Patent Description:
The fully solid-state circuit breakers belong to the technical field currently undergoing intense development, especially in the field of DC electrical circuits. This is related to a massive deployment of DC energy storages, DC distribution grids, and, last but not least, the expansion of the battery-supplied higher power applications. Here, the direct current protections and related circuit breakers improve the level of operation safety.

The fully solid-state DC circuit breaker is characterized by an absence of a mechanical switching apparatus. The function is conducted by a power electronics circuit with self-commutating power semiconductor devices, usually IGBT or MOSFET-type transistors that provide safe current tripping according to tripping characteristics of the circuit breaker.

Generally known topologies of the power electronics circuit for direct current tripping in both directions include, among others, a bridge rectifier with one transistor switch, an anti-serial connection of reverse conducting transistor switches, or an anti-parallel connection of reverse blocking transistor switches. Considering the required high nominal currents of the fully solid-state circuit breakers, it is necessary to arrange a certain number of transistors in parallel within one switch in order to achieve acceptable thermal loss under circuit breaker operation.

Document <CIT> discloses a simple arrangement of a solid-state circuit breaker, to which a mechanical apparatus may be added, if galvanic load insulation is required for safety reasons. In this case the controlling section of the circuit breaker should provide a proper sequence of turning on and off both the mechanical apparatus and a power electronics circuit so that no current is loaded onto the mechanical apparatus upon turning on and tripping the circuit breaker. A controlling section shall also provide a proper control sequence when the circuit breaker is turned off manually. The power electronics circuit having bi-directional current tripping may be used in the circuit breaker not only to disconnect the load, i.e., to disconnect electrically conductive paths between mains input terminals and output terminals for a protected device, but it may also be used when circuit breaker tripping to produce an electrically conductive path between the mains input terminals. As disclosed in document <CIT>, the grid current flowing through this path causes the tripping of the superior protective device.

A power electronics circuit of a circuit breaker may be provided with discrete power semiconductor devices. The power electronic circuit may also be included in a power semiconductor module. Its structural components include a supporting base that provides a mechanical support to electronic components and permits dissipation of heat caused by power losses. Further included are electronic components for switching and creating a current pathway for a protected circuit, and electrically conductive patterns being created on at least one of the base surfaces and used for electrically conductive connection between the electronic components. For example, this solution is disclosed in document <CIT>.

A common method for implementation of the power modules is use of the DBC technology. It is based on a ceramic substrate made from a material having high thermal conductivity while also providing electrical insulation. The substrate is provided with a copper layer fixed thereto using eutectic Cu and CuO<NUM> alloy on both sides. An electrically conductive pattern is etched in the copper layer. Etching of the pattern has a disadvantage with respect to wasting of materials, speed, and production safety. In addition, the etching method does not allow to achieve fine electrically conductive patterns. For example, this solution is disclosed in document <CIT>.

The ceramic substrate of the DBC technology may be layered by soldering to create sandwich structures. The power semiconductor bare dies may themselves be placed in a recess in the copper layer on a small ceramic substrate either individually or in small groups in a way to level up the upper side of the semiconductor bare die with the top side of the copper layer of the ceramic substrate. The bottom bare die electrode may be electrically connected to the lower side of the ceramic substrate via a passage in the ceramic substrate filled with a conductive material. The passage may be then used as a shunt resistor to measure the electric current. Each substrate may be put on a big ceramic substrate with the DBC technology according to requirements for total electric connection. Again, the need to use the copper layer thicker than thickness of the semiconductor bare die does not allow to achieve fine electrically conductive patterns, and the semiconductor bare dies fitted out like this do not use full surface of the ceramic substrate. For example, this solution is disclosed in document <CIT>.

Due to the high degree of parallelization of the transistors in the switch within the power electronics circuit topology of the circuit breaker, it is necessary to ensure optimum driving conditions (design symmetry, identical electrical parameters, minimization of parasitic inductances, etc.) for each individual transistor. Generally known approaches use non-power electronics devices very close to each transistor connected in parallel so that the impact of parasite elements in the commutation loop of the driving circuit is attenuated, in particular in dynamic phenomena in the power circuit.

Small dimensions of the non-power electronics devices require sufficiently fine electrically conductive pattern to be created correctly. The latter in a power module with a common substrate may not be feasible with etch-based technologies as the use of thick layers in the power circuit is required. In addition, the placement of the non-power electronics devices onto the same substrate with the power circuit limits the usable area of the power module surface for the electrically conductive patterns of the power circuit. This contributes to the increase of current density and power losses in the electrically conductive pattern of the power circuit. Also, the reduced surface of the electrically conductive pattern of the power circuit increases the power module's thermal resistance and the power module's internal operating temperature is increased thereby.

