Heating device for an aerosol generating device

Abstract

The heating device (100) for an aerosol generating device includes an insulation (102) including an inner wall (104) and an outer wall (106) spaced apart from each other, a cavity (110) capable of containing an aerosol-forming substance and disposed adjacent to the inner wall of the insulation, a heater (112) disposed within the insulation of the inner wall and configured to heat the aerosol-forming substance contained in the cavity by thermal conduction to generate an aerosol, and a first connection pad (114) disposed on the inner wall and configured to electrically connect the heater to a power source. The first connection pad is bonded to the outer and inner walls to seal the insulation, and the heater is disposed at a distance from the outer wall. The first connection pad at least partially covers the heater to provide a protective layer over the heater.

Description

[Technical field]

[0001] The present invention relates to a heating device for an aerosol generating device. In particular, the present invention relates to a heating device having vacuum insulation. [Background technology]

[0002] Heating devices for aerosol generating devices often have heaters that can be damaged during use or manufacturing, especially when these heaters are provided with vacuum insulation. Therefore, there is a demand for more robust heating devices. It is also desirable to make the aerosol generating device as efficient as possible to extend battery life and thus increase user convenience. The object of the present invention is to meet these demands. Summary of the Invention [Means for solving the problem]

[0003] According to a first aspect of the present invention, there is provided a heating device for an aerosol generating device, the heating device comprising: an insulating material including an inner wall and an outer wall separated from each other; a cavity capable of containing an aerosol-forming substance and arranged adjacent to the inner wall of the insulating material; a heater arranged inside the insulating material of the inner wall and configured to heat the aerosol-forming substance contained in the cavity by thermal conduction to generate an aerosol; and a first connection pad arranged on the inner wall and configured to electrically connect the heater to a power source, wherein the first connection pad is joined to the outer wall and inner wall to seal the insulating material, the heater is arranged at a distance from the outer wall, and the first connection pad at least partially covers the heater to provide a protective layer over the heater.

[0004] In this way, the first connection pad is "sandwiched" between the inner and outer walls. It has been found that sandwiching the first connection pad in this manner, rather than sandwiching the heater or other fragile electrical connections, is preferred as it avoids pressure and forces on the heater (or other elements) during use and manufacturing. Less force on the heater prevents damage. Thus, providing a separate connection pad at the junction of the inner and outer walls creates a more robust heating device that minimizes the chance of damage to critical and potentially fragile elements. Also, spacing the heater from the outer wall means that it only heats the required portion of the inner wall. Thus, heat can be more efficiently delivered to the aerosol generating material while minimizing heat lost by conduction through the outer wall. The first connection pad and heater can be provided as a single piece to form an electrical connection or in intimate contact with each other. The insulation can include any suitable insulating medium, for example a gas such as air, or a powdered or fibrous insulating material. In other embodiments, the insulation can encapsulate a vacuum. The inner and outer walls of the insulation may comprise a material that has a higher thermal conductivity than the insulating layer or material contained within the insulation to allow for heat transfer from the heater to the cavity.

[0005] Preferably, the inner and outer walls are separated by a vacuum such that the insulation is vacuum insulation, and the first connection pad is bonded to the outer and inner walls to seal the vacuum in the vacuum insulation. In this way, the connection pad is particularly effective because the tight joints required to seal vacuum insulation can require much more force than other types of insulation. Such forces can pose special risks to the heater during manufacture.

[0006] Preferably, the first connection pad is configured to provide increased mechanical robustness with respect to the heater. In this manner, the first connection pad can be resistant to damage during use or manufacturing while avoiding the need to change the heater's properties to increase its robustness. The first connection pad may comprise a metal such as stainless steel or copper. Other mechanically robust materials may also be used.

[0007] Preferably, the heater comprises an electrical resistive track printed or painted on the inner wall. In this way, heat can be transferred efficiently to the inner wall. The robustness of the heating device is significantly increased by providing a first connection pad at the junction of the inner and outer walls, since painted heating elements are particularly fragile. The resistive track can be provided on a specific portion of the inner wall, or it can be painted or printed on the inner wall so as to cover substantially the entire surface of the inner wall. The resistive track can follow a meandering or serpentine path on the inner wall from a first end of the track to a second end. In another example, the heater may comprise one or more resistive heating plates provided on the inner wall. The heating plates may also be provided as meandering or serpentine resistive tracks.

