WO2021136594A1

WO2021136594A1 - Method of interconnecting antenna parts of an antenna and antenna part

Info

Publication number: WO2021136594A1
Application number: PCT/EP2020/050042
Authority: WO
Inventors: Christian Helbig; Tekin ÖLMEZ; Qiangguo Zhou; Serban REBEGEA; Johann Baptist OBERMAIER
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2020-01-02
Filing date: 2020-01-02
Publication date: 2021-07-08

Abstract

Method of interconnecting antenna parts of an antenna and antenna part An electrical and mechanical connection between a non-plated first antenna part made of aluminum and a second antenna part of an antenna for radio frequency applications is established by connecting a connecting element made of aluminum and plated with a solderable plating to the first antenna part by laser welding, and interconnecting the second antenna part to the connecting element by soldering.

Description

Method of interconnecting antenna parts of an antenna and antenna part

The present invention generally relates to a method of producing an electrical and mechanical connection between a first antenna part and a second antenna part of an antenna for radio frequency (RF) applications according to the preamble of claim 1. The first antenna part is made of aluminum and is not plated.

Generally, the first antenna part relates to mechanical supporting structures of the antenna, which must be light weight and well conducting and are therefore made of aluminum. The first antenna part for example needs to be connected to the ground level of internal electrical components of the antenna that provide typically PCBs (printed circuit boards) or coaxial cables as interfaces. The only available and reliable galvanic connection of the antenna part to the PCBs and coaxial cables is established by soldering.

According to known prior art methods, the first antenna part therefore has to be fully or partially plated with a solderable plating, as the first antenna part is made of aluminum, which as such is not solderable. A full plating is expensive due to the excessive use of plating and a partial plating is expensive, as it requires the additional and elaborate process step of partial masking of the first antenna part before the solderable plating is applied for example by electroplating.

It is an object of the present invention to provide a simple and cost saving method of interconnecting the first antenna part to the second antenna part, so that the connection is electrically and mechanically stable.

This object is accomplished by the features of independent claim 1.

According to a first aspect, a method of producing an electrical and mechanical connection between a non-plated first antenna part made of aluminum and a second antenna part of an antenna for radio frequency applications is proposed. The method comprises connecting a connecting element made of aluminum and plated with a solderable plating to the first antenna part by laser welding, and interconnecting the second antenna part to the connecting element by soldering.

The connecting element may be small compared to the first antenna part. Plating only the connecting element with a solderable plating instead of partially or fully plating the first antenna part can be done rather quickly and at low cost.

The second antenna part may be any conductive part in an electric circuit of the antenna. Preferably, the second antenna part is or comprises a coaxial cable or a printed circuit board. In a preferred embodiment, the laser welding comprises moving a point of incidence of a laser beam on at least one of the first antenna part and the connecting element, wherein the movement of the point of incidence on the surface is a superposition of a substantially rectilineal movement along a welding path on the surface and wobbling. Thus, a PIM free or substantially PIM free connection between the first antenna part and the connecting element can be achieved. PIM free means free of passive intermodulation. The first antenna part and the connecting element can be joined at their shared contact areas by wobble mode laser welding. This technique will normally not produce any irregular or spurious connections between the two parts and will instead produce a regular, homogeneous contact zone that is substantially PIM free. Substantially PIM free means that the connection has a very low PIM level, e.g. lower than -150 dBc (decibels relative to carrier). The wobbling movement reduces or eliminates welding burs, which would be a PIM source. To benefit from the PIM free connection between the first antenna part and the connecting element, the two aluminum parts should be PIM free at their own. If RF signals are transmitted via the first antenna part and the second antenna part, it is essential that the connection between these two parts is PIM free.

The movement of the point of incidence of the laser beam comprises two components: a substantially rectilineal movement and wobbling (i.e. a wobble movement). “Substantially rectilineal” in this context means that the rectilineal movement has (at any point in time) a curvature that is small compared to a curvature of the wobble movement (e.g. the curvature of the rectilineal movement is less than 10 % of the curvature of the wobble movement). The rectilineal movement may in particular be straight, i.e. a movement along a straight line (in which case the curvature is zero). The wobbling may be a fast short-range cyclic movement of the point of incidence. “Short-range” in this context means that the point of incidence, assuming that the substantially rectilineal movement is zero, is confined to move within a relatively small wobble zone. “Cyclic movement” in this context means a sequence of cycles, each cycle corresponding to one closed trajectory of the point of incidence (again assuming that the substantially rectilineal movement is zero). “Fast” in this context means that the wobbling movement is faster (i.e. has a higher speed) than the substantially rectilineal movement. The substantially rectilineal movement moves the wobble zone along a welding path. The wobble movement may notably be a periodic elliptic (preferably circular) movement, preferably with a constant speed. In this case, the wobble movement is performed in a sequence of periods (“wobble periods”), wherein the point of incidence of the laser beam describes one full ellipse (or circle) in each period.

