WO2024083421A1

WO2024083421A1 - Method for producing a high-frequency waveguide

Info

Publication number: WO2024083421A1
Application number: PCT/EP2023/075502
Authority: WO
Inventors: Thomas Ilg
Original assignee: Vega Grieshaber Kg
Priority date: 2022-10-20
Filing date: 2023-09-15
Publication date: 2024-04-25
Also published as: DE102022211150A1

Abstract

The invention relates to a method for producing a waveguide (10), in particular a high-frequency waveguide, by sintering. The method comprises the following steps: providing a filler core (20); encapsulating the entire periphery of the filler core (20) with a fusible composite (30), wherein the fusible composite (30) comprises a metal powder and a binder; heating the filler core (20) and the fusible composite (30) to a first temperature at which the filler core (20) and the binder of the fusible composite (30) are eliminated; and heating the fusible composite (30) to a second temperature at which the fusible composite (30) sinters, such that the sintered fusible composite (30) forms the waveguide (10).

Description

VEGA Grieshaber KG

Hauptstrasse 5, 77709 Wolfach, Germany

Manufacturing process for a high-frequency waveguide

Reference to related applications

The present application claims priority from German patent application No. 10 2022 211 150.8, filed on October 20, 2022, which is incorporated in its entirety by reference into the present document.

Field of the invention

The invention relates to a manufacturing method for a waveguide, in particular for a high-frequency waveguide and/or a radar waveguide. The invention further relates to a waveguide and a use.

Background

In the current state of the art, waveguides are manufactured using what is known as deep-hole drilling. From a certain diameter of the inner wall of the waveguide and/or from a certain ratio of length to diameter of the inner wall, it can be difficult to carry out this type of deep-hole drilling. One reason may be that the drill becomes too thin to ensure sufficient stability for drilling. Summary

The object of the invention is to provide a method that provides an alternative method for producing a waveguide. This object is achieved by the subject matter of the independent patent claims. Further developments of the invention emerge from the subclaims and the following description.

One aspect relates to a method for producing a waveguide for high frequency waves, in particular for radar waves, by means of sintering, comprising the steps:

Providing a filling core;

Enveloping an entire circumference of the filling core with a melt composite, the melt composite comprising a metal powder and a binder;

Heating the filler core and the melt composite to a first temperature at which the filler core and the binder of the melt composite are eliminated; and

Heating the melt composite to a second temperature at which the melt composite sinters so that the sintered melt composite forms the waveguide.

A waveguide is a type of tube whose inner wall is essentially straight. The outer wall of the waveguide can have any shape. The waveguide can, for example, be designed as a high-frequency waveguide, which is particularly suitable and/or designed for the transmission of high-frequency waves. High-frequency waves are understood to be electromagnetic waves with a frequency of over 70 GHz, over 100 GHz, and/or over 200 GHz.

The filler core can, for example, consist of the same or a similar material as the binder of the melt composite. A key feature of the filler core is that this is eliminated at the first temperature, so that the filler core (and the binder) are removed and an elongated cavity is created that only consists of the metal component of the melt composite. This step is sometimes referred to as "debinding". The "debinding" step can comprise several sub-steps. The first temperature can, for example, be in a range between 300 °C and 600 °C. The second temperature can be higher than the first temperature and can, for example, be in a range between 1120 °C and 1135 °C. By heating the filling core to such a high temperature, the melt composite can sinter, and thus the sintered melt composite can form the waveguide. The sintering process can have several phases. The temperatures during elimination and/or during the "actual" sintering can depend on the components of the melt composite, in particular on the choice of binder and/or sintering material.

The sintering process can be carried out in three “stages”, during which the porosity and volume of the so-called “green body” (the original melt composite) are significantly reduced. In the first “stage”, for example, the green body can be compacted. In the second stage, the porosity can be reduced. The strength of the sintered body can be based on so-called “sinter necks”, for example. These “sinter necks” are formed in the third stage by surface diffusion between the powder particles.

In some embodiments, the workpiece can be calibrated after the last process, e.g. if a very high degree of dimensional accuracy is required, which cannot be achieved by pure sintering due to the volume loss that cannot be precisely calculated. The sintered workpiece can then be pressed into a mold again under high pressure. This can be a method to achieve increased dimensional accuracy and/or, for example, compliance with technical tolerances (shape and position tolerance).

