Thermal Lens Electrodes in Thermoelectric Generators for Performance Improvement

Abstract

To provide a thermal lensing electrode in thermoelectric generators for improved performance.SOLUTION: Exemplary thermoelectric devices and methods are disclosed herein. Thermoelectric generator performance is increased by forming isothermal fields within the bulk of a thermoelectric pellet, resulting in an increase in power output of a thermoelectric generator module. In one embodiment, a thermoelectric device includes a pellet comprising a semiconductor material, a first metal layer surrounding a first portion of the pellet, and a second metal layer surrounding a second portion of the pellet. The first and second metal layers are configured to be proximate to one another about a perimeter of the pellet. The pellet is exposed at the perimeter. In addition, the perimeter is configured at a sidewall height about the pellet to provide a non-linear effect on a power output of the thermoelectric device by modifying an isotherm surface curvature within the pellet. The device also includes a metal container thermally and electrically bonded to the pellet.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Related Applications This application claims priority under 35 U.S.C. 119(e) to U.S. Provisional Patent Application No. 62 / 768,679, filed on Nov. 16, 2018, entitled “Advantages of Thermal Concentration in Thermoelectric Devices for Performance Improvement,” the disclosure of which is incorporated herein by reference in its entirety.

[0002] Embodiments of the present specification generally relate to thermoelectric devices made from semiconductor components. More specifically, these embodiments relate to design improvements regarding the nature of electrodes in direct contact with semiconductor pellets that result in an increase in the power output of thermoelectric generators.

Background Art

[0003] Thermoelectric modules have been the subject of alternative power generation research for decades and are present in the space of thermoelectric generators where several products are used as power sources from waste heat. Thermoelectric modules can be used for alternative power generation in the Seebeck mode to convert heat flux into electrical flux. Conversely, in the Peltier mode, electrical flux can be used to drive heat flux to provide cooling. Otherwise, waste heat, which would otherwise be lost to the environment, can be recycled into electrical energy for use remotely or fed back into the electrical grid via an inverter, so thermoelectric devices for power generation are one of the important driving forces for research.

[0004] However, this approach to power generation encounters barriers in terms of cost per watt, which is a fundamental parameter, when compared to other methods in alternative power generation such as solar power generation technology. The main reasons for this cost barrier lie in the thermoelectric properties of the semiconductors within the device and the manufacturing costs of the heat exchanger system that provides the high and low temperature surfaces required for the conversion of thermal energy into electrical energy. Therefore, if thermoelectric energy production methods are to be present everywhere and progress on a larger power scale in the production of clean energy conversion, especially above the megawatt power range, progress in every aspect of manufacturing thermoelectric generators (TEGs) is essential.

Summary of the Invention

Means for Solving the Problems

[0005] The systems and methods presented herein provide a cost - efficient approach to large - scale production of clean energy by utilizing more area of the semiconductor surface and pellet volume of the thermoelectric pellets. In one embodiment, a new type of electronic component is proposed for improving the performance of thermoelectric generators using a favorable match of electrical and thermal properties. One way to construct a thermoelectric module (e.g., operating in the Seebeck mode and / or the Peltier mode) is based on sequential layer assembly using automated techniques such as robotic placement of components having a pick - and - place device. The thermoelectric module can be fabricated in this way for mass production.

[0006] In one embodiment, the TEG is generally configured as a semiconductor including a shape such as a cuboid or a cylinder, but the shape can be any shape that enables a heat concentration effect, such as a rectangular parallel pipe, a sphere, a frustum of a cone, or other such polyhedra, which can direct thermal energy using the corners and vertices of adjacent side surfaces of the semiconductor pellet. Two metal electrodes are used to electrically and thermally join each pellet to the electrical interconnection to form a series circuit and allow a current generated by the thermoelectric effect in the presence of a thermal gradient to flow. Thus, an array of pellets arranged in such a manner can be packaged to form a module, typically a flat package.

[0007] Generally, two flat metal electrodes of the pellet are placed on directly opposing parallel surfaces of the pellet and are conveniently attached to the interconnection by printing a solder paste on the interconnection. The solder may then be reflowed to complete the joining process between the components. More specifically, this embodiment relates to a design improvement regarding the geometric properties of the electrodes closely coupled to the pellet, which results in an increase in the overall performance of the thermoelectric device through the concentration of thermal energy within the bulk of the pellet. The power output of the TEG can be significantly increased from the nature of the isothermal contours within the pellet.

[0008] The components of the thermoelectric effect are pellets of semiconductor material in which the material has appropriate thermoelectric properties according to their dopants. Usually, for the fabrication of a thermoelectric device, two types of materials are required, one having electrons as majority charge carriers (N-type) and the other having holes as majority charge carriers (P-type). Typically, each pellet has a cuboid shape and has two opposing planar electrodes, one hot and one cold, on parallel planes on two surfaces of the pellet for heat and current injection on the hot side in a standard circuit layout. Thus, the isotherms generated in the pellet volume between the hot and cold electrodes of the pellet are planar and parallel to the electrodes. Thus, the heat gradient vector perpendicular to the isotherms within the pellet is parallel to the plane of the sidewalls of each pellet from the top to the bottom of the pellet, and the vector of the current generated through the thermoelectric effect is generally parallel to the heat gradient vector in the bulk of each pellet. Such a geometric arrangement fixes the area of the isotherms to that of the area of the electrodes of the pellet.

[0009] Collectively, the current between the pellets within the module is connected in series by arranging planar electrical interconnections at the bottom and upper half of the package to provide heat transfer and conductivity. The electrical interconnections, typically copper, provide the output electrodes of the module. Thus, the layout of the thermoelectric module has a device shape convenient for surface mount technology methods.

[0010] Furthermore, the pellets are typically cuboid in shape because they are a space-filling shape, unlike cylindrical pellets. The higher the packing density of the active thermoelectric pellets, generally, the more active volume exists in the module for converting heat into electrical energy in the generator and / or providing active cooling in the Peltier mode. In this specification, a cuboid is called a square pellet in which two faces have equal lengths and the height or thickness has a different value.

[0011] Heat transfer to the pellet is generally limited to only the top and bottom surfaces of a rectangular parallelepiped (or cylindrical) pellet. In this specification, the modification of heat transfer to the bulk of the semiconductor pellet is analyzed, and a method for enhancing the effective area of heat transfer for the thermoelectric effect is provided through heat transfer by using the pellet sidewall as a path for heat transfer from most regions of the sidewall. The increase in the module output power from this new type of component electrode can be achieved by increasing the effective area of the thermoelectric effect through modification of the isotherms within the bulk of the pellet. There are both linear and non-linear effects on the power output from the thermoelectric effect resulting from the increased effective area. The thermoelectric conversion of concentrated thermal energy to electrical energy generally results in more output power per pellet volume in the case of a thermoelectric generator.