In an embodiment, the laser welding comprises applying the laser beam at least twice at a first end of the welding path and an opposite second end of the welding path and at least once at each point between the first end and the second end of the welding path. Preferably, the laser welding comprises applying the laser beam in a back-and-forth stroke along the welding path, wherein the welding is performed twice at each point of the welding path. Thus a PIM free connection can be reliably produced, even if the penetration depth of the laser beam is not sufficient at the onset point of the laser welding (e.g. if possible oxide layers or other residues on the first antenna part or the connecting element prevent proper penetration of the laser beam during the first application of the laser beam. This is particularly important at the onset point of the laser welding, since the laser beam may hit an unbroken oxide layer at this point.

Preferably, the laser welding starts at a first end of the welding path, is carried out to an opposite second end of the welding path and back to the first end. This way the back-and-forth stroke can be easily implemented and an even welding seam is formed.

In one embodiment, the wobbling is or comprises an elliptical movement, preferably a circular movement. The circular movement results in a relatively balanced laser power distribution within a stripe region (referred to herein as the welding stripe) that includes the welding path and extends to both sides of the welding path. This is favorable for achieving a PIM free connection between the first antenna part and the connecting element.

Preferably, the substantially rectilineal movement is slower than the wobbling. In other words, the wobbling has a higher speed than the substantially rectilineal movement. In a particular preferred embodiment, a speed of the substantially rectilineal movement (referred to as the rectilineal speed) is in the range of 10 to 200 mm/s, while a speed of the wobbling (referred to as the wobble speed) is in the range of 200 to 1000 mm/s. This way a laser power distribution favorable for producing a PIM free welding connection can be achieved in the welding stripe (i.e. a stripe region which includes the welding path and extends to both sides of the welding path).

In a preferred embodiment, a diameter of the laser beam is smaller than 10 pm and a power of the laser beam is between 250 W and 4000 W. These parameter ranges have been found suitable for achieving an appropriate penetration depth, effectively resulting in a smooth welding seem and hence a PIM free connection between the first antenna part and the connecting element.

In an advantageous embodiment, the first antenna part and the connecting element are welded together at a shared contact area, wherein the laser welding is conducted from a welding area, which is opposite and parallel to the contact area on the first antenna part or on the connecting element, wherein, preferably, the distance between the contact area and the welding area in the direction of the laser beam is between 0.5 to 3.5 mm. The advantage of this embodiment is that only sparks are generated on and around the welding area and not around the contact area, which would lead to particles close to the connection, which would be a possible PIM source. The distance is advantageously as the laser welding is energy efficient and the contact area between the first antenna part and the connecting element is welded completely.

In a particularly preferred embodiment, the solderable plating of the connecting element is a tin or silver plating, preferably with an underlying diffusion barrier layer of copper or nickel. Such a plating is highly solderable.

Preferably, the solderable plating of the connecting element covers the connecting element completely. This way the manufacturing of the solderable plaiting is very cost effective and easy to achieve.

According to a second aspect, the present invention also provides an antenna part of an antenna for radio frequency applications comprising a first antenna part and a second antenna part, wherein the first antenna part is made of aluminum. The first antenna part and the second antenna part are connected to each other by a connecting element, which is made of aluminum and is plated with a solderable plating. The connection may be established by one or more of the above-mentioned embodiments of the method according to the first aspect of the invention.

The second antenna part may be any conductive part in an electric circuit of the antenna. Preferably, the second antenna part is or comprises a coaxial cable or a printed circuit board.

Preferably, the first antenna part and the connecting element are made of aluminum or an aluminum alloy selected from a group consisting of AI5052, AIMg3, AIMg1.5, AI6063, AISi9, and ADC12. These materials are suitable for the first antenna part and for the connecting element and can easily be welded using the method described above.

In one embodiment, the antenna part is a radiating element, a reflector, a phase shifter, a filter, a combiner or divider, a distribution network, a wave guide, or a suspended stripline. These antenna parts benefit the most from the inventive design.

