U.S. patent application number 15/172030 was filed with the patent office on 2016-12-08 for pyrotechnic device for an electronic circuit.
This patent application is currently assigned to Commissariat a l'Energie Atomique et aux Energies Alternatives. The applicant listed for this patent is Commissariat a l'Energie Atomique et aux Energies Alternatives. Invention is credited to Pierre Perichon.
Application Number | 20160356587 15/172030 |
Document ID | / |
Family ID | 54608616 |
Filed Date | 2016-12-08 |
United States Patent
Application |
20160356587 |
Kind Code |
A1 |
Perichon; Pierre |
December 8, 2016 |
PYROTECHNIC DEVICE FOR AN ELECTRONIC CIRCUIT
Abstract
A pyrotechnic device including at least one layer of a
pyrotechnic material deposited on all or part of an electronic
circuit, the pyrotechnic material being capable of being triggered
by a heating of the circuit due to a failure thereof.
Inventors: |
Perichon; Pierre; (Voiron,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Commissariat a l'Energie Atomique et aux Energies
Alternatives |
Paris |
|
FR |
|
|
Assignee: |
Commissariat a l'Energie Atomique
et aux Energies Alternatives
Paris
FR
|
Family ID: |
54608616 |
Appl. No.: |
15/172030 |
Filed: |
June 2, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01H 39/006 20130101;
F42C 15/40 20130101; H01H 37/76 20130101 |
International
Class: |
F42C 15/40 20060101
F42C015/40 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 4, 2015 |
FR |
15/55091 |
Claims
1. A pyrotechnic device comprising: one or a plurality of
conductors; and at least one layer of a pyrotechnic material
deposited on all or part of an electronic circuit, the pyrotechnic
material being capable of being triggered by a heating of the
circuit due to a failure thereof, the pyrotechnic effect causing
the breaking of said conductor(s).
2. The device of claim 1, wherein the explosion of the pyrotechnic
material is triggered by a hot spot at the level of the
conductor(s).
3. The device of claim 1, having a plurality of said conductors
electrically in parallel, the explosion of the pyrotechnic material
causing the breaking of all the conductors electrically in
parallel.
4. The device of claim 1, further comprising at least one rigid
element capable of being propelled towards the conductor(s) by the
pyrotechnic gases.
5. The device of claim 1, wherein the thickness of the pyrotechnic
material is in the range from 10 to 100 micrometers.
6. The device of claim 1, wherein the pyrotechnic material is
electrically insulating.
7. An electronic device comprising: an electronic circuit; and the
pyrotechnic device of claim 1.
8. The device of claim 7, further comprising a package at least
partially covering the electronic circuit and the pyrotechnic
device.
9. The device of claim 8, wherein the package is formed of an
encapsulation material covering the circuit and the pyrotechnic
device and at least partially embedding the conductor(s).
10. The device of claim 8, wherein the package is hollow.
11. The device of claim 7, wherein the electronic circuit
integrates a power switch.
12. A method of forming the pyrotechnic device of claim 1, wherein
a pyrotechnic material is deposited in the liquid state on the
electronic circuit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the priority benefit of French
patent application number 15/55091, the content of which is hereby
incorporated by reference in its entirety to the maximum extent
allowable by law.
BACKGROUND
[0002] The present disclosure generally relates to electronic
circuit and, more particularly, to an electronic power component or
circuit equipped with a pyrotechnic security.
DISCUSSION OF THE RELATED ART
[0003] In power electronic circuits, power components (power
transistors, diodes, thyristors, triacs, etc.) having automated or
controlled switching functions are used. Such components can for
example be found in motor control inverters (typically, in an
electric vehicle), power converters, as well as in power cutout
switches such as circuit breakers, static contactors, etc.
[0004] In case of a failure of a power switch, it is particularly
important for this failure to take the form of an opening of the
circuit (interruption of the connection performed by the power
component) and not of a short-circuit. Indeed, a short-circuit
failure may take the form of a short-circuiting of the system power
source and generate very high currents of several thousands of
amperes. Such currents generate overheatings such that the system
may catch fire, which is particularly dangerous.
[0005] The use of a fuse between the power source and the
electronic power system sometimes appears to be insufficient.
[0006] The use of pyrotechnic elements has already been provided to
cause an opening of an electric circuit and guarantee the opening
in open circuit and not in short-circuit in case of a failure
resulting in too high a current. Document FR-A-3005782 describes a
disconnector for a DC electric power supply source, based on an
opening of a contact by pyrotechnic triggering. The explosion of
the pyrotechnic element is controlled by an external control
element and the gases generated by the explosion spread in an
expansion chamber and actuate a movable blade which breaks the
electric conductor to be disconnected.
