is perpendicular to the first path, and the connecting areas are used for connecting with the pulse port.
[0008] In a possible implementation, the radio frequency transmission layer comprises a phase-change contact area and an electrode contact area distributed from inside to outside, the phase-change contact area is attached to the outer edge of the phase-change layer in the inside-outside direction and attached to the substrate isolation layer and the heat-conducting layer in the up-down direction, the electrode contact area is attached to the substrate isolation layer and the protection layer in the up-down direction, and the pressure point is located in the electrode contact area.
[0009] In a possible implementation, the phase-change contact area comprises a first contact part and a second contact part distributed from inside to outside, the first contact part is attached to the phase-change layer and the heat-conducting layer in the up-down direction, and the second contact part is attached to the outer edge of the phase-change layer in the inside-outside direction and attached to the heat-conducting layer and the substrate isolation layer in the up-down direction.
[0010] In a possible implementation, the heat-conducting layer comprises an aluminum nitride film and a silicon nitride film distributed from bottom to top, the silicon nitride film is attached to the heating layer, and the aluminum nitride film is attached to the phase-change layer.
[0011] In a possible implementation, the radio frequency transmission layer comprises two radio frequency transmission sheets distributed in mirror symmetry along the inside-outside direction, the two radio frequency transmission sheets are distributed in a spaced manner, and the inner ends of the radio frequency transmission sheets are attached to the phase-change layer.
[0012] In a possible implementation, the heat-conducting layer comprises a first heat-conducting area located between the two radio frequency transmission sheets and a second heat-conducting area located at the periphery of the first heat-conducting area, the bottom surface of the first heat-conducting area is attached to the phase-change layer, and the bottom surface of the second heat-conducting area is attached to the radio frequency transmission layer.
[0013] In a possible implementation, the substrate isolation layer comprises an isolation film and an adhesive film attached to the isolation film, the isolation film is attached to the substrate, and the adhesive film is bonded to the phase-change layer.
[0014] In a possible implementation, the protection layer comprises a protection main body and a protection flange connected to the periphery of the protection main body, the protection main body wraps the surfaces of the heating layer, the heat-conducting layer, the radio frequency transmission layer, and the phase-change layer, and the protection flange surrounds the outer edge of the radio frequency transmission layer.
[0015] In a possible implementation, the outer edge of the heat conduction layer protrudes outwardly from the heating layer.
[0016] The phase change radio frequency switch has the advantages that: compared with the prior art, the heating layer is arranged above the phase change layer to form a top heating structure, heat can be directly dissipated from the upper surface through the protective layer, and the heat dissipation efficiency of the device is greatly improved. This design enables the phase change layer to cool down faster when converting between the crystalline state and the amorphous state, thereby significantly improving the switching speed of the switch. Compared with the traditional built-in heater structure, the heat dissipation path of the phase change radio frequency switch is shorter, the thermal resistance is smaller, the accumulation of heat in the device is effectively avoided, and the dynamic performance of the switch is further optimized. In addition, due to the improvement of the heat dissipation efficiency, the phase change layer can reach a stable state more quickly during the state conversion process, reducing the possibility of signal leakage, thereby significantly improving the isolation performance of the switch. This improvement enables the switch to better block signals in high-frequency radio frequency applications, meeting the demand for high isolation. BRIEF DESCRIPTION OF DRAWINGS
[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.
[0018] Figure 1 The cross-sectional view of the phase change radio frequency switch provided by the embodiments of the present application is provided.
[0019] Figure 2 The top view of the phase change radio frequency switch provided by the embodiments of the present application is provided.
[0020] In the figure: 1, substrate; 2, substrate isolation layer; 201, isolation film; 202, adhesive film; 3, phase change layer; 4, heat conduction layer; 401, aluminum nitride film; 402, silicon nitride film; 5, heating layer; 501, heating area; 502, connecting area; 6, protective layer; 601, avoiding hole; 7, radio frequency transmission layer; 701, electrode contact area; 702, phase change contact area; 703, radio frequency transmission sheet. DETAILED DESCRIPTION
[0021] In order to make the technical problems, technical solutions and beneficial effects of the present application more clear, the following will further describe the present application in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.
