WO2018060233A1

WO2018060233A1 - Component carrier with fully encapsulated thermoelectric device

Info

Publication number: WO2018060233A1
Application number: PCT/EP2017/074472
Authority: WO
Inventors: Jonathan Silvano De Sousa
Original assignee: At&S Austria Technologie & Systemtechnik Aktiengesellschaft
Priority date: 2016-09-27
Filing date: 2017-09-27
Publication date: 2018-04-05

Abstract

A component carrier ( 100) which comprises a heat absorbing and thermally conductive surface layer (102) configured for being heated by an external heat source (104), and a thermoelectric device (106) fully surrounded by material of the component carrier (100), thermally coupled with the surface layer (102) and configured for transferring thermal energy of the heated surface layer (102) into electric energy.

Description

Component carrier with fully encapsulated thermoelectric device

The invention relates to a component carrier, to a method of manufac- turing a component carrier, to method of operating a component carrier, and to a method of use.

In the context of growing product functionalities of component carriers equipped with one or more components and increasing miniaturization of such components as well as a rising number of components to be mounted on the component carriers such as printed circuit boards, increasingly more powerful array-like components or packages having several components are being employed, which have a plurality of contacts or connections, with ever smaller spacing between these contacts. Removal of heat generated by such compo- nents and the component carrier itself during operation becomes an increasing issue. At the same time, component carriers shall be mechanically robust and electrically reliable so as to be operable even under harsh conditions.

EP 2,903,042 Al discloses a thermoelectric module comprising at least a support element, wherein the support member has at least one heat- conducting area for heat conduction between two opposite sides of the support member, wherein the heat-conducting area has a higher thermal conductivity than other areas of the support member. Further, the thermoelectric module comprises at least one thermoelectric member fixed in the heat-conducting area of the support member, said thermoelectric module is thermally coupled to the heat-conducting area. Finally the thermoelectric module comprises at least one cover member which is arranged on one side, opposite to the support member, of the thermoelectric module and at least partially covers the thermoelectric module.

US 2011/248846 discloses a wireless sensing module with extended service life containing at least one sensor of a physical parameter, a data acquisition hardware acquiring output electrical signals from at least one sensor and converting It into digital measurement data, a microcontroller, a non-volatile memory, at least one transceiver for wireless communication with external wireless devices, at least one battery, including at least one re- chargeable battery, at least one energy harvesting device, a power manage- ment circuit, and at least one antenna. All components of the wireless sensing module are mounted on a printed circuit board and placed into an enclosure providing mechanical, chemical, electrical and environmental protection. The wireless sensing modules can be used in different applications, including long- term condition monitoring of structures.

It is an object of the invention to provide a reliably operable component carrier with an efficient energy management and being manufacturable with reasonable effort.

In order to achieve the object defined above, a component carrier, a method of manufacturing a component carrier, a method of operating a component carrier, and a method of use according to the independent claims are provided.

According to an exemplary embodiment of the invention, a component carrier is provided which comprises a heat absorbing and thermally conductive surface layer (in particular a planar layer) configured for being heated by an external heat source (such as a hot machine part, the sun, etc.), and a thermoelectric device (such as a thermocouple) fully surrounded by (i.e. forming not even part of an exterior surface of the component carrier) material of the component carrier, thermally coupled with the surface layer and config- ured for transferring thermal energy of the heated surface layer into electric energy.

According to another exemplary embodiment of the invention, a method of manufacturing a component carrier is provided, wherein the method comprises interconnecting (in particular at least partly by laminating) a layer stack (i.e. an interconnected stack of at least two structures, which may be electrically insulating and/or electrically conductive) comprising a heat absorb- ing and thermally conductive surface layer which is arranged at a surface of the layer stack and at a surface of the component carrier for being heatable by an external heat source, thermally coupling a thermoelectric device with the surface layer for transferring thermal energy of the heated surface layer into electric energy, and fully surrounding (such as embedding, integrating in, building in, providing native or encapsulating) the thermoelectric device by material of the layer stack.

According to still another exemplary embodiment of the invention, a method of operating a component carrier having the above-mentioned fea- tures is provided, wherein the surface layer is arranged without physical contact (in particular with a gap in between) to an external heat source, in particular a moving body (such as a hot machine part) or the sun, providing thermal energy to be absorbed.

According to still another exemplary embodiment of the invention, a component carrier having the above-mentioned features is used as at least one of the group consisting of an energy harvesting device (i.e. a device for generating electric energy based on thermal energy), a thermometer (i.e. a device for measuring temperature, in particular for measuring temperature of the external heat source), a light sensor and a light intensity sensor.

In the context of the present application, the term "component carrier" may particularly denote any support structure which is capable of accommodating one or more components thereon and/or therein for providing mechanical support and/or electrical connectivity. In other words, a component carrier may be configured as a mechanical and/or electronic carrier for components. In particular, a component carrier may be one of a printed circuit board, an organic interposer, and an IC (integrated circuit) substrate. A component carrier may also be a hybrid board combining different ones of the above mentioned types of component carriers.

In the context of the present application, the term "thermoelectric de- vice" or thermoelectric generator may particularly denote a solid state device that converts heat or temperature differences directly into electrical energy through a thermoelectric effect. The thermoelectric effect relates to the direct conversion of heat or temperature differences to electric voltage. Hence, a thermoelectric device may create an electric voltage when there is a tempera- ture difference between opposing sides of the thermoelectric device. Without wishing to be bound to a specific theory, it is presently believed that at atomic scale, an applied temperature gradient causes charge carriers in the material to diffuse from the hot side to the cold side. More specifically, a thermoelectric effect which can be advantageously used in a thermoelectric device may make use of the Seebeck effect which, in turn, denotes the conversion of heat directly into electricity at the junction of different types of (in particular metallic) materials.

