EP1897115A1

EP1897115A1 - Electrode system for a lamp

Info

Publication number: EP1897115A1
Application number: EP06761686A
Authority: EP
Inventors: Rainer Koger; Dirk Rosenthal; Klaus-Dieter Stein
Original assignee: Patent Treuhand Gesellschaft fuer Elektrische Gluehlampen mbH
Current assignee: Osram GmbH
Priority date: 2005-06-28
Filing date: 2006-06-22
Publication date: 2008-03-12
Also published as: TW200719381A; KR20080017419A; US20090134800A1; WO2007000141A1; CA2613571A1; DE102005030113A1

Abstract

The invention relates to an electrode system for lamp assembly, said system comprising at least one electrode holding rod (22) and an electrode head (26) that are interconnected by a soldering process using a solder filler (76). The solder filler is a sintered moulded part consisting of an essentially eutectic alloy.

Description

Electrode system for a lamp

Technical area

The invention relates to an electrode system according to the preamble of patent claim 1, a method for producing such an electrode system according to the preamble of patent claim 10 and a discharge lamp provided with such an electrode system.

State of the art

The electrode system according to the invention can be used in principle in a variety of different lamps. However, the main field of application of the electrode system is likely to be in the manufacture of high-wattage HBO® or XBO® high pressure discharge lamps.

From the general state of the art it is known for the production of solder joints on electrode systems for high-wattage HBO® or

XBO® high-pressure discharge lamps High-temperature soldering materials

(Solder) of pure platinum wire to use. Such electrode systems consist essentially of an electrode head, which has a

Solder connection is attached to an electrode support rod. To prepare the solder joint, the platinum wire is used as a soldering additive in a

Receiving bore of the electrode head introduced. Subsequently, the

Electrode holding rod inserted into the receiving bore. In another

Operation is the electrode system in the soldering area on

Soldering temperature heated and melted the inserted platinum wire. Due to the resulting surface bond and mutual

Penetration (diffusion) between filler metal and base material, the electrode head is high-strength soldered and electrically conductive with the electrode holding rod. Although such soldering materials made of pure platinum wire allow a highly heat-resistant solder joint of the electrode system, but are very expensive due to the low platinum occurrence and thereby increase the manufacturing cost of the electrode system.

For this reason, see. the lamp manufacturing already soldering materials from cheaper zirkon wire use. A disadvantage of such soldering materials is that it can lead to embrittlement of the joint during the soldering process without sufficient diffusion of the solder additive in the base materials. In other words, the zirconium solder additive does not penetrate sufficiently into the structure of the base materials and forms no or only a deficient alloy. This can lead to a brittle fracture of the solder joint and thus to a failure of the electrode system in such solder joints.

To improve the bonding properties, it is also known from the general state of the art to use paste or powdered soldering materials made of high-temperature molybdenum-ruthenium alloys for soldering the electrode systems. Although these solutions allow, compared to zirconium-containing soldering materials, improved strength of the solder joint with respect to the individual solder components reduced melting temperature, but due to the organic substances contained in pastes and thereby, especially in closed soldering rooms, ie in soldering processes with pickled solder remaining unwanted residues not suitable for the production of high-strength solder joints. Powdered soldering materials, however, are complicated to handle and due to the health hazard, for example, by inhalation of the highly fine, powdery particles suitable only with suitable protective devices for the production of electrode systems. Presentation of the invention

The invention has for its object to provide an electrode system for lamp construction and a method for producing such an electrode system, in which over conventional solutions, an improved solder joint is made possible with minimal device complexity.

This object is achieved with regard to the electrode system by the feature combination of claim 1 and with regard to the method for producing such an electrode system by the features of claim 10. Particularly advantageous embodiments of the invention are described in the dependent claims.

The lamp system according to the invention for lamp construction has an electrode holding bar and an electrode head, which are connected to each other by a soldering process by means of a soldering additive. According to the invention, the brazing filler material is a sintered molded part of essentially eutectic alloy. This solution allows due to the formation of the solder additive as a sintered molded part with any geometry improved handling in manufacturing. Due to the use according to the invention of an essentially electic alloy, the molded part has a fixed melting point which is below the individual melting points of the alloy constituents and thus considerably facilitates the production of the solder joint. In other words, the molding according to the invention has a melting behavior without alloy-typical two-phase melting due to the substantially eutectic composition of the powder mixture. The transition from the molten to the solid state of the molding takes place completely and directly during cooling after the soldering process. This solidification leads after cooling to a fine-grained, uniform structure of the soldering material with excellent strength properties.

