DE102015103003B3 - Electrical contact element - Google Patents

Abstract

The present invention relates to an electrical contact element, in particular a switching spring, preferably a switching spring for a thermal temperature controller or a thermal fuse. The contact element comprises a band-shaped carrier (2) made of a resilient, electrically conductive material, and an electrically conductive contact layer (3) which is located on a flat side of the band-shaped carrier (2) and connected to the latter. Furthermore, it is provided that the band-shaped carrier (2) and the contact layer (3) are connected to one another by means of a planar laser welding connection, the laser welding connection has a laser welding seam (4) or laser welding cone (4a), which in each case is completely defined by the cross-sectional area of the band-shaped carrier (FIG. 2) through into a partial region of the cross-sectional area of the adjacent contact layer (3), and to achieve the planar laser welding connection along the surface of the band-shaped carrier (2) (a) a plurality of elongated laser welds (4) are arranged, (b) a laser weld (4) is oriented in two dimensions and / or (c) a plurality of laser welding cones (4a) are distributed over a surface.

Description

The present invention relates to an electrical contact element, in particular a switching spring, preferably a switching spring for a thermal temperature controller or a thermal fuse.

Technological background

Spring-loaded electrical contact elements comprise a band-shaped carrier made of a resilient, electrically highly conductive material and an areal limited contact layer of a material with low electrical resistance (eg Ag or an Ag alloy), which is located on a flat side of the band-shaped carrier and is firmly connected to the latter. Such contact elements are commonly used in thermal temperature controllers and thermal fuses as switching springs. In a thermal temperature controller, the switching spring is held under pretension on the mating contact via a holding element, which in turn is connected to a thermo-reactive component (eg bimetal). Upon reaching a predetermined temperature switching threshold, the shape or position of the thermal component changes, whereupon the holding function of the switching spring is eliminated and the latter opens the electrical contact due to its inherent bias. The contact is closed again, provided that the thermal component due to temperature moves back to the starting position and the switching spring is thereby pressed back into the closed position of the electrical contact. When a thermal fuse is released when releasing the fuse, the holding function of the switching spring irretrievably.

An electrically conductive contact layer is applied to a band-shaped carrier made of a resilient, electrically conductive material usually by resistance welding. For this purpose, the electrically conductive contact layer must first be provided with a further, less electrically conductive layer which serves as a welding aid (eg a Cu alloy). This additional layer serves as a necessary thermal reservoir for the resistance welding process. At the contact surface of the welding aid upstanding, longitudinal welding webs are provided, which serve to initiate the welding process by a held there peak ignition. In order to ensure a current flow, an electrically conductive connection contact has to be attached to the upper side of the electrically conductive contact layer during resistance welding. The method has the disadvantage that due to the upstanding on the underside of the welding aid welding webs it can often lead to a permanent gap formation between the band-shaped carrier and the electrically conductive contact layer. Moreover, due to the top electrical connection contact during welding, the top of the electrically conductive contact layer may be contaminated. Gaps as well as impurities of the contact layer and the less electrically conductive intermediate layer lead to an undesirable increase in the contact resistance. There is therefore a need to improve the quality of the connection of a band-shaped carrier made of resilient, electrically conductive material with an electrically conductive contact layer.

Nearest prior art

From the US 7,592,566 B2 For example, a method for bonding a copper-based support to a silver-based contact layer by means of a laser welding process has been known. In this case, the laser weld seam is produced along the outer edge region of the contact layer in the region of the contact seam between the carrier and the contact layer. The irradiation angle of the laser is therefore inclined in the range of 5 ° to 20 ° with respect to the surface of the carrier. According to this method, a proportion of at least 70% of the melt produced by the laser beam should occur in the region of the carrier. This is procedurally extremely difficult to ensure. In addition, this method requires a lot of equipment. Incidentally, it is not suitable for thin contact layers.

