Patent Application
20230298807
This application claims priority to and the benefit of Chinese Invention Patent Application No. 202210276883.3 filed Mar. 21, 2022. The disclosure of this application identified in this paragraph is incorporated herein by reference in its entirety.
The present invention relates to the field of electronic devices, specifically to a multilayer inductor structure for power applications. In particular, the multilayer inductor is used for voltage to current conversion for power transmission, impedance matching for data transmission and processing, and filtering of electromagnetic interference.
As one of the passive devices, inductors can usually be classified into: winding type inductors, which are manufactured by winding a coil around a ferrite core and forming electrodes at its ends; and multilayer type inductors, which are manufactured by printing an inner electrode on a magnetic or dielectric layer and then stacking the magnetic or dielectric layers together.
In recent years, the development of thick film printing processes and LTCC materials has led to the need for further miniaturization of passive devices such as resistors, capacitors, and inductors. In small circuit boards, multilayer inductors are gradually gaining dominance as the best SMT inductor solution for size miniaturization and low cost, compared to winding type inductors.
Typically, multilayer inductors consist of a single monolithic structure formed by a multilayer body consisting of multiple magnetic sheets (or strips) that undergo a high-temperature solid-phase reaction. The conductive electrodes can be formed as the coil pattern on the magnetic sheets by printing (but not limited to printing). With the development of technology, various aspects of research exist in the prior art to improve the multilayer inductor structures.
For this, U.S. Pat. No. 6,249,205 proposes a multilayer inductor that provides high inductance by introducing an air gap between the layers of the multilayer inductor. But such air gaps would cause problems in performance fluctuation of the inductor.
Therefore, the drawbacks of the multilayer inductors, e.g., inductance and impedance instability under different application conditions such as current, frequency, temperature, etc., have not been addressed in this field so far.
In an aspect, generally, when preparing the body, non-magnetic ceramics are chosen in this field instead of the air gap to regulate the characteristics of the inductor and stability thereof. But there is a problem in that the characteristics of these non-magnetic ceramics will also deviate with temperature and frequency. In this regard, the applicant has found that the source of instability of non-magnetic ceramics in the gap position of the magnetic core area to current, temperature, and frequency is the deviation of the dielectric constant.
Therefore, a technical object of the present invention is to provide a ceramic-inorganic material composite that fills such gap positions, which can eliminate the deviation of the dielectric constant of the magnetic core with current, temperature, and frequency, thereby realizing a multilayer inductor structure with stable characteristics.
In another aspect, in the prior art, the multilayer inductor is manufactured by a process of printing metal electrode tracks on the magnetic sheet, utilizing static pressing, and then co-firing. Therefore, the thickness of the magnetic sheet should not be too small in consideration of the operability of this manufacturing process. As a result, there is a high percentage of void space between two adjacent layers of metal electrode tracks where no effective magnetic lines of force exist, giving no contribution to inductor performance. The applicant has found that the void space can be maximally compressed by reducing the space between the metal electrode tracks of two adjacent layers or by changing the arrangement of the metal electrode tracks.
Therefore, another technical object of the present invention is to provide a multilayer inductor that enables minimization of the void space where no effective magnetic lines of force exist, and thus enhances the characteristics of the multilayer inductor (e.g., enhancing the effective magnet utilization of the multilayer inductor), thereby enhancing the characteristics of the inductor, such as inductance value enhancement, current stability improvement, and impedance characteristic optimization of the inductor.
In order to solve the above technical problem, in an aspect, the present invention provides a ceramic-inorganic material composite for a multilayer inductor, which is located in the magnetic core area of metal electrode tracks present in the pattern of coils and comprises two or more first layers and second layers, wherein the first layers comprise a ceramic material having a positive slope in a curve of the dielectric constant versus temperature, the second layers comprise an inorganic material having a negative slope in a curve of the dielectric constant versus temperature, and the first layers and the second layers are stacked on each other in an alternating manner.
In this aspect, the ceramic material having a positive slope in a curve of the dielectric constant versus temperature can be almost any ceramic material commonly used in the art, for example, those selected from commercially available materials such as titanium dioxide, zirconium dioxide, etc.
The inorganic material having a negative slope in a curve of the dielectric constant versus temperature can be selected from commercially available materials, such as calcium carbonate, calcium bicarbonate, calcium oxide, etc.
