MXPA01008410A - Solderless ceramic igniter having a leadframe attachment - Google Patents

Abstract

An electrical connection for a ceramic hot surface element in which the ends of the hot surface element are essentially interference fit within a pair of metallic termination sleeves, and electrical connection to the hot surface element is provided by an active metal braze which is directly chemically bonded to the metallic termination.

Description

1GNITOR CERAMIC WITHOUT SOFT WELDING WHICH HAS A DRIVER FRAME SUPPORT DESCRIPTIVE MEMORY Ceramic materials have enjoyed great success as ignitors in furnaces, stoves and clothes dryers heated with gas. A ceramic igniter typically includes a hot-surface ceramic element that is fork-shaped or U-shaped and that contains two conductive end portions and a highly resistive central portion. When the element ends are connected to conductive cables, the highly resistive central portion (or "hot zone") increases in temperature. Since these igniters are resistively heated, each end thereof must be electrically connected to a conducting wire, typically a copper conductor wire. However, the problems associated with the connection of the hot-surface ceramic element ends with conducting wires are well known. A common problem is that the ceramic material and the conductive wire do not connect well with each other. EP 0486009 ("Miller") discloses and figure 2 of the present shows a conventional ignitor system in which it is applied by brushing a hard solder 91 to one end of the ceramic material 92, then the hard solder is heated under vacuum, the soft solder 93 is applied to the hard solder and the conductive wire 95 is adhered to the solder. This soft solder is typically applied, carefully directing a flame at high temperature (1600-1800 ° C) on the end of the hard-welded ceramic branch, contacting the soft solder to the hot branch (thus causing the solder to flow) and then placing the conductive wire in the solder still liquid. However, the use of solder as described above often causes a multitude of problems for this technology. In the first place, this method is a very sensitive and time-consuming operation. Second, exposing the element to the high temperature flame often causes a crack in the igniter. The gap may be due to a disproportionate coefficient of thermal expansion ("CTE") between the hot surface ceramic element ("CHSE") and either the soft solder or the hard solder. It may also be due to the thermal shock of the CHSE. Third, even if the soft weld is satisfactory, the resulting weld covering is typically only on one side of the branch (as shown in Figure 2). If excessive pressure is applied to the tip of the wire (which frequently occurs in the cementing operation), the conductor wire can be pulled freely from its ligature. Fourth, it is known that, in use, soft solder is susceptible to oxidation and is very often the cause of premature aging of the igniter. Some researchers have tried to handle the problems caused by soldering. For example, the patent of E.U.A. Do not. ,564,618 ("Axelson") recognized that the disproportion of CTE between hard solder and solder was causing break during the soft solder step and sought to minimize hard solder using a silk screen procedure. Although this method eliminated some cracks during the soft welding step, the other three problems described above have persisted. In addition, the small amount of hard solder needed by the Axelson method ensured a substantially weaker bond between the hard solder, the soft solder and the wire, leading to substantial failures during the peel test. In another attempt to solve this problem of disproportionation of CTE, the branches of the hot-surface ceramic element are immersed in a hard solder deposit and then heated under vacuum to cure the hard solder. Ideally, this method should provide a complete and uniform coating of the branch at 360 degrees, so that the curing of the hard welding puts the branch in convenient compression. However, since the submersion procedure is inaccurate, there is typically a large variation of both the coating thickness and the coating area, resulting in an inconvenient stress distribution. In addition, the three other problems caused by the use of solder still persist. Finally, this procedure uses a large amount of very expensive hard solder.

Some researchers have tried to eliminate soft solder from ceramic igniter termination systems. For example, GB 2,095,959 discloses a ceramic block that provides mechanical stability to the hot surface wire and element system. Nichrome wires are physically placed in slotted holes machined in the hot surface element and the wires are mechanically held in place with a metal overlay that can either be flame sprayed, galvanized (ie electrodeposited) or frit (glass) or Nichrome or silver coated. Terminals are attached to the conductor wires and insulation handles are attached to the conductor wires. An element in the block accepts the isolation handles on the wires. The modalized mechanical support redundancy in the complete ceramic block / extensive groove / grab system of GB'959 indicates that this inventor is very concerned that the conductor wires will break freely from the hot surface element and cause the system to fail. The patent of E.U.A. No. ("Salzer") teaches about a modular ceramic ignitor system, in which the hot-surface ceramic element is plugged into a receptacle that has a conductive contact therein. In some embodiments these receptacles have spring-shaped contacts that help hold the branch of the ceramic igniter in place. In others, the receptacles are tube-shaped. However, each of these systems are plug systems which are designed to be temporary and therefore easily dismantled.

In summary, the use of soft solder in the ceramic ignitor systems caused a multitude of procedural and performance problems. Attempts to design systems that eliminate soft solder have resulted in either fragile or temporary systems. Therefore, there is a need for a ceramic ignitor system having a permanent electrical connection without soft solder for hot surface ceramic elements. The present inventors have observed that the use of a metallic conductor frame to permanently electrically connect a CHSE branch coated with hard solder of active metal to the conductive wire allowed to the inventors to eliminate the solder of the already provided system thus both advantages of process as significant performance advantages with respect to the ceramic igniter terminations of the prior art. With regard to procedural advantages, both the steps of I) connect the conductor frame to the hard solder and II) connect the conductor frame to the conductor wire can be more or less solid procedures. This allows the assembly to adapt to automation. As indicated above, the conventional method of assembly involved in the use of solder and was thus highly sensitive to many factors that required human surveillance. With respect to the characteristics of the product, it was observed that the present invention possesses a multitude of advantages over the conventional ignitor that required a solder interface between the hard solder and the conductive wire. First, the slits induced by the disproportionation of CTE produced during the soft welding step had been eliminated, thus producing a stronger igniter. Second, the increases in electrical resistivity in use have been substantially decreased, resulting in an effective duration of ignitor that is more than about twice that of the conventional ignitor containing solder. Third, resistance to detachment of the igniter is enhanced, compared to the screen sizing procedure, because no slit induced by the soft solder is present. Finally, the removal of solder allows igniter to be used in high temperature environments at more than about 450 ° C (such as stove tops and self-cleaning ovens) that would compromise soft solder. further, the particular geometry provided by the conductor frame provides special advantages over the other metal termination designs. First, referring now to Figure 1, the conductor frame 5 can include a sleeve 56 to which the branch 1 of the CHSE 3 can be easily inserted. This allows not only an exact and repeatable assembly, the resulting product not heated It is quite durable and can withstand the handling of silk during production. Secondly, the conductor frame can include a ring forming a hole 9 in the ceiling 55 that not only allows the hard solder to be applied after the insertion of the branch to the conductor frame (thus placing exactly the hard solder pad if the subsequent uncontrolled dipping), it also serves as a guide both to precisely control the placement of the hard solder in the center of the ceramic branch (and therefore away from the edges that are prone to more machining effects) and to control the amount of coverage of the hard solder surface. Third, the conductor frame can include a V-shaped flap 13 on its rear end to which the end 11 of a conductive wire can be connected, thus allowing each conductive wire to be collinear with its respective surface element branch. hot that has to be placed (resulting in a stronger assembly that will not be subject to efforts associated with the installation of the ignilor for final assembly). Therefore, according to the present invention, an electrical connection for a hot-surface ceramic element is provided, comprising: a) an electroconductive ceramic material having a first end, b) an electroconductive hard solder of active metal which makes contact by at least a portion of the first end, and c) a metal termination that contacts the hard solder of active metal, in which the metal termination is chemically bonded to the hard solder of active metal.