An inventive method for producing an electrode system is carried out with the steps: a) introducing the sintered molded part in the electrode head

b) inserting the electrode holding rod in the electrode head and

c) soldering of the electrode holding rod with the electrode head.

According to a particularly preferred embodiment of the invention, the molding is made of a molybdenum-ruthenium powder mixture.

The molybdenum-ruthenium-powder mixture preferably contains about 38 to 48% by weight of ruthenium. In this area, the alloy has essentially eutectic properties. This achieves an alloy with a melting point suitable for the soldering process and prevents the formation of a brittle, intermetallic sigma phase.

It has proved to be particularly advantageous if the molybdenum-ruthenium powder mixture contains 58% by weight of molybdenum and 42% by weight of ruthenium (MoRu42). This eutectic composition has a lower melting temperature than the individual alloying constituents molybdenum and ruthenium, thereby enabling a simplified, energy-efficient production of the electrode system. The melting temperature of the molybdenum-ruthenium alloy is, for example, in the vicinity of the melting temperature of pure platinum.

The solder filler material formed as a molded part is in an embodiment according to the invention at least in sections to the component contour of the joining partners, i. adapted to the geometry of the electrode holding rods and / or the electrode head. Preferably, the molding has a substantially circular cross-section. As a result, the molded part, for example for soldering with solder inserted into the soldering area, is easy to handle in terms of manufacturing technology.

According to a particularly preferred embodiment of the

Soldering additive a soldering disc. Due to their shape, the soldering discs are easy to manufacture and a uniform production Heat coupling via the components, for example by means of induction or Widerstandslötverfahren is guaranteed.

Preferably, the molding is at least partially introduced for the production of the soldered joint in one of ^• the electrode holding rod and the electrode head limited soldering space.

The electrode system according to the invention is preferably used for the production of discharge lamps, in particular for the production of high-wattage HBO®. or XBO® high pressure discharge lamps.

Brief description of the drawings

The invention will be explained in more detail below with reference to a preferred embodiment. Show it:

Figure 1 is a schematic representation of a HBO® mercury vapor high-pressure discharge lamp with an electrode system according to the invention;

FIG. 2 shows a side view of the anode-side electrode system of the HBO® mercury high-pressure discharge lamp from FIG. 1 with added soldering material and

FIG. 3 shows an individual view of the soldering additive material from FIG. 2.

