KR20230173816A - Manufacturing method for surface mount type dielectric filter - Google Patents

Abstract

The present invention relates to a method of manufacturing a dielectric filter for surface mounting, comprising the steps of a) preparing ceramic powder, b) mixing ceramic powder and amorphous thermoplastic resin and press molding to form a hexahedral body of the filter; , c) firing the molded body, and d) forming a silver coating on the front of the fired body, and then removing the silver coating around the input end and the output end.

Description

{Manufacturing method for surface mount type dielectric filter}

The present invention relates to a method of manufacturing a surface-mounted dielectric filter, and more specifically, to a method of manufacturing a 3.5GHz dielectric filter for 5G mobile communication that can be directly mounted on a PCB.

Recently, mobile communication systems require higher transmission capacity to provide various cutting-edge services such as IoT (Internet of Things), V2X (Vehicle to X), and holograms. Accordingly, more bandwidth is required in mobile communication systems, but it has become difficult to accommodate the required transmission capacity due to bandwidth limitations in the existing microwave band. Therefore, in recent mobile communication systems, technology that utilizes millimeter waves with a wavelength in millimeters has been emerging to overcome limited frequency resources.

In order to process these millimeter wave signals, a waveguide filter, which is mainly used in technological fields such as radar systems and satellite communications, is used rather than a so-called 'comeline' structure filter mainly used in the existing microwave band. It is more advantageous than this. Waveguide filters have excellent loss characteristics in high frequency bands and are easier to implement than comb-line structured filters.

A waveguide filter is a filter that transmits energy through a waveguide using a resonance phenomenon caused by a shielded space, that is, the waveguide structure itself. The waveguide, which is roughly in the shape of a tube, is designed to have a length corresponding to the filtering frequency characteristics.

These waveguide filters can be classified into types and uses depending on the dielectric that fills the waveguide.

Registered Patent No. 10-2339254 (registered on December 9, 2021, dielectric waveguide filter) describes a dielectric waveguide filter and includes an input terminal and an output terminal where the input port and output port are connected.

Coaxial cables are connected to the input port and output port, and since the connectors for coaxial cable connections are connected manually, there is a problem in that manufacturing costs increase and productivity decreases.

In addition, the above registered patent describes filters of various structures, but they commonly include a slit structure formed from a portion of the outer surface to the inner side.

Although the resonance frequency characteristics, etc. are determined by this slit structure, structurally angled parts increase, and when manufacturing ceramic powder by firing, it is possible to predict the problem of lower yield due to an increase in right-angled parts.

In relation to the manufacturing of conventional dielectric filters, Patent No. 10-0906215 (registered on June 29, 2009, manufacturing method of TE mode dielectric filter) describes a manufacturing method of a dielectric waveguide that has a uniform shape and is suitable for mass production. there is.

More specifically, a method of mixing ceramic raw materials and a polymer binder, injection molding using a ceramic material in the form of pellets, and then removing the binder is used.

However, in the conventional method, to form a ceramic base in the form of pellets, organic binders, secondary binders, plasticizers, surfactants, lubricants and solvents are added and mixed, then mixed with ceramic raw material powder, and then cut to produce pellet-shaped ceramics. Since the material is manufactured, it is possible to predict the increase in process steps due to the addition of the pellet manufacturing process, the increase in manufacturing costs due to the increase in process steps, and the problem of difficulty predicting changes in high-frequency characteristics after removing the binder can be predicted. there is.

The problem to be solved by the present invention, taking into account the problems of the prior art as described above, is to provide a method of manufacturing a filter without using pellets.

In addition, the present invention provides a method of manufacturing a filter with a structure that can be directly surface mounted on a substrate without using a coaxial wire.

The surface-mounted dielectric filter manufacturing method of the present invention to solve the above technical problems includes a) preparing ceramic powder, and b) mixing ceramic powder and amorphous thermoplastic resin and press molding to form a hexahedral shape of the filter. It may include the steps of forming a body, c) firing the molded body, and d) forming a silver coating on the front of the fired body, and then removing the silver coating around the input end and the output end.