In preferred embodiments, the connection is for a hot surface ceramic element, and comprises: a) an electroconductive ceramic material having first and second ends; b) a first electroconductive active metal solder pad that contacts at least a portion of the first end, c) a second electroconductive active metal solder pad that contacts at least a portion of the second end, d ) a first metal termination making contact with the first hard solder pad of active metal, and e) a second metal termination contacting the second hard solder pad of active metal, in which each metal determination is chemically bonded to its corresponding hard solder of active metal. Also in accordance with the present invention, a ceramic igniter is provided comprising: a) an electrically conductive ceramic material comprising two cold ends and a resistive zone therebetween; b) a pair of terminations, each termination comprising a sleeve having a first end and a second end, wherein each end of electroconductive ceramic material is permanently received at the first end of its respective sleeve and is in electrical connection therewith, wherein each determination is a metallic termination, the igniter further comprising a pair of metal pad, each metal pad making contact with its respective ceramic end and its respective metal termination to provide electrical connection between the ceramic end and the metal termination, and wherein each sleeve has a ring defining a transverse hole, and in which each dental pad remains substantially in its respective hole and makes contact with the end of ceramic material received in its sleeve, and in which each ring makes contact with its respective end ceramic. Also in accordance with the present invention, a method for making a ceramic igniter termination is provided, comprising the steps of: a) providing a ceramic igniter having first and second ends, each end having an outer surface, b) providing a pair of sleeves, each sleeve having an inner surface corresponding substantially to the outer surface of the first and second ends, c) inserting the first and second ends of the ceramic ignitor to the pair of sleeves, d) chemically bonding the inner surface of the sleeve to the external surface of the branch received in it.

Figure 1 is a drawing of a respective view of a non-assembled connection of the present invention. Figure 2 is a drawing of a ceramic ignitor connection system of the prior art using soft solder. Figure 3 is a flow chart describing a preferred automated system for realizing the present invention. Figure 4 is a drawing of an axial cross section of the assembly. Figure 5 is a perspective view of the entire assembly of Figure 4. Figure 6 is a perspective view of one embodiment of the present invention. Figure 7 is a drawing of a single depression mode of the present invention. Figure 8 is a drawing of a double depression embodiment of the present invention. Figure 9 is a drawing of a single point contact mode of the present invention. Figure 10 is a drawing of one embodiment of the present invention in which the hard welding hole and the fastener are on opposite sides of the wire frame sleeve. Referring now to Figure 1, in a preferred method of making the igniter, a hot-surface ceramic element (CHSE) 3 having two essentially parallel ends (or "branches") 1 connected by a bridge is used. These branches slide to the first end 88 of the corresponding sleeves 56 of the conductor frame 5. Next, the hard solder (not shown) is first deposited in the hole 9 in the conductor frame sleeve and then heated under vacuum to create ceramic hard solder and hard solder joints of the conductor frame. Finally, one end 11 of a conductive wire is placed on the V-shaped beater fin 13 and mechanically curled in place. In an especially preferred automated system for making the ignitor of the present invention, a predetermined number of ceramic igniters are fed with a precision linear rail into the bowl and inserted into the sleeves of the corresponding plurality of conductor frames attached to each other on a reel stamping of drivers' chassis. See figure 3. This combination then moves the hard solder dispensing station, whereupon the hard solder is deposited in the ceiling holes of the conductor beaters. This assembly is then presented to a high-temperature vacuum furnace which reflows the hard solder and creates both hard solder bonds of ceramic and hard solder of the conductor frame. Next, the assembly is presented to a singulation station in which the metal junctions between the conductor frames are recessed on the reel, to produce a plurality of independent igniters. Finally, the conductor wire is placed on the conductor frame fin and welded with resistance to the fin. Referring now to the preferred embodiments set forth in Figures 1, 4 and 5, each branch 1 of hot-surface ceramic element 3 is permanently held in place within the sleeve 56 of the conductor frame 5 by the hard solder 7 remaining inside. of the hole 9 of the conductor frame ceiling 55. A first end of the conductive wire 11 is electrically connected to the upper surface of the fin portion 13 of the conductor frame 15 and is thus a means for providing electric current to the surface element hot 3. The conductor frame 5 has a flat base 51 having an upper surface 81 having a fin 13 at one end. The conductor frame also has a side wall 53 and a lip 54 that rise parallel to each other from the flat base 51. The ceiling 55 is connected to the flat base 51 by the side wall 53. In Figure 1, the base 51, the side wall 53, the lip 54 and the roof 55 form a sleeve 56 whose axial cross section substantially corresponds to the branch axial cross section 1 of the CHSE. The depression 61 of FIG. 1 extending downwardly from the ceiling 55 provides a means for making an interference fit with the branch of the igniter, when the branch is inserted in the sleeve 56 in the direction A. In FIG. 4, the base 51, the side wall 53, the lip 54 and the roof 55 form a sleeve 56 and the interference fit are formed by selecting the height 84 of the side wall 53 to be slightly smaller than the thickness 85 of the branch 1 of the CHSE 3. It is believed that the present invention can be profitably applied to make an abutment for any conventional hot-surface ceramic element. However, since this method can be easily adapted to automation when the CHSE has two essentially parallel branches, the method has a particular advantage when CHSE having parallel branches is applied. In some cases, the CHSE is a ceramic igniter of recrystallized SIC, such as that set forth in the U.S. patent. No. 3,875,477 ("Fredrikson"), the descriptive memory of which is incorporated by reference. In these SIC CHSE, the cold conductive ends and the resistive zone are made of the same SIC material. In other embodiments, the CHSE is a fully dense ceramic igniter comprising either AIN / SIC / MoSi2 or S3N4 / SIC / MoS2, such as that set forth in the US patent. No. 5, 045,237 ("Washbum"), the descriptive memory of which is incorporated by reference. In the Washbum embodiments, the hot surface ceramic element comprises a pair of conductive (or "cold") ends 71 and 72 and a resistive hot zone 73 therebetween, as shown in Fig. 6. In preferred embodiments, the hot zone comprises: a) between about 50 and about 75% by volume of an electrically insulating material selected from the group consisting of aluminum nitride, boron nitride, silicon nitride and mixtures thereof, b) between about 10 and about 45% by volume of a semiconductor material selected from the group consisting of silicon carbide and boron carbide, and mixtures thereof, and c) between about 5 and about 25% by volume of a metal conductor selected from the group consisting of disilicide of molybdenum, tungsten disilicide, tungsten carbide, titanium nitride and mixtures thereof. In the most preferred embodiments involving AIN, the hot zone comprises a first resistive material comprising between 50% by volume and 75% by volume of AIN, between 13% by volume and 41.5% by volume of SIC, and between 8.5% by volume. volume and 12% in volume of MoSi2. In more preferred embodiments involving Si3N4, the hot zone comprises a first resistive material comprising between 50% by volume and 75% by volume of SÍ3N4, between 15% by volume and 45% by volume of SIC; and between 10% in volume and 25% in volume of MoSi2. In other embodiments, the hot zone further comprises between 1 v / o and 10 v / o of alumina, preferably in accordance with the patent of E.U.A. No. 5,514,630, the specification of which is incorporated by reference herein. The conductive cold ends 71 and 72 provide means for electrically connecting the CHSE to the conductor frame and the conductor wires. Preferably, they are also composed of AIN, SIC and MoSi2, but have a significantly higher percentage of conductive and semiconducting materials (ie SIC and MoSi2) than preferred compositions for hot zone. Consequently, they typically have much less resistivity than the hot zone and are not heated to the temperatures experienced by the hot zone. It preferably comprises. a) from 20 to 65 v / o of a ceramic material selected from the group consisting of aluminum nitride, silicon nitride and boron nitride and mixtures thereof, and b) from about 35 to 80 v / o of MoSi2 and SIC in a volume ratio of approximately 1: 1 approximately 1: 3. More preferably, the conductive ends comprise approximately 60 v / o of AIN, 20 v / o of SIC and 20 v / o of MoSi2. In preferred embodiments, the dimensions of conductor ends 9 and 13 are 0.05 cm (width) x 4.2 cm (depth) x 0.1 cm (thickness). Typically, the cold conductive ends have a resistivity at room temperature of no more than 1 ohm-cm, preferably no more than 0.1 ohm-cm. In the embodiment of the present invention, the present inventors considered electrically connecting the hot surface element 3 to the conductor frame 56 in a number of different ways. One method involved the refractory metal reaction ligation, in which the strand of a recrystallized porous SIC CHSE was cored, a tungsten strip was placed in the nick, and the conductive wire was welded directly to the tungsten. However, it was observed that the resulting product experienced severe oxidation. A second method involved using a hard solder of active metal to connect a fastener (made either of stainless steel, a Be / Cu alloy or a Ni / Fe alloy) to a porous recrystallized SIC igniter branch. However, it was observed that the resistance to release of the resulting igniters was extremely low. Accordingly, the present inventors learned that having simply been a soft solder wire conductor attachment to a CHSE is not a trivial practice, even when using a hard solder of active metal. The hard metal solder must not only be electrically conductive, it must also be compatible with both the CHSE and the conductor frame. That is, it must be able to bond with the ceramic material and the conductor frame to provide both mechanical integrity and electrical conduction and must have a CTE that is compatible with each one as well. However, since both the conductor frame and the hard solder are typically metals, the suitability of the hard solder is determined by the suitability of the bond between the hard solder and the ceramic material. Generally, the hard solder composition is any conventional hard solder composition that forms an electrical connection with the CHSE branches. In some preferred embodiments, the hard solder must have a CTE that is within approximately 25% of the CTE of the ceramic material.