[0022] In the claims, the specification, and the drawings of the present application, terms such as "first", "second", and "third" are used merely to distinguish one object or implementation from another, without necessarily implying a particular order or sequence. Unless otherwise specified, the orientation or position of the apparatus or elements, such as vertical, horizontal, clockwise, counterclockwise, and the like, is based on the orientation or position as shown in the drawings, and is merely for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the apparatus or elements must have a particular orientation or be constructed and operated in a particular orientation. Therefore, it cannot be understood as limiting the specific protection scope of the present application. In the claims, the specification, and the drawings of the present application, unless otherwise specified, the term "fixedly connected" or "fixedly connected" should be understood broadly, that is, any connection mode between the two without displacement relationship and relative rotation relationship, that is, it includes non-detachable fixed connection, detachable fixed connection, integration and fixed connection through other devices or elements. In the claims, the specification, and the drawings of the present application, the terms "include", "have" and their variants are intended to mean "contain but not limited to".
[0023] It should be noted that "inner" refers to the direction close to the center of the phase change radio frequency switch, and vice versa.
[0024] It should be noted that the protective layer is not shown in the drawings. Figure 2
[0025] Please refer to Figure 1 and Figure 2 , the phase change radio frequency switch provided by the present application will be described. The phase change radio frequency switch comprises a substrate 1, a substrate isolation layer 2, a phase change layer 3, a heat conduction layer 4, a heating layer 5 and a protective layer 6 distributed from bottom to top, and further comprises a radio frequency transmission layer 7 arranged between the substrate isolation layer 2 and the heat conduction layer 4. The radio frequency transmission layer 7 is also attached to the outer edge of the phase change layer 3. The radio frequency transmission layer 7 has a pressure point position located outside the heat conduction layer 4 and the heating layer 5. The pressure point position is used for electrical connection with external devices. The protective layer 6 is provided with a relief hole 601 corresponding to the pressure point position. The relief hole 601 exposes the pressure point position to the outside.
[0026] Compared with the prior art, the phase change radio frequency switch has the heating layer 5 arranged above the phase change layer 3, forms a top heating structure, heat can be directly dissipated from the upper surface through the protective layer 6, and the heat dissipation efficiency of the device is greatly improved. This design enables the phase change layer 3 to cool down faster when converting between the crystalline state and the amorphous state, thereby significantly improving the switching speed of the switch. Compared with the traditional built-in heater structure, the heat dissipation path of the utility model is shorter, the thermal resistance is smaller, the heat accumulation in the device is effectively avoided, and the dynamic performance of the switch is further optimized. In addition, due to the improvement of the heat dissipation efficiency, the phase change layer 3 can reach a stable state more quickly during the state conversion process, reducing the possibility of signal leakage, thereby significantly improving the isolation performance of the switch. This improvement enables the switch to better block signals in high-frequency radio frequency applications, meeting the demand for high isolation.
[0027] In some embodiments, referring to Figure 2 The heating layer 5 includes a heating area 501 and two connecting areas 502 located on the opposite sides of the heating area 501 along a first path, the heating area 501 is attached to the heat-conducting layer 4 and is used for heating the phase change layer 3, and the connecting areas 502 have a size greater than that of the heating area 501 along a second path perpendicular to the first path, and the connecting areas 502 are used for connecting with the pulse port.
[0028] The heating area 501 is attached to the heat-conducting layer 4 and focuses on heating the phase change layer 3, which can efficiently transfer heat to the phase change layer 3, ensure the stable and accurate occurrence of the phase change process, and provide a reliable thermal environment for the normal operation of related equipment. The connecting areas 502 have a size greater than that of the heating area 501 along a second path perpendicular to the first path, which greatly enhances the stability and reliability of the connection between the connecting areas 502 and the pulse port. A larger size means a larger contact area, which can effectively reduce the contact resistance and reduce energy loss during the transmission of pulse signals, thereby improving the working efficiency of the entire heating system. At the same time, this structural layout enables the heating layer 5 to have good connection performance while meeting the heating function, optimizes the overall integration of the equipment, and provides strong support for the miniaturization and high-efficiency design of the equipment, while improving the performance of the product, reducing the overall design and production cost.
[0029] Optionally, the connecting areas 502 are attached to the substrate isolation layer 2.