Document <CIT> discloses a power module for a solid-state circuit breaker comprising an insulating material in which there is arranged a bi-directional power electronics switch and non-power electronics circuits with protective elements, circuits controlling the power electronics switch and sensor circuits, further comprising a heat sink made of a dielectric material having thermal conductivity over <NUM> W/m/K, having on its surface an electrically conductive power pattern made of copper, wherein the electrically conductive power pattern comprises at least two electrically insulated sections, the bi-directional power electronics switch comprising power semiconductor bare dies mutually interconnected with a power conductive connection is placed on the electrically conductive power pattern and connected by the electrically conductive power connection, wherein the power electronics switch is positioned on longitudinal axis of the module, the electrically conductive power pattern is interconnected with output power electric terminals, the non-power electronics circuits are interconnected with output non-power electric terminals and with the power electronics switch via a non-power conductive connection, the output non-power electric terminals are interconnected with the protective circuits, wherein at least the heat sink, the power electronics switch, and the non-power electronics circuits are jointly included in a monolithic multilayer structure, which parts are connected through entire contact surfaces.

Document <CIT> discloses a power module, in particular a commutation cell for an inverter. The power module has a ceramic circuit carrier and at least one semiconductor switch half-bridge having two semiconductor switches which are connected to the circuit carrier. The power module has a flexible printed circuit board which is connected to the circuit carrier in the region of the semiconductor switches. The power module has a temperature sensor which is connected to the flexible printed circuit board and is designed and arranged to capture a temperature of the circuit carrier in the region of the semiconductor switches.

Document <CIT> discloses a circuit arrangement including at least two semiconductor chips having first and second mutually connected load terminals, a first load current collecting conductor track, and an external terminal connected thereto. For each of the semiconductor chips, there is at least one electrical connection conductor connected to the first load terminal of the relevant semiconductor chip and also to the first load current collecting conductor track. The total inductance of all the connection conductors with which the first load terminal of the second of the semiconductor chips is connected to the first load current collecting conductor track has at least twice the inductance of that section of the first load current collecting conductor track which is formed between the second connection location of the first of the semiconductor chips and the second connection location of the second of the semiconductor chips.

Document <CIT> discloses a circuit interrupter device including line hot, line neutral, load hot, and load neutral terminals, a solid-state switch, internal short-circuit switch circuitry, and control circuitry. The solid-state switch is connected in an electrical path between the line hot and load hot terminals. The internal short-circuit switch circuitry comprises an internal short-circuit switch and a shunt resistor serially connected between the line hot and line neutral terminals. The control circuitry is configured to detect for an occurrence of a fault condition. In response to detecting the occurrence of a fault condition, the control circuitry is configured to drive the solid-state switch into a switched-off state, and activate the internal short-circuit switch to generate an internal short-circuit path between the line hot and line neutral terminals and allow short-circuit current to flow through the shunt resistor between the line hot terminal and the line neutral terminal of the circuit interrupter device.

The object of the present invention is to provide a power module for the fully solid-state circuit breakers, which allows power loss (heat) dissipation to the maximum extent from the power circuit components, allows implementation of excellent construction design symmetry of the power circuit, contains non-power electronics devices for optimum driving conditions and protection of the power electronics switches, and which may be manufactured without etching with maximum level of details of electrically conductive patterns by the thick printed copper layer method known as TPC.

The present invention relates to the construction design of a power module for a solid-state circuit breaker. The module includes an insulating material in which at least bi-directional power electronics switch and non-power electronics circuits are arranged. The insulating material may be placed in a package. Alternatively, the insulating material may be self-supporting and its surface operates as the package, or the material itself is the package. The function of the package is known in the art, and it includes in particular mechanical durability (impact resistance, abrasion resistance) and resistance to environmental influences. The insulating material is preferably a dielectric potting material.

The non-power electronics circuits include at least protective elements, circuits controlling the power electronics switch and circuits of the sensors. In addition, the module includes a dielectric material heat sink having thermal conductivity over <NUM> W/m/K. It can be made, for example, of aluminium nitride or other suitable ceramics with suitable thermal conductivity and expansion properties. The electrically conductive power pattern of copper, silver, or combination thereof, is applied directly on the heat sink and comprises at least two electrically insulated sections, and it is applied preferably using a method of additive deposition.

