JP3447336B2 - Thin film firing element - Google Patents

Abstract

PURPOSE:To obtain a secure firing by current supply by forming a thin film firing element of the agent to be oxidized, of which heat generation part is oxidized quickly with oxygen at a heat generating temperature and which generates the heat at a specified heat quantity or more per unit quantity of oxygen of the generated oxide. CONSTITUTION:As oxidant thin film layers 31, 32, copper oxide thin film at mum of thickness, which is obtained by the reaction spattering of copper as a target and led-in oxygen, and as an agent-to-be-oxidized thin film layer 30, titanium thin film at about 500 mum of thickness obtained by evaporation is used. As a ceramics board 20, aluminum is used, and as a protecting film 40, silicon oxide thin film at about 500mum of thickness is used. A firing element 11 having the laminated structure, which has a heat generation part at a central part of the board 20 and which uses titanium as agent to be oxidized and copper oxide as oxidant and in which a heat generation part of the agent-to-be-oxidized thin film 30 is pinched by the oxidant thin films 31, 32, is formed. When the agent-to-be-oxidized thin film layer of the firing element is electrified with the direct current power, a large spark, which generates the heat at 1000kj/mol or more as a standard for 1 mole of oxygen of the oxide, can be obtained in the non-active gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film ignition element used in an electric ignition device such as an automobile air bag system.

[0002]

2. Description of the Related Art In a conventional electric igniter, an explosive powder is exploded by energizing a resistor closely attached to the explosive powder to heat the explosive powder.

With respect to this resistor, the technique using a bulk material such as a nichrome wire or a thick film material has a large heat capacity, and therefore has a high-speed response required for an airbag system of an automobile, for example. However, there are drawbacks such as not being obtained and the connection of the terminal portion becoming unstable due to thermal history. Therefore, not only the thin film material is used for the resistor and the response is good, but it is also improved so that many small heating elements can be manufactured at the same time with good reproducibility by the film forming technology and etching technology used in the semiconductor manufacturing technology. For example, Japanese Patent Application Laid-Open No. 64-75896 discloses a structure of a heating element which uses a thin film bridged between terminals as a resistor and has a quick response and excellent mass productivity.

[0004]

However, in the prior art using these thin film resistors, a dangerous explosive such as lead styphnine must be used between the resistor and the gunpowder due to insufficient heat generation. However, there is a problem in safety in terms of processing and the possibility of accidental explosion during use. Furthermore, it is necessary to secure the adhesion between the resistor and the explosive by a method such that the terminal and the resistor are made flat at the tip of the resistor and the explosive is pushed in with this resistor. There is a problem that the certainty of is influenced by its physical positional relationship. Therefore, the present invention aims to improve the safety of the ignition device and improve the uncertainty of ignition without sacrificing the high-speed response and mass productivity of the thin-film resistor. For example, an airbag of an automobile. As an ignition element in a system, it is intended to provide a thin film ignition element which is safe during normal standby and which can be surely ignited by energization.

[0005]

[Means for Solving the Problems] In order to solve the above problems, the need for an explosive charge is eliminated, and instead, the ignition device itself is provided with an ignition function to ensure safety and ensure ignition. After paying attention to the fact that the oxidant can be improved, the inventors conducted extensive research and found that when an oxidizable agent composed of a thin film was used as the resistor, the heat of the chemical reaction due to oxidation was added in addition to the Joule heat due to energization, and It has been found that a large ignition element can be obtained. However, the ignition characteristics depended on the oxygen concentration in the atmosphere only with the oxidant. Therefore, if an oxidant composed of a thin film is further added to heat the oxidant and the oxidant to their respective decomposition temperatures and oxidation temperatures,
It was possible to oxidize and burn the oxidant with the oxygen generated by the decomposition of the oxidant.

The present invention has been made on the basis of the above findings, and a resistor thin film layer formed by patterning on an electrically insulating substrate so as to connect a pair of wide conducting portions on both sides with a narrow heating portion. And a firing layer that is ignited by heat from the heat generating portion, and a thin film firing element having the firing layer,
One or more oxidizable layers that are rapidly oxidized by oxygen at the exothermic temperature of the exothermic part, and have a standard heat of formation per mol of oxygen of 1000 kJ / mol or more in absolute value, and decompose at the exothermic temperature. And one or more oxidant layers that generate oxygen, and at least one oxidant layer and at least one oxidant layer are laminated. Further, the resistor thin film layer may be made of an oxidant.

