JP5504894B2 - Loop antenna and immunity test method - Google Patents

Description

  The present invention relates to a loop antenna, and more particularly to an antenna that performs electromagnetic sensitivity and immunity performance tests by irradiating a magnetic field or a small loop antenna that performs communication by generating a magnetic field.

  When an electronic device operates, an electromagnetic field generated with the operation of another electronic device or mechanical device arrives, the electromagnetic field causes electromagnetic interference, causes electromagnetic interference (EMI: Electromagnetic Interference), and the performance of the electronic device May cause degradation. On the other hand, in order to improve the immunity that electronic devices can operate without degradation in performance in an environment where such electromagnetic interference exists, in order to prevent performance degradation due to electromagnetic interference, It is important to identify places where electromagnetic susceptibility is strong, elucidate the mechanism of electromagnetic interference, and design with improved immunity.

  In order to identify the places where electromagnetic susceptibility is weak, an antenna is installed in the vicinity of a large scale integrated circuit (LSI) or a printed wiring board (PWB) to irradiate an electromagnetic field. Tests are being conducted to check the condition. Such tests are useful for identifying circuits and components that have weak electromagnetic immunity.

  FIG. 11 shows a configuration example when an immunity performance is evaluated by installing an antenna for irradiating a magnetic field directly above an LSI.

  FIG. 11A is a diagram of the LSI as viewed from directly above, and the antenna 10 is installed directly above the QFP (Quad Flat Pack) 1 on which the LSI is mounted so as to have a certain height from the QFP 1. In the example of FIG. 11A, the antenna 10 is made of a multilayer substrate, and the loop wiring 11 that generates a magnetic field is formed of printed wiring. FIG. 11B is a side view of the same configuration as FIG. 11A. On the mounting board 5, peripheral circuits necessary for operating the LSI are also mounted. A circuit for monitoring the operation of the LSI is also mounted on the mounting board 5.

  In FIG. 1, reference numeral 2 denotes a chip portion of the QFP 1, and 3 denotes a lead frame of the QFP 1.

  As shown in FIG. 12, the antenna 10 includes a loop wiring 11 formed by printed wiring on a printed wiring board 13, leads 12, and a connector 14. The high-frequency signal sent from the signal generator 17 is transmitted through the coaxial cable 16, the connector 14, and the lead 12 and finally supplied to the loop wiring 11. A magnetic field is generated around the loop surface around the loop wiring 11 in accordance with the law of electromagnetism. At this time, a magnetic field in a direction perpendicular to the loop surface is generally dominant. Therefore, as shown in FIG. 11B, when the antenna 10 is installed at an appropriate distance so as to be parallel to the QFP mounted on the mounting board 5, it is possible to irradiate a magnetic field with little intensity change over the entire surface of the QFP. it can. The cause of the malfunction of the LSI is specified while controlling the intensity, modulation, waveform, etc. of the magnetic field generated by changing the setting of the signal generator 17. In FIG. 11A, an antenna having almost the same size as QFP is used, but there is also a test method in which irradiation is performed in a limited range using an antenna smaller than QFP. In this case, a magnetic field is irradiated while a small antenna is scanned on the QFP at a predetermined height, and a circuit with weak immunity is specified.

FIG. 13 is an explanatory diagram of a method of measuring the magnetic field on the surface of the antenna 10 of FIG. As shown in FIGS. 13A and 13B, FIG. 14A is a diagram in which a small magnetic field probe 15 is installed in the vicinity of the loop wiring 11 and a magnetic field is measured while being scanned in the XY axis direction at a certain height and visualized. In FIG. 14A, since the magnetic field in the vicinity of the loop wiring 11 has components in the X, Y, and Z directions, the X direction component (Hx), the Y direction component (Hy), and the Z direction are changed while changing the installation axis of the small magnetic field probe 15. The intensity of the component (Hz) is measured and combined and displayed as Hxyz = (x ² + y ² + z ² ) ^(1/2) .

  The measurement was performed by connecting the small magnetic field probe 15 to a measuring instrument such as a spectrum analyzer, and the output of the small magnetic field probe 15 was measured by oscillating the antenna 10 at 10 MHz. 14A and 14B show the measurement results obtained by scanning the small magnetic field probe 15 over the entire loop surface. 14A and 14B, the center of the loop wiring 11 is (x, y) = (18 mm, 18 mm). The outer shape of the loop wiring 11 in FIG. 13B is 24 mm square, the width of the loop wiring 11 is 1 mm, and the small magnetic field probe 15 is measured 6 mm apart. In FIG. 14A, it can be seen that a strong magnetic field is generated over the entire surface in the range surrounded by the loop wiring 11. FIG. 14B shows the result of measuring the magnetic field while performing one-dimensional scanning on the line AA ′ passing through the center of the loop wiring 11 in FIG. 13B with the Y and Z coordinates being constant. In the position of X = 18 mm of FIG. 14B, it means that the small magnetic field probe 15 exists in the center of the loop wiring 11. Although asymmetry due to measurement errors is recognized, the distribution is almost symmetrical.