The bi-directional power electronics switch is placed on the electrically conductive power pattern and connected by an electrically conductive power connection. The power electronics switch comprises non-encapsulated power semiconductor bare dies mutually interconnected by a power conductive connection. The power electronics switch is located on longitudinal axis of the module. Favourably, the power electronics switch is placed in the exact centre; however, a small deviation defined by the fit-out width of the power electronics switch causes no significant deterioration of the properties. The centric mounting of the power electronics switch results in optimum use of the die area and minimized inductance of a commutation loop. The dies of the power electronics switch may be mounted either by soldering or sintering.

The electrically conductive power pattern is interconnected with output power electric terminals. Furthermore, the electrically conductive power pattern is interconnected with auxiliary dielectric substrates through a contact layer. There are electrically conductive non-power patterns of silver, copper, or combination thereof, placed on the auxiliary dielectric substrates to interconnect the non-power electronics circuits. Favourably, the non-power electric patterns are applied by additive technology. The non-power electronics circuits are interconnected with the output non-power electric terminals and with the power electronics switch via the non-power conductive connection.

Both the output power electric terminals and the output non-power electric terminals may be embodied as soldering pins, press-fit pins, or ultrasound-welded electrodes. The output power electric terminals and the output non-power electric terminals are conductively connected with the protective circuits (e.g., by soldering). In particular, the protective circuits protect against overheating of the module. In addition, hazardous overvoltage occurs upon turning the power electronics switch off, which is managed using the protective circuits as well (overvoltage protection). The protective circuits may comprise a varistor (MOV), or TVS, or an active overvoltage circuit.

Favourably, the protective circuits are placed on their own substrate and it may be a ceramic-based one. It may be a printed circuit board based on a glass-epoxide material. Favourably, the substrate is placed above the power electronics switch and forms a sandwich arrangement having a minimum commutation loop. Said structure may be implemented to create a fully integrated power module for a solid-state circuit breaker. Alternatively, the protective circuits may be located outside the power module. However, the fully integrated design of the circuit breaker is not attainable in this case.

At least the heat sink, the power electronics switch, the auxiliary dielectric substrates, and the non-power electronics circuits are jointly included in a monolithic multilayer structure, elements of which are connected through entire contact surfaces. The contact surfaces between the components are desirably continuous and flat so that they fit together well for efficient heat transfer.

For more efficient cooling of the power module, the heat sink may be mechanically and heat-conductively connected with an auxiliary heat sink made of electrically conductive material having heat conductivity over <NUM> W/m/K. The auxiliary heat sink may be made of aluminium, copper, or other metal or metal alloy. A contact layer eligible to compensate differential thermal expansivity properties of the heat sink and of the auxiliary heat sink is made as a connection.

The contact layer of the heat sink may be a multilayer one. The layer may comprise an electrically conductive layer applied on the heat sink, and an electrically conductive connection of which full contact surfaces interconnect the electrically conductive layer and the auxiliary heat sink in a monolithic way.

Analogically, according to the claimed invention, the contact layer of the auxiliary dielectric substrate is a multilayer.

The layer comprises an electrically conductive layer applied on the auxiliary dielectric substrate, and electrically conductive power connection of which full contact surfaces interconnect the electrically conductive layer and the electrically conductive power pattern in a monolithic way.

A dielectric material of which the heat sink and/or auxiliary dielectric substrates are made, may be ceramics in particular. The electrically conductive power connection on the electrically conductive power pattern and/or electrically conductive connection of the auxiliary heat sink may be in particular a solder layer or a sintered material layer.

Favourably, the power electronics switch may be embodied either as comprising power semiconductor bare dies arranged in anti-serial order with reverse conducting transistor switches, or in an anti-parallel arrangement of reverse blocking transistor.

The power conductive connection between the power semiconductor bare dies of the bi-directional switch and/or the non-power conductive connection between the power semiconductor bare dies of the bi-directional switch and the non-power electronics circuit may comprise aluminium and/or copper wires and/or electrically conductive ribbons.

The object as defined above is achieved by the use of auxiliary substrates within the power module according to the present invention. The use of the auxiliary substrates will allow axially symmetrical arrangement because the conductive patterns for the transistor control and parameters sensing are made in above-crossing way.

The exemplary embodiment of the proposed invention is described with reference to the drawings, in which.

It is understood that specific embodiments of the invention described below are indicative only and do not in any way limit the embodiments of the invention to these specific ones shown here.

<FIG> shows the cross-section view on a power module of a fully solid-state circuit breaker. The power module for the solid-state circuit breaker includes insulating material <NUM>. The insulating material <NUM> is placed in a package <NUM> made of a thermally resistant plastic. The insulating material <NUM> is a silicone dielectric gel.

