Method for Working a First Component and a Second Component by Laser Welding and Corresponding Device

Abstract

A method for working a first component and a second component comprises the following steps: providing the first component, which comprises a thermally sprayed electrically conductive layer, providing the second component, which has a longitudinally extended strip of copper, which at least in a first region has a thickness transversely to the longitudinal direction of more than 0.1 millimeter, arranging the strip and the layer one on top of the other, so that the first region of the strip and the layer have a contact region in common with one another, emitting a laser beam onto the contact region and forming a welded connection, which connects the strip and the layer to one another.

Claims

1. A method for working a first component and a second component, comprising: providing the first component, which comprises a thermally sprayed electrically conductive layer, providing the second component, which has a longitudinally extended strip (104) of copper, which at least in a first region (112) has a thickness transversely to the longitudinal direction of more than 0.1 millimeter, arranging the strip and the layer one on top of the other, so that the first region of the strip and the layer have a contact region in common with one another, emitting a laser beam onto the contact region; and thereby forming a welded connection, which connects the strip and the layer to one another.

2. The method according to claim 1, in which the laser beam is emitted such that the geometrical form of the welded connection is formed as annular, linear, rectangular or circular.

3. The method according to claim 1, in which the laser beam is emitted with first laser parameters and is subsequently emitted with second laser parameters that are different from the first laser parameters and are prescribed such that the welded connection is formed.

4. The method according to claim 1, in which the laser beam is emitted obliquely.

5. The method according to claim 1, in which the laser beam is emitted onto the strip on a side that is facing away from the layer.

6. The method according to claim 5, wherein provision of the second component comprises the step of roughening the side of the strip that is facing away from the layer by means of the laser beam and/or chemically and/or mechanically.

7. The method according to claim 1, wherein the provision of the first component comprises the step of thermally spraying copper to form the electrically conductive layer.

8. The method according to claim 1, wherein the provision of the second component comprises the step of reducing the thickness in a welding region of the first region of the strip, and forming the welded connection in the welding region.

9. The method according to claim 8, wherein the step of reducing the thickness in the welding region comprises reducing to a prescribed second thickness transversely to the longitudinal direction, the second thickness being prescribed in dependence on a thickness of the thermally sprayed electrically conductive layer.

10. A device, comprising: a thermally sprayed electrically conductive layer, a strip of copper, which at least in a first region has a thickness transversely to the longitudinal direction of more than 0.1 millimeter, and a welded connection, which connects the layer and the first region of the strip to one another in order to form by means of the strip (104) an electrical and/or mechanical contact with respect to the layer.

11. The device according to claim 10, in which the strip has a second region outside the welded connection, the strip having in the second region a thickness transversely to the longitudinal direction that is greater than the thickness in the first region.

12. The device according to claim 10, in which the thermally sprayed electrically conductive layer comprises copper.

13. The device according to claim 10, in which: the strip has in a welding region of the first region a second thickness that is less than the thickness, and the welded connection is formed in the welding region.

14. The device according to claim 13, in which: the second thickness is prescribed in dependence on a thickness of the thermally sprayed electrically conductive layer.

15. The device according to claim 10, further comprising a heating conductor layer is arranged on the electrically conductive layer, a contour of the electrically conductive layer being prescribed to avoid a buildup of heat at the electrically conductive layer, by at least one of the following: a prescribed width of a front side of the electrically conductive layer that is facing a middle region of the heating conductor layer, a prescribed distance from an isolation groove of the heating conductor layer, and a prescribed curvature of the contour.

Description

[0033] In the figures:

[0034] FIG. 1 shows a schematic plan view of a device according to embodiments,

[0035] FIG. 2 shows a schematic representation of a sectional view of the device according to embodiments,

[0036] FIG. 3 shows a schematic representation of a sectional view of the device according to embodiments,

[0037] FIG. 4 shows a schematic representation of a sectional view of the device according to embodiments,

[0038] FIG. 5 shows a schematic plan view of a device according to embodiments,

[0039] FIG. 6 shows a schematic representation of a sectional view of the device according to embodiments, and

[0040] FIG. 7 shows a schematic representation of a sectional view of the device according to embodiments.

[0041] FIG. 1 shows a plan view of a device 100. The device 100 is in particular part of a heater for a motor vehicle. The heater is an electrical heater, which generates heat when a voltage is applied during operation.

[0042] The device 100 has a first component 101. The first component 101 has a stack of layers 116. The stack of layers 116 has a heating conductor layer on an insulation layer. The stack of layers may have further layers, such as for example intermediate layers between the heating conductor layer and the insulation layer.

