A co-fired inductor, its preparation method and application

Abstract

This invention belongs to the field of inductor technology, and relates to a co-fired inductor, its preparation method, and its application. The co-fired inductor includes electrodes and a magnetic core, and an element interdiffusion layer exists at the contact interface between the electrodes and the magnetic core. The preparation method includes at least a low-temperature debinding heat treatment, a sintering heat treatment, and an alloy diffusion heat treatment performed sequentially. This invention forms an element interdiffusion layer at the contact interface between the electrodes and the magnetic core by adding an alloy diffusion heat treatment, effectively avoiding interface cracking and deformation caused by different expansion rates at the electrode-core junction, while simultaneously improving inductor performance and yield, and reducing production costs.

Description

Technical Field

[0001] This invention belongs to the field of inductor technology, and relates to a co-fired inductor, and more particularly to a co-fired inductor, its preparation method and application. Background Technology

[0002] Currently, with the increasing maturity of 5G technology, the AI ​​industry is receiving more and more attention, which has also promoted the multi-functionality of chips and the miniaturization of circuits. Copper co-fired inductors, as an inductor element made by co-firing copper foil and magnetic materials, have the advantages of small size and high integration, and are mainly used in signal transmission fields such as chips and mobile communications.

[0003] Co-firing technology enables precise structural design, resulting in small inductor size and a flattened structure, making it suitable for use in high-density circuits and helping to improve circuit integration. Co-firing inductors have a good inductance quality factor, reducing energy loss and improving circuit efficiency; they also exhibit stable performance and good reliability under environmental conditions such as temperature and frequency variations, making them particularly suitable for high-frequency circuits and meeting the high-frequency performance requirements of modern electronic devices.

[0004] However, existing copper magnet co-firing technology mainly includes debinding heat treatment (200~400℃) and medium-temperature heat treatment (500~800℃). There is almost no metallurgical bonding and element interdiffusion at the junction of the electrode and the magnetic core. The bonding between the electrode and the magnet is poor. The two boundary surfaces are prone to interface cracking and deformation due to different expansion rates. On the one hand, this increases the air gap inside the inductor and reduces the inductance value. On the other hand, this defect increases the stress and coercivity inside the magnet, thereby increasing the hysteresis loss of the magnet and reducing the overall conversion efficiency of the device.

[0005] CN121439466A discloses an inductor element and its manufacturing method, which attempts to prepare a transition layer between the electrode and the magnet to increase the bonding force between the electrode and the magnet and avoid the cracking phenomenon of copper-magnet co-fired inductors. However, this method introduces new non-magnetic materials, which will reduce the content of magnetic materials to a certain extent, resulting in a decrease in volume inductance. At the same time, the newly added plating process will also increase the product cost.

[0006] Therefore, how to provide a co-fired inductor and its preparation method that can effectively avoid interface cracking and deformation caused by different expansion rates at the junction of the electrode and the magnetic core, while improving inductor performance and yield and reducing production costs, has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a co-fired inductor, its preparation method, and its application, which effectively avoids interface cracking and deformation caused by different expansion rates at the junction of electrodes and magnetic cores, while improving inductor performance and yield, and reducing production costs.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a co-fired inductor, comprising electrodes and a magnetic core, wherein an elemental interdiffusion layer exists at the contact interface between the electrodes and the magnetic core.

[0010] This invention utilizes element interdiffusion to form a metallurgical bond at the contact interface between the electrode and the magnetic core, enhancing the bonding force between the two and effectively avoiding interface cracking and deformation caused by different expansion rates at the junction of the electrode and the magnetic core. This eliminates parasitic air gaps inside the device from the root, thereby significantly improving the overall electrical performance, mechanical performance, and yield of the inductor.

[0011] And / or, the electrode is made of Cu or a Cu alloy, and the Cu content in the Cu alloy is ≥98wt%.

[0012] And / or, the material of the magnetic core includes at least one of FeSiAl, FeSi, FeSiCr or FeNi.

[0013] And / or, Fe and / or Ni elements diffuse along the contact interface in a 4-59 μm region toward the electrode side.