In the insulating material <NUM> there is provided a bi-directional power electronics switch <NUM>, non-power electronics circuits <NUM> including protective elements, circuits controlling the power electronics switch <NUM> and sensor circuits. Here, a desaturation protection is included in the protective elements. The sensor circuits are adapted to sensing of voltage, current, and temperature of the power electronics switch <NUM>. In addition, the module includes a dielectric material heat sink <NUM> having thermal conductivity over <NUM> W/m/K. Aluminium nitride is suitable material for the heat sink <NUM>. On its surface, the heat sink <NUM> is provided with an electrically conductive power pattern <NUM>. An electrically conductive power pattern <NUM> comprises two electrically insulated sections. Owing to use of the dielectric material for the heat sink <NUM>, the electrically conductive power pattern <NUM> is applied directly on the heat sink <NUM> and no electric insulation needs to be used between the electrically conductive power pattern <NUM> and the heat sink <NUM> being made of electrically conductive material in known designs.

A bi-directional power electronics switch <NUM> is placed on the electrically conductive power pattern <NUM> and connected by an electrically conductive power connection <NUM>. The bi-directional power electronics switch <NUM> comprises power semiconductor bare dies being mutually interconnected with a power conductive connection <NUM>. The power electronics switch <NUM> is located on longitudinal axis O1 of the module. The power circuit comprises anti-serial arrangement of semiconductor bare dies of the power electronics switch <NUM>. These are two groups of six of SiC MOSFET transistor dies connected in parallel, and they are placed axially symmetrically as closest as possible to the centre of the power module on the heat sink <NUM> as shown in <FIG>.

The electrically conductive power pattern <NUM> is interconnected with output power electric terminals <NUM>. In addition, it is joined to the auxiliary dielectric substrates <NUM> via a contact layer <NUM>. The contact layer <NUM> of the auxiliary dielectric substrate <NUM> comprises an electrically conductive layer <NUM> applied on the auxiliary dielectric substrate <NUM>, and the electrically conductive power connection <NUM> of which full contact surfaces link the electrically conductive layer <NUM> and the electrically conductive power pattern <NUM> in a monolithic way. There are electrically conductive non-power patterns <NUM> placed on the auxiliary dielectric substrates <NUM>. The non-power electric patterns <NUM> interconnect the non-power electronics circuits <NUM>. The non-power electronics circuits <NUM> are interconnected with the output non-power electric terminals <NUM> and in addition, with the power electronics switch <NUM> via the non-power conductive connection <NUM>. The heat sink <NUM>, the power electronics switch <NUM>, the auxiliary dielectric substrates <NUM>, and the non-power electronics circuits <NUM> are jointly included in a monolithic multilayer structure elements of which are connected through entire contact surfaces.

Optimum control of the power electronics switch <NUM> bare dies arranged in parallel is provided by a suitable electric connection with the non-power electronics circuits <NUM>. Thanks to thin layer of the electrically conductive non-power patterns <NUM> a necessary thin gap between the elements of the electrically conductive non-power pattern <NUM> is achieved allowing the use of the non-power electronics devices of SMD type with down to <NUM> size. Here, the non-power electronics circuit <NUM> is used for symmetric and electrically identical driving of the transistors connected in parallel, for attenuation of undesired oscillations that occur by the power electronics circuit operation, or for protection of the gate electrodes of the transistors. Use of the auxiliary dielectric substrate <NUM> causes that a multilayer interconnection structure is formed. The structure allows full use of heat sink <NUM> obverse side to carry high current load by the electrically conductive power patterns <NUM> and axially symmetrical placement of the semiconductor bare dies of the power electronics switch <NUM> (refer to <FIG>). At the same, the structure allows placement and interconnection of the non-power electronics circuit <NUM> on the auxiliary dielectric substrate <NUM> to be at distance as shortest as possible from the power electronics switch <NUM>. The auxiliary dielectric substrates <NUM> have the quality of electric insulation, thermal expansion properties and thermal conductivity properties identical to the heat sink <NUM> and therefore, the resulting properties of the power module are not influenced in any way. In this example, balancing (protective) resistors of Gate and Source electrodes are placed on the auxiliary dielectric substrates <NUM> separately for each power semiconductor bare die. Use of the auxiliary dielectric substrate <NUM> permits maximization of the surface of the electrically conductive power pattern <NUM> on the heat sink <NUM>. This is favourable, in particular with respect to minimization of the current density, minimization of power losses, and thermal impedance of the power module. At the same time, higher volume of the electrically conductive pattern <NUM> allow accumulation of more thermal energy in case of transient phenomena.

The output power electric terminals <NUM> and the output non-power electric terminals <NUM> are interconnected with the protective circuits <NUM> arranged on the substrate <NUM>. The output terminals <NUM>, <NUM> are provided as soldering pins.

