A low-pass filter and a manufacturing method thereof

Abstract

The low-pass filter provided by the present invention includes a middle layer board and outer layer boards located on the upper and lower sides of the middle layer board. Copper layers are coated on the upper and lower surfaces of the middle layer board and the surfaces of the outer layer boards facing each other. By providing an annular strip-shaped exposed area in the middle of the copper layer coated on the outer layer board, the copper layer in the annular strip-shaped exposed area can be used to form a signal copper layer. By opening a through groove in the middle of the middle layer board to avoid the signal copper layer, when the middle layer board and the outer layer boards are welded together with solder paste, a cavity can be formed between the inner wall of the through groove and the surface of the outer layer board facing each other, so that the signal copper layer is exposed to the air in the cavity, without affecting the conductivity of the signal copper layer, making the insertion loss of the low-pass filter low and the applicable range wide. The manufacturing method provided by the present invention is connected by solder paste welding, with simple operation, easy implementation and high yield rate. By opening a through groove in the middle layer board to avoid the signal copper layer, the conductivity of the signal copper layer is not affected, and the low-pass filter manufactured has low insertion loss and a wide applicable range.

Description

Technical Field

[0001] This application relates to the field of electronic communication devices, and particularly relates to a low-pass filter and a manufacturing method thereof. Background Art

[0002] With the development of 5G communication, the communication industry has entered an era of great explosion. The demand for low-pass filters has increased sharply. Most of the existing low-pass filters are made by laying copper layers on two PCB boards and placing a PP sheet between these two PCB boards for lamination. The melting of the PP sheet during lamination is used for bonding. Since the PP sheet will adhere to the signal copper layer when melting, the conductivity of the signal copper layer is reduced, resulting in a large insertion loss of the low-pass filter. As a key electrical performance index of the low-pass filter, how to reduce the insertion loss of the low-pass filter is an important task for each filter manufacturer. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a low-pass filter with low insertion loss and wide application range. The present invention also provides a manufacturing method of a low-pass filter. This method is simple to operate, easy to implement, and has a high yield rate. The manufactured low-pass filter has low insertion loss and wide application range.

[0004] To achieve the above purpose, the product in the technical solution provided by the present invention is a low-pass filter, including a middle layer board and outer layer boards located on the upper and lower sides of the middle layer board. Copper layers are laid on the upper and lower surfaces of the middle layer board and the surfaces of the outer layer boards facing each other. It is characterized in that:

[0005] A ring-shaped exposed area is provided in the middle of the copper layer laid on the outer layer board, and the copper layer within the ring-shaped exposed area forms a signal copper layer;

[0006] A through groove is opened in the middle of the middle layer board, penetrating the middle layer board and the copper layer laid on the surface of the middle layer board in the up and down direction. The through groove is used to avoid the signal copper layer;

[0007] The copper layers laid on the middle layer board and the outer layer board are welded into one body by solder paste, so that the inner wall of the through groove and the surface of the outer layer board facing each other enclose a cavity, and the signal copper layer is exposed to the air within the cavity.

[0008] Preferably, the edge of the through groove is in contact with the outer edge of the ring-shaped exposed area.

[0009] Preferably, the material of the outer layer board is a PCB board or a metal board, and the material of the middle layer board is a PCB board.

[0010] Preferably, a shielding copper layer is deposited on the surface of the outer layer board on the opposite side, and two spaced circular ring-shaped exposed areas are provided on the shielding copper layer, and the shielding copper layer within the circular ring-shaped exposed areas constitutes the input and output interfaces of the low-pass filter.

[0011] Further preferably, the input and output interfaces are directly connected to the signal copper layer, or the input and output interfaces are connected to the signal copper layer through the metallized holes on the middle layer board.

[0012] Preferably, the insertion loss of the low-pass filter is -0.0829 dB at 3.4 GHz and -0.1410 dB at 3.8 GHz.