[0030] In some embodiments, referring to Figure 1 The radio frequency transmission layer 7 includes a phase change contact area 702 and an electrode contact area 701 distributed from inside to outside, the phase change contact area 702 is attached to the outer edge of the phase change layer 3 in the inside-out direction and is attached to the substrate isolation layer 2 and the heat-conducting layer 4 in the up-down direction, the electrode contact area 701 is attached to the substrate isolation layer 2 and the protective layer 6 in the up-down direction, and the pressure point is located in the electrode contact area 701.
[0031] The phase change contact region 702 closely adheres to the outer edge of the phase change layer 3 in the inner-outer direction, and adheres to the substrate isolation layer 2 and the heat conduction layer 4 in the up-down direction, and can efficiently and stably realize heat exchange and signal transmission between the phase change layer 3. Through such close adhesion, the state change of the phase change layer 3 can be quickly perceived and the related information can be accurately transmitted, and at the same time, the substrate isolation layer 2 and the heat conduction layer 4 are used to ensure that the signal transmission is not disturbed and the heat transfer efficiency is high, providing strong support for the accurate operation of the device. The electrode contact region 701 adheres to the substrate isolation layer 2 and the protective layer 6 in the up-down direction, greatly enhancing the structural stability and reliability of the entire radio frequency transmission layer 7. The substrate isolation layer 2 ensures electrical isolation between the electrode contact region 701 and the substrate 1, reducing signal crosstalk; the protective layer 6 plays a physical protection role for the electrode contact region 701, reducing the risk of damage caused by external factors, and prolonging the service life of the device.
[0032] In some embodiments, referring to Figure 1 , the phase change contact region 702 includes a first contact portion and a second contact portion distributed from inside to outside, the first contact portion adheres to the phase change layer 3 and the heat conduction layer 4 in the up-down direction, and the second contact portion adheres to the outer edge of the phase change layer 3 in the inner-outer direction, and adheres to the heat conduction layer 4 and the substrate isolation layer 2 in the up-down direction.
[0033] The first contact portion adheres to the phase change layer 3 and the heat conduction layer 4 in the up-down direction, enhancing the thermal coupling efficiency between the phase change layer 3 and the heat conduction layer 4, and helping to quickly conduct the heat generated in the phase change process, thereby improving the thermal stability and response speed of the device. The second contact portion adheres to the outer edge of the phase change layer 3 in the inner-outer direction, and adheres to the heat conduction layer 4 and the substrate isolation layer 2 in the up-down direction, which not only further expands the heat conduction path, but also enhances the mechanical stability and electrical contact performance between the phase change layer 3 and the radio frequency transmission layer 7, reduces the interface thermal resistance and contact resistance. In addition, by dividing the phase change contact region 702 into two parts, the distribution of heat flow and current can be more accurately controlled, avoiding local overheating or current concentration, thereby improving the reliability and service life of the device.
[0034] In some embodiments, referring to Figure 1 , the heat conduction layer 4 includes an aluminum nitride film 401 and a silicon nitride film 402 distributed from bottom to top, the silicon nitride film 402 adheres to the heating layer 5, and the aluminum nitride film 401 adheres to the phase change layer 3.
[0035] The aluminum nitride has excellent thermal conductivity, which can efficiently conduct the heat generated by the phase change layer 3 out, thereby effectively reducing the temperature gradient of the phase change layer 3 and improving the thermal response speed and stability of the device. The silicon nitride film 402 not only has good thermal conductivity, but also has excellent mechanical strength and insulation properties, which can effectively isolate the electrical interference between the heating layer 5 and the heat conduction layer 4, and enhance the mechanical stability of the overall structure. In addition, the combination of aluminum nitride and silicon nitride optimizes the heat conduction path, reduces the interface thermal resistance, and further improves the heat management capability of the device.
[0036] In some embodiments, referring to Figure 2 , the radio frequency transmission layer 7 includes two radio frequency transmission sheets 703 which are mirror-symmetrically distributed along the inner-outer direction, the two radio frequency transmission sheets 703 are spaced apart, and the inner ends of the radio frequency transmission sheets 703 are attached to the phase change layer 3.
