Circuit protection module with a switching unit, MEMS device for such a switching unit and method for manufacturing and operating such a MEMS device

Abstract

The present invention proposes a circuit protection module 10 with a first 6' and a second 6'' circuit protection device as well as a switching unit 11. The circuit protection module is designed and configured to change from a primary state, in which the first circuit protection device is operative, to a backup state, in which the second circuit protection device is operative. Furthermore, in an aspect of the present invention, a MEMS device adapted and configured to form a toggle switch is disclosed, which can be used as part of the switching unit. Moreover, methods for manufacturing and operating such a MEMS device are given.

Description

[0001]CIRCUIT PROTECTION MODULE WITH A SWITCHING UNIT, MEMS DEVICE FOR SUCH A SWITCHING UNIT AND METHOD FOR MANUFACTURING AND OPERATING SUCH A MEMS DEVICE TECHNICAL FIELDThe invention disclosed herein relates to the technicalfield of basic electric elements, in particular to the technical field of protective circuit arrangements. Morespecifically, the invention pertains to a circuitprotection module. Under further aspects, the inventionrelates to a switching unit for the circuit protectionmodule and to a MEMS device, which may in particular beused in the switching unit. The invention is furtherdirected to a method of producing the switching unit as well as to methods for manufacturing and operating the proposed MEMS device. BACKGROUND OF THE INVENTION It is known in the state of the art to apply redundant systems to avoid the consequences of aging or failure of a single component. However, for example in the case of circuit protection devices, such as electrical fuses, which are connected in series to the device they protect, the introduction of a redundant system is not straightforward. P220511(WO) The presence of the redundant system may even prevent the primary protection device from acting as expected, when notembedded properly into the complete system. On the otherhand, fuses, as an example, undergo aging processes and maynot function properly any more at the end of theirlifetime, such that the possibility of switching to abackup-system may be a requirement. The development of MEMS (micro electro-mechanical system) micro-switches and micro-relays is of great interest because of their potential for miniaturisation, high switching speed thanks to low inertia, and rapid as well as easy scale-up to volume production. Their applications include, e.g., RF switches, sensors, and power switches.Independent of their intended application they have beenfabricated using surface and bulk micromachining with vertical, lateral, or zipper contacts and have amongst others been actuated by magnetic, electrostatic, piezoelectric and thermal concepts. For high-current MEMS switches handling electric currents beyond 1 A, contact resistance and contact force become increasingly important. A possible solution to this problem is the parallelization of cantilever MEMS switches. Consequently, there is a need for improved MEMS switching devices, especially for use in switching units, which in turn can for instance be employed in circuit protection modules. Improvements of such MEMS switching devices are P220511(WO) especially sought in terms of low contact resistance and handling of higher currents. SUMMARY OF THE INVENTIONIt is an object of the present invention is to provide adevice or a method, that can combine requirements of safetyand availability over the whole life cycle of a system.This object is achieved by a circuit protection moduleaccording to claim 1.The circuit protection module according to the invention has a source side terminal and a load side terminal for electrical current. The circuit protection module has a first current path between said source side terminal and said load side terminal, the first current path leading through a first circuit protection device and through a first switch point. The circuit protection module has a second current path between said source side terminal and said load side terminal, the second current path leading through a second circuit protection device and through a second switch point. Furthermore, the circuit protection module has a bypass current path, which branches off from said second current path at an intermediate position between the second circuit protection device and the second switch point. The bypass current path bypasses said second switch point. The circuit protection module further has aswitching unit comprising said first switch point and saidP220511(WO) second switch point. The circuit protection module has a primary state in which said first current path is closed at said first switch point and said second current path is open at said second switch point. The circuit protection module has a backup state in which said first current path is open at said first switch point and said second current path is closed at said second switch point. The circuit protection module is designed and configured to change from said primary state to said backup state once an electric current in said bypass current path reaches or exceeds a predetermined threshold and to stay in said backup state when the electric current in said bypass current path falls below said threshold again. The predetermined threshold is set such that it is exceeded when there is an indication that the first circuitprotection device, which for example can be a fuse wire ora semiconductor base device, will fail soon. The circuitprotection module according to the present invention may be seen as a safe-life module, as it has the effect that thesystem is available with high probability over an extendedlifetime, i.e. it provides a measure that the system does reacts properly and as specified during its complete life cycle. Thus, the invention may be described as a circuit protection module with a first and a second circuit protection device as well as a switching unit. The circuit protection module is designed and configured to change from P220511(WO) the primary state, in which the first circuit protection device is operative, to the backup state, in which the second circuit protection device is operative. Embodiments of the circuit protection module result from the features defined in claims 2 to 5. In an embodiment of the circuit protection module, the first switch point and the second switch point are both formed as openable and closable contacts of a two-way switch having a common pole connected to the load side terminal.In a variant of this embodiment, the two-way switch may bedesigned to switch only once from the primary state to the backup state. The two-way switch may be designed such that it will not go back from the backup state to the primary state under the effect of a current flowing in the circuit protection module. The two-way switch may be designed such that it can be brought into the primary state by amechanical manipulation not involving any current flowingin the circuit protection module. Such a mechanical manipulation may be used to establish the primary state for a first time, e.g. after production of the two-way switch and before starting operation of the circuit protection module. P220511(WO) In an embodiment of the circuit protection module, a releasable retention mechanism holds the two-way switch in a position closing the first current path and wherein the two-way switch is biased by a spring towards a position closing the second current path. In an embodiment of the circuit protection module, a coil for producing a magnetic field forms a section of the bypass current path. The releasable retention mechanism comprises a ferromagnetic element and is designed to release the two-way switch once the force of the magnetic field produced by said coil acting on said ferromagnetic element reaches or exceeds a predefined force threshold. In an embodiment of the circuit protection module, an electric heating element forms a section of the bypass current path. The releasable retention mechanism is designed to release the two-way switch under exposure to thermal heat produced by the electric heating element. In particular, the releasable retention mechanism may be basedon a shape memory effect, a fusibility, or a thermalexpansion. In an embodiment of the circuit protection module, theswitching unit is formed as a silicon-based micro-electromechanical system (MEMS).P220511(WO) In an embodiment of the switching unit the silicon-based micro-electromechanical system comprises said two-way switch, said releasable retention mechanism and said spring. It is a further object of the present invention to provide an improved MEMS switching device having a high switching speed and a low contact resistance, which is applicable as a toggle switch for high currents. Such a MEMS device is specified in claim 6. The MEMS device is preferably able to provide a "make before break" feature allowing to switch from one input or output terminal to another without interruption of current flow. Features making this possible are in particular provided in the dependent claims11 and 12.It is another object of the present invention (in a further aspect thereof) to provide a switching unit based on the proposed MEMS device. Such a switching unit is given in claim 17. Furthermore, it is also an object of the present invention to provide a circuit protection device based on the suggested switching module. Such a circuit protection device is given in claim 18. Moreover, it is a further object of the present invention to provide methods for manufacturing, bringing into an P220511(WO) operable mode and operating the proposed MEMS device. Suchmethods are laid out in claims 19, 21 and 22, respectively.Specific embodiments of (the further aspects of) the present invention are set out in the dependent claims. In the following features included in brackets are to be considered as optional. The MEMS switching device according to the present invention is based on the use of a main spring, which is preloaded after fabrication of the device. This allows to achieve the desired contact force and therewith the desired low contact resistance. A MEMS device according to the present invention is adapted and configured