JP2006010132A - Igniter of gas generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an igniter of a gas generator superior in protective performance against discharge of static electricity. <P>SOLUTION: This igniter for the gas generator used for an air bag, includes a base board, a bridge part having an electric bridge structure of a thin film arranged on this base board by electric insulation, a pad part arranged on the base board, having the same structure as the bridge part, having the area larger than the bridge part and connected to respective end parts of the bridge part, and a pair of electric conductive lands superposed on respective these pad parts, separately arranged so as to expose the bridge part and connected to a power source; and is formed so that the contour of the four corners of a connecting part of the bridge part and the pad part has a radius of curvature of 5 μm to 100 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ignition device for a gas generator such as an air bag for protecting passengers of an automobile. In particular, the present invention relates to an ignition device that functions as an initiation device composed of an SCB (Semiconductor Bridge) having resistance to erroneous explosion due to electrostatic discharge.

  In general, SCB is a generic term for bridges manufactured by using semiconductor technology such as vapor deposition, and the structure thereof is disclosed in Reference Document 1. That is, it has two pad parts arranged with a space having a relatively larger area than the bridge part, and a bridge part extending between these pad parts, and the pad part has electrical contacts. Metallic lands that play a role are superimposed. Since the pad portion and the bridge portion are connected in a straight line, the outline of the connection portion between the bridge portion and the pad portion has a corner where the straight lines intersect.

  Further, as disclosed in the cited document 2, as an ignition initiator, in order to prevent erroneous explosion due to static electricity, a varistor, a capacitor, a diode, etc. are installed in parallel with the bridge to constitute a filter circuit, and Some of the outlines of the boundary portions with the pad portions have corners where straight lines intersect.

Further, as disclosed in Reference 3 as an ignition initiation device using a photo-etching filament, there is one in which a bridge is configured with a curve having a radius of curvature of 0.7 mm or more in order to prevent an electrostatic explosion.
US Pat. No. 6,324,979 JP 2000-108838 A US Pat. No. 6,408,758

  However, in the SCB structure disclosed in Cited Document 1, when static electricity is applied to the bridge portion, the current density increases at the corner of the connection portion with the pad portion, causing a local temperature increase. This causes problems such as the possibility of accidental explosions.

  In addition, in the apparatus disclosed in the cited document 2, in order to prevent erroneous explosion due to static electricity, a varistor, a capacitor, a diode, etc. are installed in parallel with the bridge portion, and a misfire due to static electricity is prevented by configuring a filter circuit. Although it is aimed, the outline of the boundary part between the bridge part and the pad part has a corner where straight lines intersect, so that current concentrates on this corner and ignition from the corner due to static electricity is possible Is not sufficient as a countermeasure against static electricity.

  Further, the ignition initiation device using the photoetching filament disclosed in the cited document 3 is configured in a curved shape having a radius of curvature of 0.7 mm or more. However, in the field of low energy ignition such as SCB, a bridge is generally used. If the circuit is configured with an outer contour with a radius of curvature of 0.7 mm or more, the bridge part is relatively small and energy cannot be concentrated efficiently. There is a problem that low energy ignition (several hundred μJ or less) cannot be achieved. In addition, since the semiconductor bridge ignition device has an extremely small side of 0.85 mm, there is a problem that it is practically impossible to fit the base of this size with a radius of curvature of 0.7 mm or more.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a gas generator ignition device excellent in protection against electrostatic discharge.

In order to achieve the above object, an ignition device for a gas generator according to the present invention is an ignition device for a gas generator used for an air bag or the like,
A substrate,
A bridge portion having a thin-film electrical bridge structure disposed electrically insulated on the substrate;
A pad portion disposed on the substrate and having the same structure as the bridge portion, and having a larger area than the bridge portion and connected to each end of the bridge portion;
A pair of electrically conductive lands overlaid on each of the pad portions and spaced apart to expose the bridge portion, and connected to a power source,
The four corners of the connecting portion between the bridge portion and the pad portion are formed so as to have a radius of curvature of 5 μm to 100 μm, preferably 5 μm to 50 μm.

  In such an ignition device for a gas generator, a bridge portion includes a fuel layer and a resistance layer superimposed thereon, and the fuel layer includes a reactive metal and a reactive insulator that react with each other at a high temperature. It is characterized in that at least two superposed layers are combined, and the reactive insulator has a higher resistivity than the reactive metal. By adopting such a configuration, the generated plasma is increased and the ignition reliability is improved.