[0008] Preferably, the first connection pad is provided on the heater. In this manner, the heater and the connection pad can be easily electrically connected by covering the heater with the connection pad and attaching it to the inner wall, so that there is no need to electrically bond or solder the first connection pad and the heater to each other.

[0009] In some embodiments, the first connection pad covers substantially the entire heater. In this manner, the connection pad can act as a protective layer over the heater to reduce the possibility of damaging the heater. The first connection pad may cover the entire heater.

[0010] Preferably, the first connection pad has an electrical resistance smaller than that of the heater. More preferably, the first connection pad may have a resistance selected to generate a negligible amount of heat compared to the heater. In this way, the connection pad generates a substantially minimal amount of heat through the conduction of electricity that may be lost from the insulation through the outer wall. Thus, further energy loss is avoided, making the device more efficient.

[0011] Preferably, the heater and the first connection pad comprise different materials, in this way the mechanical robustness of the first connection pad can be optimized while the heater can be optimized in terms of both heating and efficiency.

[0012] Preferably, a second connection pad is provided on the inner wall, and the second connection pad is bonded to the inner and outer walls to seal the insulation. More preferably, the first and second connection pads are connected to different parts of the heater, each configured to connect to opposite terminals of a power source so that electrical current can be passed through the heater. In this way, both necessary electrical connections to the heater can be made using the connection pads rather than using parts of the heater, making the heating device more robust. The second connection pad may be configured to seal a vacuum in the vacuum insulation.

[0013] According to a second aspect of the present invention, there is provided an aerosol generating device comprising a heating device as described above.

[0014] Preferably, the aerosol generating device includes a controller configured to control the operation of the heater, and the first connection pad is electrically coupled to the controller. In this way, the first connection pad serves to increase the robustness of the heating device while also allowing the controller to control the heater. The first connection pad can be directly coupled to the controller or a circuit board, or can be coupled to the controller via one or more wires. In one example, the wires can be soldered to the first connection pad outside the insulation.

[0015] According to a third aspect of the present invention, there is provided a method of manufacturing a heating device as described above, comprising the steps of providing a heater on an inner wall, providing a first connection pad on the inner wall electrically connected to the heater, bonding the first connection pad to the inner wall and to the outer wall, and providing a protective layer over the heater by at least partially covering the heater with the first connection pad.

[0016] Suitably, in embodiments in which the heater comprises an electrically resistive track applied to the inner wall, providing the heater on the inner wall comprises applying an electrically resistive material to the inner wall.

[0017] Preferably, joining the first connection pad to the inner and outer walls includes welding the outer wall to the inner wall and the first connection pad. By welding the outer wall to the inner wall and the first connection pad, rather than to the heater, damage to the heater during the welding process can be avoided. In other embodiments, the outer and inner walls may be joined using a heat resistant sealant rather than welding.

[0018] Preferably, the welding comprises laser welding performed at least partially in a vacuum, in this manner sealing a vacuum within the insulation while the exterior and interior walls are being welded together.

[0019] Several embodiments of the present invention will now be described, by way of example only, with reference to the drawings in which: [Brief description of the drawings]

[0020] [Figure 1] 1 is a schematic perspective view of a portion of a heating apparatus according to one embodiment of the present invention; [Diagram 2] 1 is a schematic perspective view showing a portion of a heating device according to an embodiment of the present invention; [Diagram 3] 1 is a schematic cross-sectional view of a heating device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] FIG 1 shows a perspective view of a portion of a heating device for an aerosol generating device according to an embodiment of the present invention. A heating device 100 is provided and includes a vacuum insulation 102 including an inner wall 104 and an outer wall 106 radially spaced apart from one another such that a vacuum 108 is enclosed therebetween. FIG 1 shows the heating device 100 with the outer wall 106 removed so that the interior of the vacuum insulation 102 and the inner wall 104 are visible. FIG 2 shows a schematic perspective view of a portion of the heating device 100 and a schematic cross-sectional view of the outer wall 106 so that the inner wall 104 is visible.

[0022] The heating device 100 includes a cavity 110 disposed adjacent the interior wall 104 and configured to receive consumables including a tobacco rod and a filter held together by a tipping wrapper.