to form a toggle switch, wherein the toggle switch comprises:^ a normally closed contact part (NCC) comprising a firstcontact element with a first electrical contact surface and a second contact element with a second electrical contact surface, wherein the first electrical contact surface is in electrical contact with the second electrical contact surface in a primary state of the toggle switch and the first electrical contact surfaceis electrically disconnected from the second electrical P220511(WO) contact surface in a secondary state of the toggle switch;^ a normally open contact part (NOC) comprising a thirdcontact element with a third electrical contact surface and a fourth contact element with a fourth electrical contact surface, wherein the third electrical contact surface is electrically disconnected from the fourth electrical contact surface in the primary state of the toggle switch and the third electrical contact surface is in electrical contact with the fourth electrical contact surface in the secondary state of the toggle switch;^ a main spring arranged between the second and thirdcontact element and configured to force the first electrical contact surface away from the second electrical contact surface and to force the third electrical contact surface onto the fourth electrical contact surface in the secondary state of the toggle switch; and^ an escapement / locking mechanism configured to hold themain spring in a position where the first electrical contact surface is in electrical contact with the second electrical contact surface and the third electrical contact surface is electrically disconnected from the fourth electrical contact surface in the primary stateof the toggle switch and to release the main spring in the secondary state of the toggle switch, wherein the escapement / locking mechanism is adapted to receive an external force for triggering a transition from the P220511(WO) primary state to the secondary state of the toggle switch. In an embodiment the device further comprises a travel spring connected between an outer frame of the device and to a pusher element including a force coupling element adapted to receive a tensioning / activation tool, such as a pin, to introduce an external force onto the pusher element in order to induce movement of the pusher element within a plane of the device, wherein the first, second, third and fourth contact elements and the pusher element are arranged in series such that the movement of the pusher element is transferable to the first, second, third and fourth contact elements, the movement being adapted to bring the device into an operating position after manufacturing, in particular into the primary state, with a tensioned main spring. In a further embodiment of the device the escapement / locking mechanism comprises at least one snap-fit assembly, in particular with a snap-in clamp attached to one or more holding springs and a snap-in area formed as part of the second contact element, the snap-in area being formed to receive the snap-in clamp. The escapement / lockingmechanism in particular includes a force coupling portionadapted to interact with the one or more holding springs when an external force is applied to the force coupling portion such that the snap-fit assembly is opened and releases the tensioned main spring. P220511(WO) In a further embodiment of the device the escapement / locking mechanism has a symmetrical structure, and in particular comprises two identical snap-fit assemblies arranged on either side of a symmetry axis of the device. In a further embodiment the device further comprises a further locking mechanism, in particular comprising at least one further snap-fit assembly, adapted to hold the travel spring and the fourth contact element in the operating position. In a further embodiment of the device the further locking mechanism has a symmetrical structure, and in particular comprises two further identical snap-fit assemblies arranged on either side of a symmetry axis of the device. In a further embodiment the device further comprises a positioning spring connected between the pusher element and the fourth contact element and adapted to adapt the positioning of the fourth contact element relative to the third contact element such that optimal / maximal contact is achieved when the third electrical contact surface is in electrical contact with the fourth electrical contact surface in the secondary state of the toggle switch. This for instance allows to compensate a potential slight taper of the contact surfaces caused by the fabrication process. P220511(WO) In a further embodiment of the device the second contact element and the third contact element are mechanically coupled with each other by means of a "piston / plunger" in "cylinder / box" structure, wherein the piston / plunger is moveable within the cylinder / box from a first end position to an opposite second end position, the piston / plunger being part of the third contact element and the cylinder / box being part of the second contact element or vice-versa. This for instance enables a "make before break" mechanism, wherein during a transition from the primary state to the secondary state of the toggle switch the first electrical contact surface remains in electrical contact with the second electrical contact surface whilst the third electrical contact surface establishes electrical contact with the fourth electrical contact surface, and subsequently the first electrical contact surface electrically disconnects from the second electrical contact surface. In a further embodiment of the device an opening between the piston / plunger and the cylinder / box acts as a further force coupling element adapted to receive a tensioning / activation tool, such as a pin, to introduce an external force onto the second contact element in order to induce movement of the second contact element within a plane of the device, wherein the movement of the second contact element is transferable to the first and third contact element, the movement being adapted to bring the device into an operating position after manufacturing, in P220511(WO) particular into the primary state, with a tensioned main spring. In a further embodiment of the device the second contact element and the third contact element form a single (rigid) part. In a further embodiment the device further comprises an auxiliary spring attached to the main spring and connected to the second contact element, wherein a stiffness of the main spring is greater than a stiffness of the auxiliary spring. This in particular supports enabling a "make before break" mechanism. Furthermore, it in particular prevents jamming of the "piston / plunger" in "cylinder / box"structure by providing some (lateral) retention between thetwo. In a further embodiment the device is based on a silicon substrate or a sapphire substrate or a quartz substrate or a ceramic substrate, the substrate in particular having athickness of at least 250 µm, more particularly of at least1 mm, for instance of within a range from 250 µm to 2 mm.In a further embodiment of the device the first, second, third and fourth electrical contact surfaces are covered with a coating, in particular a multi-layer coating, wherein the coating or a top layer of the multi-layer coating is made of gold, in particular electroless nickel P220511(WO) electroless palladium immersion gold, in particular having a thickness in a range from 70 nm to 100 µm, and wherein between a substrate surface and the top layer there is in particular a layer of titanium (Ti) and / or chromium (Cr) and / or one or more layers of copper (Cu), wherein the titanium (Ti) and / or the chromium (Cr) is an adhesion layer, in particular deposited by means of a PVD process and in particular has a thickness in a range from 10 to 50 nm, and wherein a base copper layer is in particular deposited by means of a PVD process, e.g., sputtered, and in particular has a thickness in a range from 400 nm to 5 µm, an wherein an additional copper layer is in particular an electro-plated copper layer, and in particular has a thickness in a range from 5 µm to 50 µm. In a further embodiment of the device all the parts / elements of the device are integrally formed as one piece of a substrate. In a further embodiment of the device the toggle switch is an irreversible toggle switch adapted and configured to only be able to transmission from the primary state to the secondary state and not vice-versa. Possible features of the proposed MEMS device:- The device for instance has an area of 15 x 15 mm2.- The device for instance has a thickness / depth of 2 mm orless. P220511(WO)- The closed contacts of the device have a contactresistance of less than 3 mΩ.- The gap between the first and second electrical contactsurface and the gap between the third and fourth electrical contact surface when the main spring is tensionless after fabrication is greater by at least a factor of 1.2, e.g., the gap then being 400 µm wide, than the gap between the first and second electrical contact surface in the primary state and the gap between the third and fourth electrical contact surface in the secondary state, e.g., the gap then being only 333 µm wide.- The device is capable of switching electrical currents ofat least 10 A.