[0014] And / or, the concentration of Fe element in the 59 μm region along the contact interface toward the electrode side ranges from 0.2 to 4.0 wt%.

[0015] And / or, the concentration of Ni element in the 59 μm region along the contact interface toward the electrode side ranges from 0.1 to 3.0 wt%.

[0016] And / or, Cu element diffuses along the contact interface into a 2-15 μm region toward the core side.

[0017] And / or, the concentration of Cu element in the 15 μm region along the contact interface toward the core side ranges from 0.2 to 4.0 wt%.

[0018] And / or, the concentration distribution of the Fe and / or Ni elements shows a gradient decreasing trend along the contact interface toward the electrode side.

[0019] And / or, the concentration distribution of the Cu element shows a gradient decreasing trend along the contact interface toward the magnetic core side.

[0020] And / or, the diffusion depth of the Fe element along the contact interface toward the electrode side is set to D. Fe The diffusion depth of the Cu element along the contact interface toward the core side is D. Cu Then D is satisfied. Fe / D Cu =1~15.

[0021] And / or, the contact interface between the electrode and the magnetic core presents a wavy, non-straight interface.

[0022] And / or, the average thickness of the element diffusion layer is 2~60μm.

[0023] In a second aspect, the present invention provides a method for preparing a co-fired inductor as described in the first aspect, comprising at least a low-temperature debinding heat treatment, a sintering heat treatment, and an alloy diffusion heat treatment performed sequentially.

[0024] This invention adds an alloy diffusion heat treatment process after the original low-temperature debinding heat treatment and sintering heat treatment. Through alloy diffusion heat treatment, an element interdiffusion layer is formed at the contact interface between the electrode and the magnetic core. There is no need to add additional processes such as plating or interlayering. The process is simple, the production cost is low, and it is conducive to industrialization.

[0025] And / or, the temperature of the alloy diffusion heat treatment is 800~900℃, and the holding time is 5~20min.

[0026] Thirdly, the present invention provides an application of the co-fired inductor as described in the first aspect, specifically for use in server power modules or vehicle DC-DC converters.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention utilizes element interdiffusion to form a metallurgical bond at the contact interface between the electrode and the magnetic core, thereby enhancing the bonding force between the two and effectively avoiding interface cracking and deformation caused by different expansion rates at the junction of the electrode and the magnetic core. This eliminates parasitic air gaps inside the device from the root, thereby significantly improving the overall electrical performance, mechanical performance and yield of the inductor.

[0029] (2) The present invention adds an alloy diffusion heat treatment process after the original low temperature debinding heat treatment and sintering heat treatment. Through alloy diffusion heat treatment, an element interdiffusion layer is formed at the contact interface between the electrode and the magnetic core. There is no need to add additional processes such as plating or interlayer. The process is simple, the production cost is low, and it is conducive to industrialization. Attached Figure Description

[0030] Figure 1 This is the temperature rise curve of the three-stage heat treatment in the copper co-fired inductor preparation method provided in Example 1;

[0031] Figure 2 This is a micrograph of the contact interface between the electrode and the magnetic core in the copper-magnetic co-fired inductor provided in Example 1;

[0032] Figure 3 This is the EDS point measurement analysis curve of the contact interface between the electrode and the magnetic core in the copper-co-fired inductor provided in Example 1;

[0033] Figure 4 The temperature rise curve of the two-stage heat treatment in the copper co-fired inductor preparation method provided in Comparative Example 1 is shown.

[0034] Figure 5 This is a micrograph of the contact interface between the electrode and the magnetic core in the copper-co-fired inductor provided in Comparative Example 1;

[0035] Figure 6 This is the temperature rise curve of the three-stage heat treatment in the copper magnet co-fired inductor preparation method provided in Example 2;

[0036] Figure 7 This is a micrograph of the contact interface between the electrode and the magnetic core in the copper-magnetic co-fired inductor provided in Example 2. Detailed Implementation

[0037] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0038] One embodiment of the present invention provides a co-fired inductor, including electrodes and a magnetic core, wherein an elemental interdiffusion layer exists at the contact interface between the electrodes and the magnetic core.