  In the gas generator ignition device, the substrate is made of silicon, a diode is provided in the silicon, and a land is installed on the diode and is electrically connected. By adopting such a configuration, malfunction due to static electricity can be prevented more reliably.

  In the gas generator ignition device, the breakdown voltage of the diode is higher than the complete ignition voltage of the bridge portion. By adopting such a configuration, it is possible to more reliably prevent malfunction due to static electricity without reducing the ignition performance.

  In the gas generator ignition device as described above, the reactive metal and the reactive insulator of the fuel layer are titanium and boron, respectively. By adopting such a configuration, the ignition reliability can be further improved.

  In such a gas generator ignition device, the resistance layer is made of the same material as the reactive metal of the fuel layer, and the uppermost layer of the fuel layer is made of the reactive metal so that it also serves as the resistance layer. It is characterized by that. By adopting such a configuration, manufacturing efficiency is further improved.

  Further, in the ignition device for the gas generator, an energy material filling is provided in contact with the ignition device in a header of the ignition device assembly. Such a configuration is the most efficient configuration.

  The gas generator ignition device as described above is used for a micro gas generator or an inflator. Such a use is the most suitable use of the gas generator of the present invention.

  In the ignition device for a gas generator having the above-described configuration according to the present invention, the contours of the four corners of the connection portion between the pad portion and the bridge portion are formed to have a curvature radius of 5 μm to 100 μm. The local current concentration that occurs at the corner where the straight line intersects the straight line in the device, and the temperature concentrated at the corner is dispersed throughout the curved portion, and the maximum temperature when static electricity is applied is lowered. The temperature rise is greatly reduced. Thereby, even when static electricity of the same energy is applied, it is difficult to reach the firing temperature of the explosive at the corner of the bridge portion, and resistance to static electricity can be improved.

  Further, in the gas generator ignition device having the above-described configuration, since the connection portion between the pad portion and the bridge portion is a curve having a curvature radius of 5 μm or more, even if the bridge size is several tens of μm, it is low. Resistance to static electricity can be improved without substantially damaging energy ignition.

  Moreover, in the ignition device according to the present invention, silicon is used for the substrate, a diode is formed therein, and the diode and the bridge portion are electrically connected in parallel, so that malfunction due to electrostatic discharge can be prevented, There is an effect that the safety is remarkably improved.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIGS. 1 and 2, the gas generator ignition device 10 according to the embodiment of the present invention includes a semiconductor bridge, and a substrate 12 in which a layer of silicon oxide 14 is stacked on silicon 16. The pad portions 18a and 18b stacked on the substrate 12 separately, the bridge portion 20 connecting the pad portions 18a and 18b to each other, and the metal placed on the pad portions 18a and 18b, for example, aluminum Land 26a, 26b. These lands 26a and 26b are connected to a power source 30 such as a DC energy source composed of a battery, a DC power source, a capacitor or the like via a switch 31 by metal lead wires 28a and 28b to constitute an electric circuit. .

  The pad portions 18a and 18b and the bridge portion 20 are formed by vapor deposition as shown in FIG. 2, and the detailed configuration thereof is as shown in FIG. 3 in which the bridge portion 20 and the pad portions 18a and 18b are mutually connected. The connecting portion is formed as a curved portion 60 having a radius of curvature of 5 μm or more. As shown in FIG. 2, the bridge portion 20 and the pad portions 18a and 18b are composed of a fuel layer 22 in which a reactive metal and a reactive insulator are laminated, and a resistance layer 24 disposed thereon. Further, the lands 26a, 26b placed on the pad portions 18a, 18b can use gold, silver, nickel, chromium or other metals instead of aluminum.

  Further, the pad portions 18a and 18b and the lands 26a and 26b may be configured such that the bridge portion 20 is a trapezoidal pad portion 18a and a land 26a so that the planar shape thereof is only half shown in FIG. Further, as shown in FIG. 3B, only a half of the pad portion 18a ′ and the land 26a ′ may be formed as shown in FIG. In that case, the connection part of pad part 18a, 18a 'and the bridge part 20 needs to consist of the curve part 60 in any case.

  The ignition device 10 as shown in FIGS. 1, 2 and 3 as described above can produce a semiconductor bridge from, for example, ceramic, silicon, or glass, and the ignition device as shown in FIG. The electric insulating header base 36 in the assembly 32 is provided as a constituent member. However, the header base 36 is made of metal in order to improve thermal conductivity, and a passage 37a is formed with respect to the header base 36 in order to guide the electrical leads 28a, 28b connected to the ignition device 10 to the inside. 37b are opened and insulated by, for example, glass, and sealed with a well-known appropriate encapsulant so that moisture, liquid or other contaminants do not enter through the passage. Further, the header base 36 is welded to a pipe body 38 that forms a casing of the assembly 32, and maintains high airtightness.

