A balun structure and method of manufacturing the same

Abstract

The application provides a balun structure and a preparation method thereof. The balun structure comprises a substrate, a first inductor coil and a second inductor coil. The substrate comprises a dielectric film and a magnetic core unit. The magnetic core unit comprises two magnetic core layers and three magnetic core columns arranged at intervals. The two magnetic core layers are respectively arranged on opposite sides of the dielectric film in a laminated manner. Each magnetic core column penetrates through the dielectric film to connect the two magnetic core layers. The first inductor coil is arranged between the two magnetic core layers and spirally wound among the three magnetic core columns. The second inductor coil is arranged between the two magnetic core layers and spirally wound among the three magnetic core columns. The second inductor coil is coupled with the first inductor coil. An input end, a first output end, a second output end and a ground end are arranged on the outer surface of the substrate. One end of the first inductor coil is electrically connected with the input end, and the other end is electrically connected with the ground end. The two ends of the second inductor coil are respectively electrically connected with the first output end and the second output end.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microwave communication, and more particularly relates to a balun structure and a preparation method thereof. BACKGROUND

[0002] Electronic technology is developing towards multifunction, miniaturization and high reliability, and low-temperature co-fired ceramic technology (abbreviation of Low-Temperature Co-fired Ceramics, hereinafter referred to as: LTCC) is attracting more and more attention. As a balanced and unbalanced converter, a balun is widely used in microwave systems such as antennas, mixers, frequency multipliers, etc., and is an important element in a microwave system. The laminated balun is a balun structure made of a ceramic membrane through LTCC.

[0003] The balun structure in the related art, for example, for a balun structure with a length of 2 mm and a width of 1.2 mm, the lower limit of the frequency band is usually greater than 200 megahertz, and it is difficult to expand to a frequency band lower than 200 megahertz while meeting miniaturization. SUMMARY

[0004] Embodiments of the application provide a balun structure and a preparation method thereof, which can achieve the purpose of considering miniaturization and expanding to a low frequency band.

[0005] In a first aspect, the application provides a balun structure, comprising a substrate, a first inductor coil and a second inductor coil, the substrate comprising a dielectric membrane and a magnetic core unit, the magnetic core unit comprising two magnetic core layers and three magnetic core columns arranged at intervals, the two magnetic core layers being respectively laminated on opposite sides of the dielectric membrane, and each of the magnetic core columns penetrating the dielectric membrane to connect the two magnetic core layers; the first inductor coil is located between the two magnetic core layers and is spirally wound between the three magnetic core columns; the second inductor coil is located between the two magnetic core layers and is spirally wound between the three magnetic core columns, and the second inductor coil is coupled with the first inductor coil; wherein the substrate has an input end, a first output end, a second output end and a ground end on the outer surface, one end of the first inductor coil is electrically connected with the input end, and the other end is electrically connected with the ground end; the two ends of the second inductor coil are respectively electrically connected with the first output end and the second output end.

[0006] In some embodiments, the three magnetic core columns are arranged along a direction perpendicular to the thickness direction of the dielectric membrane, and the magnetic core column in the middle is a common magnetic core column, and the two magnetic core columns other than the common magnetic core column are first magnetic core columns, the first inductor coil and the second inductor coil are spirally wound around the common magnetic core column, and along the thickness direction, the projections of the first inductor coil and the second inductor coil on the magnetic core layer are staggered.

[0007] In some embodiments, the number of the dielectric film sheets is multiple, the first inductor coil includes a plurality of first conductive patterns and a first via conductor, the plurality of first conductive patterns are printed on the plurality of dielectric film sheets, and the first via conductor connects two adjacent first conductive patterns; the second inductor coil includes a plurality of second conductive patterns and a second via conductor, the second conductive patterns are printed on the plurality of dielectric film sheets, and the second via conductor connects two adjacent second conductive patterns; and the dielectric film sheets printed with the first conductive patterns and the dielectric film sheets printed with the second conductive patterns are alternately stacked along the thickness direction.

[0008] In some embodiments, the first conductive patterns or the second conductive patterns are printed on each of the dielectric film sheets; a first via hole is formed on a part of the dielectric film sheets printed with the second conductive patterns, and a second via hole is formed on a part of the dielectric film sheets printed with the first conductive patterns, and the first via hole and the second via hole are filled with conductive material to form the first via conductor and the second via conductor, respectively.