[0039] This invention utilizes element interdiffusion to form a metallurgical bond at the contact interface between the electrode and the magnetic core, enhancing the bonding force between the two and effectively avoiding interface cracking and deformation caused by different expansion rates at the junction of the electrode and the magnetic core. This eliminates parasitic air gaps inside the device from the root, thereby significantly improving the overall electrical performance, mechanical performance, and yield of the inductor.

[0040] In some embodiments, the electrode is made of Cu or a Cu alloy, and the Cu content in the Cu alloy is ≥98wt%, for example, it can be 98wt%, 98.2wt%, 98.4wt%, 98.6wt%, 98.8wt%, 99wt%, 99.2wt%, 99.4wt%, 99.6wt%, 99.8wt%, or 99.9wt%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0041] In some embodiments, the material of the magnetic core includes at least one of FeSiAl, FeSi, FeSiCr, or FeNi.

[0042] In some embodiments, Fe and / or Ni elements are diffused along the contact interface in a 4-59 μm region toward the electrode side.

[0043] In some embodiments, the concentration of Fe element in the 59 μm region along the contact interface toward the electrode side ranges from 0.2 to 4.0 wt%, for example, it can be 0.2 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, or 4.0 wt%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0044] In some embodiments, the concentration of Ni in the 59 μm region along the contact interface toward the electrode side ranges from 0.1 to 3.0 wt%, for example, it can be 0.1 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, or 3.0 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0045] In some embodiments, Cu element is diffused along the contact interface into a 2-15 μm region toward the core side.

[0046] In some embodiments, the concentration of Cu element in the 15 μm region along the contact interface toward the core side ranges from 0.2 to 4.0 wt%, for example, it can be 0.2 wt%, 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 2.5 wt%, 3.0 wt%, 3.5 wt%, or 4.0 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0047] In some embodiments, the concentration distribution of the Fe and / or Ni elements exhibits a gradient decreasing trend along the contact interface toward the electrode side.

[0048] In some embodiments, the concentration distribution of Cu element exhibits a gradient decreasing trend along the contact interface toward the magnetic core side.

[0049] In some embodiments, the diffusion depth of the Fe element along the contact interface toward the electrode side is set to D. Fe The diffusion depth of the Cu element along the contact interface toward the core side is D. Cu Then D is satisfied. Fe / D Cu =1~15, for example, it can be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15, but it is not limited to the listed values. Other unlisted values ​​within this range also apply.

[0050] In some embodiments, the contact interface between the electrode and the magnetic core presents a wavy, non-flat interface.

[0051] In some embodiments, the average thickness of the element diffusion layer is 2 to 60 μm, for example, it can be 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm or 60 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0052] One embodiment of the present invention also provides a method for preparing the co-fired inductor described in any of the above embodiments, which includes at least a low-temperature debinding heat treatment, a sintering heat treatment, and an alloy diffusion heat treatment performed sequentially.

[0053] This invention adds an alloy diffusion heat treatment process after the original low-temperature debinding heat treatment and sintering heat treatment. Through alloy diffusion heat treatment, an element interdiffusion layer is formed at the contact interface between the electrode and the magnetic core. There is no need to add additional processes such as plating or interlayering. The process is simple, the production cost is low, and it is conducive to industrialization.

[0054] In some embodiments, the temperature of the alloy diffusion heat treatment is 800~900℃, for example, it can be 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃ or 900℃, and the holding time is 5~20min, for example, it can be 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, 19min or 20min, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0055] It is important to note that the negative effects of element interdiffusion between electrodes and the magnetic core are generally significant. For example, in multilayer inductors, the diffusion of elements from the Ag electrode into the magnetic core often reduces insulation properties and deteriorates magnetic performance. Simultaneously, the diffusion of elements from the magnetic core into the Ag electrode increases impurities and resistivity, ultimately worsening the performance of the entire inductor. To address this, this invention employs a high-temperature (800~900℃), short-time (5~20min) alloy diffusion heat treatment process to effectively control the amount of element interdiffusion. This process achieves beneficial technical effects in copper co-fired inductors, effectively overcoming the aforementioned technical obstacles.

