Abstract:
A method for manufacturing a contract arrangement for a vacuum switching tube having a contact carrier and a contact piece joined to the contact carrier in a vacuum using soldering material. The contact carrier is made of electrically highly conductive material, for example, copper, and the contact piece is made of a flame-resistant sintering material containing copper. The contact piece is pressed flat directly onto the contact carrier, generating a gap along the contact surface, and the soldering material is arranged on areas directly bordering the gap of the contact surface between the contact piece and the contact carrier. Subsequently, in a vacuum through the application of heat, the soldering material is brought to the melting point, and the molten soldering material penetrates into the gap of the contact surfaces between the contact carrier and the contact piece.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a method for manufacturing a contact arrangement for a vacuum switching tube having a contact carrier and a contact piece that is joined to the contact carrier in a vacuum using a soldering material. 
     RELATED TECHNOLOGY 
     A method for manufacturing a contact arrangement for a vacuum chamber is described in German Patent Document No. 196 32 573 A1, in which the contact carrier in a vacuum is coated with a contact layer through sintering an appropriate powder and its subsequent solidifying. It is further known to solder a contact carrier to a contact piece in a vacuum using a soldering material that is arranged in between, by melting the soldering material and pressing contact carrier and contact piece together. Mechanical, frictional-locking bonds between contact piece and contact carrier are also known, reference being made, by way of example, to German Patent Document No. 44 47 391 C1 and German Patent Document No. 195 34 398 A1. 
     In FIGS. 1 a  and  1   b , there is a schematic illustration of a known method for producing a soldered connection between a contact carrier  1  and a contact piece  10  using an intermediate layer of a soldering material  11 , for example a soldering disk. In this context, contact piece  10  is preferably provided with a saucer-shaped recess  101 , into which are set soldering disk  11  and then contact carrier  1  at its mounting end. After being heated in the vacuum, soldering disk  11  melts and produces soldered connection  30  between contact carrier  1  and contact piece  10 . In this method, it is disadvantageous that in the hanging arrangement of contact piece  10  on contact carrier  1 , a sufficient positive locking between contact piece and contact carrier must be present during the production of the soldered connection in order to prevent contact piece  10  from falling away in the melting of the soldering disk. In the hanging arrangement, in the case of larger contact pieces, it is frequently necessary, during the soldering process in the vacuum, to employ auxiliary structures in order to prevent the contact piece from falling away or, on the other hand, to provide for a supplementary positive locking of contact piece  10  on contact carrier  1 . 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide a method by which a contact arrangement having soldered bonding sites can be manufactured reliably and more simply using a smallest possible optimal quantity of soldering material. 
     The present invention provides a method by which the contact piece is directly pressed flat onto the contact carrier, leaving a gap along the contact surface, and the soldering material is arranged in areas directly bordering on the gap of the contact surface between the contact piece and the contact carrier, and subsequently, in a vacuum, through applying heat, the soldering material is brought to the melting point and the melted soldering material penetrates into the gap of the contact surfaces between the contact carrier and the contact piece. 
     The method according to the present invention can be applied with particular advantage to the manufacture of contact arrangements for vacuum switching tubes. The method according to the present invention makes it possible for the contact surface between contact carrier and contact piece to be wetted with soldering material on virtually its entire surface, i.e., sufficiently. In addition, the bond between contact carrier and contact piece is strengthened through the melted soldering material rising in the gap—the annular gap—between contact carrier and contact piece, the gap being mainly vertical and, towards the exterior, adjoining the contact surface between contact carrier and contact piece. Depending on the type of configuration, an optimal dosing is possible of the quantity of soldering material that is required to achieve the sufficient soldered connection between contact carrier and contact piece. In particular, the method according to the present invention makes it possible, in a simple manner, to produce a contact carrier having a contact piece hanging from it, i.e., in the hanging position. Applying the method according to the present invention to the production of vacuum switching tubes makes it possible to manufacture, for example, all of the soldering points of a preassembled vacuum switching tube in one processing step, i.e., in one oven cycle. 
