WO2022036700A1

WO2022036700A1 - Filter unit and radio node

Info

Publication number: WO2022036700A1
Application number: PCT/CN2020/110548
Authority: WO
Inventors: Tao Xie; Jan Fallgren; Erwang DONG; Jianjun AN
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2020-08-21
Filing date: 2020-08-21
Publication date: 2022-02-24
Also published as: WO2022036700A9; CN216122362U

Abstract

The present disclosure provides a filter unit and a radio node including the filter unit. The filter unit comprises a dielectric filter, a bracket with a seating and multiple pins soldered with the dielectric filter. The radio node comprises the filter unit and a radio board soldered with seating of the bracket. With the bracket, tension conducted from the radio board expansion caused by temperature rising can be offset by the deformation of the pins. The dielectric filter can be protected from being cracked.

Description

[Title established by the ISA under Rule 37.2] FILTER UNIT AND RADIO NODE

FIELD OF THE INVENTION

The present disclosure generally relates to a structure of a filter unit and in particular to a dielectric filter unit and a radio node including the filter unit.

BACKGROUND

Nowadays, filters are required to have the characteristics of low loss, small size, light weight and low cost. Accordingly, dielectric filters that use materials with a high dielectric constant as transmission media, such as ceramic waveguide filters, are widely used, and are continuously substitute metal filters which have a longer history in quite some areas.

To assemble a ceramic filter onto a mother board, manufacturers usually purchase filter modules provided from vendors. A filter module usually comprises a ceramic filter and a smaller PCB, or sometimes called a substrate, on which the ceramic filter soldered. Then, manufacturers solder the filter module onto a mother board.

Taking telecommunication field as an example, the mother board could be a radio board. When it is applied to a radio unit or an antenna unit such as remote radio unit (RRU) or an advanced antenna system (AAS) , multiple filter units would be assembled onto a same mother board. Therefore, it becomes a part of a radio node, such as a base station, or any other radio devices.

As is shown in Figure 1, a ceramic filter 101 is mounted on a small PCB 103 via a solder layer 102 in-between. The small PCB 103 lays on a radio PCB 105 via a solder layer 104 in-between. Normally, a heatsink 107 is fixed with the radio PCB 105 via some screws 106. Since the structure comprises components made of different material, including soldering tin, steel screw, PCB, ceramic filter, heatsink mainly in Aluminum, the inventors found that it might cause some trouble when it starts working and the temperature goes higher.

Coefficient of thermal expansion (CTE) of these materials are quite different. Table 1 shows example value of corresponding CTE of those different materials of which different parts are mainly made. Higher CTE value means larger expansion of size caused by temperature rising.

Table 1 CTE of corresponding materials

During the radio node is working or even assembling before being put into use, temperature of those material changes. Compared to material with higher CTE expanding more, ceramic filter 201 expands less in dimension than the others. Therefore, the ceramic filter is easy to crack due to tension conducted from the small PCB 203, which also receives tension conducted from heatsink 207 and radio board 205. Tension is transferred through the layers one by one, as shown in Fig 2.

There’s a need to mitigate the cracking risk of the ceramic filter, in order to improve the yield and quality of filter unit and the products in which the filter unit is included.

SUMMARY

In view of the foregoing, an object of the present disclosure is to mitigate cracking risk of ceramic filter caused by the tension from the assembling components.

In accordance with one aspect of the present application, it provides a filter unit comprising a dielectric filter and a bracket. The bracket comprises a seating and more than one pins raising from one side of the seating. The other side of the seating is to be soldered with a printed circuit board, and the pins are soldered with a surface of the dielectric filter.

In some embodiments, the pins and the seating are an integrated. In alternative embodiments, the pins are soldered on the seating.

In some embodiments, the pins are shaped in any of: straight strip, or T-style, curving strip.

In a further embodiment, the bracket has at least one edge with a fringe folded towards the same direction as the pins, wherein the fringe enfolds the filter at its edge.

In some embodiments, the bracket is made of metal. In alternative embodiments, the bracket is made of electroconductive plastics.