[0056] In addition, since the surface of magnetic core powder generally has an insulating coating, if the temperature of the alloy diffusion heat treatment is too high (such as exceeding 900°C) or the time is too long (such as exceeding 20 minutes), the insulating coating will decompose, which will lead to the deterioration of inductance performance.

[0057] One embodiment of the present invention also provides an application of the co-fired inductor described in any of the above embodiments, specifically for use in server power modules or vehicle DC-DC converters.

[0058] In some embodiments, the co-fired inductor, due to its small inductance and large current characteristics, is specifically used in GPU power management modules or AI servers, which helps to improve the efficiency of the power module.

[0059] In some embodiments, the co-fired inductor is used in a SIP power module. Alternatively, the co-fired inductor can be integrated into the power module package using a low-temperature co-fired ceramic (LTCC) process to achieve miniaturization, high reliability, and high power density.

[0060] In some embodiments, the co-fired inductor is used in the DC-DC converter of new energy vehicles to store energy, filter and transform voltage, improve energy conversion efficiency, reduce electromagnetic interference (EMI), and thus ensure the stable operation of the vehicle electrical system.

[0061] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0062] Example 1

[0063] This embodiment provides a copper co-fired inductor and its preparation method. The copper co-fired inductor includes Cu electrodes and FeSi magnetic cores. The preparation method includes a three-stage heat treatment, which consists of a low-temperature debinding heat treatment, a sintering heat treatment, and an alloy diffusion heat treatment performed sequentially.

[0064] like Figure 1 As shown, the temperature of the low-temperature debinding heat treatment is 250℃ and the holding time is 3h; the temperature of the sintering heat treatment is 750℃ and the holding time is 42min; the temperature of the alloy diffusion heat treatment is 880℃ and the holding time is 18min.

[0065] like Figure 2As shown, the contact interface between the electrode and the magnetic core in the sintered inductor exhibits an elemental interdiffusion layer with good bonding and no obvious cracks. EDS point analysis reveals that Cu and Fe elements interdiffused at the contact interface, with an interdiffusion layer thickness of approximately 24 μm. Specifically, Fe diffuses along the 22 μm region towards the electrode side of the contact interface, with a concentration ranging from 0.7 to 3.2 wt%; Cu diffuses along the 2 μm region towards the magnetic core side of the contact interface, with a concentration ranging from 0.6 to 0.7 wt%. Figure 2 The types and concentrations of elements at each sampling point are shown in Table 1 below.

[0066] Table 1

[0067]

[0068] Figure 3 Given the diffusion concentration gradients of different elements towards the core and electrode directions, respectively, the diffusion depth D of Fe along the contact interface towards the electrode side can be determined. Fe =22μm, the diffusion depth D of Cu element along the contact interface toward the core side Cu =2μm, therefore satisfying D Fe / D Cu =11.

[0069] Testing showed that the inductance and device conversion efficiency of the sample obtained in this embodiment were excellent (see Table 3), with a saturation current and temperature rise current of 42A and a yield rate as high as 92%.

[0070] Comparative Example 1

[0071] This comparative example provides a copper co-fired inductor and its preparation method. The only difference between this example and Example 1 is that a two-stage heat treatment is used, consisting of a low-temperature debinding heat treatment and a sintering heat treatment performed sequentially, i.e., no alloy diffusion heat treatment is performed.

[0072] like Figure 4 As shown, the temperature of the low-temperature debinding heat treatment is 250℃ and the holding time is 3h; the temperature of the sintering heat treatment is 750℃ and the holding time is 1.3h.

[0073] like Figure 5 As shown, the contact interface between the electrode and the magnetic core in the inductor obtained after sintering is mismatched and has obvious cracks, that is, the bonding between the electrode and the magnetic core is poor, and no obvious element interdiffusion phenomenon is observed at the interface. Figure 5 The types and concentrations of elements at each sampling point are shown in Table 2 below.