     According to one version of the present invention, a contact piece is used that has a planar, saucer-shaped recess, into which the contact carrier at its mounting end is set, an annular gap between contact piece and contact carrier being formed at the planar gap of the contact surface, and the soldering material being placed in ring-like fashion around the contact carrier at the annular gap emerging between contact carrier and contact piece, so that after the melting, the soldering material is pulled by gravity and capillary action into the annular gap and the gap along the saucer-shaped recess. In this variant of the method according to the present invention, a virtually full-surface wetting of the contact surface between the contact carrier and the contact piece is achieved by the molten soldering material flowing and pressing into the gap from the sides. In addition, however, as a result of the solder collecting in the lateral vertical gaps, a good bond of great stability is achieved between contact carrier and contact piece. 
     According to a further version of the present invention, however, it is also possible to introduce the soldering material via bore holes that lead through the contact carrier to the contact surface between the contact carrier and contact piece. According to one version of the present invention, a contact piece is used that has a planar, saucer-shaped recess, into which the contact carrier at its mounting end is set, and, additionally, a contact carrier is used, which has at least one bore hole running through the contact carrier to the contact surface having the saucer-shaped recess, and the soldering material is poured into the bore holes of the contact carrier so that, after the melting, due to gravity and capillary action, the soldering material presses into the gap along the saucer-shaped recess, including into the circumferential annular gap. 
     For these process techniques, the solder can be placed into the bore holes of the contact carrier in the form, for example, of wire. In addition, these bore holes make possible an improved degasification of the space between the contact piece and contact carrier. 
     In a further embodiment of the method, it is proposed that a contact piece may be used that has a planar, saucer-shaped recess, into which the contact carrier at its mounting end is set, and a contact carrier be used, which, at its contact surface adjoining the saucer-shaped recess, has at least one recess, and the soldering material be poured into the recess of the contact carrier, so that, after the melting, the soldering material penetrates, due to gravity and capillary action, into the gap along the saucer-shaped recess, including into the peripheral annular gap. 
     In all of these cases, during the soldering, an oversupply of soldering material rises up again through the vertical gaps and bore holes, so that an optimal wetting and dosing of the soldering material is possible. 
     A further example of a method according to the present invention provides setting a contact piece into a saucer-shaped recess of a contact carrier and applying the soldering material in the form of a soldering paste onto the contact piece and over the annular gap end between the contact carrier and contact piece, so that, after the melting, the soldering material is pulled by gravity and capillary action into the gap along the saucer-shaped recess. 
     Here, too, it is possible to fix the contact piece on the contact carrier without a positive-locking or frictional connection. This variant is designed especially for securing contacts in the non-hanging position. As a solder paste, it is preferred to use one having a silver or copper base, the binding agent or binders evaporating during the heating-up process in a vacuum, leaving no residue. During the time when the soldering material is in a molten liquid state in a vacuum, the contact piece is held by the surface tension of the soldering material and/or the latter&#39;s adhesive force, so that precise positioning is also assured. 
     To achieve a good contact soldering and sufficient stability of the bond between contact piece and contact carrier, it is proposed that an amount of soldering material be used such that, after the complete wetting of the gap between contact carrier and contact piece, the remaining molten mass of solder is used to seal the solder supply points, for example, as a residual plug seals the solder supply points. 
     Thus the method according to the present invention makes it possible to satisfactorily manufacture soldered connections between contact pieces and contact carriers even in a hanging arrangement, the method being particularly advantageous when applied in connection with vacuum switching tubes. The method according to the, present invention can be refined and applied in that the contact arrangement composed of contact carrier, contact piece, and soldering material is preassembled into a unit having further components constituting the vacuum switching tube, components that are bonded to each other at soldering points using soldering material, along with a second contact arrangement, a shielding part, cover parts, insulating parts, and a bellows, and the preassembled unit being placed into a vacuum soldering oven, one of the two contact arrangements being in the hanging position of the contact piece and, under the influence of the vacuum, the simultaneous melting of all of the soldering material being effected at all of the soldering locations by heat, so that all of the soldered connections of the vacuum switching tube are produced in one process step. 
     According to the present invention, therefore, the soldering points of a piece to be connected, i.e., specifically, of the contact piece having a contact carrier, can be produced both in the hanging position as well as in the standing position. Since the soldering material penetrates into the gap between contact piece and contact carrier only after melting, there is no falling away due to excessive solder melting, which is the case when the soldering material is arranged beforehand between contact carrier and contact piece. For carrying out the method according to the present invention, at least for the soldered connection to be generated in the hanging position, a mechanical, clamping bond or mechanical positive-locking fit is sufficient to avoid a falling away of the contact piece from the contact carrier during the production of the soldered connection. 