[0007] Document EP-A-1709335 describes a pyrotechnic microsystem
where a pyrotechnic material is deposited on a substrate. The
explosion of the pyrotechnic material generates a quantity of gas
causing an actuation. The initiation of the pyrotechnic material is
caused by a heating resistive track or wire where the flowing of a
current is triggered by a control center.
[0008] Document EP-A-1344744 describes a pyrotechnically actuated
microvalve based on the triggering of pyrotechnic material
deposited on an electric resistor.
[0009] In all such systems, an external control element causes the
triggering of the pyrotechnic charge.
SUMMARY
[0010] An embodiment overcomes all or part of the disadvantages of
usual electronic power circuits.
[0011] An embodiment provides a solution avoiding a short-circuit
failure of a power component.
[0012] An embodiment provides an improved pyrotechnic solution.
[0013] Thus, an embodiment provides a pyrotechnic device comprising
at least one layer of a pyrotechnic material deposited on all or
part of an electronic circuit, the pyrotechnic material being
capable of being triggered by a heating of the circuit due to a
failure thereof.
[0014] According to an embodiment, the breaking of one or a
plurality of conductors is caused by the pyrotechnic effect.
[0015] According to an embodiment, the explosion of the pyrotechnic
material causes the breaking of all the conductors electrically in
parallel.
[0016] According to an embodiment, the device further comprises at
least one rigid element capable of being propelled towards the
conductor(s) by the pyrotechnic gases.
[0017] According to an embodiment, the thickness of the pyrotechnic
material is in the range from 10 to 100 micrometers.
[0018] According to an embodiment, the pyrotechnic material is
electrically insulating.
[0019] An embodiment also provides an electronic device
comprising:
[0020] an electronic circuit; and
[0021] a pyrotechnic device.
[0022] According to an embodiment, the device further comprises a
package at least partially covering the electronic circuit and the
pyrotechnic device.
[0023] According to an embodiment, the package is formed of an
encapsulation material covering the circuit and the pyrotechnic
device and at least partially embedding the conductor(s).
[0024] According to an embodiment, the package is hollow.
[0025] According to an embodiment, the electronic circuit
integrates a power switch.
[0026] An embodiment provides a method of forming a pyrotechnic
device, wherein a pyrotechnic material is deposited in the liquid
state on the electronic circuit.
[0027] The foregoing and other features and advantages will be
discussed in detail in the following non-limiting description of
specific embodiments in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIGS. 1A and 1B show, respectively in perspective and in
cross-section view, and very schematically, an embodiment of an
electronic power circuit with a pyrotechnic security device;
[0029] FIGS. 2A and 2B are partial cross-section views illustrating
the triggering of the pyrotechnic security according to an
embodiment of a power circuit;
[0030] FIG. 3 is a simplified top view of another embodiment of a
power switch with a pyrotechnic security;
[0031] FIG. 4 is a simplified cross-section view of still another
embodiment of a power circuit with a pyrotechnic security,
illustrating different variations; and
[0032] FIG. 5 shows, in a simplified cross-section view, still
another embodiment of a power switch with a pyrotechnic
security.
DETAILED DESCRIPTION
[0033] For clarity, only those elements which are useful to the
understanding of the described embodiments have been shown and will
be detailed. In particular, the forming of the actual power
component (transistor, thyristor, triac, diode, etc.), that is, of
the active portion thereof, for example, made of a semiconductor
material, has not been detailed, the described embodiments being
compatible with usual technologies for manufacturing power
components (semiconductor or not). Further, the applications of the
electronic circuit integrating the power component have not been
detailed, the described embodiments being here again compatible
with usual applications of power components.
[0034] It should be noted that, in the drawings, the structural
and/or functional elements common to the different embodiments may
be designated with the same reference numerals and may have
identical structural, dimensional, and material properties.
[0035] Unless otherwise specified, expressions "approximately",
"substantially", and "in the order of" mean to within 10%,
preferably to within 5%.
[0036] The present disclosure will refer to an example of
application to an electronic circuit formed of a semiconductor
power component. It should however be noted that the embodiments
which will be described more generally apply to any electronic
circuit integrating one or a plurality of power components.
[0037] FIG. 1A and 1B show, respectively in perspective and in
cross-section view, and very schematically, an embodiment of a
power circuit with a pyrotechnic security device.
[0038] A power component 2 is for example supported by an
electronic board 1 (for example, a printed circuit board PCB).
Power component 2, for example, a diode, a transistor, a thyristor,
a triac, etc. is formed in a semiconductor substrate (for example,
made of silicon) and comprises electric contacts 22 intended to
receive conductors, for example, wires 32, of electric connection
to other elements (not shown) of the circuit or of the electronic
system.
