Manufacturing method of a housing for an electronic device

Description

[0001] The invention is based on a method for producing a housing for electronics and an electronics housing according to the invention. State of the art

[0002] A method for manufacturing a housing for electronics, comprising a first housing element and a second housing element, is already known. The known methods for manufacturing a housing connect the housing elements by means of a screw connection. Sealing is achieved by a gasket arranged between the first and second housing elements. Manufacturing requires a large number of process steps, which in turn results in increased manufacturing costs.

[0003] It is also known to join the housing elements using single-layer laser beam welding. However, this process is prone to welding defects, which can result in a lack of tightness of the housing. Welding defects of the type discussed here can have a variety of causes. Welding aluminum die-cast alloys in particular presents particular challenges. For example, air inclusions in the material, which are opened during laser welding, can cause penetrations in the weld seam. Furthermore, hydrogen inclusions and alloying elements can be released during the laser beam welding process and form pores in the weld seam.

[0004] DE 10 2014 222006 A1 discloses a method for producing a housing for electronics, wherein the housing elements of the housing are welded together. EP 2 768 295 A2 discloses a housing comprising a first housing element and a second housing element, wherein the housing elements can be connected using a joining process.

[0005] EP 1 087 134 A2 discloses a method for producing a housing, wherein the housing is formed by a first housing element and a second housing element. The housing elements comprise aluminum or an aluminum alloy, and at least one of the housing elements is manufactured by a die-casting process. The housing elements are at least partially joined by multi-layer laser welding, in particular two-layer laser welding.

[0006] Further prior art has become known from EP 1 647 350 A2, WO 2018 / 072163 A1 and DE 10 2016 115437 A1. Disclosure of the invention Advantages of the invention

[0007] The invention is based on a method for producing a housing, in particular a housing for electronics, in particular for controlling an electric motor. The housing is formed by a first housing element and a second housing element, the housing elements comprising aluminum or an aluminum alloy, and at least one of the housing elements is produced by a die-casting process. It is proposed that the housing elements be at least partially connected to one another in a fluid-tight manner by means of multi-layer laser welding, in particular two-layer laser welding.

[0008] The inventive method for producing a housing and the electronics housing produced by such a method with the features of the independent claims have the advantage that a cost-effective and simultaneously fluid-tight connection can be provided between the housing elements. Such a multi-layer laser weld seam can advantageously increase the tightness. Meanwhile, the electronics arranged in the housing are minimally affected by the narrow heat-affected zone of the laser beam welding. The setting of the additional weld seam layers can be carried out particularly advantageously and flexibly in the areas of the first weld seam layer in which a leak is detected or suspected. In this way, assembly times and thus the associated component costs can be further reduced.

[0009] If the melt, or the liquid aluminum or the liquid aluminum alloy comes into contact with moisture or water from the air on the surface, this can lead to malformations, pores or gas inclusions. The water from the air reacts with the liquid aluminum to form aluminum oxide and hydrogen. The hydrogen dissolves in the melt. Hydrogen is highly soluble in liquid aluminum. When the aluminum melt solidifies, the solubility of the hydrogen decreases dramatically, and hydrogen-filled pores can form in the structure. These hydrogen inclusions can be released during laser welding of the first weld layer and thus cause openings and pores in the weld itself, which can be advantageously closed with the subsequent weld layer, thus creating a fluid-tight electronics compartment in the housing.

[0010] Released air pockets, the outgassing of alloying elements from the structure, hydrogen deposits in the oxide layer on the surface of the housing elements, and oils and greases remaining on the surface from the casting process of the die-casting alloy can also lead to a lack of tightness in a first weld layer when joining aluminum housing elements. As already explained, these welding defects can be closed with one or more additional laser weld layers arranged on the first laser weld layer, thus creating a fluid-tight connection between the housing elements. Depending on the desired laser weld quality, it can also be provided that after the introduction of a second laser weld layer, one or more further weld layers are applied to the second weld layer.

[0011] The at least partial multi-layer laser welding of the housing elements thus advantageously enables the creation of a precise, narrow laser weld seam, which is, in particular, essentially pore-free. At the same time, the comparatively low heat input of multi-layer laser welding compared to other welding processes advantageously minimizes or prevents unwanted thermal influences on the electronics. Joining the housing elements using multi-layer laser welding also represents a particularly simple and cost-effective method for fluid-tight connections with minimal thermal influences on the electronics arranged in the housing.