[0074] Table 2

[0075]

[0076] Testing revealed that the inductance and device conversion efficiency of the samples obtained in this comparative example were both low (see Table 3), with saturation current and temperature rise current both at 35A, resulting in a yield rate of 86%.

[0077] Comparative Example 2

[0078] This comparative example provides a copper co-fired inductor and its preparation method. The only difference between this example and Example 1 is that the holding time of the alloy diffusion heat treatment is extended to 36 minutes.

[0079] The results showed that in this comparative example, the electrode-core interface did not crack during sintering, and there was obvious interdiffusion of elements at the interface. However, the inductance of the obtained sample was higher, the device conversion efficiency was lower (see Table 3), the saturation current was 28A and the temperature rise current was 24A, both of which were significantly lower than those in Example 1. This is because the heat treatment time at high temperature was longer, and the structure of the powder insulating coating layer was slightly damaged.

[0080] Comparative Example 3

[0081] This comparative example provides a copper co-fired inductor and its preparation method. The only difference between this example and Example 1 is that the temperature of the alloy diffusion heat treatment is increased to 920°C and the holding time is extended to 36 min.

[0082] The results showed that in this comparative example, the electrode-core interface did not crack during sintering, and there was obvious interdiffusion of elements at the interface. However, the inductance of the obtained sample was higher, and the device conversion efficiency was lower (see Table 3). The saturation current was 26A and the temperature rise current was 23A, both of which were significantly lower than those in Example 1. This was because the heat treatment temperature was high and the time was long at high temperatures, causing the powder insulation coating to fail.

[0083] Example 2

[0084] This embodiment provides a copper co-fired inductor and its preparation method. The copper co-fired inductor includes Cu electrodes and FeNi magnetic cores. The preparation method includes a three-stage heat treatment, which consists of a low-temperature debinding heat treatment, a sintering heat treatment, and an alloy diffusion heat treatment performed sequentially.

[0085] like Figure 6 As shown, the temperature of the low-temperature debinding heat treatment is 250℃ and the holding time is 3h; the temperature of the sintering heat treatment is 720℃ and the holding time is 42min; the temperature of the alloy diffusion heat treatment is 840℃ and the holding time is 18min.

[0086] like Figure 7As shown, the contact interface between the electrode and the magnetic core in the sintered inductor exhibits an elemental interdiffusion layer with good bonding and no obvious cracks. EDS point analysis reveals that Cu, Fe, and Ni elements interdiffused at the contact interface, with an interdiffusion layer thickness of approximately 25 μm. Specifically, Fe and Ni elements diffuse along the 16 μm region towards the electrode side from the contact interface, with Fe concentrations ranging from 0.3 to 3 wt% and Ni concentrations ranging from 0.3 to 2 wt%. Cu elements diffuse along the 9 μm region towards the magnetic core side from the contact interface, with concentrations ranging from 0.5 to 4.5 wt%. The diffusion depth D of Fe elements along the contact interface towards the electrode side... Fe =16μm, the diffusion depth D of Cu element along the contact interface toward the core side Cu =9μm, therefore satisfying D Fe / D Cu =1.8.

[0087] Testing showed that the inductance and device conversion efficiency of the sample obtained in this embodiment were excellent (see Table 3), with a saturation current of 52A, a temperature rise current of 39A, and a yield rate as high as 95%.

[0088] Comparative Example 4

[0089] This comparative example provides a copper co-fired inductor and its preparation method. The only difference between this example and Example 2 is that a two-stage heat treatment is used, consisting of a low-temperature debinding heat treatment and a sintering heat treatment performed sequentially, i.e., no alloy diffusion heat treatment is performed.

[0090] Specifically, the low-temperature debinding heat treatment is performed at a temperature of 250°C for 3 hours; the sintering heat treatment is performed at a temperature of 720°C for 1.3 hours.

[0091] The results showed that the comparative example cracked during sintering due to mismatch at the contact interface between the electrode and the magnetic core, and no obvious interdiffusion of elements was observed at the interface.

