CN1069823A - Production of amorphous magnetic core for magnetic-compensation Hall current sensor - Google Patents

Abstract

The invention is used for the cutting magnetic core of the magnetic compensation Hall current sensor. The composition of the present invention is FczNiyMxSi7-10B12-15 (wherein M is Mo or Mn, x is 0-5, y is 0-40, z is 36-78), through special partial crystallization annealing or transverse magnetic field annealing, make Remanence reduces and improves high-frequency characteristics, and finally uses semi-flexible epoxy resin for encapsulation, curing and cutting. Compared with the traditional Permal magnetic core, the important advantages of the amorphous magnetic core of the present invention are low raw material and manufacturing costs, easy manufacturing, excellent frequency characteristics and lower remanence and coercive force, which can improve the response time of the sensor and precision.

Description

The invention belongs to a new type of soft magnetic core, which replaces the traditional high permeability 80Ni-Fe system permalloy material core, and has extremely low remanence induction intensity, low coercive force and better frequency characteristics. Magnetic cores are specially adapted for magnetic cores in magnetically compensated Hall current sensors.

The magnetically compensated Hall current sensor is a high-precision, non-contact, new sensor that can measure and control various waveform currents. It is widely used in emerging power electronics technology, and the magnetic core is one of its two key components. The magnetic core is usually required to have the following characteristics: 1) low remanence Br; 2) low coercive force Hc; 3) good frequency characteristics; 4) high saturation magnetic induction Bs; 5) good manufacturing process performance.

The prior art uses a permalloy tape-wound magnetic core provided by West Germany with a magnetic core containing 80% Ni, and the tape thickness is about 0.1mm. After annealing-varnish curing, its magnetic level is: Bs 0.8T, Br 0.24T, Hc 2.1A/m (0.026Oe), due to the thick tape, the high-frequency magnetism is poor, which limits the improvement of sensor response time , its remanence Br and Hc are larger, reducing the accuracy of the sensor. In recent years, with the development of power electronics technology, the requirements for measurement and control of high-frequency, non-sinusoidal current have gradually increased. Therefore, there is a need for a cut magnetic core with better frequency characteristics, lower remanence and coercive force to meet the requirements of new sensors.

The sensors sold in the domestic and foreign markets are all produced by the Swiss LAM company, all of which are provided by West Germany with Permal magnetic cores. So far, no patents and reports on the use of amorphous alloy magnetic cores have been found. For literature reports on traditional sensors, see literature [1].

The purpose of the invention is to replace the traditional Permalloy magnetic core with an amorphous magnetic core to improve the accuracy and high frequency characteristics of the sensor. In addition, through the adjustment of the amorphous composition and the improvement of the process, the amorphous magnetic core of the sensor is easy to process and manufacture, the stability of the industrial production process is improved, the cost is reduced, and it is suitable for mass production.

The content of the invention includes:

The composition of the amorphous alloy is FezNiyMxSi7-10B12~15 (where M is Mo or Mn, x is 0~5, y is 0~40, z is 36-78), this amorphous alloy has good high frequency soft magnetic properties It can be as good as the tape-making process performance. Under normal annealing conditions, it can reach Hc<1.6A/m Bs can reach 0.9T, and the saturation hysteresis coefficient is 10×10 ^-6 . The resistivity is 1.35 μΩ·m.

The invention uses a vacuum induction furnace to smelt and cast a rod-shaped base material, and uses a single-roll method to make an amorphous strip with a required width, and then winds it into a ring-shaped or racetrack-shaped magnetic core.

The magnetic core of the above composition can be annealed according to the following two processes:

a) Partial crystallization annealing In nitrogen or argon protective gas, the annealing temperature is 410-450°C, heat preservation for 10-30 minutes, air cooling, high Bs and low Br and good high frequency characteristics can be obtained.

b) Transverse magnetic annealing The annealing temperature is 400-430°C, the holding time is 10-30 minutes, and the furnace is cooled. The magnetic field strength is greater than 1600A/m. The purpose of transverse magnetic annealing is to reduce Br and improve frequency characteristics.

The annealed magnetic core can be cured by encapsulation or encapsulation. Infusion is performed using a low stress semi-flexible epoxy resin formulated with:

Variety Mixing ratio (weight)

Epoxy resin 100

Curing agent (anhydrides, etc.) 8～16

Edge enhancer (poly S rubber, etc.) 5～30

Extender (Si micropowder, etc.) 30～50

The curing and drying process is 150°C, 3 hours

Cut the cured magnetic core into the required size of the air gap with a grinding wheel slicer or a wire cutting machine, so as to put it into the Hall semiconductor device. The above process can ensure that there will be no defects such as resin cracking, interlayer delamination and air gap deformation during the cutting process.

Compared with the existing technology and its advantages:

Compared with the existing technology and its advantages:

Existing Permalloy magnetic core and the magnetic core of the present invention have the following differences in magnetism and technology:

(1) The current magnetic core adopts permalloy containing Ni80%, and the present invention adopts Fe-Ni based amorphous magnetic core.

(2) The present invention adopts low-temperature annealing (400-450°C), does not require coating, has a short treatment period, does not require strict protection gas, and has a simple process. However, the current Permal magnetic core must adopt conventional insulating electrophoretic coating and high temperature constant time annealing (1050 ° C × 4hr), and the annealing process is very complicated.