[0012] In the context of the present invention, a die-casting process can be understood as a casting process in which the melt is pressed into a permanent mold under high pressure, with the pressure preferably being maintained during solidification. The housing element produced by the die-casting process is made of aluminum, in particular an aluminum alloy, preferably AlSi12(Fe), alloy 230.

[0013] The measures listed in the subclaims result in advantageous developments and improvements of the features specified in the main claim.

[0014] According to an advantageous development of the invention, it is further provided that at least one weld seam layer of the multi-layer laser beam welding is carried out by means of beam oscillation. The beam oscillation and the associated repeated movement over already molten material can advantageously effectively reduce pores in the weld seam, resulting in a high surface quality of the multi-layer laser weld seam. By superimposing the laser welding feed movement with a circular oscillation trajectory, the local energy input can be improved such that a particularly tight and, as far as possible, defect-free connection can be provided between the housing elements. In addition to such a circular oscillation trajectory, it is also conceivable for the beam oscillation to follow a substantially sinusoidal curve.Other laser beam trajectories, such as elliptical, traverse-eight, or longitudinal-eight beam oscillation patterns, are also conceivable. Beam oscillation allows for targeted adjustment of the local heat input and, consequently, weld seam parameters such as weld width and weld depth.

[0015] In the context of the present invention, a beam oscillation of the laser beam is understood to mean a superposition of the feed movement with a generally harmonic oscillation with a fixed amplitude in one or more spatial directions.

[0016] According to a particularly advantageous embodiment of the invention, the multi-layer weld seam, which is formed from at least one first weld seam layer and at least one second weld seam layer, is essentially pore-free in the region of the weld seam layer facing the free surface of the multi-layer weld seam, in particular in the region of the second weld seam layer. Furthermore, the number of pores and inclusions is significantly reduced compared to a single laser weld seam layer, whereby the term "significantly" can preferably be understood to mean a reduction of at least half, particularly preferably by more than 80%, of the pores or inclusions.

[0017] A preferred embodiment of the invention further provides that the ratio between the feed rate of the laser beam in [mm / s] and the superimposed beam oscillation of the laser beam in [Hz] is between 0.2 (mm / s) / Hz and 0.4 (mm / s) / Hz, in particular substantially between 0.25 (mm / s) / Hz and 0.35 (mm / s) / Hz. Such a ratio enables optimal, local heat input, which, due to the varying path speed in a circular oscillation trajectory, depends crucially on the ratio between the feed rate and the beam oscillation frequency. In this way, a high-quality, fluid-tight laser weld seam with an optimized microstructure can be provided.In particular, with a feed rate to beam oscillation ratio in the range between 0.25 (mm / s) / Hz and 0.35 (mm / s) / Hz, it can be ensured that a sufficient superposition of two consecutive oscillations is provided to produce such an optimized microstructure.

[0018] According to an advantageous embodiment of the invention, it can further be provided that the width of the weld seam of the first weld seam layer is smaller than the width of the weld seam of the second weld seam layer and / or that the depth of the weld seam of the first weld seam layer is greater than the depth of the weld seam of the second weld seam layer. In this way, it can be ensured that the second weld seam layer completely covers the free surface of the first weld seam layer and thus the tightness against fluids or liquids penetrating into the housing can be ensured. Such an adjustment of the widths and depths of the weld seam layers can be provided in particular by carrying out the laser beam method by means of beam oscillation, in particular circular beam oscillation.

[0019] An advantageous development of the invention provides that the weld seam is designed as a multi-layer laser weld seam only in regions in which the laser weld seam path is angular. In this way, the repeated traversal of the first weld seam can be reduced to regions in which welding defects are more likely to occur. In this way, production costs can be advantageously reduced. In this context, an angular weld seam path is preferably understood to mean a path which requires a change in the direction of advance of the laser head of more than 45°. Particularly preferably, the weld seam is designed as a multi-layer laser weld seam in regions in which the weld seam path essentially follows an S-shaped curve.