[0039] It is provided to add to the power component a pyrotechnic
security capable of breaking one or a plurality of electric
connection conductors in case of a failure of the component.
[0040] A specificity of such a pyrotechnic security is that the
explosion is initiated by the actual failure without requiring an
external control element.
[0041] According to the embodiment shown in FIGS. 1A and 1B, the
pyrotechnic security device comprises a layer of a pyrotechnic
material 42 deposited on component 2. The function of the
pyrotechnic material is to cause a breakage of at least one
conductor 32, under the effect of the gases generated on explosion
thereof. If a plurality of conductors are electrically connected in
parallel, the pyrotechnic material causes the breaking of all these
conductors to guarantee a breaking of the electric connection.
[0042] FIGS. 2A and 2B are partial cross-section views illustrating
the triggering of the pyrotechnic security according to an
embodiment of a power component. As an example, FIGS. 2A and 2B are
considered as showing an enlargement of FIG. 1B at the level of the
active (semiconductor) area of power component 2 formed in the
semiconductor substrate. FIG. 2A illustrates the triggering of the
pyrotechnic security and FIG. 2B illustrates the action thereof on
one of conductive wires 32.
[0043] In normal operation, the current generally in the range from
some ten amperes to a few hundreds of amperes according to
circuits, which flows through active area 24 of the component
generates no temperature rise capable of making the pyrotechnic
material explode.
[0044] On occurrence of a failure in the component (for example,
breakdown of a dielectric, crack in the component, etc.), the
current conducted by conductor(s) 32 and flowing through the
component tends to concentrate in the area of the defect since the
resistance thereof is lower than in the rest of the component. This
locally generates a current increase which causes the melting of
the materials (metal, silicon, etc.) of this area, thus decreasing
the local resistance and causing a runaway effect. The hot spot
which creates and the local melting of the materials cause a
triggering of the security by the explosion of the pyrotechnic
material. The gases caused by the explosion then break conductive
wire 32 (FIG. 2B) or the conductive wires in parallel.
[0045] Thus, the security acts on (and destroys) its own triggering
element (conductive wire(s) 32). Accordingly, this guarantees an
opening of the electric circuit even if, at the level of component
2, the failure has taken the form of a short-circuit. The
mechanical breaking of conductor 32 or of the conductors
electrically in parallel guarantees that the failure results in an
open circuit. In the case of series-connected conductors, it is
sufficient to break the series connection.
[0046] It should be noted that the components and the electronic
circuit are then destroyed (the security is not resettable). This
is however the desired effect in the targeted applications.
[0047] Pyrotechnic material 42 is preferably present at least at
the level of conductors 32 to be broken by the pyrotechnic action.
This enables to improve the effect thereof.
[0048] Further, to optimize the action of the gases, the assembly
is preferably placed in a closed enclosure, as will be seen
hereafter in relation with FIG. 4.
[0049] The pyrotechnic material is preferably selected to have all
or part of the following properties:
[0050] To be an electric insulator, since it covers or joins
different conductive areas. More specifically, the leakage current
generated by the pyrotechnic material should not exceed that of the
component itself.
[0051] Not to trigger at homogeneous temperatures corresponding to
the component operating temperatures. Preferably, a pyrotechnic
material triggering at temperatures greater than approximately
150.degree. C. and preferably greater than approximately
300.degree. C. will be selected. The inventor has indeed observed
that a failure generally results in a hot spot at more than
approximately 500.degree. C. The fact for the pyrotechnic material
not to trigger below 500 or 600.degree. C. has the advantage that
it enables to deposit it on the component before certain component
soldering steps which generally generate temperatures in the range
from 300 to 400.degree. C., which would otherwise risk untimely
triggering the security.
[0052] For the combustion residue of the pyrotechnic layer to be
sufficiently insulating to avoid generating a significant leakage
current.
[0053] To be triggerable by a hot spot having a surface area of a
few square micrometers within less than from a few hundred
milliseconds to a few hundreds of microseconds.
[0054] Preferably, the integration of the pyrotechnic material is
performed at the end of the manufacturing of the component or of
the circuit, after the welding of conductors 32 on contacts 22.
[0055] The material is preferably deposited in liquid or paste form
to spread on the component and insert above conductor(s) 32. The
pyrotechnic material is for example deposited with a thickness of a
few micrometers.
[0056] As a specific embodiment, a nitrocellulose varnish which
ignites at a temperature in the range from 160 to 170.degree. C.
may be used, provided for this to be compatible with the subsequent
manufacturing steps (for example, case of a cold solder for
subsequent steps) and particularly with the encapsulation of the
component.