In a preferred embodiment, one of the first antenna part and the connecting element comprises a protruding tab, wherein an end face of the protruding tab is welded to a surface of the other one of the first antenna part and the connecting element. The contact area between the first antenna part and the connecting element, which is the end face of the protruding tab, can be sized easily and hence the welded connection has less design limitations.

In an embodiment, the connecting element is a die casting element, which comprises at least one curved soldering interface portion for the second antenna part, and at least one connecting tab protruding from the soldering interface portion, wherein the connecting element is interconnected to the first antenna part in that an end face of the connecting tab is welded to a surface of the first antenna part. A die casting element can be efficiently manufactured with complex geometries. The curved soldering interface portion accommodates the outer dimensions of the second antenna part and hence the soldering is stable. Further, the connecting tab allows a stable connection to the first antenna part by welding.

Preferably, the connecting tab has a height h ³ 1 mm from an onset of the connecting tab on the soldering interface portion to the end face of the connecting tab. The end face of the connecting tab preferably has a length in the range of 1 mm £ I £ 20 mm. And a width of the end face is preferably in the range of 0.5 mm £ w £ 3 mm. Due to this sizing, an electrically and mechanically stable connection is formed between the first antenna part and the connecting element.

In an advantageous embodiment, the connecting element is a sheet metal part, which comprises at least one soldering interface portion for the second antenna part, which is a curved section generated by bending the sheet metal and accommodates the outer dimension of the second antenna part, and at least one welding section, which is adjacent to the soldering interface portion, wherein the interconnection between the connecting element and the first antenna part is on the welding section. If the connecting element is a metal sheet part, it can be manufactured very cost effective.

Preferably, the welding section comprises a tab, which is bent towards the first antenna part and welded to the first antenna part. The tab can be manufactured efficiently and it forms a defined contact area between the connecting element and the first antenna part, where the two components are welded together PIM free and mechanically stable.

In an alternative embodiment, the connecting element is an extruded element, wherein the extruded element comprises at least a curved soldering portion for the second antenna part and at least one connecting portion protruding from the soldering portion, which is welded to the first antenna part. If the connecting element is an extruded element, it can be manufactured very cost effective and offers an enhanced stability.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, wherein: Figure 1 shows a first embodiment of a first antenna part and connecting elements in a perspective view and a detailed view of the first antenna part, the connecting element and a second antenna part,

Figures 2a, b show a segment of the first antenna part and the connecting element, wherein figure 2a shows a segment of the connecting element of the embodiment of figure 1 from above and figure 2b shows a side view of the connecting element and parts of the first antenna part,

Figures 3a, b show different connecting elements with the same second antenna part in a perspective view,

Figures 4a, b show a second embodiment of a first antenna part with attached connecting elements in a perspective top view and a perspective bottom view, and

Figures 5a, b show a third embodiment of first antenna parts, an attached connecting element and second antenna parts.

For the following explanations, the same parts are designated by the same reference signs. If a figure contains reference signs that are not described in more detail in the corresponding description of the Figure, reference is made to preceding or subsequent figures.

Figure 1 shows an embodiment of a first antenna part 1 and connecting elements 3 diagonally from above and a detail view of the first antenna part 1 , the connecting element 3 and a second antenna part 2. In this embodiment, the first antenna part 1 is a phase shifter body, which may be made of aluminum or an aluminum alloy. The aluminum allow may be selected, for example, from the group consisting of AI5052, AIMg3, AIMg1.5, AI6063, AiSi9, or ADC12. The first antenna part 1 comprises protruding tabs 6 with end faces 7. The end faces 7 are welded to the connecting element 3, which also may be made of aluminum or an aluminum alloy, for example, selected from the group consisting of AI5052, AIMg3, AIMg1.5, AI6063, AiSi9, or ADC12. The connecting element is entirely plated with a solderable plating made of tin or silver. The connecting element 3 comprises two welding sections 9. A laser beam 5 is used to weld the connecting element 3 along separate welding paths 4 to the end faces 7 of the protruding tabs 6 of the first antenna part 1. In order to achieve a PIM free connection between the first antenna part 1 and the connecting element 3, the laser welding has to be done according to the method, which is described in more detail in the description of figures 2a and 2b. The connecting element 3 further comprises the soldering interface portion 10 in between the two welding sections 9 to which a second antenna part 2 is soldered. In this embodiment, the second antenna part 2 is a coaxial cable and its outer conductor 8 is soldered to the soldering interface portion 10.