[0037] The two radio frequency transmission sheets 703 are mirror-symmetrically distributed along the inner-outer direction, which can effectively balance the transmission path of the radio frequency signal, reduce the phase distortion and energy loss in the signal transmission process, and thereby improve the efficiency and accuracy of signal transmission. The two radio frequency transmission sheets 703 are spaced apart, which avoids mutual interference between signals and further improves the anti-interference capability and signal integrity of the radio frequency device. In addition, the inner ends of the radio frequency transmission sheets 703 are attached to the phase change layer 3, which enhances the electrical contact performance between the radio frequency transmission layer 7 and the phase change layer 3, reduces the contact resistance, and also helps to uniformly conduct heat, thereby improving the thermal stability of the device.
[0038] Specifically, the inner ends of the radio frequency transmission sheets 703 are attached to the heat conduction layer 4 and the substrate isolation layer 2 in the up-down direction, and the outer ends are attached to the protective layer 6 and the substrate isolation layer 2 in the up-down direction.
[0039] In some embodiments, referring to Figure 1 and Figure 2 , the heat conduction layer 4 includes a first heat conduction area arranged between the two radio frequency transmission sheets 703 and a second heat conduction area located at the periphery of the first heat conduction area, the bottom surface of the first heat conduction area is attached to the phase change layer 3, and the bottom surface of the second heat conduction area is attached to the radio frequency transmission layer 7.
[0040] The first heat conduction area is arranged between the two radio frequency transmission sheets 703, and its bottom surface is directly attached to the phase change layer 3, which can efficiently conduct the heat generated by the phase change layer 3 to the heat conduction layer 4, thereby rapidly reducing the temperature gradient of the phase change layer 3 and improving the thermal response speed and stability of the device. The second heat conduction area is located at the periphery of the first heat conduction area, and its bottom surface is attached to the radio frequency transmission layer 7, which not only expands the heat conduction path, but also enhances the heat management capability of the radio frequency transmission layer 7, thereby avoiding the occurrence of local overheating. In addition, through the partition design, the heat conduction layer 4 can more uniformly distribute heat, reduce thermal stress concentration, and thereby improve the reliability and service life of the device.
[0041] In some embodiments, referring to Figure 1 , the substrate isolation layer 2 includes an isolation film 201 attached to the substrate 1 and an adhesive film 202 attached to the phase change layer 3.
[0042] The adhesive film 202 is attached to the phase change layer, enhancing the bonding strength between the substrate isolation layer 2 and the phase change layer 3, avoiding interface peeling or structural failure caused by thermal expansion or mechanical stress. The isolation film 201 is attached to the substrate, effectively isolating the thermal conduction and electrical interference between the substrate 1 and other functional layers, thereby reducing heat loss and signal crosstalk, improving the thermal management efficiency and signal transmission quality of the device.
[0043] In some embodiments, referring to Figure 1 , the protective layer 6 includes a protective body and a protective flange connected to the outer periphery of the protective body, the protective body wrapping the surfaces of the heating layer 5, the thermal conductive layer 4, the radio frequency transmission layer 7, and the phase change layer 3, and the protective flange surrounding the outer edge of the radio frequency transmission layer 7.
[0044] The protective body wraps the surfaces of the heating layer 5, the thermal conductive layer 4, the radio frequency transmission layer 7, and the phase change layer 3, providing comprehensive physical protection for the internal core components, preventing external mechanical impact, vibration, or environmental factors (such as humidity, dust, etc.) from damaging the device performance. At the same time, the protective flange surrounds the outer edge of the radio frequency transmission layer 7, further enhancing the edge protection capability of the radio frequency transmission layer 7, avoiding damage to the edge area due to stress concentration or external interference. The overall design of the protective layer 6 can effectively isolate the internal components from the external environment, reduce electromagnetic interference and heat loss, thereby improving the signal transmission efficiency and thermal management performance of the device.
[0045] In some embodiments, referring to Figure 1 , the outer edge of the thermal conductive layer 4 is convex to the heating layer 5.
[0046] The design of the outer edge of the thermal conductive layer 4 being convex to the heating layer 5 can expand the contact area of the thermal conductive layer 4 with the surrounding environment, thereby more efficiently conducting the heat generated by the heating layer 5 to the outside, reducing the temperature gradient of the heating layer 5, and improving the thermal response speed and stability of the device. It also enhances the coverage of the thermal conductive layer 4 to the heating layer 5, optimizes the heat conduction path, reduces the local accumulation of heat, and avoids the occurrence of overheating. In addition, the convex design can also provide additional mechanical support for the heating layer 5, enhancing the stability of the overall structure and reducing deformation or damage caused by thermal expansion or mechanical stress.