     In order to prevent a not-yet-soldered contact piece from falling away from the contact carrier during a soldering process in the hanging position, the proposal is made to provide for a mechanical and/or friction-locking and/or form-locking bond at least in areas between the contact piece in the contact carrier by configuring them appropriately outside of the contact surfaces of contact piece and contact carrier forming the planar gap, the bond being produced in the assembly of contact piece and contact carrier. A mechanical bond of this type between contact piece and contact carrier can be provided, for example, through creating a profiling at least in areas on the lateral surface of the contact carrier and/or, if appropriate, also on the interior-side lateral surface of the recess of the contact piece, to achieve a light clamping of the contact carrier in a saucer-shaped recess of the contact piece for sufficient stability in the hanging position. This profiling, for example, can be provided as milled knobs or knurls having fins and depressions, or also, for example, by only a single profiling in the shape of a protruding rise on the lateral surface of the contact carrier. 
     In the assembly of the contact carrier and contact piece, instead of achieving a mechanically stable bond for a hanging position using a skeleton form, a flanging, or profiling, the contact pieces and contact carriers to be bonded to each other can also be joined using a friction- and positive-locking bond, such as in a bayonet lock. The minimal annular gap remaining in this context can be supplied, for example, from a soldering material supply—deposit—on the contact carrier using sufficient solder, for example using a corresponding piece of soldering wire. 
     The projections or grooves of a bayonet lock of this type can be shaped so as to taper into a slight cone, so that by twisting the contact piece in a contact carrier made of soft copper, a clamping screw connection is achieved having a good supporting capacity. In this context, it is possible to achieve a good, planar, and friction-locking bond between the contact piece and the contact carrier. At the same time, the groove of the bayonet lock bond can function as the solder supply channel and then as the soldered connection point for the two parts to be bonded subsequently, using solder. 
     The contact carriers and the contact pieces, in accordance with the application purpose and the load of the vacuum switching tube, can be made from known materials, such as were described in the documents mentioned above regarding the related art. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is explained in further detail below in exemplary embodiments with reference to the drawings, in which: 
     FIGS. 1 a  and  1   b  show a schematic depiction of the contact soldering of a contact piece to a contact carrier using a soldering disk in accordance with the related art, before (FIG. 1 a ) and after (FIG. 1 b ) the soldering process; 
     FIGS. 2 a  and  2   b  show a schematic depiction of the contact soldering of contact carrier and contact piece using soldering material disposed on the outside of the contact arrangement, before (FIG. 2 a ) and after (FIG. 2 b ) the soldering process; 
     FIGS. 3 a  and  3   b  show a schematic depiction of a contact soldering of contact piece to contact carrier using soldering material fed through the contact carrier, before (FIG. 3 a ) and after (FIG. 3 b ) the soldering process; 
     FIGS. 4 a  and  4   b  show a variant of the method shown in FIG. 3 a  and  3   b;    
     FIG. 5 shows a variant of the method shown in FIG. 4 a;    
     FIG. 6 shows a contact soldering for bonding a contact piece to the contact carrier using soldering paste, in a schematic depiction in the standing position; 
     FIG. 7 shows a schematic cross-section of the vacuum switching tube after a completed contact soldering; 
     FIGS. 8 a ,  8   b , and  8   c  show a contact arrangement having a contact carrier FIG. ( 8   a ) and a contact piece (FIG. 8 b ), as well as a top view of the contact piece having a bayonet lock (FIG. 8 c ). 
    
    
     DETAILED DESCRIPTION 
     In FIG. 7, by way of example, a vacuum switching tube is depicted in schematic form having two contact arrangements, of which first contact arrangement  2 ,  20  is fixedly arranged on the housing and second contact arrangement  1 ,  10  is positioned in the housing so as to be movable by a bellows  7 . If a soldered connection between contact carrier  1  and contact piece  10  or contact carrier  2  and contact piece  20  cannot be produced in the standing position, i.e., the contact piece is placed onto the contact carrier from above, the problem arises to devise a more reliable method for producing the soldered connection of the contact arrangement in the hanging arrangement of the contact piece. For this purpose, as a rule, according to the related art, an effective positive locking and/or frictional locking is necessary, so that in response to melting the soldering material located, as in FIGS. 1 a ,  1   b , between the contact surfaces to be bonded, contact piece  10  does not float or slide. If, as a consequence of the saucer-shaped recess  101 , see FIGS. 1 a ,  1   b , the lateral overlap of contact piece  10  is used for the positive locking and frictional locking, then no soldered connection can form in this lateral area since no molten solder, or an insufficient amount, penetrates here. 