[0023] A consumable may be inserted into the cavity 110 by a user through an opening 111 into the cavity 110 and held in place by friction with the inner wall 104. A heater 112 is provided within the vacuum section 108 and on an outer surface of the inner wall 104. The heater 112 is configured to heat when an electric current is passed through it and to transfer the heat to the inner wall 104 by conduction. The inner surface of the inner wall 104 then heats the consumable and the air within the cavity 110 as the heat is transferred through the inner wall 104 by conduction. The heater 112 may be powered by a battery or any other power source provided in the aerosol generating device. The heater 112 includes a first end 113a electrically connected to a first connection pad 114 and a second end 113b electrically connected to a second connection pad 116. In the configuration shown in FIG. 1, the first end 113a of the heater 112 is provided below the first connection pad 114 so that an electrical connection is established. Similarly, the second end 113b of the heater 112 is disposed below the second connection pad 116. Each of the first connection pad 114 and the second connection pad 116 is configured to connect to opposite terminals of a battery disposed in the aerosol generating device so that an electric current can flow through the heater 112. Each of the first connection pad 114 and the second connection pad 116 is bonded to both the inner wall 104 and the outer wall 106 to seal the vacuum 108 in the vacuum insulation 102. During use, a user can draw air from the cavity 110 through the filter to deliver the aerosol generated in the cavity 110 to the user.

[0024] The vacuum insulation 102 is hollow and contains a vacuum 108 between a curved inner wall 104 and a curved outer wall 106. The vacuum insulation 102 is generally cylindrical so that the vacuum insulation 102 can enclose the entire consumable. The vacuum insulation 102 provides thermal insulation so that the heater can effectively heat the aerosol generating substrate while not heating other parts of the aerosol generating device, particularly the part of the aerosol generating device held by the user. The vacuum insulation 102 is elongated along its longitudinal axis so that it can accommodate elongated rod-shaped consumables, including cigarettes. The vacuum insulation 102 has a generally elliptical or circular cross-sectional shape when viewed along one end parallel to the longitudinal axis, although in other embodiments the vacuum insulation 102 can have other types of cross-sectional shapes, such as generally square or polygonal.

[0025] The vacuum insulation 102 has an opening 111 at one longitudinal end for accommodating consumables and is closed at the opposite end, so that when viewed perpendicular to its longitudinal axis, the vacuum insulation 102 has a cup-shaped cross-section as shown in Figures 1 and 2. In other embodiments, the vacuum insulation 102 may be open at both longitudinal ends so that it has a tubular cross-section when viewed perpendicular to its longitudinal axis.

[0026] In other embodiments, the vacuum insulation 102 may alternatively be a non-vacuum insulation, i.e., an insulation that includes an insulating medium such as air, fibrous or powdered insulation, etc. The inner wall 104 and the outer wall 106 may be joined by a first connection pad 114 and a second connection pad 116 to seal the insulating medium between the inner wall 104 and the outer wall 106.

[0027] The opening 111 flares outwardly to allow a user to easily insert a consumable into the cavity 110. In other embodiments, the opening 111 may not flare and the inner wall 104 may have the same cross-section along its entire longitudinal length.

[0028] 1 and 2, the inner wall 104 comprises stainless steel, but in other embodiments, the inner wall 104 may comprise other suitable materials having suitable properties for transferring heat from the heater 112 to the cavity 110, such as other metals, metal alloys, or ceramics.

[0029] The exterior wall 106 comprises stainless steel. In other embodiments, the exterior wall 106 may comprise other suitable materials, such as other metals or plastics. The exterior wall 106 comprises a single curved surface that is generally or entirely cylindrical. Other shapes of the exterior wall 106 may also be used in accordance with alternative configurations of vacuum insulation.

[0030] The thickness of the inner wall 104 is approximately 0.1 millimeters (mm) or less. The relatively small thickness reduces the thermal mass of the vacuum insulation 102 and increases the rate of thermal conductivity through the inner wall 104 to the cavity 110 and consumables. In particular, less heat is conducted away from the cavity 110 by the outer surface of the inner wall 104. A threshold of 0.1 mm or less has been found to be important in improving the energy efficiency of the heating device 100 through these mechanisms. In particular, an inner wall thickness of 0.1 mm has been found to provide a significant increase in thermal efficiency compared to an inner wall thickness of 0.25 mm.

[0031] The outer wall 106 has a thickness of about 0.25 mm, which may be preferable to a thickness of 0.1 mm to improve the mechanical robustness and insulating properties of the vacuum insulation 102 .