In order to obtain a preferred high degree of adhesion to the ceramic material required, the hard solder typically contains an active metal that can wet and react with the ceramic materials and thereby provide chemically released adhesion thereto with filler metals contained in the hard solder. Without wishing to be bound by theory, it is believed that hard solder of active metal chemically reacts with metals in the metal conductor frame also produces a chemical bond between them. Preferred hard metal solders are exposed in the U.S. patent. No. 5,564,618, the specification of which is incorporated by reference herein. Examples of specific active metals include titanium, zirconium, niobium, nickel, palladium and gold. Preferably, the active metal is titanium or zirconium, more preferably titanium. In addition to the active metal, hard solder also contains one or more filler metals such as silver, copper, indium, tin, zinc, lead, cadmium and phosphorus. Preferably, a mixture of filler metals is used. Most preferably, the hard solder will contain titanium as the active metal and a mixture of silver and copper as filler metals. Generally, hard solder will contain between about 0.1 and 5% by weight of active metal and between 95 and 99.9% by weight of filler metals. Some suitable hard solders are commercially available under the Lucanex factory name of LucasMilhaupt, Inc. of Cudahy, and Cusil and Cusin of Wesco, Inc. of Belmont, Cal. In preferred embodiments, the hard solder is Wesgo Cusin-1-ABA, obtainable from Wesgo, Inc. of Belmont, CA. Specific hard solders that are considered particularly useful in the present invention include Lucanex 721 and Cusil Braze, each of which contains about 70.5 wt% silver, about 27.5 wt% copper and about 2 wt% titanium. In the reflow of the hard solder after it has been deposited on the CHSE surface, care must be taken to properly control the hard weld profile in time and temperature. An incorrect profile can cause the hard solder to flow inappropriately, thus causing electrical failure in the ignitor. In some embodiments, the solder is reflowed between about 805 ° C and 850 ° C and at a soaking time between about 0 minutes and 10-30 minutes (depending on the time necessary for the thermal mass to reach the steady state) of a vacuum of no more than about 10"6 torr and cooled at a rate between 2 ° C / minute and 20 ° C / minute Although slower cooling speeds are preferred, they are not especially critical. Soak time and temperatures at the lower ends of these ranges described above.Also, the amount of hard solder is important.If an insufficient amount of hard solder is used, then the mechanical and electrical integrity of the ligatures can be compromised. excessive hard solder is used, then there is a danger that the disproportion of CTE between hard solder and ceramic material will produce indentations in the area underlying the hard solder last I'll take the step of curing hard solder. The appropriate amount of hard solder can typically be determined by customary finite element analysis methods. Furthermore, it was observed that the centering of the weld lasts 7 between the parallel edges 82 and 83 of the branch (as shown in Figure 6) was also very important. If hard solder is applied near one edge of the branch, the resulting stresses are not evenly distributed and maximum acute stress values can be seen. In addition, the edges of the branch are often a more common source of machining defects than the more or less flat surfaces of the branch. Accordingly, in some preferred embodiments, the hard solder is centered between the parallel edges of the branch in order to reduce the possibility of rupture. In the application of hard welding, it was observed that the metallization process was prohibitively long when the density of the hot surface ceramic element was about 85%. In contrast, when the ignitor has essentially no open porosity (ie more than about 95% density), the duration of the metallization step was commercially acceptable. Accordingly, in some preferred method embodiments, the ceramic igniter has essentially no open porosity. Generally, the geometry of the termination can take on any conformation, such as a flat surface, a U-shape or a tube. In some preferred embodiments, the termination includes a sleeve shape. In some embodiments (as in Figure 4), the sleeve sidewall 53 may have a height 84 that is slightly less than the branch thickness 85, so that with the insertion of the branch, the sleeve tightly holds the branch in position. an adjustment in interference and thus provides advantages over a termination that is a simply flat surface. Alternatively, the sleeve may have depressions 61 (as in Figure 1) or fasteners 65 (as in Figure 10) that employ interference fittings to hold the branch in place. In a simple sleeve mode in which the sleeve is an annular tube that has no internal holes, the conductive wire attachment typically requires careful mechanical and time-consuming crimping of the conductor wire to the tube. In addition, in this mode, the unheated hard solder coating must first be applied to the branches of the ceramic ignitor before its insertion into the tube. During insertion, it is often smeared over the branch, often reaching problematic branch edges. In contrast, the conductor frame embodiment of the present invention, the fin portion of the conductor frame provides an easily accessible flat surface on which to make the electrical connection, thus eliminating the need for mechanical crimping. In addition, the orifice element of the conductor frame allows the controlled deposition of the hard solder after the branch slides into the sleeve, thus eliminating embedment. Therefore, in preferred embodiments, each sleeve has a transverse hole therethrough and the chemical ligation step is performed by the steps of: i) depositing a hard solder of active metal in the hole after the insertion of the branch, and ii) reflowing the hard solder. Finally, referring now to Figure 1, the depression 61 helps to secure each branch 1 within its sleeve 56. Therefore, in especially preferred embodiments, the termination is a conductor frame whose sleeve has a transverse hole, the roof of which it has a depression or a fastener extending therefrom and a fin portion extending from the second end of the sleeve. The conductor frame needs to be electrically conductive (in order to transport current from the conductive wire to the hard solder). However, it does not need to have high resistance to oxidation at high temperature and is typically made of metal. In some preferred embodiments, the metal termination of the conductor frame comprises an oxidation-resistant material selected from the group consisting of nickel-based compositions containing at least 85% nickel (preferably at least 95% nickel), Ni-Cr alloys, silver, gold and platinum. In some embodiments, it consists essentially of the oxidation-resistant material which will be susceptible to moisture at typical operating temperatures of between about 600 ° C and 800 ° C. This material should have a melting point of at least 485 ° C, preferably at least 600 ° C. It typically has a CTE that is compatible with that of hard