According to an exemplary embodiment of the invention, a thermoelec- tric device is completely embedded within an interior of a component carrier so that the thermoelectric device is not exposed to a surface of the component carrier but is fully buried therein. In contrast to this, at least a surface portion of the component carrier Is defined by a simply manufacturable layer-type and preferably continuous or non-perforated heat absorbing and thermally conduc- tive surface structure which is therefore highly prone to be efficiently heated by an external heat source and to forward corresponding thermal energy to the thermoelectric device for the generation of electricity. By completely shielding the thermoelectric device with regard to an environment in an interior of the component carrier, any damage of the sensitive thermoelectric device during operation can be safely prevented, even under harsh conditions, so that high reliability of the component carrier as a whole can be achieved. Furthermore, the manufacture of a corresponding component carrier is very simple, since it is dispensable to form any exterior access to expose a surface of the thermoelectric device. It is sufficient to provide a for instance continu- ous surface layer which accomplishes heat absorption from the environment. Moreover, contaminants (such as moisture causing corrosion, aggressive chemicals which may deteriorate an Interior of the component carrier, dirt or dust which may weaken heat transfer, etc.) can be prevented from entering into an interior of the component carrier up to the thermoelectric device, thereby further increasing reliability. Since the thermal energy may be con- verted at least partially into electric energy, excessive heating of the compo- nent carrier (which may conventionally result in warpage, delam!nation, etc.) may be advantageously prevented, thereby significantly improving thermal management of the component carrier.

In the following, further exemplary embodiments of the component car- rier and the methods will be explained. In an embodiment, the thermoelectric device is embedded within an in- terconnected layer stack comprising the surface layer, at least one electrically insulating layer structure and/or at least one electrically conductive layer structure. In particular, the thermoelectric device may be interconnected with the remaining layer structures by lamination, i.e. the application of thermal energy and/or mechanical pressure.

In an embodiment, the thermoelectric device is a Seebeck element. The thermoelectric device may comprise a metal-metal junction, in particular a metal-metal junction of the group consisting of an iron-bismuth junction, a copper-nickel junction, and a copper-constantan junction. In another embodi- ment, the thermoelectric device is a Peltier element. The thermoelectric device may comprise a semiconductor-semiconductor junction. Such thermoelectric devices can be properly Implemented by embedding them in component carrier material such as resin and copper.

In an embodiment, the surface layer has an absorption coefficient, in particular for at least one of visible light and infrared light, of at least 0.8, in particular at least 0.95. By such a material selection (which may result in a black surface layer) it can be ensured that the surface layer harvests a signifi- cant amount of the thermal energy from the environment.

In an embodiment, the surface layer has a thermal conductivity of at least 1 W/(mK), in particular of at least 50 W/(mK), more particularly of at least 100 W/(mK). When the surface layer is provided with such a high thermal conductivity, the absorbed thermal energy can be conducted with low losses to one main surface of the (preferably sheet-shaped or plate-shaped) thermoelectric element.

In an embodiment, the surface layer comprises at least one of the group consisting of a metal with roughened surface, graphite, diamond, a black coating, carbon nanotubes, and photonic crystals. Such materials combine an extremely high thermal conductivity with a very high absorption capability of thermal energy and electromagnetic radiation in the relevant wavelength range (In particular the optical, infrared, and if desired ultraviolet range). Furthermore, they are compatible with component carrier (in particular printed circuit board, PCB) related materials and manufacturing procedures. In an embodiment, the surface layer is positioned at a surface of a layer stack constituting the component carrier or part thereof. Thus, the surface layer may be interconnected with one or more further electrically conductive layer structures and/or one or more further electrically insulating layer struc- tures of the layer stack, in particular by lamination.

In an embodiment, the surface layer is a continuous layer or a closed layer. Such a surface layer may fully cover, in particular directly (i.e. without any structure in between surface layer and thermoelectric device) or indirectly (i.e. with a structure, such as a heat storage structure, between surface layer and thermoelectric device), a main surface of the thermoelectric device. Such a continuous surface layer may be free of through holes or perforations and may therefore properly shield a surface portion of the component carrier with regard to contaminants such as moisture, chemicals and dirt. Moreover, a continuous layer can be formed with low effort, for instance by bonding, lamination or deposition.

In an embodiment, the thermoelectric device is integrated within and/or on a layer stack constituting the component carrier or part thereof. For example, the thermoelectric device may be placed in a cavity of a cured core or of other PCB material and may be connected thereto by gluing, laminating, etc. This allows to accommodate the thermoelectric device within an interior of the component carrier without extending up to the surface of the component carrier. Thus, the thermoelectric device may be properly protected.

In an embodiment, the thermoelectric device is shaped as a sheet or a plate. With such a shape or geometry, It is possible to embed the thermoelec- trie device by well-known PCB manufacturing procedures such as embedding by lamination.

In an embodiment, the thermoelectric device is at least partly surround- ed (for instance at least at one main surface of the thermoelectric device which opposes another main surface of the thermoelectric device being covered directly or indirectly with the surface layer) by thermally poorly conductive material, in particular material comprising resin and optionally reinforcing fibers (such as prepreg or F 4), of a layer stack constituting the component carrier. For instance, a plate-shaped thermoelectric device may be thermally coupled at one main surface thereof with the properly heat absorb- ing and highly thermally conductive surface layer, and may be thermally coupled at an opposing other main surface with poorly thermally conductive material (in particular having a thermal conductivity of less than 5 W/(mK), more particularly of less than 2 W/(mK), still more particularly of less than 1 W/(mK)) in an interior of the component carrier. By taking this measure, a high temperature difference may be established between the two opposing main surfaces of the thermoelectric device due to the significantly different values of the thermal conductivity and amounts of supplied thermal energy. Thus, the efficiency of such an energy harvesting (and/or temperature meas- uring) component carrier is very high. Conventional component carrier materi- als (such as prepreg or FR4) are properly compatible with the requirements of the thermally poorly conductive material.

In an embodiment, at least part of the surface layer comprises a coating being transparent for electromagnetic radiation to be absorbed. Such a coating may render the exterior surface of the surface layer and hence of the compo- nent carrier even more robust against mechanical load acting thereon during operation. Therefore, the component carrier may be employed also in a harsh environment. At the same time, the transparent property of the coating will not significantly reduce the absorption efficiency of the surface layer.

