GB2582574A

GB2582574A - Improved method of manufacturing a contact arrangement for a switching device with low contact resistance

Info

Publication number: GB2582574A
Application number: GB1904105.2A
Authority: GB
Inventors: Faast Rainer
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2019-03-25
Filing date: 2019-03-25
Publication date: 2020-09-30
Also published as: GB201904105D0

Abstract

A method of manufacturing a contact arrangement 1a for a switching device in which a contact pad carrier 2a is cut out or punched from a base material and a contact pad 3a is then soldered or welded onto the contact pad carrier. A machining surface A of the contact pad facing away from the contact pad carrier is then treated by laser ablation by a laser beam L generated by a laser 4. An oxide layer on the machining surface of the contact pad may be removed by the laser beam. Information related to the contact arrangement or switching device may be written onto the contact arrangement by the laser beam (figure 4). A surface pattern may be manufactured onto the contact arrangement by the laser beam. The machining surface of the contact pad may have a convex shape and may be made of silver or silver alloy. Inert gas comprising >99.8% Argon may be blown in the region of the laser ablation, which may be done with a Ytterbium fibre laser having a wavelength of 1064nm and a power of <50W. The contact arrangement may be built into the switching device before laser ablation, which may take place after >100 days.

Description

Improved method of manufacturing a contact arrangement for a switching device with low contact resistance

TECHNICAL FIELD

The invention relates to a method of manufacturing a contact arrangement for a switching device, wherein a contact pad carrier is cut out our punched out from a base material in a step a) and wherein a contact pad is sold or weld onto the contact pad carrier in a step b).

BACKGROUND ART

In switching devices such as circuit breakers, short circuiting switches and the like, contact arrangements of the above type are often installed. Unfortunately, an oxide layer may unintentionally be formed on a surface of the contact pad, which deteriorates the transfer resistance of a contact pair of a switch. This is particularly the case if the contact pad is made of silver or a silver alloy because during the welding or soldering step the contact pad is heated up so much that an oxide layer is unintentionally generated on the surface of the contact pad. Unfortunately, this oxide layer must be removed so as to restore a low transfer resistance of the contact pad. Usually, the oxide layer is mechanically removed, in particular by means of grinding and/or brushing.

A number of problems arise when the oxide layer is removed by means of grinding and/or brushing. First, a precise fixation of the contact arrangements is needed. Second, the contact surface of the contact pad may have a convex or spherical shape, which needs a sophisticated machining process to remove the oxide layer from all over the contact surface. Furthermore, wear of the grind stones and/or the brushes causes the need to adapt the machining process to the changed shape of the grind stones and/or the brushes. Moreover, foreign particles originating from the grind stones and/or the brushes may be forced into the surface of the contact pad. These foreign particles in turn can lead to rust or oxidation thus deteriorating the transfer resistance of a contact pair of a switch again and thus contravening the intention of the cleaning process. All in all, the above influences lead to relatively low and varying quality of the contact arrangements for switching devices.

DISCLOSURE OF INVENTION

Accordingly, a problem of the invention is to provide an improved method of manufacturing a contact arrangement for a switching device. In particular, the contact arrangement shall be produced with high and stable quality.

The problem of the invention is solved by a method as defined in the opening paragraph, wherein a machining surface of the contact pad facing away from the contact pad carrier is treated by means of laser ablation with a laser beam generated by a laser in a step c) after step b).

In particular, an oxide layer on the machining surface of the contact pad facing away from the contact pad carrier is removed by the laser beam generated by the laser.

By use of the laser ablation process, the machining surface of the contact pad facing away from the contact pad carrier can be cleaned easily with high cleaning quality. In particular, the fixation of the contact arrangement does not need to withstand high forces, there is no need to adapt the machining process to a changing shape of a grind stone and/or a brush, and no foreign particles originating from a grind stone and/or a brush are forced into the machining surface of the contact pad. Pollutants are simply burned away by the laser. All in all, the contact arrangement can be produced with high and stable quality by use of the laser ablation process.

Further advantageous embodiments are disclosed in the claims and in the description as well as in the figures.

Advantageously, information related to the contact arrangement or the switching device, which the contact arrangement is built into or intended to built into, is written onto the contact arrangement by means of the laser beam generated by the laser. For example, this information may be related to the type of the contact arrangement, the material of the contact pad, a switching capacity of the switching device, the name of the manufacturer, etc. The information can be alphanumerical information and/or binary coded information.