In an embodiment of the present invention, the body in the shape of a hexahedron has a first slit formed to be long in the vertical direction at the center of the body, and disposed between the center side of the first slit and the side of the body and formed to be long in the horizontal direction. It may include a second slit, an input terminal and an output terminal located on the edge of the body in a position symmetrical about the second slit, and a plurality of cavity resonators formed with a predetermined diameter and depth on the upper surface of the body. .

In an embodiment of the present invention, the ceramic powder of step a) may exhibit characteristics such as a dielectric constant of 20.8, a loss tangent of 1.7e-4, and a Q value of 6000 after sintering.

In an embodiment of the present invention, the ceramic powder may have an average particle diameter of 60 to 100 μm.

In an embodiment of the present invention, the ceramic powder may have an average particle diameter of 73.2㎛.

In an embodiment of the present invention, the ceramic powder may have a bulk density of 0.8 to 1.2 g/cm ³ .

In an embodiment of the present invention, the ceramic powder may have a bulk density of 1.04 g/cm ³ .

In an embodiment of the present invention, the ceramic powder may have a moisture content of less than 1.5%.

In an embodiment of the present invention, the ceramic powder may have a moisture content of 0.12%.

In an embodiment of the present invention, after step c), a step of polishing the surface of the fired body may be further included.

The present invention can manufacture a dielectric filter without using ceramic materials in the form of pellets, thereby reducing manufacturing costs by minimizing process steps, and improving the particle characteristics, molding characteristics, sintering characteristics, and electrical characteristics after sintering of the ceramic powder. In consideration of this, by providing a structure that can be directly mounted on the PCB at the input and output terminals, there is an effect of reducing manufacturing costs and improving productivity because manual connector connection of coaxial cables is not required.

In addition, the present invention has the effect of minimizing the number of angled parts (number of edges) of the ceramic body by changing the shape of the slit portion, thereby preventing a decrease in yield during the firing process of ceramic powder.

1 is a flowchart of a dielectric filter manufacturing process according to a preferred embodiment of the present invention.
Figure 2 is a perspective view of a dielectric filter manufactured according to the present invention.
Figure 3 is a plan view of Figure 2.
Figure 4 is a bottom view of Figure 1.
Figure 5 is a graph of temperature change in the sintering process used in the present invention.
Figure 6 is an exemplary diagram of a PCB on which a dielectric filter manufactured according to the present invention is mounted on the surface.
Figure 7 is an exemplary diagram of the dielectric filter manufactured according to the present invention in a mounted state.
Figures 8 and 9 are characteristic graphs of the dielectric filter manufactured according to the present invention, respectively.

In order to fully understand the configuration and effects of the present invention, preferred embodiments of the present invention will be described with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various forms and various changes can be made. However, the description of this embodiment is provided to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the present invention of the scope of the invention. In the attached drawings, components are shown enlarged in size for convenience of explanation, and the proportions of each component may be exaggerated or reduced.

Terms such as 'first' and 'second' may be used to describe various components, but the components should not be limited by the above terms. The above terms may be used only for the purpose of distinguishing one component from another. For example, the 'first component' may be named 'the second component' without departing from the scope of the present invention, and similarly, the 'second component' may also be named 'the first component'. You can. Additionally, singular expressions include plural expressions, unless the context clearly dictates otherwise. Unless otherwise defined, terms used in the embodiments of the present invention may be interpreted as meanings commonly known to those skilled in the art.

Hereinafter, a method for manufacturing a dielectric filter according to a preferred embodiment of the present invention will be described in detail with reference to the drawings.

1 is a flowchart of the manufacturing process of a dielectric filter according to a preferred embodiment of the present invention.

Referring to FIG. 1, a step of preparing ceramic powder (S10), mixing ceramic powder and an amorphous thermoplastic resin, and compression molding using a mold (S20), and firing the molded body in a furnace, Removing impurities and amorphous thermoplastic resin (S30), performing a polishing process to correct the unevenness of the sintered body (S40), coating the surface of the polished body with silver, and then sintering. It includes (S50) and a step (S60) of removing the silver coating on the input and output terminals.