- The main spring provides a contact force of at least0.25 N, preferably of at least 0.5 N. As an aspect of the present invention a switching unit is proposed with a first, second and third terminal, wherein the switching unit comprises:^ a MEMS device with the above-mentioned features, and^ an activation element adapted to trigger a switchingaction of the toggle switch from the primary state to the secondary state, wherein a first terminal, e.g., an input, of the switching module is electrically connected with the first electrical contact surface, a second terminal, e.g., a further input, of the switching module is electrically connected with the P220511(WO) fourth electrical contact surface, and a third terminal, e.g., an output, of the switching module is electrically connected with the second and third electrical contact surface, and wherein the activation element in particular comprises a coil for producing a magnetic field and a ferromagnetic element, the activation element being adapted to release the locking mechanism once the force of the magnetic field produced by the coil acting on the ferromagnetic element reaches or exceeds a predefined threshold, or wherein the activation element in particular comprises an electric heating element, the activation element being adapted to release the locking mechanism under exposure to thermal heat produced by said electric heating element, in particular wherein the activation element is based on a shape memory effect, a fusibility or a thermal expansion. As a further aspect of the present invention a circuit protection module with the features mentioned above is proposed comprising the previously proposed switching unit. A method for manufacturing a MEMS device as previously proposed comprises the steps:- providing a silicon substrate / wafer or alternatively asapphire substrate or a quartz substrate or a ceramic substrate, respectively, the substrate in particular havinga thickness of at least 250 µm, more particularly at least1 mm, for instance in a range from 250 µm to 2 mm; andP220511(WO)- deep reactive ion etching, in particular by means of aBosch process, or selective laser etching or anisotropic wet etching the structures / elements of the device. In an embodiment the method further comprises one or more of the following steps:- growing in a diffusion furnace, e.g., a 1 μm strong,thermal oxide on the substrate by applying a wet oxidation process to provide electrical insulation of at least 250 V;- on top of the oxide an, e.g., 15 nm thick, titanium (Ti)adhesion layer and an, e.g., 400 nm thick, copper (Cu) seed layer by means of sputtering on the tilted and rotating substrate to ensure homogeneous layer formation and to reach the very bottom of the trenches / sidewalls;- patterning by means of photolithography with laminateddry photoresist on both side of the substrate;- forming an, e.g., 20 μm strong, copper (Cu) layer aselectrical conductors by means of electroplating;- stripping the photoresist, e.g., in potassium hydroxide(KOH), and removing the seed layer, e.g., in a copper (Cu) etch step;- adding, e.g., on top of the copper, a layer ofelectroless nickel electroless palladium immersion gold to achieve a low contact resistance and enable wire bonding. A method for bringing a MEMS device as previously proposed into the primary, biased / tensioned state after fabrication P220511(WO) comprises applying an external force to the pusher element thus pushing the and tensioning the main spring and engaging the locking mechanism such that. A method for operating a MEMS device as previously proposed to bring the device from the primary, biased state to the secondary state comprises applying an external force to a lever of the locking mechanism thus disengaging the locking mechanism and releasing the main spring. It is specifically pointed out that combinations of the embodiments mentioned above can result in even further, more specific embodiments. It is also to be noted that certain features / elements of the embodiments mentioned above can be considered as stand- alone inventions, such as the MEMS device or the switching unit, which can for instance be employed independently in other possible apparatuses or for other purposes than claimed or described in the following. BRIEF DESCRIPTION OF THE DRAWINGS The present invention is further explained below by means of non-limiting specific embodiments and with reference to the accompanying drawings, which show the following: P220511(WO)Fig. 1 a schematic view of the circuit protection moduleaccording to the invention;Fig. 2 in sub-figures 2.a) and 2.b) schematicillustrations of the basic operation principle of the circuit protection module;Fig. 3 a schematic view of an embodiment of the circuitprotection module including neighbouring elementsin a typical use situation;Fig. 4 a schematic view of a specific embodiment of thecircuit protection module;Fig. 5 in subfigures 5.a) to 5.c) schematic views ofembodiments with specific realizations of the switching unit;Fig. 6 a schematic diagram of the power MEMS-based toggleswitch with normally closed (NCC) and normally open contacts (NOC) according to the present invention;Fig. 7 a) a top view of a MEMS device according to thepresent invention with annotations, and b) the top view of a MEMS device according to the present invention with further annotations;Fig. 8 a) the top view of a MEMS device according to thepresent invention, and b) schematically different phases / states of the MEMS device according to the present invention;Fig. 9 a top view of a MEMS device according to the presentinvention mounted in a frame included wire bonds to the input and output terminals; P220511(WO)Fig. 10 a) a first perspective view of an assembled switchingmodule according to the present invention with a Fe- yoke actuator, and b) a second perspective view of an assembled switching module according to the present invention with a Fe-yoke actuator; andFig. 11 a schematic diagram of the fabrication process of aMEMS device according to the present invention; andFig. 12 a) a side view on to a sidewall of a trench acting asan electrical contact of a MEMS device according to the present invention, and b) an enlarge view of a cross-section of the sidewall of a trench acting as an electrical contact of a MEMS device according to the present invention showing details of the sidewall surface. In the figures, like reference signs refer to like parts. DETAILED DESCRIPTION OF THE INVENTION Fig. 1 shows schematically and simplified, a circuitprotection module 10 according to the invention. Thecircuit protection module has two current paths leading inparallel to each other from a source side terminal 4 to aload side terminal 5. The route of a first current path 1is indicated by black arrows, whereas the route of a second current path 2 is indicated by white arrows. Each of these current paths leads through a circuit protection device, 6' P220511(WO) or 6'', respectively, which are able to interrupt the respective current path if the electrical current flowing through the circuit protection device is too high. The circuit protection devices may be fuses based on a fuse wire or may be semiconductor-based circuit protection devices. Both current paths further lead through a switch point, 7' or 7'', respectively, at which switch point the current path may be opened or closed. A bypass current path 3 is indicated by striped arrows. It branches off from the second current path at an intermediate point 8, which intermediate point is located between the second circuit protection device 6'' and the second switch point 7''. The bypass current path bypasses the second switch point 7'' and thus provides for a connection leading from the source side terminal 4, across the second current protection device 6'' and to the load side terminal 5, even if the second current path is interrupted at the second switch point. In a primary state of the circuit protection module, the first current path is closed at the first switch point 7' and the second current path is open at the second switch point 7''. In this primary state, current flowing across the circuit protection module is split into a main fraction following the first current path and a further fraction running through the second circuit protection device and the bypass current path. This is the steady state of a running system after initial start of operation. If a fatal current error occurs, safe interruption of the circuit is P220511(WO) performed by the first circuit protection device. An indication of possible failure of the first circuit protection device, e.g. due to wear out at the end of its lifetime, is an increasing resistivity and subsequently an increase of current through the bypass current path. A detector element, which is symbolically indicated as a circle, is able to trigger a switch over mechanism that brings the circuit protection module into a backup state. This switch over is triggered, once the current in the bypass current path reaches or exceeds a predetermined threshold. In the backup state, the second current path is closed at the second switch point 7'' and the first current path is open at the first switch point 7'. In this state, all the current runs across the second circuit protection device 6''. This is the backup operating state which provides a new steady state of a running system, this time with the second circuit protection device having the role of interrupting the circuit in case of a fatal current error. Closing the second current path at switch point 7'' has the effect that the current in the bypass current path drops again. The circuit protection module is designed and configured to stay in the backup state and will not go back to the primary state. The switch-over from the primary state to the backup state may be realized by a force acting on switch elements, as symbolically indicated by a spring 12, which spring may be prestressed and pushing into the direction indicated by the arrows in the dashed line. There may be a blocking P220511(WO) mechanism holding the spring in its prestressed state until the blocking is released depending on an electrical current flowing in the bypass current path 3. A diagonally hatched arrow symbolizes such a releasable retention mechanism 9. Fig. 2.a) illustrates in a simplified block diagram the primary state, where the current mainly flows across the first circuit protection device 6'. This corresponds to the primary state, in which the first circuit protection device 6' has the role interrupting the electrical current flowing between the source side terminal and the load side terminal, in case an overcurrent should occur. A minor amount of electrical current may flow across the second circuit protection device 6'' already in this state. Fig. 2.b) illustrates the situation after switching over to the backup state, in which the current follows the secondcurrent path indicated by white arrows. In the backupstate, the second circuit protection device 6'' has the role interrupting the electrical current flowing between the source side terminal and the load side terminal, in case an overcurrent should occur. Both partial figures, Fig. 2.a) and Fig. 2.b), show the main elements of the circuit protection module, namely two circuit protectiondevices 6' and 6'', as well