solder. In one embodiment, the metal termination is made of Alloy 42, nickel-iron alloy obtainable from Heyco Metals Inc. of Reading, PA. In some embodiments, the conductor frame comprises an underlying substrate made of a relatively inexpensive metal (such as copper or a copper-based alloy) and an overlying coating of a material more resistant to oxidation, more expensive, such as those exposed previously. There is typically no concern for the compatibility of these metallic finishing materials and the hard solder of active metal. In some embodiments, the CHSE has a part inserted between its branches, as set forth in the U.S. patent. No. 5,786,565, the specification of which is incorporated by reference. In these embodiments containing this type of ignitor, it is especially preferred that the conductor frame sleeve consists essentially of three walls as in Figure 5 (ie it has essentially no lip which would interfere with the easy insertion of the igniter type. embodiments, the igniter of the present invention is used as a type of ignitor plug, such as those set forth in the Salzer patent discussed above In these embodiments, one end of a pin made of a high temperature metal having a melting point at least 600 ° C (such as Ni-Cr) to the fin as the conductive wire.The other end of the pin is then used as the male connector for a plug connection.Due to the critical role played by the Hard welding in the provision of both mechanical and electrical connection, it was initially believed that the provision of as much welding coverage as possible would produce an ignitor At the same time, it was noted that the simple depression design of Figure 7 necessarily limited the coverage of the hard solder 7 essentially to the area of the hole 9. Accordingly, the roof of the conductor frame was modified to contain two depressions of contact and a hole for hard welding between them. This modification is shown in FIG. 8. Since the hard solder hole 9 of FIG. 8 is now located between the two contact depressions 61, it rises from the surface of the igniter branch, thus allowing the solder to last. extend freely during reflux and maximizing its branch coverage. Therefore, in some embodiments, the ring defining the hard solder hole 9 does not contact the ceramic branch 1. In this case, the roof 55 of the conductor frame has two depressions 61 and a hard solder hole 9 located between them, thus raising the hole ring for hard welding from the branch and allowing limited extension of the hard weld during reflow. In addition, if the lip is removed (so that the sleeve has only a base, a side wall and a roof, the igniter branch can be oriented perpendicular to the side wall and inserted into the sleeve as well, thus producing an adjustment like shown in Figure 6. This mode of insertion has the particular advantage when the igniter branch has an irregular shape which makes insertion into the sleeve difficult parallel to the side wall, in this case, the parallel edges 82 and 83 of Each branch defines a central axis and the branch 1 is arranged in the sleeve 56 so that the central axis is perpendicular to the side wall 53. The conductor frame in this embodiment further has the wing 13 extending from the side wall 53, thus aligning the fin 13 with the center axis of the branch This branch is held in place by an interference fit in which the roof 55 also acts as a bidirectional fastener which is first tends from the branch 1 and the base 51, and then to the branch 1 and the base 51 to make contact with the branch 1. In contrast, in Figure 1 the parallel edges of each branch define a central axis and the branch 1 is arranged in the sleeve 56 so that the central axis is parallel to the side wall 53. Preferably, the igniter branch and the sleeve are dimensioned so that the branch is adjusted in interference when it is inserted into the sleeve. This interference is advantageous because it provides stability to the previously welded, hard assembly. The interference fit is preferably achieved by at least one of three means. In the first medium, interference is essentially achieved by an undersized sidewall. (As in figure 4). That is, the height 84 of the side wall is less than the thickness 85 of the branch, so that during the insertion of the branch 1 to the sleeve the branch makes contact with both the roof 35 and the base 51 (which are flexed to reach at a slight angle to each other) before it touches the side wall. In the second medium, the interference is provided by a depression 61, as in Figure 1. In this embodiment, the height of the sidewall 53 exceeds the thickness of the branch 1 and either the roof or the base has either a depression internal that extends from the face to the opposite branch to produce a free space between roof and base that is less than the thickness of the igniter. Therefore, when the ignitor branch is inserted into the sleeve, it contacts the depression and the opposite wall to produce interference fit. In the third medium, interference is provided by a unidirectional fastener, as in Figure 10. In this embodiment, the height of the side wall exceeds the thickness of the branch and either the roof or the base has either an external fastener 65. which extends from the face towards the opposite branch to produce a free space between roof and base that is less than the thickness of the igniter. Therefore, when the ignitor branch is inserted into the sleeve, it contacts the fastener and the opposite wall to produce interference fit. As a variation of the fastener embodiment, a bidirectional fastener having a first portion 86 extending from the opposite face and then a second portion 87 extending back toward the opposite face can be used, as in Figure 6. The above-discussed conductor frame of FIG. 8 has two distinguishing features. First, its roof has two depressions 61. When an appropriately sized ignitor slides to the conductor frame, the double-depression element produces an interference fit with the ignitor and keeps it in place. Secondly, the roof also has a hole 9 through which the hard solder 7 can be conveniently applied. Although these two elements provide significant benefits, the present igniters set out to improve this design and three initially identified areas of importance: mechanics produced by the interference fit used to secure the ceramic branch in the conductor frame; thermal stresses produced by hard welding activity; and stress efforts in the assembled part due to use in service. The present inventors then analyzed each of these three stress situations for the igniter substantially shown in Figure 8 with the aid of finite element analysis (FEA). With respect to the mechanical stresses produced by the interference fit, it was observed that the interference will induce harmless compressive mechanical stresses within the ceramic material over the actual contact area with the ceramic material, but will also induce some damaging strain stresses in the immediate area that surrounds the contact area. However, the actual magnitude of these stresses is not very significant. Therefore, the use of an interference fit itself will not automatically produce significant stresses in these conductor frame designs.