[0012] In one embodiment, the thermoelectric device includes a pellet containing a semiconductor material, a first metal layer surrounding a first portion of the pellet, and a second metal layer surrounding a second portion of the pellet. The first and second metal layers are configured to be proximate to each other around the perimeter of the pellet. The pellet is exposed at the perimeter. The perimeter is configured with a sidewall height around the pellet and provides a non-linear effect on the power output of the thermoelectric device by modifying the isothermal surface curvature within the pellet. The device includes a metal container that is thermally and electrically coupled to the pellet.

[0013] In another embodiment, the isothermal surface curvature within the pellet is operable to increase the effective surface area of the thermoelectric effect within the volume of the pellet via heat injection through the sidewall. In another embodiment, the first and second metal layers include a higher thermal conductivity than the pellet. For example, at least one of the first and second metal layers includes copper. In another embodiment, at least the pellet and the second metal layer are configured in a shape (e.g., rectangular parallelepiped and / or cylindrical) operable to increase the heat lens effect of the thermoelectric device.

[0014] In one embodiment, the first and second metal layers are electrically separated from each other. In this regard, the first metal film and the pellet may include a chamfered edge adjacent to the periphery of the pellet to electrically separate the first and second metal layers from each other.

[0015] In one embodiment, a method of fabricating a thermoelectric device includes metallizing a plurality of semiconductor pellets with one or more layers of metal, removing a portion of the metal layer around the periphery of the semiconductor pellet to create a gap with each of the semiconductor pellets exposing the semiconductor pellet, forming a plurality of cups from copper, electroplating the cups with nickel, and coating a portion of the cups with solder. The method also includes placing one of the pellets into each of the cups such that the sidewall height of each cup matches the gap position of each pellet to provide a non-linear effect on the power output of the thermoelectric device by modifying the isothermal surface curvature within the pellet, curing the solder to bond the pellet to the cup, and attaching the cup to a substrate to form the thermoelectric device. The present invention provides, for example, the following. (Item 1) A thermoelectric device, a pellet including a semiconductor material, a first metal layer surrounding a first portion of the pellet, a second metal layer surrounding a second portion of the pellet, wherein the first and second metal layers are configured to be adjacent to each other around the periphery of the pellet, the pellet is exposed at the periphery, and the periphery is configured with a sidewall height around the pellet to provide a non-linear effect on the power output of the thermoelectric device by modifying the isothermal surface curvature within the pellet, and a metal container thermally and electrically coupled to the pellet. (Item 2) The thermoelectric device according to item 1, wherein the isothermal surface curvature within the pellet is operable to increase the effective surface area of the thermoelectric effect within the volume of the pellet through heat injection through the sidewall. (Item 3) The thermoelectric device according to item 1, wherein the first and second metal layers include a higher thermal conductivity than the pellet. (Item 4) The thermoelectric device according to item 3, wherein at least one of the first and second metal layers contains copper. (Item 5) The thermoelectric device according to item 1, wherein at least the pellet and the second metal layer are configured in a shape operable to increase the thermoelectric device's heat lens effect. (Item 6) The thermoelectric device according to item 5, wherein the shape is a rectangular parallelepiped. (Item 7) The thermoelectric device according to item 5, wherein the shape is a cylinder. (Item 8) The thermoelectric device according to item 1, wherein the first and second metal layers are electrically separated from each other. (Item 9) The thermoelectric device according to item 1, wherein the first metal film and the pellet include a chamfered edge in the vicinity of the periphery of the pellet, and electrically separate the first and second metal layers from each other. (Item 10) A method of manufacturing a thermoelectric device, comprising: metallizing a plurality of semiconductor pellets with one or more metal layers; removing a portion of the metal layer around the periphery of the semiconductor pellet to create a gap with each of the semiconductor pellets, exposing the semiconductor pellet; forming a plurality of cups from copper; electroplating the cups with nickel; coating a portion of the cups with solder; placing one of the pellets into each of the cups such that the side wall height of each cup matches the gap position of each pellet, and modifying the isothermal surface curvature within the pellet to provide a non-linear effect on the power output of the thermoelectric device; Curing the solder to adhere the pellet to the cup, Attaching the cup to a substrate to form the thermoelectric device, a method comprising.

Brief Description of the Drawings

[0016] The present disclosure, where like reference numerals indicate like structural elements, will be readily understood by the following detailed description in conjunction with the accompanying drawings.

[0017] The use of cross-hatching or shading in the accompanying drawings is generally provided to clarify the boundaries between adjacent elements and to facilitate the readability of the figures. Accordingly, the presence or absence of cross-hatching or shading does not indicate a preference or requirement for any particular material, material property, element ratio, element dimension, commonality of similarly illustrated elements, or any other characteristic, attribute, or property of any element illustrated in the accompanying drawings.

[0018] Furthermore, it goes without saying that the ratios and dimensions (either relative or absolute) of the various features and elements (as well as their collection and grouping) and the boundaries, separations, and positional relationships presented therebetween are provided solely in the accompanying drawings to facilitate the understanding of the various embodiments described herein, and accordingly, need not necessarily be presented or illustrated to scale, and are not intended to indicate any preference or requirement for the embodiments described and illustrated with reference thereto.

[0019] Here, some embodiments will be described by way of example only, with reference to the accompanying drawings. The same reference numerals represent the same elements or the same type of elements on all the drawings.

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[0035] Figure 15B shows the device power output of the same thermocouple.

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DETAILED DESCRIPTION OF THE INVENTION

[0046] The drawings and the following description illustrate specific exemplary embodiments disclosed herein. Accordingly, those skilled in the art will understand that, although not explicitly described or shown herein, various principles can be embodied and various arrangements can be devised that are included within the claims. Further, any examples described herein are intended to assist in understanding the principles of the embodiments and should not be construed as being limited to such specifically recited examples and conditions. As a result, the embodiments are not limited to the specific examples described below.

[0047] The exemplary thermoelectric devices and methods disclosed herein increase the performance of a thermoelectric generator by shaping the isothermal field within the bulk of a thermoelectric pellet, resulting in an increase in the power output of the thermoelectric generator module. In the following embodiments, it is computationally shown that the presence of a metal layer on the sidewalls of the pellet has a distinct advantage for power generation, and that the increase in power output generally depends on the thickness of the metal layer, the percentage of metal coating on the sidewalls, and the number of sidewalls having a metal coating on the pellet. The presence of a thermally conductive metal on the sidewalls effectively increases the active region of the isotherms of the thermoelectric effect by inducing a three-dimensional curvature of the isotherms.