In an embodiment, the component carrier comprises a heat storage structure, in particular a heat storage layer, arranged between the surface layer and the thermoelectric device for temporarily storing energy from the heated surface layer. By taking this measure, sort of thermal buffer may be sandwiched between the surface layer and the thermoelectric device in form of the heat storage structure. By taking this measure, excessive supply of thermal energy, which the thermoelectric device cannot properly handle, can be prevented. In contrast to this, some amount of the absorbed thermal energy can be stored in the heat storage layer and may be later forwarded to the thermoelectric device for conversion into electricity.

In an embodiment, the heat storage structure comprises or consists of a phase change material. A phase-change material may be denoted as a sub- stance with a high heat of fusion which, melting and solidifying at a certain temperature, is capable of storing and releasing large amounts of energy. Heat is absorbed or released when the material changes from solid state to liquid state, and wee versa. However, other kinds of energy storage structures may be implemented as well (such as a battery, a capacitance, etc.).

The at least one component can be selected from a group consisting of an electrically non-conductive inlay, an electrically conductive inlay (such as a metal inlay, preferably comprising copper or aluminum), a heat transfer unit (for example a heat pipe), an electronic component, or combinations thereof. For example, the component can be an active electronic component, a passive electronic component, an electronic chip, a storage device (for instance a DRAM or another data memory), a filter, an integrated circuit, a signal pro- cessing component, a power management component, an optoelectronic interface element, a voltage converter (for example a DC/DC converter or an AG/DC converter), a cryptographic component, a transmitter and/or receiver, an electromechanical transducer, a sensor, an actuator, a microelectro me- chanical system (MEMS), a microprocessor, a capacitor, a resistor, an induct- ance, a battery, a switch, a camera, an antenna, a logic chip, and an energy harvesting unit. However, other components may be embedded in the compo- nent carrier. For example, a magnetic element can be used as a component. Such a magnetic element may be a permanent magnetic element (such as a ferromagnetic element, an antiferromagnetic element or a ferrimagnetic element, for instance a ferrite core) or may be a paramagnetic element.

However, the component may also be a further component carrier, for exam- ple in a board-in-board configuration. The component may be surface mounted on the component carrier and/or may be embedded in an interior thereof. Moreover, also other components, in particular those which generate and emit electromagnetic radiation and/or are sensitive with regard to electromagnetic radiation propagating from an environment, may be used as component. In an embodiment, the component is electrically coupled to the thermo- electric device so that at least part of generated electric energy is supplyable from the thermoelectric device to the component for providing operation energy to the component (for instance when the latter is embodied as chip or sensor). Thus, an external supply of energy to such a surface mounted or embedded component may be dispensable or may be reduced. In contrast to this, the component carrier may operate autonomously in terms of energy supply, because the generated electric energy may be supplied by the inte- grated thermoelectric device. In other embodiments, operation energy for the component may be supplied partially from the thermoelectric device, and partially from a separate (for instance component carrier internal or compo- nent carrier external) energy supply.

In a preferred embodiment, the component is a sensor, in particular at least one of the group consisting of a temperature sensor, a humidity sensor, an air quality sensor, a chemical sensor, and a luminosity sensor. Other kind of sensors may be implemented as well.

In an embodiment, the sensor comprises a sensing element configured for generating a sensor signal (in particular an electric sensor signal) indicative of a sensor event (for instance light has been switched on) or a sensor param- eter (for instance a concentration of a specific gas in a surrounding of the component carrier) to be sensed and comprises a processing element (such as a processor, for instance a chip) electrically coupled with the sensing element and configured for processing the sensed and supplied sensor signal. An output of the processing element may be the information as to whether the sensor event has occurred or not, or the value of the sensor parameter.

In an embodiment, the sensor comprises a communication unit config- ured for communicating sensed information to a communication partner device of the component carrier. For example, such a communication unit may be an antenna or a communication chip. The communication may be preferably wirelessly, or in another embodiment wire based. By (in particular wirelessly) communicating the result of the sensing to a (component carrier external) communication partner device, the autonomous character of the component carrier can be rendered even more pronounced. In a preferred embodiment, also the operation energy for the communication unit may be provided at least partially from the electric energy generated by the thermoelectric device.

In an embodiment, an electrically conductive layer structure of a layer stack constituting the component carrier is configured for electrically coupling the sensing element and/or the processing element and/or the communication unit. Thus, in particular a wiring structure (for instance composed of patterned metal layers and patterned vertical through connections such as vias, both for instance made of copper) of the component carrier may be used synergistically for signal communication in terms of sensing and communicating the sensor results.

In an embodiment, the surface layer is configured for being heated by at least one of the group consisting of electromagnetic radiation, in particular by at least one of visible light and infrared light, emitted by the external heat source, and a hot external heat source when in contact with or being suffi- ciently neighbored to the surface layer. Thus, the heat transfer may be accomplished by heat radiation and/or heat conduction, optionally also heat convection.

In an embodiment, the component carrier comprises a stack of at least one electrically insulating layer structure and at least one electrically conduc- tive layer structure. For example, the component carrier may be a laminate of the mentioned electrically insulating layer structure(s) and electrically conduc- tive layer structure(s), in particular formed by applying mechanical pressure, if desired supported by thermal energy. The mentioned stack may provide a plate-shaped component carrier capable of providing a large mounting surface for further components and being nevertheless very thin and compact. The term "layer structure" may particularly denote a continuous layer, a patterned layer or a plurality of non-consecutive islands within a common plane.

In an embodiment, the component carrier is shaped as a plate. This contributes to the compact design, wherein the component carrier neverthe- less provides a large basis for mounting components thereon. Furthermore, in particular a naked die as example for an embedded electronic component, can be conveniently embedded, thanks to its small thickness, into a thin plate such as a printed circuit board.

In an embodiment, the component carrier is configured as one of the group consisting of a printed circuit board, and a substrate (in particular an IC substrate).

