JP2001505646A - Thin-film ignition element for pyrotechnic active substances and method of manufacturing the same - Google Patents

Abstract

(57) [Summary] 1. Thin-film ignition elements for pyrotechnic active substances and their production method 2.1. The thin-film ignition elements used for the ignition of pyrotechnic agents have in most cases very high ignition voltages or initial energies. These are most often based on a purely thermal connection of the heated and evaporating ignition bridge material. 2.2. By using hafnium and / or titanium hydride as the ignition bridge layer and by a manufacturing method that is compatible with semiconductor processes, it is possible to manufacture ignition elements in a very simple and large number, wherein the default For this reason, ignition voltages in the low volt range are sufficient. At already low heating temperatures, the decomposition process of the hafnium and / or titanium hydride is activated, whereby the reaction hydrogen is liberated in particular and a plasma is formed. 2.3. Such an ignition element allows a clearly simplified control circuit for a passenger protection device in a motor vehicle, in particular for an airbag.

Description

DETAILED DESCRIPTION OF THE INVENTION         Thin-film ignition element for pyrotechnic active substances and method of manufacturing the same   The invention relates to a fireworks technical active substance according to the preamble of claim 1. Thin-film ignition element and its manufacturing method according to the preamble of claim 11. I do.   According to DE 422 22 223 A1 claims The electric igniting means described in the generic term above is known.   In a conventional ignition element, a thin wire bridge with a small resistance (2Ω) Heated and evaporated by the loose. With this purely thermal pulse At this time, the pyrotechnic active substance is ignited. At that time, the Federal Republic of Germany patent No. 4,222,223, wherein titanium, titanium nitride or titanium There has been proposed a thin film ignition bridge made of an alloy containing: Because titanium or titanium Tan nitrides have a high thermal conductivity and a high Based on the electrical resistance, a large area and uniformity of pyrotechnic active substances during melting This is because a proper heating is guaranteed. However, titanium has a melting point above 1660 ° C. Has; titanium nitride is over 2900 ° C and ordinary titanium alloy is more than Therefore, the ignition energy required for this is extremely large.   The basic method of operation is the same as that of thermal characteristics, preferably semiconductor materials, polysilicon. Other variations utilizing the components described in U.S. Pat. No. 4,708,060. I have. This takes advantage of the negative temperature coefficient of the resistive material that occurs after the elevated temperature. You. This means that in addition to heat transfer at the moment of ignition, the formation of a lean plasma and convective pressure Causes a shrinkage effect. The configuration can then be compared to a resistive bridge.   Another basic ignition scheme described in U.S. Pat. Based on the use of nitride films. This cantilever supported A synthetic band is mounted on the film that has been Is dispersed by thermal decomposition of the hydride layer (gas pressure generation) for Part of the sash (flyer) is accelerated and spaced fireworks technical work Material, where the pressure action (shock wave) of the impinging synthetic part Ignition by The electrical energy supplied is thereby firstly heat energy And pressure, which again leads to the kinetic energy of the flyer, Flyers use this kinetic energy to collide with pyrotechnic agents, Converts to pressure and heat. However, due to this multiple energy conversion, Energy loss occurs, so that the voltage used for ignition is k Must be in the V range. U.S. Pat. No. 5,508,0016 correspondingly describes Suitable materials for storing hydrogen include elements, titanium, zirconium, nickel And palladium are specified.   Generally, hydrogen accumulation in metal hydrides is also considered well known, In most cases, this is undesirable as a detrimental effect on metal strength (hydrogen damage). This Can also be used for the storage of hydrogen of interest (Bergman / Shafer: Lehrbuch der Experimentalphys ik, Vol. 6, 1992, pp. 452 et seq.).   The object of the present invention is to be able to ignite with little initial energy, And transfer it to the pyrotechnic ignition material with as little loss of efficiency as possible To develop a thin film ignition element. Thin-film ignition elements are also easier and It can be manufactured in large numbers.   According to the invention, this object is achieved by the features of the characterizing part of claim 1. The problem is solved by a manufacturing method according to the features of the characterizing part of claim 11.   With a small initial energy, hafnium and / or Physical, chemical and thermal effects from titanium hydride directly to pyrotechnic agents The coupling of energy uptake is characteristic of the present invention. Titanium or hafnium Besides the ignition bridge layer consisting of A mixture of is also provided.   