JP2017022089A - Pyrotechnic device for electronic circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pyrotechnic device that avoids a short-circuit failure of a power component.SOLUTION: A pyrotechnic device 4 includes one or more conductors 32 and at least one layer 42 of a pyrotechnic material deposited on all or part of an electronic circuit 2. The pyrotechnic material is capable of being triggered by a heating of electronic circuit 2 due to a failure of the electronic circuit 2. A pyrotechnic effect causes breaking of the one or more conductors 32. An explosion of the pyrotechnic material is triggered by a hot spot at a level of the one or more conductors 32.SELECTED DRAWING: Figure 3

Description

  The present disclosure relates generally to electronic circuits, and more specifically to power electronic components or power electronic circuits with pyrotechnic security functions.

  In the power supply electronic circuit, power supply components (power transistor, diode, thyristor, triac, etc.) having an automatic switch function or a control switch function are used. Such power components can be found, for example, in motor control inverters (typically in electric vehicles), power converters, power cut-out switches such as circuit breakers, and static contactors.

  When a power switch fails, it is particularly important that this failure takes the form of an open circuit (breaking of connections made by power supply components), not a short circuit. In fact, a short circuit failure takes the form of shorting the system power supply and may generate a very high current of several thousand amperes. Such currents cause overheating that can cause the system to ignite, which is particularly dangerous.

  The use of fuses between the power source and the power electronics system may be inadequate.

  The use of pyrotechnic elements has already been provided in the event of a failure and the current is too high, causing an electrical circuit to open and guaranteeing an open circuit rather than a short circuit.

  French Patent Application No. 3005782 describes a disconnector for a DC power supply based on the opening of a contact by a pyrotechnic trigger. The explosion of the pyrotechnic element is controlled by an external control element, and the gas produced by the explosion spreads in the expansion chamber and activates a movable blade that cuts off the conductor to be cut.

  EP 1709335 describes a pyrotechnic microsystem in which a pyrotechnic material is deposited on a substrate. The explosion of the pyrotechnic material produces an amount of gas that triggers operation. The pyrotechnic material detonation is caused by a resistively heated track or wire whose current flow is triggered by the control center.

  European Patent Application No. 1344744 describes a microvalve that operates in a pyrotechnic manner based on the trigger of a pyrotechnic material deposited on an electrical resistor.

  In all such systems, external control elements trigger pyrotechnics.

  Embodiments overcome all or some of the disadvantages of conventional power electronics.

  Embodiments provide a solution that avoids short circuit faults in power supply components.

  Embodiments provide an improved pyrotechnic solution.

  Accordingly, an embodiment is a pyrotechnic device comprising at least one layer of pyrotechnic material deposited on all or part of an electronic circuit, wherein the pyrotechnic material is a failure of the electronic circuit. A device is provided which can be triggered by heating of the electronic circuit according to

  According to an embodiment, the interruption of the one or more conductors is caused by a pyrotechnic.

  According to an embodiment, all of the electrically parallel conductors are interrupted by the explosion of the pyrotechnic material.

  According to an embodiment, the device further comprises at least one rigid element that can be advanced towards the one or more conductors by pyrotechnic gas.

  According to an embodiment, the pyrotechnic material has a thickness in the range of 10-100 micrometers.

  According to an embodiment, the pyrotechnic material has electrical insulation.

The embodiment is
Electronic circuit,
There is further provided an electronic device comprising: a pyrotechnic device.

  According to an embodiment, the electronic device further comprises a package that at least partially covers the electronic circuit and the pyrotechnic device.

  According to an embodiment, the package is formed of a sealing material that covers the electronic circuit and the pyrotechnic device and at least partially embeds the one or more conductors.

  According to an embodiment, the package is hollow.

  According to an embodiment, the electronic circuit is integrated with a power switch.

  Embodiments provide a method for forming a pyrotechnic device, wherein a pyrotechnic material is deposited in liquid form on the electronic circuit.

  The foregoing and other features and advantages are described in detail below with reference to the accompanying drawings and specific embodiments that do not limit the invention.