The ignition layer having a laminated structure of the oxidant thin film and the oxidant thin film may be formed in the heat generating portion made of a conventional resistor thin film. Therefore, according to the present invention, on the heat generating portion formed of the resistor thin film formed on the electric insulator and patterned so as to generate heat by a predetermined Joule heat when energized, at the above heat generation temperature, particularly 500 to 1
It decomposes at a temperature of 500 ° C and rapidly oxidizes with an oxidizer thin film that generates oxygen and oxygen generated from the oxidizer, and the standard heat of formation per mol of oxygen of the generated oxide is 100 in absolute value.
The present invention also provides a thin film ignition element having an ignition layer formed by laminating an oxidant thin film having a rate of 0 kJ / mol or more. In addition to metal oxidants, some metal oxides have semiconductivity, and the oxidant layer cannot be used as an electrical insulating layer with the resistor thin film. Therefore, the thin film layer is usually formed on the resistor thin film via an insulating layer.

[0008]

According to the present invention, the oxidizer decomposes at a temperature that can be heated by the resistor thin film patterned so as to generate a predetermined Joule heat when energized, particularly at a temperature of 500 to 1500 ° C., and oxygen generated by the oxidizer is decomposed. As a result, the oxidant is rapidly oxidized, that is, burns for the first time, so that the operation stability is excellent.

By laminating the oxidizer and the oxidizer as a thin film as described above, a large spark can be obtained regardless of the oxygen concentration of the atmosphere without impairing the conventional advantages such as high-speed ignition and mass productivity of the device. An ignition element having a larger calorific value can be obtained.

When the Joule heat generated by directly energizing the oxidant thin film is utilized, that is, when the oxidant has both functions as a resistance material and an oxidant, the laminated structure is simplified. be able to.

Furthermore, the function of the resistor as an electronic component,
For example, when a temperature coefficient is strictly required, a thin film made of an electric resistance material is provided on the base of the above laminated structure,
It is preferable that an electric current be applied to the resistance thin film to generate Joule heat, and this heat heats and ignites the laminated ignition film of the oxidant and the oxidant.

The oxidizing agent used in the present invention is copper (II) oxide.
Is the best. The oxidant in the present invention controls the temperature at the ignition point and is required to have stability. A material having a decomposition temperature that is too low is not suitable, and the oxidant or resistor that becomes a heat source by energization has a melting point, and the oxidant cannot be heated to a temperature higher than that. Therefore, the oxidizer thin film is preferably a substance that decomposes at a temperature of about 500 ° C to 1500 ° C, and the decomposition temperature of copper (II) oxide is on the fairly high temperature side in this temperature range, and rapid decomposition occurs near that temperature. . In other words, although copper (II) oxide is a material that releases oxygen when heated, it is very stable at normal operating temperatures, and copper (II) oxide thin films can be easily produced by mass-production methods such as reactive sputtering. This is because it has an advantage that it can be manufactured.

Titanium or zirconium is most suitable as the oxidant in the present invention. This is because the standard heat of formation of these oxides is large, the amount of heat generated during combustion is large, and the resistivity is a relatively large metal material, which can also be used as a resistance material. Furthermore, it is not easily oxidized in the atmosphere and can be handled relatively stably, and its oxidation temperature is close to the decomposition temperature of copper (II) oxide.
In other words, these materials satisfy the characteristics as an oxidant and a resistance material, and when used in combination with copper (II) oxide, they are optimal for causing an oxidation reaction with oxygen generated by the decomposition of copper (II) oxide. Is. Further, these thin films are also materials that can be produced by a method with mass productivity such as sputtering or vapor deposition.

As the oxidizing agent, in addition to the above copper (II) oxide, an oxide such as manganese, antimony, germanium, arsenic or iron which releases oxygen at a relatively low temperature can be used. The decomposition temperatures of typical oxides are shown below. The values in the table are the standard enthalpy of formation ΔH ° and standard entropy ΔS ° of each oxide (298.15).
° K), assuming that ΔH ° does not depend on temperature, ΔH
It was determined as ° / ΔS °.

[0015]

[Table 1] Decomposition reaction Decomposition temperature (° C) 6 Mn ₂ O ₃ → 4 Mn ₃ O ₄ + O ₂ 875 2 GeO ₂ → 2 GeO + O ₂ 898 As ₂ O ₅ → 1/2 As ₄ O ₆ + O ₂ 908 Sb ₂ O ₅ → 1/2 Sb ₄ O ₆ + O ₂ 916 4 CuO → 2 Cu ₂ O + O ₂ 1005 2 V ₂ O ₅ → 2 V ₂ O ₄ + O ₂ 1267 6 Fe ₂ O ₃ → 4 Fe ₃ O ₄ + O ₂ 1338

Further, as the oxide to be used, besides titanium and zirconium, an element having a large standard heat of formation of an oxide such as aluminum, magnesium, lithium, strontium, and a rare earth element, that is, an element having a large calorific value during combustion is used. be able to. The standard heats of formation of typical oxidants are shown below.