  As described above, since the ignition device 10 is formed of a reactive bridge, the ignition device 10 is installed on the upper surface 36a of the header base 36, and the electrical leads 28a and 28b are connected to the land in the ignition device 10 by the connection members 34a and 34b. 26a and 26b are electrically connected. The electrical leads 28a and 28b led out from the header base 36 are connected to a DC energy source 30 as shown in FIG. Further, the tube body 38 incorporating the ignition device 10 having a semiconductor bridge accommodates therein an energy material filling 42 made of compressed powder of a material such as potassium zirconium perchlorate (ZPP), which is an energy material. ing. In addition to this, any suitable energy material such as potassium perchlorate titanium hydride or lead azide can be used as the energy material filling 42. Further, as shown in FIG. 4, the energy material filling 42 may have a plurality of types of compositions (42a, 42b) having different combustion sensitivities.

  The ignition device 10 configured as described above operates as follows with reference to FIGS. 1 to 4. In the electric circuit shown in FIG. 1, when the switch 31 is closed, a current flows through a circuit formed by the lead wires 28 a and 28 b, the aluminum lands 26 a and 26 b, and the resistance layer 24 of the bridge unit 20. The electrical energy required for either DC current or capacitor discharge is provided. At that time, in the ignition device 10 shown in FIG. 2, the resistance layer 24 of the bridge portion 20 can be heated by Joule heat to ignite the energy fillers 42 (42 a, 42 b). In order to improve, it is preferable to adopt a configuration in which plasma generation described below occurs. That is, in the ignition device assembly 32 shown in FIG. 4, since the reactive insulator layer is disposed under the resistance layer 24, the current passes through the reactive metal of the resistance layer 24 and the fuel layer 22 is heated by the Joule heat of the resistance layer 24. At that time, the 22 reactive metals and the reactive insulator in the fuel layer are vaporized and reacted in order from the upper layer to be turned into plasma. Since there is conductivity in the plasma state, an electric current flows in the plasma, the reaction proceeds to a lower layer, and finally the reaction is continued until no electric current flows or the fuel layer 22 disappears. The energy of the plasma is increased by the exothermic reaction of the fuel layer 22, and this high-energy plasma directly supplies energy to the energy material filling 24 to reach the ignition temperature or more, thereby enabling effective and reliable ignition. Bring.

  An ignition device having a semiconductor bridge according to the invention as described above is known, for example, to ignite a filling for inflating an automobile airbag or to detonate other larger explosive fillings. Applications similar to those applied to bridge wire ignition devices are possible. Accordingly, an igniter assembly 32 using the igniter according to the present invention is sufficiently reliable for the energy charge 42 to achieve its intended purpose when current is properly flowing through the electrical circuit as shown in FIG. High ignition is possible.

  Hereinafter, specific application examples of the ignition device according to the present invention as described above will be further described.

If the igniter 10 is an igniter having stacked reactive bridges 20 as shown in FIGS. 5 and 6, it can be manufactured using standard semiconductor processing equipment and methods. In this ignition device, the same numerals are used in the parts corresponding to those shown in FIGS. 1 and 2 to describe the ignition device using the tested titanium-boron bridge.
In this embodiment, for example, titanium is used as the reactive metal for the fuel layer 22 in the bridge portion, and boron is used as the reactive insulator, for example, boron. Are alternately deposited on the silicon oxide 14 of the substrate 12, and titanium is deposited under the bottom boron to improve the adhesion to the silicon oxide. The thickness of the boron layer of the fuel layer 22 can be, for example, 225 nm, the thickness of the titanium layer can be 250 nm, and a combination of the boron layer and the titanium layer is one set, and five sets are stacked. A titanium layer is further deposited on the fuel layer 22 as the resistance layer 24. The thickness of the uppermost titanium layer is, for example, 1 μm, and the substantial resistance value of the bridge portion is set to a desired value by this thickness. Can be adjusted. The bridge portion can change the average ignition voltage by changing the length, width, and thickness thereof.

  In this ignition device, a reactive bridge portion as shown in FIG. 1 is formed by using a normal masking and etching method, and furthermore, aluminum lands 26a and 26b are formed on the pad as shown in FIG. As shown in FIG. 4, the obtained ignition device is placed on the header base so as to overlap the portions 18a and 18b and the bridge portion is exposed, and the connection bodies 34a and 34b using 125 μm aluminum wires are electrically connected. The igniter assembly can be completed by connecting the lead wires 28a and 28b by a known bonding technique using ultrasonic waves or the like.