In the context of the present application, the term "printed circuit board" (PCB) may particularly denote a component carrier (which may be plate-shaped (I.e. planar), three-dimensionally curved (for instance when manufactured using 3D printing) or which may have any other shape) which is formed by laminating several electrically conductive layer structures with several electrically Insulating layer structures, for instance by applying pressure, if desired accompanied by the supply of thermal energy. As preferred materials for PCB technology, the electrically conductive layer structures are made of copper, whereas the electrically insulating layer structures may comprise resin and/or glass fibers, so-called prepreg or FR4 material. The various electrically conductive layer structures may be connected to one another in a desired way by forming through-holes through the laminate, for instance by laser drilling or mechanical drilling, and by filling them with electrically conductive material (in particular copper), thereby forming vias as through-hole connections. Apart from one or more

components which may be embedded in a printed circuit board, a printed circuit board is usually configured for accommodating one or more components on one or both opposing surfaces of the plate-shaped printed circuit board. They may be connected to the respective main surface by soldering. A dielectric part of a PCB may be composed of resin with reinforcing fibers (such as glass fibers).

In the context of the present application, the term "substrate" may particularly denote a small component carrier having substantially the same size as a component (in particular an electronic component) to be mounted thereon. More specifically, a substrate can be understood as a carrier for electrical connections or electrical networks as well as component carrier comparable to a printed circuit board (PCB), however with a considerably higher density of laterally and/or vertically arranged connections. Lateral connections are for example conductive paths, whereas vertical connections may be for example drill holes. These lateral and/or vertical connections are arranged within the substrate and can be used to provide electrical and/or mechanical connections of housed components or unhoused components (such as bare dies), particularly of IC chips, with a printed circuit board or

intermediate printed circuit board. Thus, the term "substrate" also includes ^WIC substrates". A dielectric part of a substrate may be composed of resin with reinforcing spheres (such as glass spheres).

In an embodiment, the at least one electrically insulating layer structure comprises at least one of the group consisting of resin (such as reinforced or non-reinforced resins, for instance epoxy resin or Bismaleimide-Triazine resin, more specifically FR-4 or FR-5), cyanate ester, polyphenylene derlvate, glass (in particular glass fibers, multi-layer glass, glass-like materials), prepreg material, polyimide, polyamide, liquid crystal polymer (LCP), epoxy-based Build-Up Film, polytetrafluoroethylene (Teflon), a ceramic, and a metal oxide. Reinforcing materials such as webs, fibers or spheres, for example made of glass (multilayer glass) may be used as well. Although prepreg or FR4 are usually preferred, other materials may be used as well. For high frequency applications, high-frequency materials such as polytetrafluoroethylene, liquid crystal polymer and/or cyanate ester resins may be implemented in the component carrier as electrically insulating layer structure.

In an embodiment, the at least one electrically conductive layer struc- ture comprises at least one of the group consisting of copper, aluminum, nickel, silver, gold, palladium, and tungsten. Although copper is usually preferred, other materials or coated versions thereof are possible as well, in particular coated with supra-conductive material such as graphene.

In an embodiment, the component carrier is a laminate-type component carrier. In such an embodiment, the component carrier is a compound of multiple layer structures which are stacked and connected together by apply- ing a pressing force, if desired accompanied by heat.

The aspects defined above and further aspects of the invention are ap- parent from the examples of embodiment to be described hereinafter and are explained with reference to these examples of embodiment.

Figure 1 illustrates a component carrier according to an exemplary embodiment of the invention.

Figure 2A Illustrates a cross-sectional view, Figure 2B illustrates a plan view, and Figure 2C illustrates a schematic overview of a component carrier with power autonomous sensor function according to an exemplary embodiment of the invention.

Figure 3 illustrates how the component carrier according to Figure 2A to Figure 2C is implementab!e in combination with a moving external heat source.

Figure 4 schematically illustrates cooperation of surface layer and thermoelectric device of a component carrier according to an exemplary embodiment of the invention.

Figure 5 shows an experimental set up for a proof of principle of a component carrier with integrated power harvesting arrangement according to an exemplary embodiment of the invention.

Figure 6 shows the function of a thermoelectric device of a component carrier according to an exemplary embodiment of the invention.

Figure 7 is a diagram illustrating the dependency of temperature difference and output power of a thermoelectric device of a component carrier according to an exemplary embodiment of the invention.

Figure 8 illustrates an arrangement of a component carrier according to an exemplary embodiment of the invention in combination with an external heat source in the context of a temperature measurement application.

The illustrations in the drawings are schematic. In different drawings, similar or identical elements are provided with the same reference signs.

Before, referring to the drawings, exemplary embodiments will be de- scribed in further detail, some basic considerations will be summarized based on which exemplary embodiments of the invention have been developed.

According to an exemplary embodiment, a component carrier with an integrated thermoelectric device is provided which can be used as a light energy harvesting device, a thermometer, a light sensing sensor and/or a light intensity sensor. Such a component carrier, which may be based on PCB technology, may for instance be used to power an autonomous sensor system. In different embodiments, it is possible to implement such a component carrier as energy harvester and/or thermometer.

Autonomous sensor systems are highly advantageous for many applications, for example concerning industry 4.0 applications, automotive applications and aerospace applications. According to sensor-based embodiments of the invention, the sensing of very different parameters is possible, such as temperature, humidity, air quality, chemicals, luminosity conditions, etc. Since exemplary embodiments of the invention make it possible to render component carrier based sensor systems autonomous, it may be possible to simplify presently complicated design constructions where unnecessary wiring Is used, to reduce weight in automotive and aerospace products, etc.

Conventionally, a main drawback of sensor systems Is the necessity to empower such remote devices. Batteries can provide energy to small systems for a long time (for example watches). Possible problems in terms of batteries as power source are however the increase of weight for the end application, the need of battery replacement, the risk of fire In the event of battery leakage, environmental pollution, etc. In particular for sensor systems, or the like, that require relative small amounts of energy, exemplary embodiments of the invention may be implemented In which operation energy can be provided by a component carrier integrated energy harvesting technique.

An idea of an exemplary embodiment of the invention is the provision of a compact component carrier-based system, in particular PCB- (printed circuit board) based system, that can absorb energy in form of light and/or heat and convert it into electricity. This generated electricity can be used for powering one or more electrical systems (such as one or more surface mounted and/or embedded components) being installed In and/or on the same component carrier. The energy is converted into heat by the absorbing structure. The light and/or heat will subsequently be converted into electricity by one or more embedded thermoelectric elements.

