CN116835976A

CN116835976A - Dielectric filter forming method, dielectric filter and electronic equipment

Info

Publication number: CN116835976A
Application number: CN202210303254.5A
Authority: CN
Inventors: 齐峰; 黄晓俊; 李梅
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2022-03-25
Filing date: 2022-03-25
Publication date: 2023-10-03

Abstract

The embodiment of the application provides a dielectric filter forming method, a dielectric filter and electronic equipment, wherein the forming method comprises the following steps: mixing ceramic powder, polymerizable substances, a polymerization auxiliary agent and a solvent to form ceramic suspension, injecting the ceramic suspension into a filter die, demolding after the ceramic suspension is polymerized to form gel with a net structure and solidified to form a ceramic pre-blank body, and drying, degreasing, sintering and metallizing the ceramic pre-blank body to obtain the dielectric filter. Because the ceramic suspension has low viscosity and good fluidity, the filter mould can be filled up as fast as water flow, thereby meeting the integral molding requirement of large-size or structural design complex dielectric filter, and the ceramic suspension has lower content of polymer organic matters such as polymerizable substances, polymerization auxiliary agents and the like, and can effectively reduce the time required by degreasing to remove gel process, and remarkably improve the processing efficiency of the dielectric filter.

Description

Dielectric filter forming method, dielectric filter and electronic equipment

Technical Field

The present application relates to the field of filter technologies, and in particular, to a method for forming a dielectric filter, and an electronic device.

Background

The filter is a frequency selective device that passes certain frequency components of the signal while greatly attenuating other frequency components. With the development of communication technology, filters have been widely used in the communication field, which is a key component in a communication system, for example, in the 5G era, the requirements of wireless radio frequency products for the number of antenna elements are increasing, and in order to ensure the communication quality, each element link needs a filter.

At present, the dielectric filter is widely applied to wireless radio frequency products due to the characteristics of small volume, less loss, small temperature coefficient and the like. The dielectric filter is usually a ceramic dielectric filter, and the forming mode is usually a dry-press forming (also called compression forming) mode, that is, the pretreated dry powder is filled into a mould, and pressure is applied to make the dry powder compact, so that the process is simple.

However, as the dielectric filter is changed in the plate structure, the dielectric filter is developed towards the direction of large size or complex structural design, so as to solve the problem of insufficient plate layout area, and the dielectric filter with simple structure can only be formed by using the above method, which cannot meet the integral forming requirement of the large size or complex structural dielectric filter.

Disclosure of Invention

The application provides a dielectric filter forming method, a dielectric filter and electronic equipment, which solve the problem that the existing dry-pressing forming process cannot meet the integral forming requirement of a dielectric filter with large size or complicated structural design.

A first aspect of the present application provides a dielectric filter forming method, the method comprising:

preparing a ceramic suspension, wherein the ceramic suspension at least comprises ceramic powder, a polymerizable substance, a polymerization auxiliary agent and a solvent;

injecting the ceramic suspension into a filter mold, and demolding after the ceramic suspension is polymerized to form gel and solidified to form a ceramic front blank;

drying the ceramic front blank body and then degreasing to remove the gel to form a ceramic blank body;

and sequentially carrying out sintering molding and surface metallization treatment on the ceramic blank to form the dielectric filter.

That is, the ceramic suspension is polymerized to form a gel of a net structure to be solidified after being injected into the mold, and the ceramic powder uniformly distributed in the mold is fixed along with the solidification of the gel, so that a ceramic front blank body is formed. The ceramic suspension has low viscosity and good fluidity, can fill the filter mould as fast and effectively as water flow, and especially can be well filled into the filter mould aiming at a large-size or structural design complex dielectric filter, thereby meeting the integral forming requirement of the large-size or structural design complex dielectric filter.

Moreover, the gel of the network structure is relatively large in volume, the relative content of polymerizable substances, polymeric additives and other high-molecular organic substances in the ceramic suspension is small while the molding requirement is met, the relative content of the gel in the formed ceramic front blank is small, the time required in the degreasing process for removing the gel can be effectively reduced, and the processing efficiency of the dielectric filter is improved. The risk of high molecular substance residue after degreasing treatment is reduced or avoided, and the precision of the dielectric filter is improved.

In addition, the difficulty of injecting and filling the ceramic suspension into the filter mould is low, auxiliary equipment is not needed, the forming method is simple and convenient to operate, and the processing cost can be reduced while the processing efficiency of the dielectric filter is improved. The problems of weld marks, flow lines, burrs and other processing defects of the finished filter caused by insufficient filling can be reduced or avoided, and the precision of the dielectric filter can be guaranteed while the processing efficiency is improved and the processing cost is reduced.

In one possible implementation, the polymerizable species is a monomer and the polymerization aid includes a crosslinking agent, a catalyst, an initiator, and a dispersant.

After the ceramic suspension is injected into the filter die, the initiator can decompose to generate free radicals, the free radicals can polymerize with the monomers to form chain polymers, and the cross-linking agent can continue to polymerize with the chain polymers to form netlike gels, so that the polymerization of polymerizable substances in the die is realized to form curing gels, and the ceramic powder is fixed along with the curing of the gels to obtain ceramic blanks, thereby meeting the molding requirements of the dielectric filter.