[0092] Testing revealed that the inductance and device conversion efficiency of the sample obtained in this comparative example were both low (see Table 3), with a saturation current of 46A and a temperature rise current of 32A, both of which were significantly lower than those in Example 2, resulting in a yield rate of 88%.

[0093] Example 3

[0094] This embodiment provides a copper co-fired inductor and its preparation method. The copper co-fired inductor includes Cu electrodes and FeSiAl magnetic cores. The preparation method includes a three-stage heat treatment, which consists of a low-temperature debinding heat treatment, a sintering heat treatment, and an alloy diffusion heat treatment performed sequentially.

[0095] Specifically, the low-temperature debinding heat treatment is performed at a temperature of 250°C for 3 hours; the sintering heat treatment is performed at a temperature of 750°C for 42 minutes; and the alloy diffusion heat treatment is performed at a temperature of 850°C for 18 minutes.

[0096] In this embodiment, the contact interface between the electrode and the magnetic core in the sintered inductor exhibits an element interdiffusion layer, and the interface shows good bonding without obvious cracks. EDS point measurement analysis reveals that Cu and Fe elements interdiffusion occur at the contact interface, with an interdiffusion layer thickness of approximately 32 μm. Specifically, Fe diffuses along the contact interface towards the electrode side within a 25 μm region, with a concentration ranging from 0.5 to 2.8 wt%; Cu diffuses along the contact interface towards the magnetic core side within a 7 μm region, with a concentration ranging from 0.3 to 1.7 wt%. The diffusion depth D of Fe along the contact interface towards the electrode side... Fe =25μm, the diffusion depth D of Cu element along the contact interface toward the core side Cu =7μm, therefore satisfying D Fe / D Cu =3.6.

[0097] Testing showed that the inductance and device conversion efficiency of the sample obtained in this embodiment were excellent (see Table 3), with a saturation current of 42A, a temperature rise current of 32A, and a yield rate as high as 93%.

[0098] Comparative Example 5

[0099] This comparative example provides a copper co-fired inductor and its preparation method. The only difference between this example and Example 3 is that it uses a two-stage heat treatment, which consists of a low-temperature debinding heat treatment and a sintering heat treatment performed sequentially. That is, no alloy diffusion heat treatment is performed.

[0100] Specifically, the low-temperature debinding heat treatment is performed at a temperature of 250°C for 3 hours; the sintering heat treatment is performed at a temperature of 750°C for 1.3 hours.

[0101] The results showed that the comparative example cracked during sintering due to mismatch at the contact interface between the electrode and the magnetic core, and no obvious interdiffusion of elements was observed at the interface.

[0102] Testing revealed that the inductance and device conversion efficiency of the sample obtained in this comparative example were both low (see Table 3), with a saturation current of 31A and a temperature rise current of 22A, both of which were significantly lower than those in Example 3, resulting in a yield rate of 86%.

[0103] Performance testing

[0104] (1) Inductance value: The test was conducted in accordance with GB / T 40853.1-2021 "Electrical characteristics and measurement methods of high frequency inductive components - Part 1: Nahen chip inductors".

[0105] (2) Saturation current and temperature rise current: The test was conducted in accordance with GB / T 40853.2-2023 "Electrical characteristics of high frequency inductive elements and their measurement methods - Part 2: Rated current of inductors for DC-DC converters".

[0106] (3) Device conversion efficiency: The actual power loss of the inductor under real working conditions is measured by a power analyzer, and the device conversion efficiency is calculated accordingly.

[0107] The relevant test results are shown in Table 3 below.

[0108] Table 3

[0109]

[0110] As shown in Table 3:

[0111] (1) Compared with Example 1, since Comparative Example 1 only used two-stage heat treatment and did not perform alloy diffusion heat treatment, the inductance value and device conversion efficiency of the obtained sample were significantly reduced, and the saturation current and temperature rise current were not as good as those of Example 1.

[0112] (2) Compared with Example 1, Comparative Example 2 has excessively extended the holding time of alloy diffusion heat treatment, resulting in a higher inductance value, lower device conversion efficiency, and lower saturation current and temperature rise current than Example 1.