The physical principle realized by a PCB integrated thermoelectric element according to an exemplary embodiment of the invention is the conversion of absorbed light into thermal energy and then into electricity. Highly advantageously, the thermoelectric device fully embedded within the component carrier may be free of any mechanical contact to the heat source in order to convert heat energy into electricity. In exemplary embodiments of the invention, it may become possible to use a component carrier (in particular PCB) area to absorb heat energy in form of light in order to harvest energy from highly illuminated environments (such as airplanes, building tops, etc.). Thus, an advantageous measure which may be taken according to an exemplary embodiment of the invention is the integration of a native energy harvester in form of one or more thermoelectric devices directly in the body of the component carrier (in particular PCB) or package. Consequently, an energy harvester being fully integrated to a package can be obtained. For example it is possible that such an energy harvester is fully or substantially fully made out of PCB material, such as FR4 and copper.

Exemplary applications of component carriers according to exemplary embodiments of the invention are autonomous sensors, wearables, remote sensors and/or actuators, machine monitoring, communication, smart integrated systems, etc.

Exemplary embodiments of the invention may allow to meet the demand for sensor systems that are autonomous and, for this reason, can be used remotely to monitor different applications (such as engines, plants, manufacture machines, health applications, wearables, etc.). For the realization of corresponding component carriers, the integration of an energy harvesting system into the packaging is highly advantageous. Exemplary embodiments of the invention may correspondingly add an additional energy harvesting functionality to a component carrier. Besides, an autonomous energy harvester integrated as a thermoelectric device in a component carrier such as a PCB can be used in virtually any sensing system where small amounts of energy are sufficient.

Figure 1 illustrates a cross-sectional view of a component carrier 100, which is here embodied as printed circuit board (PCB), according to an exemplary embodiment of the invention. The component carrier 100 according to Figure 1 is configured as a fully autonomous sensor system with energy harvesting capability to thereby generate the operation energy of the component carrier 100 by itself.

The component carrier 100 comprises a highly heat absorbing (for instance black) and highly thermally conductive surface layer 102 arranged on an exterior surface of the component carrier 100. In the shown embodiment, the surface layer 102 is a double layer composed of a graphite layer 177 covered by a thin optically and infrared transparent coating 114 with high robustness, for instance an appropriate varnish. The surface layer 102, in particular the graphite layer 177 thereof, is configured for being heated by an external heat source 104, in the shown embodiment the schematically illustrated sun. The thermal conductivity of the graphite layer 177 (for instance embodied as Pyrolytic Highly Oriented Graphite Sheet) may be several hundred or even more than thousand W/mK. Furthermore, the material of the graphite layer 177 has a high absorption coefficient for optical and infrared light. Consequently, a significant amount of the thermal energy from the heat source 104 impinging on the surface layer 102 will be absorbed by the latter. As shown in Figure 1, the surface layer 102 may be arranged without physical contact to the external heat source 104 for providing thermal energy to be absorbed.

As can be furthermore taken from Figure 1, the component carrier 100 additionally comprises a thermoelectric device 106 which is fully embedded or built in within material of the component carrier 100 without surface access, so that the thermoelectric device 106 does not form part of an exterior surface of the component carrier 100. In contrast to this, the thermoelectric device 106 is buried and fully shielded by material of the component carrier 100 with regard to an environment. Thereby, It is safely prevented that the sensitive thermoelectric device 106 is mechanically damaged during operation of the component carrier 100. Furthermore, corrosive moisture, aggressive chemicals and thermally insulating dust or dirt can be prevented from negatively influencing the thermoelectric device 106. Therefore, a highly reliable component carrier 100 with a high lifetime may be obtained. In addition, the continuous surface layer 102 can be applied easily and needs not be processed (for instance patterned) for accessing the thermoelectric device 106.

As can be taken from Figure 1, the thermoelectric device 106 is thermally coupled with the surface layer 102 via an optional intermediate heat storage structure 116 which will be described below in further detail. The thermoelectric device 106 is configured for transferring thermal energy supplied by the heated surface layer 102 into electric energy. In terms of manufacturing the component carrier 100, the thermoelectric device 106 may be fully surrounded by material of (in particular embedded or built in within) the interconnected layer stack 108 comprising the surface layer 102, a plurality of electrically insulating layer structures 110 (such as layers of prepreg) and a plurality of electrically conductive layer structures 112 (such as copper structures). Stack 108 may be interconnected for Instance by lamination, i.e. the application of thermal energy and/or heat.

The plate-like thermoelectric device 106 may be a Seebeck element (implementing for instance a copper-nickel junction) or a Peltier element (implementing for instance a semiconductor-semiconductor junction).

Advantageously, at least a part of a lower main surface and of side surfaces of the thermoelectric device 106 is surrounded by thermally poorly conductive material in form of prepreg or FR4 of the layer stack 108. In contrast to this, an upper main surface of the thermoelectric device 106 is thermally coupled to the highly thermally conductive material of the surface layer 102. By taking this measure, a high temperature difference may be established between the upper main surface and the lower main surface of the thermoelectric device 106, therefore allowing for a very efficient conversion of thermal energy into a significant amount of electric energy (such as an electric voltage).

As already mentioned above, the component carrier 100 comprises a layer-type heat storage structure 116 (which is here embodied as a layer of phase change material) sandwiched between the surface layer 102 and the thermoelectric device 106. The heat storage structure 116 is capable of temporarily storing excessive amount of heat (or corresponding energy) generated in the surface layer 102. Thus, such energy may be buffered in the heat storage structure 116 before supplying this energy to the thermoelectric device 106. This further increases reliability of the operation of the component carrier 100, since a heat overflow in the thermoelectric device 106 may be safely prevented.

As can be taken from Figure 1 as well, the component 100 comprises a stack of three components 118 which are all embedded in the component carrier 100, for instance may be laminated together with the layer stack 108. Although shown only schematically in Figure 1, the components 118 are electrically coupled to the thermoelectric device 106 via electrically conductive layer structures 112 so that generated electric energy can be conducted from the thermoelectric device 106 to the components 118 for providing operation energy to the components 118.