In accordance with another aspect of the present application, the disclosure provides a radio node comprising a dielectric filter, a bracket and a radio board connected to the dielectric filter. The bracket comprises a seating and multiple pins raising from one side of the seating. The seating is mounted on a surface of the radio board with the other side of the seating, and the multiple pins are soldered with a surface of the dielectric filter.

In some embodiments, the bracket further comprises an input and output passage which raises from the seating at the same side of the pins, wherein electric lines connected the filter to the radio board are put inside of the input and output passage.

In some embodiments, the dielectric filter is a ceramic waveguide filter.

With the bracket provided in the disclosure, tension conducted from the radio board expansion caused by temperature rising can be offset by the deformation of the pins. The dielectric filter can be protected from being deformed and even cracked.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure itself, the preferable mode of use and further objectives are best understood by reference to the following detailed description of the embodiments when read in conjunction with the accompanying drawings, in which:

Fig. 1 illustrates a structure of a ceramic filter assembled on a radio board according to a current solution;

Fig. 2 illustrates the expansion of different components and the tension brought from a small PCB to the filter, making the filter easy to get cracked, according to current solution;

Fig. 3 shows an example of structure of a radio node, including a filter unit with a bracket, according to embodiments of the present disclosure;

Fig. 4 shows deformation of the bracket during the radio node is working, according to embodiments of the present disclosure;

Fig. 5a and 5b show steps of manufacturing the bracket, according to embodiments of the present disclosure;

Fig. 5c shows the step of assembling the filter unit, according to embodiments of the present disclosure;

Fig. 5d illustrates a further design of the bracket with fringes, according to embodiments of the present disclosure.

DETAILED DESCRIPTION

The embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the present disclosure, rather than suggesting any limitation on the scope of the present disclosure. Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present disclosure should be or are in any single embodiment of the disclosure. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure.

Furthermore, the described features, advantages, and characteristics of the disclosure may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the disclosure may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the disclosure.

As used herein, the terms “first” , “second” and so forth refer to different elements. The singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises” , “comprising” , “has” , “having” , “includes” and/or “including” as used herein, specify the presence of stated features, elements, and/or components and the like, but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. The term “based on” is to be read as “based at least in part on” . The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment” . The term “another embodiment” is to be read as “at least one other embodiment” . Other definitions, explicit and implicit, may be included below.

In the following, various embodiments of the present disclosure will be described with reference to the accompany figures.

As introduced in the background, taking Figure 2 as an example, heatsink 207 has the highest CTE as 23 ppm, conveying its tension to the radio board 205, causing the radio board 205 to expand more than it should under CTE 14 ppm. As a result, the ceramic filter is stretched by the tension transmitted from the small PCB 203, which gets a bit stretched by the radio board 205. If the ceramic filter is replaced by metal filter which has higher extensibility, this will be no problem from the CTE difference. However, since dielectric filters contribute smaller size and higher performance to radio products, and ceramic waveguide filter is one of the most popular dielectric filters, efforts need to be taken considering fragility of ceram when putting ceramic waveguide filter into use.

To satisfy the growing needs of dielectric filter in radio products, the disclosure provides a solution to mitigate expansion brought from a radio board connected to the dielectric filter.

Specifically, this disclosure provides a filter unit and a radio node including the filter unit. The filter unit comprises a dielectric filter, a bracket with a seating and multiple pins soldered with the dielectric filter. The radio node comprises the filter unit and a radio board soldered with seating of the bracket. With the bracket, tension conducted from the radio board expansion caused by temperature rising can be offset by the deformation of the pins. The dielectric filter can be protected from being cracked.

According to an embodiment of the disclosure, a filter unit is provided, comprising a dielectric filter and a bracket. The bracket comprises a seating and more than one pins raising from one side of the seating. Further, the more than one pins are soldered with a surface of the dielectric filter, and the other side of the seating is to be soldered with a printed circuit board. The bracket can be made of metal, or any other material with well electric conductivity.

According to an embodiment of the disclosure, a radio node is provided, comprising a dielectric filter, a bracket and a radio board connected to the dielectric filter. The bracket includes a seating and multiple pins, where the seating is mounted on a surface of the radio board, and the pins raise from the other side of the seating and soldered with a surface of the dielectric filter. For simplicity, ceramic waveguide filter as a popular dielectric filter is mentioned hereinafter.