Figures 2a and 2b show a segment of the connecting element 3 from the top side in figure 2a and from a lateral side in figure 2b, wherein figure 2b further shows the protruding tabs 6 of the first antenna part 1. The inventive welding method comprises applying a laser beam 5 in motion along the welding path 4 in a wobble mode. The point of incidence of the laser beam 5 thus travels along a trajectory 25. The trajectory 25 is the result of a superposition of a substantially rectilineal movement along the welding path 4 and wobbling. By this laser welding technique, the end faces 7 of the protruding tabs 6 of the first antenna part 1 , which are shown in figure 2b in dotted lines, are welded to the connecting element 3. The connection between the two aluminum parts 1, 3 will likely be PIM free, which means that the PIM level is below - 150dBc. Certain techniques are implemented to achieve a PIM level as low as possible at the welding connections. The welding with the wobble mode 10 starts at a first end 11 of the welding path 4 is carried out to a opposite second end 12 of the welding path 4 and back to the first end 11. This movement is called a back-and-forth stroke 13 and guarantees that the welding is performed twice at each point of the welding path 4. This is preferred, as the penetration depth of the laser beam 5 may be too small at the beginning of the laser welding process. The back-and-forth stroke 13 leads to a PIM free welding seam at each point along the welding path 4. The speed of the rectilineal movement of the back-and-forth stroke 13 is preferably in the range of 10 to 40 mm/s while the wobble speed is preferably in the range of 300 to 700 mm/s. By moving the laser beam 5 with a diameter smaller than 7 pm at this speed, the applied power, which should be in the range of 500 W to 4000 W, of the laser beam 5 is distributed advantageously. Further, the welding is performed from a welding area 14 of the connecting element 3 opposite to the contact area 15 of the connecting element 3, which is in contact with the end face 7 of the protruding tabs 6 of the first antenna part 1. The distance between these two parallel areas 14, 15 is given by the thickness 16 of the connecting element 3 and is in the range of 0.5 to 3.5mm. Welding the end faces 7 and the contact area 15 indirectly together from the welding area 14, has the advantage, that no sparks are generated at the connection between the first antenna part and the connecting element, which would be a possible PIM source.

Figures 3a and 3b show different embodiments of the connecting element 3, which are connected to the outer conductor 8 of the coaxial cable as second antenna part 2. The connecting element 3 shown in figure 3a is a metal sheet part, which is bent in the soldering interface portion 10 to harbour the outer conductor 8 of the coaxial cable. Using a metal sheet part as connecting element is advantageous regarding the related costs of manufacturing. In order to connect the connecting element 3 with a first antenna part 1, the connecting element comprises tabs 17, which are bent away from the soldering interface portion 10. The tabs 17 are welded to a surface of the first antenna part 1. Figure 3b shows another embodiment of the connecting element 3. The connecting element 3 of this embodiment is an extruded element, which also comprises a curved soldering portion 18 for the outer conductor 8 of the second antenna part 2 and two connecting portions 19 protruding from the soldering portion 18, which are welded to the first antenna part 1.

Figures 4a and 4b show an embodiment in which the first antenna part 1, which is a housing for a suspended stripline module is equipped with two connecting elements 3 in form of the embodiment shown in figure 3 a. The connecting elements 3 are welded along the welding path 4 at the end faces of the two tabs 17 to the first antenna part 1 such that the soldering interface portion is directed towards an opening 20 in the first antenna part, which is leading into a cavity 21 inside the first antenna part 1. The second antenna part 2, which is a coaxial cable is soldered to the connecting element 3 at its outer conductor 8 in a way that the inner conductor 22 of the coaxial cable reaches into the opening 20 of the cavity 21 of the first antenna part 1 and can be connected to the suspended stripline module, which can be placed into the cavity 21.

Figures 5a and 5b show yet another embodiment of the first antenna part 1, which comprises four sheet metal parts of a dipole, and a die casted connecting element 3, which is the main body of the dipole. The die casted connecting element 3 comprises connecting tabs 23, which are welded to the first antenna parts 1 at their end faces. The connecting element 3 further comprises a soldering portions 24 to which the second antenna part 2 is soldered. The die casted connecting element 3 can be hollow inside to place a PCB or other signal transmitting devices into it. Further, the soldering portion 24 can be formed such that the outer conductor 8 of a coaxial cable as second antenna part 2 is welded to the connecting element and the inner conductor 22 of the coaxial cable is connected to the PCB or other signal transmitting device inside the connecting element 3.

