Method for forming a laser weld joint and assembly with a laser weld joint

Abstract

The invention relates to a method for forming a laser weld joint (1) between two components (12, 14), wherein at least one of the components (12, 14) is designed to absorb radiation in a joining area (20) of the components (12, 14) for the wavelength (λ) of the laser steel (LS) used of a laser beam source (100), and wherein the components (12, 14) are covered on the side facing an incident direction of the laser beam (LS) onto the components (12, 14) by a further component (16).

Description

Technical field

[0001] The invention relates to a method for forming a laser weld between two components, characterized by the possibility of forming the laser weld even in connection areas of the components that are not freely accessible or are covered by another component when viewed in the direction of the laser beam. Furthermore, the invention relates to an assembly comprising a laser weld formed according to the invention. State of the art

[0002] A method for forming a laser weld between two components with the features of the preamble of claim 1 is known in various forms from the prior art. For example, laser welds are known in which both components are made of plastic, wherein a first component is made of a material transparent to the wavelength of the laser radiation, and a second component is made of a material absorbing the wavelength of the laser radiation. The adsorption capacity for the wavelength of the laser beam used can be adjusted by suitable additives, as is known from the applicant's generic DE 10 2010 029 978 A1.If the laser beam is now introduced through the first component into the second component, a laser weld is created at the joining point between the two components, since the material of the second component is heated above its melting temperature as a result of the adsorption of the laser beam and thus the material of the first component also melts in the area of ​​the joining point through heat transfer.

[0003] Other laser welding processes are known in which at least one component is made of metal and the other component of metal or plastic, with the joint being formed in the form of a fillet weld. Such a generic process is known from DE 10 2015 225 047 A1 of the applicant.

[0004] Both of the aforementioned applications share the common feature that the joints between the components are freely accessible to the laser beam. This means that, viewed in the direction of the laser beam, no other components are positioned between the components or the joint and the laser beam. However, there are applications where a laser weld is only created once the components are already arranged, for example, within a housing. In these cases, it is essential that the joint is freely accessible to the laser beam source or the laser beam itself. If this is not the case, openings or similar features must be provided in the housing surrounding the components to allow direct laser beam penetration to the joint area. These openings or similar features must then be subsequently sealed or closed, resulting in additional material, handling, and therefore cost expenditure. Disclosure of the invention

[0005] The inventive method for forming a laser weld between two components with the features of claim 1 has the advantage that the laser weld between the two components can also be formed in a state in which the components are arranged in a way that obscures the effect of the laser beam on the laser weld in the area to be formed by another or a further component. This is particularly relevant for applications in which the joining area between the two components is arranged in the area of ​​a housing that covers the joining area of ​​the components on the side facing the direction of the laser beam.

[0006] The invention is based on the idea of ​​enabling the laser beam to act in the area of ​​the joining point between the two components by making the additional component covering or protecting the joining point from a material that is transparent to the wavelength of the laser beam. This allows the laser beam to pass through the additional component in the direction of the joining area of ​​the two components without the additional component being excessively heated or damaged.

[0007] In light of the above explanations, a method according to the invention for forming a laser weld between two components with the features of claim 1 therefore has the feature that at least one of the two components is designed to be absorbing in the joining area for the wavelength of the laser beam used. Furthermore, it is essential that the components are covered on the side facing the direction of incidence of the laser beam onto the components by another component, which consists of a material transparent to the wavelength of the laser beam, at least in a transmission region of the laser beam through the other component.

[0008] Advantageous further developments of the inventive method for forming a laser weld joint are listed in the dependent claims.

[0009] In a practical implementation of the process, an infrared laser is used as the laser beam source, and the material of the subsequent component must have a transmittance of at least 70% in the transmitted light area. However, lower transmittances are also conceivable in principle. Ideally, though, the transmittance of the material should be as high as possible to enable the process to be carried out with low power and minimal heat input into the subsequent component.

[0010] In order to minimize scattering or deflection of the laser beam when passing through the further component, it is also preferably provided that the laser beam penetrates the further component at least approximately perpendicularly in the transmission area in the area of ​​preferably parallel surfaces of the further component.

[0011] With a view to minimizing the coupling of thermal energy into the further component, it is also preferably provided that the laser beam is at least substantially unfocused in the transmission area of ​​the further component and has a focus diameter of less than 1.0 mm, preferably less than 0.3 mm, and most preferably less than 0.1 mm in the joining area.

[0012] Furthermore, to minimize processing time, it is advantageous to use a laser beam source with a power output of more than 500W. However, the required power depends on the specific application, and can range from approximately 100W to several kW.

[0013] The method according to the invention is preferably used for components where these consist of metal at least in the area of ​​the joining point.