Figure 3 illustrates a side profile of the structure of the radio node. A ceramic filter 301 is soldered with pins of a bracket 303 through solder tin 302. Side profile of the bracket 303 looks like a comb with its broaches as the pins soldered with the ceramic filter 301, and its back as seating part soldered with a radio PCB 306. Next to the other side of the radio PCB 306 is a heatsink 307 fixed to the radio PCB 306 via at least one screw 305.

When temperature rises, the radio board begins to expand, and the seating of the bracket mounted on the surface of the radio board expands with it. Referring to Figure 4 still an illustration of side profile of the structure, a radio board 406 generates heat which not only expanding the radio board 406 itself, but a heatsink 407 which expands faster than the radio board 406 because of its higher CTE. Since the heatsink 407 is fixed to the radio board 406 via several screws 405, it pulls the radio board 406 more than the radio board 406 expanded by the heat. On the other side of the radio board is a bracket 403 with its seating mounted on the radio board 406. Because the bracket 403 is made of metal which has higher malleability, or even the bracket 403 is made of electroconductive plastics, it still has higher malleability, the seating can be easily expanded with the radio board 406. However, a ceramic filter 401 sitting on the pins of the bracket, would not be stretched by the tension brought from expansion of the radio board. Instead, deformation of the pins provides tolerance of CTE differentiation between materials.

Readers can see from Figure 4 that the pins of the bracket 403 bend or lean “inside” with their “heads” stick to the ceramic filter 401 through solder paste 402 and their bases, the seating, stick to the radio board 406 through solder layer 404. In such cases, the ceramic filter 401 won’t get crack by the tension brought from heating-up materials with a larger CTE. Similarity, with the bracket substituting the substrate, a small PCB, between the radio board and the ceramic filter, when temperature drops, the “broaches” of the “comb” can deform back to offset different shrinkages between the ceramic filter and the radio board, so that the ceramic filter and its resonators won’t get deformed by external force from a PCB next to it. Therefore, performance of the ceramic filter won’t get affected by the external force.

In some embodiments, the pins can be soldered on the seating of the bracket. The seating of the bracket can be flat so as to be mounted on a surface of a radio board. A pin with its two ends soldered respectively with the ceramic filter and the seating. With environment temperature changing, the bracket deforms with it, for example, direction of those pins changes with the temperature, providing offset of expansion or shrinkage differences between the radio board and the ceramic filter.

In some embodiments, the pins and the seating form an integrated body. Compared with the embodiment that the pins being soldered on the seating, the joints between the pins and the seating might be more tolerant. An embodiment shows a manufacturing process of a bracket. Figures 5a to 5c illustrate steps of the process.

Firstly, a metal sheet is designed and cut out. In an example provided in Figure 5a, several rectangle blocks 501 are designed in a flat metal sheet 500. Then, three sides of each rectangle block 501 are cut away from the flat sheet, the fourth side remaining as it is.

In a next step as shown in Figure 5b, to stamp the rectangle blocks 501 from one side of the sheet, so that the rectangle blocks can fold at the fourth side, and become pins 501’ arising from the sheet. The side opposite to the remaining fourth side of the rectangular becomes head of a pin to be soldered with a ceramic filter in later process. The remaining sheet become seating of the bracket to be soldered with a radio board. The flat sheet 500 now become a bracket 500’ comprising the seating and the pins.

Alternatively, the flat sheet can also be made of electroconductive plastics, which not only has high extensibility, but nice elasticity. Therefore, the pins might be easier to be folded during the stamping process, and has longer life for changing its direction caused by the tension of its neighboring materials.

In a next step as shown in Figure 5c, to assemble a ceramic filter 510 on the bracket 500’ via the pins, with soldering tin 520 in-between. Surface of the ceramic filter is often plated with a silver layer thus easy to be soldered with the pins of the bracket 500’. The bracket 500’ is then assembled on a radio board with a heatsink. Figure 5c is just an example of assembling the bracket, and the sequence of these steps is not limited to the embodiment mentioned above.