[0009] In some embodiments, the number of the first conductive patterns is the same as the number of the second conductive patterns.

[0010] In some embodiments, a relief hole is formed on each of the dielectric film sheets, and the relief hole is filled with magnetic insulation material to form the magnetic core column.

[0011] In some embodiments, the three magnetic core columns and the two magnetic core layers are an integral structure.

[0012] In some embodiments, the three magnetic core columns and the two magnetic core layers are made of magnetic insulation material, and the magnetic insulation material is ferrite with a magnetic permeability of 300-1000.

[0013] In some embodiments, the cross-sectional area of the common magnetic core column is greater than the cross-sectional area of each of the first magnetic core columns, and the cross-section is perpendicular to the thickness direction.

[0014] In some embodiments, the wire diameter of the first inductor coil and the second inductor coil is 40-80 μm.

[0015] In some embodiments, the wire spacing of the first inductor coil and the second inductor coil is equal to the wire diameter.

[0016] In some embodiments, the dielectric film sheet is a dielectric ceramic film sheet, the dielectric constant of the dielectric film sheet is 3-10, and the dielectric loss is less than or equal to 0.01.

[0017] The beneficial effect of the balun structure provided by the present application is that, compared with the prior art, the substrate of the balun structure provided by the present application is composed of a dielectric film and a magnetic core unit, the first inductive coil and the second inductive coil are both located between two magnetic core layers and are both spirally wound between three magnetic core columns, the first inductive coil and the second inductive coil are coupled under the action of the magnetic field formed by the magnetic core unit, so that the balun structure has a magnetic coupling characteristic, the advantages of magnetic materials and dielectric materials can be fully utilized, so that the balun structure can achieve the purpose of expanding to a low frequency band on the basis of miniaturization, thereby achieving the purpose of considering miniaturization design and expanding to a low frequency band.

[0018] In a second aspect, the present application further provides a preparation method of a balun structure, which is applied to the balun structure of the first aspect and comprises the following steps:

[0019] providing one magnetic core layer and a plurality of dielectric films;

[0020] the avoidance hole is formed on each dielectric film, and the first through hole or the second through hole is formed on a part of the dielectric films;

[0021] the first conductive pattern or the second conductive pattern is printed on each dielectric film;

[0022] a part of the dielectric films printed with the first conductive pattern and a part of the dielectric films printed with the second conductive pattern are alternately stacked on one magnetic core layer, after each dielectric film is stacked, the conductive material is filled into the first through hole or the second through hole until the first inductive coil and the second inductive coil are formed, and the magnetic insulating material is filled into the avoidance hole to form the magnetic core column;

[0023] the insulating magnetic material is cast on the last dielectric film to form another magnetic core layer, thereby forming a magnetic core unit;

[0024] both ends of the first inductive coil and the second inductive coil are exposed outside the substrate, thereby forming the input end, the first output end, the second output end and the ground end, thereby forming the balun structure.

[0025] The preparation method of the balun structure in the second aspect can be applied to the balun structure in the first aspect, and the same effects as the balun structure in the first aspect are achieved, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description only constitute some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0027] Figure 1 The outer structure schematic diagram of the balun structure provided by the embodiments of the present application is shown in the figure.

[0028] Figure 2 The partial structure schematic diagram of the balun structure in the figure is shown in the figure. Figure 1

[0029] Figure 3 The internal structure schematic diagram of the balun structure in the figure is shown in the figure. Figure 1

[0030] Figure 4 The exploded view of the figure is shown in the figure. Figure 3

[0031] Figure 5 The equivalent circuit diagram of the balun structure provided by the embodiments of the present application is shown in the figure.

[0032] Figure 6 The preparation method flow chart of the balun structure provided by the embodiments of the present application is shown in the figure.

[0033] Figure 7 The simulation curve diagram of the insertion loss of the balun structure of one embodiment of the present application is shown in the figure.

[0034] Figure 8 The simulation curve diagram of the amplitude imbalance of the balun structure of one embodiment of the present application is shown in the figure.

[0035] Figure 9 The simulation curve diagram of the phase imbalance of the balun structure of one embodiment of the present application is shown in the figure.