1 is a perspective view very schematically illustrating an embodiment of a power electronic circuit with a pyrotechnic security device. FIG. FIG. 2 is a cross-sectional view very schematically illustrating an embodiment of a power electronic circuit with a pyrotechnic security device. It is a fragmentary sectional view which shows the trigger of the pyrotechnic security function which concerns on embodiment of a power supply circuit. It is a fragmentary sectional view which shows the trigger of the pyrotechnic security function which concerns on embodiment of a power supply circuit. It is a plane schematic diagram which shows another embodiment of the power switch provided with the pyrotechnic security function. It is a cross-sectional schematic which shows another embodiment of the power supply circuit provided with the pyrotechnic security function with various modifications. It is a cross-sectional schematic diagram which shows another embodiment of the power switch provided with the pyrotechnic security function.

  For clarity, only those elements useful for understanding the described embodiments are shown and described in detail. In particular, the actual power supply components (transistors, thyristors, triacs, diodes, etc.), i.e. the formation of the active part of the power supply components formed, for example, from a semiconductor material is not detailed, and the described embodiments are ( Compatible with conventional techniques for manufacturing power components (whether or not they are semiconductors). Furthermore, the application of the electronic circuit integrating the power supply components has not been described in detail, and the described embodiments are again compatible with the normal application of the power supply components.

  In the drawings, structural and / or functional elements common to various embodiments may be denoted by the same reference numerals and may have the same structural, dimensional, and material characteristics. It should be noted.

  The expressions “approximately”, “substantially” and “degree” mean within the range of 10%, preferably within the range of 5%, unless otherwise specified.

  The present disclosure refers to an application example to an electronic circuit formed from a semiconductor power supply component. However, it should be noted that the described embodiments apply more generally to any electronic circuit that integrates one or more power supply components.

  1A and 1B are a perspective view and a cross-sectional view, very schematically illustrating an embodiment of a power supply circuit with a pyrotechnic security device, respectively.

  The power supply component 2 is supported on, for example, an electronic board 1 (for example, a printed circuit board PCB). A power supply component 2, for example, a diode, transistor, thyristor, triac, etc., is formed on a semiconductor substrate (eg, formed from silicon) and is an electrical connection to other components (not shown) of the electronic circuit or system. An electrical contact 22 configured to receive a conductor such as wire 32.

  A pyrotechnic security function has been added to power supply components that can interrupt one or more electrical connection conductors in the event of a power supply component failure.

  The peculiarity of such pyrotechnic security functions is that an explosion starts with an actual failure without the need for external control elements.

  According to the embodiment shown in FIGS. 1A and 1B, the pyrotechnic security device comprises a layer of pyrotechnic material 42 deposited on the power supply component 2. The function of the pyrotechnic material is to cause damage to at least one conductor 32 due to the effect of gas produced by the explosion of the pyrotechnic material. If multiple conductors are electrically connected in parallel, the pyrotechnic material will cause all of these conductors to be interrupted to ensure that the electrical connection is interrupted.

  2A and 2B are partial cross-sectional views showing a pyrotechnic security function trigger according to an embodiment of a power supply component. As an example, FIGS. 2A and 2B are enlarged views of FIG. 1B at the level of the active (semiconductor) region of the power supply component 2 formed on the semiconductor substrate. FIG. 2A shows a pyrotechnic security function trigger, and FIG. 2B shows the pyrotechnic security function effect on one of the conductive wires 32.

  In normal operation, current in the power supply component active region 24, typically in the range of approximately 10 amperes to several hundred amperes, due to the power supply circuit does not cause an increase in temperature that can explode the pyrotechnic material.

  When a component failure (for example, dielectric breakdown, component crack, etc.) occurs, the current flowing through the component conducted by one or more of the conductors 32 causes the resistance in the defective area of the component to be the resistance of the rest of the component. Since it is lower, it tends to concentrate in the defect area. This locally causes an increase in current that causes melting of the material (metal, silicon, etc.) in this defect region, thereby causing local resistance reduction and runaway action. The resulting hot spots and local melting of the material cause the security function to be triggered by the explosion of the pyrotechnic material. The gas generated by the explosion then blocks the conductive wire 32 (FIG. 2B) or the plurality of parallel conductive wires.