as a switching unit 11.Fig. 3 shows an embodiment of the circuit protection module. A fuse array 14 comprises a first and a second fuse, having the role of the first and second circuit protection device. A detector module 15 watches the current P220511(WO) in the two paths. As the second current path is interrupted at the second switch point, the current in the bypass can be measured at the point indicated by I2, i.e. it is not necessary to measure the current in the bypass itself. The threshold may be an absolute threshold or a relative threshold which is set relative to the current in the first current path, i.e. may be measured at the point indicatedby I1. In addition, the figure shows the possible use ofthe circuit protection module, which is connected to a source of electric power on the side of the source side terminal 4 and which is connected to a load, the resistivity Rl of which load may vary. Fig. 4 shows another embodiment of the circuit protectionmodule. The switching unit 11 in this embodiment comprisesa coil 17 placed in the bypass path. The coil provides a magnetic force which is able to release a retention mechanism, once the force exceeds a force threshold. By this, a switch-over from the primary state to the backup state is triggered. A resistivity R1 of the first current path and the combined values of the resistivity RMicroActuatorof the coil, which can be implemented as a micro actuator, and the resistivity R3 of the bypass path may be set such that once the resistivity RF1of the first fuse increasesabove the value, which assures safe operation, the amountof electrical current flowing across the coil is sufficient to trigger the switch-over. P220511(WO) Fig. 5.a) shows the structure of an embodiment of the circuit protection module, which may be seen as a safe-lifemodule, in which the switching unit 11, which accordinglymay be seen as a safe-life switching unit. Note that inFigs. 5.a) to 5.c) - different from the orientation in Fig.1 to Fig. 4 - the primary path is the lower and the backuppath is the upper path. Fig. 5.b) shows the details of avariant of the switching unit 11. A switch over isperformed by the force Fspring of a preloaded spring acting in upward direction. A magnetic force Fcoil of the coil 17, which is positioned in the bypass path bypassing the open connection in the backup path, establishes the mechanical connection between the spring and the switch, once the force reaches or exceeds a force threshold. The force threshold, the resistivities in the paths, the number of windings of the coils etc. may e.g. be selected such that the switch-over to the backup state occurs if the current in the bypass path reaches or exceeds 50% of the total current flowing between the source side terminal and the load side terminal. During the switch-over, current is flowing across the coil until the contact in the backup path is completely established. This way, seamless switching is possible. Fig. 5.c) shows a similar operation mechanism as Fig. 5.b), but this time based on a thermal effect, indicated by the arrow symbolizing the effect of temperature ^. An electrical current in the bypass pathheats the electric heating element 18. Once enough meltingenergy Qmeltinghas been delivered to a mechanical element that holds the preloaded spring back, a part of the mechanical element melts and releases the spring to P220511(WO) initiate the switch-over indicated by the dashed arrow.This way, the switching unit may switch irreversibly fromthe primary state to the backup state.In the following the proposed MEMS device is presented indetail. Design of the proposed MEMS device (cf. Fig. 6): The proposed switching system uses the full wafer thickness to integrate both mechanical and electrical functions. It allows the interruption-free changeover between two inputs and one output or vice versa by a nested design as shown schematically in Fig. 6. On the normally open contact(NOC) side a travel spring and mechanical locking are addedto overcome initial 400 μm gaps between the electricalcontacts (to allow deep (≤ 2 mm) trench etching andelectroplating during fabrication). The contact is held in controlled position such that when changing switch state. The inner structure travels in the wafer plane in order to toggle switch state. When locked in, it closes the normally closed contact (NCC) suspended by a split spring. In this position the split spring is loaded and applies contact force onto the NCC. On the normally open contact (NOC) side a travel spring and mechanical locking are added to overcome initial 400 μm gaps between the electrical contacts. The contact is held P220511(WO) in controlled position such that when changing switch state the inner structure makes contact with the desired force via the main spring. Changing of switch state is achieved by an electromagnetic actuator consisting of a U-shaped yoke and bar-shaped armature both with cross-section of9 mm2 and 100 μm airgap between yoke and armature. At acurrent threshold of 2 A through the 15 windings of 0.5 mm diameter copper wire, the central lock is released, the inner part travels towards the NOC. Fig. 7 a) shows in more detail a top view of an embodiment of a MEMS device according to the present invention. The depicted MEMS device is in the state following fabrication where all springs are relaxed. As can be seen, the device consists of two contacts arrangements forming a toggle switch, where the normally closed contact part (NCC) is located at the bottom area and the normally open contact part (NOC) is located at the top area of the device. The two switchable input terminals In 1 and In 2 and the outputterminal Out are subdivided and arranged on both sides ofthe device. As mentioned before Fig. 7 a) shows the device after fabrication in an unloaded state where both contact parts (NCC & NOC) are wide open (with gaps on the order of 400 µm). This is necessary during fabrication of the device in order to be able to perform deep etching of the trenches all the way through the substrate / wafer such that the sidewall have minimal tapering (thus providing good closed contact surfaces) as well as to allow optimal coating of the sidewalls by means of sputtering and electroplating copper and finally adding a surface layer of P220511(WO) electroless nickel electroless palladium immersion gold (ENEPIG). In Fig. 7 b) the individual parts of the MEMS device are labelled. The normally closed contact part NCC comprises a first contact element P5 with a first electrical contact surface C1 and a second contact element P4 with a second electrical contact surface C2, wherein the first electrical contact surface C1 is in electrical contact with the second electrical contact surface C2 in a primary state of the toggle switch (not illustrated in Fig. 7) and the first electrical contact surface C1 is electrically disconnected from the second electrical contact surface C2 in a secondary state of the toggle switch (whereby the gap of the NOC shown in Fig. 7 is wider than in operation of the device). The normally open contact part NOC comprises a third contact element P3 with a third electrical contact surface C3 and a fourth contact element P2 with a fourth electrical contact surface C4, wherein the third electrical contact surface C3 is electrically disconnected from the fourth electrical contact surface C4 in the primary state of the toggle switch and the third electrical contact surface C3 is in electrical contact with the fourth electrical contact surface C4 in the secondary state of thetoggle switch. Furthermore, the device comprises a mainspring S3 arranged between the second and third contact element C2, C3 and configured to force the first electrical contact surface C1 away from the second electrical contact surface C2 and to force the third electrical contact P220511(WO) surface C3 onto the fourth electrical contact surface C4 in the secondary state of the toggle switch. An escapement / locking mechanism L3 is necessary to hold the main spring S3 in a position where the first electrical contact surface C1 is in electrical contact with the second electrical contact surface C2 and the third electrical contact surface C3 is electrically disconnected from the fourth electrical contact surface C4 in the primary state of the toggle switch and to release the main spring S3 in the secondary state of the toggle switch. The escapement / locking mechanism L3 is adapted to receive an external force for triggering a transition from the primary state to the secondary state of the toggle switch. In order to load the spring(s), the device further comprises a travel spring S1 connected between an outer frame F of the device 100 and to a pusher element P1 including a force coupling element H1 adapted to receive a tensioning / activation tool, such as a pin, to introduce an external force onto the pusher element P1. The first, second, third and fourth contact elements P5, P4, P3, P2 and the pusher element P1 are arranged in series such that the movement of the pusher element P1 is transferred to the first, second, third and fourth contact elements P5, P4, P3, P2. In this way the device is brought into an operating position after manufacturing / fabrication, in particular into the primary state, with a tensioned main spring S3. This device in Fig. 7 is shown in an unlocked state. As will be described later on, loading of the P220511(WO) spring(s) can also be achieved by applying an external force to the second contact element P4. The escapement / locking mechanism L3 comprises a snap-fit assembly with two snap-in clamps D3 attached to holding springs S6, S7 and two snap-in areas D3' formed as part of the second contact element P4. The snap-in area D3' is formed to receive the snap-in clamp D3. The escapement / locking mechanism L3 includes a force coupling portion H3 adapted to interact with the holding springs S6, S7 when an external force is applied to the force coupling portion H3 such that the snap-fit assembly is opened and releases thetensioned main spring S3 - in order to transition from theprimary state to the secondary state. Since there are no guides (such as rails) a linear movement during the release phase of the escapement / locking mechanism L3 has to be maintained by symmetrical forces (in order to prevent torque) otherwise