[0036] In the figure, various reference signs are as follows:

[0037] 10, substrate; 101, input end; 102, first output end; 103, second output end; 104, ground end; 11, dielectric film; 12, magnetic core unit; 121, magnetic core layer; 122, common magnetic core column; 123, first magnetic core column;

[0038] 20, first inductor coil; 21, first conductive pattern; 22, first via conductor;

[0039] 30, second inductor coil; 31, second conductive pattern; 32, second via conductor;

[0040] 40, avoiding hole.​​​ DETAILED DESCRIPTION

[0041] In order to make the technical problems to be solved, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application, and not to limit the present application.

[0042] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0043] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0044] In addition, the terms "first", "second", "third", etc. are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0045] Electronic technology is developing towards multi-function, miniaturization and high reliability, and low temperature co-fired ceramic technology (abbreviation of Low-Temperature Co-fired Ceramics, hereinafter referred to as: LTCC) is attracting more and more attention. As a balanced and unbalanced converter, the balun is widely used in microwave systems such as antennas, mixers, frequency multipliers, etc., and is an important element in microwave systems. The laminated balun is a balun structure made of ceramic membrane through LTCC. LTCC technology refers to the low temperature sintering ceramic powder into a green ceramic tape with accurate thickness and density, as a circuit substrate material, and the required pattern conductor is made on the green ceramic tape by laser drilling, micro-hole grouting, and precise conductor paste printing process, and a plurality of passive elements are embedded therein, and then stacked together, and sintered at about 900℃ to form a three-dimensional circuit network of passive integrated components. It can also be made into a three-dimensional circuit substrate with built-in passive elements, and IC and active devices can be mounted on its surface to form a passive / active integrated functional module.

[0046] The balun structure in related technologies is usually a stacked sheet structure. For example, a balun structure with a length of 2mm and a width of 1.2mm (the size here refers to the package size of the balun structure) has the advantages of small size, high reliability and simple manufacturing process, which meets the requirements of miniaturization, high reliability, high performance and low cost of downstream electronic devices. However, the lower limit of the frequency band that this balun structure can reach is usually greater than 200 MHz, making it difficult to achieve the goal of extending to the frequency band below 200 MHz while meeting the requirements of miniaturization.

[0047] In order to enable the balun structure in related technologies to extend to the frequency band below 200 MHz, this application provides a balun structure.

[0048] like Figures 1 to 5 As shown, the balun structure includes a substrate 10, a first inductor coil 20, and a second inductor coil 30. The substrate 10 includes a dielectric film 11 and a magnetic core unit 12. The magnetic core unit 12 includes two magnetic core layers 121 and three spaced magnetic core pillars. The two magnetic core layers 121 are stacked on opposite sides of the dielectric film 11, and each magnetic core pillar penetrates the dielectric film 11 to connect the two magnetic core layers 121. The first inductor coil 20 is located between the two magnetic core layers 121 and is spirally wound between the three magnetic core pillars. The second inductor coil 30 is located between the two magnetic core layers 121 and is spirally wound between the three magnetic core pillars. The second inductor coil 30 is coupled to the first inductor coil 20. The outer surface of the substrate 10 is provided with an input terminal 101, a first output terminal 102, a second output terminal 103 and a ground terminal 104. One end of the first inductor coil 20 is electrically connected to the input terminal 101 and the other end is electrically connected to the ground terminal 104. The two ends of the second inductor coil 30 are electrically connected to the first output terminal 102 and the second output terminal 103, respectively.

[0049] The balun structure substrate 10 provided in this application is composed of a dielectric film 11 and a magnetic core unit 12. The first inductor coil 20 and the second inductor coil 30 are both located between two magnetic core layers 121 and are spirally wound between three magnetic core pillars. The first inductor coil 20 and the second inductor coil 30 are coupled under the action of the magnetic field formed by the magnetic core unit 12. In this way, the balun structure has magnetic coupling characteristics, which can give full play to the advantages of magnetic materials and dielectric materials, so that the balun structure can achieve the purpose of extending to the low frequency band on the basis of miniaturization, thereby achieving the purpose of balancing miniaturization design and extension to the low frequency band.

[0050] It should be noted that the dielectric film sheet 11 can generally adopt a dielectric ceramic material, the magnetic core unit 12 adopts a magnetic insulating material such as ferrite, the first inductor coil 20 and the second inductor coil 30 adopt a conductive material, and the above-mentioned balun structure is made by a heterogeneous laminated co-firing process. The heterogeneous laminated co-firing is based on a low-temperature co-fired ceramic (LTCC) process technology, and two or more materials and a conductor paste are co-fired to realize product multifunctionalization and high integration. Compared with the balun structure in the related art with a length of 2 mm and a width of 1.2 mm, the balun structure in the embodiment is co-fired by a dielectric ceramic material, a magnetic insulating material, and a conductive paste, so that the balun structure can be expanded to a frequency band lower than 200 megahertz or even lower.

