Electronic module and cooling system therefor

Abstract

The invention relates to an electronic module and to a cooling system therefor, which is improved with regard to the cold chain. The invention makes it possible for the first time to integrate a cooling system into an electronic module. The cooling system cools directly without hindering heat transfer within a cold chain, substantially uses the existing components of the module, reduces their number and integrates an additional function merely by integrating piezoelectric material.

Description

[0001] Description

[0002] Electronic module and cooling system

[0003] The invention relates to an electronic module which, when in operation, has a heat density of 1 W / cm 2 Heat dissipation is shown, in particular a new type of cooling system which is improved with regard to the cold chain.

[0004] The term “power electronics” or “electronic module” refers to everything that has to do with the control, conversion, or switching of electrical energy using electronic semiconductors and / or semiconductors, such as chips. This starts at just a few hundred milliamps and a few volts, but goes up to several tens of kilovolts and several thousand amps. Electronic modules enable the conversion of electrical energy in terms of its voltage form, the level of voltage and current, and the frequency. In electric drive technology, the operating points of electrical machines can be set very flexibly using the control options offered by electronic modules. Today, even large machine drives and / or electric locomotives are equipped with electronic modules for control purposes.

[0005] Electronic modules are also becoming increasingly popular in energy generation and / or transmission. In lower-power systems or systems with conditions where the traditional synchronous generator cannot be used as a power generator, electronic modules are used as frequency converters to feed the generated electrical energy into the power grid.

[0006] Electronic modules are also becoming increasingly important in the automotive sector. Here, a wide variety of electrical devices are switched and controlled using electronic modules.

[0007] Cooling, or rather waste heat dissipation, from electronic modules is a very important topic and affects not only the efficiency and / or speed of the electronic modules, but also their service life. In particular, electronic modules that are circuits, such as HVDC "high-voltage direct current transmission" back-to-back couplers and / or converters, very high waste heat densities of several watts per cm2 are generated, which are complex to cool and dissipate. In addition to oversized heat sinks, fans, various types of heat spreaders and thermal interface materials are often used. The result of using this modular system is a construction that is sometimes costly and, in terms of cooling results, often unsatisfactory and not permanently reliable. This construction has been used more or less unchanged for over 40 years due to a lack of technical alternatives and dependence on suppliers.

[0008] The conventional standard components for cooling electronic modules are thermal paste and metallic coolers. The thermal paste is responsible for thermally connecting the cooler to the semiconductor or chip of the electronic module, while the heat sinks, particularly metallic heat sinks made of aluminum and / or copper, perform the next step in the cooling chain: increasing the surface area.

[0009] However, heat flow in the cooling chain is disrupted at the transition from the thermal paste to the metallic heat sink, because thermal pastes have thermal conductivities in the range of 1 to 7 W / mK, while the subsequent metals have approximately 50 times this. Thus, there is always the risk of heat buildup in the thermal paste, and this is traditionally solved with convection and / or increasingly larger heat sinks. In the development of power electronics, space requirements and weight are important criteria, in addition to functionality and efficiency.

[0010] The economically and technically viable solutions are always the more compact ones. Therefore, the systems currently used to cool power electronics are not optimal, and there is a need for new, space-saving cooling systems for electronic modules.

[0011] In addition, many current systems for cooling electronic modules end with the transfer of waste heat from a metal cooler to the ambient air. The factors that determine the potential heat transfer rate of this final cooling step include, in addition to the temperature of the cooling air, which can usually only be influenced to a limited extent, and above all, the airflow velocity and the pressure difference generated by the fan. This is generally rather small, so that mechanical fans, in addition to their actual function of moving air, also have to meet requirements regarding longevity, power consumption, and self-heat production.Accordingly, it is an object of the present invention to provide an electronic module with a compact and efficient cooling system which overcomes the disadvantages of the prior art, in particular with regard to the different thermal conductivities within the cold chain and / or with regard to the compactness and space requirements of the cold chain of electronic modules.

[0012] This object is achieved by the subject matter of the present invention as disclosed in the claims, the description and the figures.

[0013] Accordingly, the subject matter of the invention is an electronic module comprising at least one frame and a semiconductor for controlling, regulating and / or switching electrical currents and voltages, wherein at least one element such as the semiconductor is present as a piezo actuator, by means of which an element of the electronic module is set into oscillation and / or vibration for cooling by ambient air when current flows by utilizing the inverse piezoelectric effect.

[0014] Piezoelectric semiconductors are either made of piezoelectric materials and / or coupled with piezoelectric material. Piezoelectric material can be present, for example, in the form of a coating or a partial coating.

[0015] Piezoelectric materials include, for example, all ferroelectric materials and materials with a permanent electric dipole. For example, barium titanate and lead zirconate titanate (PZT) are frequently used piezoelectric materials. But piezoelectric materials also occur in the form of piezoelectric thin films, piezoelectric polymers, lead-free inorganic piezoelectric particles and / or crystals, as well as in the form of metals. Piezoelectric crystals are crystals with polar axes but without a center of symmetry. These include, for example, α-quartz, liquid crystals, tourmaline, Seignette salt, zinc sulfide, and cane sugar. Of the 32 known crystal classes in solid-state physics, 20 allow piezoelectricity in principle because they have polar symmetry.