Before heating the fill core, the fill core may be coated with the fused composite over its entire circumference. In at least some processes, it may be possible to tolerate small gaps in the coating, particularly if these small gaps can be closed during heating and/or sintering - e.g. by flowing the fused composite. The coating may be achieved, e.g., by spraying with the fused composite (e.g., by means of metal powder injection molding) and/or by pressing, e.g., into a waveguide shape. In at least some types of waveguides, further and/or alternative post-treatment may be useful and/or necessary. If the waveguide is to be designed as a high-frequency waveguide, for example, smoothing the inner wall of the waveguide can be considered.

This process represents an alternative to conventional drilling. Furthermore, in at least some cases this process can be used for "drilled holes" (or feedthroughs) that can be longer, narrower and/or "slimmer" than conventionally manufactured feedthroughs. "Slimmer" refers to a larger length to diameter ratio of the inner wall of the feedthrough. For example, in the prior art, so-called "deep hole drilling" can produce holes with a length to diameter ratio of about 85:1. As the holes become smaller, this value can decrease because the drill bits become increasingly unstable and the resulting chips can cause the drill bit to break off. Holes of, for example, smaller than 2 mm, 1 mm or 0.5 mm can therefore be difficult to produce. On the other hand, a larger length to diameter ratio can be achieved using this manufacturing process.

In some embodiments, an increased pressure is exerted on the melt composite and/or the filling core during heating. The pressure can be 10 bar, for example. This makes it possible to produce a particularly dense waveguide.

In some embodiments, a shape of an inner wall of the waveguide is formed by the filler core, the shape having a defined cross-section. In some embodiments, the filler core has a round, rectangular, and/or square cross-section. This can represent a further advantage over the deep drilling manufacturing process, which can only produce round feedthroughs.

In some embodiments, a diameter of the inner wall is less than 2 mm, eg less than 1 mm, eg less than 0.5 mm. In some embodiments, a ratio of length to diameter of the inner wall of the waveguide is a factor greater than 50, eg greater than 85, eg greater than 100. In this case, a definition of a "diameter" for non-round feedthroughs can be an arithmetic mean of the radii and/or the largest and smallest radius of the feedthrough. This can be advantageous for the production of Feedthroughs can be used which can be longer, narrower and/or "slimmer" than conventionally manufactured feedthroughs. Using the method described, it can be possible to create very thin holes as well as a particularly high length to diameter ratio of the inner wall. Implementation using other methods, e.g. drilling, can be extremely complex or even impossible. For example, a drill with a small diameter and a long length may not be stable enough to enable a hole to be drilled in a metal suitable for a waveguide with sufficient quality. An inner wall diameter with the dimensions described can be advantageous and/or necessary for high frequency radar waves. A waveguide with a longer length - e.g. greater than 25 mm, greater than 50 mm, etc. - can be advantageous and/or necessary, e.g. because of a high temperature of the process to be monitored, and/or e.g. because of a higher homogeneity (and therefore a lower transmission loss) of the radar waves, which can be relevant from a certain length of the waveguide.

In some embodiments, the method has a further step: after sintering (i.e. heating the filler core to the second temperature), smoothing and/or coating the inner wall of the waveguide. This can be particularly useful if certain quality requirements are applied to the inner wall of the waveguide. This can be necessary in particular when the waveguide is used to conduct high-frequency waves. The coating can be carried out, for example, before smoothing, after smoothing or instead of smoothing. The coating can be carried out in multiple layers. The coating, in particular before smoothing, can correspond to “filling in” uneven areas. The coating can be carried out using a filler material, e.g. a metal. The coating can be carried out, e.g. in a last or penultimate operation, e.g. with a material such as gold, rhodium, stainless steel, etc., e.g. in order to achieve a high-quality high-frequency waveguide.

In one embodiment, the smoothing of the inner wall of the waveguide is achieved by selectively evaporating a part of the inner wall of the waveguide, in particular by means of a laser. This embodiment can be particularly time-saving Vaporization can be combined with other straightening methods.