In order to proceed with the ignition in this way, a low volt voltage of <50 V and several milli An initial energy in the range of the module is sufficient. At that time, almost 4 Hafnium and / or titanium which decomposes at a local temperature of 50 ° to 800 ° C. The properties of tan hydrides are important for energy savings, while A melting temperature of 60 ° C. had to be procured. At that time, the ratio of hafnium As the temperature increases, the decomposition temperature increases.   However, during the decomposition of hafnium and / or titanium hydride, atomic hydrogen is liberated. This means that there is considerable pressure between the ignition bridge layer and the pyrotechnic agent. Leads to the rise. In addition, atomic hydrogen itself is used as an igniter (oxygen and pyrotechnic agents) (A chemical reaction with the constituent parts). At that time, it leads to the formation of plasma There is also.   The metal components used, titanium, can be easily managed technically And has a basic mode of operation, so the production of reactive hydrogen released during decomposition Energy, as well as the action of the resulting plasma This also facilitates the ignition process.   The metal component used, hafnium, is superior in terms of even greater intrinsic atomic weight. The effect of reactive hydrogen released during decomposition and the effect of plasma In addition, the energy absorption is heavier due to the heavier metal atoms, Accelerate the ignition process. High in hafnium hydride for hydrogen diffusion effluent High thermal stability and even higher metal hydrogenation for already very good titanium The decomposition temperature of the material layer is more advantageous compared to another metal hydride layer, Is It is desirable for stability against the effects of thermal environment and for the overall life of the ignition element. Acts as a new thing.   This coupling of energy uptake is within the microsecond range of pyrotechnic agents. This leads to a very rapid ignition, which Very advantageous in application.   Low ignition voltage and default energy make direct and expensive electricity supply possible. Without a voltage amplifier, a car battery or the like is already sufficient. Hence these points Fire elements are particularly useful as igniters for airbags and other passenger protection devices. It can be used conveniently.   The thermal insulation layer below the ignition bridge layer provides energy loss due to heat release to the support substrate And thereby flow in the direction of the pyrotechnic agent, and thus Increase effective energy. Therefore, the structural geometry and especially the thickness of the insulation Can affect the ignition time and the minimum required ignition voltage. it can.   Applying a manufacturing process compatible with semiconductor processes and semi-conductor as a support substrate By using the body board, a sensor for monitoring the operation capability in a small space Sensors (eg humidity and temperature sensors) and controls in microelectronic circuits Integration with control and monitoring electronics is enabled. High frequency interference pulse and EMV action Circuit measures to protect the ignition element against can likewise be realized advantageously. it can.   To ensure the smallest possible junction resistance between the ignition bridge and the contacts, Forming a large area contact surface from the ignition bridge layer to the ignition bridge, and They are brought into contact with the metallization layer of the contacts as completely as possible. On the ignition bridge layer In addition to the deposition of the metallization layer, the support substrate contacting the ignition bridge layer from the opposite side Downward contacts consisting of integrated conductor track areas are also conceivable. at the time The fire bridge layer is a structured extruded on the support substrate surface or optionally in the middle It can also be deposited on a deposited metallization layer.   The ignition bridge layer between 0.2 and 2 μm is approximately 50 μΩm titanium hydride. In the case of specific resistance, 0.5 to almost 200 Ω of the total electrical resistance of the ignition bridge layer In the priority area, the very large surface area of the ignition bridge and the ignition bridge Allows good changeability due to the length and width of the jig.   The method required for producing an ignition element according to the invention is described in claim 11 Are described, especially at very low levels for conventional temperature processes. A temperature of 350 ° C. is extremely advantageous for hydrogen storage. Lower temperature ( (Less than 300 ° C.), the process duration increases significantly, while higher temperatures Temperature (over 400 ° C), the decomposition process of titanium hydride has already started And the accumulation of hydrogen is only possible under very or very difficult process conditions (pressure, etc.). It doesn't work. When the proportion of hafnium is high, the temperature durability increases.   In this connection, variants according to claim 13 are also taken into account, according to which During the deposition of the passivation layer, the local temperature is 350 Do not exceed ° C.   