Preferred embodiment of the invention

The invention will be described below with reference to an HBO® mercury vapor

Explained high-pressure discharge lamp, which is used for example in microlithography for the production of semiconductors. As already mentioned, however, the electrode system according to the invention is by no means limited to such lamp types. FIG. 1 shows a schematic representation of a two-sided HBO® mercury vapor high-pressure discharge lamp 1 in short arc technique. This has a discharge vessel 2 made of quartz glass with an inner space 4 and two diametrically arranged, sealed Kolbenschäften 6, 8, the free Εndabschnitte 10, 12 are each provided with a base sleeve 14, 16. In the interior 4 protrude two diametrically arranged electrodes 18, 20, between which forms a gas discharge during lamp operation. In the interior 4 of the discharge vessel 2 an ionizable filling is included, which consists essentially of mercury and a high-purity noble gas. The electrodes 18, 20 are each designed as a two-part electrode system consisting of a current-feeding, rod-shaped electrodes hard ng 22, 24 and one, with this soldered, discharge-side head electrode 26 (anode) or • top electrode 28 (cathode). For mounting the electrode heads 26, 28 on the electrode holding rods 22, 24, the electrode heads 26, 28 are each provided on the discharge-distant side with a blind hole 30, 32, in which end portions 34, 36 of the electrode holding rods 22, 24 are attached. According to FIG. 1, the lower electrode head 28 is designed as a conical head cathode for generating high temperatures in order to ensure a defined arc attachment and sufficient electron flow due to thermal emission and field emission (Richardson equation). The upper electrode head 26 in FIG. 1 is designed as a thermally highly charged, barrel-shaped head anode, in which the emission power is improved by sufficient dimensioning of the electrode size. In order to suppress or at least significantly reduce negative gas reactions for the luminous flux and the life behavior of the discharge lamp 1, a getter 38 made of tantalum is mounted inside the discharge vessel 2. In the embodiment shown, the getter 38 is mounted as a metal band on the anode-side electrode holding bar 22. To hold the electrodes 18, 20 in the discharge vessel 2, truncated cone-shaped holding elements 40 made of quartz glass are used in the piston stems 6, 8, which are provided with an axially extending through hole 42 for receiving the electrode holding bars 22, 24. The holding rods 22, 24 of the electrodes 18, 20 are guided in the through-holes 42 in such a way that they extend into the inner space 4 and there the electrode heads 26 and 28, respectively wear. On the base side, the electrode holding rods 22, 24 are each extended beyond the holding elements 40 and inserted into a receiving bore 44 of an annular molybdenum plate 46 and soldered thereto. The molybdenum plate 46 is adjoined in each case by a quartz cylinder 48, which is melted into the piston shaft 6, 8 and on the outer surface 50 of which four molybdenum foils 52 soldered to the molybdenum plate 46 are arranged, forming a gas-tight current feedthrough. The molybdenum foils 52 are soldered at one end section 54 to a contact plate 56, which is connected to a base pin 58 on the cathode side (bottom in FIG. 1) or a stranded wire 60 on the anode side for electrical contacting of the electrode system 18, 20. For convection cooling of the anode-side base sleeve 14 (in Figure 1 above) this is additionally provided with cooling fins 62. The electrical connection of the HBO® discharge lamp 1 to the supply voltage takes place on the cathode side via the base pin 58 and on the anode side via the stranded wire 60 and a cable lug 64 connected thereto. The cathode-side region of the discharge vessel 2 is partially provided with a heat-reflecting lamination to improve the efficiency of the discharge lamp 1 metallic coating 66 provided.

According to FIG. 2, which shows a side view of the anode-side electrode system 18 of the HBO® high-pressure mercury discharge lamp 1 from FIG. 1 before soldering the head anode 26 to the electrode holding bar 22, the end section 34 of the electrode holding bar 22 is provided with a peripheral chamfer 68 and into which Blind hole 30 of the head anode 26 introduced. Since the attachment of the head cathode 28 on the electrode support rod 24 differs from the attachment of the head anode 26 only by a step-shaped abutment shoulder 70 of the discharge-side end portion 36 (see Figure 1), the general term electrode head is used in the following for head anode 26 and head cathode 28. To prepare the solder joint, a soldering material 74 introduced into the soldering space 72 defined by the electrode holding bar 22 and electrode head 26 is used. According to the invention, the brazing filler material 74 is a sintered molded part 76 of essentially eutectic alloy. This solution allows due to the formation of the solder additive 74 as a sintered molded part 76 with any geometry improved handling in manufacturing. Due to the According to the invention, using a substantially eutectic powder mixture, the molding 76 has a fixed melting point which is below the individual melting points of the alloying constituents in the vicinity of the melting point of pure platinum, thereby substantially facilitating the production of the solder joint. The molding 76 thus has a melting behavior due to the substantially eutectic composition without alloy-typical two-phase melting. The transition from molten to solid state occurs completely and immediately during the cooling of the solder joint. This solidification leads to a fine-grained, uniform structure of the molten molding 76 after cooling with excellent strength properties. In the embodiment shown, the sintered molding 76 contains a molybdenum-ruthenium powder mixture consisting of 58% by weight molybdenum and 42% by weight ruthenium (MoRu42). This eutectic composition has a relation to the individual alloying constituents molybdenum and ruthenium reduced melting temperature and thereby enables a simplified, energy-efficient production of the electrode system 18, 20. The melting temperature of pure platinum compared to cost molybdenum-ruthenium alloy is in the range of the melting temperature of

Platinum. The molded part 74 is produced in a pressing process with a pressure of about 8 kN and a subsequent sintering process at a temperature of about 1800 ° C.