     According to the proposal of the present invention, see FIGS. 2 a  and  2   b , between the parts to be bonded to each other, namely contact piece  10  and contact carrier  1 , first a sufficient positive-locking or mechanically supportive connection is produced, for example by configuring the contact piece so as to have a saucer-shaped recess  101 , into which is fitted the contact carrier at its mounting end, which can be correspondingly shaped. However, it is particularly advantageous to provide for a profiling  105  at least in areas on the lateral surface of the contact carrier and/or the single-sided lateral surface of the contact piece, to achieve a light clamping effect of the contact carrier in saucer-shaped recess  101  of the contact piece for a sufficient stability in the hanging position. The profiling can be shaped, for example, as milled knobs  105  having fins and depressions. Thus an adequate positive-locking bond between contact piece  10  and contact carrier  1  is created, a contact gap between the two parts remaining along saucer-shaped recess  101 , which is composed of annular gap RS, running to the outside, and planar gap FS. At the exterior circumference of the contact arrangement, where the contact gap between contact piece  10  and contact carrier  1  ends, soldering material  11 , for example in an annular shape as soldering wire, is placed on the edge of contact piece  10  adjacent to contact carrier  1 . Contact carrier  1 , prepared in this manner, contact piece  10 , which is pressed down, and soldering material  11 , placed externally, are heated in a vacuum in a vacuum chamber, so that soldering material  11  melts and penetrates into gap RS between contact piece  10  and contact carrier  1  and, consequently, it is pulled into gap FS between the contact surfaces, leading to the complete or near complete, wetting by molten solder of the contact surface between contact carrier and contact piece. At the same time, solder also remains, down to the upper external edge of contact piece  10 , and there forms a remaining plug  11   a , sealing the gap to the outside, resembling a hollow channel made of soldering material. Using the method according to the present invention, it is possible also to fill the vertical gaps at the side between contact piece  10  and the contact carrier using molten solder and thus to produce a significantly improved, strengthened bond between the parts. The bonding surface wetted by soldering material is designated as  30 . 
     In the variant in FIGS. 3 a  and  3   b , provision is also made at first for a light positive locking between contact piece  10  and contact carrier  1 , i.e., without a soldering foil in between or, for example, a profiling, as in FIGS. 2 a  and  b . For this purpose, contact piece  10  is configured, for example, using a saucer-shaped recess  101 , into which contact carrier  1  is set. The mechanical bond produced in this manner by frictional locking and/or positive locking is sufficient to prevent contact piece  10  in the hanging position from falling out before and during the production of the soldered connection. Contact carrier  1  itself has at least one, as in FIG. 4 a , or, for example, two, as in FIG. 3 a , bore holes  102 , 103  running in the axial direction parallel to the axis, the bore holes functioning to receive soldering material  11 , for example, in the form of soldering wire. Bore holes  102 , 103  penetrate to the contact surface at the contact piece. After the parts, preassembled in this manner, are placed into a vacuum chamber, in a vacuum, and heat is applied, soldering material  11  melts and, due to gravity and capillary action, penetrates into the gap formed between the contact surfaces of contact piece  10  and contact carrier  1  along saucer-shaped recess  101 , and fills up the gap, also ascending at the lateral edges up to the upper edge, as in FIGS. 3 b  and  4   b . The contact surface between contact carrier and contact piece is completely and adequately wetted in turn by the soldering material, and at the same time the bond between contact carrier and contact piece is strengthened by the rising soldering material at the external vertical gaps between contact piece and contact carrier. The quantity of solder is measured such that a residue of soldering material remains in the shape of a hollow channel  11   a  at the foot of bore holes  102 , 103 , sealing them. In the event that bore holes  102 , as in FIG. 4 a , lead directly to the outside, they also function for improved degasification of the space between contact piece and contact carrier. To produce bond  30  between contact carrier  1  and contact piece  10 , a relatively small quantity of solder is necessary in the application of the method according to the present invention. 