Hereinafter, the structure and operation of the dielectric filter manufacturing method of the present invention configured as described above will be described in more detail.

First, prepare ceramic powder as in step S10.

Ceramic powder can be used with a bulk density of 0.8 to 1.2 g/cm ³ , and preferably 1.04 g/cm ³ .

The average particle diameter of the ceramic powder can be 60 to 100㎛, and is preferably 73.2㎛.

The above density and average particle size characteristics are for the development of the dielectric constant of 20.8, loss tangent of 1.7e-4, and Q value of 6000 after sintering.

Additionally, the moisture content of the ceramic powder can be less than 1.5%, and is most preferably 0.12%.

In addition, the molding density of the ceramic powder under the above conditions satisfies 2.30 g/cm ³ .

Next, the ceramic powder prepared in step S20 is mixed with the amorphous thermoplastic resin, and a ceramic body is manufactured using a press mold.

The amorphous thermoplastic resin can be PVA (polyvinyl alcohol). PVA is added to prevent ceramic powder damage.

2 to 3 wt% of PVA is mixed with 97 to 98 wt% of ceramic powder, and the body is manufactured by compression molding using a press mold.

An example of a manufactured ceramic body will be described in more detail.

FIG. 2 is a perspective view of a dielectric filter according to a preferred embodiment of the present invention, FIG. 3 is a top view of FIG. 2, and FIG. 4 is a bottom view of FIG.

2 to 4, the dielectric filter manufactured according to the present invention has a body 10 having a hexahedral structure where the length (L) is longer than the width (W) and the height (H) is shorter than the width (W). and a first slit 20 penetrating from the center of the upper surface of the body 10 to the lower surface, a second slit 30 formed in a 90-degree direction with the central part of one side of the first slit 20, and the body ( 10), first to fourth cavities (40, 50, 60, 70) formed at a predetermined depth on the upper surface, and an inductance adjustment cavity (located between the first cavity (40) and the second cavity (50)) 80, and an input terminal 91 and an output terminal 92 located on the body 10 on the left and right sides of the second slit 30.

In step S20, the shape of the body 10 is manufactured.

The body 10 has the shape of a flat rectangular parallelepiped.

The body 10 has a first slit 20 and a second slit 30 formed through the top and bottom surfaces.

The first slit 20 is formed long in the horizontal direction in a plan view, and the second slit 30 is formed long in the vertical direction.

The first slit 20 has a first length L1 and a second width W1 and is located in the horizontal direction at the center of the upper surface of the body 10.

The first length L1 of the first slit 20 may be 50 to 60% of the length L of the body 10.

The first slit 20 is intended to form the body 10 into a folded wave guide, and the body 10 around the first slit 20 is formed from the input end 91 to the output end 92. A waveguide is formed accordingly.

At this time, the second slit 30 is located at the boundary between the start and end of the waveguide.

That is, the second slit 30 is a long hole-shaped slit located in the center of the input terminal 91 and the output terminal 92, and the beginning and end of the curved waveguide are divided by this boundary.

A first cavity 40 is located between the input end 91 and the second slit 30, and a fourth cavity 70 is located between the second slit 30 and the output end 92.

The first to fourth cavities 40, 50, 60, and 70 are cavity-type resonators, and the resonance frequency is determined by the depth and diameter, respectively. Provides capacitance connecting regions of the body 10 located between the first to fourth cavities 40, 50, 60, and 70 between the first to fourth cavities 40, 50, 60, and 70. do.

More specifically, the first region 11, which is part of the body 10 between the input terminal 91 and the first cavity 40, is connected between the input terminal 91 and the first cavity 40 with a capacitor, and the first region 11 is connected between the input terminal 91 and the first cavity 40 with a capacitor. The second region 12, which is a part of the body 10 between the first cavity 40 and the second cavity 50, acts as a capacitor for adjacent resonator coupling. Likewise, the third region 13, which is a part of the body 10 between the third cavity 60 and the fourth cavity 70, determines the capacitance between the third cavity 60 and the fourth cavity 70.