The metal electrode comprises silver (Ag), platinum (Pt), palladium (Pd), copper (Cu), gold (Au), nickel (Ni), or alloys thereof, or composites thereof.
In this aspect, it further relates to a multilayer inductor comprising a plurality of magnetic layers and metal electrode tracks formed on the magnetic layers, wherein a ceramic-inorganic material composite is disposed in the magnetic core area formed by the metal electrode tracks in the pattern of coils, the ceramic-inorganic material composite comprises two or more first layers and second layers, wherein the first layers comprise a ceramic material having a positive slope in a curve of the dielectric constant versus temperature, the second layers comprise an inorganic material having a negative slope in a curve of the dielectric constant versus temperature, and the first layers and the second layers are stacked on each other in an alternating manner.
In the second aspect, the present invention provides a multilayer inductor comprising a plurality of magnetic layers and metal electrode tracks formed on the magnetic layers, wherein the metal electrode tracks are arranged in such a way that the void space between two adjacent metal electrode tracks where no effective magnetic lines of force exist is minimized.
According to the second aspect, the metal electrode tracks are arranged in such a way that multilayer metal electrode tracks of the multilayer inductor are closely arranged in the vertical direction, so that the overall thickness of the magnetic layers between the metal electrode tracks is 10 μm or less.
In the second aspect, the plurality of magnetic layers and metal electrode tracks are formed by printing, etching, and laser methods. Among them, in forming the plurality of magnetic layers and metal electrode tracks by multiple printing techniques, the thickness of the magnetic or metal layers is 5 μm or less for each printing.
According to the second aspect, alternatively, the metal electrode tracks are arranged in such a way that multilayer metal electrode tracks of the multilayer inductor are arranged in a stepwise mismatch on a cross section perpendicular to the plurality of magnetic layers.
Specifically, with respect to the metal electrode tracks of a lower layer, the metal electrode tracks of an upper layer are mismatched to the left or right layer by layer in a step-like manner.
The material of magnetic layers can be a ferrite material.
In the third aspect, the present invention provides a multilayer inductor comprising a plurality of magnetic layers and metal electrode tracks formed on the magnetic layers, wherein a ceramic-inorganic material composite is placed in the magnetic core area in the pattern of coils formed by the metal electrode tracks, the ceramic-inorganic material composite comprises two or more first layers and second layers, wherein the first layers comprise a ceramic material having a positive slope of the dielectric constant versus temperature curve, the second layers comprise an inorganic material having a negative slope of the dielectric constant versus temperature curve, and the first layers and the second layers are stacked on each other in an alternating manner; and the metal electrode tracks are arranged in such a way that the void space between two adjacent metal electrode tracks where no effective magnetic lines of force exist is minimized.
According to the first aspect of the present invention, the ceramic-inorganic material composite of the multilayer inductor of the present invention can eliminate the deviation of the dielectric constant of the core with current, temperature, and frequency, thereby realizing a multilayer inductor structure with stable characteristics.
According to the second aspect of the present invention, the void space between the metal electrode tracks of the multilayer inductor is minimized, thus allowing the available magnetic capacity of the core to increase and the DC resistance to decrease.
In addition, by aligning the metal electrode tracks closely, subsequent processes (e.g., sintering) can be performed without creating delamination or machine shrinkage rate anisotropy that can lead to product distortion, cracking, and unstable reliability.
According to a third aspect of the present invention, the multilayer inductors can improve the electrical and magnetic performances of the device while achieving stable characteristics, and thus enhances the effective magnet utilization of the multilayer inductor, thereby enhancing the characteristics of the inductor, such as inductance value enhancement, current stability improvement, and impedance characteristic optimization of the inductor.
The accompanying drawings depicted herein are for the purpose of illustrating selected examples only, not all possible embodiments, and are not intended to limit the scope of the present invention.
In the following, the present invention will be described in more detail.
It is to be understood that the terms used in the specification and claims may be construed to have a meaning consistent with their meaning in the context of the relevant field and the technical contemplation of the present invention, based on the principle that they may be appropriately defined by the inventor. The terms used in the specification are intended to explain exemplary embodiments only and are not intended to limit the invention.
It is further understood that, when used in this specification, the terms “comprise”, “include”, “contain”, or “have” when used in this specification indicates the presence of the stated feature, figure, step, element, or combination thereof, but does not exclude the presence or inclusion of one or more other features, figures, steps, elements, or combinations thereof.