In one possible implementation, the preparing a ceramic suspension includes:

mixing the ceramic powder, the dispersing agent, the monomer, the cross-linking agent and the solvent to form a mixed solution;

and adding the catalyst and the initiator into the mixed solution, and mixing to form the ceramic suspension.

That is, when preparing the ceramic suspension, firstly, mixing the monomer, the ceramic powder, the dispersing agent and the cross-linking agent with the solvent to form a mixed solution, and then adding the catalyst and the initiator into the mixed solution to form the ceramic suspension, so that the monomer is prevented from being polymerized due to the early addition of the catalyst and the initiator, the fluidity of the ceramic suspension in the process of being injected into the filter mold is ensured, the filling effect of the ceramic suspension in the filter mold is improved, and the requirements of forming and precision of a large-size or structurally-designed complex dielectric filter are further met.

In one possible implementation, the ceramic powder, the solvent, the dispersant, the monomer, and the crosslinker are in a mass ratio of: (90-110): (5-20): (0.5-2): (1-7): (0.05-0.15). The ceramic suspension formed can have better fluidity, and meanwhile, the gel is formed by monomer polymerization, so that the integrated forming of the dielectric filter is realized, and the forming precision requirement of the dielectric filter with large size or complex structural design is met.

In one possible implementation, the polymerizable substance is a copolymer and the polymerization aid includes a dispersant. The copolymer is further polymerized to form solidified gel, so that ceramic powder is fixed along with the solidification of the gel, a ceramic blank is obtained, and the molding requirement of the dielectric filter is met.

In one possible implementation, the preparing a ceramic suspension includes:

mixing the copolymer, the dispersant and the solvent to form a mixed solution;

and adding the ceramic powder into the mixed solution, and mixing to form the ceramic suspension.

That is, when preparing the ceramic suspension, the copolymer, the dispersing agent and the solvent are mixed to form a mixed solution, and then the ceramic suspension is formed by mixing the ceramic powder with the mixed solution, so that the operation is convenient, and the dispersion and the fluidity of the ceramic suspension are improved.

In one possible implementation, the mass ratio of the ceramic powder, the solvent, the dispersant and the copolymer is: (90-110): (5-20): (0.5-2): (1-7). The formed ceramic suspension has good fluidity, and meanwhile, the copolymer is polymerized to form gel, so that the molding precision requirement of a large-size or structural design complex dielectric filter is met.

In one possible implementation, the ceramic powder includes at least one of calcium magnesium titanate, samarium calcium aluminate, barium titanate, and lanthanum strontium aluminate.

In one possible implementation, the polymerizable substance includes: n-methylol acrylamide and/or acrylamide.

In one possible implementation, the polymerizable substance includes: isobutylene-maleic anhydride copolymers.

The second aspect of the embodiment of the application provides a dielectric filter, which is prepared by any one of the above-mentioned dielectric filter molding methods. The dielectric filter formed by the forming method can be a dielectric filter with large size and complex structural design, and is beneficial to meeting the requirements on the performance of the dielectric filter.

In one possible implementation, the dielectric filter is provided with a recess on at least one side surface. The groove can improve the performance of the dielectric filter, and the structure of the dielectric filter is more complicated, and the integrated forming of the dielectric filter with the groove can be realized by using the forming method.

In one possible implementation, the length of at least one of the length, width, and height of the dielectric filter is greater than 100mm. The large-size requirement of the dielectric filter is met, and the integral forming of the large-size dielectric filter can be realized by using the forming method.

In one possible implementation, the dielectric filter includes at least two filter units, and at least two filter units are stacked. The functions of the dielectric filter can be enriched through the lamination of the plurality of filter units, the structure of the dielectric filter can be more complicated, and the integral forming of the dielectric filter with at least two layers of lamination filter units can be realized by using the forming method.

A third aspect of the embodiment of the present application provides an electronic device, at least including a radio frequency unit and the above-mentioned dielectric filter, where the dielectric filter is electrically connected to the radio frequency unit.

The dielectric filter can filter the radio frequency signals sent or received by the radio frequency unit, and is beneficial to improving the quality of signal transmission.

Drawings

FIG. 1 is a flow chart of a method for forming a dielectric filter according to an embodiment of the present application;

fig. 2 is a schematic structural diagram of a dielectric filter obtained by using the method for forming a dielectric filter according to an embodiment of the present application;

FIG. 3 is a schematic diagram of another dielectric filter obtained by the method for forming a dielectric filter according to an embodiment of the present application;

fig. 4 is a schematic structural diagram of another dielectric filter obtained by using the method for forming a dielectric filter according to an embodiment of the present application;

FIG. 5 is a schematic structural diagram of another dielectric filter obtained by the filter forming method according to the embodiment of the present application;

FIG. 6 is a schematic flow chart of a method for forming a dielectric filter according to a first embodiment of the present application;

fig. 7 is a schematic flow chart of a forming method of a dielectric filter according to a second embodiment of the present application.