[0020] A fluid-tight connection of the housing elements with simultaneous minimal influence on the electronics arranged in the housing can be achieved in particular by making the radius of the substantially circular laser beam trajectory of the second weld seam layer larger, in particular between 20% and 40% larger, preferably between 30% and 35% larger, than the radius of the substantially circular laser beam trajectory of the first weld seam layer. Such a weld seam shape enables reliable overlap of the first weld seam layer with the second weld seam layer, thus minimizing the susceptibility to defects of the multiple weld seam while simultaneously providing a narrow weld seam.

[0021] According to an advantageous embodiment of the invention, the second housing element is designed as a cover for the first housing element, wherein the first housing element has a recess that is covered by the second housing element. In this way, by connecting the two housing elements using the laser beam method or multi-layer laser beam method according to the invention, a sealed housing interior for the electronics can be provided without additional housing parts or additionally introduced materials. For this purpose, the second housing element designed as a cover preferably rests against the first housing element in a substantially gap-free contact prior to the multi-layer laser beam welding.

[0022] An advantageous embodiment of the invention provides that the first housing element and the second housing element are arranged at an angled joint, in particular a flanged joint, relative to one another. Furthermore, it is provided that the multi-layer laser weld seam is designed as a flat end weld. Such a flanged joint can be provided in particular by the second housing element designed as a cover projecting beyond the contour of the first housing element in the direction of laser beam extension, wherein the cover is essentially trough-shaped. The projecting cover edge of the angled, sheet-metal-shaped cover (flange) can advantageously be used as weld metal and melted during laser beam welding.

[0023] A further advantageous embodiment of the invention provides that the second weld seam layer is formed as a weld seam with unequal legs, wherein the long leg of the weld seam faces the housing element produced by the through-casting process. Particularly in the case of a cover formed from a wrought alloy, weld seam defects such as pores and holes preferably occur in the region of the housing element produced by the die-casting process. An increased overlap of the first weld seam layer with the corresponding second weld seam layer in the region of the housing element produced by the die-casting process advantageously enables increased bonding in areas with a higher probability of weld defects occurring.

[0024] It is particularly advantageous that at least one housing element is produced by means of a forming process. A housing element is advantageously formed by deep drawing. The starting material for producing the housing element by deep drawing is a wrought alloy, in particular a defect-free and pore-free one. Deep drawing according to the process allows the production of a defect-free, in particular pore-free, thin-walled, lightweight housing element. A further advantage is that deep drawing is a simple and cost-effective process for producing a housing element. The housing element deep-drawn from a wrought alloy preferably comprises aluminum, in particular an aluminum alloy, preferably AlMg3 or AlSi1.2Mg0.4. It is advantageous that the copper content of the alloys is low, in particular less than 0.3%. The use of other aluminum alloys is also possible.

[0025] Preferably, the housing element produced by the die-casting process is made from a melt that has been degassed, in particular sufficiently, before being introduced into a die-casting mold, wherein the die-casting process is carried out in a protective atmosphere, in particular a nitrogen atmosphere. Degassing the melt prevents the melt from reacting during the casting process, for example, with other gases or with gases escaping from the melt. The combination of degassed melt and carrying out the die-casting process in a nitrogen atmosphere can reduce deformations, gas inclusions, or pores even before multi-layer laser welding.

[0026] According to an advantageous embodiment of the invention, the electronics are arranged in one of the housing elements prior to multi-layer laser welding. Preferably, the electronics are arranged centrally within the recess of the first housing element, so that a maximum distance between the electronics and the heat-affected zone of the laser weld seam can be provided.

[0027] Preferably, a solid-state laser, in particular an Nd:YAG laser, preferably with a power between 1800W and 2000W, is used for multi-layer laser beam welding.

[0028] Exemplary embodiments are illustrated in the figures and explained in more detail in the following description. They show: Figure 1 is an exploded view of a housing before joining, Figure 2a is a sectional view of an embodiment of the housing from Figure 1 before multi-layer laser beam welding, Figure 2b shows a sectional view of an embodiment of the housing made of Figure 1after multi-layer laser welding,

[0029] In Figure 1 is an exploded view of a housing 10 according to the invention. The housing 10 comprises a first housing element 12 and a second housing element 14. Figure 1 The housing 10 shown is suitable for accommodating electronics 18 for controlling an electric motor. However, it should be expressly mentioned at this point that applications for such a housing 10 are also conceivable, insofar as a fluid-tight housing interior is required for these applications. As shown in Figure 1As can be clearly seen, the first housing element 12 has a recess 16 within which the electronics 18 are arranged in the assembled state. Corresponding to the contour of the electronics 18, the recess 16 has a substantially rectangular shape. According to the invention, the housing elements 12, 14 comprise aluminum or an aluminum alloy, and at least one of the housing elements 12, 14 is manufactured by means of a die-casting process.

