Electrical ignition and method for its production.

The invention relates to the object described above.

From DE-PS 20 20 016 an ignition set including an electrical ignition means is known, which consists of an electrically conductive housing and an insulated therein arranged and accessible from the outside pole piece, which pole piece is electrically conductively connected to the housing via an ignition bridge. Inside the housing there is an insulating body made of glass or ceramic with metal layer contacts which are in contact with the primer and are partially covered with a firing bridge made of tantalum or tantalum nitride. One of the metal layer contacts, which can consist of nickel, palladium as well as palladium-silver, palladium-gold, platinum-silver, platinum-gold and silver-aluminum alloys, stands with the pole piece via a bore lined with conductive material in the insulating body in an electrically conductive connection, while the ground connection to the outer housing is formed with a support ring which presses the insulating body containing the metal layer contacts against the pole piece. However, these so-called single-pole electrical ignition devices can only be produced in a comparatively complex process, since the ignition bridge must be contacted with many parts of the ignition device.

It is indeed also known to use so-called two-pole glass leadthroughs, in which the complex contact known from the single-pole electrical ignition means is avoided in that the two current-carrying leads, also called "pins", are insulated in the glass body. However, since between these pins the conductive layer forming the ignition bridge in turn has to be produced in a very complex manner, by first producing this layer by means of sputtering or vapor deposition in a high vacuum and then reworking, for example etching, or by producing the conductive layer in the mask technology, which is also labor-intensive, this known method also leaves many wishes unanswered regarding a simplified production process for ignition and ignition means, especially since the glow wires which are conventionally attached between the pins have not proven themselves as ignition bridges, since they can only withstand severe mechanical loads to a limited extent.

The object of the invention is to make available an electrical ignition bridge carrier which does not have the disadvantages of the previously known constructions and which is mechanically highly resilient. At the same time, a process is to be developed for the production of this ignition bridge carrier, which can be carried out comparatively easily without complex post-processing, but with great certainty with regard to the process products and their properties.

The solution to this problem is an electrical ignition bridge carrier for the ignition of ignition sets, delay sets and pyrotechnic mixtures as well as for the ignition of primary primers and sets, which is characterized in that it consists of a ceramic body 2 with one or more bores inserted into a metallic outer ring 1, into the solid or tubular contact pins 3 as current supply lines, tightly and tightly fitted and surrounded by a conductive layer 4, between which the ignition bridge 5 is located.

Stainless steel, which can also be used as a material for the contact pins 3, has proven particularly useful as the material for the metallic outer ring 1. However, it is also possible to use other metallic materials for the metallic outer ring 1 and / or the contact pins 3, for example aluminum, copper, nickel and their alloys, titanium, zirconium, tantalum and other heat-resistant and high-melting metals and alloys, in particular also the known as KOVAR cobalt-nickel-iron alloy.

A wide variety of ceramic materials can be used as materials for the ceramic body 2, in particular those based on aluminum oxide, silicon dioxide, silicon nitride, silicon carbide and zirconium dioxide.

The tight and firm connection or fitting between the metallic outer ring 1 and the ceramic body 2 on the one hand and between the ceramic body 2 and the contact pins 3 on the other hand can be done by gluing using adhesives known to the person skilled in the art, but also by cementing, but preferably by Glazed in. The materials known to any person skilled in the art, with which metallic materials and ceramic materials are tightly connected, can be used for the preferred glazing. In this context, alkali and alkaline earth silicate glasses, glasses based on borosilicate and glasses containing oxides of rare earth have proven particularly useful. A glass of the following composition can be used as an example of a glass which is suitable for this glazing connection between metallic and ceramic material:<tables id="tabl0001" num="0001"><img file="EP0248977A1_D0001.tif" /></tables>

However, it is also possible to use ceramic pastes, for example the pastes shown below in their composition:<tables id="tabl0002" num="0002"><img file="EP0248977A1_D0002.tif" /></tables>

Silicon or silicon alloys mixed with quartz powder, glass powder and clay can also be used to permanently bond the ceramic with the metallic materials.