     In FIG. 5, a further possible configuration of the preceding arrangement of soldering material is depicted partially outside the contact surfaces between contact carrier and contact piece to be bonded to each other in the contact soldering, contact carrier  1  having a recess  104  at its side facing contact piece  10 , the recess receiving the soldering material. Here, as well, the contact arrangement, preassembled as depicted in FIG. 5, is placed into a vacuum chamber, and there, in a vacuum, soldering material  11  is brought to the melting point through the application of heat, as a result of which it penetrates into the adjoining gaps between contact piece  10  and contact carrier  1  and, in accordance with the supply of solder, also rises into the lateral vertical gaps, thus producing the desired stable bond. 
     For standing arrangements of the contact soldering of a contact piece  20  to a contact carrier  2 , an arrangement in accordance with FIG. 6 is proposed, in which contact piece is also placed directly into a recess  21  on the upper side of contact carrier  2 . In this manner, a positive-locking grip is already provided. The soldering material, however, is not placed into the gap between contact piece  20  and contact carrier  2 , but rather on top, for example, as soldering paste  11  in a layer. During the heating procedure in a vacuum, the binding agent and binders of the soldering paste evaporate and the soldering material in a molten state can penetrate into the contact gap between contact carrier  2  and contact piece  20  along recess  21  and thus produce the desired contact soldering in this area. 
     In FIGS. 8 a  and  b , the contact arrangement is depicted having a contact carrier  1  in the form of a moving conductor and a contact piece  10  having a cup-shaped recess  101 , which is configured for a mechanical bond in the form of a bayonet lock. In FIG. 8 c , the top view of contact piece  10  having recess  101  and two lugs  107  protruding to the inside are depicted, which are shaped so as to protrude on the cylindrical interior side of recess  101 . Contact carrier  1  on the lateral surface in the area coming into contact with contact piece  10  has oppositely oriented grooves  106  arranged so as to run slightly diagonally, into which contact piece  10  having its lugs  107  can be introduced in a screw-like fashion. Via a short rotation, contact piece  10  is then firmly pressed onto contact carrier  1 . The remaining gap can then also be filled using solder, as is explained in FIGS. 2 a  and  2   b , or also using solders from a solder repository, as is depicted, for example, in FIGS. 3 a ,  4   a ,  5 , and the soldered connection is produced. 
     The bayonet lock between contact piece and contact carrier can also have two or more beveled grooves and protuberances situated on the periphery, the grooves being able to be configured either on the contact carrier or on the contact piece, and the lugs then on the respective other part. For further improving the fixing of the contact piece on the contact carrier using a bayonet lock, the groove/grooves can also be given a slightly conical shape, i.e., tapering at the end, so that during the rotation of the parts to be joined with each other, a firm, gripping screw connection is achieved in the contact carrier made of a soft copper. In addition, n contact carrier can also be used as a solder supply channel and also forms a good solder connection area between the contact carrier and contact piece. 
     In FIG. 7, a vacuum switching tube is schematically depicted having a fixedly arranged contact carrier  2 , and having a contact piece  20  fixedly joined via a soldered connection  31 , as well as having a contact arrangement, movable in the axial direction of the arrow, including contact carrier  1  and contact piece  10 , fixedly joined via the soldered connection  30 , for example, as in FIG. 2 b . The housing is composed of pot-like cover parts  5  and  6 , an insulator  8  being arranged in between. The one pot-like cover is soldered to stationary contact carrier  2  in the area of connecting surfaces  32 —soldering points. Other pot-like cover  6  is secured at movable contact carrier  1 , specifically via two soldering points  34 , 36 , a bellows  7  being connected in between. Pot-like covers  6 , 5  are also connected to the insulator via soldering points  35 , 33 . On the interior side of contact pieces  10 ,  20 , shielding part  4  having getter ring  3  is arranged for shielding the metal vapor arc, retaining the radiation heat, and dissipating the latter in the covers, as well as for sufficiently shielding the insulator from condensing metal vapor. 
     Using the method according to the present invention for the possibility of the contact soldering of contact piece  10  to the contact carrier in the latter&#39;s hanging position, as is explained in FIGS. 3 a  through  5 , it is possible to reassemble the vacuum tube depicted in FIG.  7  and its components, to arrange the corresponding soldering material in the area of the contact gap of contact piece  10  and contact carrier  1  as well as at all connection points to be soldered  31 ,  32 ,  33 ,  34 ,  35 ,  36 , and then to place the assembly, preassembled in this manner, into a vacuum soldering oven, and there, in a vacuum, through the application of heat, to produce all of the soldering connections in one working cycle—an oven cycle.