FLAKY SOFT MAGNETIC METAL POWDER AND MAGNETIC CORE MEMBER FOR RFID ANTENNA

Abstract

The performance index μ′×Q of a magnetic core member, in which an Fe—Si—Cr alloy is used, is further improved. A flaky soft magnetic metal powder, which is used in a magnetic core member for an RFID antenna comprising the above flaky soft magnetic metal powder and a binder, wherein it is composed of an Fe—Si—Cr alloy having an Ms (saturation magnetization)/Hc (coercive force) of 0.8 to 1.5 (mT/Am−1) in an applied magnetic field of 398 kA/m. In the present invention, it is preferable that the flaky soft magnetic metal powder consists of 7 to 23 at % of Si, 15 at % or less of Cr (excluding 0), and the balance being Fe and inevitable impurities, and that it has a weight-average particle size D50 of 5 to 30 μm and an average thickness of 0.1 to 1 μm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view showing an antenna module used for non-contact data communication, in which the magnetic core member of the present invention is used;

FIG. 2 is a graph showing the relationship between the real part μ′and imaginary part μ″ of a complex magnetic permeability, and an Si amount;

FIG. 3 is a graph showing the relationship between an Si amount and the performance index (μ′×Q) of a magnetic sheet;

FIG. 4 is a graph showing the frequency characteristics of complex magnetic permeability μ of magnetic sheets having different Si amounts;

FIG. 5 is a graph showing the relationship between the critical frequencies fr and loss coefficients tanδ of magnetic sheets;

FIG. 6 is a graph showing the relationship between the values of (Ms/Hc)^1/2 and critical frequencies fr of flaky Fe—Si—Cr alloy powders;

FIG. 7 is a graph showing the Ms/Hc (saturation magnetization/coercive force) of flaky Fe—Si—Cr alloy powders and the performance indexes (μ′×Q) of magnetic sheets; and

FIG. 8 is a graph showing the relationship between the performance indexes (μ′×Q) of magnetic sheets comprising flaky Fe—Si—Cr alloy powders and communication distances.

Claims

1. A flaky soft magnetic metal powder, which is used in a magnetic core member for an RFID antenna comprising the flaky soft magnetic metal powder and a binder, wherein the flaky soft magnetic metal powder is composed of an Fe—Si—Cr alloy having an Ms (saturation magnetization)/Hc (coercive force) of 0.8 to 1.5 (mT/Am−1) in an applied magnetic field of 398 kA/m.

2. The flaky soft magnetic metal powder according to claim 1, which comprises 7 to 23 at % of Si, 15 at % or less of Cr (excluding 0), and the balance being Fe and inevitable impurities, wherein the flaky soft magnetic metal powder has a weight-average particle size D50 of 5 to 30 μm, and an average thickness of 0.1 to 1 μm.

3. The flaky soft magnetic metal powder according to claim 2, wherein the amount of Si is 10 to 20 at %.

4. The flaky soft magnetic metal powder according to claim 2, wherein the amount of Si is 12 to 17 at %.

5. The flaky soft magnetic metal powder according to claim 2, wherein the amount of Cr is 0.5 to 5 at %.

6. The flaky soft magnetic metal powder according to claim 2, wherein the amount of Cr is 0.5 to 3 at %.

7. The flaky soft magnetic metal powder according to claim 2, having the weight-average particle size D50 of 10 to 25 μm.

8. The flaky soft magnetic metal powder according to claim 2, having the weight-average particle size D50 of 15 to 25 μm.

9. The flaky soft magnetic metal powder according to claim 2, having the average thickness of 0.3 to 0.7 μm.

10. The flaky soft magnetic metal powder according to claim 2, having an Ms (saturation magnetization)/Hc (coercive force) of 0.9 to 1.45 (mT/Am−1).

11. A magnetic core member for an RFID antenna, which comprises a flaky soft magnetic metal powder and a binder, wherein the flaky soft magnetic metal powder is composed of an Fe—Si—Cr alloy having an Ms (saturation magnetization)/Hc (coercive force) of 0.8 to 1.5 (mT/Am−1) in an applied magnetic field of 398 kA/m.

12. The magnetic core member for an antenna according to claim 11, wherein the flaky soft magnetic metal powder comprises 7 to 23 at % of Si, 15 at % or less of Cr (excluding 0), and the balance being Fe and inevitable impurities,the weight-average particle size D50 thereof is 5 to 30 μm, andthe average thickness thereof is 0.1 to 1 μm.

13. The magnetic core member for an antenna according to claim 12, wherein the flaky soft magnetic metal powder has an Ms (saturation magnetization)/Hc (coercive force) of 0.9 to 1.45 (mT/Am−1).

14. The magnetic core member for an antenna according to claim 11, having a thickness of 0.05 to 2 mm in a sheet-like form.

15. The magnetic core member for an antenna according to claim 11, wherein the packing ratio of the metal powder in the magnetic core member for an antenna is between 60 to 95 wt %.

16. The magnetic core member for an antenna according to claim 11, wherein the packing ratio of the metal powder in the magnetic core member for an antenna is between 70 to 90 wt %.