ELECTRICAL SWITCHING MODULE AND SWITCHING DEVICE COMPRISING SUCH A MODULE

Abstract

The invention relates to an electrical switching module (1) comprising a first electrode and a second electrode forming the ends of an electrically conductive path and at least one control electrode for selectively allowing or blocking the flow of a current in the electrically conductive path. The plurality of electrodes of the switching module (1) are arranged on a main face (1a) of a package (2), the latter being formed of an electrically insulating resin entirely coating the two transistors, formed on and / or in at least one chip, arranged head-to-tail and in series in the electrically conductive path and coating conductive tracks (P) electrically associating the plurality of electrodes and the transistors. Figure 2

Description

Title of the invention: ELECTRICAL SWITCHING MODULE AND SWITCHING DEVICE COMPRISING SUCH A MODULE

[0001] The present invention relates to the field of miniaturized electronic systems with very low electrical losses, extremely fast switching and operating at high voltage, preferably greater than 600 V. These electronic systems can be used in applications for protecting electrical networks to immediately interrupt the flow of an AC or DC current, for example in a network supplying computer servers or a "micro grid" type electrical network connecting renewable energy sources such as solar panels. These electronic systems also find application for battery protection. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0002] Such protection systems use switching components based on integrated circuits, electrically arranged in the current path of the electrical network that is to be protected. These integrated circuits are controlled to change state very quickly (for example, from the on state to the off state) in order to respond to a fault in the network and prevent damage to the equipment connected to it. The desired switching time is of the order of a microsecond, or even less.

[0003] By "fault" we mean any situation leading to a significant and excessive increase in current in the network ("overcurrent" or short-circuit situation). It can also be a surge, an excessive increase in temperature, and any other anomaly likely to damage network equipment or the network itself.

[0004] The protection system is associated with or provided with a sensor, for example a current and / or voltage and / or temperature sensor depending on the nature of the fault being monitored. A control component of the protection system is associated with the sensor and the switching component in order to enable its operation.

[0005] Such protection systems use switching components based on integrated circuits whose losses (switching and / or conduction) are dissipated in the form of heat, which may require the implementation of bulky cooling means depending on the level of losses to be dissipated.

[0006] The use of integrated circuits exploiting so-called “large gap” materials, such as SiC or GaN, or “ultra large gap” materials, such as diamond, AlN or silicon oxide, gallium, makes it possible to significantly reduce the on-state resistance of these circuits (and therefore conduction losses) while maintaining the target voltage (above 600 V) and presenting reduced dimensions in comparison with more conventional integrated circuits, for example based on silicon.

[0007] Usually, a protection system uses a plurality of switching components each comprising an integrated circuit housed in a housing, these switching components being electrically arranged in parallel on a printed circuit support. This parallel arrangement makes it possible to reduce the current flowing through each component, which also tends to reduce their resistance in the on state and therefore the conduction losses in the system and the need for heat dissipation.

[0008] This parallel arrangement is however complex to implement, because it requires the use of switching components having very similar electrical characteristics (ideally identical), in particular with regard to the threshold voltage (Vth) and on-state resistance (Ron) characteristics. It also requires the design of a very sophisticated printed circuit support seeking to minimize the parasitic capacitances and / or inductances of the electrical signal routing tracks and seeking to position the control components as close as possible to the switching components in order to minimize the length of the control loop ("driving loop" according to the English terminology of the field) and thus minimize the time required for switching the system.

[0009] The object of the present invention is to remedy these problems. BRIEF DESCRIPTION OF THE INVENTION

[0010] With a view to achieving one of these aims, the subject of the invention proposes an electrical switching module comprising a plurality of electrodes, including in particular: a. a first electrode and a second electrode forming the ends of an electrically conductive path; b. at least one control electrode for selectively allowing or blocking the flow of a current in the electrically conductive path.

[0011] The plurality of electrodes of the switching module are arranged on a main face of a housing. According to the invention, the housing is formed of an electrically insulating resin completely coating two transistors, formed on and / or in at least one chip, arranged head to tail and in series in the electrically conductive path. The resin also coats conductive tracks electrically associating the plurality of electrodes and the transistors.

[0012] According to other advantageous and non-limiting characteristics of the invention, taken alone or in any technically feasible combination: - the at least one chip comprises a surface layer of material having a large gap on and in which at least one of the two is formed transistors; - the electrical path is composed, between the first electrode and the second electrode, of several parallel paths, each parallel path comprising two transistors arranged head to tail and in series; - the box has a secondary face, opposite the main face, having at least one thermal conduction pad; - the two transistors have a vertical architecture; - both transistors have a lateral architecture.