Reference numerals illustrate:

a 100-dielectric filter;

100 a-side;

101-grooves;

102-a first filtering unit;

103-a second filtering unit;

104-support structure.

Detailed Description

The terminology used in the description of the embodiments of the application herein is for the purpose of describing particular embodiments of the application only and is not intended to be limiting of the application.

The dielectric filter is a microwave filter which adopts a dielectric resonant cavity to play a role in selecting frequencies through multistage coupling. The dielectric filter has the advantages of miniaturization, low loss, good temperature characteristic and the like, and is widely applied to communication systems such as mobile communication, microwave communication and the like.

Most of common dielectric filters are microwave dielectric ceramic filters, and microwave dielectric ceramic refers to ceramic which is applied to a microwave frequency band (for example, 300 MHz-300 GHz) circuit as a dielectric material and performs one or more functions, and is suitable for a microwave mobile communication scene. At present, the microwave dielectric ceramic filter produced in mass production is mostly prepared by adopting a dry pressing forming mode. Specifically, the ceramic dry powder is filled into a filter die, the ceramic dry powder is pressed to form a blank, and then the filter is formed through steps of sintering, metallization and the like, but the density of the blank after dry pressing is uneven, shrinkage after sintering is inconsistent, the dimensional accuracy is poor, and the tuning workload of the filter is increased.

In order to meet the requirements of communication quality, the dielectric filter is gradually developed towards the directions of large size and complicated structural design, wherein the complicated structural design specifically refers to that structural designs such as blind holes, through holes, grooves and the like (shown in fig. 1) are formed on the side surface of the dielectric filter so as to improve the performance of the dielectric filter, or the dielectric filter can also comprise a multi-layer filtering unit, and a partition structure and the like are arranged inside the dielectric filter. The dry press molding is used as a two-dimensional molding mode, and can only mold the integral molding of the dielectric filter with a simple structure, but cannot meet the integral molding requirement of the dielectric filter with a large size and a complex structural design.

Aiming at the molding of a dielectric filter with large size or complex structural design, a ceramic powder injection molding mode is introduced in the related technology, specifically, ceramic powder and a high polymer binder (such as acrylic resin, rubber or phenolic resin and the like) are mixed, and after uniform mixing, the mixture can be heated to be melted at high temperature to obtain ceramic filler, and the melted ceramic filler is injected into a mold of the dielectric filter and is molded after cooling to obtain a ceramic blank. Removing the high polymer organic matters from the ceramic blank, and then sintering, metallizing and the like the degreased ceramic blank to form the dielectric filter.

However, the ceramic powder and the polymer binder obtain the ceramic filler in a molten state, the polymer binder is used as a forming agent of the ceramic powder, the content of the polymer binder in the molten ceramic filler is required to be relatively high, a large amount of polymer organic matters exist in the ceramic filler, the thickness of the dielectric filter is generally larger than 3mm (for example, the thickness of the dielectric filter can be 8-10 mm), and thus, in the degreasing process for removing the polymer organic matters, the internal polymer components are difficult to effectively discharge, the degreasing process is slow, the required time period is long, for example, one to two weeks are generally required, and the processing efficiency of the dielectric filter is reduced. And the residual polymer binder is easy to cause cracking of the ceramic blank in the subsequent sintering process, so that the precision of the dielectric filter can be influenced.

In addition, the viscosity of the molten ceramic filler is relatively high, the fluidity is poor, and when a large-size or structurally-designed complex dielectric filter is manufactured, the ceramic filler is difficult to well fill into a mold, and injection operation is required by auxiliary equipment capable of realizing extrusion, vacuum pushing and the like, so that the manufacturing cost is increased. And the existence of complex structures such as blind holes and through holes can also influence the effective welding of ceramic fillers in the injection molding process, so that the finished dielectric filter is easy to have processing defects such as welding marks, flow lines, burrs and the like, and the precision of the dielectric filter can be influenced.

Based on the technical problems described above, the embodiment of the application provides a method for forming a dielectric filter, which is particularly suitable for forming a dielectric ceramic filter with a large size or a complex structural design, can well meet the integral forming requirement of the dielectric filter with the large size or the complex structural design, can effectively shorten the degreasing time in the forming process, and improves the processing efficiency.

The method can be applied to the forming scene of the microwave dielectric ceramic filter, and can also be used for forming dielectric ceramic filters in other wave bands.

The following describes the dielectric filter forming method according to the embodiment of the present application in detail with reference to specific forming steps.

Fig. 1 is a flowchart of a method for forming a dielectric filter according to an embodiment of the present application.

Referring to fig. 1, the method for forming the dielectric filter comprises the following steps:

s101: preparing a ceramic suspension, wherein the ceramic suspension at least comprises ceramic powder, a polymerizable substance, a polymerization auxiliary agent and a solvent.

The ceramic powder may be a dielectric ceramic powder, and specifically, the ceramic powder may at least include one of calcium magnesium titanate, samarium calcium aluminate, barium titanate, and lanthanum strontium aluminate.