According to FIG. 3, which shows an individual representation of the molded part 76 from FIG. 2, the molded part 76 is formed with a circular cross-section adapted to the component contour of the joining partners, ie the electrode heads 26, 28 and electrode support rods 22, 24. Due to their disk-shaped shape, the molded parts 76 are easily produced in terms of production engineering and ensure uniform heat coupling during the soldering process. Furthermore, the sintered solder disk 78 is easy to handle compared to powdered soldering materials manufacturing technology. A health hazard due to inhalation of very fine, powdery particles is prevented by the formed as a solid soldering additive 74. In the following, the production of the electrode system 18, 20 will be explained by way of example with reference to FIGS. 1 to 3. In a first step, the molded part 76 is introduced into the soldering region 72, ie into the blind holes 30, 32 of the electrode heads 26, 28. In a further operation, the ^• electrode ^holding rod 22, 24 is inserted into the blind hole 30, 32, so that this, according to Figure 2, abuts the end face of the molding 76. Subsequently, the required soldering temperature is introduced by heat coupling from the outside, for example by means of a high-frequency induction process in the soldering region 72. The parameter guide during soldering is chosen so that the heat input is high enough to melt the molding 76 and by the resulting surface bond and mutual penetration (diffusion) between solder additive 76 and electrode support rod 22, 24 and electrode head 26, 28, the workpieces high-strength and to be electrically conductively soldered together. After the heat input, the molded part 76 is completely fused and at least partially fills the soldering space 72, wherein the end portion 34, 36 of the electrode holding bar 22, 24 is completely received in the blind bore 30, 32 of the electrode head 26, 28 (see FIG. 1). The soldering gap between the end portion 34, 36 of the electrode holding rod 22, 24 and the blind hole 30, 32 of the electrode head 26, 28 is thereby completely filled by the solder additive 74 and produces a dense, electrically conductive connection.

The electrode system according to the invention is not limited to the described circular solder disk 78, but the

Solder additive 74 have any geometric shape. In particular, the soldering additive 74 according to the invention can be produced as a wire-shaped or annular shaped part. Furthermore, the solder filler material 74 can be used for all known from the prior art soldering, which allow a defined heat input into the soldering region 72. It is essential to the invention that the soldering additive material 74 used to produce the soldered connection has an essentially eutectic alloy and is formed by a sintering process to form a molded part 76. Disclosed is an electrode system 18, 20 for the construction of lamps, comprising at least one electrode support rod 22, 24 and an electrode head 26, 28, which are connected to one another by a soldering process by means of a soldering filler 74, wherein the solder additive 74 is a sintered molding 76 of substantially eutectic alloy is.

Claims

claims

An electrode system for the construction of lamps, comprising at least one electrode support rod (22, 24) and an electrode head (26, 28) joined together by a soldering process by means of a solder additive (74), characterized in that the solder additive (74) is sintered Molded part (76) of substantially electrical alloy.

An electrode system according to claim 1, wherein the molding (76) is made of a molybdenum-ruthenium powder mixture.

3. The electrode system of claim 2, wherein the molybdenum-ruthenium powder mixture comprises about 38 to 48 wt .-% ruthenium.

4. An electrode system according to claim 2 or 3, wherein the molybdenum-ruthenium powder mixture contains 58 wt .-% molybdenum and 42 wt .-% ruthenium (MoRu42).

5. Electrode system according to one of the preceding claims, wherein the molded part (76) is at least partially adapted to the geometry of the electrode holding rod (22, 24) and / or electrode head (26, 28).

6. The electrode system according to one of the preceding claims, wherein the molded part (76) has a substantially circular cross-section.

7. Soldering additive according to one of the preceding claims, wherein the molded part (76) is a soldering disc (78).

8. The electrode system according to any one of the preceding claims, wherein the molded part (76) in an at least partially by the electrode holding rod (22, 24) and the electrode head (26, 28) limited soldering space (72) is introduced.

9. discharge lamp, in particular HBO® or XBO® high-pressure discharge lamp with an electrode system (18, 20) according to any one of the preceding claims.

10. A method for producing an electrode system (18, 20) according to any one of claims 1 to 8, comprising the steps:

a) introducing the sintered molding (76) into the electrode head (26, 28)

b) inserting the electrode holding rod (22, 24) in the electrode head (26, 28) and

c) soldering the electrode holding rod (22, 24) to the electrode head (26, 28).