[0051] As shown in Figure 2 some embodiments, three magnetic core columns are arranged along a direction perpendicular to the thickness direction of the dielectric film sheet 11, and the magnetic core column in the middle is the common magnetic core column 122, and the two magnetic core columns other than the common magnetic core column 122 are the first magnetic core columns 123. The first inductor coil 20 and the second inductor coil 30 are both spirally wound around the common magnetic core column 122, and the projections of the first inductor coil 20 and the second inductor coil 30 on the magnetic core layer 121 are staggered along the thickness direction.

[0052] Through the above arrangement, it is not only beneficial to reduce the parasitic capacitance between the coupled lines of the first inductor coil 20 and the second inductor coil 30, but also beneficial to ensure that the amplitude-frequency characteristic and the phase characteristic of the upper limit of the bandpass are excellent.

[0053] As shown in Figure 4 some embodiments, the number of dielectric film sheets 11 is a plurality, the first inductor coil 20 includes a plurality of first conductive patterns 21 and a first via conductor 22, the plurality of first conductive patterns 21 are printed on the plurality of dielectric film sheets 11, and the first via conductor 22 connects two adjacent first conductive patterns 21; the second inductor coil 30 includes a plurality of second conductive patterns 31 and a second via conductor 32, the second conductive patterns 31 are printed on the plurality of dielectric film sheets 11, and the second via conductor 32 connects two adjacent second conductive patterns 31; along the thickness direction, the dielectric film sheet 11 on which the first conductive pattern 21 is printed and the dielectric film sheet 11 on which the second conductive pattern 31 is printed are alternately and laminatedly arranged.

[0054] Through the above arrangement, the parasitic capacitance between the coupled lines of the first inductor coil 20 and the second inductor coil 30 is further reduced, and the amplitude-frequency characteristic and the phase characteristic of the high-frequency band (upper limit of the frequency band) are effectively ensured to be excellent.

[0055] For example, the number of dielectric films 11 is six, wherein the first conductive pattern 21 includes 21a, 21b, and 21c, the first via conductor 22 includes 22a and 22b, the second conductive pattern 31 includes 31a, 31b, and 31c, and the second via conductor 32 includes 32a and 32b. The first conductive patterns 21a, 21b, and 21c, and the second conductive patterns 31 include 31a, 31b, and 31c, which are arranged in an alternating layer. This facilitates the three-dimensional spiral winding of the first inductor coil 20 and the second coil around the common magnetic core pillar 122 along the thickness direction of the dielectric film 11. Furthermore, along the thickness direction of the dielectric film 11, some patterns in the first conductive pattern 21 and the second conductive pattern 31 can be designed to include planar spiral structures, such as 21a, 21b, 31a, and 31b. This not only helps to ensure that the first inductor coil 20 and the second inductor coil 30 have the same number of turns, but also helps to reduce parasitic capacitance.

[0056] Of course, the number of dielectric membranes 11 can also be any number other than six, and no specific limitation is made here.

[0057] like Figure 3 and Figure 4 As shown, in some embodiments, each dielectric film 11 is printed with a first conductive pattern 21 or a second conductive pattern 31; a first through hole is formed at intervals on a portion of the dielectric films 11 on which the second conductive pattern 31 is printed, and a second through hole is formed at intervals on a portion of the dielectric films 11 on which the first conductive pattern 21 is printed. The first through hole and the second through hole are both used to fill conductive material to form a first through hole conductor 22 and a second through hole conductor 32, respectively.

[0058] The above settings further reduce the parasitic capacitance between the coupling lines of the first inductor coil 20 and the second inductor coil 30.

[0059] like Figure 4 As shown, in some embodiments, the number of first conductive patterns 21 and the number of second conductive patterns 31 are the same. This is advantageous because it allows the structures of the first inductor coil 20 and the second inductor coil 30 to be the same or similar, thereby helping to reduce the parasitic capacitance between the coupling lines of the first inductor coil 20 and the second inductor coil 30.