[0013] In order to achieve the above object, the method in the technical solution provided by the present invention is a method for manufacturing a low-pass filter, including the following steps:

[0014] A Place two outer layer boards on the upper and lower sides of the middle layer board respectively, and deposit copper layers on the surfaces of the outer layer boards on the opposite side and the upper and lower surfaces of the middle layer board. Among them, a ring-shaped exposed area is provided in the middle of the copper layer deposited on the upper surface of the outer layer board located on the lower side of the middle layer board, and the copper layer within the ring-shaped exposed area constitutes the signal copper layer;

[0015] B Solder the copper layers deposited on the upper and lower surfaces of the middle layer board and the opposite side surfaces of the outer layer board into one body to obtain a low-pass filter;

[0016] Between step A and step B, there is also a step of opening a through groove on the middle layer board that penetrates the middle layer board and the copper layer deposited on the surface of the middle layer board in the up and down direction, and using the through groove to avoid the signal copper layer; in step B, the inner wall of the through groove and the upper and lower surfaces of the outer layer board enclose a cavity, and the signal copper layer is exposed to the air within the cavity to reduce the insertion loss.

[0017] Preferably, between step A and step B, there is also a step of depositing a shielding copper layer on the surface of the outer layer board on the opposite side, and two spaced circular ring-shaped exposed areas are provided on the shielding copper layer, and the shielding copper layer within the circular ring-shaped exposed areas constitutes the input and output interfaces of the low-pass filter.

[0018] Further preferably, the input and output interfaces are directly connected to the signal copper layer, or the input and output interfaces are connected to the signal copper layer through the metallized holes on the middle layer board.

[0019] Preferably, the lower edge of the through groove is in contact with the outer edge of the ring-shaped exposed area.

[0020] Preferably, in step A, the material of the outer layer board is a PCB board or a metal board, and the material of the middle layer board is a PCB board.

[0021] Preferably, the insertion loss of the low-pass filter at 3.4 GHz is -0.0829 dB, and the insertion loss at 3.8 GHz is -0.1410 dB.

[0022] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0023] The low-pass filter provided by the present invention includes a middle layer board and outer layer boards located on both the upper and lower sides of the middle layer board. Copper layers are plated on the upper and lower surfaces of the middle layer board and the surfaces of the outer layer boards facing each other. By setting a ring-shaped exposed area in the middle of the copper layer plated on the outer layer board, the copper layer in the ring-shaped exposed area can be used to form a signal copper layer. By opening a through groove in the middle of the middle layer board that penetrates the middle layer board and the copper layer plated on the surface of the middle layer board in the up and down direction, the signal copper layer is avoided. When the copper layers plated on the middle layer board and the outer layer board are welded together with solder paste, a cavity can be formed between the inner wall of the through groove and the surface of the outer layer board facing each other, so that the signal copper layer is exposed to the air in the cavity, without affecting the conductivity of the signal copper layer, making the insertion loss of the low-pass filter low and the applicable range wide. The manufacturing method of the low-pass filter provided by the present invention is connected by solder paste welding, with simple operation, easy implementation, and high yield. By opening a through groove on the middle layer board to avoid the signal copper layer, the conductivity of the signal copper layer is not affected, making the manufactured low-pass filter have low insertion loss and a wide applicable range. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 is a three-dimensional exploded view of the first embodiment of the low-pass filter in the present invention.

[0026] Figure 2 is Figure 1 the bottom view of the middle and lower layer board.

[0027] Figure 3 is a three-dimensional exploded view of the second embodiment of the low-pass filter in the present invention.

[0028] Figure 4 is the performance diagram of the low-pass filter in the prior art.

[0029] Figure 5 is Figure 1 The performance diagram of the low-pass filter

[0030] Wherein: 10. upper layer board; 20. middle layer board; 21. through slot; 22. metallized hole; 30. lower layer board; 31. annular bare area; 32. signal copper layer; 33. circular bare area; 41. copper layer; 42. shielding copper layer Specific embodiments

[0031] Next, the technical solutions in the embodiments of the present invention will be described in detail with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention

[0032] The up and down directions described in the present invention are Figure 1 The up and down directions in

[0033] Embodiment 1

[0034] As Figure 1-2 shown, the low-pass filter provided by the present invention includes a middle layer board 20 and outer layer boards located on the upper and lower sides of the middle layer board 20. The outer layer board on the upper side of the middle layer board 20 is the upper layer board 10, and the outer layer board on the lower side of the middle layer board 20 is the lower layer board 30. The lower surface of the upper layer board 10, the upper and lower surfaces of the middle layer board 20, and the upper surface of the lower layer board 30 are all coated with a copper layer 41. In the middle of the copper layer 41 coated on the upper surface of the lower layer board 30, there is an annular bare area 31, and the copper layer 41 within the annular bare area 31 constitutes a signal copper layer 32; a through slot 21 is opened in the middle of the middle layer board 20 and penetrates through the middle layer board 20 and the copper layer 41 coated on the upper and lower surfaces of the middle layer board 20. The through slot 21 is used to avoid the signal copper layer; the copper layers 41 on the upper layer board 10, the middle layer board 20, and the lower layer board 30 are welded together by solder paste, so that a cavity is formed between the inner wall of the through slot 21 and the lower surface of the upper layer board 10 and the upper surface of the lower layer board 30, and the signal copper layer 32 is exposed to the air within this cavity