In this document, when describing the structure of a component with reference to the accompanying drawings, the terms “upper”, “lower”, “upper layer”, “lower layer” and the like refer to the relative position relationship of the component and are not limited to the structure shown in the accompanying drawings.
Hereafter, the multilayer inductor of the present invention will be described.
First, referring to
In this regard, referring to
The ceramic-inorganic material composite of the present invention can be located at any position in the magnetic core area 103, such as the position shown in the long black area of
As described above, in the first aspect, the present invention provides a ceramic-inorganic material composite for multilayer inductor, which is located in the magnetic core area of metal electrode tracks present in the pattern of coils and comprises two or more first layers and second layers, wherein the first layers comprise a ceramic material having a positive slope of the dielectric constant versus temperature curve, the second layers comprise an inorganic material having a negative slope of the dielectric constant versus temperature curve, and the first layers and the second layers are stacked on each other in an alternating manner.
In this regard, referring to
Here, “slope of the dielectric constant versus temperature curve” has the meaning of rate of change of the dielectric constant of the material in the dielectric constant versus temperature curve as it becomes larger or smaller with temperature. If it becomes larger, the slope is positive, and vice versa.
Preferably, the ceramic material having a positive slope in a curve of the dielectric constant versus temperature has a slope between 0.1 and 1; and the inorganic material having a negative slope in a curve of the dielectric constant versus temperature has a slope between −0.1 and 0.05.
Although only a ceramic-inorganic material composite having a two-layer structure is illustrated in
The ceramic-inorganic material composite 200 shown in
After embedding the magnetic core area of the multilayer inductor, the ceramic material having a positive slope in a curve of the dielectric constant versus temperature and the inorganic material having a negative slope in a curve of the dielectric constant versus temperature overlap each other to eliminate the deviation of the dielectric constant of the core with current, temperature and frequency, thus realizing a multilayer inductor structure body with stable characteristics.
In the first aspect, it further relates to a multilayer inductor comprising a plurality of magnetic layers and metal electrode tracks formed on the magnetic layers, wherein a ceramic-inorganic material composite is placed in the magnetic core area in the pattern of coils formed by the metal electrode tracks, the ceramic-inorganic material composite comprises two or more first layers and second layers, wherein the first layers comprise a ceramic material having a positive slope in a curve of the dielectric constant versus temperature, the second layers comprise an inorganic material having a negative slope in a curve of the dielectric constant versus temperature, and the first layers and the second layers are stacked on each other in an alternating manner.
In such aspect, in this field, almost all commonly used ceramic materials are ceramic materials having a positive slope in a curve of the dielectric constant versus temperature, and thus they can be used as the ceramic materials herein. Usually, the ceramic materials having a positive slope in a curve of the dielectric constant versus temperature can be commercially available materials, such as titanium dioxide, zirconium dioxide, etc.
The inorganic material having a negative slope in a curve of the dielectric constant versus temperature can be selected from commercially available materials, such as calcium carbonate, calcium bicarbonate, calcium oxide, etc.
The metal electrode comprises silver (Ag), platinum (Pt), palladium (Pd), copper (Cu), gold (Au), nickel (Ni), or alloys thereof, or composites thereof.
The material of the magnetic layers can be a magnetic material, e.g., a magnetic ceramic material, pertaining a main category of ferrite material, preferably a nickel-zinc-copper ferrite material. For example, ferrite powders comprise iron oxide powder, zinc oxide powder, copper oxide powder, nickel oxide powder, bismuth oxide powder, and a small amount of silicon oxide powder.
The ceramic-inorganic material composite of the present invention can be prepared by a method as follows:
A ceramic material having a positive slope in a curve of the dielectric constant versus temperature (and optional modifying agent) and an inorganic material having a negative slope in a curve of the dielectric constant versus temperature (and optional modifying agent) are dissolved in a solvent for dispersion to obtain a slurry A containing the ceramic material having a positive slope in a curve of the dielectric constant versus temperature and a slurry B containing the inorganic material having a negative slope in a curve of the dielectric constant versus temperature. Then, the slurries A and B are alternately applied to the substrate and sintered at high temperature to obtain the ceramic-inorganic material composite.
In the above production method, the solvent used can be selected from ethyl cellulose and pine alcohol.