[0060] like Figure 4 As shown, in some embodiments, each dielectric diaphragm 11 has a clearance hole 40, which is used to fill magnetic insulating material to form a magnetic core pillar. For example, the clearance hole 40 includes a first clearance hole 40 and a second clearance hole 40. The first clearance hole 40 is used to form a common magnetic core pillar 122, and the second clearance hole 40 is used to form a first magnetic core pillar 123. Figure 4In order to clearly show the comparison between the first clearance hole 40 and the second clearance hole 40 before and after filling, only the structure of the first magnetic core column 123 formed after the second clearance hole 40 is filled with magnetic slurry is schematically shown in the figure. Of course, the structure of the common magnetic core column 122 formed after the first clearance hole 40 is filled with magnetic slurry can be referred to the first magnetic core column 123.

[0061] With the above settings, magnetic core pillars can be formed by casting magnetic insulating slurry (hereinafter referred to as magnetic slurry) when stacking dielectric films 11. This helps to fill the clearance holes 40 completely with magnetic slurry, thereby increasing the density of the magnetic core pillars and maximizing their function.

[0062] like Figure 2 As shown, in some embodiments, the three core pillars and the two core layers 121 are an integral structure.

[0063] The above configuration ensures that the three magnetic core pillars and the two magnetic core layers 121 are reliably connected, thereby enhancing the magnetic field formed by the magnetic core unit 12, which in turn facilitates the expansion of the balun structure to lower frequency bands.

[0064] In some embodiments, the three magnetic core pillars and the two magnetic core layers 121 are all made of a magnetic insulating material, which is a ferrite with a permeability of 300 to 1000.

[0065] By using ferrite with a permeability of 300 to 1000 to make the magnetic core unit 12, the permeability characteristics of ferrite can be fully utilized, which is conducive to extending the balun structure to a lower frequency band. For example, the balun structure can reach as low as tens of megahertz.

[0066] like Figure 2 As shown, in some embodiments, the cross-sectional area of ​​the common magnetic core post 122 is larger than the cross-sectional area of ​​each first magnetic core post 123, wherein the cross-section is a section perpendicular to the thickness direction.

[0067] By increasing the cross-sectional area of ​​the common magnetic core column 122, the common magnetic circuit is strengthened, which helps to reduce the parasitic capacitance between the coupling lines of the first inductor coil 20 and the second inductor coil 30.

[0068] In some embodiments, the wire diameter of the first inductor coil 20 and the second inductor coil 30 is 40μm to 80μm.

[0069] If the wire diameter of the first inductor coil 20 and the second inductor coil 30 is too large, the size of the balun structure will be too large. If the wire diameter is too small, the first inductor coil 20 and the second inductor coil 30 will be difficult to process. Reducing the wire diameter of the first inductor coil 20 and the second inductor coil 30 not only helps to achieve miniaturization of the balun structure, but also reduces parasitic capacitance.

[0070] For example, the wire diameter of the first inductive coil 20 and the second inductive coil 30 can be 60 μm. The thickness of the first inductive coil 20 and the second inductive coil 30 along the thickness direction of the dielectric film sheet 11 is 10 μm.

[0071] In some embodiments, the wire spacing of the first inductive coil 20 and the second inductive coil 30 is equal to the wire diameter.

[0072] If the wire spacing of the first inductive coil 20 and the second inductive coil 30 is too small or the wire diameter of the conductive coil is too small, a larger parasitic capacitance is generated. If the wire spacing is too large, the size of the balun structure is large. Through the above setting, the balun structure can be miniaturized and the parasitic capacitance can be reduced.

[0073] For example, the wire spacing of the first inductive coil 20 and the second inductive coil 30 can be 60 μm.

[0074] In some embodiments, the dielectric film sheet 11 is a dielectric ceramic film sheet, the dielectric constant of the dielectric film sheet 11 is 3-10, and the dielectric loss is less than or equal to 0.01.

[0075] Through the above setting, the balun structure can meet the use requirements in the field of less than 200 megahertz frequency band.

[0076] In some embodiments, the input end 101, the first output end 102, the second output end 103, and the ground end 104 each include a three-layer plating layer, and the plating layer from inside to outside is a silver plating layer, a nickel plating layer, and a tin plating layer. In this way, the three-layer plating layer structure can ensure the welding reliability of the product.

[0077] The sintering temperature of the silver paste in the above plating layer is about 880℃, the silver content of the silver paste is 85%, the silver layer thickness is 10 μm, and the silver layer width is 60 μm.