[0014] The invention further comprises an assembly comprising two components joined together in a joining area by a laser weld. In addition, a further component is provided on the side facing the direction of an incident laser beam. This component consists of a material transparent to the wavelength of the laser beam in a transmission area of ​​the laser beam through the further component. The assembly is preferably manufactured according to a method described in the invention. In principle, almost all joining geometries between the components to be joined or welded are conceivable, e.g., butt joints, lap joints, fillet welds, through-hole joints, or connections between pins.

[0015] In a preferred further development of the assembly, the additional component is designed to have parallel surface planes in the transmission area and a maximum wall thickness of 3 mm. The required geometry enables low thermal stress on the additional component and / or the coupling of as much energy as possible into the joining area of ​​the two components.

[0016] In particular, it can be provided that the additional component forms a housing.

[0017] It may also be provided that the additional component outside the transmission area consists of a different material than the material in the transmission area and / or that the wall thickness of the material in the transmission area is reduced compared to areas at least immediately adjacent to the transmission area.

[0018] Further developing the last proposal, it may be provided that the additional component is made of plastic and is a component produced by a multi-component injection molding process, or that an element is arranged in the transmission area that is overmolded by the material of the remaining additional component or that is sealed against the additional component.

[0019] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments of the invention and from the drawings. Brief description of the drawings Fig. Figure 1 shows a schematic representation of an assembly to illustrate the inventive method for forming a laser weld joint between two components of the assembly. Fig. 2 a detail of the Fig. 1, in which a housing of the assembly has a reduced wall thickness in a transmission area of ​​a laser beam and Fig. 3 a view corresponding to the representation of the Fig. 2, in which a component transparent to the wavelength of the laser beam is inserted into the housing in the transmission area of ​​a laser beam. Embodiments of the invention

[0020] Identical elements or elements with the same function are provided with the same reference numbers in the figures.

[0021] In the Fig. Figure 1 shows an assembly 10 comprising two components 12 and 14 to be joined together. The two components 12 and 14 are preferably, but not exclusively, made of similar metals that are weldable. For example, the components 12 and 14 could be sheet metal parts, electrical connecting cables, or similar components. However, it is also conceivable that the first component 12, which is located on the side facing the direction of incidence of a laser beam LS from a laser beam source 100, consists of a material transparent to the wavelength LS of the laser beam source 100, and that the second component 14, which faces away from the direction of incidence of the laser beam LS, consists of a material that absorbs LS at that wavelength. In the latter case, the two components 12 and 14 are made of plastic.The second component 14 can contain additives, such as soot particles or similar, to adjust the absorption properties.

[0022] The two components 12, 14 are arranged in a further or third component 16 of the assembly 10, which in the illustrated embodiment forms a housing 18. In particular, the housing 18 is a closed housing 18, in which the components 12, 14 (as well as further components arranged in the housing 18) are arranged in an interior 19 of the housing 18. Fig. 1. To protect components or assemblies (not shown for the sake of simplicity) from the ingress of moisture, dirt, etc.

[0023] The two components 12, 14 are joined together in a joining area 20 by a laser weld 1. The laser weld 1 is generated by the laser beam LS of the laser beam source 100, which in the exemplary embodiment is an infrared laser beam source. In particular, the wavelength of the laser beam LS used has a wavelength λ of 1030 nm, and the power P of the laser beam source 100 is more than 500 W, preferably more than 1000 W.

[0024] The laser beam LS emitted from the laser beam source 100 is directed towards the housing 18 via a focusing lens 101. This reduces the focus diameter d1 of the raw beam from, for example, 40 mm in a transmission area 22 of the housing 18 to a focus diameter d2 of approximately 30 mm. In contrast, the focus diameter d3 in the joining area 20 of the two components 12, 14 has a diameter of (only) about 0.1 mm.

[0025] It is essential that the material of the housing 18, at least in the transmission area 22, consists of a material transparent to the wavelength of the laser beam LS. In particular, the material of the further or third component 16 or of the housing 18 has a transmittance T for the wavelength of the laser beam LS of at least 70%, preferably at least 80%, in the transmission area 22. Preferably, the material of the housing 18 therefore consists of a suitable plastic, at least in the transmission area 22.

[0026] Based on the Fig. It is further evident from Figure 1 that the additional or third component 16 has surfaces 24, 26 arranged parallel to each other, at least in the transmission area 22, wherein the wall thickness w of the additional component 16 in the transmission area 22 is preferably a maximum of 3 mm. The angle of incidence α of the laser beam LS into the transmission area 22 is preferably 90°. The geometries and transmittances described so far ensure that the material of the additional component 16 in the transmission area 22 is at least substantially not heated, or that the majority of the energy introduced by the laser beam LS into the housing 18 onto the joining area 20 is available for heating the two components 12, 14 in the joining area 20 above their melting temperature.