It has been observed that the efforts related to hard welding are the most important efforts of any aspect of these igniters that contain conductor frames. Simply, the steps of reflowing the solder lasts at about 850 ° C and subsequently allowing it to cool to room temperature produce significant thermal stresses on the hard solder print and stresses on its periphery. These efforts are in the order of approximately 200 MPA. It was observed that the forces induced by hard welding on the ceramic branch and on the interface between ceramic material and hard welding are less important. Therefore, the hard solder itself was identified as the element of the igniter most susceptible to rupture related to hard welding. The additional analysis led to the conclusion that the simple substitution of different ceramic materials or conductor frames would not lead to appreciable changes in the magnitude of the stresses that impact hard welding. Rather, the proper handling of these efforts could be realized only by changing the characteristics of the hard solder. In particular, it was found that the most important factors of these characteristics were. a) control of the surface area coverage of the hard solder, b) the type of hard solder, and c) the coefficient of thermal expansion of the hard solder.

Surprisingly, the finite element analysis of the double depression design determined that there is an advantageous exchange in the amount of hard solder that covers the surface of the branch. The degree of hard solder coverage impacts the electrical resistance of the ignitor, the efforts imparted to the ceramic ignitor and the solids of the hard solder to withstand the efforts of hard welding. Therefore, if there is very little coverage of the branch, the electrical connection is compromised and the hard solder is weak. Conversely, if there is too much pure welding, the efforts will damage the integrity of the ignitor. Therefore, there is a need to accurately control the hard solder used. In view of this need for precision placement of the hard solder, the present inventors examined the location of the hard solder referred to in the double depression igniter of FIG. 8 and observed that, after reflowing the hard solder, The location of the hard solder was extremely variable. Given the need to precisely control the area and placement of the hard solder, the location of the hard solder hole was reconsidered. The present inventors noted that, in the double depression dress conductor frame, the hole above the surface of the ignitor and speculated was raised that slowly between the bottom of the hole 9 and the branch 1 allowed the hard solder to flow out of control . Accordingly, the inventors reconsidered the simple depression design of Figure 7. In contrast to the double depression design, when hard welding is reflowed in a simple depression design, the contact between the ceramic branch and the defining ring The hard solder hole keeps the solder hard in the precise desired area and thus eliminates the variability of hard solder location. Accordingly, in some preferred embodiments, the ring defining the hard solder hole 9 is in contact with the ceramic branch 1. The finite element analysis of the double depression design further revealed that the typical hard welding operation caused a deformation residual in the hard solder of approximately 15-20%, which is significant. As indicated above, increasing the area of the hard solder would reduce this value, but would also increase the effort on the igniter. In view of this advantageous exchange, it was decided that the use of a hard solder with increased fault deformation would be more acceptable. Thus, in preferred embodiments of the present invention, the hard solder has a residual strain of at least 22%, more preferably at least 25%. Although the stress experienced by hard welding seems to be the most important issue in the hard welding operation, there is nevertheless some effort in the ignitor produced during hard welding, particularly in the region of ceramic material (in the order of microns). The CTE of the hard solder and the ceramic material in this evaluation differed by approximately 50% (ie the lower value was half the highest value), since it can be reduced. the residual stress on this region further reducing the disproportion of CTE, in some embodiments, the disproportion of CTE between the hard solder and the ceramic material is less than 25% over the temperature range of 22-850 ° C. To the service efforts of the double depression design, the highest score was that the disproportions of CTE between the ceramic branch, the hard welding, the material Conductor frame and encapsulant would produce high stresses. The analysis of finite elements showed that the valuable efforts resulting from them would remain in ceramic material but they would not be very large and the probability of durability was estimated in almost 100%. However, it is believed that these efforts could be further reduced if the disproportion of CTE between the ceramic branch and the hard solder material were further reduced. Therefore, in some embodiments, the disproportion of CTE between the ceramic branch and hard solder is less than 25% over the temperature range of 22-850 ° C. Although the use of a hard solder hole in the simple depression design provides the skilled person with a convenient means to accurately locate the hard solder, which nevertheless contains limitations. In particular, when the hard solder is deposited through the solder hole of simple fastener design of Figure 7 (which controls the extension area), the electrical connection between the hard solder and the conductor frame takes place only around from the periphery of hard welding. This periphery is very thin. Since electricity must travel through this thin region, the region has a high electrical resistance. Therefore, this design requires the use of a relatively large amount of hard solder in order to decrease the strength of this region. However, since a large amount of hard solder can cause stress problems related to the CTE, there is a parallel desire to minimize the amount of hard solder used. Thus, the need for electrical conduction through the thin edge of the hard solder presents a problem. Therefore, in some embodiments (as shown in Figure 9), the conductor frame and the ignitor branch and electrical connection are placed across the large surface face of the hard solder and this is done using what is called a "single point contact". This single point contact is produced by contacting a hard hemispherical weld 7 with a solid fastener 65 on the conductor frame. Since the electrical contact comes from the holder 65 through the substantially integral hemisphere of the hard solder 7, the solder is electrically more efficient and thus less hard solder is used. Therefore, the "single point" design has the advantage of minimizing the amount of hard solder that is needed to provide acceptable electrical resistance in the connection with the hard solder. In this design, the branch 1 is slid past both the first end 88 and the second end 89 of the conductor frame sleeve.