  Thus, the security function acts on (and destroys) its trigger element (one or more conductive wires 32). Therefore, even if a failure in the form of a short circuit occurs at the level of the power supply component 2, the opening of the electric circuit is guaranteed. A mechanical interruption of conductor 32 or a plurality of electrically parallel conductors ensures that the failure results in an open circuit. In the case of a plurality of conductors connected in series, it is sufficient to cut off the series connection.

  Therefore, it should be noted that parts and electronic circuits are destroyed (security function is not reconfigurable). However, this is a desired effect in the intended application.

  The pyrotechnic material 42 is preferably provided at the level of the conductor 32 which is interrupted at least by the pyrotechnic action. For this reason, the effect of the pyrotechnic material 42 can be enhanced.

  Furthermore, in order to optimize the action of the gas, the assembly is preferably placed in a closed housing, as will be shown below in connection with FIG.

  The pyrotechnic material is preferably selected to have all or part of the following properties.

-Pyrotechnic materials are electrical insulators because they cover or connect various conductive areas.
More specifically, the leakage current caused by the pyrotechnic material should not exceed the leakage current of the component itself.

– Do not trigger at a uniform temperature corresponding to the operating temperature of the part.
It is preferred that a pyrotechnic material is selected that triggers at a temperature above about 150 ° C, preferably above about 300 ° C. The inventor has actually observed that failures typically result in hot spots at temperatures above approximately 500 ° C. The fact that the pyrotechnic material does not trigger below 500 ° C or 600 ° C generally generates a temperature in the range of 300-400 ° C, which could otherwise trigger the security function when inappropriate It has the advantage that a pyrotechnic material can be deposited on the component prior to the component soldering step.

  -The non-combustible deposits in the pyrotechnic layer are sufficiently insulated to avoid significant leakage currents.

  -It can be triggered by a hot spot with a surface area of a few square micrometers, from a few hundred milliseconds to less than a few hundred microseconds.

  The integration of the pyrotechnic material is preferably carried out at the end of the production of the part or circuit after welding of the conductor 32 to the electrical contact 22.

  It is preferable to form the pyrotechnic material in a liquid or paste form in order to spread on the part and insert the one or more conductors 32 described above. The pyrotechnic material is deposited with a thickness of, for example, several micrometers.

  In a specific embodiment, ignition occurs at a temperature in the range of 160-170 ° C., provided that it is compatible with subsequent manufacturing processes (eg, low temperature solder for subsequent processes), particularly with component sealing. Nitrocellulose varnish may be used.

  According to another example, the pyrotechnic material is a polymer from the family of glycidyl azide polymers (GAP) having an ignition temperature of approximately 573 ° C.

  According to the described embodiment, this pyrotechnic material covers the whole part or only an area of the part.

  FIG. 3 is a schematic plan view showing another embodiment of a power supply component having a pyrotechnic security function.

  According to this embodiment, the pyrotechnic security device 4 includes a rigid intermediate element 44 between the pyrotechnic material layer 42 and the one or more conductors 32 in addition to the pyrotechnic material layer 42. If the pyrotechnic material 42 explodes and facilitates conductor disconnection, the intermediate element 44 is used as a projectile. The intermediate element 44 is placed on the pyrotechnic material, for example (as an easy way if the pyrotechnic material is deposited in the form of a liquid varnish) and placed on one or more conductors to be cut. It is preferred that The intermediate element 44 may be a single piece as shown in FIG. 3 or may be formed from multiple projectiles. The intermediate element 44 is preferably insulative to avoid any risk of a short circuit between the conductors 32 during normal operation.

  FIG. 4 is a schematic cross-sectional view showing still another embodiment of a power supply component having a pyrotechnic security function in various modifications.

  This embodiment features a package 6 that covers an electronic circuit, in particular a power supply component 2.

  In the example of FIG. 4, it is assumed that the power supply component 2 is connected to a connection tab 35 that extends outside the package 6 by one or more conductive tracks 34 formed, for example, from copper. For example, the track 34 forms a ground plane for a power supply component or a back electrode. Furthermore, inside the package, the upper contact of the power supply component 2 is connected by a conductive wire 32 to the copper track 36 of the circuit 1 connected to another connection tab 37.

