INTEGRATED CO-FIRED INDUCTOR AND PREPARATION METHOD THEREFOR

Abstract

An integrated co-fired inductor and preparation method therefor, comprising: filling a mold cavity with a magnetic powder, embedding at least one wire in the magnetic powder, wherein the two ends extend out of the mold cavity, sequentially performing compression molding and heat treatment to obtain a magnetic core, and bending and tinning the wire extending out of the magnetic core to obtain the co-fired inductor. The preparation method uses an integrated mold forming process to prepare the inductor to avoid an assembly process involving an excessive number of components; heat treatment is performed after the integral forming process, stress is fully released, material hysteresis loss is reduced, and the loss of the device under light load conditions is reduced; no extra gap exists between the wire and the magnetic core, air gaps are uniformly distributed within the magnetic core, and the vibration noise of eddy current loss is reduced.

Claims

1. A preparation method for an integrated co-fired inductor, comprising: filling a mold cavity with a magnetic powder, embedding at least one wire into the magnetic powder, wherein two ends of the wire extend out of the mold cavity, then performing compression molding and heat treatment in sequence to obtain a magnetic core, and bending and tin-attaching the wire extending out of the magnetic core to obtain the co-fired inductor.

2. The preparation method according to claim 1, wherein the wire is a bare wire without paint layer.

3. The preparation method according to claim 1, wherein the wire is a copper wire.

4. The preparation method according to claim 1, wherein the wire is a flat wire having a rectangular cross section; preferably, the wire is a straight wire or a special-shaped wire; preferably, a shape of the special-shaped wire comprises an S-shape, an L-shape, a U-shape, a W-shape or an E-shape; preferably, the wires are laid inside the magnetic powder side by side at intervals on a horizontal plane.

5. The preparation method according to claim 1, wherein the compression molding is performed in a manner of hot pressing or non-hot pressing; preferably, the hot pressing is performed at more than or equal to 800 MPa/cm.sup.2, further preferably 2000 MPa/cm.sup.2; preferably, the hot pressing is performed at 90-180 C.; preferably, the hot pressing is performed for 5-100 s; preferably, the heat treatment is an annealing treatment; preferably, the heat treatment is performed under a protective atmosphere; preferably, the protective atmosphere uses nitrogen and/or an inert gas; preferably, the heat treatment is performed at 650-850 C.; preferably, the heat treatment is performed for 30-50 min.

6. The preparation method according to claim 1, wherein the preparation method further comprises: impregnating and spray-coating the magnetic core in sequence before the bending and tin-attaching; preferably, the impregnating is vacuum impregnation; preferably, a spray-coating liquid used for the spray-coating comprises an epoxy resin, a paint or Parylene.

7. The preparation method according to claim 1, wherein the magnetic powder is prepared by the following method: subjecting a soft magnetic powder to insulation coating, secondary coating and pelletizing treatment in sequence to obtain the magnetic powder; preferably, the soft magnetic powder is obtained by combining powders with two different particle sizes, wherein the powder with a larger particle size has a D50 of 6-50 m, and the powder with a smaller particle size has a D50 of 1-6 m; preferably, the powder comprises FeSiCr, FeSi, FeNi, FeSiAl, a carbonyl iron powder, a carbonyl iron nickel powder, FeNiMo, a Fe-based amorphous nanocrystalline material, a Co-based amorphous nanocrystalline soft magnetic material or a Ni-based amorphous nanocrystalline soft magnetic material.

8. The preparation method according to claim 7, wherein a coating process used for the insulation coating comprises phosphating, acidification, oxidation or nitridation, and further preferably, the soft magnetic powder is subjected to insulation coating by phosphating; preferably, the phosphating comprises: mixing and stirring the soft magnetic powder and a diluted phosphoric acid, and performing drying to obtain a phosphated soft magnetic powder; preferably, that phosphoric acid is dilute with acetone; preferably, the phosphoric acid and acetone have a mass ratio of 1:(60-70); preferably, the phosphoric acid and acetone are mixed and stirred for 1-6 min, and then stand for 5-10 min for later use; preferably, the soft magnetic powder and the diluted phosphoric acid are mixed and stirred for 30-60 min; preferably, the drying is performed at 90-110 C.; preferably, the drying is performed for 1-1.5 h.

9. The preparation method according to claim 7, wherein the secondary coating comprises: mixing and stirring a coating material and the soft magnetic powder after the insulation coating; preferably, the coating material is 2-10 wt % of the soft magnetic powder; preferably, the coating material comprises a phenolic resin, an epoxy resin or a silicon resin; preferably, the coating material and the soft magnetic powder are mixed and stirred for 40-60 min.