List of reference signs

1. first antenna part

2. second antenna part

3. connecting element

4. welding path

5. Laser beam

6. Protruding tab

7. End face

8. Outer conductor

9. Welding portion

10. Soldering interface portion (metal sheet connecting element)

11. First end of welding path

12. Second end of welding path

13. Back-and-forth stroke

14. Welding surface

15. Contacting surface

16. Thickness of connecting element

17. Tab

18. Curved soldering portion

19. Connecting portion

20. Opening

21. Cavity

22. Inner conductor

23. Connecting tabs

24. Soldering interface portion (die casted connecting element)

25. Trajectory

Claims

1. A method of producing an electrical and mechanical connection between a first antenna part (1) and a second antenna part (2) of an antenna for radio frequency applications, wherein the first antenna part is made of aluminum and is not plated, characterized in that the method comprises: connecting a connecting element (3) to the first antenna part (1) by laser welding, the connecting element (3) being made of aluminum and being plated with a solderable plating, interconnecting the second antenna part (2) to the connecting element (3) by soldering.

2. The method according to claim 1 , characterized in that the second antenna part is or comprises a coaxial cable or a printed circuit board.

3. The method according to claim 1 or 2, characterized in that the laser welding comprises moving a point of incidence of a laser beam (5) on at least one of the first antenna part (1) and the connecting element (3), wherein the movement of the point of incidence is a superposition of: a substantially rectilineal movement along a welding path (4) and wobbling.

4. The method according to claim 3, characterized in that the laser welding comprises applying the laser beam (5) at least twice at a first end (11) of the welding path (4) and an opposite second end (12) of the welding path (4) and at least once at each point between the first end (11) and the second end (12) of the welding path (4).

5. The method according to claim 3 or 4, characterized in that the wobbling is or comprises an elliptical movement.

6. The method according to one of the claims 3 to 5, characterized in that the substantially rectilineal movement is slower than the wobbling.

7. The method according to one of the claims 1 to 6, characterized in that the solderable plating of the connecting element (3) is a tin plating or a silver plating.

8. An antenna part for an antenna for radio frequency applications, the antenna part comprising a first antenna part (1) and a second antenna part (2), wherein the first antenna part (1) is made of aluminum, characterized in that the first antenna part (1) and the second antenna part (2) are connected to each other by a connecting element (3), which is made of aluminum and is plated with a solderable plating, by the method of one of the claims 1 to 7.

9. The antenna part according to claim 8, characterized in that the second antenna part

(2) is or comprises a coaxial cable or a printed circuit board.

10. The antenna part according to claim 8 or 9, characterized in that the first antenna part (1) and the connecting element (3) are made of aluminum or an aluminum alloy selected from a group consisting of AI5052, AIMg3, AIMg1.5, AI6063, AISi9, and ADC12.

11. The antenna part according to one of claims 8 to 10, characterized in that the antenna part is a radiating element, a reflector, a phase shifter, a filter, a combiner or divider, a distribution network, a wave guide, or a suspended stripline.

12. The antenna part according to one of the claims 8 to 11 , characterized in that one of the first antenna part (1) and the connecting element (3) comprises a protruding tab (6), wherein an end face (7) of the protruding tab (6) is welded to a surface of the other one of the first antenna part (1) and the connecting element (3).

13. The antenna part according to one of the claims 8 to 12, characterized in that the connecting element (3) is a die casting element which comprises at least one curved soldering interface portion (24) for the second antenna part (2) and at least one connecting tab (23) protruding from the soldering interface portion (24), wherein the connecting element (3) is interconnected to the first antenna part (1) and an end face of the connecting tab (23) is welded to a surface of the first antenna part (1).

14. The antenna part according to one of the claims 8 to 12, characterized in that the connecting element (3) is a sheet metal part, the sheet metal part comprising a soldering interface portion (10) for the second antenna part (2), the soldering interface portion being a curved section generated by bending the sheet metal and accommodating the outer dimension of the second antenna part (2), and at least one welding section (9) which sits adjacent to the soldering interface portion (10), wherein the interconnection between the connecting element (3) and the first antenna part (1) is on the welding section (9).

15. The antenna part according to claim 14, characterized in that the welding section (9) comprises a tab (17) which is bent towards the first antenna part (1) and welded to the first antenna part (1).