In order to confirm the effect of the ignition device according to the present invention, the susceptibility to static electricity was tested on the boundary part between the pad part and the bridge part with the same bridge size and the one having a curve with a radius of curvature of 5 μm or more. The results are shown in Table 1. This test is an average obtained by the Neyer-D method when electrostatic discharge is performed with a static electricity simulator through a static capacitance of 150 pF and a series resistance of 500 Ω on a bridge portion having a bridge size of 50 μm square as a measure of electrostatic ignition. Ignition voltage.

  From this table, it is clear that the average ignition voltage is increased when the connecting portion between the pad portion and the bridge portion is not a shape in which straight lines intersect but is a curve. That is, the sensitivity to static electricity is reduced.

  As shown in FIGS. 5 and 6, the ignition device using the semiconductor bridge according to the first embodiment is formed on a diode previously set on a silicon substrate, and the diode 51 and the resistance layer 24 are formed by the conductive land 26. Are electrically connected to each other. These parts can obtain a significant effect on static electricity when combined with a diode. These parts are manufactured on a silicon wafer as in a normal semiconductor manufacturing technique, and each part is subsequently cut into a dice and placed on a header base 36 as shown in FIG. . In the ignition device on the header base 36, 125 μm aluminum wires are used as the connecting members 34a and 34b, and the electrical leads 28a and 28b are connected by a known bonding technique using ultrasonic waves or the like to form an assembly. Can do.

It is a conceptual diagram of the ignition device of the gas generator by one embodiment of this invention. It is sectional drawing of the ignition device along line II-II of FIG. It is a top view for demonstrating the outline of the pad part and bridge | bridging part in one embodiment of this invention. 1 is a cross-sectional view of a gas generator assembly using an ignition device according to the present invention. It is a top view of the ignition device in one embodiment of the present invention. FIG. 6 is a cross-sectional view of the ignition device along line VI-VI in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ignition device 12 Board | substrate 14 Silicon oxide 16 Silicon 18a Pad part 18b Pad part 20 Bridge part 22 Fuel layer 24 Resistance layer 26a Land 26b Land 28a Electrical lead wire 28b Electrical lead wire 30 Power supply 31 Switch 32 Assembly 34a Wiring body 34b Wiring body 36 Header base 37a Passage 37b Passage 38 Tubing 42a Energy material filling 42b Energy material filling 51 Diode 52 Diode electrode pad 60 Curved portion

Claims (8)

An ignition device for a gas generator used for an air bag or the like, the ignition device comprising:
A substrate,
A bridge portion having a thin-film electrical bridge structure disposed electrically insulated on the substrate;
A pad portion disposed on the substrate and having the same structure as the bridge portion, and having a larger area than the bridge portion and connected to each end of the bridge portion;
A pair of electrically conductive lands overlaid on each of the pad portions and spaced apart to expose the bridge portion, and connected to a power source,
An ignition device for a gas generator, wherein contours of four corners of a connecting portion between the bridge portion and the pad portion are formed to have a radius of curvature of 5 µm to 100 µm.   The bridge portion includes a fuel layer and a resistance layer stacked thereon, and the fuel layer is a combination of at least two layers in which a reactive metal and a reactive insulator that react with each other at a high temperature are stacked. 2. The ignition device for a gas generator according to claim 1, wherein the reactive insulator has a resistivity higher than that of the reactive metal.   3. The substrate according to claim 1, wherein the substrate is made of silicon, a diode is provided on the silicon, and the land is disposed on the diode and is electrically connected. Gas generator ignition device.   The ignition device for a gas generator according to claim 3, wherein a breakdown voltage of the diode is higher than a complete ignition voltage of the bridge portion.   5. The ignition device for a gas generator according to claim 2, wherein the reactive metal and the reactive insulator of the fuel layer are titanium and boron, respectively.   3. The resistance layer is made of a metal made of the same material as the reactive metal of the fuel layer, and the uppermost layer of the fuel layer is made of a reactive metal so as to also serve as the resistance layer. The ignition device of the gas generator as described in any one of thru | or 5.   The ignition of the gas generator according to any one of claims 1 to 6, wherein an energy material filling is provided in contact with the ignition device in a header of the assembly of the ignition device. apparatus. The ignition device for a gas generator according to any one of claims 1 to 7, wherein the ignition device is used for a micro gas generator or an inflator.

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