From the DE 10 2009 013 110 A1 It will be understood by those skilled in the art that welding of Cu and Cu alloys with laser light is difficult because of their high reflectivity. To solve this problem, a laser welding structure and a laser welding method is proposed, in which a conductor is connected at its end-side end region with a conductive component via a punctiform weld. Both the conductor and the conductive member are provided with a nickel plating layer on both their upper and lower surfaces, which have a lower melting point and a lower laser reflectance than the conductor or the component itself. The nickel plating layer serves to accelerate the melting of the conductor or component. However, a corresponding nickel plating layer is disadvantageous in an electrical contact element of the type mentioned, since it increases the contact resistance.

From the GB 2 327 300 A is an electrical contact with a band-shaped carrier of resilient, electrically conductive CuBe known at the top of a silver wire by means of a plurality of arranged in the lateral contact region of the silver wire to the carrier on both sides laser welding points fixed. The laser welding points lie at an acute angle between the carrier and the contact wire. Again, the laser beam must be positioned laterally inclined. This method also requires a high expenditure on equipment.

Object of the present invention

The object of the present invention is to provide an electrical contact element with reduced contact resistance with simplified manufacture.

Solution of the task

The above object is achieved by an electrical contact element according to the features of claim 1. Advantageous embodiments of the invention are claimed in the subclaims.

The invention makes it possible, an electrical contact element with a band-shaped carrier made of a resilient, electrically conductive material of low thickness with a pad or pad-shaped electrically conductive contact layer also low strength, which is located on a flat side of the band-shaped carrier, on a simple apparatus and reliably connect. At the same time, a reduced contact resistance compared with the conventional method can be achieved. The laser beam is positioned perpendicular to the back of the carrier, radiating through the carrier and penetrates only in a slight, defined depth in the carrier-facing surface of the electrical contact material. The type of laser welding connection according to the invention is due to the large-area, but comparatively gentle, energy input into the contact layer that thin layers can be effectively connected to each other without an additional (such as a contact resistance increasing) welding aid, such as a Cu alloy.

Because the outer edge region of the band-shaped carrier and / or the contact layer remains laser-welded or laser-welding cone-free, the electrically conductive contact layer, in particular in the case of thin contact layers, remains unchanged in its starting geometry. It is advantageous that the upper contact surface remains undamaged. This results in improved contact properties.

By increasing the size ratio of the welded surface to the unwelded surface of the contact layer from the switching spring root to the switching spring end, an abrupt change in the spring properties of the band-shaped carrier and resulting disadvantages can be avoided. This manner of laser welding therefore results in a gradual change in the spring characteristics of the band-shaped carrier from the shift spring root to the shift spring end, such that the decreasing spring characteristic in that direction increases only gradually, but not abruptly. To achieve the planar laser welding connection, a plurality of elongate laser weld seams can be arranged, for example, running parallel to one another in the carrier.

Alternatively or additionally, the profile of the respective laser weld seam can also be circular, curved, rectangular and / or meander-shaped. This ensures a large-area bond with a comparatively low energy input and penetration depth of the melted area into the contact layer.

Alternatively, a surface pattern formed from a multiplicity of individual welding cones can be provided to ensure a laminar bond. This also makes possible a large-area connection with a comparatively low energy input as well as a reduced penetration depth of the welding cone into the contact layer.

According to an expedient embodiment, the laser welding seam or the laser welding cone extends from the band-shaped support in each case up to a maximum of only a quarter, preferably up to a maximum of only one fifth of the layer thickness H1 of the contact layer into the latter. This unusual, very slight welding entry is made possible by the large-area laser welding connection and at the same time leads to a sufficient real wear layer remaining in the contact layer, ie laser welding defects only on a very small layer area of the contact layer, i. Wear layer, remain limited.

Expediently, the laser welding seam or the laser welding cone extends from the band-shaped carrier, in each case up to a maximum of 0.08 mm, preferably up to a maximum of 0.06 mm, into the contact layer.

Due to the fact that the extrapolated cross-sectional contour of the laser weld seam or of the weld cone each has an opening angle of at least 60 °, preferably of at least 80 °, a sufficient hold is ensured with a very small penetration depth of the laser welding into the contact layer, nevertheless considered sufficient over the areal laser welding connection.

Conveniently, the thickness of the band-shaped carrier is in the range of 0.1 to 0.3 mm.

Conveniently, the thickness of the contact layer is in the range of 0.1 to 0.4 mm.