the escapement / locking mechanism L3 may jam. The release mechanism is designed and configured such that both snap-fit clamps D3 release simultaneously and in the same manner such that symmetrical forces are maintained (i.e., no torque is created). The device comprises a further locking mechanism L1 consisting of two further snap-fit assemblies arranged at both sides at the top of the device. This locking mechanism L1 permanently holds the travel spring S1 and the fourth contact element P2 in the operating position (-> irreversible toggle switch). P220511(WO) A positioning spring S2 is connected between the pusher element P1 and the fourth contact element P2. It adapts the positioning of the fourth contact element P2 relative to the third contact element P3 such that optimal / maximal contact is achieved when the third electrical contact surface C3 is in electrical contact with the fourth electrical contact surface C4 in the secondary state of the toggle switch. This especially allows to compensate a potential slight taper of the contact surfaces caused by the fabrication process. The second contact element P4 and the third contact element P3 are mechanically coupled with each other by means of a "piston / plunger" in "cylinder / box" type structure L2 (=connection mechanism) - whereby the elements forming the"piston / plunger" and "cylinder / box" are essentially two- dimensional flat, open structures. The piston / plunger is moveable within the cylinder / box from a first end position to an opposite second end position. Thereby, the piston / plunger and the cylinder / box are only loosely coupled and not in close fitting in order to avoid / minimise friction between the two. The piston / plunger is part of the third contact element P3 and the cylinder / box is part of the second contact element P4 or vice-versa. This enables a "make before break" mechanism, wherein during a transition from the primary state to the secondary state of the toggle switch the first electrical contact surface remains in electrical contact with the second electrical P220511(WO) contact surface whilst the third electrical contact surface establishes electrical contact with the fourth electrical contact surface, and subsequently the first electrical contact surface electrically disconnects from the second electrical contact surface. The connection mechanism L2 with the opposing stop collars D2, D2' holds the main spring S3 in position in the primary state. The escapement / locking mechanism L3 with the snap- in clamp D3 engaged in the snap-in area D3' holds the normally closed contact part (NCC with the contact surfaces C1, C2) closed in the primary state, whereby the escapement / locking mechanism L3 also holds the connection mechanism L2 in its position in the primary state. The opening between the piston / plunger and the cylinder acts as a further force coupling element H2 adapted to receive a tensioning / activation tool, such as a pin, to introduce an external force onto the second contact element P4. This allows to induce movement of the second contact element P4 within a plane of the device 100. The movement of the second contact element P4 is transferred onto the first and third contact element P5, P3 such that the device 100 is brought into the operating position after manufacturing (i.e., into the primary state) with a tensioned main spring S3. P220511(WO) An auxiliary spring S4 is attached to the frame F and connected to the second contact element P4. The stiffness of the main spring S3 is greater than the stiffness of the auxiliary spring S4. The auxiliary spring S4 serves to position the second contact element P4 and bring it to the open position in the secondary state. Loading / charging / tensioning of the spring(s): The device is fabricated as a single piece with all parts being integral. Necessarily all the springs are relaxed / tensionless. The device becomes operational / functional (after completion of the final step of metallisation) by means of a loading / charging / tensioning process. This is achieved by means of a single linear movement of the coupling point H1 and / or H2 in the plane of the device (downwards in Fig. 8) and a subsequent retraction until the locking element D1 engages. Thereby the travel spring S1 is tensioned and the upper contact is closed. The positioning spring S2 allows positional compensation (by allowing shifting of the contact location) to achieve optimal contact when transitioning to the secondary state. The further displacement increases the contact force of the upper contact. The lower contact element P3 meets thecontact element P4 (= upper contact part of the lowercontact). The upper pusher element P1 is then already beyond the locking element D1. The travel spring S1 is designed to reversibly withstand this stretch. After further advances of H1, P1, P2, P3 & P4, P4 meets P5 and P220511(WO) the lower contact is closed. The system of P1-P5 is then jointly pushed down even further together. Then the position is reached where the locking element D3 engages, whereby the contact force of lower contact increases continuously during this phase. After a short further feed to guarantee the engagement of D3, moving backwards begins. In this maximum position, the tension of the springs is also greatest and all the energies required for operation and contact forces are mechanically stored in the system. If H1 (and / or H2) is now retracted, P5 & P4 (i.e., the closed lower contact) first run back together and then remain in the pressed state due to the locking element D3. By further retracting H1, the stop collar D2 then acts and P3 stops, whereby S3 remains tensioned. Now only P2 & P1 drive back, so the upper contact is opened, much earlier (further down) than it was closed when driving in (during tensioning). P2 & P1 now move back a bit (to create the air / vacuum gap) and are then held in place by the locking element D1 in a position further down than after fabrication. The spring S1 remains taut. Its function is now only to keep P1 & P2 in place. The locking element D1 is not intended to relax / loosen. However, it would be technically possible to do this without consuming a great deal of energy, in which case the device would ultimately be back in its original state (after manufacturing) and thus be reversible. The spring S2 is relaxed. In the secondary state, it is used to ensure an optimal parallel arrangement of the two contact surfaces against each other P220511(WO) and allows the contact surface C4 to be tilted when coming into contact with the contact surface C3 (in order to compensate a potential slight taper of the contact surfaces caused by the fabrication process). Now the device is in the primary state, i.e., the lower contact is closed and the upper contact is open, i.e., mechanically separated. The trigger to transition to the secondary state is actuated by moving the force coupling element H3 upwards (in this case, electromechanically by changing the current flows as a fuse element ages). Of course, the less force that has to be generated here, the more sensitive the component is. Essentially, only the frictional force of the snap-in clamp D3 has to be overcomehere. The springs S6 & S7 are guide springs. In theprimary state, spring S7 receives a tensile force in the longitudinal (vertical) direction but is relaxed in the transverse direction (perpendicular to the actuation direction). So if D3 has been triggered, S5, S4 & S3 start to relax, i.e., P5, P4 & P3 move upwards (in Figs. 7 & 8). On the upper side, P3 reaches the position where the upper contact closes. This position is given by the locking element / tongue D1. It is designed in such a way that S3 can provide the necessary contact force. When S5 is fully relaxed, P5 stops and the upper contact opens. The dimensions are chosen in such a way that the lower contact only opens when the upper contact is closed (i.e., "make before break"). The device is now in the secondary state. The symmetrical arrangement of the escapement / locking P220511(WO) mechanism L3 allows for the transfer of the movement along the symmetry axis of the device (upwards in Figs. 7 & 8) by the release mechanism (i.e., the electromagnetic actuator in an embodiment) into a symmetrical lateral movement ofthe two snap-in clamps D3 of L3 holding P4 in place in theprimary state. A sequence of consecutive phases during loading and operation of the device are shown in Fig. 8 b). From left to right Fig. 8 b) depicts the device directly after fabrication (I), then during loading / tensioning (II), i.e., the transition from the fabricated to an operational state, then in the primary state (III), where the bottom contact is closed and the top contact is open, then during switching (IV) from the primary state to the secondary state (in a "make before break" manner, where both the top and bottom contact are briefly simultaneously closed), and finally in the secondary state (V), where the top contact is closed and the bottom contact is open. The MEMS device is packaged in a mounting frame formed by a PCB, glass or glass-like substrate. Connections from input and output terminals In 1, In 2, Out to the first, second, third and fourth contact elements P5, P4, P3, P2 are made by multiple bonded wires as shown in Fig. 9. Alternatively, instead of bond wires metallic tapes may be employed to realise the electrical connections. P220511(WO) Fig. 10 show two perspective views a) & b) of an assembled switching module with an electromechanical actuator in the form of a coil and Fe-yoke. Fabrication of the proposed MEMS device (cf. Fig. 11): As schematically shown in Fig. 11, deep reactive ion etching (DRIE) processing is applied to a 500 μm thick standard 4" Si wafer to form a monolithic MEMS device with springs targeting 0.5 N contact force, snap in clamps for holding tightened springs of the loaded system, and dedicated areas for the switching contacts at the DRIE- etched trench side walls. Dry-etching is in particular performed by means of a Bosch process (also known as pulsed or time-multiplexed etching) which results in macroscopically smooth and almost taperless trench sidewalls within a reasonable etching time. The Bosch process is a high-aspect ratio plasma etching process. This process consists of cyclic isotropic etching and