The single point design of Figure 9 can be further improved by using a fastener having a flat contact face 66, as shown in Figure 10. The flat contact face has the effect of further flattening the hard solder, thus reducing the strength of the hard solder and allowing the even more effective use of hard solder. Although the single-point contact conductor frame design of Figure 9 provided many advantages over single and double depression modes, it still possessed characteristics that could cause problems for typical printer applications. Thus, the present inventors set out to eliminate these problems and produced an improved conductor frame design shown in Figure 10. These new features of the improved igniter will now be discussed. Despite the improved single point design of Figure 9, the present inventors observed that electrical integrity problems still persisted during their use and hypothesized that these problems were due to the lack of mechanical integrity in the connection between the fastener, the hard solder and the branch. First, the present inventors noted that, for each of the designs of Figs. 1, 7-9, the ignitor in cement is finally or completely embedded (shown as C in Fig. 9). The present inventors then hypothesized that, when the ignitor is heated to service temperatures, the high CTE of expanding element located between the fastener and the ceramic branch sometimes causes the fastener to detach from the hard weld, thus destroying the connection Electrical in the location of the hard solder in the disconnection procedure. Furthermore, it was observed that the contact resistance of the single point modalities was inconveniently about 2-4 times higher than that of the simple depression design of Figure 1 (which uses a hard solder hole to control the area of hard welding). Without wishing to be bound by theory, it is believed that the spring contact mode relies more strongly on the surface contact conductivity than the orifice mode and thus the conductivity of this joint is more dependent on the conductivity of the frame material. of conductors and is therefore prone to oxidation of the conductor frame. Therefore, the electrical connection between the hot surface element and the conductor frame is most preferably made by providing a hard weld within the hole of the conductor frame. In the preferred embodiment (as illustrated in FIG. 10), the hard solder is located away from the holder, preferably in a hole 7 in the base 51 opposite the ceiling 55, in which the ring of the conductor frame makes contact with the branch ceramic. In this mode, the cement can not reach between the conductor frame and the ceramic branch in the vicinity of the hard solder. Thus, in this mode, even if the cement with high CTE content pulls the opposite fastener away from the ignitor branch during service, the critical connection between the conductor frame, the hard solder and the branch is not affected by that disconnection and The electrical integrity of the hard solder is maintained. In the design of Figure 10, the fastener 65 having a flat surface area contact 66 provides greater mechanical stability during handling of the hard pre-weld. Another problem or contact designs of simple depression, double depression and single point is related to the use of the inner wall 54 (or "lip") in each conductor frame. As indicated above, these lips help to maintain the stability of the assembly during the handling of the hard pre-weld and ensure that the ignitor branches remain straight. However, by conductor frames 56 are put in place on the end of each branch of a fork-type ignitor, the inner walls 54 of the conductor frame are oriented towards one another and closely approximate one another. Since the distance outside the branch-to-branch frame is typically very small (only approximately 0.0254 mm) and each inner wall of the conductor frame has a significant thickness (approximately 0.254 m), the presence of the interior walls significantly decreases the distance effective between the branches in approximately 50%, thus significantly increasing the danger of causing a short circuit (by wall-to-wall contact). This danger is particularly problematic because it is known that the branches of the fork ignitor designs have the ability to fractionate a little. In effect, in the initial design test showing substantially in Figure 1, the igniters are plagued by short circuits in some high-potential test situations. In addition, the lip 54 of the ignitor of Figure 1 presents an additional design drawback. Although many ceramic igniters want a fork geometry, other ceramic igniters (such as those disclosed in U.S. Patent No. 5,786,565) contain a solid insert between their branches. Although this insert can provide additional support, the ignitor presents an obstacle to the easy insertion of the ignitor branches to the conductor frames in direction A. Finally, it was believed that the presence of these lips prevented the flow of the refractory cement used to wrap the ignitor. Therefore, in the preferred embodiment (as shown in Figures 5 and 10), the inner lip of each conductor frame is removed, thereby producing a conductor frame having only three walls. The lipless designs of FIGS. 5 and 10 maintain the effective distance between the conductive ceramic branches (thus eliminating the increased risk of short circuit) and allow the easy insertion of the fork style ceramic ignitors having inserted pieces disposed between their ceramic branches. . Another problem with the simple depression and double depression designs of Figures 1, 7-9 is related to their use of circular orifices for hard welding. A circular orifice has the advantages of maximizing the effectiveness of the hard solder's ability to make a good electrical connection and typically provide uniform stresses at the edges. However, in cases where relatively large hard solder contact areas are required, the continuous expansion of the circle will bring the edge of the hard solder towards the edge region of the igniter branch. Since it is known that the edge of the branch contains a relatively high frequency of machining related defects, the expansion of the hard solder to the edge region is inconvenient. Therefore, in a preferred embodiment (as shown in Figure 5), the hole for hard welding is elongated over the direction of the branch. This has the advantage of increasing the surface coverage of the hard solder without getting too close to the problematic branch material edges. Therefore, in some embodiments, the hard solder coating is characterized by a pad of non-equidistant axes having an aspect ratio of at least 1.5: 1 whose main axis is displaced over the length of the branch. Preferably, the conformation is an oval. Another problem with the design of the single fastener of FIG. 1 relates to the use of a V-shaped flap 13. As indicated above, a conductive wire is placed in the V-shaped trough of the fin 13, then compressed. mechanically the side walls of the tundish together, thus producing a mechanically secure electrical connection between the conductor frame and the conductive wire. However, it was noted that the strength of this assembly step was so significant that it often resulted in ignitor fracture and / or hard solder flux. further, it was observed that the safety of this mechanical connection was subject to variability, thus causing inconvenient variability in the electrical properties of the ignitor. Therefore, in the preferred embodiment (as shown in Figure 5), the V-shaped trough is removed and replaced with a simple flat fin 13. In this embodiment, this connection is made between the connecting wire and the conductor frame by directly welding the conductive wire to the fin of the conductor frame with resistance. Since the force used to make this connection is low, the danger of rupture of either the ignitor branch or the hard solder is equally low. In addition, it was observed that the direct solder connection produces a more or less recognizable result in terms of electrical properties. For these two reasons, the fin option welded directly with resistance is superior to the V-shaped trough mode. Thus, in the preferred embodiments, the conductor frame has a fin 13 and the conductive wire is directly welded with resistance to the fin. Another problem with the simple fastener design of Figure 1 relates to the relative inability to accommodate a plurality of different ignitor designs having different distances between the center lines of their branches. As indicated above, it is convenient to center the hard solder pad on each ceramic branch. However, it is also convenient to use the same set of conductor frames for as many different ignitor designs as possible. Since ceramic igniters are obtainable in any number of branch separations and branch thicknesses, the distance between the center lines of the branches will vary from ignitor to ignitor. Accordingly, the use of a simple set of pre-connected conductor frames (having a fixed distance between their respective centered holes of hard solder pad on the ceilings) will not provide the desired centering of the hard solder pad over the ignitor branches. for each design. Since the convenience of using the same basic set of conductor frames for as many different ignitor designs as possible is great, the present inventors decided to vary the location of the hard solder pad hole to locations that are not in the center of the frame. of conductors to ensure that the hard solder was always centered on the underlying ceramic branch. Therefore, in some embodiments (such as Figure 5) the hole 9 for hard welding is not centered on the roof of the conductor frame. The igniters of the present invention can be used in many applications, including gas-phase fuel ignition applications such as economical ovens and stoves, basic countertop heaters, gas or oil antennas and stove tops. Since the system no longer contains the temperature sensitive white solder layer (which melts at approximately 635 ° C), the system can be used in applications where the service atmosphere exceeds 635 ° C. This feature has particular advantage in applications in upper stove covers in economical stoves, in which the temperature in the area of the termination is higher than 635 ° C.