[0043] On part of a surface 117 of the heating conductor layer, an electrically conductive layer 103 has been applied. The electrically conductive layer has been applied by means of a thermal spraying process, in particular by means of an atmospheric plasma spraying.

[0044] In particular, an arc is used, and an inert gas is passed through the arc. For example, compressed air is used. Copper powder is introduced and is melted as a result of the high plasma temperature. The stream of plasma entrains the powder particles and accelerates them onto the stack of layers 116. The electrically conductive layer 103 has for example a thickness 121 transversely to a longitudinal direction 106 of greater than 250 μm and less than 450 μm, for example 300 μm.

[0045] The electrically conductive layer 103 is formed from copper or comprises copper. For example, the electrically conductive layer comprises 99% copper. The copper has been applied to the stack of layers 116 by means of the thermal spraying process, so that there is an electrical connection between the electrically conductive layer 103 and the heating conductor layer. The electrically conductive layer 103 forms contact pads for the electrical and/or mechanical contacting of the stack of layers 116.

[0046] According to exemplary embodiments, the contour of the electrically conductive layer 103, in particular the outline in plan view of FIGS. 1 and 5, is prescribed such that current can be reliably introduced into the heating conductor layer during operation. The contour of the electrically conductive layer 103 is prescribed such that a uniform transport of current, and consequently a uniform heat distribution, are accomplished. This makes it possible to avoid buildups of heat (hot spots). According to embodiments, the width of the front edge or the front face of the electrically conductive layer 103 is prescribed such that a uniform transport of current, and consequently a uniform heat distribution, are accomplished. The front face or front edge is facing a middle region of the surface 117. Alternatively or additionally, the corners of the electrically conductive layer 103 are prescribed as rounded, in order to accomplish uniform transport of current, and consequently a uniform heat distribution. Alternatively or additionally, a distance from a neighboring isolation groove of the heating conductor layer is prescribed such that a uniform transport of current, and consequently a uniform heat distribution, are accomplished. The isolation groove serves in particular for dividing the heating conductor layer into conductor tracks. The prescribed contour of the contact pad that is formed by the electrically conductive layer 103 makes it possible to keep the temperatures at the contact pad so low during operation that reliable operation is accomplished in spite of a high flow of current.

[0047] Connected to the electrically conductive layer 103 in a material-bonded manner is a second component 102. The second component 102 has a strip 104 of copper. The strip 104 is for example formed from a copper alloy. The strip 104 of copper extends in an elongated manner along the longitudinal direction 106. The longitudinal direction 106 is for example that spatial direction along which the strip has its greatest extent.

[0048] During operation, two strips 104 and two layers 103 are provided. By means of the two strips 104, the device 100 can be connected to a current/voltage source. During operation, the two electrically conductive layers and the two strips 104 that are represented in FIG. 1 form for example the positive and negative terminals for the electrical voltage.

[0049] The strip 104 is respectively connected by means of a welded connection 109 to the electrically conductive layer 103. The welded connection 109 forms a mechanical and electrical connection between the strip 104 and the electrically conductive layer 103. The electrically conductive layer has a greater base area than the region of the strip 104 that is in contact with the electrically conductive layer 103. Consequently, during operation the temperature of the electrically conductive layer 103 is reduced in comparison with a contact layer of a size that corresponds substantially to the region of the strip 104 that is in contact with the electrically conductive layer.

[0050] In FIG. 1, the welded connection 109 is represented as circular. According to further embodiments, the welded connection has a different geometrical form, for example linear, rectangular and/or circular/punctiform. A mixture of different geometrical forms is also possible. In particular, according to embodiments, not just a single circle is provided for each welded connection 109, as represented in FIG. 1, but two or more welded connections spaced apart from and/or overlapping one another. For example, a lap fillet weld is provided as a welded seam arrangement.

[0051] FIG. 2 shows a sectional view of the device 100 during production. Formed on the surface 117 of the stack of layers 116 is the electrically conductive layer 103 of thermally sprayed-on copper. Placed on a surface 115 of the electrically conductive layer 103 that is facing away from the surface 117 is the strip 104. The strip 104 and the electrically conductive layer 103 consequently have in a first region 112 (FIG. 3) a common contact region 107. In the common contact region 107, the strip 104 and the electrically conductive layer 103 touch. The strip 104 and the electrically conductive layer 103 are placed one on top of the other as far as possible without any gaps. In the contact region 107, the copper of the strip 104 and the copper of the electrically conductive layer 103 are in direct contact with one another.