In the above production method, the ceramic and inorganic materials used are as described above.
In the above production method, the purpose of adding the modifying agent is to change the surface energy and activity of the slurry particle surface, so that the resulting product is less prone to agglomeration which may affect the processing quality. The modifying agent is preferably M1159 material from FERRO, and preferably, the modifying agent is stirred together with the ceramic material or inorganic material before adding into the solvent.
In the above production method, the dispersion process is carried out using a ball mill for 3 to 5 hours, for example 4 hours.
In the above production method, the substrate is a magnetic substrate for magnetic layers used in the multilayer inductor.
In the above production method, the slurries A and B are alternately printed on the substrate by an alternating printing process.
In the above production method, the sintering temperature is from 800° C. to 950° C., for example 900° C., and the time may be a suitable time commonly used in the art.
In the second aspect, a multilayer inductor comprising a plurality of magnetic layers and metal electrode tracks formed on the magnetic layers, wherein the metal electrode tracks are arranged in such a way that the void space between two adjacent metal electrode tracks where no effective magnetic lines of force exist is minimized is provided.
Referring to
Specifically, referring to the left side of
In the present invention, the applicant has found that the void space between two adjacent metal electrode tracks where no effective magnetic lines of force exist can be minimized by changing the arrangement of the metal electrode tracks, thereby enhancing the performance of the multilayer inductor device.
According to the second aspect, as the solution 1, the metal electrode tracks can be arranged in such a way that multilayer metal electrode tracks of the multilayer inductor are closely arranged in the vertical direction, so that the overall thickness of the magnetic layers between the metal electrode tracks is 100 μm or less.
Specifically, no metal electrode tracks are formed in the bottommost magnetic layer 501b. Then, a layer of metal electrode tracks, e.g., 502a, is first formed on the next lower layer using a multiple printing technique, and another magnetic layer 501c is printed on top of the metal electrode tracks. This procedure is repeated until multiple layers (e.g., 3 or 4 layers) of metal electrode tracks and magnetic layers are formed, in which 502a and 501c are laminated on top of each other. In addition, the two layers of metal electrode tracks 502a can be connected by mesh 503. As the mesh, an aluminum alloy mesh can be used with intermediate openings of 0.01 to 0.1 millimeter (mm) thickness and a tensile strength of 35 to 50 Newtons (N).
The process of the multiple printing technique is as follows:
First, a slurry for the magnetic layer is prepared. Here, a binder, dispersant, defoamer and ceramic powder (ferrite material) are added separately to the solvent and dispersed in a ball mill for 3 to 8 hours (h) to produce a slurry with a viscosity of 200 to 600 centipoise (CPS).
The solvent, binder, dispersant, defoamer and the like used to prepare the slurry can be materials commonly used in the art and will be omitted from description here.
Subsequently, the slurry for forming the magnetic layer and the metal slurry (e.g. silver slurry) are printed in stacking manner by using a mesh, according to the design requirements. The specific process steps are as follows:
(1) The thickness of the magnetic or metallic layer is 5 μm or less for each printing and is dried by baking at 50 ° C. to 70 ° C. for 1 h after each printing, resulting in a multilayer structure, i.e., multilayer metallic electrodes or multilayer magnetic layers, with a total thickness of 100 μm or less,
(2) A mesh structure (e.g., ½, ⅓, ¼ mesh) is used for the connection points of the metal electrode tracks to ensure that the metal electrode tracks between different layers can form a complete coil.
Secondly, according to the second aspect, as the solution 2, the metal electrode tracks are arranged in such a way that multilayer metal electrode tracks of the multilayer inductor are arranged in a stepwise mismatch on a cross section perpendicular to the plurality of magnetic layers. Specifically, with respect to the metal electrode tracks of a lower layer, the metal electrode tracks of an upper layer are mismatched to the left or right layer by layer in a step-like manner.
In this regard, firstly, referring to
As shown in
Depending on the difference in device design, the metal electrode tracks of the upper layer are mismatched to the left or right at different distances with respect to the metal electrode tracks of the lower layer.
In the second aspect, the metal electrode comprises silver (Ag), platinum (Pt), palladium (Pd), copper (Cu), gold (Au), nickel (Ni), or alloys thereof, or composites thereof.
The material of the magnetic layers can be a magnetic material, e.g., a ceramic material having magnetic property, the main category of which is a ferrite material, preferably a nickel-zinc-copper ferrite material.