[0048] In one embodiment, a thermoelectric device includes a pellet comprising a semiconductor material, a first metal film surrounding a first portion of the pellet, and a second metal film surrounding a second portion of the pellet. The first and second metal films are configured to be proximate to each other around the perimeter of the pellet. The pellet is exposed at the perimeter, which is configured with a sidewall height around the pellet, and provides a non-linear effect on the power output of the thermoelectric device by modifying the isothermal surface curvature within the pellet. The device includes a metal container that is thermally and electrically coupled to the pellet.

[0049] Geometric Effects in the Thermoelectric Seebeck Effect It is analytically shown that as the thickness of the thermoelectric pellet decreases, the output power of the thermoelectric generator increases until the thermal conductivity of the semiconductor pellet cannot support the thermal gradient. Naturally, at this point, as the pellet thickness approaches zero, the output power decreases to zero. The same relationship has been shown computationally, and the results are verified herein as a confirmation of a computational model using an ideal and basic thermocouple component model without all the bonding layers. More specifically, the maximum thermoelectric power can be generated for pellet thicknesses of about 80 - 100 microns, depending on the physical properties of the semiconductor. The maximum current may occur at a thickness value slightly less than the maximum power, while the voltage increases monotonically with the pellet thickness. Thus, the maximum maximum power point is somewhat larger than the pellet thickness for the maximum current.

[0050] The study of the thermocouple device herein was verified through an analytical approach and with a computational model. Here, the temperature-dependent properties of the package components were used. Ideal conditions such as no electrical contact resistance between the thin-film metal electrode on the semiconductor and the semiconductor and no contact heat transfer coefficient were used in the modeling. This model includes the temperature-dependent properties of relevant packaging materials such as copper, aluminum, excluding the solder layer between the TLE and the pellet. The solder layer was not included because it is relatively thin and has a much higher thermal conductivity than the pellet. In one embodiment, the modeling included the measured properties of the semiconductor. In one embodiment, measurements were taken on a semiconductor bar of sintered semiconductor and data collected on the Seebeck coefficient, electrical conductivity, and thermal conductivity as a function of temperature.

[0051] The computational model used herein shows the same maximum power point at generally about 100 microns, in agreement with previous analytical and computational results. The thermoelectric effect as a function of pellet thickness is shown in FIG. 8. In thermoelectric theory, the power output of the pellet is related to the pellet thickness and the cross-sectional area of the pellet.

[0052] For the range of thicknesses where the power is maximum for a given material, the pellets are considered thick films if they are less than about 100 microns. In the case of hot or cold pressing with thermal processing, some semiconductor materials are brittle and prone to cracking after sintering, such as the bismuth and antimony tellurides used here. Thus, due to their handling fragility, it may not be practical to use pick and place automation techniques for thermoelectric thick films. In general, thick films should be fabricated by printing, dispensing, or plating methods, unless they are grown as single crystals and diced into wafer form.

[0053] In accordance with the above results regarding the optimal pellet thickness and the fact that such thermoelectric telluride-based pellets have a brittle effect, an alternative method is proposed to obtain more power per pellet, rather than thinning the pellets. This method involves modifying the thermal gradient within thicker pellets by using a metal sidewall layer on the pellets. Metals are generally very thermally and electrically conductive compared to thermoelectric semiconductors. These physical properties are a distinct advantage when controlling the isothermal temperature field within the semiconductor pellet bulk, which increases the effective volume of the thermoelectric effect. It is computationally shown that the thermoelectric power increases in both linear and non-linear modes by injecting thermal and electrical energy through the sidewalls of the pellets adjacent to the metal thick film.

[0054] The joining of metal to the sidewalls of thermoelectric pellets with high thermal conductivity, and the modification of the thermal gradient within the pellet, are alternative methods proposed to effectively increase the active volume of the thermoelectric effect in order to obtain more power. This method involves the modification of the thermal gradient within the pellet by the use of a metal sidewall layer that provides thermal focusing. One reason for the increase in thermoelectric power generation within a given semiconductor volume is related to the control of the thermal gradient. In particular, the control of the shape of the thermal gradient is one reason for increasing the effective volume of the thermoelectric effect. It has been computationally shown that by introducing a three-dimensional curvature to the isotherms, and by injecting heat and current through the sidewalls of the pellet coated with a thick metal layer, the thermoelectric power increases due to the increase in the effective thermoelectric volume in the pellet. The curvature of the thermal gradient resulting from the thermal lens (focusing) effect changes the shape of the isotherms within the internal volume of the pellet.

[0055] One method of surface mounting technology for assembling metallized thermoelectric semiconductor pellets with other components within a thermoelectric module depends on the material, size and thickness of the pellet, as well as ease of handling. For example, automation techniques in module assembly can result in a cost-effective method by robotic pick and place for mass production. Metallized pellets in the size range of a few millimeters on the edge and with a thickness of about 0.5 - 1.5 mm can be easily placed in trays where pick and place robots can easily construct a thermoelectric module (or cartridge) consisting of hundreds of pellets in a few minutes. Pellets in this size range have the distinct advantage in that they can be easily handled and traced by an operator required for certain process operations (e.g., if the process is not fully automated).

[0056] Some methods of metallization are also much more cost-effective, especially when semi-automatic techniques are introduced to a reasonable extent. Electroplating is one such method, and the thickness of the metal electrode layer can be easily controlled within the electroplating or electroless plating process.

[0057] The injection of heat from the sidewalls is achieved by placing a layer of a relatively high thermal conductivity material, such as metal, on the sidewalls within the volume of a low thermal conductivity material, such as a thermoelectric semiconductor. The ratio of thermal conductivities is important in the thermal injection of heat through the sidewalls of the pellet. Metals such as copper, nickel, or silver can be electroplated to form such a layer. As the sidewall material becomes thicker, the thermal conductance increases, and more heat can move from the sidewalls into the pellet according to the conductance. This injection of heat can result in a deformation of the shape of the thermal gradient within the pellet. The spatial modification of the thermal gradient can result in a change in the spatial generation of the current provided by the thermoelectric effect when compared to the planar isotherms generated within the pellet when using only standard electrodes at the top and bottom of the pellet.

[0058] The power generated by the thermoelectric effect may directly depend on the area of the thermal gradient, and this area can be increased without changing the volume of the pellet. The internal volume of the pellet between the top electrode surface and the bottom electrode surface can also be utilized through the sidewalls of the pellet. When heat is injected through the electrodes on the sidewalls and the top and bottom electrodes, the isotherms within the pellet defined by the thermal gradient are generally no longer parallel to the top and bottom surfaces (e.g., 2D parallel isotherms) as they would be in the absence of metal on the sidewalls.