[0052] The strip 104 has a thickness 105 transversely to the longitudinal direction 106. The thickness 105 is chosen to be of such a size that a sufficiently great flow of current is possible during operation. For example, during operation a voltage of 100 V is applied to the strips 104 and there flows a current sufficiently great to make it possible for the device 100 to have a heating output sufficiently great for a motor vehicle. The thickness 105 is in particular greater than 0.1 mm and less than 0.6 mm. According to further embodiments, the thickness 105 is greater than 0.2 mm. According to further embodiments, the thickness 105 is greater than 0.3 mm. In particular, the thickness 105 is between 0.2 mm and 0.3 mm. According to further embodiments, the thickness 105 is between 0.4 mm and 0.6 mm. According to further embodiments, the thickness is greater than 0.5 mm, in particular greater than 1 mm. The thickness 105 is less than 5 mm, in particular less than 2 mm. The thickness 105 is chosen to be sufficiently thick to accomplish a sufficiently high current-carrying capacity. For example, the thickness 105 is chosen such that a current-carrying capacity of 25 A is accomplished.

[0053] A laser beam 108 is emitted by means of a laser 118 onto one side 111 of the strip 104. The side 111 is a surface that is facing away from the layer 103. The laser beam 108 is in particular emitted at an angle 110. The angle 110 is greater than 0°, in particular greater than 20°. The angle 100 is less than 90°, in particular less than 80°. The angle 110 is prescribed such that the laser beam 108 is coupled into the strip 104 as well as possible. The angle 110 is alternatively or additionally prescribed such that instances of damage to the laser caused by undesired reflections at the surface 111 are avoided.

[0054] According to embodiments, the laser 118 is a fiber laser. In particular, the laser 118 is an Nd:YAG laser (neodymium-doped yttrium-aluminum-garnet laser). According to further embodiments, a different laser is used.

[0055] In particular, the laser 118 is designed to produce the laser beams 108 with a wavelength of 532 nm. According to further embodiments, alternatively or additionally the laser beam 108 is produced with a wavelength of 1064 nm. For example, both a laser beam with a wavelength of 532 nm and a laser beam with a wavelength of 1064 nm are emitted. The laser beam with 532 nm couples into the strip 104 particularly well. The laser beam with 1064 nm has a high energy input into the strip 104. The laser power of the laser beam 108 is prescribed such that the strip 104 melts in a certain region. For example, a laser energy of 400 W is chosen. The laser energy is absorbed at the surface 111 of the strip 104, or in the interior of the strip 104, and is chosen to be of such an intensity that the material of the strip 104 at least partially melts in the region 112. The melting zone spreads in the direction of the layer 103 to the extent that the electrically conductive layer 103 is also melted. The layer 103 is melted at least in a region that directly adjoins the surface 114. The materials of the strip 104 and of the layer 103 mix in the melt. Subsequently, the melt solidifies to form the material-bonded welded connection 109 (FIG. 3).

[0056] According to further embodiments, the surface 111 is pretreated before the laser beam 108 for the welding is emitted. The pretreatment serves in particular for cleaning and/or roughening the surface 111. The cleaning has the effect for example of removing an oxide layer from the surface 111. The roughening of the surface has the effect of improving the coupling of the laser beam 108 into the strip 104. The roughening has the effect that the proportion of the laser beam 108 that is reflected at the surface 111 is reduced. The proportion of the laser beam 108 that penetrates into the interior of the strip 104, or is absorbed by the strip 104, is increased. By means of the roughening it is possible to set the reflectance of the surface 111 to a desired value. In particular, the reflectance is reduced in comparison with a non-roughened surface such that a higher heat input is made possible during the welding. As a result, the coupling-in behavior of the laser beam 108 is improved. The roughened surface 111 has the effect that the proportion of the energy of the laser beam 108 that is absorbed by the strip 104 is increased.

[0057] The pretreatment of the surface 111 is performed in particular by using the laser beam 108. For the pretreatment, the laser parameters for the laser beam 108 are set such that the laser beam 108 does not melt the material of the strip 104, but it is only that the surface 111 is roughened. For example, a pulsed laser is used. Moreover, a circular beam guidance is used for the pretreatment. Alternatively or additionally, the pretreatment is performed mechanically, for example by brushing. Alternatively or additionally, the pretreatment is performed chemically, for example by a superficial etching of the surface 111.

[0058] According to further embodiments, for the pretreatment before the welding, the strip 104 is alternatively or additionally preheated at least in the region 112. For the preheating, in particular the laser beam 108 is used with correspondingly prescribed laser parameters. The preheating has the effect for example of further improving the coupling of the laser beam 108 into the strip 104 during the welding.