The electrically conductive power pattern <NUM>, the electrically conductive non-power patterns <NUM> and electrically conductive layer <NUM> of the auxiliary dielectric substrate <NUM> are applied by an additive technology (printing technique). As illustrated in <FIG>, the electrically conductive power pattern <NUM> and the electrically conductive non-power patterns <NUM> have different thicknesses. The electrically conductive non-power pattern <NUM> is thinner than the electrically conductive power pattern <NUM>. Thicknesses of the layers range from <NUM> to <NUM>.

The electrically conductive power connection <NUM> on the electrically conductive power pattern <NUM> and electrically conductive connection <NUM> of the auxiliary heat sink is a layer of solder. The power conductive connection <NUM> between the semiconductor bare dies of the bi-directional switch <NUM> and/or the non-power conductive connection <NUM> between the semiconductor bare dies of the bi-directional switch <NUM> and the non-power electronics circuit <NUM> are provided in the form of electrically conductive ribbons. More specifically, these are silver-plated copper ribbons. The power conductive connection <NUM> includes ribbons <NUM> wide and <NUM> thick. Compared to the wire-bonding technology, maximum transmitted current and reduction of the current density is permitted thereby not only in the power conductive connection <NUM> but also in the metallized area of the semiconductor bare die. The interconnection between the driving electrodes of the power electronics switch <NUM> bare dies and the non-power electronics circuit <NUM> is provided by <NUM> wide and <NUM> thick ribbons.

Another contemplated embodiment is shown in <FIG> and it differs from the one described above by that the dielectric material heat sink <NUM> is mechanically and thermally connected to the auxiliary heat sink <NUM> made of electrically conductive material having thermal conductivity over <NUM> W/m/K. A heat sink contact layer <NUM> is interconnecting the heat sink <NUM> and the auxiliary heat sink <NUM> while compensating their different thermal expansion properties. The contact layer <NUM> of the heat sink comprises an electrically conductive layer <NUM> applied on the heat sink <NUM>, and an electrically conductive connection <NUM> of which full contact surfaces interconnect the electrically conductive layer <NUM> and the auxiliary heat sink <NUM> in a monolithic way. Here, the auxiliary heat sink <NUM> is made of aluminium, and the heat sink <NUM> is made of Al<NUM>O<NUM>. An advantage of this arrangement is lower price and lower demands on production technology.

Claim 1:
A power module for a solid-state circuit breaker comprising an insulating material (<NUM>) in which there is arranged a bi-directional power electronics switch (<NUM>) and non-power electronics circuits (<NUM>) with protective elements, circuits controlling the power electronics switch (<NUM>) and sensor circuits,
further comprising a heat sink (<NUM>) made of a dielectric material having thermal conductivity over <NUM> W/m/K, having on its surface an electrically conductive power pattern (<NUM>) made of silver and/or copper, wherein the electrically conductive power pattern (<NUM>) comprises at least two electrically insulated sections,
the bi-directional power electronics switch (<NUM>) comprising power semiconductor bare dies mutually interconnected with a power conductive connection (<NUM>) is placed on the electrically conductive power pattern (<NUM>) and connected by the electrically conductive power connection (<NUM>), wherein the power electronics switch (<NUM>) is positioned on longitudinal axis (O1) of the module, the electrically conductive power pattern (<NUM>) is interconnected with output power electric terminals (<NUM>) and via a contact layer (<NUM>) further joined to auxiliary dielectric substrates (<NUM>) where there are electrically conductive non-power patterns (<NUM>) made of silver and/or copper interconnecting the non-power electronics circuits (<NUM>) placed on the auxiliary dielectric substrates (<NUM>), wherein said contact layer (<NUM>) of the auxiliary dielectric substrates (<NUM>) comprises an electrically conductive layer (<NUM>) applied on the auxiliary dielectric substrates (<NUM>), and the electrically conductive power connection (<NUM>) of which full contact surfaces interconnect the electrically conductive layer (<NUM>) and the electrically conductive power pattern (<NUM>) in a monolithic way,
the non-power electronics circuits (<NUM>) are interconnected with output non-power electric terminals (<NUM>) and with the power electronics switch (<NUM>) via a non-power conductive connection (<NUM>),
the output power electric terminals (<NUM>) and the output non-power electric terminals (<NUM>) are interconnected with protective circuits (<NUM>),
wherein at least the heat sink (<NUM>), the power electronics switch (<NUM>), the auxiliary dielectric substrates (<NUM>), and the non-power electronics circuits (<NUM>) are jointly included in a monolithic multilayer structure, which parts are connected through entire contact surfaces.