10. The preparation method according to claim 7, wherein the pelletizing treatment comprises: pelletizing the soft magnetic powder after the secondary coating, and airing, drying and cooling the soft magnetic powder in sequence after the pelletizing to obtain the magnetic powder; preferably, the pelletizing is performed in a 40-60 mesh pelletizer; preferably, the airing is performed for less than or equal to 3 h; preferably, the soft magnetic powder after the airing is sieved by a 30-50 mesh screen, and then dried; preferably, the drying is performed at 50-70 C.; preferably, the drying is performed for 0.8-1.2 h; preferably, the cooling is natural cooling; preferably, the soft magnetic powder after the cooling is sieved by a 30-50 mesh screen, and then added with an auxiliary material to obtain the magnetic powder; preferably, the auxiliary material comprises magnesium oxide, a lubricant powder or a demoulding powder.

11. A co-fired inductor prepared by the preparation method according to claim 1, comprising a magnetic core and at least one wire inside the magnetic core, wherein two ends of the wire extend out of the magnetic core, and a portion of the wire extending out of the magnetic core is bent and tightly touches an outer wall of the magnetic core.

12. The co-fired inductor according to claim 11, wherein the wire is a bare wire without paint layer; preferably, the wire is a copper wire; preferably, the wire is a flat wire having a rectangular cross section; preferably, the wire is a straight wire or a special-shaped wire; preferably, a shape of the special-shaped wire comprises an S-shape, an L-shape, a U-shape, a W-shape or an E-shape; preferably, the wires are laid inside the magnetic powder side by side at intervals on a horizontal plane.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0086] FIG. 1 is a structural diagram of a co-fired inductor provided by an embodiment of the present application.

REFERENCE LIST

[0087] 1magnetic core; and 2wire.

DETAILED DESCRIPTION

[0088] The technical solutions of the present application are further described below with reference to the drawing and embodiments.

Example 1

[0089] This example provides a preparation method for an integrated co-fired inductor, which includes the following steps: [0090] (1) a mold cavity was filled with a magnetic powder, and a flat copper wire having a rectangular cross section was embedded into the magnetic powder after removing paint layer, in which two ends of the wire 2 extended out of the mold cavity, and the wire 2 was a straight wire 2 which had a length of 14 mm, a width of 2.2 mm, and a thickness of 0.35 mm; [0091] (2) the magnetic powder with the wire 2 embedded was subjected to compression molding in a manner of hot pressing, in which the hot pressing was performed at 500 MPa/cm.sup.2 and 180 C. for 20 s; [0092] (3) after the molding, an annealing heat treatment was performed under a protective atmosphere to obtain a magnetic core 1, in which the heat treatment was performed at 700 C. for 30 min; and [0093] (4) the wire 2 extending out of the magnetic core 1 was impregnated, spray-coated, bent and tin-attached in sequence to obtain a co-fired inductor with a size of 10.0 mm5.0 mm2.0 mm (as shown in FIG. 1), in which the impregnating treatment was vacuum impregnation, and a spray-coating liquid used for the spray-coating was an epoxy resin.

[0094] In the method, the magnetic powder in step (1) was prepared by the following method: [0095] (a) powder combination: a FeSi powder with a D50 of 20.2 m and a carbonyl iron powder with a D50 of 3 m were mixed according to a mass ratio of 7:3 to obtain a combined soft magnetic powder; [0096] (b) insulation coating: phosphoric acid was diluted with acetone at a mass ratio of phosphoric acid to acetone being 1:60, and the phosphoric acid and acetone were mixed and stirred for 1 min and then stood for 5 min for later use; the combined soft magnetic powder obtained in step (a) was mixed with the diluted phosphoric acid and stirred for 30 min, and dried at 90 C. for 1 h to obtain a phosphated soft magnetic powder; [0097] (c) secondary coating: a coating material was mixed with the soft magnetic powder obtained in step (b) and stirred for 40 min, in which the coating material was 2 wt % of the soft magnetic powder, and the coating material was a phenolic resin; and [0098] (d) pelletizing treatment: the soft magnetic powder after the secondary coating was pelletized in a 40-mesh pelletizer, the soft magnetic powder after the pelletizing was aired for 2 h, and the soft magnetic powder after the airing was sieved by a 30 mesh screen, then dried at 50 C. for 0.8 h, cooled naturally, then sieved by a 30 mesh screen, and then added with an auxiliary material to obtain the magnetic powder, in which the auxiliary material was magnesium oxide.