[0032] The cavity 110 is generally cylindrical and disposed immediately adjacent the inner wall 104. Preferably, the side of the inner wall 104 facing the cavity 110, i.e., the "inner surface" of the inner wall 104, is largely or completely free of additional elements to allow for direct contact with the inner surface when the consumable is contained within the cavity 110. In this manner, the efficiency of heat transfer from the inner wall 104 to the consumable is maximized. Furthermore, the absence of additional elements keeps the thermal mass of the heating device low, thereby reducing the time required to heat the tobacco to an aerosol-generating temperature.

[0033] In the embodiment of Figures 1 and 2, the heater 112 is a resistive heater configured to generate heat when an electric current is applied to it. The heater 112 includes a wire-wound resistive heating track that extends from a first end 113a to a second end 113b of the heater 112. The track follows a serpentine path along the length of the inner wall 104, as shown in Figures 1 and 2. The first end 113a and the second end 113b of the heater 112 are configured to electrically connect to first and second connection pads 114, 116, respectively. The heater 112 is longitudinally offset from the junction or seal of the inner wall 104 and the outer wall 106 to avoid damage to the heater 112 during assembly and use of the heating device 100.

[0034] The heater 112 is printed or painted on the exterior surface of the inner wall 104. In other embodiments, the heater 112 may include a heating element or plate disposed and attached on the inner wall 104. Thus, the heater 112 may provide "trace heating" to the cavity 110. The heater 112 may have a serpentine shape on the surface of the inner wall 104 such that substantially the entire length of the inner wall 104 is heated, as shown in Figures 1 and 2. In other embodiments, the heater 112 may cover substantially the entire circumference and / or area of ​​the inner wall 104.

[0035] The heater 112 may include materials that are susceptible to oxidation in the presence of oxygen and may be provided without an anti-oxidant coating, such that exposing the heater 112 to the vacuum 108 takes advantage of the absence of oxygen in the vacuum insulation 102, making the heater 112 cheaper and / or easier to manufacture.

[0036] A first connection pad 114 and a second connection pad 116 are provided as plates on the inner wall 104 and are located on the top of the heater 112 to allow electrical connection between each connection pad and the heater 112. The first and second connection pads 114, 116 are spaced apart to prevent short circuits and are provided at opposite ends of a track forming the heater 112. The first and second connection pads 114, 116 are sandwiched between and bonded to both the inner wall 104 and the outer wall 106, respectively. The first and second connection pads 114, 116 are curved to match the circumferential curvature of the inner wall 104.

[0037] 1 and 2, the first and second connection pads 114, 116 comprise stainless steel. The first and second connection pads 114, 116 are configured to be electrically conductive so that they can be used to provide power to the heater 112 while increasing the mechanical robustness of the device. In other embodiments, the first and second connection pads 114, 116 may comprise copper or other mechanically robust material configured to be electrically conductive.

[0038] Each of the first and second connection pads 114, 116 can extend through the joints or seals of the inner and outer walls 104, 106 to allow electrical connection to the first and second connection pads 114, 116 outside the vacuum insulation 102. The electrical connection can be made by wires soldered to the first and second connection pads 114, 116 configured to connect the heater 112 to a controller or battery in the aerosol generation device via the connection pads 114, 116. In other embodiments, the connection pads 114, 116 can extend directly to a battery or controller when the heating device 100 is in the aerosol generation device.

[0039] 1 and 2, a seal (not shown) is provided at the junction of the inner wall 104 and the outer wall 106 to prevent air from entering the vacuum insulation 102. The seal may comprise any suitable material, such as rubber, polyetheretherketone (PEEK), or metal. The inner wall 104 and the outer wall 106 may be welded together, in which case the seal may comprise a weld material.

[0040] The heating device 100 may be used with or provided in an aerosol generating device. The aerosol generating device may typically include a battery for powering the heater 112, a button or other input mechanism that allows a user to activate the heater 112, and a controller to control electronic components of the device, such as the heater 112. The heating device 100 may be provided within a housing of the aerosol generating device, the housing including an opening aligned with the opening 111 of the heating device 100. The aerosol generating device may be configured as an electronic smoking device.