[0016] The piezoelectric material can, for example, be combined with the semiconductor to form the piezoelectric semiconductor, in which piezo crystals are formed and / or deposited on the carrier, e.g., a wafer. The wafer, which forms the chip because, for example, integrated circuits are arranged on it, thus serves not only as a carrier for the conductor tracks that form the circuits, but also as a carrier for the piezo crystals.

[0017] Piezo actuators utilize the inverse piezoelectric effect; they are made of piezoelectric material and convert electrical energy directly into mechanical energy, enabling movements in the sub-nanometer range.

[0018] According to an advantageous embodiment, the semiconductor is piezoelectric.

[0019] Using semiconductor technology, it is possible to deposit active piezoelectric thin films on silicon. These include, for example, zinc oxide (ZnO) and / or aluminum nitride (AIN).

[0020] According to an advantageous embodiment, the semiconductor has one or more piezo actuators in addition to the control and circuit elements on a common semiconducting substrate, for example a chip and / or a circuit board.

[0021] According to a further advantageous embodiment, one or more piezo actuators are fixed to the semiconductor by bonding.

[0022] The term "bonding" is used as an umbrella term for various connection processes in assembly and connection technology. Wire bonding refers to the wiring of an integrated circuit or a discrete semiconductor with the electrical connections of other components or the package.

[0023] According to an advantageous embodiment of the electronic module, a stack of semiconductors is realized in a frame with a multi-layer stack construction.

[0024] In this way, several thin piezo semiconductor elements can be combined with electrodes in between. This results in a mechanical series arrangement controlled by an electrical parallel circuit.

[0025] The holding frame is preferably made of plastic and dielectric.

[0026] In the following, the invention is explained in more detail with reference to two figures which show exemplary embodiments of the invention:

[0027] Figure 1 shows a cross section through an embodiment of the invention in which piezoelectric semiconductors or chips are arranged and fixed freely oscillating, alternating right and left within a frame.

[0028] Figure 2 shows a cross section through another exemplary embodiment of the invention, in which the piezoelectric semiconductors, or chips, are held in the frame on two sides, whereby a standing wave results upon piezoelectric excitation.

[0029] Figure 1 shows an electronic module 1 with three piezoelectric semiconductors 4 and 6 on each side.

[0030] The individual piezoelectric semiconductors 4 and 6 - also called "chips" - are each attached alternately to a right part 2 and left part 3 of a frame element. In the two shown parts 2 and 3 of the frame element, for example, electrical contacts and connecting lines to and from the piezoelectric semiconductors 4 and 6 are accommodated. For the sake of clarity, these contacts are also not shown individually, but a person skilled in the art will know how such connections, contacts, connections and / or wiring run in frame elements and are connected to the piezoelectric semiconductors 4, 6. During operation of an electronic module, the semiconductors produce heat, which is cooled and dissipated so that the semiconductors do not overheat.

[0031] The piezoelectric semiconductors 4 and 6 , as shown here according to an embodiment of the invention, also produce waste heat, but by utilizing the inverse piezoelectric effect of the chips themselves, i.e. the piezoelectric semiconductors, the piezoelectric semiconductors or chips 4 and 6 are set into oscillation or vibration during operation at the same time as they are heated, so that they generate an air flow 5 .

[0032] The oscillation or vibration of the chips 4 and 6 can be adjusted by the piezoelectric material used, by current density, and / or by suspension from the frame element. The oscillation generates an air flow 5 that flows through the electronic module 1 and thereby cools the parts 2, 3, 4, and 6 that heat up during operation.

[0033] The piezoelectric deflection 7 during the oscillation and / or vibration of the individual piezoelectric semiconductor chips is mainly vertical, i.e. an up and down movement, as indicated in Figure 1 by the short arrows 7.

[0034] Figure 2 shows another exemplary embodiment of the invention, in which the six piezoelectric semiconductors 14 shown here are fixed on both sides of each side 12 and 13 of the frame in an electronic module 10, again comprising frame elements 12 and 13, as well as the contacts provided there. Again, during operation, the piezoelectric semiconductors 14 are firstly undesirably heated, and again, due to the inverse piezoelectric effect, they begin to oscillate, creating an air flow 15.

[0035] In this embodiment 10, in which the piezoelectric semiconductors 14 are located in the airflow within the electronic module, elements 18 for ventilation, such as semi-permeable membranes 18 and / or semi-permeable openings 16 and 19, which are set into oscillation and / or vibration by the piezoelectric excitation, either directly or indirectly by the piezoelectrically generated airflow, can be provided. Through these openings 16 and 19, for example, very effective cross-ventilation can be generated by the airflow 15 in the electronic module 10.

[0036] Excitation of the piezoelectric semiconductor causes it to vibrate and / or oscillate, forming, for example, one or more standing waves. Alternatively, a vibration can also propagate through the piezoelectric semiconductor and be reflected at the attachment point on the frame.