[0013] According to another aspect, the invention provides a switching device comprising a printed circuit support and, mounted on the support, a switching module as previously proposed.

[0014] According to other advantageous and non-limiting characteristics of this aspect of the invention, taken alone or in any technically feasible combination: - the switching device comprises at least one sensor electrically connected to a control component; - the switching device comprises a current sensor arranged to measure the current flowing in the electrically conductive path; - the current sensor and / or control component is integrated into the electrical switching module. Brief description of the drawings

[0015] Other characteristics and advantages will emerge from the detailed description of the invention which follows with reference to the appended figures in which:

[0016] [Fig.l]

[0017] [Fig.l] represents a first mode of implementation;

[0018] [Fig.2]

[0019] [Fig.2] represents a second mode of implementation;

[0020] [Fig.3]

[0021] [Fig.3] an example of two transistors in “head to tail” configuration;

[0022] [Fig.4]

[0023] [Fig.4] represents a switching device taking advantage of a switching module according to the invention;

[0024] [Fig.5]

[0025] [Fig.5] represents a switching module according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0026] With reference to figures 1 and 2, which illustrate two embodiments, a switching module 1 is presented in accordance with one aspect of the invention.

[0027] This switching module 1 is in the form of a housing 2, of generally parallelepiped shape, having a plurality of electrodes T1-T4 allowing it to be electrically connected to the other components of a protection system.

[0028] In particular, on a face called the "main" face of this housing, there are a first electrode T1 and a second electrode T2 forming the ends of an electrically conductive path circulating in the module 1. This path is intended to be traveled by the current electrically supplying equipment or a plurality of equipment that it is desired to protect from the occurrence of a fault, as presented in the introduction to this application. For this purpose, the switching module 1 comprises, also on the main face 1a of the housing 2, a control electrode T3 intended to receive a control signal, this signal making it possible to configure the module to selectively allow the current to flow or block it in the electrically conductive path.By arranging the electrodes of the switching module, and in particular the first electrode, the second electrode and the control electrode, on a single face of the housing 2, it is easier to mount it directly on a printed circuit support using automated manufacturing techniques.

[0029] The housing 2 of the switching module 1 has a secondary face 1b, opposite the main face 1a, having at least one thermal conduction pad Ttl, Tt2. This at least one pad has the function of evacuating the heat produced by the transistors integrated in the module 1, as will be detailed in the remainder of this description. These may be pads made of a metal, for example copper, a good thermal conductor. The thermal conduction pads T1, T2 may be associated with other heat evacuation elements, for example radiators assembled on the switching module 1, in thermal contact with the pads.

[0030] This switching function is implemented by two transistors integrated in the housing 2, arranged head to tail and in series in the electrically conductive path. The first transistor C1 and the second transistor C2 each have a source S1, S2, a drain D1, D2 and a gate G1, G2. A channel extends between the source and the drain of each transistor.

[0031] By "head to tail" we mean that the first transistor C1 and the second transistor C2 are electrically connected by their source S1,S2 or by their drain D1,D2. Such an arrangement is for example illustrated in [Fig.3], in a configuration in which the sources S1,S2 are directly connected to each other.

[0032] The transistors C1, C2 are arranged in series in the electrically conductive path, that is to say that the channels of these transistors C1, C2, extending between the source S1, S2 and the drain D1, D2, are arranged in this path, between the first electrode T1 and the second electrode T2 of the module.

[0033] This configuration allows bidirectional circulation of current in the path, and the ability to selectively block or allow this current to flow by applying an appropriate control signal to the gates G1, G2.

[0034] The transistors C1, C2 can be produced on a single semiconductor chip, or on two chips P1, P2 as is the case in the implementation modes illustrated in Figures 1 and 2.