[0059] Different laser parameters for the laser beam 108 are prescribed for the welding than for the pretreatment. For example, a continuous-wave laser beam 108 is used for the welding. For example, a top-hat (cylinder shape) and/or rectangular fiber is used as the grade of beam. The grade of beam or the beam profile is prescribed such that the material of the strip 104 is melted, in particular for example without any material being removed by burning. In particular, a comparatively small melting zone is formed and comparatively short melting times are prescribed. As a result, a welding of the strip 104 and of the layer 103 that respectively comprise copper is possible. It is possible in this case to dispense with filler materials. For example, the number and form of the welded connections 109 is chosen such that they correspond to an analogous wire cross section of 2.4 mm.sup.2. This makes it possible to apply the strip 104 of copper on the thermally sprayed copper layer 103. A current-carrying capacity of 25 A is in this case ensured.

[0060] FIG. 4 shows the device 100 according to further embodiments. The device 100 corresponds substantially to the exemplary embodiments as explained in conjunction with FIGS. 1 to 3. As a difference, the strip 104 has in a second region 113 a second thickness 114. The second thickness 114 is greater than the thickness 105. The second region 113 is different from the first region 112 and is arranged outside the contact region 107. The thickness in the region 112, in which the strip 104 is welded to the layer 103, is smaller than the thickness 114 in the region 113, which is facing the current/voltage source during operation. This makes it possible to accomplish a welded connection 109 that is as good as possible in the region 112. At the same time, a current-carrying capacity that is as good as possible is accomplished in the region 113.

[0061] FIGS. 4 to 7 show the device 100 according to further embodiments. The device 100 corresponds substantially to the exemplary embodiments as explained in conjunction with FIGS. 1 to 3. As a difference, the strip 104 has in the first region 112 a welding region 119. The welding region 119 has a thickness 120 transversely to the longitudinal direction 106. The thickness 120 is smaller than the thickness 105. Outside the welding region 119, the strip 104 has in the first region 112 the thickness 105, which is greater than 0.1 millimeter.

[0062] The thickness 105 is reduced to the thickness 120 for example by a stamping method and/or a rolling method and/or a milling method and/or a grinding method and/or a pressing method. Some other method that is suitable for reducing the thickness may also be used.

[0063] The thickness 105 is chosen such that a good current-carrying capacity and a good thermal conductivity are accomplished. The region of the device 100 of the layer 103 is not heated during operation. The region of the device 100 of the layer 103 is in particular cooled by the medium flowing under this region. As a result of this cooling, in this region the smaller thickness 120 is sufficient for the load currents occurring. In the other regions, in particular outside the welding region 119, the thickness 105 is greater than in the welding region 119, in order to ensure sufficient removal of heat for the load currents occurring.

[0064] The welded connection 109 is consequently formed at the welding region 119 with the smaller thickness 120. As a result, it is possible to operate the laser beam 108 with a lower energy requirement. Welds that are too deep and damage the layer 103 can consequently be avoided. As a result, it is possible to reduce the number of reject parts during production.

[0065] The thickness 120 is in particular prescribed in dependence on the thickness 121 of the layer 103 transversely to the longitudinal direction 106. The greater the thickness 121 is, the greater for example the maximum value for the thickness 120 is prescribed. The smaller the thickness 121 is, the smaller for example the maximum value for the thickness 120 is prescribed. In particular, the thickness 120 is less than or equal to the thickness 121 of the layer 103. The thickness 121 is for example greater than 50 micrometers and less than 450 micrometers, in particular 200 micrometers or 300 micrometers.

[0066] The strip 104 consequently has at least two different thicknesses 105 and 120. As a result, the strip 104 has a sufficient removal of heat and is reliably weldable.

[0067] A combination is also possible with the exemplary embodiment of FIG. 4, in which the second region 113 has the greater thickness 114 than the first region 112 and the first region 112 has the welding region, which has the reduced thickness 120.

[0068] The strip 104 of copper according to the exemplary embodiments of FIGS. 1 to 7 has a sufficiently high current-carrying capacity to be used as a contact for a heater in a motor vehicle. The welded connection of the strip 104 to the layer 103 provides a gas-impermeable and moisture-resistant material-bonded connection. In this case, the porous material of the layer 103 is covered by the solid material of the strip 104 and/or the material-bonded connection 109. Short welding times in the range of milliseconds are possible for the forming of the welded connection 109. Consequently, a connection of the strip 104 to the layer 103 is reliably possible and undesired influencing of the stack of layers 101, for example damage, is avoided. A reliable connection between the strip 104 and the layer 103 over the service life of the device is made possible by the welded connection 109.