EP0949479B1 - Semiconductor igniter - Google Patents

Abstract

The igniter has a thermal insulation layer (104) which is limited to the ignition gap region (108) of a semiconductor layer (106). The semiconductor layer, at its end sections (110,112) held free from the thermal insulating layer, is connected fixed with a carrier (102). The semiconductor layer, is heated, with current passing in the ignition gap region, to trigger the ignition.

Description

The invention relates to a semiconductor igniter, in particular for the Gas generator of a protection system for vehicle occupants, according to the generic term of claim 1.

Semiconductor fuses of this type, which are mainly due to hot wire fuses their much lower susceptibility to interference more and more spread find are known from EP 0 762 073 A1 or US 5,309,841 and consist of a heavily p-doped or n-doped semiconductor layer between end contact pieces on an electrically insulated or non-conductive Carrier is arranged and during the passage of current to produce a ionized semiconductor plasma suddenly heated or evaporated and thereby the ignition - usually by way of a primary ignition charge - is triggered. Out Due to a high ignition efficiency, it is necessary to use a thermal Insert insulation layer between the semiconductor layer and the carrier. As a result, however, the mechanical bond deteriorates Semiconductor layer to the carrier, and there is a risk that the Semiconductor layer under the effect of thermal or dynamic loads, as occurs especially when used in a motor vehicle, and replaces the semiconductor igniter becomes inoperable.

The patent specification DE 197 02 118 C1 (Basis for the preamble of claim 1) shows for example a squib for triggering a Airbags, with a carrier and a chip, the lightly doped silicon and two electrodes having. The two electrodes are separated by a highly doped silicon area, which is intended as a heating zone. A free space is as thermal insulation to the wearer intended. The associated disadvantages in terms of strength are mentioned above.

The object of the invention is to design a semiconductor igniter of the type mentioned in the introduction, that in a simple manner in terms of production and while maintaining high ignition efficiency great structural strength is achieved.

This object is inventively characterized by that in claim 1 Semiconductor detonator solved.

The semiconductor igniter according to the invention is especially for a gas generator Protection system suitable for vehicle occupants and has a bridge-like semiconductor layer, the end portions and an intermediate ignition gap area, wherein the semiconductor layer is connected at the end to electrical contact areas to heat in an ignition-triggering manner during the passage of current in the area of the ignition, and continue to do so a carrier is provided on which the semiconductor layer is applied at the end sections and is firmly connected to the carrier, as well as a thermal insulation layer that is trench-shaped is incorporated into the carrier. The thermal insulation layer lies between the firing range and the carrier and it is local to the firing range limited.

A particularly high structural strength is achieved by the configuration, wherein nevertheless a high ignition efficiency is guaranteed. It becomes one in terms of acting Loads extremely stable support of the semiconductor layer guaranteed and the functional reliability of the semiconductor fuse without significant additional measures improved. Nevertheless, the thermal shielding required for high ignition efficiency remains of the firing range fully preserved. This has an advantageous effect spatial limitation of the thermal insulation layer on the ignition gap area of the Semiconductor layer in connection with an identical and accordingly firm connection of the bridge end sections directly to the girder.

In a particularly preferred embodiment of the invention, the semiconductor layer is at the end sections molded integrally to the carrier according to claim 2, whereby an even safer Bond between the semiconductor layer and carrier is achieved.

For reasons of a further increase in stability with a high thermal Protective effect, it is recommended according to claim 3, the thermal insulation layer from a porous, the semiconductor layer in the ignition gap area to produce supporting material, namely according to claim 4 on production simple way in that the carrier material itself, for example is locally porosized electrochemically. In this case it is porous Material according to claim 5 preferably oxidized to the thermal conductivity to further reduce the insulation layer.

Alternatively, however, it is also possible to use the semiconductor layer as claimed 6 preferred to be designed as a free-standing bridge structure in the ignition zone area, namely according to claim 7 expediently such that the first porosified insulation material is removed by etching, so that as thermal Insulation layer an air-filled under the ignition gap area and, if desired, evacuable cavity through which the thermal ignition energy losses can be reduced even more.

In a particularly preferred manner, the semiconductor layer is im Ignition zone range from an explosive combustion when heated Ignition enhancer surrounded, which after reaching a relative low temperature levels of non-electrically generated heat for the ignition process is made available. According to claim 9, the ignition enhancer expediently in the form of a with regard to one low ignition delay thin coating applied to the semiconductor layer. When using a porous insulation layer it is for reinforcement of the ignition pulse either optionally or additionally also possible porous insulation material according to claim 10 with a gaseous or to impregnate metal-containing ignition reinforcing agents.

According to claim 11, the semiconductor layer is preferably in several to each other parallel and mutually insulated bridge bridges to the beam divided, whereby with a comparatively large bridge width, which create large contact areas for those above the semiconductor layer ignition charge located is advantageous on the way between the Bridges existing gaps a thermal easily Formation of insulation layer on the underside of the bridge.