[0035] Preferably, the semiconductor chips P1, P2 of the module 1 are composed of a substrate, relatively thick and at least 30 micrometers thick, and typically between 30 micrometers and 300 micrometers, made of a material with high thermal conductivity such as SiC, PAIN or diamond. The material of the substrate may be in monocrystalline or polycrystalline form. This substrate supports a crystalline surface layer, preferably monocrystalline, relatively thin and with a thickness of between 2 and 10 micrometers, of material having a large gap, for example chosen from SiC, GaN, TAIN, Ga2O3 or diamond. The surface layer may be the surface thickness of the substrate when the latter is monocrystalline, or be formed by deposition on this substrate or by transfer.In some cases, it may also be provided that the semiconductor chip P1,P2 is made up of the surface layer only, without the latter requiring a substrate to support it. This may for example involve removing or dismantling this substrate after the manufacture of the transistor(s) C1,C2 and before their integration into the package 2 of the module 1. At least one of the transistors C1,C2 is formed on and / or in the surface layer of a semiconductor chip P1,P2 according to any architecture that is suitable for the application and the materials chosen. These transistors may be configured to be normally on or normally off.

[0036] The use of a large gap material (i.e. having a gap threshold greater than 3eV) to form the transistor makes it possible in particular to obtain a very low resistance in the on state, a reduced semiconductor chip size, and a voltage resistance greater than 600 V, or even 1200 V, as well as a very rapid switching speed.

[0037] The source, drain and gate pads of the chip P1, P2 associated respectively with the sources S1, S2, the drains D1, D2 and the gates G1, G2 of the transistors C1, C2 are preferably formed from an aluminum-based metal and having a thickness of at least one micrometer.

[0038] In the embodiment shown in [Fig.l], the transistors C1, C2 have a vertical architecture. That is to say that the electrically conductive path circulates between the front face and the rear face of the at least one semiconductor chip P1, P2 on and in which the transistors are manufactured. The voltage resistance is ensured by the application of an electric field between the pads of source and drain of the semiconductor chip (associated with the drains D1, D2 and the sources S1, S2 of the transistors) arranged on opposite faces of this chip. The gate pad is arranged on the face carrying the source pad.

[0039] In this case, the transistors C1, C2 may correspond to transistors of JFET, MOSFET, FET, Superjunction, FinFET architecture produced on a substrate. This substrate may be solid and made of 4H SiC, GaN, AIN, diamond or even Ga2O3. It may alternatively be a composite substrate comprising a thin layer of 4H SiC transferred onto a SiC substrate, for example polycrystalline. Alternatively, these transistors C1, C2 may be produced on and in a surface layer of GaN, AIN, Ga2O3 or diamond transferred onto a monocrystalline or polycrystalline SiC substrate or a polycrystalline AIN substrate.

[0040] In the case of such a vertical architecture, it may be advantageous (for reasons of electrical and thermal resistance) for the substrate partly making up the semiconductor chip to have a relatively small thickness, less than 150 micrometers, or even less than 100 micrometers or 80 micrometers.

[0041] In the embodiment shown in [Fig. 2], the transistors C1, C2 have a lateral architecture. That is to say that the electrically conductive path runs on the surface, and not in the thickness, of the semiconductor chip P1, P2. The voltage resistance is ensured by the application of an electric field between a source pad and a drain pad (associated with the drains D1, D2 and the sources S1, S2 of the transistors) arranged on the same face of this chip, called the "front face". The gate pad is arranged on this same face. The rear face of the semiconductor chip, opposite its front face, can optionally be electrically polarized, by connecting it to the source or drain pad in order to limit certain transient effects such as trapping of electrons and / or holes.

[0042] In this case, the transistors C1, C2 may correspond to transistors of HEMT architecture. These transistors may in particular be formed on and in a surface layer of GaN arranged on a silicon substrate, or formed on a bulk SiC substrate. The transistors may also be formed on a composite substrate obtained by transferring a surface layer onto a bulk substrate. For example, it may be a transistor having a lateral architecture formed in a surface layer of AIN, Ga2O3 or diamond, transferred onto a substrate of monocrystalline or polycrystalline SiC or polycrystalline AIN.

[0043] Returning to the general description of Figures 1 and 2, conductive tracks P, advantageously made of copper for reasons of thermal and electrical conductivity, electrically associate the plurality of electrodes with the pads of the transistors C1, C2. By "track" is meant any electrically conductive structure allowing these electrodes to be electrically connected to the pads: this structure can in particular extend in a plane parallel to the main face of the housing 2 or according to its depth, in a plane perpendicular to this main face and thus constitute a via.

[0044] In the configurations shown, the first electrode T1 and the second electrode T2 are respectively connected via the conductive tracks P to the two drain pads associated with the drains D1, D2 of the transistors C1, C2. The control electrode T3 is electrically connected to the two gate pads associated with the gates G1, G2 of the transistors C1, C2.