All manufacturing steps are compatible with manufacturing in semiconductor factories. And thus use a silicon wafer as a support substrate The silicon wafer is cut for the first time after all manufacturing steps. Therefore, it can be realized simultaneously for many ignition elements.   Next, the present invention will be described in detail with reference to examples and the accompanying drawings.   here:   FIG. 1 shows a TiHx point deposited and structured on a support substrate with a thermal insulation layer. FIG. 3 shows an ignition element with a fire bridge layer (0.2 <x <2);     FIG. 1a shows a plan view without contact metallization,     FIG. 1b shows a plan view with contact metallization, and     FIG. 1c is shown as a cross-sectional view,   FIG. 2 shows a TiHx point deposited and structured on a support substrate with a thermal insulation layer. FIG. 3 shows an ignition element with a fire bridge layer (0.2 <x <2);     Figure 2a shows a plan view without contact metallization,     Figure 2b shows a plan view with contact metallization, and     FIG. 2c is shown as a sectional view,   FIG. 3 shows the thermodynamically effective length l and width b of the ignition structure;   FIG. 4 shows a basic circuit diagram of the ignition circuit,   FIG. 5 has a pyrotechnic active substance without a thermal insulation layer and attached directly TiHx ignition bridge layer deposited on a support substrate and structured (0.2 <x Fig. 3 shows an ignition element provided with <2),   FIG. 6 shows a fireworks technical work with an insulating layer and mounted at a slight distance. TiHx ignition bridge deposited and structured on a support substrate having an application material Fig. 3 shows an ignition element with layers (0.2 <x <2);   FIG. 7 shows an ignition with contacts of an ignition bridge layer guided out of a support substrate. Indicates the element,   FIG. 8 shows an ignition element having a blocking layer on the ignition bridge.   All manufacturing steps and layers being compatible with semiconductor processes through It has a fundamental meaning for all the embodiments shown. Only one thin each Although a film ignition element is shown; this is a number of the same on a semiconductor substrate wafer. It is realized so that the ignition element has. But basically, instead of a semiconductor substrate, It is also possible to utilize a support substrate, for example a glass or ceramic surface. The indications of layer thickness, -width and -length are schematic and not to scale.   FIG. 1 shows that TiHx; (0.2 <x <2) and TiHx on a support substrate 4 having a heat insulating layer 3. And / or hafnium hydride HfHx; (0.025 <x <2) already deposited Element with a structured, hydrogenated ignition bridge layer 2 Have been.   The thermal insulation layer 3 was closed epitaxially deposited in this example. It is configured as a SiO2 layer. But basically this is the surface of the silicon substrate It can also be produced by oxidation. Yet other substances are also suitable for insulation. You. However, when the heat insulating layer 3 is used or the heat insulating layer 3 is omitted, the support substrate 4 also indicates that the ignition bridge layer 2 is not electrically short-circuited. It is important.   The contact surface 21 (see FIG. 1 a) of the ignition bridge layer It is expanded to achieve a low junction resistance. Correspondingly easy contact In order to achieve this, the contact 1 can be made as an Al layer or another layer made of a highly conductive material. (See FIGS. 1b and 1c). The dimensions of the contact surface 21 Follows touch conditions. In FIG. 1c, again the order of the layers is evident in the cross-sectional view In this case, the variable thickness d of the heat insulating layer 3 depends on the ignition point and the minimum required ignition voltage. Affects pressure. That is, when a current flows through the ignition bridge layer 2, a dangerous decomposition temperature is generated. The time to reach the temperature depends to a large extent on the thermal conductivity of the thermal insulation layer 3. Sa When a larger amount of heat can flow out to the support substrate 4 through the heat insulating layer 3, The ignition point is delayed, or more power must be converted, Means higher ignition voltage.   As FIG. 2 shows as a second embodiment, hafnium and / or titanium hydride The material layer 2 is preferably delayed in ignition time or the ignition voltage is selected to be correspondingly high, In addition, when the support substrate is not electrically conducted, the support substrate is directly deposited on the support substrate 4. You can also. In this case, the contact 1 is deposited on the structured ignition bridge layer 2 again. (See FIGS. 2b and 2c).   FIG. 3 reveals the final effective surface of the ignition bridge layer 2. This figure 3, a rectangular structure of the ignition bridge 2 having an effective length 1 and a width b is selected. ing. This structure, via the well-known equations, R = ρI / A and P = U * 2 / R, Very easily calculated theoretically, and Further, the dimensions can be easily determined in terms of manufacturing technology. Ignition time and ignition voltage Such dangerous ignition characteristics can thereby be matched.   