The electrically conductive material of the band-shaped carrier is expediently a Cu alloy, preferably a CuCoBe alloy or a CuBe alloy or a NiBe alloy.

Alternatively, according to the invention, the material of the band-shaped carrier can also be a metal provided with a conductive layer, for example a steel strip.

Conveniently, the belt-shaped carrier and the contact layer may be welded to each other in a planar manner without gap formation and without an intermediate layer serving as a welding aid (i.e., preferably without a Cu alloy). As a result, a particularly low contact resistance can be achieved.

According to an alternative embodiment, if required, a phosphor bronze layer can also be present between the strip-shaped carrier and the contact layer, which as an additional solder ensures a particularly intimate connection between carrier and contact layer. This phosphor bronze layer is particularly suitable in the case of a band-shaped support of a copper alloy or of a support of metal provided with a conductive layer (for example silver or a silver alloy).

Description of the invention with reference to embodiments

Advantageous embodiments of the present invention will be explained in more detail with reference to drawings. Show it:

1 a sectional view of a thermal temperature controller;

2 a sectional view of a thermal fuse;

3 an isolated view of the contact element 1 in plan view from above ( 3a ) and in section along the cutting plane AA 3a ( 3b );

4 a greatly enlarged sectional view through the band-shaped carrier and the contact layer of the contact element according to 3 ;

5 various possibilities of large-scale laser welding connections of band-shaped carrier and electrically conductive contact layer and

6 a greatly enlarged sectional view through the band-shaped carrier and the contact layer of the contact element, wherein an intermediate layer of phosphor bronze according to 3 ,

The reference number 7 in 1 shows a so-called thermal temperature controller with a housing 9 and two connectors located at the top of the housing 8th to connect the temperature controller to an electrical circuit. The in 1 left connector is with a switching spring 1 in the area of the so-called switch spring root 1a firmly connected and lies in the area of the switching spring end 16 with its opposite end to a mating contact 12 of the adjacent connector 8th in closed position of the temperature controller 7 at. The switching spring 1 is there with a contact layer 3 Mistake. The switching spring 1 is in the closed position by means of an actuating element 11 held, whose underside end turn with a bimetallic disc 10 communicates.

Provided that due to a change in temperature, the bimetallic disc 10 in 1 bulging downward, the actuator moves 11 also down and the contact is due to the self-bias of the switching spring 1 open.

Similarly, the in works 2 illustrated thermal fuse 13 , in place of the bimetallic disc 10 in 1 a melting pill 17 at the bottom of the actuator 11 is arranged. Unless the melting pill 17 Temperature is destroyed, this moves in the housing 15 located actuator 16 down and over the switching spring 1 held contact on the mating contact 12 of the connector 14 is due to the bias of the contact spring 1 open.

At the in 2 shown switching spring 1 is also a contact layer 3 intended.

It is desirable that the on the switching spring 1 arranged contact layer 3 has the lowest possible resistance. High resistances lead to increased temperature in the contact layer and thus often to premature destruction due to frequent during switching arc formation.

The 3a such as 3b show a corresponding switching spring 1 in isolated form, on the one hand in plan view ( 3a ) and on the other in a sectional view along the sectional plane AA in 3a ( 3b ). numeral 1a denotes the so-called switch spring root, reference numeral 1b the shift spring end. The switching spring comprises a band-shaped carrier 2 made of an elastic, electrically conductive material. In the material it is expediently a Cu alloy, preferably a CuCoBe alloy or a CuBe alloy. The band-shaped carrier 2 can also consist of a NiBe alloy. Alternatively, it may be in the material of the band-shaped carrier 2 also be a stainless steel strip which is provided with a conductive layer, for example an Ag layer or a layer of an Ag alloy. The layer thickness of the Ag layer is in the range of 0.01-0.1 mm. The thickness of the band-shaped carrier for both alternatives is in the range of up to a maximum of 0.5 mm, preferably in the range of 0.1-0.3 mm.

On the curved end of the switch spring 1 opposite end region is a surface limited contact layer 3 on the carrier 2 applied. In the 3a illustrated contact layer 3 has a pillow-shaped or pad-shaped form. The contact layer is a noble metal or noble metal alloy layer, preferably an Ag layer or an Ag alloy layer. Likewise, Au or Pt or an Au or Pt alloy comes into question.