Claims (49)

NOVELTY OF THE INVENTION CLAIMS

1. - An electrical connection for a hot-surface ceramic element, comprising: a) an electroconductive ceramic material having a first end, b) an electroconductive hard solder of active metal contacting at least a portion of the first end, and ) a metal termination that makes contact with the hard solder of active metal, characterized in that the termination is chemically bonded to the hard solder of active metal.

2. A hot-melt ceramic element connection, comprising: a) an electroconductive ceramic material having first and second ends, b) a first electroconductive hard solder pad of active metal contacting at least a portion of the first end, c) a second electrically conductive electroconductive solder pad that contacts at least a portion of the second end, d) a first metal termination that makes contact with the first hard solder pad of active metal, and e) a second metal termination contacting the second active metal hard solder pad, characterized in that each metal termination is chemically bonded to its corresponding hard solder pad of active metal.

3. - The connection according to claim 2, further characterized in that each metal termination comprises a sleeve having a first end and a second end, and in that each end of the electroconductive ceramic material is received at the first end of its respective sleeve.

4. The connection according to claim 3, further characterized in that each sleeve has a transverse hole and that each hard solder pad is substantially in the hole and makes contact with the end of ceramic material received in the sleeve.

5. The connection according to claim 4 further comprising a conductive wire having a first end, each metal termination further comprising a fin extending from the second end of each sleeve and further characterized in that the first end of the wire conductor is electrically connected to the fin.

6. The connection according to claim 5, further characterized in that the ceramic connector material comprises silicon carbide.

7. The connection according to claim 5, further characterized in that the first and second ends of the conductive ceramic material comprises: a) from 20 to 65 v / o of a ceramic material selected from the group consisting of aluminum nitride, nitride of silicon and boron nitride, and mixtures thereof, and b) of about 35 to 80 v / o MoSi2 and SiC in a ratio and volume of about 1: 1 to about 1: 3.

8. The connection according to claim 7, further characterized in that the hard solder of active metal comprises: a) between about 0.1% by weight and 5% by weight of active metal selected from the group consisting of titanium, zirconium, niobium , nickel, palladium and gold, and mixtures thereof, and b) between about 95% by weight and 99.9% by weight of filler metals selected from the group consisting of silver, copper, indium, tin, zinc, lead, cadmium and phosphorus , and mixtures thereof.

9. The connection according to claim 8, further characterized in that the conductor frame comprises a metal selected from the group consisting of nickel-based compositions containing at least 85% nickel, Ni-Cr alloys, silver , gold and platinum.

10. The connection according to claim 3, further characterized in that each sleeve comprises: a) a base having a substantially flat upper surface, b) a side wall that rises substantially perpendicular from the base, and c) a roof connected to the side wall, the roof being substantially parallel to the base.

11. - The connection according to claim 10, further characterized in that the roof comprises a fastener that extends towards the base

12. The connection according to claim 11, further characterized in that each base has a transverse hole and because each pad metal is substantially within its respective hole and makes contact with the end of ceramic material received in its respective sleeve.

13. A ceramic igniter comprising: a) an electrically conductive ceramic material comprising the cold ends and a resistive zone therebetween, b) a pair of terminations, each termination comprising a sleeve having a first end and a second end , further characterized in that each end of the electroconductive ceramic material is permanently received at the first end of its respective sleeve and is in electrical connection therewith, because each termination is a metallic termination, the ignitor further comprising a pair of metal pads, making contact each metal pad with its respective ceramic end and its respective metal termination to provide electrical connection between the ceramic end and the metal termination, because each sleeve has a ring defining a transverse hole, because each metal pad is substantially in its respective hole and makes contact with the end of the ceramic material received in its sleeve, and because each ring makes contact with its respective ceramic end.

14. The ceramic ignitor according to claim 13, further comprising a pair of conductive wires, each conducting wire having a first end, each metal termination further comprising a fin extending from the second end of each sleeve, having the fin an upper surface, and in that the first end of each conductive wire is electrically connected to the upper surface of its respective fin.

15. The ignitor according to claim 14, further characterized in that the conductive ceramic metal comprises silicon carbide and in that each metal pad comprises a hard solder of active metal.

16. The ignitor according to claim 15, further characterized in that the first and second ends of the conductive ceramic material comprise in each case: a) from 20 to 65 v / o of a ceramic material selected from the group consisting of nitride of aluminum, silicon nitride and boron nitride, and mixtures thereof, and b) from about 35 to 80 v / o MoSi2 and SiC in a ratio and volume of from about 1: 1 to about 1: 3.