[0059] The injection of heat into the sidewalls may change the shape of the isotherms to a curved surface (dome shape) within the pellet, having a 3D shape rather than a 2D planar shape, thereby increasing the area of the thermal gradient. Such a change of the shape of the isotherms to a 3D surface increases the effective area of the thermoelectric effect within the volume of the pellet, thereby increasing the generated thermoelectric power. Also, due to the charge carrier injection through the sidewalls (e.g., because the conductivity of the metal is high), with the enhancement of the thermal gradient, more charge carriers can be driven to the counter electrodes, so the thermoelectric current also increases.

[0060] The thermoelectric current generated by the thermoelectric effect, and thus the power, is proportional to the effective surface area of the thermal gradient consisting of parallel isotherms. This current is generally proportional to the second spatial derivative of the temperature gradient and is thus approximately parallel to the normal of the thermal gradient throughout the volume where the thermoelectric effect occurs. In the steady state, the equation for the second spatial derivative of the temperature field is, as follows, proportional to the Joule heating effect (~I 2 ) : [Number] where I is the thermoelectric current, and the Thomson contribution of the thermoelectric current is ignored in J as it balances to zero.

[0061] The second derivative of a variable describes its curvature, and the inverse of the curvature is the radius. Thus, the thermo-lens electrode effect reduces the radius of curvature of the isotherms within the pellet volume, generates dome-shaped isotherms, increases the thermoelectric current, and thus increases the output power. Without increasing the size or shape of the pellet, this effective increase in the surface area of the isotherms allows more power to be generated within the pellet volume. Thus, more thermal energy can be converted into power by directing or focusing the heat transport per semiconductor volume. The power output of a thermoelectric module can increase by up to approximately 60% when using thermally enhanced thermoelectric pellets.

[0062] In summary, since the thermoelectric effect directly depends on the area of the thermal gradient, the modification of the thermal gradient within the pellet by the TLE results in an increase in the output power. The power is increased by increasing the effective area of the thermoelectric effect within the pellet, usually by modifying the isotherms to have 3D curvature within the pellet. Thus, more isotherm regions per semiconductor volume are generated. More current, and thus power, can be generated within the pellet by increasing the surface area of the isotherms. Since the thermoelectric current is proportional to the effective surface area of the isotherms within the pellet, more power can be converted by enhancing the heat transport.

[0063] Calculation Analysis and Related Theories The computational analysis was performed using the Comsol Multiphysics program including the Multiphysics thermoelectric module. The scale for modeling was selected for convenience when meshing small components and high geometric aspect ratios. For these results, a pellet size of 6×6×1 mm was selected, and all other components were geometrically automatically scaled to match the pellet size without changing the basic configuration of the thermocouple. All calculations were based on time-independent steady-state conditions. That is, the boundary conditions for each interface are essentially constant at a temperature independent of time. Due to these fixed boundary conditions, the heat injection on each sidewall can be added linearly.

[0064] In the computational analysis, several metal layers were omitted to more easily align the mesh at the interfaces between components and reduce the calculation time. Alternatively, an increase in the thickness of the components to accommodate meshing is accompanied by an appropriate reduction in the physical properties to effectively maintain both thermal and electrical conductivities. Figure 1, for example, does not include the thin metal film of the pellet required for soldering to the TLE110. This is because both have relatively very high thermal and electrical conductivities compared to the pellet. In Figure 1, it is shown that a square semiconductor pellet 100 is inserted into the TLE110 with four thermally conductive sidewalls 111 starting from the upper electrode and leaving a 0.25 mm sidewall metallization gap at the bottom of the pellet. The pellet 100 and the TLE110 can be joined together with solder to provide a thermally enhanced thermoelectric component (TETC). Also, when avoiding components with a high aspect ratio thickness, the convergence of the Multiphysics solution is more achievable. In most cases, the temperature difference from the high-temperature side to the low-temperature side was 100 °C. Since the package is symmetric through the middle plane of the pellet and functions to maintain the stress balance of the thermal stress, the thermally induced stress between components was ignored.

[0065] Figure 2 shows one exemplary TLE component 110 having a 1 mm wall 111 of pellet 100. The TLE component 110 is a sub-component of the TETC for attaching the pellet 100 having a solder layer within the TLE 100. The analysis did not extend beyond this thickness. In one embodiment, the thermal lens electrodes shown in Figure 2 are copper or nickel that established the nature of the thermal lens effect using the varying metal thickness and height of this component.

[0066] In Figure 3, a square semiconductor pellet 100 is shown within four thermally conductive sidewalls 111 of the TLE component 110. In one embodiment, the pellet 110 starts with an upper electrode having a metal gap 114 of 0.25 mm left at the bottom of the pellet. The semiconductor pellet 100 is illustrated with an inclined shape 112 for electrically separating the upper and bottom electrodes.

[0067] The components of Figure 3 vary greatly in the industry depending on the materials used in the assembly of the thermoelectric device, and are exemplarily incorporated into the Comsol geometric structure of a thermocouple having all ideal interfaces, i.e., a thermocouple without electrical or thermal barriers. Therefore, using an ideal device, a performance degradation was expected for non-ideal conditions, and the results were constructed expecting that non-ideal results could be easily included by the above method. Further, the model used either the measured (semiconductor) or temperature-dependent materials included in the Comsol material library.

[0068] Figure 4 shows one exemplary computational geometry shape of a single thermocouple device 120 including two square semiconductor pellets, N and P pellets, with four copper sidewalls as the thermocouple. In this embodiment, the side view of the thermocouple device 120 is illustrated with two square semiconductor pellets each having four copper sidewalls starting from the bottom electrode interconnects on each pellet. The thickness of the sidewalls is 1 mm, and there is a 0.15 mm metal gap for the upper electrode interconnect.

[0069] The copper metal resistance load is shown above the pellet and is parametrically modified by resistivity to simulate a varying load for generating a load line. The load lines are shown in FIGS. 18 and 20 along with other parameters and have a metal sidewall thickness and temperature difference between the high-temperature side and the low-temperature side, respectively. As expected, these are linear relationships.

[0070] FIG. 5 is an isometric view of one exemplary single thermocouple device 120 having four copper sidewalls with a height of 0.65 mm and a thickness of 0.2 mm starting from the upper electrode of each pellet, and a 0.35 mm metal gap at the bottom electrode.

[0071] FIG. 6 shows another view of the thermocouple device 120 having two pellets 100. FIG. 6 typically shows from the bottom component to the top component. That is, an anodized aluminum substrate, copper interconnects, N-type and P-type pellets, and 1 mm thick copper sidewalls (transparent rendering) on three sides of each pellet for heat and current injection are shown. The thicker sidewall metal thickness results in higher thermal and electrical conductances as shown in FIG. 18 where a 1 mm sidewall thickness has the highest power output. Further, as shown when the sidewall coating ratio is increased, compared to the case of 0.05 mm with coating ratios of 0.85 and 0.65, and in the case of nickel with a 0.2 mm thick sidewall having a metal sidewall coating ratio as a parameter, higher output is provided as observed in FIG. 10.