The suspension refers to a dispersion of solid particles in a liquid solvent, wherein the solid particles undergo a diffusion displacement, also called brownian displacement, due to disordered collisions of the thermal motion of liquid molecules, and the solid particles cannot sink in the liquid quickly due to brownian displacement, and the mixture of the solid particles and the liquid becomes a suspension.

The solvent may be an aqueous solution, or may be another organic solvent, for example, an ethanol solution, a methanol solution, or the like. In the embodiment of the present application, the solvent is taken as an aqueous solution as an example, that is, the ceramic powder, the polymerizable substance and the polymerization auxiliary agent are dispersed into the aqueous solution to form a ceramic suspension. The suspension itself has good dispersibility and fluidity, and contains low concentration of organic molecules (such as polymerizable substances and polymerization aids), and low viscosity, and can flow like water flow.

The polymerizable substance is a substance capable of polymerizing under certain conditions to form a polymer, and in the embodiment of the present application, the polymerizable substance is a substance capable of polymerizing to form a gel of a network structure to be cured. For example, the polymerizable material may be N-methylolacrylamide, acrylamide, isobutylene-maleic anhydride copolymers, and the like. Of course, in some examples, the polymerizable substance may also be other compounds capable of polymerizing to form a gel.

The polymerization auxiliary agent refers to auxiliary substances added in the polymerization process, such as an initiator, a catalyst, an emulsifier, a dispersing agent and the like. Its functions are to initiate polymerization, improve polymerization rate, control molecular weight, improve polymer properties, etc., and can facilitate polymerization of the polymerizable material to form a gel.

Adding ceramic powder, polymerizable substances and polymerization auxiliary agents into a solvent, and fully and uniformly mixing to obtain the ceramic suspension. Specifically, the above materials can be mixed by using a ball milling process, for example, ceramic powder, polymerizable materials, polymerization auxiliary agents and aqueous solution are added into a ball mill to perform the ball milling process, so that the ceramic powder, the polymerizable materials and the polymerization auxiliary agents are fully dispersed in the aqueous solution to obtain a uniformly mixed ceramic suspension, and the formed ceramic suspension has lower content of polymerizable materials, polymerization auxiliary agents and other organic materials, lower viscosity and good fluidity.

S102: and (3) injecting the ceramic suspension into a filter die, and demolding after the ceramic suspension is polymerized to form gel and solidified to form a ceramic front blank.

Wherein, the gel means that the polymers in the solution are mutually connected under certain conditions to form a space network structure, and the gaps of the network structure are filled with liquid serving as a dispersion medium. When ceramic suspension with good fluidity is injected into a filter mold, a polymerizable substance can be used as a ceramic molding agent, specifically, the polymerizable substance uniformly dispersed in the ceramic suspension is polymerized in the mold to form gel with a net structure, and gaps of the net structure are filled with ceramic powder and solvent, so that the ceramic powder is uniformly filled into the filter mold and fixed along with solidification of the gel, and a molded solid ceramic front blank can be obtained after demolding.

In particular, the ceramic suspension may be injected into the filter mold by an injection device, for example, an injection machine may be used to inject the ceramic suspension into the filter mold.

S103: and drying the ceramic front blank body and then degreasing to remove gel to form the ceramic blank body.

The method comprises the steps of firstly, drying a ceramic front blank, and removing redundant solvent in the ceramic front blank in the drying process. And degreasing to remove polymer gel in the ceramic blank body, thereby obtaining the ceramic blank body after removing the gel and the solvent.

Specifically, the drying mode can be high-temperature drying, and the drying temperature can be selected and set according to actual requirements, so that the purposes of removing gel and redundant solvent can be achieved.

The sectional drying mode can be adopted in the drying process, and the specific stages and the temperatures of the stages can be set according to the requirements so as to achieve a good removal effect.

The degreasing treatment mode can be a high-temperature degreasing mode, for example, a dried ceramic precursor blank is placed in a combustion type degreasing furnace for degreasing, and the degreasing temperature can be selected and set according to actual requirements, so that the purpose of removing gel can be achieved.

S104: and (3) sequentially carrying out sintering molding and surface metallization treatment on the ceramic blank to form the dielectric filter.

Specifically, the ceramic body can be put into a sintering furnace to be sintered and molded, and the molded ceramic medium is obtained after sintering.

The sintering mode can adopt a sectional heating mode for sintering, and specifically the included sintering stage and the sintering temperature of each stage can be selected and set according to actual requirements, and the method is not limited in the embodiment of the application.

And carrying out surface metallization treatment on the formed ceramic medium to obtain the medium filter.

The surface metallization means that a metal layer is formed on the surface of the filter, so that the electric coupling connection between the filter and an external circuit is realized. Specifically, the surface metallization may be achieved by electroplating, spraying, dipping, etc., and the metal material may be silver, nickel, tin, copper, etc.

Before the surface metallization treatment, the shaped ceramic medium may be first subjected to a surface treatment, such as grinding, polishing, cleaning, etc., so as to facilitate the formation of a metal layer and ensure the performance of the dielectric filter.