FIG. 4 shows a basic circuit diagram of the ignition circuit. Ignition is applied to metallized contact 1 This is done by applying a voltage U which is in the low volt range. Current flow started As a result, Joule heating of the ignition bridge 2 occurs, and this ignition bridge Directly by heating and chemical decomposition (release of reactive hydrogen) and plasma discharge The ignition process in the pyrotechnical active substance 5 (see FIG. 5) mounted above is started. In so doing, the thick metal atoms and pressure cause a large area of ignition.   The arrangement of the pyrotechnical active substance 5 is, in addition to the hydrogen reaction and the plasma action, On the one hand, directly on the ignition bridge layer 2 in order to also utilize heat conduction (See FIG. 5). Or an ignition bridge, especially to take advantage of pure plasma action A small spacing 7 is realized by the intermediate layer 6 which determines the spacing for the layer 2 (FIG. 6).   At this time, FIG. 7 shows still another embodiment, in which the ignition bridge layer 2 is Contacted in the area of the contact surface 21 from the lower side opposite to the pyrotechnic active substance You. The contact 1 is embedded, for example, on the upper side of the support substrate. Between contacts 1 and ignition Below the effective area of the bridge layer 2, a heat insulating layer 3 is provided. The fire bridge layer 2 is thermally and electrically insulated from the support substrate 4. To contact 1 The carrier substrate has conductor track areas 4.1, which are, for example, It consists of a highly doped support substrate material (Si). 3. both conductor track areas 1 are insulated from one another by insulating trenches 4.2 in the carrier substrate 4 . The advantage of this embodiment is that in some cases the omission of external terminals to the Al layer and the contacts. You. Furthermore, the contact between the pyrotechnic active substance and the ignition bridge layer is simplified. And improved.   In addition to the previously described and illustrated embodiment, in particular, the ignition bridge layer For example, another circular configuration is also conceivable.   FIG. 8 shows, again in cross section, another variant embodiment of the invention. On the ignition bridge layer 2 in the effective area of the ignition bridge between the contacts 1 A blocking layer 7 is deposited. Such a blocking layer 7 of, for example, an oxide material Due to the heating process of the ignition bridge layer to the temperature required for decomposition, the pressure Can be promoted by ascent. Layer thickness and its structure (Target split position The local taper of all the blocking layers 7) can then be achieved by opening up the liberation and expansion of the reactive hydrogen. After the start, the blocking layer 7 opens at a predefined pressure and hot hydrogen gas The hot particles in the ignition bridge layer and, if formed, the plasma are also pyrotechnic Are selected to be able to reach or into the application material.   Preferably, the blocking layer 7 is also destroyed directly at the start of the reaction of the ignition bridge layer 2. It is only as thick as it can be. The blocking layer 7 does not bridge the ignition bridge layer 2 To ensure that at least what is directly on the ignition bridge layer 2 is electrically insulated It can consist of a series of materials or layers that must be made. But Heat is ignited before the destruction of the blocking layer 7 by reflection in the metallized cover layer. It is reflected back to the bridge layer 2 and thereby heats it up more quickly Therefore, partial metal deposition is considered as a cover layer of the blocking layer 7.

────────────────────────────────────────────────── ─── Continuation of front page    (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), JP, KR, U S (71) Applicant TLV Airbag Systems               Gesellsyaft Mitsut Vesiylenk             Ter Huffung             Germany Day-84544 Atsushi             Yau am in Wuerngel-Fuon             -Brown-Shuttlese 1 (72) Laucht, Horst             Germany Day 83052 Wurz             Kumiyur Hermann-Lens-Voueg             16 (72) Inventors Ehrbeck, Heinz-Veilhelm             Germany Day-24989 Dorell               Puim Winkel 3 (72) Inventor Reichart, Horst             Germany Day 01219 Dress             Den Klein Shuttle Shutase 14 (72) Inventor Teidlelle, Viktor             Germany Day 73265 Detete             Haricot Limburg Shuttlese 70 (72) Inventor Vuice, Uvue             Germany Day-09126 Siem             Nitsutsu Fetzer Shuttle 35 (72) Inventor Schjortz, Marx             Federal Republic of Germany Day-79424 Auge             N Lindenweg 8

Claims (1)