  In the example of FIG. 4, the pyrotechnic material 42 surrounds the connection tab 35 (and passes under the connection tab 35 when the connection tab 35 has a horizontal portion inside the package 6). The film is formed only on the track 34. Therefore, when the pyrotechnic material 42 is activated, the connection tab 35 and the wire 32 are cut off.

  In the example of FIG. 4, a rigid intermediate element 44 is further provided between the pyrotechnic material layer 42 and the one or more wires 32.

  It should be noted that in embodiments where the rigid element is provided as a projectile, the package 6 is open at least in the vicinity of the rigid element to allow the rigid element to be fired.

  According to a variant not shown, the package is completely filled. For example, an assembly of the power supply component 2, the pyrotechnic material 42 and the wire 32 is embedded in a sealing resin (for example, epoxy resin). In this case, the intermediate element 44 has no effect. However, when the wire 32 is embedded in the resin, when the pyrotechnic trigger that breaks the package is generated, the wire 32 embedded in the resin is effectively torn.

  According to the variant shown in FIG. 4, the connection tab 35 has a weakened area 352, for example a notch, to facilitate the disconnection of the connection tab 35. However, the notches should be provided so that the connection tab 35 maintains a portion capable of conducting normal operating current. The intersecting portion of the package 6 by the connection tab 35 may be a hard connection portion depending on circumstances. For this reason, the interruption | blocking when the use for fireworks arises becomes easy.

  According to another variant not shown, the pyrotechnic material 42 is provided over the entire circuit 1 inside the package 6.

  FIG. 5 is a schematic cross-sectional view showing still another embodiment of a power supply component having a pyrotechnic security function.

  According to this embodiment, two circuits 1 and 1 'are connected by a ball grid array (BGA). The spacing between the balls, preferably the spacing between circuit 1 and circuit 1 ′, is filled with pyrotechnic material. Therefore, this pyrotechnic material is used for sealing parts while ensuring the protection of the parts.

  An advantage of the described embodiment is that the security trigger is particularly fast.

  Another advantage is that reliable operation is ensured by the absence of a control circuit. In fact, since the trigger is only due to heat, there is no risk that an electronic failure will interfere with this trigger.

  Another advantage is that the security device is particularly easy to form.

  As a specific embodiment, the pyrotechnic material thickness is in the range of 10-100 micrometers.

  Various embodiments have been described. Various changes, adjustments and improvements will readily occur to those skilled in the art. In particular, the practical implementation of the described embodiment is within the skill of one of ordinary skill in the art based on the above functional representation using existing pyrotechnic materials.

Claims (12)

Pyrotechnic device (4),
One or more conductors (32);
At least one layer (42) of pyrotechnic material deposited on all or part of the electronic circuit (2),
The pyrotechnic material can be triggered by heating of the electronic circuit due to a failure of the electronic circuit, and pyrotechnics cause a blockage of the one or more conductors.   The device of claim 1, wherein an explosion of the pyrotechnic material is triggered by a hot spot at the level of the one or more conductors. A plurality of the conductors electrically provided in parallel;
3. Device according to claim 1 or 2, characterized in that all the conductors (32) in electrical parallel are interrupted by the explosion of the pyrotechnic material.   The device according to any of the preceding claims, further comprising at least one rigid element (44) capable of being advanced towards the one or more conductors (32) by pyrotechnic gas. .   A device according to any of the preceding claims, characterized in that the pyrotechnic material (42) has a thickness in the range of 10-100 micrometers.   The device according to claim 1, wherein the pyrotechnic material has electrical insulation. Electronic circuit (2),
An electronic device comprising the pyrotechnic device (4) according to any one of claims 1 to 6.   The electronic device according to claim 7, further comprising a package (6) that at least partially covers the electronic circuit (2) and the pyrotechnic device (4).   The packaging body is formed of a sealing material that covers the electronic circuit and the pyrotechnic device (4) and at least partially embeds the one or more conductors (32). The electronic device according to claim 8, which is dependent on item 2.   The electronic device according to claim 8, wherein the package (6) is hollow.   The electronic device according to claim 7, wherein the electronic circuit is integrated with a power switch. A method of forming a pyrotechnic device according to any one of claims 1 to 6,
A method of depositing a pyrotechnic material in liquid form on the electronic circuit.

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