In a particularly preferred manner, the semiconductor layer is as operated in the reverse direction, when the breakdown voltage is exceeded ignition-triggering heating semiconductor element with at least one p-n transition, thus approximately as a pair of anti-parallel diodes. hereby the susceptibility to interference of the semiconductor igniter is further reduced and received a distinctly short, sharp ignition pulse.

Finally, according to claim 13, the carrier and the semiconductor layer expediently made of differently doped silicon, for example in the form of a Silicon wafers.

Fig. 1

die Aufsicht eines erfindungsgemäßen Halbleiterzünders in stark vergrößertem Maßstab;

Fig. 2

einen Schnitt des Halbleiterzünders nach Fig. 1 längs der Linie I-I;

Fig. 3

ein zweites Ausführungsbeispiel eines Halbleiterzünders mit einstückig angeformter Halbleiterbrücke in einer der Fig. 2 entsprechenden Darstellung; und

Fig. 4

ein weiteres Ausführungsbeispiel eines Halbleiterzünders mit einer mehrteiligen Halbleiterbrücke in der Aufsicht.

The invention will now be explained in more detail using several exemplary embodiments in conjunction with the drawings. They show in a highly schematic representation:

Fig. 1

the supervision of a semiconductor igniter according to the invention in a greatly enlarged scale;

Fig. 2

a section of the semiconductor igniter of Figure 1 along the line II.

Fig. 3

a second embodiment of a semiconductor igniter with integrally formed semiconductor bridge in a representation corresponding to Figure 2; and

Fig. 4

a further embodiment of a semiconductor igniter with a multi-part semiconductor bridge in supervision.

The semiconductor igniter shown in FIGS. 1 and 2 contains a carrier 2 in Form of a weakly p-doped silicon wafer, one in the carrier 2 trench-shaped thermal insulation layer 4, a semiconductor bridge 6, also made of silicon, but heavily n-doped, which is in the ignition gap area 8 supported on the thermal insulation layer 4 and on the bridge end sections 10, 12 under the same material, mechanically stronger Connection is applied directly to the carrier 2, as well as electrical Bridge end sections 10, 12 contact pieces 14, 16 covering a large area the via connection elements 18, 20 with the - not shown - ignition electronics stay in contact.

The thermal insulation layer 4 is made of the carrier material itself in the Made that the carrier 2 in electro- or photochemical way one limited locally to the ignition gap area 8 of the semiconductor bridge 6 Zone is porosized. When current passes through the semiconductor bridge 6 the thermal insulation layer 4 ensures that the electrically generated Heat is largely converted into ignition energy, so that the ignition gap material abruptly heated and thereby the ignition in the above of the semiconductor bridge 6 arranged primary ignition charge (not shown). On the other hand, those kept free by the thermal insulation layer 4 End sections 10, 12 is the semiconductor bridge 6 with regard to the acting thermal and mechanical loads securely anchored to the carrier 2. to The porous silicon layer can improve the thermal protective effect 4 at least on the area areas adjoining the ignition section area 8 be oxidized.

In order to amplify the ignition pulse, the porous insulation layer 4 with a explosive gas or gas mixture filled when the ignition section heats up 8 burns suddenly and thus additional thermal energy for the Ignition process provides. Instead, the porous surfaces the insulation layer 4 also with a thin, ignition-enhancing, for example with With the help of the so-called sol-gel process deposited metal-containing coating, for example made of Al, Mg, titanium hydride or the like.

3, where the the first embodiment corresponding elements are identified by a reference symbol increased by 100 are, the semiconductor bridge 106 at its end portions 110 and 112 integrally formed on the carrier 102, the semiconductor bridge 106 from the carrier 102 by different doping, namely on the semiconductor bridge 106 a strong n- and in the area of the carrier 102 a weak p-silicon doping, is delimited. Another difference is that the Thermal insulation layer in this embodiment from an air-filled and, if desired, evacuable, trench-shaped in the carrier material incorporated cavity 104. For this purpose it will Carrier material below the later ignition zone area 108 initially again porosized by electrochemical or photochemical means, and then the porous silicon material is removed by under-etching, so that that under the ignition section area 108, up to the bridge end sections 110, 112 extending cavity 104 is formed. Alternatively, you can the cavity 104 also directly with the aid of a plasma-technical etching attack be worked out. For ignition amplification there is a turn thin, in this case applied to the ignition gap area 108 metallic coating 22 made of Al, Mg, titanium hydride or the like. in the 3 is the construction and operation of the semiconductor igniter according to FIG same as in the first embodiment.