In the shown embodiment, the components 118 form part of a chemical sensor system. This sensor system comprises a chemical sensing element 120 (for instance a semiconductor chip with the capability of sensing a certain chemical in an environment of the component carrier 100) as a first one of the components 118 on an exterior surface of the component carrier 100. The chemical sensing element 120 is configured for generating a sensor signal indicating the value of this chemical as sensor parameter. The chemical sensing element 120 is electrically and communicatively coupled with a processing element 122 (for instance a further semiconductor chip serving as processing resource) as a second one of the components 118 and is configured for processing the sensor signal. In other words, the processing element 122 may retrieve the value of the sensor parameter from the sensor signal. Moreover, the sensor system comprises a wireless communication unit 124 (for example yet another semiconductor chip having wireless communication capability) as a third one of the components 118. The wireless communication unit 124 is electrically and communicatively coupled with the processing element 122 and is supplied with the retrieved value of the sensor parameter by the processing element 122. The wireless communication unit 124 is further configured for wirelessly communicating this sensor information to a communication partner device (not shown in Figure 1).

According to Figure 1, the various components 118 are coupled to one another via directly connected pads 191. Additionally or alternatively, the electrically conductive layer structures 112 (such as patterned metal foils and metal filled vias) of the layer stack 108 may be configured for electrically coupling the sensing element 120, the processing element 122 and the communication unit 124 with one another.

Figure 2A illustrates a cross-sectional view, Figure 2B illustrates a plan view, and Figure 2C illustrates a schematic overview of a component carrier 100 with power autonomous sensor function according to an exemplary embodiment of the invention. The component carrier 100 according to Figure 2A to Figure 2C is a PCB- based energy harvesting packaging module which should preferably have a large area to be exposed to light sources, in the shown embodiment the sun, as external heat source 104. The PCB-type component carrier 100 can be associated to light absorbing materials such as black coatings, carbon nanotubes, quantum dots, photonic crystals, graphite, etc. as a surface layer 102 that can absorb for example up to 99% of incident light 165 produced by the external heat source 104. In these materials, the incident light 165 is basically converted into heat. Consequently, the PCB system carrying the black coating in form of the surface layer 102 experiences an increase in temperature. Micro thermoelements forming the thermoelectric device 106 are used to convert the thermal energy into electricity to be supplied to an electrical system (see components 118) contained Into and/or onto the PCB- type component carrier 100. Such thermoelectric devices 106 may also be embedded or native in the PCB. The device depicted in Figure 2A and Figure 2C is hence capable of converting visible and infrared radiation into electricity and to operate autonomously. The PCB-body, see layer stack 108, is the mechanical support and the encapsulation of the electrical system. The black surface of the PCB (i.e. the surface layer 102 of the component carrier 100) is operable for absorbing and converting the energy and empowering a remote sensor system (see reference numerals 120, 122, 124). The thermoelectric device 106 is connected to the remote sensor system via copper vias 167. The remote sensor system may be composed by at least one sensing element 120, at least one signal processing element 122 and at least one communication unit 124 for wirelessly communicating with a communication partner device 126 (for instance a central unit) by emission of electromagnetic (Wi-Fi or RF, for example) or mechanical (infrasound or ultrasound, for example) waves 169. Thus, the processed signal is sent via radio electromagnetic waves or mechanical waves 169 to the communication partner device 126, where the sensed data may be compiled. The operation during periods of darkness can be assured by the addition of energy storing materials in form of the heat storage structure 116 (such as phase change material, one or more electrical capacitors or a battery). The operational principle of the thermoelectric device 106 relies on a temperature difference between its two opposing main surfaces. This is guaranteed by the almost thermally insulating FR4 and prepeg materials of electrically insulating layer structure HO that encloses a bottom portion of the thermoelectric device 106.

Advantageously, no direct contact between the component carrier 100 and the external heat source 104 is needed. Even without such a direct contact, the component carrier 100 can absorb heat also from moving parts (for example turbines, motors, etc.) and/or remote bodies (for instance sunlight). Alternatively, the component carrier 100 can also be activated in a contact mode.

Figure 2C illustrates communication partner device 126 as central unit being communicatively coupled with a plurality of component carriers 100 of the type shown in Figure 2A and Figure 2B forming a distributed sensing network.

Figure 3 illustrates how the component carrier 100 according to Figure

2A to Figure 2C is implementable in combination with a moving external heat source 104, in the shown embodiment a turbine. Infrared thermal energy originating from the external heat source 104 and reaching the surface layer 102 of the component carrier 100 generates electrical energy used for self- empowering sensor system 120, 122, 124, for Instance to measure temperature of the moving external heat source 104.

Figure 4 schematically illustrates cooperation of surface layer 102 and thermoelectric device 106 of a component carrier 100 according to an exemplary embodiment of the invention for creation of an electric voltage V. Reference 400 indicates incoming heat, for instance infrared thermal energy coming from a turbine.

Figure 5 shows an experimental set up for a proof of principle of a component carrier 100 with integrated power harvesting arrangement according to an exemplary embodiment of the invention.

Figure 5 shows the schematics and the setup of an experiment ran in applicant's laboratory to qualitatively differentiate the light absorption between common materials in a PCB. Figure 5 shows the results for different materials, i.e. the temperature of the illuminated samples at steady-state. In Figure 5, reference numeral 206 is the material that is absorbing heat from an external source 200. The external source 200 is a 150W infrared lamp that was placed 1,5 cm away from the sample (i.e. material 206) in order to achieve sufficiently high temperatures quickly. Reference numeral 202 represents the infrared light rays that heated the sample (i.e. material 206). The temperature of the heated surface (compare reference numeral 206) at steady state was measured by a thermometer 204. This experiment was carried out with the following materials 206:

a) PGS (Pyrolytlc Graphite Sheet, 25 μm) embedded in LCP (Liquid Crystalline Polymer) laminated with copper on the surface (rough copper), b) the same sample as in a) without any copper,

c) FR4

d) 100 μm copper foil (rough surface)

e) 100 μm copper foil (polished surface)

All five materials 206 were significantly warmed up by the source 200 due to the small distance to it. Note that the samples containing rough copper and apparent PGS showed the best results. That can be explained by the high infrared absorption rates of these structures, Such structures showed a temperature increase (i.e. heat absorption) of about 20% better than FR4, about 30% better than rough copper and more than two times better than polished copper. Further, convection played a major role in lowering the steady state temperatures of the hottest samples since the lab temperature was only 24°C. This can be improved by encapsulating the light absorbing structures with transparent materials (preferably thermally insulating, to suppress convection). This experiment emulates how exemplary embodiments of the invention can be used specially close to hot structures such as moving motor parts, airplane turbines (see Figure 4), melting metals, cooking meals, chemical reactions, etc., where the heat dissipation energy can be harvested without any mechanical contact.