[0017]

TABLE 2 oxide standard heat of oxygen per 1mol (kJ / mol at 298.15 ° K) 2TiO -1038 ZrO 2 -1101 2 / 3Al 2 O 3 -1116 2SrO -1184 2Li 2 O -1196 2MgO -1203 2 / 3Sm ₂ O ₃ -1215

The ignition layer formed by laminating the above-mentioned thin films of the oxidizer and the oxidant may be such that at least one layer is in a laminated state, but the amount of oxygen required for ignition is supplied and the contact area with oxygen is provided. It is preferable that the oxidant thin film be sandwiched between the oxidant thin films in order to maximize the temperature. In order to secure the operational stability of the ignition layer, it is preferable to block the contact with the outside air by a protective film.

[0019]

EXAMPLE 1 FIG. 1 shows a thin film ignition element 11 according to the present invention.
The top view of the 1st example of and the AA line sectional view are shown. Wide conductive parts 31 on both sides of the ceramic substrate 20
a and 30a are heat generating portions 31b forming a narrow passage in the central portion,
The oxidant thin film layer 31 and the oxidant thin film layer 30 are laminated in this order by patterning connected by 30b. When electricity is applied from both sides of the oxidant thin film layer 30, Joule heat is concentrated in the central portion. It is shaped so as to occur. Another oxidant thin film layer 32 is laminated on the heat generating portion 30b so as to cover it, and a protective film 40 is laminated on the outermost layer.

The oxidizer thin film layers 31 and 32 are each formed by reactive sputtering in which oxygen is introduced using copper as a target, and each of them is a copper oxide thin film (II) having a thickness of about 1 μm.
Was used. As the oxidant thin film layer 30, a titanium thin film having a thickness of about 500 nm formed by vapor deposition was used. Alumina is used for the ceramic substrate 20, and the protective film 40 has a thickness of about 5
A silicon oxide thin film of 00 nm was used.

As a result, the heat generating portion is provided at the center of the substrate,
Using titanium as an oxidant and copper (II) oxide as an oxidant, a firing element having a laminated structure in which a heat generating portion of the oxidant thin film is sandwiched between the oxidant thin films was obtained. A large spark was obtained even in an inert gas by energizing the oxidant thin film layer 30 of this element with a DC power supply.

[0022]

[Embodiment 2] FIG. 2 shows a second embodiment of the thin film ignition element. In the thin film ignition element 12, the wide current-carrying parts 21a, 21a on both sides are connected by the heat generating part 21b forming a narrow passage in the central part so that Joule heat is concentratedly generated in the central part on the ceramic substrate 20. The patterned resistor thin film layer 21 is provided, and the heat generating portion 21 is provided through the insulating film 22.
The oxidant thin film layer 31, the oxidant thin film layer 30, and the oxidant thin film layer 32 are laminated in this order on the surface b, and the protective film 40 is provided on the outer layer.
Are stacked.

Nickel formed by vapor deposition was used for the resistor thin film layer 21, and a silicon oxide film having a thickness of about 500 nm was used for the insulating film 22. The oxidant thin film layers 31 and 32 and the oxidant thin film layer 30 were formed by using the same material and method as in Example 1. The ceramic substrate 20 and the outer protective film 40 are also
This is the same as in the first embodiment. As a result, a nickel thin film heating layer is formed, and titanium is used as an oxidant and copper (II) oxide is used as the oxidant, and the oxidant is sandwiched between the oxidants to form a laminated thin film structure. An ignition element was obtained.

[0024]

Examples 3 and 4 In Examples 1 and 2, zirconium was used in place of titanium, and the thickness was about 500 by vapor deposition.
A thin film ignition element was manufactured using the same material and method except that a zirconium thin film of nm was formed.

[0025]

[Comparative Example] For comparison, a conventional thin film ignition element 13 using a nickel thin film was also manufactured. FIG. 3 shows this prior art thin film firing element. On the ceramic substrate 20, a resistor thin film layer 21 and a protective film layer 40, which are patterned so that Joule heat is concentratedly generated in the central portion, are laminated.

The firing element 12 having the laminated structure manufactured in Example 2 and the conventional firing element 13 manufactured in the comparative example.
The size of the spark generated when the same electric power was applied to the resistor thin film layer 21 of No. 2 in an inert gas by using a DC power source was photographed from the side of the ignition element. The results are shown graphically in Figures 4A and 4B. In the conventional element, the resistor thin film caused current breakdown, but almost no sparks were observed, and in the ignition element having a laminated structure, a large spark of 8 mm or more from the substrate was observed.