4, where the the previous embodiments corresponding elements by a 200 increased Reference symbols are identified, the carrier 202 and the semiconductor bridge 206 in the same way as in FIG. 3 in one piece from one Silicon wafer manufactured, but here is the porosized silicon material not etched away below the ignition gap area 208, but as thermal Insulation layer 204 remained. Furthermore, the semiconductor bridge 206 in the ignition gap area 208 into a plurality of bridge webs 24 parallel to one another divided to a wide bridge width for a large area Initiation of the primary ignition charge located above the semiconductor bridge 206 is advantageous, the electrochemical etching process for porosizing the Insulation layer 204 over the spaces between the bridge webs 24 without problems, ie without an excessively high driving depth and thus the thickness of the Insulation layer 206 to be able to perform. Instead of a division into The semiconductor bridge 206 can also have parallel bridge webs 24 with a large number be provided by etching holes or slots, via which the etching process to produce the thermal insulation layer 204.

According to FIG. 4, the semiconductor bridge 206 is also on the bridge webs 24 Kind of a semiconductor element provided with several p-n junctions, that is about - as shown - designed as an antipolar diode pair 26, which is operated in the reverse direction and changes when the Breakdown voltage heated to generate an ignition pulse. This will reduce the sensitivity to interference the semiconductor igniter further reduced and an even steeper Receive ignition pulse.

The semiconductor bridge typically has a wall thickness between 1 and 10 µm, a length between 20 and 1000 µm and a width between 20 and 300 microns (according to FIG. 4, the bridge length is about 100 microns and the Bridge width about 200 µm), the thickness of the thermal insulation layer corresponds to approximately half the bridge or web width and is approx. 30 µm, that of the metallic ignition reinforcement layer 22 at approximately 0.5 μm and the Semiconductor detonators have a total height of around 500 µm.

Claims (13)

1. A semiconductor igniter, in particular for a gas generator of a protection system for vehicle occupants, comprising
   a bridge-type semiconductor layer (6; 106; 206) comprising end portions (10, 12; 110, 112; 210, 212) and an ignition-gap region (8; 108; 208) arranged therebetween, wherein the semiconductor layer (6; 106; 206) is connected at the ends to electrical contact regions in order to heat up so as to trigger ignition when current flows in the ignition-gap region (8; 108; 208),
   a substrate (2; 102; 202) to which the semiconductor layer (6; 106; 206) is applied at its end portions (10, 12; 110, 112; 210, 212) and fixedly connected to said substrate (2; 102; 202), and
   a thermal insulating layer (4 104; 204),
   characterised in that :
   the thermal insulating layer (4 104; 204) is incorporated into the substrate (2; 102; 202) in the form of a channel, the thermal insulating layer (4 104; 204) lying between the ignition-gap region (8; 108; 208) and the substrate (2; 102; 202) and being locally limited to the ignition-gap region (8; 108; 208).
2. A semiconductor igniter according to claim 1, characterised in that the semiconductor layer (106; 206) is formed in one piece on the substrate (102; 202) at its end portions (110, 112; 210; 212).
3. A semiconductor igniter according to claim 1 or 2, characterised in that the thermal insulating layer (4; 204) comprises a porous material supporting the semiconductor layer (6; 206) in the ignition-gap region (8; 208).
4. A semiconductor igniter according to claim 3, characterised in that the porous insulating material comprises substrate material which has been rendered porous.
5. A semiconductor igniter according to claim 3 or 4, characterised in that the porous insulating material is oxidised,
6. A semiconductor igniter according to any one of the preceding claims, characterised in that the thermal insulating layer comprises a cavity (104) etched out of the substrate material.
7. A semiconductor igniter according to claim 6 in conjunction with any one of claims 3 to 5, characterised in that the cavity (104) is formed by removal of the porous insulating material.
8. A semiconductor igniter according to any one of the preceding claims, characterised in that the semiconductor layer (6; 106; 206) in the ignition-gap region (8; 108; 208) is surrounded by an ignition boosting means (22) burning explosively upon heating.
9. A semiconductor igniter according to claim 8, characterised in that the ignition boosting means (22) comprises a coating applied locally to the semiconductor layer (106).
10. A semiconductor igniter according to claim 8 in conjunction with any one of claims 3 to 5, characterised by a gaseous or metal-containing ignition boosting means introduced into the porous insulating material (4; 204).
11. A semiconductor igniter according to any one of the preceding claims, characterised in that the semiconductor layer (206) is divided into a plurality of mutually parallel bridge segments (24) thermally insulated from one another and from the substrate (202).
12. A semiconductor igniter according to any one of the preceding claims, characterised in that the semiconductor layer (206) in the ignition-gap region (208) is formed as a semiconductor element (diode pair 26) having at least one p-n junction, operated in the reverse direction and heated so as to trigger ignition when the breakdown voltage is exceeded.
13. A semiconductor igniter according to any one of the preceding claims, characterised in that the substrate (2; 102; 202) and the semiconductor layer (6; 106; 206) comprise differently doped silicon.

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