[0041] The heating device 100 is configured for use with a consumable including tobacco and a filter, which may be held together by a tipping wrapper. The consumable may be in the form of a cylindrical rod, although other shapes of consumables designed to be received within the cavity 110 may be used. Other shapes of aerosol forming material may be used instead of or in addition to tobacco.

[0042] An example of the use of a heating device 100 as used in an aerosol generating device will now be described with reference to FIGS.

[0043] During use, a user may insert a consumable into cavity 110 through opening 111. The consumable may have a slightly smaller diameter than opening 111 so that the consumable can be initially received within cavity 110.

[0044] When the user is ready to begin vaporization, he or she can press a button on the aerosol generating device, after which the controller can cause current to flow from the battery to the heater 112 via the first connection pad 114 and the second connection pad 116. The heater 112 generates heat due to its own electrical resistance, which is transferred to the inner wall 104 by conduction and radiation. The resistance of the first connection pad 114 and the second connection pad 116 is low, so that the amount of heat generated due to the electrical current flowing therethrough is negligible. This increases the efficiency of the heating device 100 by minimizing the amount of unwanted heating of the outer wall 106.

[0045] While the heater 112 is operating, the vacuum 108 in the vacuum insulation 102 prevents heat from escaping by conduction from the cavity 110. The vacuum insulation 102 also prevents heat from escaping by convection, except through the openings 111. In this manner, the cavity 110, the heater 112, and the vacuum insulation 102 form a highly efficient heating oven that can heat the tobacco in the consumable to a desired aerosol-forming temperature. The controller may be configured to direct the heater 112 to heat the tobacco to a temperature below the combustion temperature of the tobacco. It may take several seconds for the cavity 110 to reach the aerosol-forming temperature.

[0046] The heater 112 is spaced from the exterior wall 106 such that there is no contact between the heater 112 and the exterior wall 106. This minimizes the amount of heat lost from the heating apparatus 100 after being transferred to the exterior wall 106.

[0047] As the tobacco heats, an aerosol is generated within cavity 110. The user can then inhale the aerosol by drawing air through the filter and into cavity 110. In this manner, air can be drawn into cavity 110 around the periphery of opening 111, allowing the user to continuously inhale aerosol from cavity 110.

[0048] The heater 112 is difficult to repair because it is located within the vacuum insulation 102. Therefore, to avoid damage to the potentially fragile heater 112 during assembly or manufacturing of the heating device 100, the first connection pad 114 and the second connection pad are bonded to the inner wall 104 and the outer wall 106 to seal the vacuum 108 within the vacuum insulation 102. This eliminates the need to place the outer wall 106 over the heater 112 and bond it to the inner wall 104, which could damage the heater 112. This configuration is particularly effective when using pre-painted heating tracks, which are particularly fragile.

[0049] The inner and outer walls 104, 106 may be welded to the first and second connection pads 114, 116. In one example, the inner and outer walls 104, 106 may be laser welded in a vacuum to create a vacuum inside the vacuum insulation 102. It is contemplated that other methods of joining the inner and outer walls 104, 106 to the first and second connection pads 114, 116 may also be implemented.

[0050] Alternatively, a sealant, such as a rubber sealant, may be provided to join the inner wall 104, the outer wall 106, and the first and second connection pads 114,116.

[0051] In other embodiments not shown, the first connection pad 114 and the second connection pad 116 may be disposed to cover all or nearly all of the heater 112, thereby providing a protective layer over the entire heater 112 to prevent damage during use. In this case, components of the heater 112 may be electrically isolated from the connection pads 114, 116 to avoid short circuits.

[0052] 3 shows a cross-sectional schematic diagram of a heating device 200 according to an alternative embodiment of the present invention. The heating device 200 includes a vacuum insulation 202 having an inner wall 204 and an outer wall 206 configured substantially similarly to the inner wall 104 and the outer wall 106 of the vacuum insulation 102. However, the vacuum insulation 202 differs from the vacuum insulation 102 in that the inner wall 204 includes a diverging opening 211. The opening 211 diverges radially outward from the center of the adjacent cavity 210 to facilitate the insertion of a rod-shaped consumable into the cavity 210. The inner wall 204 and the outer wall 206 are joined at the diverging region of the inner wall 204 as shown in FIG. 3.

[0053] A vacuum 208 is enclosed between the inner wall 204 and the outer wall 206, a cavity 210 is disposed adjacent to the inner wall 204, and a heater 212 is disposed in the inner wall 204. A seal 118 is disposed at the junction of the inner wall 204 and the outer wall 206. Each of these elements or aspects are constructed and operate similarly to corresponding features of the heating device 100.