[0072] FIG. 7 is one exemplary computational mesh 140 in a thermocouple circuit for the case of a sidewall having a gap at the top of the sidewall. The limits of meshing are determined by the thickness aspect ratio of adjacent components. As described above, there are means to compensate for these limitations by adjusting the thickness and physical properties of the materials.

[0073] FIG. 8 shows one exemplary relationship 150 between the device power of the thermocouple circuit and the pellet thickness normalized to the 1 mm thick pellet device power output. Calculations are derived to provide an analytical solution for the thermocouple. These calculations herein confirm these results and provide motivation to increase the power output by an alternative method, namely, including sidewall metal coatings in the package of the thermoelectric module.

[0074] FIG. 9 shows an exemplary normalized maximum power output 160 for a 1 mm thick pellet without metal sidewalls versus the number of sidewalls covered with metal. That is, FIG. 9 shows the normalized linear maximum power output for a pellet without metal sidewalls versus a 1 mm thick pellet and the percentage of nickel metal sidewall coating in this embodiment where the metal coating of each sidewall used is 0.8 mm (80%). The relationship is linear (R 2 = 1) with respect to the power output for the number of sidewalls present on the pellet. This relationship is consistent with the analytical results having similar boundary conditions of a 2D rectangle for the solution of the steady-state heat equation. In the analytical case, homogeneous (or unmixed boundary) conditions are used. This is the case of steady-state heat transfer where heat injection is added linearly so that all sidewalls can be treated independently of each other. Thus, the power generated through the thermoelectric effect is additive for each sidewall, thereby resulting in a linear relationship for the output power with respect to the number of sidewalls present on the pellet. It should be noted that the results of the computational model are consistent with the analytical results even though the boundary conditions in the model are non-uniform due to the gaps in the sidewall metal to avoid short-circuiting between the top and bottom of the pellet electrodes. This means that it can be solved by separating the analytical solution of the temperature field for each sidewall and each part of the sidewall not covered with metal. These results are summarized in FIGS. 25A and 25B where the isotherms from the analytical results match the isotherms from the computational results of FIG. 13. Note the similarity between the analytical and computational results and confirm the curvature of the isotherms. The curvature of the isotherms increases the area of the thermoelectric effect and thus outputs power in a linear fashion with respect to the number of sidewalls present.

[0075] Figure 10 shows one exemplary maximum device power output 170 normalized with respect to the maximum power for pellets without metal sidewalls, versus the ratio of nickel metal sidewall coating for pellets of 1 mm thickness. Figure 10 shows an example of the maximum power output of a thermocouple with sidewall metal coating normalized to the maximum power output in the case without sidewalls, with the ratio of sidewall metal coating as a parameter. In this case, the metal thickness is 0.2 mm. This non-linear behavior indicates something that has not been shown previously because the thermoelectric effect was not used in the previous analytical solutions for the solution of the temperature field, namely that the thermal lens effect is non-linear with respect to the ratio of sidewall coating. Solutions for the case of non-uniform boundary conditions are known. The polynomial used to describe the non-linear behavior has an R 2 Note that is 1 and is the sixth power of the ratio of sidewall coating.

[0076] Figure 11 shows one exemplary cross-section of a thermal gradient 180 passing through the center of a pellet with sidewall metal that causes a thermal lens for the case of a sidewall thickness with an opening of 0.05 mm centered on 0.5 mm of the pellet height. The thermal lens is symmetrically present on both the upper and lower parts of the pellet, generating dome-shaped isotherms that increase the active region of the thermoelectric effect.

[0077] Figure 12 shows one exemplary cross-section of a thermal gradient 190 of 100 °C passing through the center of a pellet without sidewall metal, resulting in planar isotherms.

[0078] Figure 13 shows an exemplary heat concentration 200 for the case of an opening with a width of 0.2 mm located at the upper part of the pellet for a sidewall thickness of 1 mm. It should be noted that the thermal lens effect is very strong near the edge.

[0079] Figure 14 shows an exemplary heat concentration 210 for the case of an opening with a width of 0.05 mm located at the bottom of the pellet for a nickel thickness of 0.2 mm. The isotherm curvature is the reverse of that in Figure 13, indicating that the isotherm curvature is essentially independent of whether the metal gap appears to be located on the high-temperature or low-temperature side of the pellet.

[0080] Figures 15A and 15B show exemplary advantages of the metal gap position. For example, FIG. 15A compares the resistive load loss 220 of a thermocouple as a function of the center of all four 0.05 mm wide openings in the pellet sidewall. FIG. 15B shows the thermoelectric power output 222. The pellet sidewall in this embodiment is nickel metal at a thickness of 0.2 mm. The thermocouple device power output is a function of the center of the position of the 0.05 mm wide metal openings in all four sidewalls. Note that the maximum power occurs when the opening is located near either the top or bottom of the pellet, indicating that the thermo-lens effect is strongest when the metal gap is offset from the center with respect to the height of the pellet. Generally, the load loss of the thermocouple as a function of the center of all four 0.05 mm wide openings in the pellet sidewall.

[0081] FIG. 15A also shows the variation of the effective power output when the center of the 0.05 mm wide gap varies in position on all four pellet sidewalls. When the metal gap is located close to either the bottom electrode or the top electrode, the power output increases relative to other positions of the gap. Note that the maximum power occurs when the opening is located near either the top or bottom of the pellet, indicating that the thermo-lens effect is strongest when the metal gap is offset from the center with respect to the height of the pellet. The positive resistive power load is the opposite of the generated power, since power generation is considered the opposite of power loss. The curvature of the temperature isotherms is greater for these positions and is completely symmetric with respect to performance at either position. The smaller the gap, generally, the higher the heat and current injection, resulting in a higher power output. Apparently, the computational limit of the gap width is determined by meshing and is most likely physically determined by the practical nature of manufacturing the gap on the side of the pellet by laser ablation of a thin film of metal on the pellet before bonding the TLE.

[0082] FIG. 16 shows an exemplary maximum device power output versus an external resistance load factor 230 having a nickel metal sidewall coverage ratio as a parameter. At the peak of each curve, the resistance load matches the internal resistance of the thermocouple device where the device includes pellets and electrical interconnections as part of its internal resistance. The straight line 232 passing through the peak implies an inverse linear relationship between the maximum device power output versus the external resistance load factor because the internal device resistance decreases with an increase in the sidewall coverage. Since the maximum power occurs when there is a load matching with the internal resistance of the pellet, a decrease in the internal device resistance requires a decrease in the external matching as well.