As can be seen from FIG. 14B, Hz is dominant in the region surrounded by the loop wiring 11. There is a region where Hx becomes strong near the loop wiring 11, but its strength is lower than that of Hz. If the measurement distance of the small magnetic field probe 15 is further reduced and becomes smaller than 1 mm, Hx may be dominant compared to Hz, but the distance between the loop and the object in a normal use state is considered. Then, the distribution form of FIG. 14A is a typical distribution. Hy is a direction in which no magnetic field is observed in principle, and thus has a very low value. The magnitude of Hxyz = (x ² + y ² + z ² ) ^(1/2) , which is a combined magnetic field in the x, y, and z directions, is almost similar to the distribution of Hz, but in the region where Hx becomes strong, Hxyz Becomes larger than Hz. Therefore, in the case of FIG. 14B, Hxyz is almost a combination of Hz and Hx. In the region surrounded by the loop wiring 11, the intensity change of the composite magnetic field Hxyz is small and only changes by about 8%. 14A and 14B are both normalized and displayed with the maximum value. When the loop wiring 11 is manufactured in the same size as the QFP and installed on the QFP, as shown in FIG.

  FIG. 15A schematically shows the test method for irradiating the magnetic field described above. The shaded area is a region where a strong magnetic field is generated, and the inside of the loop wiring 11 almost belongs to this region. When the distance between the QFP 1 and the antenna 11 is changed, the distribution shape also changes, but it is general to perform the test at a measurement distance that is close to a uniform distribution. More specifically, when the antenna 10 is very close to the LSI chip 1 or the lead frame 3 to be tested, a strong magnetic field is generated only in the vicinity of the loop wiring 11 and the magnetic field strength at the center of the loop wiring 11 is reduced. That is, an annular magnetic field distribution is generated. However, in the case of QFP, because of the thickness of the package, the loop wiring 11 must be placed away from the chip 1 and the lead frame 3. In this case, the magnetic field near the center of the loop wiring 11 becomes strong, and as a result, a strong magnetic field is generated in the loop plane exemplified in FIG. 14A. Therefore, changing the installation distance of the antenna 10 to generate an annular magnetic field is very restrictive.

  In the above, the case where the test is performed by irradiating a magnetic field is exemplified, but if an antenna that generates a uniform electric field is used, it can be applied to a malfunction test by an electric field.

  In FIG. 15A, since the magnetic field is irradiated over the entire surface of QFP1, it is possible to evaluate the immunity of the entire QFP1, but it is not possible to evaluate each part. As shown in FIG. 15B, it is possible to irradiate the magnetic field only to the chip 2 on which the LSI is formed by creating the loop wiring 11 having a small outer dimension, but the lead frame 3, QFP1 and the pad on the chip are connected. It is impossible to irradiate the magnetic field only to the bonding wire 4 to be performed. In particular, in a frequency band of 1 GHz or less, noise is generated in the lead frame 3 and the bonding wire 4 due to an electromagnetic field coming from the outside, and may be larger than noise generated inside the chip 2 due to the same external electromagnetic field. In this case, the noise generated in the lead frame 3 and the bonding wire 4 becomes conductive noise and enters the chip 2 from the terminal portion to cause a malfunction. Therefore, even if a countermeasure is taken to prevent the electromagnetic field from entering the chip 2 from the outside. The effect cannot be expected. Therefore, it is important to select the lead frame 3 and the bonding wire 4 and perform the test in order to select a correct noise countermeasure.

  FIG. 15C shows a case where the bonding wire 4 and a portion where the bonding wire 4 is connected to the lead frame 3 (that is, a portion where the lead frame 3 is tapered) are selected and a magnetic field irradiation test is performed, and FIG. This is a case where a test for irradiating a magnetic field including the wiring 6 on the board 5 is performed. In this way, if a magnetic field generation method that generates a strong magnetic field in an annular shape is used, it is possible to test by combining the chip 2, the bonding wire 4, the lead frame 3, and the wiring 6 on the mounting board, and the electromagnetic sensitivity is strong. It is possible to identify a mounting component that causes a decrease in immunity.

  FIG. 16 shows an example in which a magnetic field is selected for each circuit. In FIG. 16A, a test including all components connected to a circuit to be tested is performed instead of selecting at the mounting component level. Examples of the circuit include a power supply circuit, a data port, an I / O port for signal transmission, and the like, but pins connected to similar circuits are often adjacent on the QFP. In that case, as shown in FIG. 16B, for example, there is a case where it is not desired to irradiate a specific lead frame 3.

  As described above, the conventional technology has a drawback that it is not possible to select a mounted component or circuit and irradiate a magnetic field from the outside, and it is not possible to sufficiently identify a circuit or component having low immunity performance.

  Next, publicly known documents recognized by the applicant will be described.

  In Patent Document 1, a first half loop 3c, a circular loop 3e, and a second half loop 3g are connected in series, and a first annular loop composed of a first half loop 3c and a second half loop 3g. There is disclosed a loop antenna in which an antenna portion and a second annular antenna portion formed of a circular loop 3e are formed in the same shape and the same size, and the first and second annular antenna portions are brought into close contact with each other.