fluorocarbon-based protection film deposition by quick gas switching. The SF6 plasma cycle etches silicon, and the C4F8 plasma cycle creates a protection layer. Smooth sidewalls are achieved by using for instance 0.1 second high-speed gas switching so that the scallop size is controlled to less than 5 nm while still retaining an etch rate of e.g., 2 μm / min. Furthermore, the microscopically undulated surface of the trench sidewalls created using the Bosch process results in an increase contact surface which reduces the contact resistance (cf. Fig. 12 a) & b)). A 1 P220511(WO) μm strong thermal oxide is grown in a diffusion furnace applying a wet oxidation process to provide electrical insulation up to at least 250 V. On top of the oxide a 15 nm thick titanium (Ti) adhesion layer and 400 nm thick copper (Cu) seed layer are sputtered on tilted and rotating wafers to ensure homogeneous layer formation and to reach the very bottom of the sidewalls. At this moment the seed layer covered the entire device. Subsequent patterning is achieved by photolithography with laminated dry photoresist on both side of the wafer. Thereafter, a 20 μm strong Cu layer, forming electrical conductors, was grown using electroplating. The photoresist is stripped off in potassium hydroxide (KOH) and the seed layer is removed in a Cu-etch step. Finally, standard electro-less goldplating, more specifically electroless nickel electrolesspalladium immersion gold (ENEPIG), of the copper pattern was added to achieve a low contact resistance and enabling wire bonding. This results in the following layer structure:Ti or Cr (PVD, adhesion layer): 10 – 50 nmCu (PVD, e.g. sputtered): > 400 nm to 5 µmCu EP (electro-plated): > 5 µm to 50 µmAu finish: 70 nm – 100 µmAssembly of the switching module consists of (i)electrically connecting the switch contacts to the dedicated landing pads on the frame by six parallel gold P220511(WO) wire bonds with a diameter of 20 µm on each side, (ii) mounting the bonded MEMS device on a standard two-sided printed circuit board (PCB) using an electrically conductive silver epoxy, and (iii) mounting the electromagnetic actuator onto the silicon device with a two-component epoxy. The assembled switching module according to the present invention with a Fe-yoke actuator is shown in Fig. 10 a) & b) from two different perspectives. Mechanical Properties: Displacement and force measurements of the MEMS structures showed spring constants of kM ≈ 3.4 N / mm and kS ≈ 5.1 N / mm for the main and split springs, respectively, leading to the desired contact forces of FC,M= 0.55 N at a targeted displacement of dM = 165 µm for the main spring and FC,S = 0.55 N at a displacement of dS= 115 µm for the split spring. The magnetic actuator releasing the clamping of loaded springs was characterized with respect to actuation force as a function of the actuator coil current, thereby the required release force of Fmag = 0.2 N was achieved at an airgap of 100 µm and an actuator current of IAct= 2 A. Contact Resistance: Two distinct resistance evaluations were performed: (i) on dedicated PCB strips prior to MEMS switch design and (ii) on the fabricated and assembled MEMS switches. The PCB P220511(WO) strips with widths wtrackfrom 0.1 mm to 3.0 mm forming contact areas AC from 0.01 mm2to 9.0 mm2were loaded with contact forces FCof 0.05 N to 5.0 N. The corresponding resistance measurements are found to be in the order of1 mΩ to 10 mΩ, taking nearly constant values for each ACand beyond FC> 0.5 N. Fitting to the data set using Levenberg-Marquardt method led to extracted parameters a = 1.47×10−3, b = 1.09×10−5, and = 0.35 and calculated values of RC = 1.8 mΩ and RS = 2.6 mΩ at FC = 0.5N and AC = 5.5 mm2. A contact resistance of about 0.7 mΩ at FC = 0.5 N is expected for Au / Au contacts. Secondly, switch resistances of eight assembled MEMS devices were extracted from measurements of VS at Iin < 1A. The corresponding resistances RS showed values between1.1 mΩ and 11.1 mΩ. Applying a log-normal function to themeasured resistances revealed a median value of RS,m = 3.1 mΩ and lower and higher 1σ bounds of RS,l= 1.5 mΩ and RS,h = 6.6 mΩ, respectively. In conclusion, measured switch resistances are in line with our expectation from prior PCB track based investigation and model. High current performance: High-current tests were performed with five fully assembled samples including wire-bonding and PCB mounting therebythree types of tests were executed (i) 0 A - 10 A, (ii)> 10 A until melt-down, and (iii) long-term at 10 A. In P220511(WO) the regime up to 10 A voltage drop was found to be a linear function of the input current. At Iin = 10 A values of Vm between 233 mV and 368 mV were measured, i.e., total module resistances of 23.3 mΩ to 36.8 mΩ. The mean value was extracted to be 30 mΩ. Two devices #A and #B were exposed to currents beyond 10 A until permanent damage occurred. Reason for this was found to be melt-down of bond wires which happened as a consequence of self-heating in combination with the corresponding nonlinearity due to thermal resistance increase. The devices were damaged at currents of > 13.5 A and > 14.0 A, respectively. Finally, devices #C and #F were undergoing long-term tests. They were supplied with 10 A while voltage Vmwas periodically measured over time from 3 minutes until at least four hours. During the first hour Vmand hence the module resistance decreased from 36 mΩ to 28 mΩ and from27 mΩ to 25 mΩ for the two devices, respectively, andremained nearly constant thereafter. Conclusion: A MEMS toggle switch device for handling currents up to 10 A is proposed and was successfully practically realised and tested. A dedicated Bosch process is applied in order to metalize the sidewalls of the etched trenches by means of P220511(WO) DRIE in order to gain access to the full bulk of 500 µm thick Si substrates. As the mentioned tests show, switch resistances of Au / Au coated contacts of 3 mΩ can be achieved with contact force of 0.5 N and contact area 5.5 mm2with the proposed all-mechanical design. The proposed electronics-less power switch allows hot and cold switching for power lines, safety applications in battery driven vehicles such as automotive or mobile robotics or changeover from main to spare power supplies. The proposed (irreversible or bistable) MEMS microswitch on silicon, sapphire (monocrystalline), quartz or ceramic- wafer using MEMS fabrication technologies for high volume production provides the following benefits / advantages:- Low energy for switching- Energy-free in both states- Design and material optimized for safe-life applications(i.e., reliable and low electrical resistance)- High contact force in both states with low electricalcontact resistance < 30 mΩ- Electronics-less power switch for hot and cold switchingup to at least 10 A- Applicable in combination with any kind of passive andactive electronic components (e.g., fuses, transistors, etc.)- Adjustable threshold level (resistance as voltagedivider) P220511(WO)- Compact size despite high current carrying capacity(> 10 A)- Good manufacturability: MEMS-based -> Economy of Scale –scalability for high-volume- High electrical efficiency: low contact resistance- Low energy for switching- High safety: galvanic isolation (air / vacuum gap)- Adjustable threshold level (switching)- Fully passive component – no electronics needed, noadditional supply- Long-term mechanical reliability- Broad versatility: wide range of applicationsTo further miniaturization the melting fuse links could be integrated into the packaging of the switching module as well or wire bonds could be used as fuse wires. In summary the present invention proposes a circuit protection module with a switching unit, a MEMS device for such a switching unit and methods for manufacturing and operating such a MEMS device. The MEMS device according to the present invention is adapted and configured to form a toggle switch, wherein the toggle switch comprises a normally closed contact part, a normally open contact part a main spring and an escapement / locking mechanism. The escapement / locking mechanism is configured to hold the main P220511(WO) spring in a position such that the normally closed contact part is closes and the normally open contact part is open in a primary state of the toggle switch and to release the main spring in the secondary state of the toggle switch. The main spring is configured to provide a force to close the normally closed contact part and to open the normally open contact part. P220511(WO) LIST OF REFERENCE SYMBOLS1 first current path2 second current path3 bypass current path4 source side terminal5 load side terminal6' first circuit protection device6'' second circuit protection device7' first switch point7'' second switch point8 intermediate position (branch off position ofbypass current path)9 releasable retention mechanism10 circuit protection module11 switching unit12 spring13 arrow indicating mechanism of action14 fuse array15 detector16 actuator17 coil18 electric heating elementR, R1, R2, R3, R4 resistorsFcoil force exerted based on current in coilFspring force exerted by a springFprimary fuse in primary pathFback-up fuse in back-up pathIload total current delivered to loadP220511(WO)Iprimary current in primary pathIback-up current in back-up pathL inductanceQmelting melting energyq effect of temperature100 MEMS deviceA actuator, e.g., electromechanicalC1 first electrical contact surfaceC2 second electrical contact surfaceC3 third electrical contact surfaceC4 fourth electrical contact surfaceD1 locking element / tongueD2 stop collar on "piston / plunger" of P3 / "cylinder / box" of P4D3 snap-in clampD3' snap-in areaF outer frame of the MEMS deviceH1, H2, H3 force coupling element / portionIn 1 first (input) terminalIn 2 second (input) terminalL1 further locking mechanismL2 connection mechanism: "piston / plunger" in"cylinder / box" structureL3 escapement / locking mechanismM mounting frame (e.g., PCB) for MEMS deviceNCC normally closed contact partNOC normally open contact partOut third (output) terminalP1 pusher elementP2 fourth contact elementP220511(WO)P3 third contact elementP4 second contact elementP5 first contact elementS1 travel springS2 positioning springS3 main springS4 auxiliary springS6, S7 holding springW bonding wireP220511(WO)