[0054] The first and second connection pads 214, 216 are provided on the heater 212 at different ends of the heater track to allow current to flow through the heater 212, as described above. One end of the first and second connection pads 214, 216 are curved to match the circumferential curvature of the inner wall 204. These same ends are provided on the inner wall 204 in contact with the heater 212 to make electrical connection therewith, as shown in FIG. 3. The first and second connection pads 214, 216 differ from those of the heating device 100 in that they are outwardly flared to match the outwardly flared inner wall 204. This allows the first and second connection pads 214, 216 to be bonded to the inner and outer walls 204, 206 at the outwardly flared portions where the inner and outer walls 204, 206 are bonded to one another. As can also be seen in FIG. 3, the outwardly flared ends of the first and second connection pads 214, 216 are joined to and sandwiched between the inner wall 204, the outer wall 206, and the sealant 118 which prevents air from entering the vacuum insulation 202.

[0055] 3 illustrates the gap between the first and second connection pads 214, 216 and the inner wall 204. In other embodiments, the first and second connection pads 214, 216 can include a flared shape that more closely matches the flared shape of the inner wall 204. This allows the first and second connection pads 214, 216 to contact the inner wall 204 along the entire length of the first and second connection pads 214, 216.

[0056] In other respects, the first and second connection pads 214, 216 are configured and operate similarly to the first and second connection pads 114, 116 described above with reference to FIGS.

Claims

1. A heating device for an aerosol generating device, comprising: an insulation material including an inner wall and an outer wall separated from each other; a cavity capable of containing an aerosol-forming substance and disposed adjacent to an inner wall of the vacuum insulation material; a heater provided inside the insulating material of the inner wall and configured to heat an aerosol-forming substance contained in the cavity by thermal conduction to generate an aerosol; a first connection pad disposed on the inner wall and configured to electrically connect the heater to a power source; the first connection pad is bonded to the outer wall and the inner wall to seal the insulation, and the heater is spaced apart from the outer wall; A heating apparatus, wherein the first connection pad at least partially covers the heater to provide a protective layer over the heater.

2. 2. The heating device of claim 1, wherein the inner wall and the outer wall are separated by a vacuum such that the insulation is a vacuum insulation, and the first connection pad is bonded to the outer wall and the inner wall to seal the vacuum within the vacuum insulation.

3. 3. The heating device of claim 1 or 2, wherein the first connection pad is configured to have increased mechanical robustness with respect to the heater.

4. 4. A heating device according to claim 1, wherein the heater comprises an electrical resistive track printed or painted on the inner wall.

5. The heating device according to claim 1 , wherein the first connection pad covers substantially the entire heater.

6. 6. The heating device according to claim 1, wherein the first connection pad has an electrical resistance smaller than an electrical resistance of the heater.

7. The heating device of claim 1 , wherein the heater and the first connection pad comprise different materials.

8. 8. The heating device of claim 1, further comprising a second connection pad provided on the inner wall, the second connection pad being bonded to the inner wall and the outer wall to seal the insulation.

9. 9. The heating device of claim 8, wherein the first connection pad and the second connection pad are connected to different portions of the heater and each are configured to be connected to opposite terminals of a power source so that current can be passed through the heater.

10. An aerosol generating device comprising a heating device according to any one of claims 1 to 9.

11. The aerosol generating device of claim 10 , further comprising a controller configured to control operation of the heater, the first connection pad being electrically coupled to the controller.

12. A method for manufacturing the heating device according to any one of claims 1 to 9, comprising the steps of: providing the heater on the inner wall; providing the first connection pad on the inner wall for electrical connection to the heater; bonding the first connection pad to the inner wall and the outer wall; and at least partially covering the heater with the first connection pad to provide a protective layer over the heater.

13. The method of claim 12 , wherein the heater comprises an electrically resistive track applied to the inner wall, and providing the heater on the inner wall comprises applying an electrically resistive material to the inner wall.

14. The method of claim 12 or 13, wherein joining the first connection pad to the inner wall and the outer wall comprises welding the outer wall to the inner wall and to the first connection pad.

15. The method of claim 14 , wherein the welding comprises laser welding performed at least partially in a vacuum.

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