The conductive layer 4 applied in the form of a surface around the contact pins 3 is generally a thin or thick film layer applied in a customary manner, which has been produced, for example, by screen printing or galvanically. The noble metals and noble metal alloys of group VIII of the periodic table, in particular platinum or palladium and their alloys also with silver and / or gold, have proven themselves as materials for this conductive layer 4.

The actual ignition bridge 5 between the contact pins 3 or the conductive layers 4 enclosing them in the form of a surface can either be formed by a wire, as can be seen, for example, from FIG. 4, which will be explained in detail later. However, it has been shown that the application of the ignition bridge 5 also has special advantages in screen printing technology; resistance ranges from 1 to 100 ohms can be achieved in this way. However, it is also possible to apply the ignition bridge as a thin film in an atomization process known per se or by vapor deposition in a vacuum. The wire-shaped ignition bridges are either soldered or welded on.

Precious metal materials, as already mentioned above, have also proven particularly useful as materials for these ignition bridges. These resistance bridges, which are specially applied using screen printing technology, have an already sharply defined resistance range after heat treatment, but if desired, it is possible to achieve resistance values ​​of even smaller fluctuation ranges by post-processing in the laser trimming method known to the person skilled in the art.

It is particularly advantageous when using screen printing technology to produce the ignition bridge that the ceramic body does not require any special pretreatment, but rather can be used directly with the roughness depth of N 5, for example, which occurs in production. In addition, screen printing technology is an easy-to-use process that also provides ignition bridges that are far more economical than mechanical wire bridges in terms of their mechanical resilience.

The invention is explained below with reference to the drawings.<ul id="ul0001" list-style="none"><li>1 shows in section the metallic outer ring 1 with the fitted ceramic body 2 in the form of a ceramic blank with here, for example, two contact pins 3. The ceramic body 2 is tightly connected to the metallic outer ring 1 on the one hand and the contact pins 3 on the other hand, either using the brazing process, with a ceramic cement or an organic adhesive or by glazing technology using the glasses or pastes specified above, for example in their composition.</li><li>FIG. 2 shows a simplified top view of the ignition bridge carrier of FIG. 1, with only the contact pins 3 with the conductive layers 4 surrounding them in the form of a surface and the ignition bridge 5, which here, like the conductive layers 4, have been applied using the screen printing process, for better clarity, are shown.</li><li>FIGS. 3 and 4 show a variant of the ignition bridge carrier shown in FIGS. 1 and 2 according to the invention, in which the ignition bridge is formed by a wire 5a which establishes the conductive connection between the contact pins 3.</li></ul>

It is of course possible to use a larger number of contact pins in the ceramic body, in which case the corresponding larger number of ignition bridges must of course also be applied.

The method for producing the electrical ignition bridge carrier according to the invention is essentially characterized in that a ceramic body having one or more bores is fitted into a metallic, geometrically shaped outer ring and is tightly connected to the metallic outer ring, whereupon the metallic contact pins are fitted into the bores of the ceramic body and are also tightly connected to the ceramic body and then either wire-shaped ignition bridges between the contact pins are produced by soldering or welding, or preferably ignition bridges are produced by sputtering or vapor deposition technology in a vacuum or screen printing process. In this last-mentioned method, an electrically conductive layer is preferably first applied in the form of a surface around the contact pins, via which the connection between the contact pins and the ignition bridge is established.

The ignition bridge carrier with the ceramic elements according to the invention is distinguished from the previously known embodiments in that, owing to the higher compressive strength of the ceramic materials, a far higher mechanical load-bearing capacity can be achieved than was possible with a glass bushing. In addition, the ceramic materials have a higher thermal conductivity than normal glasses, which has proven extremely favorable, for example, in the first-time production of 1A / 1W ignition elements. In addition, the ceramic bushings enable the production of welded ceramic-based ignition elements which, in addition to their mechanical resilience, have the further advantage that they are completely sealed.