[0083] FIG. 17 shows an exemplary parameter relationship 240 between the normalized maximum power output of a thermocouple versus the ratio of a metal sidewall coverage having a metal thickness as a parameter. The copper metal sidewall coverage is on all four sidewalls of each pellet of the thermocouple having a metal sidewall thickness as a parameter in the range of 0.05 - 0.2 mm thickness. At a thickness of 0.20 mm, the thermal lens effect is the strongest. The increase in the metal coating and thickness is accompanied by an increase in the thermal conductance through the metal sidewall layer and thus an increase in the heat injection and an increase in the heat concentration. Thus, as either the ratio of the metal coating or the metal thickness increases, the device power output increases.

[0084] Figure 18 shows exemplary current-voltage load lines 250 of three thermocouple devices 251, 252, and 253 with metal sidewall coatings on all four sidewalls for metal sidewall thicknesses of 0.05 mm and 1 mm and ratios of pellet height of 0.65 and 0.85 with respect to sidewall coating. The 1 mm thick sidewall is expected to generate more power because it has increased thermal conductivity compared to the 0.05 mm thick sidewall. A comparison of the ratio of 0.05 mm to 0.85 in the 0.05 mm load line reveals a crossover point at high voltage because the increased metal coating in the 0.85 mm case reduces the open circuit voltage through a partial short circuit of the device along the sidewall. However, at high current, the heat concentration effect results in a larger short circuit current, while the maximum power (occurring at half the short circuit current and half the open circuit voltage) is slightly larger for the 0.85 case than for the 0.65 case. These two load lines show the sensitivity of the maximum power to the metal coating.

[0085] Figure 19 shows an exemplary current-voltage load line 260 of one of the three thermocouple devices 251, 252, and 253 of Figure 18 with metal sidewall coatings on all four sidewalls for metal sidewall thicknesses of 0.05 mm and 1 mm and ratios of pellet height of 0.65 and 0.85 with respect to sidewall coating. The device power versus resistance load with metal sidewall coating is one parameter. The peak is where the resistance load matches the internal resistance of the thermocouple device. The output power shows that the 0.85 coating is larger than the 0.5 coating and the crossover is at 0.25 volts.

[0086] Figure 20 shows exemplary current-voltage load lines 270 for four temperatures (50 °C, 100 °C, 150 °C, 200 °C) for the case of three sidewalls with a thickness of 1 mm. The trend is expected and further validates the computational model.

[0087] FIG. 21 shows one exemplary semiconductor pellet sub-component 280 of a TETC. For example, FIG. 21 shows one exemplary thin metallization (253) pellet that is ready to be bonded to a TLE component. Four features are a thermoelectric semiconductor pellet 281, a primary metal layer 282 for an adhesion and / or diffusion barrier (titanium, tungsten, Ni-P

[20] , chromium, active brazing alloy, etc.), a solderable and oxidation-resistant metal layer 283 (gold, palladium, and Ni-P), and a gap 284 (e.g., discontinuity) in metal layer 283 from the surface of metal layer 282 to the semiconductor material of pellet 281. Any number of thin film metal layers can be used according to a final layer that provides a solderable surface such as gold, silver, Ni-P, etc. Generally, the metal gap 284 is to cut off conductivity on the pellet sidewall from the upper electrode to the lower electrode.

[0088] FIG. 22 shows one exemplary completed TETC component 290 with layer details. Features include an N or P type semiconductor pellet 281, the material being removed through a multi-layer deposit to create a gap 284 (i.e., discontinuity) at the metal surfaces 282 / 283 up to the semiconductor surface of pellet 281, and a bonding material 291 such as solder (Sn-Ag-Cu, In-Ag

[21] , In-Sn) that thermally and electrically couples the outer surface of pellet 281 to the inner surface of sub-component TLE 292 except where the discontinuous metal gap 284 is located. Features 282 and 283 are the thin films discussed in FIG. 21, but any number of thin film layers that meet the requirements can be used.

[0089] FIG. 23 shows, as an example of an application, one exemplary detailed cross-section of two TETC components attached to a thermoelectric module 300. In this packaging option, two separate metal interconnects (submounts) are joined to a solder layer 291 that also serves to bond pellet 281 to a substrate 304. The upper metal substrate has square through-holes to provide a thermal lens for the metallized semiconductor pellet layer.

[0090] FIG. 24 shows, as an example of an application, an exemplary detailed cross-section of one of two TETC components attached to a thermoelectric module 300. This packaging option uses a press-formed metal substrate to provide a heat lens to the pellet 281.

[0091] FIGS. 25A and 25B show an exemplary comparison of one of two visualizations of isotherms calculated by the Fourier method using variable separation and identical to the isotherms determined by the calculation method of this specification.

[0092] Assembly Aspects of Thermally Enhanced Thermoelectric Components (TETCs) This specification presents a method for significantly increasing the output power of a thermoelectric generator device by changing the electrode shape of semiconductor pellet components used in the assembly of a thermoelectric module. It is proposed that the metal sidewalls be formed as separate assembly steps as sub-components and then joined to pre-metallized semiconductor pellets via soldering. These two sub-components combine to form a new electronic component for high-speed packaging surface mount technology. This method is not applicable to the cooling mode of a thermoelectric module because the Peltier effect and the Seebeck effect are opposing (backing) currents. The effect of the heat lens electrodes on the Peltier operating mode results in a slight decrease in the coefficient of performance in the cooling mode.

[0093] When using metal for the sidewalls, the sidewalls have an opening, or gap 284, that breaks the conductivity between the top and bottom electrodes of pellet 281 and prevents electrical short circuits. Such openings can be created by laser ablation along the sidewalls of pellet 281 after thin-film metallization. The opening width can be 50 microns or less, or narrowed to a practical limit. When using small openings in the sidewall metal, there can be two focusing effects depending on the position of the openings. A narrow opening located around the pellet parallel to the upper surface at the center of the sidewall creates two thermal focusing effects, one near the upper side of the pellet and one near the bottom side. The center of an opening located near the top or bottom of the pellet results in a higher power output than other positions of the opening.

[0094] By chamfering the four edges at the top or bottom of the pellet, the interruption of the sidewall conductivity can be achieved

[0095] The fabrication of thermally enhanced pellets (TEPs) generally involves (1) lens electrode (TLE) components, (2) metallized pellets (281, 282, 283) having cuts in conductivity on all sidewalls (i.e., gap 284), and / or (3) solder for bonding the TLE and the pellet. The fabrication can be achieved in a practical sense by a two-step process. First, solderable surfaces on each sub-component can be used to form solder-bonded joints. Thin-film methods such as electroplating or electroless plating can be used to coat the pellets with various metals to form adhesive layers, diffusion barriers, and solderable layers in various ways. The final metal layer generally preferably has a solderable metal for joining to the TLE, made from copper, nickel, silver, or any metal having a solderable finish. An appropriate amount of solder is dispensed onto the TLE, or a fluxless preform of appropriate thickness is inserted at the bottom of the TLE, and then the pellet is placed within the TLE. After reflow of the solder at the bottom and sidewalls of pellet 281, the two are joined together. It is desirable to use a solder that melts at a higher temperature than the solder used to join the rest of the package components. Thus, the electronic component is fabricated for assembly where high-speed pick and place methods can be used.