Claims

CLAIMS1. A circuit protection module (10) having- a source side terminal (4) and a load side terminal (5)for electrical current,- a first current path (1) between said source sideterminal and said load side terminal, said first currentpath leading through a first circuit protection device (6')and through a first switch point (7'),- a second current path (2) between said source sideterminal and said load side terminal, said second currentpath leading through a second circuit protection device(6'') and through a second switch point (7''),- a bypass current path (3), which branches off from saidsecond current path at an intermediate position (8) betweensaid second circuit protection device and said second switch point, and which bypass current path bypasses said second switch point, and- a switching unit (11) comprising said first switch pointand said second switch point, wherein said first current path and said second current path are connected in parallel to each other with respectto said source side terminal and said load side terminal,wherein the circuit protection module has a primary statein which said first current path is closed at said firstswitch point and said second current path is open at saidsecond switch point, wherein the circuit protection module has a backup state inwhich said first current path is open at said first switchP220511(WO)point and said second current path is closed at said secondswitch point, and wherein the circuit protection module is designed andconfigured to change from said primary state to said backupstate once an electric current in said bypass current pathreaches or exceeds a predetermined threshold and to stay insaid backup state when the electric current in said bypasscurrent path falls below said threshold again.

2. The circuit protection module according (10) to claim1, wherein said first switch point (7') and second switchpoint (7'') are both formed as openable and closablecontacts of a two-way switch having a common pole connected to the load side terminal.

3. The circuit protection module (10) according to claim2, wherein a releasable retention mechanism (9) holds thetwo-way switch in a position closing the first current pathand wherein the two-way switch is biased by a spring (12)towards a position closing the second current path.

4. The circuit protection module (10) according to claim3, wherein a coil (17) for producing a magnetic field formsa section of said bypass current path, and wherein saidreleasable retention mechanism comprises a ferromagneticelement and is designed to release the two-way switch oncethe force of said magnetic field produced by said coilP220511(WO)acting on said ferromagnetic element reaches or exceeds apredefined force threshold.

5. The circuit protection module (10) according to claim3, wherein an electric heating element forms a section of said bypass current path, and wherein said releasable retention mechanism is designed to release the two-way switch under exposure to thermal heat produced by saidelectric heating element (18), in particular, wherein thereleasable retention mechanism is based on a shape memoryeffect, a fusibility or a thermal expansion.

6. A MEMS device (100) adapted and configured to form atoggle switch, wherein the toggle switch comprises:^ a normally closed contact part (NCC) comprising a firstcontact element (P5) with a first electrical contact surface (C1) and a second contact element (P4) with a second electrical contact surface (C2), wherein the first electrical contact surface (C1) is in electrical contact with the second electrical contact surface (C2)in a primary state of the toggle switch and the first electrical contact surface (C1) is electrically disconnected from the second electrical contact surface (C2) in a secondary state of the toggle switch;^ a normally open contact part (NOC) comprising a thirdcontact element (P3) with a third electrical contact surface (C3) and a fourth contact element (P2) with a fourth electrical contact surface (C4), wherein the P220511(WO)third electrical contact surface (C3) is electrically disconnected from the fourth electrical contact surface (C4) in the primary state of the toggle switch and the third electrical contact surface (C3) is in electrical contact with the fourth electrical contact surface (C4) in the secondary state of the toggle switch;^ a main spring (S3) arranged between the second and thirdcontact element (C2, C3) and configured to force the first electrical contact surface (C1) away from the second electrical contact surface (C2) and to force the third electrical contact surface (C3) onto the fourth electrical contact surface (C4) in the secondary state of the toggle switch; and^ an escapement / locking mechanism (L3) configured to holdthe main spring (S3) in a position where the first electrical contact surface (C1) is in electrical contact with the second electrical contact surface (C2) and the third electrical contact surface (C3) is electrically disconnected from the fourth electrical contact surface (C4) in the primary state of the toggle switch and to release the main spring (S3) in the secondary state of the toggle switch, wherein the escapement / locking mechanism (L3) is adapted to receive an external force for triggering a transition from the primary state to the secondary state of the toggle switch.