[0030] As in Figure 1As can be seen, according to the embodiment of the invention shown here, the first housing element 12 is produced by means of a die-casting process and has a large number of cooling fins 20 on its surface. The heat generated during operation of the electronics 18 can be dissipated by means of the cooling fins 20. The heat is passed from the electronics 18 to the housing 10. The heat is dissipated from the housing 10 by means of convection via the surface of the housing 10 and the surface of the cooling fins 20. For this purpose, the housing 10 is advantageously arranged in a moving air stream. Preferably, the housing 10 is arranged in an air stream of a fan which is driven by an electric motor, wherein, as already explained at the beginning, the electric motor is controlled by the electronics 18.

[0031] As in Figure 1As can be clearly seen, the second housing element 14 is designed as a cover, which during assembly, after the electronics 18 have been inserted into the recess 16 of the first housing element 12, is arranged on the recess 16 and completely covers it. The electronics compartment remains between the first housing element 12 and the second housing element 14 in the assembled state. Such a cover can be produced according to a preferred embodiment of the invention by deep drawing a wrought alloy. Figure 1 The lid 14 shown has a substantially rectangular, flat contour, wherein the lid edge 24 is bent circumferentially by substantially 90°, so that the lid 14 has a substantially tub-shaped form.

[0032] As in Figure 1As can be seen, the first housing element 12 has a circumferential casing 26. On or in a recess 28 of the casing 26, for example, a connector plug is arranged for controlling and / or supplying power to the electronics 18 or for controlling and / or supplying power to the motor. The electronics 18 is arranged in the electronics compartment before the second housing element 14 is placed on the first housing element 12 and, in particular, is fixed there. According to a further embodiment of the invention, the electronics 18 is fixed in the housing 10 by fixing elements, in particular contact points, preferably stops on the housing elements 12, 14. Subsequently, the two housing elements 12, 14 are laser-welded completely circumferentially along the extension of the housing edge 24 in a first welding layer. As in Figure 1As can be clearly seen, the second housing element 14 and the laser weld seam path following the housing edge 24 has a section 26 in which the laser has to change its feed direction twice by approximately 90° in order to follow the curvature of the cover edge 24. In this section 26, the welding defects explained at the outset occur more frequently in the first weld seam layer, which can lead to inadequate sealing of the electronics compartment. According to the invention, it is now provided that by passing over the first weld seam layer again, at least one further weld seam layer is applied to the first weld seam layer. The application of the further weld seam layer or weld seam layers preferably takes place in section 26 or in other sections 27 in which the laser feed direction has to be changed by approximately 90° in order to set the corresponding weld seam.

[0033] The multi-layer laser weld creates a metallic connection between the two housing elements 12, 14, which enables good heat conduction between the two housing elements 12, 14 and thus effective heat dissipation of the housing 10 and the electronics 18. In contrast, a wet seal as known from the prior art prevents or minimizes the formation of a heat flow between the housing elements 12, 14, so that heat exchange can only occur to a limited extent. The direct and circumferential metallic contact between the two joining partners 12, 14 also creates a positive electrical connection for the electronics 18. This can, for example, improve electromagnetic compatibility. This is particularly important if the electronics 18 is to be protected from electromagnetic fields or radiation from the motor, or if the environment is to be protected from electromagnetic radiation or fields from the electronics 18.

[0034] Figure 2a shows a section of a housing 10 according to a first embodiment in a sectional view before multi-layer laser welding. According to the Figure 2a In the illustrated embodiment of the invention, the two housing elements 12, 14 are arranged in a flanged joint with respect to one another. For this purpose, the second housing element 14 has a housing edge 24, which is bent substantially 90° from the plane of extension of the second housing element 14. However, it should be expressly mentioned at this point that other embodiments are also conceivable; for example, it is also conceivable for the two housing elements 12, 14 to be arranged in a corner joint with respect to one another.