Additionally, the fourth region 14 located between the fourth cavity 70 and the output terminal 92 forms the capacitance of the filter output terminal.

At this time, in the structure of the body 10, which is a bent waveguide, frequency blocking is required between the input end 91 and the output end 92, and for this purpose, a block is required between the first slit 20 and the second slit 30. The fifth region 15 located there acts as a cross-coupling capacitor.

By forming the fifth region 15, the body 10 of the present invention can form a curved waveguide without forming a slit communicating from the outer surface of the body to the center as in the prior art.

Therefore, there are no angled areas except for the four corners on the plane of the body 10, and this structure minimizes the possibility of defects occurring when forming angled parts in the ceramic firing process, preventing a decrease in yield. There will be.

In addition, the second cavity 50 and the third cavity 60 must be connected to each other by an adjacent coupling inductor, and for this purpose, the inductance adjustment cavity 80 is used.

The inductance adjustment cavity 80 can adjust the inductance by adjusting the diameter and depth of the cavity.

In this way, the present invention makes it possible to implement a resonator filter without using a slit that communicates the shape of the body 10 from the side to the center.

After manufacturing the body 10 of this shape, it is fired as in step S30.

By firing, the added amorphous thermoplastic resin is removed and impurities are also removed. By firing, the dielectric constant value and quality factor value of the ceramic dielectric can be obtained.

Figure 5 is a graph of the firing temperature profile during the firing process in step S30.

Referring to Figure 5, the present invention includes a first temperature increase step (S31), a first temperature maintenance step (S32), a second temperature increase step (S33), a second temperature maintenance step (S34), a third temperature increase step (S35), It consists of a third temperature maintenance step (S36).

In the first temperature raising step (S35), the molded body 10 is heated to 200 to 230° C. for 60 to 70 minutes. The first temperature increase step (S35) involves raising the temperature over a relatively short period of time, and the temperature increase slope is more rapid than that of the second temperature increase step (S33) or the third temperature increase step (S35).

In the first temperature maintenance step (S32), the temperature of the first heated body 10 is maintained in the range of 200 to 230° C. for 180 to 200 minutes.

In the second temperature raising step (S33) after the first temperature maintaining step (S32), the temperature of the body 10 is raised to 490 to 510°C. The second temperature raising step (S33) is performed for about 130 to 140 minutes.

Next, in the second temperature maintenance step (S34), the temperature of the body 10 is maintained at 490 to 510°C for about 40 to 50 minutes.

Next, in the third temperature raising step (S35), the temperature of the body 10 is raised to 1350 to 1360°C for 230 to 240 minutes, and the body 10 is fired by maintaining the temperature for about 230 to 250 minutes as in the third temperature maintaining step (S36).

With this firing, the dielectric constant of the body 10 is 20.8 at 1 MHz and 1 Vrms, the Q value is 5945, and the Tf is 8.5 under the same conditions.

Next, in step S40, the fired body 10 is machined.

Step S40 can be selectively performed only when surface uniformity is reduced due to shrinkage during firing.

Since the body 10, which is a ceramic sintered body, has high hardness and is brittle, a polishing process is performed to prevent breakage or microcracks.

After performing the polishing process, silver (Ag) is printed on the front surface of the body 10 using a screen printing method in step S50.

At this time, the clearance for stable plate separation, the angle of the squeegee for discharging the silver paste, the squeegee speed that affects the speed of silver paste discharge and plate separation, and the squeegee pressure to scrape off the silver paste on the screen are appropriately maintained.

The silver-coated body 10 is sintered and hardened.

Next, as in step S60, some of the silver coated on the body 10 is removed to expose the ceramic body around the input and output terminals.

Referring again to FIG. 4, in the present invention, the input terminal 91 and the output terminal 92 formed on the body 10 are each composed of circular holes, and are directly surface mounted on the PCB.

To this end, dielectric exposed areas 94 and 96 on which the silver (Ag) coating has been removed are formed around each of the input terminal 91 and the output terminal 92 on the bottom side of the body 10.

Therefore, the mounting areas 93 and 94 where the silver coating remains are formed around the holes of the input terminal 91 and the output terminal 92 and in the portion extending from the input terminal 91 and the output terminal 92 to the side of the body 10. It is located.