7. The device (100) of claim 6, further comprising atravel spring (S1) connected between an outer frame (F) of the device (100) and to a pusher element (P1) including a P220511(WO)force coupling element (H1) adapted to receive a tensioning / activation tool, such as a pin, to introduce an external force onto the pusher element (P1) in order to induce movement of the pusher element (P1) within a plane of the device (100), wherein the first, second, third and fourth contact elements (P5, P4, P3, P2) and the pusher element (P1) are arranged in series such that the movement of the pusher element (P1) is transferable to the first, second, third and fourth contact elements (P5, P4, P3, P2), the movement being adapted to bring the device (100) into an operating position after manufacturing, in particular into the primary state, with a tensioned main spring (S3).

8. The device (100) of claim 6 or 7, wherein theescapement / locking mechanism (L3) comprises at least one snap-fit assembly, in particular with a snap-in clamp (D3) attached to one or more holding springs (S6, S7) and a snap-in area (D3') formed as part of the second contact element (P4), the snap-in area (D3') being formed to receive the snap-in clamp (D3), and wherein the escapement / locking mechanism (L3) in particular includes a force coupling portion (H3) adapted to interact with the one or more holding springs (S6, S7) when an external force is applied to the force coupling portion (H3) such that thesnap-fit assembly is opened and releases the tensioned mainspring (S3).

9. The device (100) of any one of claims 6 to 8, furthercomprising a further locking mechanism (L1), in particular P220511(WO)comprising at least one further snap-fit assembly, adapted to hold the travel spring (S1) and the fourth contact element (P2) in the operating position.

10. The device (100) of any one of claims 6 to 9, furthercomprising a positioning spring (S2) connected between the pusher element (P1) and the fourth contact element (P2) and adapted to adapt the positioning of the fourth contact element (P2) relative to the third contact element (P3) such that optimal / maximal contact is achieved when the third electrical contact surface (C3) is in electrical contact with the fourth electrical contact surface (C4) in the secondary state of the toggle switch.

11. The device (100) of any one of claims 6 to 10, whereinthe second contact element (P4) and the third contact element (P3) are mechanically coupled with each other by means of a piston / plunger in cylinder / box structure (L2), wherein the piston / plunger is moveable within the cylinder / box from a first end position to an opposite second end position, the piston / plunger being part of the third contact element (P3) and the cylinder / box being part of the second contact element (P4) or vice-versa.

12. The device (100) of any one of claims 6 to 11, furthercomprising an auxiliary spring (S4) attached to the main spring (S3) and connected to the second contact element P220511(WO)(P4), wherein a stiffness of the main spring (S3) is greater than a stiffness of the auxiliary spring (S4).

13. The device of any one of claims 6 to 12, wherein thedevice is based on a silicon substrate or a sapphiresubstrate or a quartz substrate or a ceramic substrate, the substrate in particular having a thickness of at least 250 µm, more particularly of at least 1 mm, for instance ofwithin a range from 250 µm to 2 mm.

14. The device (100) of any one of claims 6 to 13, whereinthe first, second, third and fourth electrical contact surface (P5, P4, P3, P2) is covered with a coating, in particular a multi-layer coating, wherein the coating or a top layer of the multi-layer coating is made of gold, in particular electroless nickel electroless palladium immersion gold, in particular having a thickness in a range from 70 nm to 100 µm, and wherein between a substrate surface and the top layer there is in particular a layer of titanium (Ti) and / or chromium (Cr) and / or one or more layers of copper (Cu), wherein the titanium (Ti) and / or the chromium (Cr) is an adhesion layer, in particular deposited by means of a PVD process and in particular has a thickness in a range from 10 to 50 nm, and wherein a base copper layer is in particular deposited by means of a PVD process, e.g., sputtered, and in particular has a thickness in a range from 400 nm to 5 µm, an wherein an additional copper layer is in particular an electro-plated copper layer, and P220511(WO)in particular has a thickness in a range from 5 µm to50 µm.

15. The device (100) of any one of claims 6 to 14, whereinall the parts / elements of the device (100) are integrally formed as one piece of a substrate.

16. The device (100) of any one of claims 6 to 15, whereinthe toggle switch is an irreversible toggle switch adapted and configured to only be able to transmission from the primary state to the secondary state and not vice-versa.

17. A switching unit with a first, second and thirdterminal, comprising:^ a MEMS device according to any one of any one of claims6 to 16, and^ an activation element adapted to trigger a switchingaction of the toggle switch from the primary state to the secondary state, wherein a first terminal, e.g., an input, of the switching module is electrically connected with the first electrical contact surface, a second terminal, e.g., a further input, of the switching module is electrically connected with the fourth electrical contact surface, and a third terminal, e.g., an output, of the switching module is electrically connected with the second and third electrical contact surface, and P220511(WO)wherein the activation element in particular comprises a coil for producing a magnetic field and a ferromagnetic element, the activation element being adapted to release the locking mechanism once the force of the magnetic fieldproduced by the coil acting on the ferromagnetic elementreaches or exceeds a predefined threshold, or wherein the activation element in particular comprises an electric heating element, the activation element being adapted to release the locking mechanism under exposure to thermal heat produced by said electric heating element, in particular wherein the activation element is based on a shape memory effect, a fusibility or a thermal expansion.

18. The circuit protection module any one of claims 1 to5, comprising the switching module according to claim 17.

19. A method for manufacturing a MEMS device according toany one any one of claims 6 to 16 comprising:- providing a silicon substrate / wafer or alternatively asapphire substrate or a quartz substrate or a ceramic substrate, respectively, the substrate in particular havinga thickness of at least 250 µm, more particularly at least1 mm, for instance in a range from 250 µm to 2 mm; and- deep reactive ion etching, in particular by means of aBosch process, or selective laser etching or anisotropic wet etching the structures / elements of the device. P220511(WO)20. The method according to claim 19, further comprisingone or more of the following steps:- growing in a diffusion furnace, e.g., a 1 μm strong,thermal oxide on the substrate by applying a wet oxidation process to provide electrical insulation of at least 250 V;- on top of the oxide an, e.g., 15 nm thick, titanium (Ti)adhesion layer and an, e.g., 400 nm thick, copper (Cu) seed layer by means of sputtering on the tilted and rotating substrate to ensure homogeneous layer formation and to reach the very bottom of the trenches / sidewalls;- patterning by means of photolithography with laminateddry photoresist on both side of the substrate;- forming an, e.g., 20 μm strong, copper (Cu) layer aselectrical conductors by means of electroplating;- stripping the photoresist, e.g., in potassium hydroxide(KOH), and removing the seed layer, e.g., in a copper (Cu) etch step;- adding, e.g., on top of the copper, a layer ofelectroless nickel electroless palladium immersion gold to achieve a low contact resistance and enable wire bonding.

21. A method for bringing a MEMS device according to anyone any one of claims 6 to 16 into the primary,biased / tensioned state after manufacturing comprising applying an external force to the pusher element thus pushing the and tensioning the main spring and engaging the locking mechanism such that. P220511(WO)22. A method for operating a MEMS device according to anyone any one of claims 6 to 16 to bring the device from theprimary, biased state to the secondary state comprising applying an external force to a lever of the locking mechanism thus disengaging the locking mechanism and releasing the main spring. P220511(WO)

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