[0035] The first housing element 12 has an internally arranged recess 16, which is designed in particular as a step in the edge of the casing 26 of the first housing element 12. The step forms both an axial and a radial stop for the inserted cover element 14. According to an advantageous development of the invention, the radial height 30 of the step 32 is essentially constant around its circumference. An advantageous development of the invention further provides that the circumferential housing edge 24 of the second housing element 14 has a radial height 36, which is preferably greater than the radial height 30 of the step 32, so that the housing edge 24, when inserted, protrudes beyond the contour of the first housing element 12 in the laser beam extension direction 34 or in the radial direction. The overhang 38 can advantageously be melted during laser beam welding and function as an additional welding agent.

[0036] As already mentioned at the beginning, the housing elements 12, 14 are made of aluminum or an aluminum alloy, with at least one of the two housing elements 12, 14 being produced using the die-casting process. The die-casting process is a primary forming process, i.e. a solid body is produced from a liquid starting material, in particular a melt. For this purpose, aluminum alloys, in particular those with a high melting point, are used, which are injected under high pressure into a dimensionally accurate, reusable mold, in particular a steel mold, in order to completely fill the casting mold. The hardened casting takes on the details and shape of the mold cavity of the casting mold with high precision. The advantage of die casting lies in the high degree of design freedom. A housing element 12, 14 for a housing 10 of an electronics unit 18 places high demands on thermal conduction and tightness.In particular, the die-casting process allows the formation of cooling fins and an optimal adaptation of the geometry of the housing interior to the electronics 18 located there.

[0037] Due to the die-casting process used to manufacture the housing elements 12, 14, defects and gas inclusions, which lead to pores, cannot generally be avoided. These misalignments lead to leaks during welding in the first weld seam layer, which prevent complete sealing of the housing 10. As already mentioned, such welding defects occur more frequently in regions 26, 27 in which the laser weld seam path is angular. An advantageous embodiment of the invention now provides that a multi-layer weld seam 40 according to the invention is arranged in these regions 26, 27. Such a multi-layer weld seam 40 is shown in Figure 2b shown.

[0038] As in the Figures 2a and 2bAs can be seen, in the multi-layer laser beam welding according to the invention, the laser beam is preferably guided centrally between the two housing elements 12, 14, wherein the laser beam extension direction 34 extends substantially in the radial direction of the housing 10. According to the invention, it is now provided that in a first method step, a first weld seam layer 42 is applied by means of laser beam welding. According to an advantageous embodiment of the invention, the first weld seam layer 42 can be applied by means of beam oscillation of the laser beam of the type described above. Subsequently, a second weld seam layer 44 is applied to the first weld seam layer 42. By setting the second weld seam layer 44, welding defects such as pores and inclusions in the first weld seam layer 42 can be closed in an advantageous manner.

[0039] The width 48 of the weld seam of the first weld seam layer 42 is according to the Figure 2b In the embodiment shown, the width 46 of the weld seam of the second weld seam layer 44 is smaller than the width 46 of the weld seam. In this way, it can be ensured that in the corresponding regions 26, 27, the entire first weld seam layer 42 is covered by the second weld seam layer 44, thus improving the tightness of the housing. According to an advantageous development of the invention, it is additionally or alternatively provided that the depth 50 of the first weld seam layer 42 is greater than the depth 52 of the second weld seam layer 44.

Claims

1. Method for producing a housing (10) for electronics (18), in particular for controlling an electric motor, wherein the housing (10) is formed by a first housing element (12) and a second housing element (14), wherein the housing elements (12, 14) comprise aluminium or an aluminium alloy, and at least one of the housing elements (12, 14) is produced by means of a diecasting process, wherein the housing elements (12, 14) are at least partly connected to one another in a fluid-tight manner by means of multilayer laser beam welding, wherein a multilayer weld seam (40) of the multilayer laser beam welding is made up of at least a first weld-seam layer (42) and at least a second weld-seam layer (44), wherein the second weld-seam layer is applied on top of the first weld-seam layer, characterized in that the width (48) of the first weld-seam layer (42) is made to be less than the width of the second weld-seam layer (44).