FIG. 5 shows a circuit for measuring the amount of light emission and the response time when these elements are fired. A pulse voltage V0 is applied to the firing element 10, and the change in resistance value at that time is monitored by the voltage generated in R2. The light generated by the ignition element 10 is transmitted to the phototransistor 50 which is arranged in close proximity.
And is amplified by the operational amplifier 51. The voltage generated in R2 and the output of the operational amplifier 51 are connected to the digital oscilloscope 52, and the output of the operational amplifier 51 was read by using the voltage generated in R2 as a trigger.

FIG. 6 shows a digital oscilloscope 52 when a thin film of a resistor is subjected to current destruction by applying a rectangular wave V0 of -8 V having a rise time of 5 μs to each of the resistor thin films having a resistance value of about 2Ω. It shows the output result of. In the ignition element 12 having a laminated structure, a much larger amount of light emission was observed than in the conventional ignition element 13 even in an inert gas, and the effect of the oxidant thin film was confirmed. Also,
Despite the fact that several thin film layers were laminated on the nickel resistor and the total heat capacity of the heat generating portion was large, the response time was almost as fast as the response time in the current breakdown of the nickel resistor.

FIG. 7 shows the results of measuring the surface temperature of the firing element 12 having a laminated structure and the firing element 13 of the prior art with an infrared radiation thermometer by energizing under the condition that the resistor thin film layer is destroyed by current. It can be seen that the surface temperature of the sample to which the laminated thin film is added reaches a high temperature and the surface temperature is kept high for a long time even under the same energization condition.

[0030]

As is apparent from the above description, according to the present invention, there is provided an ignition element having a laminated thin film structure of an oxidant and an oxidant, and the safety and operation stability of the ignition element are increased. Can be improved. This enables more rapid ignition without impairing the high-speed response and mass productivity of the ignition element that uses a thin film resistor.For example, when used as an ignition element for an automobile airbag system, the certainty of the ignition is increased. By eliminating the need for dangerous explosives such as explosives, it can contribute to ensuring safety.

[Brief description of drawings]

1 (A) is a plan view and FIG. 1 (B) is a schematic cross-sectional view taken along the line AA, showing a first embodiment of an ignition element according to the present invention.

2 (A) is a plan view and FIG. 2 (B) is a schematic cross-sectional view taken along the line AA, showing a second embodiment of an ignition element according to the present invention.

3 (A) is a plan view and FIG. 3 (B) is a schematic cross-sectional view taken along line AA showing an example of a conventional thin film ignition element.

FIG. 4 is a copy diagram of an example of a result of photographic observation of the size of sparks at the time of ignition of (A) the firing element according to the present invention and (B) the firing element of the related art.

FIG. 5 is a circuit for measuring the amount of light emitted during ignition.

FIG. 6 is a diagram showing an example of the amount of light emitted when the firing element of FIGS. 2 and 3 fires.

FIG. 7 is a diagram showing an example of a surface temperature at the time of ignition of the same ignition element as in FIG.

[Explanation of symbols] 10-13 ... Ignition element 20 ... Ceramics substrate 21 ... Resistor thin film layer 22 ... Insulating film 30 ... Oxidizing agent thin film layer 31-32 ... Oxidizing agent thin film layer 40 ... Protective film 50 ... Phototransistor PT501A 51 ... Operational amplifier LF356H 52 ... Digital oscilloscope HP54202A V0 ... Applied voltage -8V V1 ... Bias voltage -2.5V R0 ... Resistor 1kΩ R1 ... Resistor 9.1kΩ R2: resistor 3.5Ω

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) B60R 21/26 F42B 3/12 F23Q 3/00

Claims (5)

(57) [Claims] 1. A resistor thin film layer, which is patterned on an electrically insulating substrate so that a pair of wide current-carrying parts on both sides are connected to each other by a narrow heating part, and an ignition which is ignited by heat from the heating part. A thin film ignition element having a layer, wherein the ignition layer is rapidly oxidized by oxygen at a heat generation temperature of the heat generating portion, and a standard heat of formation per 1 mol of oxygen of the generated oxide is 1000 kJ / mol or more in absolute value. And at least one oxidant layer that decomposes at the exothermic temperature to generate oxygen, and at least one oxidant layer and at least one oxidant. A thin film ignition element in which an agent layer is laminated. 2. The thin film ignition element according to claim 1, wherein the resistor thin film layer comprises the oxidant. 3. The thin film ignition element according to claim 1, wherein the oxidant thin film layer and the oxidizable thin film layer are laminated in this order on the resistor thin film layer. 4. The ignition layer has a second oxidant layer,
4. The thin film ignition element according to claim 1, wherein the oxidant layer is sandwiched by two oxidant layers. 5. The thin film ignition element according to claim 1, wherein the oxidant is copper (II) oxide, and the oxidant is titanium or zirconium.