[0078] As shown in FIG. 1, the balun structure provided by the present application includes an input end 101, a first output end 102, a second output end 103, a ground end 104, and a magnetic core layer 121. Figure 6 The present application also provides a preparation method of the balun structure, which is applied to the balun structure in the above embodiments. The preparation method includes the following steps:

[0079] providing a magnetic core layer 121 and a plurality of dielectric film sheets 11;

[0080] Each dielectric film sheet 11 is provided with a relief hole 40, and a first through hole or a second through hole is provided on a part of the dielectric film sheets 11;

[0081] Each dielectric film sheet 11 is provided with a corresponding first conductive pattern 21 or a second conductive pattern 31;

[0082] The partial number of medium film pieces 11 printed with the first conductive pattern 21 and the partial number of medium film pieces 11 printed with the second conductive pattern 31 are alternately stacked on a magnetic core layer 121, after each layer of medium film piece 11 is stacked, the first through hole or the second through hole is filled with conductive material until the first inductor coil 20 and the second inductor coil 30 are formed, and the magnetic core column is formed by filling the magnetic insulating material into the avoiding hole 40;

[0083] The last medium film piece 11 is cast with the insulating magnetic material to form another magnetic core layer 121, thereby forming a magnetic core unit 12;

[0084] The two ends of the first inductor coil 20 and the second inductor coil 30 are exposed outside the base body 10, thereby forming an input end 101, a first output end 102, a second output end 103 and a ground end 104, thereby forming a balun structure.

[0085] The preparation method of the balun structure in the above embodiment is applied to the balun structure in the above embodiment, which is the same as the balun structure in the above embodiment, and will not be repeated here.

[0086] In one embodiment of the balun structure, six medium film pieces 11 are included, each dielectric film piece uses dielectric ceramic with a dielectric constant of 5 and a dielectric loss less than or equal to 0.01, the magnetic core unit 12 is made of a ferrite slurry with a magnetic permeability of 500 and a solid content of 90%, and the sintering temperature is 880℃; the first inductor coil 20 and the second inductor coil 30 are made of silver paste, the silver paste sintering temperature is 875℃, the silver paste silver content is 85%, the silver layer thickness is 10μm, and the silver layer line diameter (width) is 60μm; the first inductor coil 20 and the second inductor coil 30 each include three layers, as shown in Figure 4 The first conductive pattern 21 of the first inductor coil 20 includes 21a, 21b and 21c, and the first through hole conductor 22 includes 22a and 22b; the second conductive pattern 31 of the second inductor coil 30 includes 31a, 31b and 31c, and the second through hole conductor 32 includes 32a and 32b; and 21a, 21b and 21c in the first conductive pattern 21, 31a, 31b and 31c in the second conductive pattern 31 are alternately stacked;

[0087] One end of the first inductor coil 20 is electrically connected to the input end 101, and the other end is electrically connected to the ground end 104; the two ends of the second inductor coil 30 are respectively electrically connected to the first output end 102 and the second output end 103, thereby forming a voltage type balun structure, and the equivalent circuit of the balun structure is as shown in Figure 5 ;

[0088] The input terminal 101, the first output terminal 102, the second output terminal 103 and the ground terminal 104 each include three layers of plating, and the plating layers from inside to outside are silver plating, nickel plating and tin plating in sequence, the silver paste sintering temperature in the plating is 880 DEG C, the silver paste silver content is 85%+ / -5%, the silver layer thickness is 10 mu m, and the silver layer width is 60 mu m.

[0089] Through simulation, the band pass of the balun structure in the above embodiment can reach 10MHz-350MHz, the insertion loss in the passband is ≤3dB, as shown in Figure 7 , the amplitude imbalance is ≤0.35dB, as shown in Figure 8 , and the phase imbalance is ≤15°, as shown in Figure 9 .