[0057] According to another example, the material is a polymer from
the family of glycidyl azide polymers (GAPs) which have an ignition
temperature of approximately 573.degree. C.
[0058] According to the described embodiments, it is provided to
cover the entire component or only certain areas thereof.
[0059] FIG. 3 is a simplified top view of another embodiment of a
power component with a pyrotechnic security.
[0060] According to this embodiment, pyrotechnic security device 4
comprises, in addition to pyrotechnic material layer 42, a rigid
intercalary element 44 between pyrotechnic material 42 and
conductor(s) 32. Element 44 is used as a projectile when
pyrotechnic material 42 explodes and eases the breaking of the
conductors. Preferably, element 44 is arranged on the pyrotechnic
material, for example, glued (which is easy if the pyrotechnic
material is deposited in liquid varnish form) and is located on the
conductor(s) to be disconnected. Element 44 may be one piece, as
shown in FIG. 3, or may be formed of a plurality of projectiles.
Preferably, element 44 is insulating to avoid any risk of creating
a short-circuit between conductors 32 in normal operation.
[0061] FIG. 4 is a simplified cross-section view of still another
embodiment of a power component with a pyrotechnic security,
illustrating different variations.
[0062] This embodiment features a package 6 covering the electronic
circuit and particularly power component 2.
[0063] In the example of FIG. 4, component 2 is assumed to be
connected, by one or a plurality of conductive tracks 34, for
example, made of copper, to a connection tab 35 emerging outside of
package 6. For example, track 34 forms a ground plane of the power
component or a rear surface electrode. Further, inside of the
package, an upper contact of component 2 is connected by a
conductive wire 32 to a copper track 36 of circuit 1 connected to
another connection tab 37.
[0064] In the example of FIG. 4, pyrotechnic material 42 is only
deposited on the component and on copper track 34 to surround tab
35 (and pass under tab 35 when the latter comprises horizontal
portions internal to package 6). Thus, on activation of pyrotechnic
material 42, tab 35 and wire 32 are broken.
[0065] In the example of FIG. 4, a rigid intercalary element 44 is
also provided between layer 42 and wire(s) 32.
[0066] It should be noted that, in embodiments providing a rigid
element used as a projectile, package 6 is empty, at least in the
vicinity of this element to enable the projection thereof.
[0067] According to a variation, not shown, the package is full.
For example, the assembly of component 2, material 42 and wire 32
is embedded in encapsulation resin (for example, epoxy resin). In
this case, an intermediate element 44 has no effect. However, the
fact for wire 32 to be embedded in resin results in that, when a
pyrotechnic triggering destroying the package occurs, wire 32
embedded in resin is effectively torn off.
[0068] According to a variation, illustrated in FIG. 4, to ease the
breaking of tab 35, the latter comprises a weakened area 352, for
example, a notch. The notch should however be such that tab 35
keeps a section capable of conducting the normal operation current.
The crossing of package 6 by tab 35 may possibly be a rigid
connection. This contributes to easing the breaking when the
pyrotechnic effect takes place.
[0069] According to another variation, not shown, pyrotechnic
material 42 extends all over circuit 1 inside of package 6.
[0070] FIG. 5 shows, in a simplified cross-section view, still
another embodiment of a power component with a pyrotechnic
security. According to this embodiment, two circuits 1 and 1' are
connected by a ball grid array (BGA). The interval between balls
and, preferably, between circuits 1 and 1', is filled with
pyrotechnic material. Thus, this material is used as an
encapsulation for the component while ensuring the protection
thereof.
[0071] An advantage of the embodiments which have been described is
that the security is particularly fast to trigger.
[0072] Another advantage is that the absence of a control circuit
guarantees a reliable actuation. Indeed, since the triggering is
exclusively thermal, no electronic failure risks preventing this
triggering.
[0073] Another advantage is that the security device is
particularly easy to form.
[0074] As a specific embodiment, the thickness of the pyrotechnic
material is in the range from 10 to 100 micrometers.
[0075] Various embodiments have been described. Various
alterations, modifications, and improvements will readily occur to
those skilled in the art. In particular, the practical
implementation of the described embodiments is within the abilities
of those skilled in the art based on the functional indications
given hereabove and by using existing pyrotechnic materials.
[0076] Such alterations, modifications, and improvements are
intended to be part of this disclosure, and are intended to be
within the spirit and the scope of the present invention.
Accordingly, the foregoing description is by way of example only
and is not intended to be limiting. The present invention is
limited only as defined in the following claims and the equivalents
thereto.
* * * * *