[0096] For a single thermocouple in power generation mode, it is shown that an increase in the power output of the device is achieved by thermal and electrical injection into the sidewalls of the pellet. (1) The effect of gradually adding metallized sidewalls of the same thickness until the sidewalls become metal of the same thickness (linear dependence on the number of sidewalls), (2) the sidewall height varies from a height of 0 of the pellet thickness to about 0.95 (non-linear effect increasing with the metal sidewall height), and / or (3) the case of varying the position of the 0.050 mm gap of the sidewall metal may be investigated. Each variation has its own effect of increasing the device power output through heat concentration. In fact, contrary to the normal practice in the assembly method of a thermoelectric power generation device (for example, a partial electrical short circuit is expected along the sidewalls, resulting in a decrease in the device power output), there are advantages to partially metallizing the sidewalls of the semiconductor pellet. To avoid electrical short circuits, by leaving a narrow gap or slit in the metallization of all sidewalls between the upper and lower metal electrodes. This can result in a significant increase in thermoelectric power generation by heat concentration or lensing. The results can be presented based on computational analysis with measured physical properties, having a metallized gap width thickness of 50 microns for all four sidewalls and a uniform metallization thickness of 0.05 - 1 mm (for example, bismuth - selenium - telluride and antimony - bismuth - telluride thermoelectric pellets). The gap 284 that breaks conductivity is positioned symmetrically around the pellet 281.

[0097] One way to increase the output power of a thermoelectric generator by a significant factor involves changing the shape of the electrodes adjacent to the semiconductor pellets 281 used in the component assembly of the thermoelectric module. New components are recommended for use in the surface-mounted component assembly of the thermoelectric module. The increase in power output is achieved by thermal and electrical injection into the bulk of the semiconductor pellets through the sidewalls of pellet 281. In fact, contrary to normal assembly methods, there is an advantage in partially metallizing the sidewalls of semiconductor pellet 281. Further, leaving a small gap 284 or slit in the sidewall metallization between the upper and lower metal electrodes significantly increases the generation of thermoelectric power through the thermal lens electrodes. The results are presented based on a computational analysis of a 50-micron metallization gap width on all four symmetrically placed sidewalls of the telluride-based thermoelectric pellets.

[0098] FIG. 21 shows an exemplary cross-sectional view of one of the pellet 281 sub-components for TETC. Typically, the pellets can be electroplated or electroless plated since these methods can be easily implemented in large quantities by modern plating companies. Several layers (e.g., layers 282 and 283) can be sequentially plated to fulfill functions such as adhesion, diffusion barrier, and solderable layers for bonding to other components. The number of layers can typically be 3 - 4, as needed, as described in the previous section. Methods for depositing these layers include physical vapor deposition, explosive lamination, electroplating, electroless plating, high-pressure compression lamination, or pressing. When metal layers are deposited on both N-type and P-type pellets, a gap 284 in the metal layer is formed on all four sidewalls of the semiconductor pellet 281, breaking the conductivity on the sidewalls of the pellet. This operation can include grinding wheels, special saws, lasers, abrasive wires, or EDM techniques. The removal of sidewall metal of an appropriate height along the pellet sidewalls is important as described above, and the gap 284 is continuous along all sidewalls, preferably at the same height on all four sidewalls.

[0099] FIG. 22 shows one exemplary completed TETC component that has the layer details and uses the same aspect of the semiconductor pellet as exactly described in FIG. 21. The method of assembling the metal TLE 292 (e.g., in the shape of a square metal cup) can be embodied by various techniques. Techniques such as pressing, molding, electroforming, stenciling, die casting, and casting can be used. The TLE is attached to the N and P pellets by conventional or special solder, as mentioned in the previous section, which reflows at a temperature different from the temperature of the solder that attaches the TLE to the metal substrate (electrical interconnect). The difference in reflow temperature is usually necessary to enable multi-step assembly. Solder candidates include transient liquid phase alloys. These alloys contain pure metals (In, Sn) that melt at low temperatures and metals (Ag, Cu) that melt at high temperatures. When melting is initiated, intermediates are formed during the process and the freezing of the solder begins. When the intermediate compound is formed, the next melting is relatively high (650 °C in the case of In-Ag). Therefore, more conventional alloys such as Sn-Ag-Cu (SAC) can be used for the remaining assembly to join the components. For these types of alloys in the field, one embodiment includes using Ag-Sn to keep the material cost low. Additionally, more conventional solders, preferably lead-free solder alloys, can also be used.

[0100] In FIG. 22, the N- or P-type semiconductor pellet sub-component has material 283 / 284 removed through the multilayer deposit, creating a discontinuity within the metal surface up to the semiconductor surface. The solder layer 291 (Sn-Ag-Cu, In-Ag

[21] , In-Sn, Ag-Sn) discussed above, and a bonding material that is thermally and electrically coupled to the outer surface of the pellet and the inner surface of the TLE sub-component, are applied to bond the metallized pellet and the TLE 292 surrounding the pellet surface on all four sides (e.g., to a discontinuous metal gap or to a slightly lower height). The metal layers 282 / 283 are shown again in the TLE 292, except where the discontinuous metal gap 284 is located. In this embodiment, the metal layers 282 / 283 are the thin films discussed in FIG. 21, although any number of thin film layers that meet the requirements can be used.

[0101] FIG. 23 shows a cross-section of one type of application of the TETC 300 that utilizes a two-piece assembly (i.e., TETC-2L) where both substrates are dimensionally matched in the lateral direction in order for one to fit over the other having a matching perimeter of the substrates. In other words, the substrates are generally identical parts and, when stacked vertically, the two substrates are intended to be a single unit for TETC component placement. The bottom substrate 304 is solid, while the top substrate 306 has two square openings (through-holes) through the thickness of the substrate. The square holes in the top substrate can be created through processes such as laser cutting, pressing, casting, molding, machining, and manual cutting. These square openings provide heat for the thermal lenses of the N and P pellets 281 after being joined to the substrate by the solder 291. The previous features as described in FIGS. 21 and 22 are modified to provide a dual TLE component that provides a thermal lens to the two semiconductor pellets 281. The lower piece 304 of the two-piece TLE supports the upper part of the TLE component. Thus, in component 306, the modified substrate has a dual thermal lens electrode component having two substrate layers, or TETC-2L.