[0047] The above merely describes preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, and improvement within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A phase change radio frequency switch, characterized by, The application relates to a substrate, a substrate isolation layer, a phase change layer, a heat conduction layer, a heating layer and a protective layer which are stacked from bottom to top, and a radio frequency transmission layer which is arranged between the substrate isolation layer and the heat conduction layer and is attached to the outer edge of the phase change layer, wherein the radio frequency transmission layer has a pressure point which is arranged outside the heat conduction layer and the heating layer and is used for electrical connection with external devices, and the protective layer is provided with a clearance hole corresponding to the pressure point, so that the pressure point is exposed to the outside.
2. The phase change radio frequency switch of claim 1, wherein, The heating layer comprises a heating area and two connecting areas which are arranged on the opposite sides of the heating area along a first path, the heating area is attached to the heat conduction layer and is used for heating the phase change layer, the connecting areas have a size larger than that of the heating area along a second path which is perpendicular to the first path, and the connecting areas are used for connection with pulse ports.
3. The phase change radio frequency switch of claim 1, wherein the first and second electrodes are formed of a material selected from the group consisting of: gold, silver, copper, aluminum, and combinations thereof. The radio frequency transmission layer comprises a phase change contact area and an electrode contact area which are arranged from inside to outside, the phase change contact area is attached to the outer edge of the phase change layer in the inside-outside direction and is attached to the substrate isolation layer and the heat conduction layer in the up-down direction, the electrode contact area is attached to the substrate isolation layer and the protective layer in the up-down direction, and the pressure point is arranged in the electrode contact area.
4. The phase change radio frequency switch of claim 3, wherein the first and second electrodes are formed of a material selected from the group consisting of: gold, silver, copper, aluminum, and combinations thereof. The phase change contact area comprises a first contact part and a second contact part which are arranged from inside to outside, the first contact part is attached to the phase change layer and the heat conduction layer in the up-down direction, and the second contact part is attached to the outer edge of the phase change layer in the inside-outside direction and is attached to the heat conduction layer and the substrate isolation layer in the up-down direction.
5. The phase transition radio frequency switch of claim 1, wherein the first and second electrodes are formed of a material selected from the group consisting of: gold, silver, copper, aluminum, and combinations thereof. The heat conduction layer comprises an aluminum nitride film and a silicon nitride film which are arranged from bottom to top, the silicon nitride film is attached to the heating layer, and the aluminum nitride film is attached to the phase change layer.
6. The phase transition radio frequency switch of claim 1, wherein, The radio frequency transmission layer comprises two radio frequency transmission sheets which are arranged in mirror symmetry along the inside-outside direction, the two radio frequency transmission sheets are arranged in a spaced manner, and the inner ends of the radio frequency transmission sheets are attached to the phase change layer.
7. The phase transition radio frequency switch of claim 6, wherein the first and second electrodes are formed of a material selected from the group consisting of: gold, silver, copper, aluminum, and combinations thereof. The heat conduction layer comprises a first heat conduction area which is arranged between the two radio frequency transmission sheets and a second heat conduction area which is arranged at the periphery of the first heat conduction area, the bottom surface of the first heat conduction area is attached to the phase change layer, and the bottom surface of the second heat conduction area is attached to the radio frequency transmission layer.
8. The phase transition radio frequency switch of claim 1, wherein, The substrate isolation layer comprises an isolation film and an adhesive film which is attached to the isolation film, the isolation film is attached to the substrate, and the adhesive film is attached to the phase change layer.
9. The phase transition radio frequency switch of claim 1, wherein, The protective layer comprises a protective main body and a protective flange which is connected to the periphery of the protective main body, the protective main body is wrapped around the surfaces of the heating layer, the heat conduction layer, the radio frequency transmission layer and the phase change layer, and the protective flange is arranged around the outer edge of the radio frequency transmission layer.
10. The phase transition radio frequency switch of claim 1, wherein, The outer edge of the heat conduction layer protrudes outwardly beyond the heating layer.