In an embodiment, since signals need be input via a resonator of the ceramic filter and then output from the filter, if the input and output interface of the ceramic filter is on the same side of the one soldered with the bracket, an input and an output passage should also be made in the bracket. As shown in Figure 5a, two circles 503 are designed and several gaps have been cut from the center of the circles. Then, the circles 503 and rectangles are stamped from a same side in Figure 5b, forming an input and output passages 503’ for signals transmitted from and to the ceramic filter. Note that the shape and position of the passages 503’ is only diagrammatic sketch and the skilled should well know how to form those passages for in-an-out signals, and it is preferred to have those passages as radiation shield of the signal waves.

In another embodiment, in order to make it easier for the assembling between the filter and the bracket, at least one side of the sheet is designed to fold in order for positioning the ceramic filter. As an example, shown in Figure 5a and 5d, strips 502 are formed at two opposite sides of the sheet, and then folded towards the same direction with the pins, as two fringes 502’ to locate the filter. As shown in Figure 5d, the fringes 502’ have two-stage folder, with the lower folder in a same level with the pins, and the higher level enfolding the ceramic filter at its edge.

In another embodiment, in order to make it easier for the stamping process, and ensure the rectangular regions in the flat sheet can be easier folded at a wanted position to keep the pins at a same length, a shallow slot can be milled on a surface of the rectangle, as also shown in Figure 5a. The stamping is then performed at the other surface of the sheet and the rectangles are folded at the slots.

In another embodiment, the shape of the pins is not limited to the above embodiments. For example, with the design on the flat metal sheet, T-style shape with the head to be soldered with the ceramic filter and the tail to be folded at the seating, can be stamped and folded as the pins, so that the contact region of the pins is larger than that of the rectangular pins in previous embodiments. In another example, a curving strip is designed and stamped as a bent pin, so that the tolerance provided by the bracket might be higher than that of the rectangular pins during the expansion by the heat. A skilled can think of any shape of the pins of the bracket that can provide tolerance to offset different expansion from the materials with various CTEs.

References in the present disclosure to “an embodiment” , “another embodiment” and so on, indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to implement such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

The present disclosure includes any novel feature or combination of features disclosed herein either explicitly or any generalization thereof. Various modifications and adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-Limiting and exemplary embodiments of this disclosure.

Claims

A filter unit, comprising:

a dielectric filter and a bracket;

wherein the bracket comprises a seating and more than one pins raising from one side of the seating;

wherein the other side of the seating is to be soldered with a printed circuit board; and wherein the more than one pins are soldered with a surface of the dielectric filter.
The filter unit of claim 1, wherein the pins and the seating are an integrated.
The filter unit of claim 1, wherein the pins are soldered on the seating.
The filter unit of any of claims 1 to 3, wherein the pins are shaped in any of: straight strip, or T-style, curving strip.
The filter unit of any of the preceding claims, wherein the bracket further comprises an input and output passage which raises from the seating at the same side of the pins.
The filter unit of any of the preceding claims, wherein the bracket has at least one edge with a fringe folded towards the same direction as the pins, wherein the fringe enfolds the filter at its edge.
The filter unit of any of the preceding claims, wherein the bracket is made of metal or electroconductive plastics.
The filter unit of any of the preceding claims, wherein the dielectric filter is a ceramic waveguide filter.
A radio node, comprising:

a dielectric filter, a bracket and a radio board connected to the dielectric filter; wherein the bracket comprises a seating and multiple pins raising from one side of the seating;

wherein the seating is mounted on a surface of the radio board with the other side of the seating;

wherein the multiple pins are soldered with a surface of the dielectric filter.
The radio node of claim 9, wherein the pins and the seating are an integrated.
The radio node of claim 9, wherein the pins are soldered on the seating.
The radio node of any of claims 9 to 11, wherein the pins are shaped in any of: straight strip, or T-style, curving strip.
The radio node of any of claims 9 to 12, wherein the bracket further comprises an input and output passage which raises from the seating at the same side of the pins, wherein electric lines connected the filter to the radio board are put inside of the input and output passage.
The radio node of any of claims 9 to 13, wherein the bracket is made of metal or electroconductive plastics.