Advantageously, a surface pattern is manufactured onto the contact arrangement by means of the laser beam generated by the laser. In this way, very fine structures influencing the switching behaviour of the contact arrangement can be produced. For example, fine lines may be engraved into the contact pad. Moreover, such a pattern may also be a safety feature to guarantee that a contact pad has been produced by a particular manufacturer and is no counterfeit.

Beneficially, the machining surface of the contact pad facing away from the contact pad carrier can have a convex shape. This could be useful for positively influencing the switching behaviour of the contact arrangement, but does not negatively influence the ablation or cleaning process. Basically, the ablation or cleaning process is the same for flat and spherical surfaces as the focus of the laser beam can be kept the same in both cases.

Beneficially, the contact pad can be made of silver or a silver alloy. In this way, a favourable material for the contact arrangement is used without to take care of its tendency to oxidise.

In a very advantageous embodiment, inert gas is blown in the region of the laser ablation, in particular inert gas, comprising > 99.8% Argon. In this way, a very fine and homogenous surface of the contact can be obtained.

In yet another very advantageous embodiment, the laser ablation process is done with a Ytterbium fibre laser, in particular having a wavelength of 1064 nm. It has turned out that this kind of laser is particularly useful to clean the surface of the contact pad.

Beneficially, the laser ablation process is done with a laser power of 50 W. In this way, a soiled and/or oxidised layer can be removed without burning too much of the base material of the contact pad under the soiled and/or oxidised layer.

Beneficially, the laser beam generated by the laser is moved over the machining surface of the contact pad line by line during the laser ablation process. In this way, the ablation or cleaning can easily be controlled by the size of the line feed.

Beneficially, the laser ablation process is done with a feed in a range from 1.5 m/min to 7 m/min. In this way, a very fine and homogenous surface of the contact can be obtained, too Advantageously, the contact arrangement is built into a housing part of said switching device between steps b) and c) of the method of manufacturing the contact arrangement for a switching device. Beneficially, a time between step b) and c) can be > 100 days. In this way, the contact pad may be cleaned very late in the production process of a switching device so that the same may leave the factory in perfect condition. A storage time of the contact arrangement of any length does not influence the quality of the switching device. In particular, information related to the switching device, which the contact arrangement is built into, can be written onto the contact arrangement by means of the laser beam in this stage.

BRIEF DESCRIPTION OF DRAWINGS

The invention now is described in more detail hereinafter with reference to particular embodiments, which the invention however is not limited to.

Fig. 1 shows a first embodiment of a contact arrangement before the contact pad is fixed to the contact pad carrier; Fig. 2 shows the contact arrangement of Fig. 1 in a state, in which the contact pad is treated by a laser beam; Fig. 3 shows a second embodiment of a contact arrangement in a state, in which the contact pad is treated by a laser beam; Fig. 4 shows that information is written onto the contact arrangement by means of the laser beam; Fig. 5 shows an oblique view of an exemplary switching device and Fig. 6 shows the switching device with the upper housing part being detached.

DETAILED DESCRIPTION

Generally, same parts or similar parts are denoted with the same/similar names and reference signs. The features disclosed in the description apply to parts with the same/similar names respectively reference signs. Indicating the orientation and relative position (up, down, sideward, etc) is related to the associated figure, and indication of the orientation and/or relative position has to be amended in different figures accordingly as the case may be.

The proposed method comprise the steps of: a) cutting out our punching out a contact pad carrier 2a from a base material and b) soldering or welding a contact pad onto 3a the contact pad carrier 2a Fig. 1 shows a first embodiment of a contact arrangement la right before the contact pad 3a is fixed to the contact pad carrier 2a.

Fig. 2 shows the contact arrangement la of Fig. 1 in a state, in which a machining surface A of the contact pad 3a facing away from the contact pad carrier 2a is treated by means of a laser beam L generated by a laser 4. In this way, a laser ablation process takes place on the machining surface A after step b). The laser beam L may be moved over the machining surface A as indicated by arrows. Accordingly, the laser beam L generated by the laser 4 can be moved over the machining surface A of the contact pad 3a line by line during the laser ablation process. In this way, the ablation or cleaning process can easily be controlled by the size of the line feed.