[0045] To facilitate the electrical connection between the conductive tracks P, preferably formed of copper, and the pads associated with the transistors C1, C2, a thickness of copper can be formed on the latter, before their integration into the package 2. This metallization, typically of the order of 5 to 10 μm, can be carried out by an electrolytic type deposition on the front face and on the rear face of the chip or the semiconductor chips P1, P2.

[0046] Advantageously, to promote heat dissipation, the conductive tracks P also electrically connect the rear face of the semiconductor chip or chips P1, P2 integrated in the package 2 to the thermal conduction electrode(s) Ttl, Tt2. In the case of the vertical architecture shown in [Fig.l], the rear faces of the chips constituting the drains of the transistors Tl, T2 and having, in operation, a significant voltage difference, provision has been made to provide the secondary face 1b of the package 2 with two thermal conduction electrodes Ttl, Tt2 that are distinct and electrically insulated from each other. Conductive tracks P that are also distinct and electrically insulated connect, respectively, the two drain pads to the two thermal conduction electrodes Ttl, Tt2. In the case of the horizontal architecture shown in [Fig.2], a single thermal conduction electrode Ttl, arranged on the secondary face 1b of the case 2 is connected by conductive tracks P to the rear faces of the two semiconductor chips, here polarized at the voltage of the midpoint of the two transistors C1, C2 in series (generally a zero voltage).

[0047] It is therefore understood that the conductive tracks P ensure the dual function of electrical connection and heat dissipation. They are therefore designed to best ensure this dual function.

[0048] In an alternative configuration, it could be provided that the switching module 1 has two control electrodes, each control electrode being respectively connected, via separate tracks, to the gate pads of the two transistors C1, C2. In this case, it is necessary to develop two control signals, respectively applied independently of each other to the two control electrodes, to control the blocking or passing operation of the switching module 1. It could also be provided, as is the case in FIGS. 1 and 2, that the switching module 1 has other electrodes, for example example a midpoint electrode T4 electrically connected to the series connection point of the two transistors C1, C2, here their sources. This midpoint electrode T4 can make it possible to impose a determined voltage at this midpoint, for example a zero voltage. It can also be at least one Kelvin type electrode, connected by a Kelvin connection to a source S1, S2 or to a drain D1, D2 of the transistors C1, C2, this type of electrode being able to be made necessary during high current operation of the module.

[0049] The kelvin connection of the housing 2, as is well known to those skilled in the art, is a connection dedicated to a small signal generally originating from the source. Unlike the direct connection to the source which carries the main current, the small signal is used, which attenuates the inductive voltage changes on the control signal when switching the current. Since the device switches quickly, this inductive drop may be sufficient to turn it on or off.

[0050] It is also possible to provide an electrode or a plurality of electrodes allowing the measurement of the junction temperature of a transistor or a plurality of transistors C1, C2.

[0051] In all cases, and regardless of the number of electrodes available to the switching module 1, these are arranged on the main face 1a of the housing 2 of the module.

[0052] To complete the description of the switching module 1, it is therefore in the form of a housing 2, this housing being formed of an insulating resin completely coating the semiconductor chip(s) P1, P2 constituting the transistors C1, C2 and the conductive tracks. More generally, the insulating resin forming the housing 2 coats all of the elements integrated in the module 1. In this way, a sort of “3D” circuit support is formed in which the components and the conductive tracks are integrated, which makes it possible to form a very compact module. In addition to a reduced size, such a very compact module minimizes the length of the conductive tracks P, which makes it possible to minimize parasitic factors (resistance, inductance, capacitance).For example, the parasitic resistance of a switching module according to the present description may be less than 1 milliohm and its parasitic inductance of the order of a few nanohenries or less.

[0053] According to a particularly advantageous variant, making it possible to reduce conduction losses, the electrical path circulating between the first electrode T1 and the second electrode T2 of the switching module 1 comprises several paths parallel to each other. Each parallel path comprising two transistors arranged head-to-tail and in series, according to the description which has just been given. These transistors can be formed on a single semiconductor chip or on a plurality of such chips, as in the implementation modes just described.

[0054] In all cases, to serve the intended applications, it is sought to obtain a switching module 1 whose resistance in the on state is less than 5 milliohms, typically of the order of 2-3 milliohms and ideally of the order of 1 milliohm. Its voltage resistance is greater than 600 V and can extend to 2000 V.