In some embodiments, the smoothing of the inner wall of the waveguide is achieved by means of a grinding wire and/or a plurality of grinding wires. A grinding wire can be understood as a type of small file. In one embodiment, the grinding wire or the grinding wires have a strictly monotonically increasing diameter and/or a strictly monotonically decreasing roughness. This makes it possible to achieve a selectable quality, e.g. selectable according to quality and/or cost specifications.

In some embodiments, the filling core is coated with the melt composite by means of metal powder injection molding or metal powder injection molding (MIM, "spraying") and/or by pressing. The pressing can be carried out, for example, by means of a mold - similar to a casting mold.

Alternatively or additionally, the “green body” can be manufactured using an injection molding process, for example.

In one embodiment, the melt composite contains a metal powder, in particular titanium, stainless steel, e.g. stainless steel 1.4404, and/or a binder. This can be advantageous, for example, for high-frequency waveguides. Other metal powders can also be used that are suitable for high temperatures, such as those that occur during sintering, and also meet the special requirements for a radar waveguide.

One aspect relates to a waveguide manufactured as described above and/or below and/or a waveguide consisting of or comprising sintered metallic material.

For example, such a “slim” waveguide can be used to create a waveguide for a radar sensor that is suitable for high frequencies, e.g.

150 GHz and higher, as well as for high operating temperatures, e.g. up to 450 °C. In conventional devices, instead of a "slim" Waveguide manufactured as described above and/or below - for example

4 to 5 waveguides are used, which have to be connected precisely and/or laboriously to one another in order to create a distance between the process (or the antenna) and the sensor electronics, which excludes any thermal hazard to the sensor electronics due to the high process temperatures. For example, in the state of the art, several conventional waveguides ("temperature pieces") are built together in the PULS6x sensor from Vega to enable higher operating temperatures.

In one embodiment, the waveguide is designed for combination with a radar sensor, wherein the radar sensor is designed for a frequency range of approximately 180 GHz and/or 240 GHz. Radar sensors for these frequency ranges can advantageously be designed to be particularly robust and reliable, and/or be offered by several manufacturers and/or have a particularly good price-performance ratio.

In some embodiments, the waveguide has an inner wall that is configured for transmission of radar waves, in particular in a frequency range between 100 GHz and 500 GHz, e.g. between 150 GHz and 300 GHz.

In some embodiments, the waveguide has a low wall thickness for temperature decoupling. In some embodiments, the waveguide has a material with low thermal conductivity for temperature decoupling. Since high to very high temperatures can occur during measurements in at least some process environments, effective temperature decoupling can be particularly advantageous. By means of the method described above and/or below, a low wall thickness of the waveguide can be achieved and/or a material with low thermal conductivity can be used.

One aspect relates to the use of a waveguide as described above and/or below for conducting high-frequency waves, in particular radar waves, for example in a frequency range between 100 GHz and 500 GHz, in particular between 150 GHz and 300 GHz. The waveguide can be particularly well suited for combination with a radar sensor as described above and/or below, for example, for a radar sensor designed for a frequency range of approximately 180 GHz and/or 240 GHz.

It should be noted that the various embodiments described above and/or below can be combined with one another.

For further clarification, the invention is described using embodiments shown in the figures. These embodiments are to be understood as examples only and not as limitations.

Short description of the characters

It shows:

Fig. 1 schematically shows a waveguide according to an embodiment;

Fig. 2 is a flow chart showing a method according to an embodiment.

Detailed description of embodiments

Fig. 1 shows a schematic of a waveguide 10 according to an embodiment and components for its production. For production, a melt composite 30 is introduced into a mold 40 - similar to a casting mold. The mold 40 can be realized, for example, as two half molds. Furthermore, a filling core 20 is introduced, e.g. in the middle of the melt composite 30. After the mold 40 is closed, the filling core 20 is heated to a first temperature at which the filling core 20 and the binder of the melt composite 30 are eliminated. In some embodiments, this elimination can have several sub-steps. In the next step, the melt composite 30 is heated to a second temperature which is higher than the first temperature and at which the melt composite 30 sinters, so that the sintered melt composite 30 forms the waveguide 10. The mold 40 can also be heated in this phase.