[0090] The above only is the preferred embodiment of the present application, and does not limit the present application, any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A balun structure, characterized by, The base body (10) comprises a dielectric film (11) and a magnetic core unit (12), the magnetic core unit (12) comprises two magnetic core layers (121) and three spaced magnetic core columns, the two magnetic core layers (121) are respectively laminated on opposite sides of the dielectric film (11), and each of the magnetic core columns penetrates through the dielectric film (11) to connect the two magnetic core layers (121), and the three magnetic core columns and the two magnetic core layers (121) are all made of magnetic insulating material; The first inductor coil (20) is located between the two magnetic core layers (121) and is spirally wound between the three magnetic core columns; The second inductor coil (30) is located between the two magnetic core layers (121) and is spirally wound between the three magnetic core columns, and the second inductor coil (30) is coupled with the first inductor coil (20); Wherein, the outer surface of the base body (10) is provided with an input end (101), a first output end (102), a second output end (103) and a ground end (104), one end of the first inductor coil (20) is electrically connected with the input end (101), the other end is electrically connected with the ground end (104), and the two ends of the second inductor coil (30) are respectively electrically connected with the first output end (102) and the second output end (103); the three magnetic core columns are arranged along the direction perpendicular to the thickness direction of the dielectric film (11), and the magnetic core column located in the middle is a common magnetic core column (122), and the two magnetic core columns except the common magnetic core column (122) are first magnetic core columns (123), the first inductor coil (20) and the second inductor coil (30) are spirally wound around the common magnetic core column (122), and along the thickness direction, the projections of the first inductor coil (20) and the second inductor coil (30) on the magnetic core layer (121) are staggered, so as to reduce the parasitic capacitance between the coupling lines of the first inductor coil (20) and the second inductor coil (30).

2. The balun structure according to claim 1, wherein The number of the dielectric films (11) is multiple, the first inductor coil (20) comprises multiple first conductive patterns (21) and a first via conductor (22), the multiple first conductive patterns (21) are printed on the multiple dielectric films (11), and the first via conductor (22) connects two adjacent first conductive patterns (21); The second inductor coil (30) comprises multiple second conductive patterns (31) and a second via conductor (32), the second conductive patterns (31) are printed on the multiple dielectric films (11), and the second via conductor (32) connects two adjacent second conductive patterns (31); Along the thickness direction, the dielectric films (11) on which the first conductive patterns (21) are printed and the dielectric films (11) on which the second conductive patterns (31) are printed are alternately laminated.

3. The balun structure according to claim 2, wherein ​ Each of the dielectric films (11) is printed with the first conductive pattern (21) or the second conductive pattern (31); a first through hole is formed on a part of the dielectric films (11) printed with the second conductive pattern (31), and a second through hole is formed on a part of the dielectric films (11) printed with the first conductive pattern (21); the first through hole and the second through hole are both filled with conductive material to form the first through-hole conductor (22) and the second through-hole conductor (32), respectively. The number of the first conductive patterns (21) is the same as the number of the second conductive patterns (31).

4. The balun structure according to claim 3, wherein, Each of the dielectric films (11) is provided with a relief hole (40) filled with magnetic insulation material to form the magnetic core column.

5. The balun structure according to any one of claims 1-4, wherein, The cross-sectional area of the common magnetic core column (122) is greater than the cross-sectional area of each first magnetic core column (123), wherein the cross-section is perpendicular to the thickness direction.

6. The balun structure according to any one of claims 1-4, wherein, The wire diameter of the first inductor coil (20) and the second inductor coil (30) is 40-80 μm; and / or the wire spacing of the first inductor coil (20) and the second inductor coil (30) is equal to the wire diameter.

7. The balun structure according to any one of claims 1-4, wherein, The dielectric film (11) is a dielectric ceramic film, the dielectric constant of the dielectric film (11) is 3-10, and the dielectric loss is less than or equal to 0.

01. The method comprises:

8. A method of manufacturing a balun structure for use in a balun structure as claimed in claim 4, characterized in that, providing one of the magnetic core layers and a plurality of the dielectric films; forming the relief hole on each of the dielectric films, and forming the first through hole or the second through hole on a part of the dielectric films; printing the corresponding first conductive pattern or the second conductive pattern on each of the dielectric films; alternately stacking the dielectric films printed with the first conductive pattern and the dielectric films printed with the second conductive pattern on one of the magnetic core layers; after stacking one of the dielectric films, filling the first through hole or the second through hole with the conductive material until the first inductor coil and the second inductor coil are formed, and filling the relief hole with the magnetic insulation material to form the magnetic core column; casting the magnetic insulation material on the last dielectric film to form another of the magnetic core layers, thereby forming a magnetic core unit; exposing both ends of the first inductor coil and the second inductor coil outside the substrate, thereby forming the input end, the first output end, the second output end, and the ground end, and thereby forming the balun structure. ​

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