[0037] The present invention proposes for the first time cooling the chip, which is responsible for the waste heat development, using high-frequency oscillation. This means that heat is dissipated directly from the chip and / or a vapor chamber in which the chip is housed, into the air, and some of the heat transfer resistance found in a conventional cold chain is eliminated. Due to the high-frequency movement of the substrate to be cooled, heat transfer to the air is many times better than with conventional blowing via a fan. By combining it with a cold chain, it is possible to achieve higher cooling performance without spreading the surface of the heat source.

[0038] The solution proposed here for a cooling concept for electronic modules, for example via one-sided mounting and / or fixing of a piezoelectric semiconductor and / or an element that either acts as a piezo actuator itself or is set into vibration by the air generated by the piezo actuator, as shown by way of example in Figure 1, can enormously increase the reliability and efficiency of the cooling systems of electronic devices, in particular power electronic devices.

[0039] The same applies to the double-sided mounting of a piezoelectric semiconductor and / or an element that either acts as a piezo actuator itself or is set into vibration by the air generated by the piezo actuator, as shown by way of example in Figure 2. In combination with the introduction of semi-permeable openings in the housing and / or membranes, a directed air volume flow can be achieved even with a smaller deflection. In addition, the use of volume flow-enhancing components, such as polymer film flags mounted on the end of the piezoelectric semiconductor, can further enhance the effect.

[0040] The introduction of the electromechanical and / or piezoelectric properties onto the chip can be carried out using classical semiconductor technology processes analogous to power switch manufacturing, such as sputtering, vapor deposition, physical vapor deposition (PVD) and / or chemical vapor deposition (CVD), and / or subsequently by using generative manufacturing methods, such as AM processes, and / or applying pastes.

[0041] The described invention combines, for the first time, the heat loss associated with the operation of power electronics with heat dissipation and cooling in a single component, the chip. This integration step eliminates interfaces, which in previous cooling solutions have led to a massive deterioration in cooling performance and considerable effort in production and operation.

[0042] By incorporating many cooling elements into an electronic system, it is now possible to have intelligent cooling control which can determine not only the intensity but also the location of the cooling and the direction of the air flow. This cooling is more effective and reliable with less effort. The invention therefore makes it possible for the first time to integrate a cooling system into an electronic module which cools directly, without hindering heat transfer within a cold chain, essentially uses the existing components of the module, possibly reducing their number and simply by integrating piezoelectric material integrates an additional function in the electrical module and / or in particular in the piezoelectric semiconductor. For example, by integrating piezoelectric material, an additional function is integrated into the chip, the circuit board or the piezoelectric semiconductor element.

Claims

Patent claims 1. Electronic module (1,10), at least one frame (2.3.12.13) and a semiconductor (4, 6, 14) for controlling, regulating and / or switching electrical currents and voltages, wherein at least one element such as the semiconductor (4, 6, 14) is present as a piezo actuator (4, 6, 14), by means of which, when current flows, an element of the electronic module (4, 6, 14) is set into oscillation and / or vibration (7, 17) for cooling by ambient air by utilizing the inverse piezoelectric effect.

2. Electronic module (1,10) according to claim 1, which carries out ultrasonic vibrations (7, 17).

3. Electronic module (1,10) according to one of claims 1 or 2, which comprises one or more piezoelectric semiconductors (4, 6) which are fixed to the frame on one side only.

4. Electronic module (1, 10) according to one of claims 1 or 2, comprising one or more piezoelectric semiconductors (14) which are arranged on both sides of the frame (12.13) is / are fixed.

5. Electronic module (1,10) according to one of the preceding claims, which has a piezoelectric semiconductor element which generates movements in the sub-nanometer range.

6. Electronic module (1,10) according to one of the preceding claims, which has openings for ventilation in the frame.

7. Electronic module (1,10) according to one of the preceding claims, which has one or more membranes (18) parallel to the semiconductors.

8. Electronic module (1,10) according to claim 6, wherein the openings in the frame are provided as ventilation openings and are covered by a semi-permeable membrane.

9. Electronic module (1,10) according to one of the preceding claims, wherein one or more elements (18) are provided within the module (10) which amplify the air flow (5, 15) generated by the oscillation and / or vibration (7,17) of the piezoelectric semiconductors (14).

10. Electronic module (1,10) according to one of the preceding claims, which comprises a piezoelectric semiconductor (4, 6, 14) which is at least partly made of piezoelectric material.

11. Electronic module (1,10) according to one of the preceding claims, which comprises a piezoelectric semiconductor (4, 6, 14) which has at least in part a piezoelectric surface coating.

12. Electronic module (1,10) according to claim 9, wherein the piezoelectric surface coating is a piezoelectric thin-film coating.

13. Electronic module (1,10) according to one of the preceding claims, comprising a piezoelectric semiconductor (4, 6, 14) having a region on which piezo crystals are deposited.

14. Electronic module (1,10) according to one of the preceding claims, comprising a thermal paste.

15. Electronic module (1,10) according to one of the preceding claims, comprising a metallic heat sink.

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