2. Method for producing a housing (10) according to Claim 1, wherein at least one weld-seam layer (42, 44) of the at least a first weld seam layer (42) and at least a second weld-seam layer (44) is created by means of beam oscillation, in particular by means of a substantially circular laser beam trajectory.

3. Method for producing a housing (10) according to one of the preceding claims, wherein the multilayer weld seam (40) is formed as substantially pore-free in the region of a weld-seam layer (42, 44) facing a free surface of the multilayer weld seam (40).

4. Method for producing a housing (10) according to either of Claims 2 and 3, wherein a ratio between a feed rate of the laser beam and the beam oscillation of the laser beam is made to be between 0.2 (mm / s) / Hz and 0.4 (mm / s) / Hz, in particular substantially between 0.25 (mm / s) / Hz and 0.35 (mm / s) / Hz.

5. Method for producing a housing (10) according to one of the preceding claims, wherein the depth (50) of the first weld-seam layer (42) is made to be greater than the depth (52) of the second weld-seam layer (44).

6. Method for producing a housing (10) according to one of the preceding claims, wherein the multilayer weld seam (40) is formed in regions (62, 27) in which the laser weld-seam follows a sharply angled course.

7. Method for producing a housing (10) according to one of the preceding claims when dependent on Claim 2, wherein the at least a first weld-seam layer (42) and the at least a second weld-seam layer (44) are created by means of a substantially circular laser beam trajectory, wherein the radius of the substantially circular laser beam trajectory of the second weld-seam layer (44) is made to be greater, in particular between 20% and 40% greater, 30% and 35% greater, than the radius of the substantially circular laser beam trajectory of the first weld-seam layer (42).

8. Method for producing a housing (10) according to one of the preceding claims, wherein the second housing element (14) is formed as a cover for the first housing element (12), wherein the first housing element (12) has a recess (16), which is covered by the second housing element (14).

9. Method for producing a housing (10) according to one of the preceding claims, wherein the first housing element (12) and the second housing element (14) are arranged in relation to one another in the laser beam region with an angular joint, in particular a flanged joint.

10. Method for producing a housing (10) according to one of the preceding claims when dependent on Claim 8, wherein the second housing element (14), formed as a cover, protrudes in the direction of extent (34) of the laser beam in a projection (38) beyond the contour of the first housing element (12), wherein the cover is substantially of a pan-shaped form.

11. Method for producing a housing (10) according to one of the preceding claims, wherein the second weld-seam layer (44) is formed as a weld seam with unequal legs, wherein the long leg of the second weld-seam layer (44) is formed facing the housing element (12, 14) produced by means of a diecasting process.

12. Method for producing a housing (10) according to one of the preceding claims, wherein the second housing element (14) is created by means of forming, in particular by the deep drawing of a wrought alloy.

13. Method for producing a housing (10) according to one of the preceding claims, wherein the housing element (12, 14) produced by means of a diecasting process is produced from a melt which has been degassed, in particular sufficiently degassed, before being introduced into a diecasting mould, wherein the diecasting process is performed in a protective atmosphere, in particular a nitrogen atmosphere.

14. Method for producing a housing (10) according to one of the preceding claims, wherein the electronics are arranged in one of the housing elements (12, 14) before the multilayer laser beam welding.

15. Method for producing a housing (10) according to one of the preceding claims, wherein a solid-state laser, in particular an Nd:YAG laser, is used for the laser beam welding.

16. Electronics housing produced by a method according to one or more of the preceding claims, wherein the electronics housing has at least a first housing element (12) and a second housing element (14), wherein the housing elements (12, 14) comprise aluminium or an aluminium alloy, and at least one of the housing elements (12, 14) is produced by means of a diecasting process, and wherein the housing elements (12, 14) are connected to one another in a fluid-tight manner by means of laser welding and between the first housing element (12) and the second housing element (14) at least partly a multilayer weld seam layer (40) is formed, wherein a multilayer weld seam (40) of the multilayer laser beam welding is made up of at least a first weld-seam layer and at least a second weld-seam layer, wherein the second weld-seam layer is applied on top of the first weld-seam layer, and wherein the width (48) of the first weld-seam layer (42) is made to be less than the width (46) of the second weld-seam layer (44).