[0035] The advantage of such a setting is that it can not affect the conductivity of the signal copper layer 32, resulting in low insertion loss and wide application range of this low-pass filter

[0036] In this embodiment, the lower slot edge of the through slot 21 is in contact with the outer edge of the annular bare area 31. The advantage of such a setting is that it can ensure the bonding effect of the upper layer board 10, the middle layer board 20, and the lower layer board 30 to the greatest extent while avoiding affecting the conductivity of the signal copper layer 32

[0037] For material selection convenience, in this embodiment, the upper layer board 10 is a PCB board or a metal board, and the lower layer board 30 and the middle layer board 20 are PCB boards.

[0038] To improve the shielding effect, in this embodiment, shielding copper layers 42 are coated on the upper surface of the upper layer board 10 and the lower surface of the lower layer board 30. For signal connection convenience, two spaced-apart circular ring-shaped exposed areas 33 are provided on the shielding copper layer 42 on the lower surface of the lower layer board 30. The shielding copper layer 42 within the circular ring-shaped exposed areas 33 constitutes the input and output interfaces of this low-pass filter, and this input and output interface is directly connected to the signal copper layer 32.

[0039] As Figure 4-5 shown, the insertion loss of this low-pass filter is -0.0829 dB at 3.4 GHz and -0.1410 dB at 3.8 GHz. The insertion loss of a low-pass filter with a traditional structure is -0.2004 dB at 3.4 GHz and -0.2618 dB at 3.8 GHz. Compared with the low-pass filter with a traditional structure, the insertion loss of this low-pass filter is reduced by approximately 0.12 dB.

[0040] Embodiment Two

[0041] As Figure 3 shown, Embodiment Two is basically the same as Embodiment One. The difference lies in that in Embodiment Two, two spaced-apart circular ring-shaped exposed areas 33 are provided on the shielding copper layer 42 on the upper surface of the upper layer board 10. The shielding copper layer 42 within the circular ring-shaped exposed areas 33 constitutes the input and output interfaces of this low-pass filter. Moreover, through holes are opened on the middle layer board 20, and a metal coating is provided on the inner wall of the through holes to form metallized holes 22. The above input and output structure is connected to the signal copper layer on the lower layer board 30 through the metallized holes 22 to achieve signal transmission. In this embodiment, the metallized holes 22 are located within the ring-shaped exposed area 31.

[0042] The advantage of such a setting is that it can adapt to different installation requirements.

[0043] The manufacturing method for manufacturing a low-pass filter provided by the present invention includes the following steps:

[0044] A Place two outer layer boards on the upper and lower sides of the middle layer board respectively, and coat copper layers on the opposite-side surfaces of the outer layer boards and the upper and lower surfaces of the middle layer board. Among them, a ring-shaped exposed area is provided in the middle of the copper layer coated on the upper surface of the outer layer board located on the lower side of the middle layer board. The copper layer within the ring-shaped exposed area constitutes the signal copper layer;

[0045] B Solder the copper layers coated on the upper and lower surfaces of the middle layer board and the opposite-side surfaces of the outer layer boards into one body to obtain a low-pass filter;

[0046] Between step A and step B, there is also a step of opening a through groove on the middle layer board that penetrates through the middle layer board and the copper layer coated on the surface of the middle layer board in the up and down direction, using the through groove to avoid the signal copper layer; in step B, the inner wall of the through groove and the upper and lower surfaces of the outer layer board enclose a cavity, and the signal copper layer is exposed to the air in the cavity to reduce the insertion loss.

[0047] The manufacturing method of the low-pass filter provided by the invention is connected by solder paste welding, with simple operation, easy implementation, and high yield rate. By opening a through groove on the middle layer board to avoid the signal copper layer, it does not affect the conductivity of the signal copper layer, making the manufactured low-pass filter have low insertion loss and a wide application range.

[0048] Preferably, between step A and step B, there is also a step of laying a shielding copper layer on the surface of the outer layer board on the opposite side. There are two spaced circular ring-shaped bare areas on the shielding copper layer, and the shielding copper layer within the circular ring-shaped bare areas constitutes the input and output interfaces of the low-pass filter.