[0099] The prepared co-fired inductor was tested for the inductance characteristics; the initial inductance L(0A) is 120 nH, the saturation current is 70 A, and the temperature rise-current is 65 A. The efficiency test was performed using a 12 V-1 V buck circuit at a switching frequency of 500 kHz; the efficiency reaches 79.5% when the electronic load is 5 A, and the efficiency reaches 88.3% when the electronic load is 15 A.

Example 2

[0100] This example provides a preparation method for an integrated co-fired inductor, which includes the following steps: [0101] (1) a mold cavity was filled with a magnetic powder, and a flat copper wire having a rectangular cross section was embedded into the magnetic powder after removing paint layer, in which two ends of the wire 2 extended out of the mold cavity, and the wire 2 had an S-shape which had a length of 10 mm, a width of 2.6 mm, and a thickness of 0.30 mm; [0102] (2) the magnetic powder with the wire 2 embedded was subjected to compression molding in a manner of hot pressing, in which the hot pressing was performed at 400 MPa/cm.sup.2 and 175 C. for 25 s; [0103] (3) after the molding, an annealing heat treatment was performed under a protective atmosphere to obtain a magnetic core 1, in which the heat treatment was performed at 650 C. for 50 min; and [0104] (4) the wire 2 extending out of the magnetic core 1 was impregnated, spray-coated, bent and tin-attached in sequence to obtain a co-fired inductor with a size of 8.0 mm6.0 mm1.9 mm (as shown in FIG. 1), in which the impregnating treatment was vacuum impregnation, and a spray-coating liquid used for the spray-coating was an epoxy resin.

[0105] In the method, the magnetic powder in step (1) was prepared by the following method: [0106] (a) powder combination: a FeSiAl powder with a D50 of 18.3 m and a FeNi powder with a D50 of 2.8 m were mixed according to a mass ratio of 75:25 to obtain a combined soft magnetic powder; [0107] (b) insulation coating: phosphoric acid was diluted with acetone at a mass ratio of phosphoric acid to acetone being 1:63, and the phosphoric acid and acetone were mixed and stirred for 3 min and then stood for 6 min for later use; the combined soft magnetic powder obtained in step (a) was mixed with the diluted phosphoric acid and stirred for 40 min, and dried at 95 C. for 1.2 h to obtain a phosphated soft magnetic powder; [0108] (c) secondary coating: a coating material was mixed with the soft magnetic powder obtained in step (b) and stirred for 45 min, in which the coating material was 5 wt % of the soft magnetic powder, and the coating material was an epoxy resin; and [0109] (d) pelletizing treatment: the soft magnetic powder after the secondary coating was pelletized in a 43-mesh pelletizer, the soft magnetic powder after the pelletizing was aired for 2.3 h, and the soft magnetic powder after the airing was sieved by a 35 mesh screen, then dried at 55 C. for 1 h, cooled naturally, then sieved by a 35 mesh screen, and then added with an auxiliary material to obtain the magnetic powder, in which the auxiliary material was a lubricant powder.

[0110] The prepared co-fired inductor was tested for the inductance characteristics; the initial inductance L(0A) is 100 nH, the saturation current is 50 A, and the temperature rise-current is 50 A. The efficiency test was performed using a 6 V-0.8 V buck circuit at a switching frequency of 1000 kHz; the efficiency reaches 81.5% when the electronic load is 5 A, and the efficiency reaches 90.3% when the electronic load is 25 A.

Example 3

[0111] This example provides a preparation method for an integrated co-fired inductor, which includes the following steps: [0112] (1) a mold cavity was filled with a magnetic powder, and a flat copper wire having a rectangular cross section was embedded into the magnetic powder after removing paint layer, in which two ends of the wire 2 extended out of the mold cavity, and the wire 2 had a W-shape which had a length of 18 mm, a width of 2.8 mm, and a thickness of 0.26 mm; [0113] (2) the magnetic powder with the wire 2 embedded was subjected to compression molding in a manner of cold pressing, in which the cold pressing was performed at 1600 MPa/cm.sup.2; [0114] (3) after the molding, an annealing heat treatment was performed under a protective atmosphere to obtain a magnetic core 1, in which the heat treatment was performed at 690 C. for 40 min; and [0115] (4) the wire 2 extending out of the magnetic core 1 was impregnated, spray-coated, bent and tin-attached in sequence to obtain a co-fired inductor with a size of 7.5 mm6.5 mm1.8 mm (as shown in FIG. 1), in which the impregnating treatment was vacuum impregnation, and a spray-coating liquid used for the spray-coating was an epoxy resin.