[Claims]   1. It consists of a support substrate (4) on which two electrical contacts ( 1) are connected to each other via a chemically and thermally active ignition bridge layer (2). And this ignition bridge layer has a voltage (U) applied to its contact (1). A thin-film ignition element for igniting a pyrotechnic active substance (5), The ignition bridge layer (2) is a hydrogenated hafnium and / or titanium layer; A thin-film ignition element for igniting a pyrotechnic active substance (5).   2. The ignition bridge layer (2) is ignited by a plasma discharge. The thin film ignition element according to claim 1, wherein:   3. Under the ignition bridge layer (2), towards the support substrate (4), a thermal insulation layer ( 3. The thin-film ignition element according to claim 1, wherein 3) is present.   4. The contact (1) is configured as two metallization layers and these metallization layers Contact a large area on the contact surface (21) formed from the ignition bridge layer (2). A thin-film ignition element according to one of the preceding claims, characterized in that:   5. The ignition time and the minimum required ignition voltage (U) depend on the structure of the ignition bridge layer (2). Directly adjusted by changing the geometry of the structure and by changing the thickness of the layers A thin-film ignition element according to one of the preceding claims, characterized in that:   6. The ignition bridge layer (2) has a substantially constant layer thickness of 0.2 to 2 μm A thin film ignition element according to claim 5, characterized in that:   7. The ignition time and the minimum required ignition voltage (U) are below the ignition bridge layer (2). By changing the geometry of the structure of the thermal insulation layer (3) and the thickness of the layer. Thin-film ignition element according to one of the preceding claims, characterized in that it is adjusted directly. .   8. The thermal insulation layer (3) has a substantially constant layer thickness of 0.5 to 3 μm and 8. The thin-film ignition element according to claim 7, comprising a conoxide.   9. 0.5 and 200Ω to change ignition time and minimum required ignition voltage , An ohmic resistance of the ignition bridge layer of approximately 20Ω is established, And an ignition bridge for the pyrotechnic active substance (5) and for the thermal insulation layer (3). So that the surface area of the bilayer (2) has a size between 25 and 100000 μm * 2 Wherein the structural geometry and layer thickness of the ignition bridge layer (2) are set. A thin film ignition device according to one of the preceding claims.   10. The ignition bridge layer (2) is made of titanium containing no hafnium component; And the atomic composition ratio (x) of titanium to hydrogen of titanium hydride (TiHx) is 0.5 2. The thin film point according to claim 1, wherein the thickness of the thin film point is in the range of .about.2.0. Fire element.   11. The ignition bridge layer (2) is made of hafnium containing no titanium component; And hydrogen / hafnium atomic composition ratio of the hydrogenated hafnium layer (HfHx) The above claim, wherein (x) is in the range of 0.025 to 2.0. A thin film ignition element according to one of the preceding claims.   12. Percent hydrogen content of the hydrogenated hafnium layer is not 2.25 12. The thin film according to claim 11, wherein the thickness is in the range of 66.4%. Ignition element.   13. The ignition bridge layer (2) is a hydrogenated hafnium-titanium mixture A thin-film ignition element according to one of the preceding claims, characterized in that it consists of:   14． On the ignition bridge layer (2), heat is directed towards the pyrotechnic active substance (5). An electrically and electrically insulating blocking layer (7) is applied, which comprises a material and a structure. When the pressure defined by the reaction of the ignition bridge layer (2) is reached Have destructive properties A thin-film ignition element according to one of the preceding claims, characterized in that:   15. Support substrate (4) with integrated components for ignition control The contact surface (21) of the ignition bridge layer (2) is a semiconductor substrate, (4) connected to a conductor path area (4.1) integrated therein. A thin-film ignition element according to one of the preceding claims.   16. a) first deposit a layer of titanium and / or hafnium and Structured according to the selected structural geometry of the ridge layer (2) and the contact surface (21), And   b) Next, heat treatment accumulates hydrogen, wherein the temperature during the heat treatment is preferably Maintained at about 350 ° C   A method for manufacturing a thin-film ignition element according to one of the preceding claims, characterized in that:   17． Before depositing titanium and / or hafnium, And a microelectronic circuit and a heat insulating layer (3) on the support substrate (4). 17. The method according to claim 16, wherein is realized.   18. Aluminum layer deposited after titanium and / or hafnium hydrogenation And as contacts (1), in the form of contact surfaces (21) of the ignition bridge layer (2) It is structured accordingly, preferably with the support substrate (4) and the ignition bridge layer (2) ) To maintain the temperature of the ignition bridge layer (2) below 350 ° C. 18. Method according to claim 17, characterized in that it is locally cooled.   19. Multiple ignition elements are realized on a silicon wafer as a support substrate (4) 19. The method according to claim 18, wherein the method is performed.   20. Ignition for passenger protection devices in motor vehicles, especially for airbags Use of the thin-film ignition element according to one of claims 1 to 15 as a vessel.