Figure 6 shows the function of a thermoelectric device 106 (with dimensions smaller than 1mm³) of a component carrier 100 according to an exemplary embodiment of the invention. When the thermoelectric device 106 is placed between a hot reservoir 210 and a cold reservoir 212, electrical power is output, see reference numeral 214.

Figure 7 is a diagram 700 illustrating the dependency of temperature difference (plotted along an abscissa 702) and output power (plotted along an ordinate 704 of a thermoelectric device 106 of a component carrier 100 according to an exemplary embodiment of the invention. Thus, Figure 7 illustrates the calculated maximum power versus temperature difference.

Figure 6 and Figure 7 relate to thermoelectric devices 106 which may be used according to exemplary embodiments of the invention to convert thermal power absorbed by the PCB into electric energy. The dimensions of the thermoelectric device 106 according to Figure 6 allow these thermoelectric devices 106 to be embedded in a PCB. Figure 7 shows the efficiency on energy conversion of these thermoelectric devices 106. Another possibility is the production of thermoelectric devices 106 in the PCB with metal-metal junction devices (exploiting the Seebeck effect). This can be realized by applying layers of iron and bismuth, for example, in the build-up of the PCB. In an exemplary embodiment, the Seebeck thermoelement can be build up using metals that are commons in the PCB construction, i.e. copper and nickel. An efficient Seebeck thermoelement can be built with the combination of copper and constantan (i.e. an alloy of 55% copper and 45% nickel).

Figure 8 illustrates an arrangement of a component carrier 100 according to an exemplary embodiment of the Invention in combination with an external heat source 104. The embodiment according to Figure 8 relates to the application of a wireless thermometer or light intensity detector.

Hence, Figure 8 describes how a component carrier 100 according to an exemplary embodiment of the invention can be used, for example, as a contactless thermometer. The component carrier 100 is placed in the surrounding of the heat source 104 (for instance a heat emitting engine, moving part, melting metal, etc.), which generates infrared radiation (see reference numeral 400). The infrared radiation is absorbed by the heat absorption unit, i.e. the surface layer 102, and is converted into a temperature increase (up to T₁). A resulting temperature gradient through the component carrier 100 generates electric power in the thermoelement or thermoelectric device 106. The temperature on the back side of the thermoelectric device 106 is monitored or even controlled with a thermometer (see control temperature unit 800 at temperature To). This thermometer can be a simple thermocouple or temperature dependent resistor. The harvested energy is used to send the readings of the temperature or to empower any other sensor unit, depending on the case. The temperature of the heat generating part, i.e. heat source 104, can be calculated (for instance using the modified Stefan-Boltzmann equation, i.e. P=εfε_thσ(T₁ ⁴-T₀ ⁴), where the terms ε_th and Br are related to the efficiencies of the thermoelement and of the infrared absorbing film, respectively; P is the power, and σ is the Stefan-Boltzmann constant).

In the same fashion, the device described in Figure 8 can be used as a light detector and luminosity sensor. The reading is done simply by knowing T₁ and To (which can be monitored by conventional thermometers) in the modified Stefan-Boltzmann equation. The reading of the power will indicate the light intensity that reaches the surface layer 102 of the device.

It should be noted that the term "comprising" does not exclude other el- ements or steps and the "a" or "an" does not exclude a plurality. Also ele- ments described in association with different embodiments may be combined.

It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.

Implementation of the invention is not limited to the preferred embodi- ments shown in the figures and described above. Instead, a multiplicity of variants are possible which use the solutions shown and the principle accord- ing to the invention even in the case of fundamentally different embodiments.

Claims

Claims:

1. A component carrier (100), comprising:

a heat absorbing and thermally conductive surface layer (102) config- ured for being heated by an external heat source (104);

a thermoelectric device (106) fully surrounded by material of the com- ponent carrier (100), thermally coupled with the surface layer (102) and configured for transferring thermal energy of the heated surface layer (102) into electric energy.

2. The component carrier (100) according to claim 1, wherein the ther- moelectric device (106) is embedded within an interconnected layer stack ( 108) comprising the surface layer (102), at least one electrically insulating layer structure (110) and/or at least one electrically conductive layer structure (112).

3. The component carrier (100) according to claim 1 or 2, wherein the thermoelectric device (106) is a Seebeck element and/or comprises a metal- metal junction, in particular a metal-metal junction of the group consisting of an iron-bismuth junction, a copper-nickel junction, and a copper-constantan junction.

4. The component carrier (100) according to claim 1 or 2, wherein the thermoelectric device ( 106) is a Peltier element and/or comprises a semicon- ductor-semiconductor junction.

5. The component carrier (100) according to any of claims 1 to 4, wherein the surface layer (102) comprises a material which has an absorption coeffi- cient, in particular for at least one of visible light and infrared light, of at least 0.8, in particular at least 0.95.

6. The component carrier (100) according to any of claims 1 to 5, wherein the surface layer (102) comprises a material which has a thermal conductivity of at least 1 W7(mK), in particular of at least 50 W/(mK), more particularly of at least 100 W/(mK).

7. The component carrier (100) according to any of claims 1 to 6, wherein the surface layer (102) comprises at least one of the group consisting of a metal with roughened surface, graphite, diamond, a black coating, carbon nanotubes, and photonic crystals.