The thickness of the contact layer is a maximum of 0.5 mm. It is preferably in a range of 0.1-0.4 mm.

The contact layer 3 is with the carrier 2 connected via a specially designed laser welding connection.

The 4 shows an enlarged partial sectional view of the connection area between the contact layer 3 and carriers 2 , The contact layer 3 lies flat, without gap bonding on the top of the carrier 2 on. The reference number 4 denotes a laser weld in cross section. The laser weld 4 extends over both the total thickness H2 of the carrier 2 as well as in a partial area H3 of the carrier 2 facing surface of the contact layer 3 into it. Here, the penetration depth H3 is chosen so that it only a maximum of a quarter of the total thickness H1 of the contact layer 3 , preferably one fifth of the total thickness H1 of the contact layer 3 , makes up. So it will be punctually in 4 considers only a minor input of energy, ie a minor melt entry, into the contact layer 3 causes.

Conveniently, the opening angle of the extrapolated cross-sectional contour of the weld 4 at least 60 °, preferably at least 80 °. This makes it possible to set the penetration depth H3 of the melt particularly slightly.

To produce the laser welding, a laser is irradiated in a direction perpendicular to the underside of the carrier 2 positioned as in 4 is shown schematically. In this way it is possible to laser weld the wearer 2 with the contact layer 3 in the aforementioned special materials without a welding aid, in particular without a Cu alloy perform. This results in the advantage that, on the one hand, the contact resistance between the contact layer 3 and carriers 2 can be minimized, on the other hand, a sufficient wear layer in the contact layer 3 remains and the welding process can still be done in a simple apparatus arrangement, also automated.

Conveniently, the outer edge region of the contact layer 3 free from a laser weld.

Although the penetration depth of the laser weld 4 , as in 4 shown, is extremely low, due to a large-area weld sufficient strength between the carrier 2 and contact layer 3 achieved.

The illustrations according to 5a - 5g show in each case different embodiments of a large-area laser welding connection in a plan view of the carrier 2 from underneath. The large-area laser welding connection can according to 5a from one over the area of the contact layer 3 large-scale extending number of laser welding seams running side by side 4 will be realized.

Likewise, a single laser weld 4 For example, in a meandering course over large areas of the contact layer 3 extend like this in 5b is shown.

Alternatively, different geometric figures, such as at least one, preferably a plurality of nested, rectangular laser welds 4 be provided ( 5c ).

Alternatively, a plurality of individual point-shaped laser welding cone 4a , as in 5d shown over the surface of the contact layer 3 extend.

Alternatively, the laser weld 4 at least in certain areas, even in the immediate vicinity of the outer edge of the contact layer 3 be arranged running, for example, in the immediate vicinity of the outer edge extending ( 5b such as 5e ) or in a circular or curved course ( 5f ).

At the in 5f such as 5g illustrated embodiments of the large-scale laser welding connection takes the ratio of the welded surface to the unwelded surface of the contact layer 3 from the shift spring root 1a facing side of the contact layer 3 to the shift spring end 1b facing side of the contact layer 3 to. This advantageously achieves that the spring properties of the band-shaped carrier 2 not abruptly, but only gradually, ie continuously change towards the switching spring end, by the spring characteristics of the shift spring root 1a to the spring end 1b decrease continuously. At the in 5f such as 5g shown types of welded joint are only examples. Of course, any other shapes can be chosen to the gradual change in the spring characteristics of the shift spring root 1a to the spring end 1b adjust.

It is important in each case that a large-area weld between the carrier 2 and the contact layer 3 with a very limited penetration into the contact layer 3 prevails.

According to an alternative embodiment, in the connection region of the carrier 2 and the contact layer 3 according to 6 a phosphor bronze layer 6 be provided, which acts as additional solder.

The present invention ensures a connection of a band-shaped elastic carrier to be carried out in an easy manner 2 of electrically conductive material having a contact layer thereon 3 also low strength without gap formation with reduced electrical resistance and without the need for a Cu alloy.