That is, in the embodiment of the present application, the ceramic powder, the polymerizable substance and the polymerization auxiliary agent are mixed to form a ceramic suspension, the ceramic suspension is injected into a filter mold to polymerize to form gel, which is cured and then demolded, and then the dielectric filter is obtained through drying, degreasing, sintering and metallization. That is, the ceramic suspension is polymerized to form a gel with a net structure after being injected into a mold, and then the gel is solidified, ceramic powder uniformly distributed in the mold is fixed along with the solidification of the gel, so that a ceramic pre-blank is formed, and the dielectric filter is obtained through operations such as drying and degreasing.

And because the viscosity of the ceramic suspension is low, the fluidity of the ceramic suspension is good, and when the ceramic suspension is injected into the filter mould, the ceramic suspension can fill the filter mould as fast and effectively as water flow. Particularly, the method can be well filled into a filter mold aiming at a large-size or structural design complex dielectric filter, for example, the method can be well filled into a hole groove formed in the filter mold for forming the complex structure, so that the integrated forming requirement of the large-size or structural design complex dielectric filter is met, and the forming method can be well suitable for forming the large-size or structural design complex dielectric filter.

Moreover, the gel of the network structure is relatively large in volume, the relative content of polymerizable substances, polymeric additives and other high-molecular organic substances in the ceramic suspension is small while the molding requirement is met, the relative content of the gel in the formed ceramic front blank is small, the time required in the degreasing process for removing the gel can be effectively reduced, and the processing efficiency of the dielectric filter is improved. The risk of high polymer substance residues after degreasing treatment is reduced, and the precision of the dielectric filter is improved.

In addition, the difficulty of injecting and filling the ceramic suspension into the filter mould is low, and additional auxiliary equipment such as extrusion, vacuum pushing and the like can be omitted, so that the processing cost is reduced. Compared with the prior art that ceramic filler is formed by high-temperature melting and low-temperature cooling, the method omits the steps of high-temperature heating, low-temperature cooling and the like, has the advantages of simple forming method, convenient operation, contribution to reducing equipment required by the whole forming process, and capability of effectively reducing the processing cost while further improving the processing efficiency of the dielectric filter.

And the problems of weld marks, flow lines, burrs and other processing defects of the finished filter caused by insufficient filling can be reduced or avoided, so that the accuracy of the dielectric filter is guaranteed while the processing efficiency of the dielectric filter is improved and the processing cost is reduced.

It should be appreciated that to expedite the injection of the ceramic suspension into the filter mold, in some examples, extrusion, vacuum pushing, etc. devices may also be used to assist in injecting the ceramic suspension into the structure, which may help to further improve the processing efficiency.

Fig. 2 is a schematic structural diagram of a dielectric filter obtained by a dielectric filter forming method according to an embodiment of the present application, fig. 3 is a schematic structural diagram of another dielectric filter obtained by a dielectric filter forming method according to an embodiment of the present application, and fig. 4 is a schematic structural diagram of another dielectric filter obtained by a dielectric filter forming method according to an embodiment of the present application.

The dielectric filter with complex structural design can be prepared by using the molding method, specifically, for example, as shown in fig. 2, a groove 101 can be formed on at least one side surface of the dielectric filter 100, for example, as shown in fig. 2, a plurality of grooves 101 are formed on one side surface of the dielectric filter 100, and the grooves 101 can improve the performance of the dielectric filter 100.

The recess 101 may be configured to implement capacitive coupling on the dielectric filter 100, or the recess 101 may be configured to meet other functional requirements of the dielectric filter 100, such as adjusting a passband frequency position of the dielectric filter 100, etc. The arrangement of the grooves 101 makes the structure of the dielectric filter 100 more complicated, and the integrated forming of the dielectric filter 100 with the grooves 101 can be realized by using the forming method, and the forming method is simple and convenient to operate and has higher processing efficiency.

The shape of the groove 101 may be a regular or irregular shape such as a circle, a square, an ellipse, a T-shape, etc., which is not limited in the embodiment of the present application.

The number and positions of the grooves 101 may be selected according to the performance requirements of the dielectric filter 100, and are not limited in the embodiment of the present application. For example, referring to fig. 3, grooves 101 may be provided on only one side surface (e.g., side surface 100a in fig. 3) of the dielectric filter 100, and the number of grooves 101 may be one, or the number of grooves 101 may be plural.

Alternatively, as shown with reference to fig. 4, grooves 101 may be provided on at least two sides of the dielectric filter 100 (e.g., grooves 101 are provided on four sides in fig. 4), and the number of grooves 101 on each side may be one, or the number of grooves 101 on each side may be plural.

Fig. 5 is a schematic structural diagram of another dielectric filter obtained by the filter forming method according to the embodiment of the present application.

For example, the dielectric filter 100 may further include at least two filter units, where the at least two filter units may be stacked, where the stacking of the plurality of filter units may enrich the functions of the dielectric filter 100, and may also complicate the structure of the dielectric filter 100.