[0116] In the method, the magnetic powder in step (1) was prepared by the following method: [0117] (a) powder combination: a FeNi powder with a D50 of 17.5 m and a FeSi powder with a D50 of 2.6 m were mixed according to a mass ratio of 80:20 to obtain a combined soft magnetic powder; [0118] (b) insulation coating: phosphoric acid was diluted with acetone at a mass ratio of phosphoric acid to acetone being 1:65, and the phosphoric acid and acetone were mixed and stirred for 5 min and then stood for 8 min for later use; the combined soft magnetic powder obtained in step (a) was mixed with the diluted phosphoric acid and stirred for 50 min, and dried at 100 C. for 1.3 h to obtain a phosphated soft magnetic powder; [0119] (c) secondary coating: a coating material was mixed with the soft magnetic powder obtained in step (b) and stirred for 55 min, in which the coating material was 7 wt % of the soft magnetic powder, and the coating material was a silicon resin; and [0120] (d) pelletizing treatment: the soft magnetic powder after the secondary coating was pelletized in a 50-mesh pelletizer, the soft magnetic powder after the pelletizing was aired for 2.5 h, and the soft magnetic powder after the airing was sieved by a 40 mesh screen, then dried at 63 C. for 1.1 h, cooled naturally, then sieved by a 40 mesh screen, and then added with an auxiliary material to obtain the magnetic powder, in which the auxiliary material was a demoulding powder.

[0121] The prepared co-fired inductor was tested for the inductance characteristics; the initial inductance L(0A) is 150 nH, the saturation current is 80 A, and the temperature rise-current is A. The efficiency test was performed using a 5 V-1 V buck circuit at a switching frequency of 750 kHz; the efficiency reaches 78.2% when the electronic load is 5 A, and the efficiency reaches 92.5% when the electronic load is 45 A.

Example 4

[0122] This example provides a preparation method for an integrated co-fired inductor, which includes the following steps: [0123] (1) a mold cavity was filled with a magnetic powder, and a flat copper wire having a rectangular cross section was embedded into the magnetic powder after removing paint layer, in which two ends of the wire 2 extended out of the mold cavity, and the wire 2 was a straight wire 2 which had a length of 10 mm, a width of 2.0 mm, and a thickness of 0.36 mm; [0124] (2) the magnetic powder with the wire 2 embedded was subjected to compression molding in a manner of cold pressing, in which the cold pressing was performed at 1500 MPa/cm.sup.2; [0125] (3) after the molding, an annealing heat treatment was performed under a protective atmosphere to obtain a magnetic core 1, in which the heat treatment was performed at 850 C. for 30 min; and [0126] (4) the wire 2 extending out of the magnetic core 1 was impregnated, spray-coated, bent and tin-attached in sequence to obtain a co-fired inductor with a size of 8.0 mm5.0 mm3.0 mm (as shown in FIG. 1), in which the impregnating treatment was vacuum impregnation, and a spray-coating liquid used for the spray-coating was an epoxy resin.

[0127] In the method, the magnetic powder in step (1) was prepared by the following method: [0128] (a) powder combination: a FeSiB amorphous powder with a D50 of 23 m and a carbonyl iron nickel powder with a D50 of 2 m were mixed according to a mass ratio of 80:20 to obtain a combined soft magnetic powder; [0129] (b) insulation coating: phosphoric acid was diluted with acetone at a mass ratio of phosphoric acid to acetone being 1:70, and the phosphoric acid and acetone were mixed and stirred for 6 min and then stood for 10 min for later use; the combined soft magnetic powder obtained in step (a) was mixed with the diluted phosphoric acid and stirred for 60 min, and dried at 110 C. for 1.5 h to obtain a phosphated soft magnetic powder; [0130] (c) secondary coating: a coating material was mixed with the soft magnetic powder obtained in step (b) and stirred for 60 min, in which the coating material was 10 wt % of the soft magnetic powder, and the coating material was a silicon resin; and [0131] (d) pelletizing treatment: the soft magnetic powder after the secondary coating was pelletized in a 60-mesh pelletizer, the soft magnetic powder after the pelletizing was aired for 3 h, and the soft magnetic powder after the airing was sieved by a 50 mesh screen, then dried at 70 C. for 1.2 h, cooled naturally, then sieved by a 50 mesh screen, and then added with an auxiliary material to obtain the magnetic powder, in which the auxiliary material was magnesium oxide.

[0132] The prepared co-fired inductor was tested for the inductance characteristics; the initial inductance L(0A) is 60 nH, the saturation current is 15 A, and the temperature rise-current is 12 A. The efficiency test was performed using a 5 V-1 V buck circuit at a switching frequency of 1500 kHz; the efficiency reaches 89.5% when the electronic load is 0.5 A, and the efficiency reaches 90.5% when the electronic load is 5 A.