[0049] Further preferably, the input and output interfaces are directly connected to the signal copper layer, or the input and output interfaces are connected to the signal copper layer through the metallized holes on the middle layer board.

[0050] Preferably, the lower groove edge of the through groove is in contact with the outer edge of the circular ring-shaped bare area.

[0051] Preferably, in step A, the material of the outer layer board is a PCB board or a metal board, and the material of the middle layer board is a PCB board.

[0052] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0053] The above are only the specific embodiments of the present application. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present application, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present application.

Claims

1. A low-pass filter, comprising a middle layer board and outer layer boards located on the upper and lower sides of the middle layer board. Copper layers are plated on the upper and lower surfaces of the middle layer board. It is characterized in that: Copper layers are also plated on the surfaces of the opposite sides of the outer layer boards. The copper layers are full-coverage copper layers. An annular strip-shaped exposed area is provided in the middle of the copper layers. The copper layer within the annular strip-shaped exposed area forms a signal copper layer. A through groove is opened in the middle of the middle layer board, penetrating through the middle layer board and the copper layers plated on the surface of the middle layer board in the up and down directions. The edge of the through groove is in contact with the outer edge of the annular strip-shaped exposed area. The through groove is used to avoid the signal copper layer. The copper layers plated on the middle layer board and the outer layer boards are welded into one body by solder paste, so that the inner wall of the through groove and the surface of the opposite side of the outer layer board enclose a sealed cavity, and the signal copper layer is exposed to the air within the sealed cavity, such that the insertion loss of the low-pass filter is -0.0829 dB at 3.4 GHz and -0.1410 dB at 3.8 GHz.

2. The low-pass filter according to claim 1, wherein: The material of the outer layer board is a PCB board or a metal board, and the material of the middle layer board is a PCB board.

3. The low-pass filter according to claim 1, characterized in that: A shielding copper layer is plated on the surface of the opposite side of the outer layer board. Two spaced annular strip-shaped exposed areas are provided on the shielding copper layer. The shielding copper layer within the annular strip-shaped exposed areas forms the input and output interfaces of the low-pass filter.

4. The low-pass filter according to claim 3, wherein: The input and output interfaces are directly connected to the signal copper layer, or the input and output interfaces are connected to the signal copper layer through metallized holes on the middle layer board.

5. A manufacturing method for manufacturing the low-pass filter according to any one of claims 1-4, comprising the following steps: A. Place two outer layer boards on the upper and lower sides of the middle layer board respectively, and plate copper layers on the surfaces of the opposite sides of the outer layer boards and the upper and lower surfaces of the middle layer board. Among them, an annular strip-shaped exposed area is provided in the middle of the copper layer plated on the upper surface of the outer layer board located on the lower side of the middle layer board. The copper layer within the annular strip-shaped exposed area forms a signal copper layer. B. Weld the copper layers plated on the upper and lower surfaces of the middle layer board and the surfaces of the opposite sides of the outer layer boards into one body by solder paste to obtain a low-pass filter. It is characterized in that: Between step A and step B, there is also a step of opening a through groove in the middle layer board, penetrating through the middle layer board and the copper layers plated on the surface of the middle layer board in the up and down directions, and using the through groove to avoid the signal copper layer. In step B, the inner wall of the through groove and the upper and lower surfaces of the outer layer board enclose a cavity, and the signal copper layer is exposed to the air within the cavity to reduce the insertion loss.

6. The manufacturing method of the low-pass filter according to claim 5, characterized in that: Between step A and step B, there is also a step of plating a shielding copper layer on the surface of the opposite side of the outer layer board. Two spaced annular strip-shaped exposed areas are provided on the shielding copper layer. The shielding copper layer within the annular strip-shaped exposed areas forms the input and output interfaces of the low-pass filter.

7. The manufacturing method of the low-pass filter according to claim 6, characterized in that: The input and output interfaces are directly connected to the signal copper layer, or the input and output interfaces are connected to the signal copper layer through metallized holes on the middle layer board.

8. The manufacturing method of the low-pass filter according to claim 5, characterized in that: The lower edge of the through groove is in contact with the outer edge of the annular strip-shaped exposed area.

9. The manufacturing method according to claim 5, characterized in that: In step A, the material of the outer layer board is a PCB board or a metal board, and the material of the middle layer board is a PCB board.

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