By use of the laser ablation process, the machining surface A of the contact pad 3a facing away from the contact pad carrier 2a can be cleaned easily with high cleaning quality. In particular, an oxide layer on the machining surface A of the contact pad 3a can be removed in this way. Accordingly, particularly contact pads 3a made of silver or a silver alloy can be used for the contact arrangement la, which have favourable characteristics in view of a switching contact, but which however also have a tendency to oxidise when the contact pad 3a is heated during the welding or soldering step. Of course, one should note that the laser beam L is also capable of removing other oxide layers and dirt in general, which simply is burnt away by the laser beam L. Moreover, the use of a laser beam L is also of advantage if the machining surface A of the contact pad 3a facing away from the contact pad carrier 2a has a convex shape as this is the case in the example of Fig. 1. As the laser beam L has just a low divergence, the convex shape of the contact pad 3a does not influence the ablation process very much.

In Fig. 2, the contact pad 3a has a spherical machining surface A, and the contact pad carrier 2a comprises two exemplary bends. Of course one should note that the shape of the contact pad carrier 2a and the contact pad 3a shown in Fig. 2 is not mandatory, and other shapes are possible as well. In this context, Fig. 3 shows a second embodiment of a contact arrangement 1 b with a flat contact pad carrier 2b and a contact pad 3b with an even machining surface A facing away from the contact pad carrier 2b, Generally it is of advantage if the laser 4 is a Ytterbium fibre laser, in particular having a wavelength of 1064 nm. It has turned out that this kind of laser 4 is particularly useful to clean the machining surface A of the contact pad 2a, 2b. The laser power may be s 50 W. In this way, a soiled and/or oxidised layer can be removed without burning too much of the base material of the contact pad 3a, 3b under the soiled and/or oxidised layer. Beneficially, the laser ablation process is done with a feed in a range from 1.5 m/min to 7 m/min. In this way, a very fine and homogenous surface of the contact pad 3a, 3b can be obtained. In a very advantageous embodiment, inert gas is blown in the region of the laser ablation, in particular inert gas, comprising > 99.8% Argon. In this way, a very fine and homogenous surface of the contact pad 3a, 3b can be obtained, too.

Fig. 4 shows a further variant of the proposed method. In detail, information B related to the contact arrangement 1 a, 1 b or the switching device (see Figs. 5 and 6), which the contact arrangement 1 a, 1 b is built into or intended to built into, is written onto the contact arrangement 1 a, lb by means of the laser beam L generated by the laser 4. For example, this information may be related to the type of the contact arrangement 1 a, 1 b, the material of the contact pad 3a, 3b, a switching capacity of the switching device 5, the name of the manufacturer of the contact arrangement la, 1b, etc. The information B can be alphanumerical information and/or binary coded information.

Alternatively or in addition, it is possible to manufacture a surface pattern onto the contact arrangement 1 a, lb by means of the laser beam L. In this way, very fine structures influencing the switching behaviour of the contact arrangement 1 a, 1 b can be produced. For example, fine lines may be engraved into the contact pad 3a, 3b. Moreover, such a pattern may also be a safety feature to guarantee that the contact arrangement 1 a, 1 b has been produced by a particular manufacturer and is no counterfeit.

Figs. 5 and 6 show an oblique view of an exemplary switching device 5. The switching device 5 comprises a housing 6 with a lower housing part 7 and an upper housing part 8. Fig. 5 shows the switching device 5 with the upper housing part 8 being attached, and Fig. 6 shows the switching device 5 with the upper housing part 8 being detached.

The switching device 5 comprises a first contact arrangement 1 c and a second contact arrangement 1d, which form terminals of the switching device 5. The switching device 5 also comprises a lever 10, which is operatively coupled to a switching axle 11. The switching axle 11 comprises switching arms 12 and contact arrangements le on the end of the switching arms 12. When the contact arrangements le touches the contact arrangement 1 c, there is a electrical connection between the terminals formed by the first contact arrangement lc and the second contact arrangement 1 d, and if the contact arrangements le does not touch the contact arrangement 1c, there is no electrical connection between the terminals formed by the first contact arrangement lc and the second contact arrangement 1 d.

Generally, the first arrangements lc..le may be shaped like the contact arrangements la and 1 b shown in Figs. 1 to 4 or may have any other applicable shape.