17. The ignitor according to claim 16, further characterized in that the hard solder of active metal comprises: a) between about 0.1% by weight and 5% by weight of active metal selected from the group consisting of titanium, zirconium, niobium , nickel, palladium and gold, and mixtures thereof, and b) between about 95% by weight and 99.9% by weight of filler metals selected from the group consisting of silver, copper, indium, tin, zinc, lead, cadmium and phosphorus , and mixtures thereof.

18. The igniter according to claim 16, further characterized in that each conductor frame comprises a metal selected from the group consisting of nickel-based compositions containing at least 85% nickel (preferably at least 95% by weight). Nickel), Ni-Cr alloys, silver, gold and platinum.

19. The ignitor according to claim 13, further characterized in that each sleeve comprises: a) a base having a substantially flat upper surface, b) a side wall that rises substantially perpendicularly from the upper surface and c) a roof substantially parallel to the flat upper surface of the base and connected to the side wall.

20. The igniter in accordance with claim 10, further characterized in that each ceramic branch is adjusted in interference within its respective sleeve.

21. The igniter according to claim 20, further characterized in that each side part has a height and each branch has a thickness, because the height of each side wall is less than the thickness of its respective branch and because each ceramic branch makes contact with its respective roof and base to form the interference fit.

22. The igniter according to claim 20, further characterized in that each sleeve also comprises a fastener having a first end extending from its roof and a second end, because at least a portion of each fastener extends towards its end. base and because each ceramic end makes contact with its base and the second end of its fastener to form the fit in interference.

23. The igniter according to claim 20, further characterized in that each roof comprises a depression extending from the ceiling towards its base and because each ceramic end makes contact with the depression and its base to form the fit in interference.

24.- The igniter according to claim 23, further characterized in that each depression contains a ring defining a transverse hole, each metal pad is substantially in its hole and makes contact with the ceramic end received in its sleeve and because each ring makes contact with its respective ceramic end.

25. The igniter according to claim 23, further characterized in that each roof comprises two depressions that extend downward toward their respective bases and each ceramic end is adjusted against interference with its depressions.

26. - The ignitor according to claim 25, further characterized in that each roof also comprises a ring defining a transverse hole, each hole being between its two respective depressions, because each metal pad contacts the end of ceramic material received in the cuff and because each ring does not make contact with its respective ceramic end.

27. The ignitor according to claim 19, further characterized in that each ceramic end defines a branch having a central axis and because each branch is arranged in its respective sleeve and its central axis is substantially parallel to its respective side wall.

28.- The igniter according to claim 19, further characterized in that each base has no lip that extends from it, because each ceramic end defines a branch that has a central axis and because each branch is arranged in its respective sleeve and its central axis is substantially perpendicular to its respective side wall.

29. The igniter according to claim 19, further characterized in that the CTE of the metal pad is within 25% of the CTE of ceramic material.

30. The ignitor according to claim 19, further characterized in that each end of the ceramic material is a branch having a pair of parallel edges and in that the metal pad is centered between the parallel edges.

31. - The igniter according to claim 19, further characterized in that each ceramic end has a density that is at least 95% of the theoretical density.

32.- The igniter according to claim 19, further characterized in that each metal pad has a fault deformation of at least 22%.

33.- The ignitor according to claim 19, further characterized in that each roof comprises a fastener that extends down towards its base to form a lower face, because each metal pad contacts both the underside of its fastener and with the end of ceramic material received in its sleeve.

34.- The igniter according to claim 33, further characterized in that each lower face is substantially parallel to the upper face of its base.

35.- The igniter according to claim 19, further characterized in that each ceramic branch comprises first and second surfaces, each roof comprises a fastener that extends down towards its base to form an inner face, are in contact each fastener with the first surface of its respective ceramic end, because each base also comprises a ring defining a transverse hole, because a metal pad is substantially in each hole and makes contact with the second surface of the ceramic material received in its sleeve and because the ring of each base makes contact with its branch.

36. The igniter according to claim 35, further characterized in that the first and second surfaces of each ceramic branch are opposite surfaces.

37.- The igniter according to claim 19, further characterized in that each sleeve essentially consists of: a) a base having a substantially flat upper surface, b) a side wall that rises substantially perpendicularly from the upper surface, and c) a roof substantially parallel to the flat top surface of the base and connected to the side wall.

38.- The igniter according to claim 37, further characterized in that the igniter also comprises an insert arranged between the ends of the ceramic igniter.

39.- The igniter according to claim 19, further characterized in that each end of ceramic material is a branch having a pair of substantially parallel edges and each metal pad which makes contact with its respective branch forms an elongated surface between the substantially parallel edges of its respective branch, each elongate surface defining an axial length and a radial length, because each axial length is greater than its respective radial length.

40. - The igniter according to claim 39, further characterized in that each axial length is greater than 1.5 times its respective radial length.

41. The igniter according to claim 39, further characterized in that each metal pad has an oval shape.

42. The igniter according to claim 19, further comprising a pair of conductive wires, each conducting wire extending a first end, each sleeve further comprising a fin extending from the second end of its sleeve, the fin having a flat upper surface, and further characterized in that the first end of each conductive wire is directly welded with resistance to the flat upper surface of its respective fin.

43.- The igniter according to claim 19, further characterized in that each base has two substantially parallel edges, because each end of the ceramic material is a branch having a pair of parallel edges and because the parallel edges of each base are substantially parallel to the parallel edges of its branch.

44. The igniter according to claim 43, further characterized in that each base also comprises a transverse hole and because each hole is not centered between the parallel edges of its respective base.

45. The ignitor according to claim 19, further comprising a lip that rises substantially perpendicular from each base in a plane substantially parallel to the side wall.

46.- A procedure for making a ceramic igniter termination, comprising the steps of. a) providing a ceramic igniter having first and second ends, each end having an outer surface, b) providing a pair of sleeves, each sleeve having an inner surface corresponding substantially to the outer surface of the first and second ends, c) inserting the first and second ends of the ceramic igniter to the pair of sleeves, d) chemically bonding the inner surface of the sleeve to the outer surface of the branch received therein.

47. The method according to claim 46, further characterized in that each sleeve has a transverse hole therethrough and that the step of chemically binding is performed by the steps of. i) depositing a hard solder of active metal in the hole after step c), i) reflowing the hard solder.

48. The method according to claim 46, further characterized in that the step of chemically binding is performed by the steps of: i) coating the ends of the ceramic element with a hard solder of active metal before step c), and i) reflowing the hard solder after step c). 49.- The method according to claim 46, further characterized in that the ceramic igniter has essentially no open porosity.