A support structure may be disposed between two adjacent filter units to ensure stability of the dielectric filter 100. For example, referring to fig. 5, taking an example in which the dielectric filter 100 includes two filter units stacked, a first filter unit 102 and a second filter unit 103, respectively, a support structure 104 may be disposed between the first filter unit 102 and the second filter unit 103.

Of course, in some examples, the molding method may also be applied to molding of dielectric filters having other complex structures, for example, the dielectric filter 100 may have a structure such as a partition plate therein. Alternatively, the dielectric filter 100 may include two or more layers of filter units stacked, each of which may include two parallel filter modules (as shown with reference to fig. 2, the filter unit 105 includes a filter module 105a and a filter module 105 b), and so on.

The forming method can also be used for preparing a large-size dielectric filter, for example, the length of at least one of the length, the width and the height of the dielectric filter 100 is greater than 100mm, if the length of the dielectric filter 100 is L1, the width is L2, and the height is L3 (refer to FIG. 4), the length of L1 can be greater than 100mm, the large-size requirement of the dielectric filter 100 is met, the integral forming of the large-size dielectric filter 100 can be realized by using the forming method, and the forming method is simple and convenient to operate and has higher processing efficiency.

In the embodiments of the present application, the polymerizable material in the ceramic suspension may be a monomer capable of polymerizing, or the polymerizable material may be a copolymer capable of further polymerizing, capable of polymerizing to form a cured gel. The method of forming a dielectric filter using different types of polymerizable substances will be described in detail with reference to specific examples.

Example 1

In this example, the polymerizable substance is a monomer, which is a generic term for small molecules capable of polymerizing with the same or other molecules, is a simple compound capable of producing a high molecular compound by polymerization, polycondensation, or the like, and is a low molecular raw material for synthesizing a polymer.

For example, the polymerizable material may be N-methylolacrylamide, capable of polymerizing to form a gel and curing. Of course, in some other examples, the polymerizable substance may be any other monomer capable of polymerizing to form a gel, for example, the polymerizable substance may also be acrylamide.

The polymer auxiliary agent can comprise a cross-linking agent, a catalyst, an initiator and a dispersing agent. That is, when preparing the ceramic suspension, ceramic powder, monomer, cross-linking agent, catalyst, initiator and dispersant may be added into the solvent to form mixed solution to obtain the ceramic suspension.

Wherein, the initiator is a compound which is easy to decompose into free radicals, is a substance capable of initiating the monomer to carry out polymerization reaction, and can participate in and initiate the polymerization of the polymerizable substance to form gel.

Specifically, the initiator may be ammonium persulfate.

Crosslinking agents are a class of small molecule compounds that have reactive ends with two or more reactive groups (e.g., amino groups, sulfhydryl groups, etc.) that can be coupled to two or more molecules separately to bind the molecules together, act as bridging, and participate in the polymerization of polymerizable materials to form gels.

Specifically, the crosslinking agent may be N-N-methylenebisacrylamide.

The catalyst is a substance which can change the chemical reaction rate of other substances in chemical reaction, has a catalytic effect and can play a role in catalyzing polymerization, thereby promoting the interaction of monomers, a crosslinking agent and an initiator to form gel.

In particular, the catalyst may be tetramethyl ethylenediamine.

The dispersing agent has good dispersing effect, can uniformly disperse ceramic powder, monomers, catalysts, initiators, cross-linking agents and the like in the solvent, is beneficial to improving the dispersibility of the substances in the solvent, ensures the fluidity, is convenient for realizing the full polymerization of the monomers, is beneficial to improving the distribution uniformity of the ceramic powder in gel, and is further beneficial to improving the precision and the quality of the dielectric filter.

In particular, the dispersant may be ammonium polyacrylate or ammonium citrate.

The polymerizable substance is made into a monomer, the polymerization auxiliary agent comprises an initiator, a cross-linking agent and the like, after the ceramic suspension is injected into the filter mould, the initiator can be decomposed to generate free radicals, and the monomer can be polymerized with the free radicals to form a chain polymer. The cross-linking agent may further polymerize with the chain polymer to form a network of gel. Therefore, the polymerizable substance is solidified by forming gel in the filter die, the ceramic powder is fixed along with the solidification of the gel, and finally the dielectric filter is obtained through degreasing, sintering and other steps, so that the molding requirement of the dielectric filter is met.

Fig. 6 is a schematic flow chart of a method for forming a dielectric filter according to a first embodiment of the present application.

Referring to fig. 6, the method for preparing the ceramic suspension, that is, step S101, may specifically include:

s111: mixing ceramic powder, a dispersing agent, a monomer, a cross-linking agent and a solvent to form a mixed solution.

Ceramic powder, a dispersing agent, a monomer and a cross-linking agent can be added into a solvent, and then the mixture is uniformly mixed by a ball milling process to obtain a uniformly mixed solution.

Specifically, the dispersing agent, the monomer, the cross-linking agent and the solvent can be mixed firstly, then the ceramic powder and the mixed solution are added into the ball mill to be ball-milled and mixed together, so that the mixed solution is obtained, the realization is convenient, and the dispersion of the ceramic powder in the mixed solution is improved.