Advantageously, step c) (treating the machining surface A of the contact pad 3a, 3b facing away from the contact pad carrier 2a, 2b by use of the laser beam L) takes place after the contact arrangement has been built into the lower housing part 7 of the switching device 5. In other words, the contact arrangement lc..le is built into the lower housing part 7 of the switching device 5 between steps b) and c) of the method of manufacturing the contact arrangement 1a..1e for the switching device 5. In particular, a time between step b) and c) can be > 100 days. In this way, the contact pads 3a, 3b may be cleaned very late in the production process of the switching device 5 so that the same may leave the factory in perfect condition. A storage time of the contact arrangement 1a..1e of any length does not influence the quality of the switching device 5. In particular, also information related to the switching device 5, which the contact arrangement 1 a..1 e is built into, can be written onto the contact arrangement 1a..1e by means of the laser beam L in this stage.

All in all, the proposed method provides the following advantages. A fixation of the contact arrangement 1 a..1 e does not need to withstand high forces. Furthermore, there is no need to adapt the machining process to a changing shape of a grind stone and/or a brush. In addition, no foreign particles originating from a grind stone and/or a brush are forced into the machining surface A of the contact pad 3a, 3b. Finally, pollutants are simply burned away by the laser beam L. All in all, the contact arrangement 1a..1e can be produced with high and stable quality by use of the laser ablation process.

It is noted that the invention is not limited to the embodiments disclosed hereinbefore, but combinations of the different variants are possible. In reality, the contact arrangement 1a..1e and/or the switching device 5 may have more or less parts than shown in the figures. The contact arrangement 1a..1e and/or the switching device 5 as well as parts thereof may also be shown in different scales and may be bigger or smaller than depicted. Finally, the description may comprise subject matter of further independent inventions.

It should also be noted that the term "comprising" does not exclude other elements and the use of articles "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.

LIST OF REFERENCE NUMERALS

1 a..1 e contact arrangement 2a, 2b contact pad carrier 3a, 3b contact pad 4 laser switching device 6 housing 7 (lower) housing part 8 (upper) housing part lever 11 switching axle 12 contact arm A machining surface B information L laser beam

Claims

-10 -CLAIMS1. Method of manufacturing a contact arrangement (1a..1e) for a switching device (5), comprising the steps of a) cutting out our punching out a contact pad carrier (2a, 2b) from a base material and b) soldering or welding a contact pad onto (3a, 3b) the contact pad carrier (2a, 2b), characterized in that c) a machining surface (A) of the contact pad (3a, 3b) facing away from the contact pad carrier (2a, 2b) is treated by means of laser ablation after step b) with a laser beam (L) generated by a laser (4).
2. Method according to claim 1, characterized in that an oxide layer on the machining surface (A) of the contact pad (3a, 3b) facing away from the contact pad carrier (2a, 2b) is removed by the laser beam (L) generated by the laser (4).
3. Method according to claim 1 or 2, characterized in that information (B) related to the contact arrangement (1a..1e) or the switching device (5), which the contact arrangement (1a..1e) is built into or intended to built into, is written onto the contact arrangement (1a..1e) by means of the laser beam (L) generated by the laser (4).
4. Method according to any one of claims 1 to 3, characterized in that a surface pattern is manufactured onto the contact arrangement (1a..1e) by means of the laser beam (L) generated by the laser (4).
5. Method according to any one of claims 1 to 4, characterized in that the machining surface (A) of the contact pad (3a, 3b) facing away from the contact pad carrier (2a, 2b) has a convex shape.
6. Method according to any one of claims 1 to 5, characterized in that the contact pad (3a, 3b) is made of silver or a silver alloy.
7. Method according to any one of claims 1 to 6, characterized in that inert gas is blown in the region of the laser ablation, in particular inert gas, comprising > 99.8% Argon.
8. Method according to any one of claims 1 to 7, characterized in that the laser ablation process is done with a Ytterbium fibre laser, in particular having a wavelength of 1064 nm.
9. Method according to any one of claims 1 to 8, characterized in that the laser ablation process is done with a laser power of 50 W.
10. Method according to any one of claims 1 to 9, characterized in that the laser beam (L) generated by the laser (4) is moved over the machining surface (A) of the contact pad (3a, 3b) line by line during the laser ablation process.
11. Method according to any one of claims 1 to 10, characterized in that the laser ablation process is done with a feed in a range from 1.5 m/min to 7 m/min.
12. Method of manufacturing a switching device (5), characterized in that the contact arrangement (1a..1e) is built into a housing part (7) of said switching device (5) between steps b) and c) of the method according to any one of claims 1 to 11.
13. Method according to any one of claims 1 to 12, characterized in that a time between step b) and c) is > 100 days.