The shape of each of the mounting areas 93 and 94 includes a circular part surrounding the entire circumference of the hole that is the input terminal 91 and the output terminal 92, and a circular portion connected to the circular portion to form the center of the dielectric exposed area 94 and 96. It consists of a straight part that passes through and reaches the side of the body 10.

Due to this structure, the dielectric filter manufactured according to the present invention can be directly mounted on a PCB.

Figure 6 is an exemplary diagram of a PCB on which the dielectric filter manufactured according to the present invention can be mounted, and Figure 7 is an exemplary diagram of a state in which the dielectric filter manufactured according to the present invention can be mounted on the PCB.

In this way, the present invention can be mounted directly on the PCB (1) without the need to connect coaxial cables to the input terminal (91) and output terminal (92), eliminating the need for manual connector assembly and shortening the manufacturing process time. And costs can be reduced.

Figures 8 and 9 show the results of analyzing the characteristics of the surface-mounted dielectric filter manufactured according to the present invention, respectively.

Figure 8 shows the reflection coefficient and transmission coefficient specification of the present invention, and the pass band is 3500 to 3600 MHz and the reflection loss is 19 dB, showing very good characteristics.

Additionally, Figure 9 shows the insertion loss characteristics of the present invention. The present invention is directly surface mounted on a PCB without using a coaxial cable, and the insertion loss at this time is 0.7dB, showing very good characteristics.

In this way, the present invention can manufacture a ceramic dielectric filter without forming a pellet, and can be expected to improve productivity and reduce costs by shortening the manufacturing process.

Although embodiments according to the present invention have been described above, they are merely illustrative, and those skilled in the art will understand that various modifications and equivalent scope of embodiments are possible therefrom. Therefore, the true technical protection scope of the present invention should be determined by the following claims.

10: Body 11: Area 1
12:Second area 13:Third area
14: Area 4 15: Area 5
20: first slit 30: second slit
40: 1st cavity 50: 2nd cavity
60: 3rd cavity 70: 4th cavity
80: Inductance adjustment cavity 91: Input terminal
92:Output stage

Claims (10)

a) preparing ceramic powder;
b) mixing ceramic powder and amorphous thermoplastic resin and press molding to form a hexahedral body of the filter;
c) firing the molded body; and
d) A dielectric filter manufacturing method including forming a silver coating on the front surface of the fired body and then removing the silver coating around the input and output terminals. According to paragraph 1,
The body in the shape of a hexahedron,
A first slit formed longitudinally in the center of the body;
a second slit disposed between the center of the first slit and a side of the body and extending horizontally;
an input terminal and an output terminal located on an edge side of the body in a position symmetrical about the second slit; and
A dielectric filter manufacturing method comprising a plurality of cavity resonators formed with a predetermined diameter and depth on the upper surface of the body. According to paragraph 1,
The ceramic powder of step a) is,
A dielectric filter manufacturing method characterized by a dielectric constant of 20.8, a loss tangent of 1.7e-4, and a Q value of 6000 after sintering. According to paragraph 2,
The ceramic powder is,
A method of manufacturing a dielectric filter, characterized in that the average particle diameter is 60 to 100㎛. According to paragraph 2,
The ceramic powder is,
A dielectric filter manufacturing method characterized by an average particle diameter of 73.2㎛. According to paragraph 2,
The ceramic powder is,
A method of manufacturing a dielectric filter, characterized in that the bulk density is 0.8 to 1.2 g/cm ³ . According to paragraph 2,
The ceramic powder is,
A dielectric filter manufacturing method characterized in that the bulk density is 1.04g/cm ³ . According to paragraph 2,
The ceramic powder is,
A method of manufacturing a dielectric filter, characterized in that the moisture content is less than 1.5%. According to paragraph 2,
The ceramic powder is,
A method of manufacturing a dielectric filter, characterized in that the moisture content is 0.12%. According to paragraph 2,
After step c) above,
A dielectric filter manufacturing method further comprising polishing the surface of the fired body.

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