[0027] In the Fig. Figure 2 illustrates the case where the wall thickness w in the transmission area 22 of the further or third component 16 has the aforementioned maximum of 3 mm, while outside the transmission area 22 the wall thickness w of the further component 16 is increased. The reduction of the wall thickness w preferably takes place from the inside of the housing 18 in order to enable a homogeneous or flat and smooth surface on the outside of the housing 18.

[0028] In the Fig.Figure 3 shows a further embodiment of the additional or third component 16, in which the additional component 16 has an additional element 28 in the transmission area 22, which consists of a material transparent to the wavelength LS of the laser beam used. Outside the transmission area 22 or the element 28, the additional component 16 can consist of other materials, in particular materials that absorb light or are less transparent to the wavelength LS of the laser beam than in the transmission area 22.

[0029] The additional element 28 can be formed, for example, by a multi-component injection molding process with the further component 16, or by overmolding the element 28 with the material of the further component 16, or by the element 28 being inserted into the further component 16 by another connection (adhesive connection, screw connection or similar).

[0030] Specific applications of the described method or assembly 10 include, for example, the current-carrying phase connections between an electric motor and an inverter (components 12, 14) for electromobility applications, where the housing 18 consists of a material transparent to the wavelength LS of the laser beam used, at least in the transmission area 22. Screw connections on assemblies 10 can also be replaced by the described method using laser welding 1. Examples of applications include cell connections in 48V battery systems or in fuel cells. Welding connections in headlight systems can also be formed through mounted headlight lenses.

[0031] Examples of materials for the further or third component 16, at least in the transmission area 22, are thermoplastics or elastomers such as PMMA, PET, PS, PC, COC or PBT.

[0032] The method or assembly 10 described so far can be adapted or modified in a variety of ways without deviating from the inventive concept. Thus, depending on the application or materials, other wavelengths λ of the laser beam LS or other laser beam sources 100 can of course be used. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2010 029 978 A1

[0002] DE 10 2015 225 047 A1

[0003]

Claims

[1] Method for forming a laser weld joint (1) between two components (12, 14), wherein at least one of the components (12, 14) is formed in a joining area (20) of the components (12, 14) for the wavelength (λ) of the laser beam (LS) of a laser beam source (100), characterized by , that the components (12, 14) on the side facing an incoming direction of the laser beam (LS) onto the components (12, 14) are covered by a further component (16) which consists of a material transparent to the wavelength (λ) of the laser beam (LS) at least in a transmission area (22) of the laser beam (LS) through the further component (16). [2] Method according to claim 1, characterized by , that an infrared laser is used as the laser beam source (100), and that the material of the further component (16) has a transmittance (T) of at least 70% in the transmission area (22). [3] Method according to claim 1 or 2, characterized by, that the laser beam (LS) penetrates the further component (16) in the transmission area (22) at least approximately perpendicularly in the area of ​​preferably parallel surfaces (24, 26) of the further component (16). [4] Method according to any one of claims 1 to 3, characterized by , that the laser beam (LS) in the transmission area (22) is at least substantially unfocused and has a focus diameter (d3) of less than 1.0 mm, preferably less than 0.3 mm, most preferably less than 0.1 mm in the joining area (20). [5] Method according to any one of claims 1 to 4, characterized by , that a laser beam source (100) with a power (P) of more than 500W is used. [6] Method according to any one of claims 1 to 5, characterized by , that components (12, 14) are used which consist of metal at least in the joining area (20). [7] Assembly (10) comprising two components (12, 14) joined together in a joining area (20) by a laser welding connection (1), and a further component (16) arranged on the side facing a direction of incidence of a laser beam (LS) onto the components (12, 14), which in a transmission area (22) of the laser beam (LS) through the further component (16) consists of a material transparent to the wavelength (λ) of the laser beam (LS), wherein the assembly (10) is preferably manufactured according to a method according to one of claims 1 to 6. [8] Assembly according to claim 7, characterized by , that the further component (16) in the transmission area (22) has surfaces (24, 26) arranged parallel to each other and a wall thickness (w) of a maximum of 3mm. [9] Assembly according to claim 7 or 8, characterized by , that the further component (16) forms a housing (18). [10] Assembly according to any one of claims 7 to 9, characterized by, that the further component (16) outside the transmission area (22) is made of a different material than the material in the transmission area (22) and / or that the wall thickness (w) of the further component (16) in the transmission area (22) is reduced compared to areas at least immediately adjacent to the transmission area (22). [11] Assembly according to claim 10, characterized by , that the further component (16) is made of plastic and is a component (16) produced by a multi-component injection molding process, or that in the transmission area (22) an element (28) is arranged which is overmolded by the material of the remaining further component (16) or which is sealed against the further component (16).

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