As described above, the third aspect of the present invention provides a combination of the first and second aspects, i.e., a multilayer inductor comprising a plurality of magnetic layers and metal electrode tracks formed on the magnetic layers, wherein a ceramic-inorganic material composite is placed in the magnetic core area in the pattern of coils formed by the metal electrode tracks, the ceramic-inorganic material composite comprises two or more first layers and second layers, wherein the first layers comprise a ceramic material having a positive slope in a curve of the dielectric constant versus temperature, the second layers comprise an inorganic material having a negative slope in a curve of the dielectric constant versus temperature, and the first layers and the second layers are stacked on each other in an alternating manner; and the metal electrode tracks are arranged in such a way that the void space between two adjacent metal electrode tracks where no effective magnetic lines of force exist is minimized.
Characteristics of the ceramic-inorganic material composite and the arrangement of the metal tracks are the same as in the first aspect and/or the second aspect, and thus the detailed descriptions thereof are omitted herein.
In the following, the present invention will be explained in detail with reference to examples. However, examples of the present invention may be modified into various other types, and the scope of the present invention should not be limited to the embodiments described below. The examples of the present invention are provided for the purpose of explaining the invention in its entirety to a person having ordinary knowledge in the art.
A prior art multilayer inductor, having the structure shown in
Example 1: The multilayer inductor of the present invention (comprising a ceramic-inorganic material composite and closely arranged multilayer metal electrode tracks)
By using the ultra-fine ferrite powder as raw material and the above-mentioned oily organic substances as additives, the slurry was prepared by ball milling process and the magnetic body was prepared by the test cast machine.
Each of titanium dioxide and limestone powders were dissolved in ethyl cellulose and pine oil alcohol as solvents, and a modifying agent (e.g., M1159 material from FERRO) was added, followed by ball milling for 4 hours using a ball mill to obtain two slurries: a titanium dioxide-based ceramic body with a positive temperature coefficient of dielectric constant based on, and a limestone-based inorganic body with a negative dielectric constant.
Then, by using an alternating printing process, the two slurries were printed on the core substrate, respectively, and this composite ceramic body was obtained by high temperature sintering at about 900° C.
The closely arranged multilayer electrode structure was obtained as follows:
Each of a binder, dispersant, defoamer and ceramic powder was added in a ball mill and subjected to ball milling for 8 h to produce a slurry with a viscosity of 400 CPS, thereby obtaining a slurry for forming the magnetic layer.
A silver slurry was used as the material for forming the electrode tracks. The slurry for magnetic layer and the silver slurry were stacked and printed by using a silver mesh, according to the design requirements. The specific process steps were as follows:
For the magnetic layers and metal track layers, the thickness of each printing is 5 μm or less, and each printing needs to be baked at 60° C. for 1 hour after each printing. If the layer thickness does not reach the requirement, several times of printing and baking were performed.
A silver mesh structure (e.g., ½ mesh) was used for the connection points of silver electrode tracks to ensure that the silver electrode between different layers can form a complete coil.
The magnetic body, metal electrode tracks, and ceramic-inorganic material composite were pressed together and sintered at 900° C. to obtain a multilayer inductor. The resulting multilayer inductor contained the ceramic-inorganic material composite and closely arranged metal electrode tracks as described above.
Using the WK3260 series DC source and inductance test instrument and Agilent 4396 spectrum analyzer, electrical performances of the products obtained from Comparative Example 1 and Example 1 were tested, and the results are shown in each of
As seen in
As seen in
In addition, as seen in
The multilayer inductor containing mismatched arrangement of multilayer metal electrodes of this example was prepared in a similar manner as in Example 1, except that the multilayer metal electrodes were formed into the mismatched structure shown in
Using the WK3260 series DC source and inductance test instrument and Agilent 4396 spectrum analyzer, electrical performances of the products obtained from Comparative Example 1 and Example 2 were tested, and the results are shown in
Referring to
With the aid of the teachings present in the foregoing specification and related accompanying drawings, one of skill in the art will be aware of a variety of variations and other embodiments of the technical solutions described herein. Accordingly, it will be understood that the present invention is not limited to the particular embodiments disclosed and that any variations and other embodiments are deemed to be included within the scopes of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022102768833 | Mar 2022 | CN | national |