[0055] [Fig. 4] represents a switching device D taking advantage of the module 1 which has just been presented. The device D is composed of a printed circuit support 4, very conventionally having routing tracks for electrically and functionally connecting various components together. On this support 4, we find the switching module 1, crossed by the electrically conductive path I and comprising the two transistors C1, C2. Intercepting this path I, on the support 4, we also have a current sensor K associated with a control component 3. The current sensor and the control component make it possible to detect an excessive current, the intensity of which exceeds a predetermined threshold. The current sensor K produces a detection signal for the current flowing in the path I, this detection signal being transmitted to the control device 3.This is configured to produce a control signal on the control electrode T3 of the switching module 1, this signal corresponding, in normal operation, to the on state of the module. When, however, the detection signal produced by the current sensor K and communicated to the control component 3, detects that the intensity in the current path I is excessive, this control component 3 is then configured to produce a control signal on the control electrode T3 of the switching module 1, causing it to switch into a blocking state.

[0056] In the illustration of [Fig.4], an initialization signal INIT has been provided, which can for example be connected to a push button or to a supervision unit, connected to the control component 3, to reset this component and, for example, to allow the switching module 1 to switch back to a passing state and to return to normal operation of the device D.

[0057] In this illustration, a temperature sensor T is also provided, connected to the control component to, similar to the operation of the current sensor K, cause the switching module 1 to switch over, when the temperature exceeds a predetermined threshold value. It could be provided that the temperature sensor is not carried by the printed circuit support 4, but integrated into equipment under surveillance.

[0058] For the sake of readability, the elements attached to the device D have been omitted from the illustration in [Fig. 4], for example those enabling the control component 3 and the sensors K, T to be electrically powered or those enabling the support 4 to be connected to the rest of the system.

[0059] It is naturally possible to envisage that at least some of the components carried by the printed circuit support 4 are directly integrated into the switching module 1. As an illustration of this approach, [Fig. 5] shows such a switching module 1 integrating in the housing, in addition to the transistors C1, C2, the current sensor K and a control circuit 3, reproducing the functionalities of the control component 3 of [Fig. 4].

[0060] Of course, the invention is not limited to the embodiments described and variant embodiments can be made without departing from the scope of the invention as defined by the claims.

[0061] In particular, the concepts presented in the present description can be extended to a simple series arrangement of the two transistors, without them necessarily being arranged head to tail. In this way, a half-bridge circuit can be formed, the transistors then being controlled by independent control signals and respectively applied to their gate electrode.

Claims

Claims

1. Electrical switching module (1) comprising a plurality of electrodes (T1-T4) including in particular: a. a first electrode (T1) and a second electrode (T2) forming the ends of an electrically conductive path; b. at least one control electrode (T3) for selectively allowing or blocking the passage of a current in the electrically conductive path; the plurality of electrodes (T1-T4) of the switching module (1) being arranged on a main face (la) of a housing (2), the housing (2) being formed of an electrically insulating resin entirely coating two transistors (C1, C2), formed on and / or in at least one chip (P1, P2), arranged head to tail and in series in the electrically conductive path and coating conductive tracks (P) electrically associating the plurality of electrodes (T1-T4) and the transistors (C1, C2).

2. Electrical switching module (1) according to the preceding claim in which the at least one chip (P1, P2) comprises a surface layer of material having a large gap on and in which at least one of the two transistors (C1, C2) is formed.

3. Electrical switching module (1) according to one of the preceding claims in which the electrical path is composed, between the first electrode (T1) and the second electrode (T2), of several parallel paths, each parallel path comprising two transistors arranged head to tail and in series.

4. Electrical switching module (1) according to one of the preceding claims in which the housing (2) has a secondary face (1b), opposite the main face (1a), having at least one thermal conduction pad (Ttl, Tt2).

5. Electrical switching module (1) according to one of the preceding claims in which the two transistors (C1, C2) have a vertical architecture.

6. Electrical switching module (1) according to one of claims 1 to 4 in which the two transistors (C1, C2) have a lateral architecture.

7. Switching device (D) comprising a printed circuit support (4) and, mounted on the support, a switching module (1) according to one of the preceding claims.

8. Switching device (D) according to the preceding claim comprising at least one sensor (K,T) electrically connected to a control component (3).

9. Switching device (D) according to the preceding claim comprising a current sensor arranged to measure the current flowing in the electrically conductive path.

10. Switching device (D) according to the preceding claim wherein the current sensor and / or the control component (3) is integrated in the electrical switching module (1).

Images