In some embodiments, after removing the filling core 20, an inner wall 12 of the waveguide 10 can be smoothed and/or coated. For smoothing and/or coating, the sintered waveguide 10 can remain in the mold 40 or be removed, depending on the manufacturing process.

Fig. 2 shows a flow chart 100 with a method according to an embodiment. In a step 102, a filler core 20 (see Fig. 1) is provided. In a step 104, an entire circumference of the filler core 20 is coated with a melt composite 30, wherein the melt composite comprises a metal powder and a binder. In a step 106, the filler core 20 and the melt composite are heated to a first temperature at which the filler core 20 and the binder of the melt composite 30 are eliminated. In a step 108, melt composite 30 is heated to a second temperature at which the melt composite 30 sinters so that the sintered melt composite 30 forms the waveguide 10. In an optional step 110, an inner wall 12 of the waveguide 10 is smoothed and/or coated.

List of reference symbols

10 waveguides

12 Inner wall

20 filling core

30 Enamel composite

40 Shape

100 Flowchart

102 - 110 steps

Claims

Method for producing a waveguide (10) for high frequency waves by sintering, comprising the steps:

Providing a filling core (20);

Enveloping an entire circumference of the filling core (20) with a melt composite (30), the melt composite (30) comprising a metal powder and a binder;

Heating the filler core (20) and the melt composite (30) to a first temperature at which the filler core (20) and the binder of the melt composite (30) are eliminated; and

Heating the melt composite (30) to a second temperature at which the melt composite (30) sinters so that the sintered melt composite (30) forms the waveguide (10). Method according to claim 1, wherein during the heating an increased pressure is exerted on the melt composite (30) and/or the filler core (20). Method according to one of the preceding claims, wherein the filler core (20) consists of the binder or comprises the binder. Method according to one of the preceding claims, wherein a shape of an inner wall (12) of the waveguide (10) is formed by the filler core (20), and/or wherein the filler core (20) has a round, rectangular and/or square cross-section.

5. Method according to one of the preceding claims, wherein a diameter of the inner wall (12) is less than 2 mm, e.g. less than 1 mm, e.g. less than 0.5 mm, and/or a ratio of length to diameter of the inner wall (12) of the waveguide (10) is a factor greater than 50, e.g. greater than 85, e.g. greater than 100.

6. Method according to one of the preceding claims, with the further step: after removing the filling core (20), smoothing and/or coating the inner wall (12) of the waveguide (10).

7. The method according to claim 6, wherein the smoothing of the inner wall (12) of the waveguide (10) is realized by selective evaporation of a part of the inner wall (12) of the waveguide (10), in particular by means of a laser.

8. The method according to claim 6, wherein the smoothing of the inner wall (12) of the waveguide (10) is realized by means of a grinding wire and/or a plurality of grinding wires.

9. The method according to claim 8, wherein the grinding wire or the grinding wires have a strictly monotonically increasing diameter and/or a strictly monotonically decreasing roughness.

10. Method according to one of the preceding claims, wherein the coating of the filling core with the melt composite (30) is realized by means of metal powder injection molding and/or by means of pressing.

11. Method according to one of the preceding claims, wherein the melt composite (30) contains a metal powder, in particular titanium, stainless steel, e.g. stainless steel 1.4404, and a binder.

12. Waveguide (10) manufactured by a method according to one of the preceding claims, and/or

Waveguide (10) consisting of or comprising sintered metallic material.

13. Waveguide (10) according to claim 12, which is designed for combination with a radar sensor, wherein the radar sensor is designed for a frequency range of approximately 180 GHz and/or 240 GHz.

14. Waveguide (10) according to claim 12 or 13, wherein an inner wall (12) of the waveguide (10) is designed for transmission of radar waves, in particular in a frequency range between 100 GHz and 500 GHz, e.g. between 150 GHz and 300 GHz, and/or wherein the waveguide (10) has a small wall thickness and/or a material with low thermal conductivity for temperature decoupling.

15. Use of a waveguide (10) according to claim 12, 13 or 14 for conducting high-frequency waves, in particular radar waves, for example in a frequency range between 100 GHz and 500 GHz, in particular between 150 GHz and 300 GHz.