S121: adding a catalyst and an initiator into the mixed solution, and mixing to form a ceramic suspension.

For example, the catalyst may be added to the mixed solution first, and after the catalyst and the mixed solution are mixed uniformly, the initiator may be added and mixed.

In the embodiment of the application, when the ceramic suspension is prepared, firstly, the monomer, the ceramic powder, the dispersing agent and the cross-linking agent are mixed with the solvent to form a mixed solution, and then the catalyst and the initiator are added into the mixed solution to form the ceramic suspension, so that the polymerization of the monomer caused by the premature addition of the catalyst and the initiator can be avoided, the viscosity of the ceramic suspension is increased to influence the fluidity of the ceramic suspension, the fluidity of the ceramic suspension in the process of being injected into the filter mold is ensured, the filling effect of the ceramic suspension in the filter mold is improved, and the requirements of the forming and the precision of the dielectric filter with large size or complex structural design are further met.

Specifically, the mass ratio of the ceramic powder, the solvent, the dispersant, the monomer and the cross-linking agent can be: (90-110): (5-20): (0.5-2): (1-7): (0.05-0.15). Therefore, the formed ceramic suspension liquid has good fluidity, and meanwhile, the monomer is fully polymerized to form solidified gel, so that the integrated forming of the dielectric filter is realized, and the forming requirement of the dielectric filter with large size or complex structural design is met.

Taking a solvent as an aqueous solution and ceramic powder as calcium magnesium titanate powder as an example, the forming method specifically comprises the following steps:

n-methylolacrylamide, N-N-methylenebisacrylamide and ammonium polyacrylate are added into the aqueous solution and mixed to form a mixed aqueous solution.

Adding the mixed aqueous solution and calcium magnesium titanate into a ball mill for ball milling and mixing to form a mixed solution, wherein the mass ratio of the calcium magnesium titanate, the aqueous solution, the ammonium polyacrylate, the N-methylol acrylamide and the N-N-methylene bisacrylamide in the ceramic suspension is (90-110): (5-20): (0.5-2): (1-7): (0.05-0.15).

And adding tetramethyl ethylenediamine into the mixed solution, mixing, adding ammonium persulfate, and mixing to obtain a ceramic suspension.

And (3) injecting the ceramic suspension into a filter die, and demolding after the ceramic suspension is polymerized to form gel, so as to form a ceramic front blank.

And drying the ceramic front blank body and degreasing to remove gel to form the ceramic blank body.

And placing the ceramic blank in a sintering furnace, sintering and forming to obtain a formed ceramic medium, and performing surface metallization treatment on the formed ceramic medium to prepare the formed dielectric filter.

Example two

In this embodiment, the polymerizable substance is a copolymer, which is a polymer obtained by polymerizing two or more different monomers, and the copolymer is capable of undergoing further polymerization, in other words, the copolymer is capable of further polymerizing to form a gel with a network structure.

For example, the polymerizable material may be an isobutylene-maleic anhydride copolymer formed by polymerizing isobutylene monomer and maleic anhydride monomer, capable of further polymerization to form a net-like cured gel. Of course, in some other examples, the polymerizable material may be any other copolymer capable of further polymerizing to form a gel.

Wherein, the ceramic suspension also comprises a dispersing agent, that is, when the ceramic suspension is prepared, ceramic powder, a copolymer and the dispersing agent can be added into a solvent to form a mixed solution, thus obtaining the ceramic suspension. The dispersing agent can disperse and flow the ceramic suspension, which is beneficial to meet the molding requirement of large-size or structural design complex dielectric filter.

The material of the dispersant can be referred to in the first embodiment, and will not be described in detail in the embodiments of the present application.

The polymerizable substance is a copolymer, the polymerization auxiliary agent comprises a dispersing agent, and after the ceramic suspension is injected into the filter die, the copolymer is further polymerized to form a net-shaped gel, so that the polymerization of the polymerizable substance in the die and the formation of a solidified gel are realized, the ceramic powder is fixed along with the solidification of the gel, a ceramic blank is obtained, and the molding requirement of the dielectric filter is met. In addition, the polymerizable substance is made into a copolymer, so that the ceramic suspension can be conveniently and rapidly and effectively formed into solidified gel after being injected into a mold, and the influence on the molding precision and quality of the dielectric filter caused by insufficient polymerization can be reduced or avoided.

Referring to fig. 7, the method for preparing the ceramic suspension, that is, step S101, may specifically include:

s131: the copolymer, dispersant and solvent are mixed to form a mixed solution.

S141: adding ceramic powder into the mixed solution, and mixing to form ceramic suspension.

Specifically, the ceramic powder and the mixed solution can be added into a ball mill to be ball-milled and mixed together, so as to obtain ceramic suspension.

In the embodiment of the application, when the ceramic suspension is prepared, the polymer intermediate piece, the dispersing agent and the solvent are mixed to form the mixed solution, and then the ceramic powder and the mixed solution are mixed to form the ceramic suspension through a ball milling process, so that the ceramic suspension is convenient to operate and realize, and the dispersibility and the fluidity of the ceramic suspension are improved.