8. The component carrier (100) according to any of claims 1 to 7, wherein the surface layer (102) is positioned at a surface of an interconnected layer stack (108).

9. The component carrier (100) according to any of claims 1 to 8, wherein the surface layer (102) is a continuous layer or a closed layer, in particular fully covering, more particularly directly or indirectly, one main surface of the thermoelectric device (106).

10. The component carrier (100) according to any of claims 1 to 9, wherein the thermoelectric device (106) is integrated within an interconnected layer stack (108).

11. The component carrier (100) according to any of claims 1 to 10, wherein the thermoelectric device ( 106) is shaped as a sheet or plate, in particular rigid or flexible.

12. The component carrier (100) according to any of claims 1 to 11, wherein the thermoelectric device ( 106) is partly surrounded by thermally poorly conductive material, in particular by material comprising resin, such as prepreg or FR4.

13. The component carrier (100) according to any of claims 1 to 12, wherein an exposed part of the surface layer ( 102) comprises a coating (114) being transparent for electromagnetic radiation to be absorbed.

14. The component carrier (100) according to any of claims 1 to 13, com- prising a heat storage structure (116), in particular a heat storage layer, arranged between, in particular directly between, the surface layer (102) and the thermoelectric device (106) and being configured for temporarily storing energy from the heated surface layer (102).

15. The component carrier (100) according to claim 14, wherein the heat storage structure (116) comprises or consists of a phase change material.

16. The component carrier (100) according to any of claims 1 to 15, further comprising at least one component (118) mounted on and/or embedded in material of the component carrier (100).

17. The component carrier (100) according to claim 16, wherein the at least one component (118) is electrically coupled to the thermoelectric device (106) so that at least part of generated electric energy is supplyable from the thermoelectric device (106) to the at least one component (118) for providing operation energy to the at least one component.

18. The component carrier (100) according to claim 16 or 17, wherein the at least one component (118) is selected from a group consisting of an electronic component, an electrically non-conductive and/or electrically conductive inlay, a heat transfer unit, an energy harvesting unit, an active electronic compo- nent, a passive electronic component, an electronic chip, a storage device, a filter, an integrated circuit, a signal processing component, a power manage- ment component, an optoelectronic interface element, a voltage converter, a cryptographic component, a transmitter and/or receiver, an electromechanical transducer, an actuator, a microelectromechanical system, a microprocessor, a capacitor, a resistor, an inductance, an accumulator, a switch, a camera, an antenna, a magnetic element, a further component carrier and a logic chip.

19. The component carrier (100) according to claim 16 or 17, wherein the at least one component (118) comprises a sensor, in particular at least one of the group consisting of a temperature sensor, a humidity sensor, an air quality sensor, a chemical sensor, and a luminosity sensor.

20. The component carrier (100) according to claim 19, wherein the sensor comprises a sensing element (120) configured for generating a sensor signal, indicative of a sensor event or a sensor parameter to be sensed, and compris- es a processing element (122) electrically coupled with the sensing element (120) and configured for processing the sensor signal.

21. The component carrier (100) according to claim 19 or 20, wherein the sensor comprises a communication unit (124) configured for communicating, in particularly wirelessly communicating, sensed information to a communica- tion partner device (126).

22. The component carrier (100) according to claim 20 or 21, wherein an electrically conductive layer structure ( 112) of a layer stack (108) of the component carrier (100) is configured for electrically coupling the sensing element (120) with the processing element (122) and/or the communication unit (124) with at least one of a sensing element (120) and a processing element (122).

23. The component carrier (100) according to any of claims 1 to 22, wherein the surface layer ( 102) is configured for being heated by at least one of the group consisting of electromagnetic radiation (165), in particular by at least one of visible light and infrared light, emitted by the external heat source (104), and a hot external heat source (104) when in contact with or neigh- bored to the surface layer (102).

24. The component carrier (100) according to any of claims 1 to 23, com- prising a stack (108), in particularly a laminated stack (108), of at least one electrically conductive layer structure (112) and/or at least one electrically insulating layer structure (110).

25. The component carrier (100) according to any of claims 1 to 24, wherein the at least one electrically conductive layer structure (112) comprises at least one of the group consisting of copper, aluminum, nickel, silver, gold, palladi- um, and tungsten, any of the mentioned materials being optionally coated with supra-conductive material such as graphene.

26. The component carrier (100) according to any of claims 1 to 25, wherein the at least one of the electrically insulating layer structure (110) comprises at least one of the group consisting of resin, in particular reinforced or non- reinforced resin, for instance epoxy resin or Bismaleimide-Trlazine resin, FR-4, FR-5, cyanate ester, polyphenylene derivate, glass, prepreg material, polyi- mide, polyamide, liquid crystal polymer epoxy-based Build-Up Rim, polytetra- fluoroethylene, a ceramic, and a metal oxide.

27. The component carrier (100) according to any of claims 1 to 26, wherein the component carrier (100) is shaped as a plate.

28. The component carrier (100) according to any of claims 1 to 27, wherein the component carrier (100) is configured as one of the group consisting of a printed circuit board, and a substrate,

29. The component carrier (100) according to any of claims 1 to 28, config- ured as a laminate-type component carrier (100).

30. A method of manufacturing a component carrier (100), the method comprising :

interconnecting a layer stack (108) comprising a heat absorbing and thermally conductive surface layer (102) which is arranged at a surface of the layer stack ( 108) for being heatable by an external heat source (104); thermally coupling a thermoelectric device (106) with the surface layer (102) for transferring thermal energy of the heated surface layer (102) into electric energy; and

fully surrounding the thermoelectric device (106) by material of the lay- er stack (108).

31. The method according to claim 30, wherein at least one of the surface layer (102) and the thermoelectric device (106) is interconnected within the layer stack (108) by laminating.

32. A method of operating a component carrier (100) according to any of claims 1 to 29, wherein the surface layer (102) is arranged without physical contact to an external heat source (104), in particular a moving body or the sun, providing thermal energy to be absorbed by the surface layer (102).

33. A method of using a component carrier ( 100) according to any of claims 1 to 29 as at least one of the group consisting of an energy harvesting device, a thermometer, a light sensor and a light intensity sensor.