[0113] (3) Compared with Example 1, Comparative Example 3 increased the temperature of the alloy diffusion heat treatment and extended the holding time excessively, resulting in a higher inductance value and lower device conversion efficiency of the obtained sample. The saturation current and temperature rise current were also lower than those of Example 1.

[0114] (4) Compared with Example 2, Comparative Example 4 only used two-stage heat treatment and did not perform alloy diffusion heat treatment, resulting in a significant reduction in the inductance value and device conversion efficiency of the obtained sample. The saturation current and temperature rise current were both lower than those of Example 2.

[0115] (5) Compared with Example 3, Comparative Example 5 only used two-stage heat treatment and did not perform alloy diffusion heat treatment, resulting in a significant reduction in the inductance value and device conversion efficiency of the obtained sample. The saturation current and temperature rise current were both lower than those of Example 3.

[0116] As can be seen, the present invention utilizes element interdiffusion to form a metallurgical bond at the contact interface between the electrode and the magnetic core, thereby enhancing the bonding force between the two and effectively avoiding interface cracking and deformation caused by different expansion rates at the junction of the electrode and the magnetic core. This eliminates parasitic air gaps inside the device from the root, and thus significantly improves the overall electrical performance, mechanical performance and yield of the inductor.

[0117] In addition, this invention adds an alloy diffusion heat treatment process after the original low-temperature debinding heat treatment and sintering heat treatment. Through alloy diffusion heat treatment, an element interdiffusion layer is formed at the contact interface between the electrode and the magnetic core. There is no need to add additional processes such as plating or interlayering. The process is simple, the production cost is low, and it is conducive to industrialization.

[0118] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A co-fired inductor, comprising electrodes and a magnetic core, characterized in that, An elemental interdiffusion layer exists at the contact interface between the electrode and the magnetic core.

2. The co-fired inductor according to claim 1, characterized in that, The electrode is made of Cu or a Cu alloy, and the Cu content in the Cu alloy is ≥98 wt%. And / or, the material of the magnetic core includes at least one of FeSiAl, FeSi, FeSiCr or FeNi.

3. The co-fired inductor according to claim 2, characterized in that, Fe and / or Ni elements diffuse along the contact interface in a 4-59 μm region toward the electrode side; The concentration of Fe element in the 59 μm region along the contact interface towards the electrode side ranges from 0.2 to 4.0 wt%. And / or, the concentration of Ni element in the 59 μm region along the contact interface toward the electrode side ranges from 0.1 to 3.0 wt%.

4. The co-fired inductor according to claim 2, characterized in that, Cu element diffuses along the contact interface into a 2-15 μm region toward the magnetic core side; The concentration of Cu element in the 15μm region along the contact interface toward the magnetic core side ranges from 0.2 to 4.0 wt%.

5. The co-fired inductor according to claim 3 or 4, characterized in that, The concentration distribution of Fe and / or Ni elements shows a gradient decreasing trend along the contact interface toward the electrode side; And / or, the concentration distribution of the Cu element shows a gradient decreasing trend along the contact interface toward the magnetic core side.

6. The co-fired inductor according to claim 3 or 4, characterized in that, Let the diffusion depth of the Fe element along the contact interface toward the electrode side be D. Fe The diffusion depth of the Cu element along the contact interface toward the core side is D. Cu Then D is satisfied. Fe / D Cu =1~15.

7. The co-fired inductor according to claim 1, characterized in that, The contact interface between the electrode and the magnetic core is a wavy, non-straight interface. And / or, the average thickness of the element diffusion layer is 2~60μm.

8. A method for preparing a co-fired inductor as described in any one of claims 1 to 7, characterized in that, The preparation method includes at least the following sequential processes: low-temperature debinding heat treatment, sintering heat treatment, and alloy diffusion heat treatment.

9. The preparation method according to claim 8, characterized in that, The alloy diffusion heat treatment temperature is 800~900℃, and the holding time is 5~20min.

10. An application of the co-fired inductor as described in any one of claims 1 to 7, characterized in that, The co-fired inductor is used in server power modules or vehicle-mounted DC-DC converters.

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