LIST OF REFERENCE NUMBERS

1

 switching spring

1a

 spring root

1b

 Switching spring end

2

 carrier

3

 contact layer

4

 laser weld

4a

 Laser weld nipples

5

 surface pattern

6

 Phosphor bronze layer

7

 thermostat

8th

 connector

9

 casing

10

 bimetal disc

11

 actuator

12

 countercontact

13

 fuse

14

 connector

15

 casing

16

 actuator

17

 melting pill

Claims (14)

Electrical contact element, in particular switching spring ( 1 ), preferably for a temperature controller or a thermal fuse, comprising a band-shaped carrier ( 2 ) made of a resilient, electrically conductive material, and an electrically conductive contact layer ( 3 ), which lie on a flat side of the band-shaped carrier ( 2 ) and connected to the latter, characterized in that the band-shaped carrier ( 2 ) and the contact layer ( 3 ) are connected to one another by means of a planar laser welding connection, the laser welding connection is a laser welding seam ( 4 ) or laser welding cone ( 4a ), each completely through the cross-sectional area of the band-shaped carrier ( 2 ) in a partial region of the cross-sectional area of the adjacent contact layer (FIG. 3 ) and, in order to achieve the areal laser welding connection, respectively along the surface of the band-shaped carrier ( 2 ) (a) a plurality of elongated laser welds ( 4 ), (b) a laser weld ( 4 ) is oriented in two dimensions and / or (c) a multiplicity of laser welding cones ( 4a ) are distributed flat. Contact element according to claim 1, characterized in that the outer edge region of the band-shaped carrier ( 2 ) and / or the contact layer ( 3 ) Laser welding seam or laser welding cone-free. Contact element according to claim 1 or 2, characterized in that the ratio of the welded surface to the unwelded surface of the contact layer ( 3 ) of the shift spring root ( 1a ) facing side of the contact layer ( 3 ) to the switching spring end ( 1b ) facing side of the contact layer ( 3 ) increases. Contact element according to at least one of the preceding claims, characterized in that the course of the laser weld seam ( 4 ) is circular, rectangular, web-shaped and / or meandering. Contact element according to at least one of the preceding claims, characterized in that as a planar laser welding connection one of a plurality of individual welding cone ( 4a ) formed surface pattern ( 5 ) is provided. Contact element according to at least one of the preceding claims, characterized in that the laser weld seam ( 4 ) or the laser welding cone ( 4a ) from the band-shaped carrier ( 2 ) starting in each case up to a maximum of one quarter, preferably up to a maximum of one fifth of the total height H of the contact layer ( 3 ) into the latter. Contact element according to at least one of the preceding claims, characterized in that the laser weld seam ( 4 ) or the laser welding cone ( 4a ) from the band-shaped carrier ( 2 ) starting in each case up to a maximum of 0.08 mm, preferably up to a maximum of 0.06 mm in the contact layer ( 3 ). Contact element according to at least one of the preceding claims, characterized in that the extrapolated cross-sectional contour of the laser weld seam ( 4 ) or the welding cone ( 4a ) each having an opening angle of at least 60 °, preferably of at least 80 °. Contact element according to at least one of the preceding claims, characterized in that the thickness of the band-shaped carrier ( 2 ) is in the range of 0.1-0.3 mm. Contact element according to at least one of the preceding claims, characterized in that the thickness of the contact layer ( 3 ) is in the range of 0.1-0.5 mm. Contact element according to at least one of the preceding claims, characterized in that it is in the material of the band-shaped carrier ( 2 ) is a Cu alloy, preferably a CuCoBe alloy or a CuBe alloy or a NiBe alloy. Contact element according to at least one of claims 1-10, characterized in that it is in the material of the band-shaped carrier ( 2 ) is a metal provided with a conductive layer. Contact element according to at least one of the preceding claims, characterized in that between the band-shaped carrier ( 2 ) and the contact layer ( 3 ) no intermediate layer, preferably no Cu alloy, is provided. Contact element according to at least one of the preceding claims 1-12, characterized in that between the band-shaped carrier ( 2 ) and the contact layer ( 3 ) a phosphor bronze layer ( 6 ) is provided.

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