[0102] Figure 24 shows yet another method of applying a thermal lens to pellet 281. Similar to the case of TECT-2L, the TLE sub-component is modified to include two pellets 281. In this packaging option, the TLE is modified in the same way as TLEC-2L through processes such as laser cutting, pressing, casting, molding, machining, and manual cutting. As shown in Figure 23, the previous features described in Figures 21 and 22 are used in Figure 24. In Figure 24, the portions of features 306 and 304 are modified to provide a dual TLE component that provides thermal lenses for two semiconductor pellets using a single metal substrate. Thus, in this component, this modified substrate is a dual thermal lens electrode component having a single substrate layer, or TETC-1L.

[0103] In any or all of the above-described embodiments, the metal sub-component of the TETC has a relatively high thermal conductivity and electrical conductivity (e.g., copper plated with nickel).

[0104] Figure 23 shows some exemplary features that can be used in manufacturing. For example, in one embodiment, pellet 281 is a thermoelectric semiconductor component metallized with multiple layers including feature 282, a diffusion barrier, and layer 283 (e.g., a noble metal on top of the pellet 281 substrate to prevent oxidation). Manufacturing methods used to create such multi-layer deposits on the pellet can include physical vapor deposition (PVD), explosive lamination, sputtering, electroplating, electroless plating, and high-temperature lamination.

[0105] The gap 284 includes a slit where metal removal has been performed to create a thermal and electrical cut at the outer peripheral edge of the pellet to avoid short - circuits. This cut provides a thermal lens effect for improving power output. Some of the manufacturing methods used to create features in the gap 284 include wire electrical discharge machining (EDM), abrasive wire cutting, metallization process masking, abrasive saw cutting, and laser etching. The metallized pellet 281 can then be placed in a two - piece thermal lens device consisting of a solid component 304 and a twin cavity implemented by component 306. Components 304 and 306 can be manufactured by pressing, 3D printing, laser cutting, waterjet cutting, wire EDM, CNC machining, or casting. Components 304 and 306 can also be made as one piece by 3D printing, pressing, and CNC machining. Components 304 and 306 can include copper to prevent oxidation and can be electroplated with nickel. The cavity of component 306 generally matches the shape of the pellet 281 (e.g., slightly larger than the pellet 281 to provide space for the bonding material 291). Component 304 can include a cavity that is attached to the solid piece component 306 by thermal soldering, ultrasonic soldering, explosive lamination, hot pressing, and adhesives that are thermally and electrically compatible. Thus, components 304 and 306 become a one - piece component with two cavities such that a completed metallized pellet 281 having the gap 284 can be placed and attached to components 304 and 306 through a curing process specific to the bonding method of the solder bonding material.

[0106] The internal square cavity formed by the opening of component 306 can be coated with solder (e.g., by dispensing, stencil printing, and mask spraying) so that pellet 281 (and layers 282 and 283) can be attached thereto. All or part of the components can be placed in tape & reel, vibrating bowl, tube, or Joint Electron Device Engineering Council (JEDEC) trays for utilization of high-speed placement by a robotic system. A suitable thermal adhesive can be printed using a stencil to hold components 304 and 306 during pick and place by a high-speed robot. This process can be repeated many times to implement on a package substrate and construct a large industrial module or cartridge. Next, the P-type and N-type pellets 281 can be placed within these cavities such that the sidewall height of component 306 matches the height of the gap 284 slit using a high-speed robotic system. The thermal lens assembly 300 can be repeated many times on a module package substrate (e.g., copper-coated alumina, anodized aluminum, or other suitable flat substrate) such that the lower half elements of the cartridge (or module) surround the pellet 281. The upper substrate with metal interconnects (e.g., layer 304) attached can be positioned and numbered appropriately and joined to complete a series circuit between components on the bottom substrate. Solder can be printed on top of the pellet 281 on the bottom substrate and joined together to the package substrate. Next, this foldable assembly can be placed within an aluminum retainer that applies slight pressure to the assembled module. The assembly can then be heat treated by a batch oven, conveyor reflow oven, ultraviolet (UV) curing, and / or ultrasonic welding system to complete the process of curing the materials and reflowing the solder.

Claims

1. A thermoelectric device, comprising: a semiconductor pellet; a first metal layer metallized around the semiconductor pellet; a second metal layer metallized around the first metal layer; a gap in the first metal layer and the second metal layer, the gap being formed by removing the first metal layer and the second metal layer around the periphery of the semiconductor pellet to expose the semiconductor pellet, the first metal layer and the second metal layer remaining on the sidewalls of the semiconductor pellet above and below the gap, the sidewalls having a sidewall thickness such that the combined thickness of the first metal layer and the second metal layer on the sidewalls of the semiconductor pellet is in the range of 0.05 mm to 1 mm; a metal container thermally and electrically bonded to the second metal layer via solder; and the first metal layer, the second metal layer, and the semiconductor pellet are configured to electrically isolate a portion of the first metal layer and the second metal layer above the gap from another portion of the first metal layer and the second metal layer below the gap.

2. The thermoelectric device according to claim 1, wherein the gap is configured at a sidewall height that provides a non-linear effect on the power output of the thermoelectric device by modifying an isothermal surface curvature within the semiconductor pellet.

3. The thermoelectric device according to claim 2, wherein the isothermal surface curvature within the semiconductor pellet is operable to increase an effective surface area of a thermoelectric effect within the volume of the semiconductor pellet via heat injection through the sidewalls of the semiconductor pellet.

4. The thermoelectric device according to claim 1, wherein the metal container surrounds the second metal layer in the vicinity of the gap.

5. The thermoelectric device according to claim 1, wherein the metal container provides a heat lens electrode structure.

6. The thermoelectric device according to claim 1, wherein the first metal layer and the second metal layer include a higher thermal conductivity than the semiconductor pellet.

7. The thermoelectric device according to claim 1, wherein the semiconductor pellet is configured in a shape operable to increase a heat lens effect of the thermoelectric device.

8. The thermoelectric device according to claim 7, wherein the shape is a rectangular parallelepiped.

9. The thermoelectric device according to claim 7, wherein the shape is cylindrical. **Claim 10** The thermoelectric device according to claim 1, wherein portions of the first metal layer and the second metal layer above the gap are electrically separated from other portions of the first metal layer and the second metal layer below the gap. **Claim 11** The thermoelectric device according to claim 1, wherein the first metal layer comprises copper, titanium, tungsten, nickel-phosphorus, or a chromium alloy. **Claim 12** The thermoelectric device according to claim 1, wherein the second metal layer comprises copper, nickel, silver, gold, palladium, or nickel-phosphorus.

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