(3) The present invention adopts epoxy resin encapsulation and curing method, while the currently used Permal magnetic core adopts the method of dipping paint. The former method can ensure that the soft magnetic properties will not change much after curing, while the latter will greatly reduce the magnetic properties. For example, for the coercive force Hc, the magnetic core of the present invention increases by 0-30% after curing, while the current technology generally increases to 400%.

(4) The DC magnetism of the core before and after cutting can be compared as follows:

Table 1 compares the DC performance of the core after curing and before cutting. Figure 1 is the comparison of the magnetic core hysteresis loop after cutting. (a) in Fig. 1 is the magnetic core of the present invention; (b) is the current Permal magnetic core. It can be seen that the magnetic core of the present invention has the advantages of high Bs, low Br and Hc, and the linearity of the curve is high, which is more suitable for the Hall current sensor.

(5) Regarding high frequency characteristics:

In the state before cutting after curing, the magnetic core of the present invention and the existing Permal magnetic core have been compared in frequency characteristics, and the elastic permeability of the two magnetic cores has been measured using the bridge method under the magnetic induction condition of Bm=5mT As the operating frequency changes, the dispersion characteristics of its magnetic permeability are shown in Table 2. It can be seen from the table that the traditional Permal core has dropped significantly since the frequency of 10KHz. At 50KHz, the magnetic permeability is already lower than 1000, but the magnetic permeability of the magnetic core of the present invention is only reduced by 18% from 10KHz to 150KHz. This magnetic core is especially suitable for the measurement and control of high-frequency current and voltage.

Table 1: Comparison of core DC performance after curing and before cutting Current Pomo Ni80 this invention Bs(T) 0.8 0.9 Br(T) 0.24 0.07 Hc(A/m) 2.1 2.1

Table 2: Dispersion characteristics of the elastic permeability of the two cores before cutting Frequency KHZ 10 20 50 70 100 120 150 200 Current Pomo Ni80 2850 1670 876 694 548 492 417 〃 Magnetic core of the present invention 5104 5030 4087 4760 4560 4420 4190 3860

[instance 1]

The composition is Fe38Ni38Mn2Si8B14 base material smelted in a vacuum induction furnace, and a 10mm wide amorphous strip is made by a single roll method, which is wound into a magnetic core of φ18/φ24×10mm. Subsequently, transverse magnetic annealing was performed with a magnetic field strength of 1600A/m. After annealing at 410°C for 10 minutes and then furnace cooling, the magnetic core is encapsulated with epoxy resin to make the outer dimensions of φ15/φ26×11.5mm, and a 1.8mm wide gap is cut on a grinding wheel slicer. The obtained DC hysteresis loop is shown in Figure 1. Its average magnetic permeability is 125, and the static magnetic field when it reaches saturation is 40AT/cm.

A magnetically compensated Hall current sensor with a rated measurement current of 100A (50Hz) was made with this magnetic core. The results show that its measurement accuracy is less than 1%, the measurement range is extended to 0-150A, and the response time is less than 1μS, which meets the requirements of use. .

[Example 2]

Using the same smelting and strip-making method as in Example 1, a 10mm wide amorphous strip with a composition of Fe77Si9B14 was produced and wound into a φ18/φ24×10mm annular magnetic core. After annealing at 430°C for 20 minutes under the protection of Ar gas, the DC magnetism is: Bs=1.55T, Br=0.15T, Hc=7.96A/m, and then inject the magnetic core into epoxy resin, dry and cure Bs=1.52T, its residual magnetism Br and Hc have little change, and it is cut by a grinding wheel slicer with a gap of 1.7mm in width. The B100 of the core after measuring the notch is 1.45T, and the average magnetic permeability is 180, which is higher than 125 in Example 1. And because Bs is very high, the current measurement range can be expanded to 200A after the sensor is made.

[Note 1] Toshio Naoi, Yoshiaki Kuwata, "ホ-ルフェルコックッドルスコリックセンサ-"センサ-technology. Vol.9.No.8 (1989), 48.

Claims (5)

1. The soft magnetic amorphous magnetic core production method is characterized in that the chemical composition (weight %) is: FezNiyMxSi7-10B12-15 (wherein M is Mo or Mn, x is 0-5, y is 0-40, z is 36 -78), use vacuum induction furnace to smelt rod-shaped base metal, use single-roll method to make amorphous strip with required width, wind it into ring-shaped or racetrack-shaped magnetic core, then perform partial crystallization annealing or transverse magnetic annealing, and then undergo curing treatment Forming and finally air gap cutting. 2. The method according to claim 1, characterized in that the partial crystallization annealing process is: under the protection of nitrogen or argon, the annealing temperature is 410-450°C, heat preservation for 10-30 minutes, and air cooling. 3. The method according to claim 1, characterized in that the transverse magnetic annealing process is as follows: the annealing temperature is 400-430°C, heat preservation is 10-30 minutes for furnace cooling, the magnetic field direction is along the belt transverse direction, and the magnetic field strength is greater than 1600A/m. 4. The method according to claim 1, characterized in that the curing treatment is by encapsulating and pouring semi-flexible epoxy resin. 5. The semi-flexible epoxy resin according to claim 4, characterized in that the formulation components meet the following requirements: Variety Mixing ratio (weight) epoxy resin 100 Curing agent (anhydrides, etc.) 8～16 Edge enhancer (polysulfide rubber, etc.) 5～30 Filler (silica powder, etc.) 30～50 The curing and drying process is 150°C for 3 hours.

Images