Specifically, the mass ratio of the ceramic powder, the solvent, the dispersing agent and the copolymer is as follows: (90-110): (5-20): (0.5-2): (1-7). Therefore, the formed ceramic suspension liquid has good fluidity, and the copolymer is fully polymerized to form solidified gel, so that the integrated forming of the dielectric filter is realized, and the forming requirement of the dielectric filter with large size or complex structural design is met.

the isobutylene-maleic anhydride copolymer and ammonium polyacrylate are added to an aqueous solution and mixed to form a mixed solution.

Adding the mixed solution and calcium magnesium titanate into a ball mill for ball milling and mixing to form ceramic suspension, wherein the mass ratio of the calcium magnesium titanate to the aqueous solution to the ammonium polyacrylate to the isobutylene-maleic anhydride copolymer in the ceramic suspension is (90-110): (5-20): (0.5-2): (1-7).

The dielectric filter provided by the embodiment of the application is prepared by the dielectric filter molding method. The dielectric filter can be a microwave ceramic dielectric filter, can be applied to communication systems such as mobile communication or microwave communication, and is beneficial to improving the signal transmission quality of the communication systems.

In order to meet the performance requirement of the dielectric filter, the dielectric filter can be a large-size dielectric filter, at least one side surface of the dielectric filter can be provided with grooves, and the dielectric filter can also be formed by stacking a plurality of layers of filter units.

The embodiment of the application also provides electronic equipment which can be wireless radio frequency equipment, for example, an antenna. Alternatively, the electronic device may be other radio frequency devices, for example, a component that needs to have a filtering function on a radio frequency transceiver link.

Specifically, the electronic device at least comprises a radio frequency unit and the dielectric filter, wherein the dielectric filter is electrically connected with the radio frequency unit, and the radio frequency unit can send or receive radio frequency signals. The radio frequency signals sent by the radio frequency unit can be sent after passing through the dielectric filter, and the radio frequency signals received by the radio frequency unit can be received by the radio frequency unit after passing through the dielectric filter. The dielectric filter can play a role in filtering the radio frequency signals, so that the quality of signal transmission is improved.

It should be noted that, the numerical values and the numerical ranges related to the embodiments of the present application are approximate values, and may have a certain range of errors under the influence of the manufacturing process, and those errors may be considered to be negligible by those skilled in the art.

In describing embodiments of the present application, it should be noted that, unless explicitly stated or limited otherwise, the terms "mounted," "connected," and "coupled" should be construed broadly, and may be, for example, fixedly coupled, indirectly coupled through an intermediary, in communication between two elements, or in an interaction relationship between two elements. The specific meaning of the above terms in the embodiments of the present application will be understood by those of ordinary skill in the art according to specific circumstances. The terms "first," "second," "third," "fourth," and the like, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the embodiments of the present application, and are not limited thereto; although embodiments of the present application have been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of forming a dielectric filter, the method comprising:

2. The method of forming a dielectric filter according to claim 1, wherein the polymerizable substance is a monomer, and the polymerization auxiliary agent comprises a crosslinking agent, a catalyst, an initiator, and a dispersing agent.

3. The method of forming a dielectric filter of claim 2, wherein the preparing a ceramic suspension comprises:

4. The method of forming a dielectric filter according to claim 3, wherein the mass ratio of the ceramic powder, the solvent, the dispersant, the monomer and the crosslinking agent is: (90-110): (5-20): (0.5-2): (1-7): (0.05-0.15).

5. The method of forming a dielectric filter of claim 1 wherein the polymerizable material is a copolymer and the polymerization aid comprises a dispersant.

6. The method of forming a dielectric filter of claim 5, wherein preparing the ceramic suspension comprises:

mixing the copolymer, the dispersant and the solvent to form a mixed solution;

7. The method of forming a dielectric filter according to claim 6, wherein the mass ratio of the ceramic powder, the solvent, the dispersant and the copolymer is: (90-110): (5-20): (0.5-2): (1-7).

8. The method of forming a dielectric filter according to any one of claims 1 to 7, wherein the ceramic powder includes at least one of calcium magnesium titanate, samarium calcium aluminate, barium titanate, and lanthanum strontium aluminate.

9. The method of forming a dielectric filter according to any one of claims 1 to 4, wherein the polymerizable substance comprises: n-methylol acrylamide and/or acrylamide.

10. The method of forming a dielectric filter according to any one of claims 5 to 7, wherein the polymerizable substance comprises: isobutylene-maleic anhydride copolymers.

11. A dielectric filter prepared by the method of any one of claims 1 to 10.

12. The dielectric filter of claim 11, wherein at least one side of the dielectric filter is fluted;

or the length of at least one of the length, the width and the height of the dielectric filter is more than 100mm;

or, the dielectric filter comprises at least two filter units, and at least two filter units are stacked.

13. An electronic device comprising at least a radio frequency unit and a dielectric filter according to any of the preceding claims 11 or 12, said dielectric filter being electrically connected to said radio frequency unit.