  Patent Document 1 describes that signal transmission can be performed without causing problems in the Radio Law. This is considered that the magnetic field distribution is a problem at a distance where the magnetic fields generated by the loop antenna are sufficiently combined.

  Further, FIG. 2C of Patent Document 2 discloses a coil antenna for a non-contact communication apparatus in which the loop portion of the loop antenna is wound a plurality of times to increase the magnetic field strength.

  Neither Patent Documents 1 and 2 are used for immunity measurement.

Further, the above Patent Document 1 describes that signal transmission can be performed without causing a problem in the radio wave law. This is considered that the magnetic field generated by the loop antenna is sufficiently synthesized, that is, the magnetic field distribution at a distance sufficiently away from the loop antenna is a problem. On the other hand, this invention makes the subject magnetic field distribution near a loop antenna, and controls the magnetic field distribution near a loop antenna.
JP 62-61430 A Japanese Patent Laying-Open No. 2006-74348 (second embodiment)

  The present invention has been made in view of the above points, and the object of the present invention is to control the magnetic field distribution in the vicinity of the loop antenna, thereby enabling the generation of an annular magnetic field distribution according to the measurement target, It is intended to provide a novel loop antenna that can accurately identify circuits and components with low immunity performance.

  Another object of the present invention is to provide an electronic device that can prevent malfunction by selectively attenuating a magnetic field around a part that is not desired to be irradiated with a magnetic field in an electronic device having an extremely short distance communication function. It is.

In order to achieve the above-described object, the present invention basically employs a technical configuration as described below.
That is, the first aspect of the loop antenna according to the present invention is:
A first annular conductor;
One or more second annular conductors that are smaller than the first annular conductor and are located inside the ring of the first annular conductor;
The second annular conductor is connected in series with the first annular conductor;
The first annular conductor and the second annular conductor are arranged on the same plane,
The second aspect is
A first annular conductor formed on the substrate;
One or more second annular conductors that are smaller than the first annular conductor and are located inside the ring of the first annular conductor;
The second annular conductor is connected in series with the first annular conductor;
The first annular conductor and the second annular conductor are arranged on different surfaces of the substrate,
The third aspect is:
An annular conductor;
Consisting of a metal plate disposed inside the ring of the annular conductor,
The annular conductor and the metal plate are arranged on the same plane,
The fourth aspect is:
An annular conductor formed on the substrate;
Consisting of a metal plate disposed inside the ring of the annular conductor,
The annular conductor and the metal plate are arranged on different surfaces of the substrate,
The fifth aspect is:
A substrate,
An annular conductor provided on the first surface of the substrate;
A metal pad provided on the inner side of the ring of the annular conductor on the first surface of the substrate and for connecting an inner conductor or an outer conductor of the coaxial cable;
A metal plate provided on a second surface different from the first surface of the substrate and connected to the metal pad by a plurality of vias;
The coaxial cable is connected perpendicularly to the substrate surface,
The sixth aspect is
A substrate,
An annular conductor provided on the first surface of the substrate;
A metal pad provided inside the ring of the annular conductor on a second surface different from the first surface of the substrate, for connecting an inner conductor or an outer conductor of the coaxial cable;
A metal plate provided on the first surface of the substrate and connected to the metal pad by a plurality of vias;
The coaxial cable is connected perpendicularly to the substrate surface.

The aspect of the magnetic field generation method according to the present invention is as follows.
A first annular conductor; and one or more second annular conductors that are smaller than the first annular conductor and are located inside the ring of the first annular conductor, wherein the second annular conductor is A loop antenna connected in series with the first annular conductor is driven at a frequency having a wavelength sufficiently longer than the total length of the first annular conductor and the second annular conductor, and an annular magnetic field distribution is obtained. It is characterized by generating.

  Since the loop antenna of the present invention is configured as described above, it is possible to selectively irradiate a magnetic field, and it becomes easy to specify a component with low immunity performance.

  In addition, the mounting method of the loop antenna of the present invention can selectively attenuate the magnetic field around a part that is not desired to be irradiated with a magnetic field in an electronic device having an extremely short-range communication function, thereby preventing malfunction.

It is a figure which shows an example of a structure of the loop antenna of this invention. It is a side view of FIG. 1A. It is a figure which shows magnetic field distribution near the loop antenna of this invention. It is a figure which shows magnetic field distribution near the loop antenna of this invention. It is a figure explaining the other structural example of the loop antenna of this invention. It is a figure explaining the other structural example of the loop antenna of this invention. It is a figure explaining the other structural example of the loop antenna of this invention. It is a figure explaining the structure of the loop antenna which has a conductor board of this invention. It is a figure which shows the example which has arrange | positioned the connection pad in the inside of a cyclic | annular conductor in the figure of FIG. 4A. It is a figure which shows the conductor board provided in the other surface of the printed wiring board of FIG. 4B. It is a figure explaining the other structural example of the loop antenna of this invention. It is a figure explaining the other structural example of the loop antenna of this invention. It is a figure explaining the other structural example of the loop antenna of this invention. It is a figure explaining the other structural example of the loop antenna of this invention. It is a figure which shows that a lead frame does not exist in the 45 degree | times direction of QFP. It is a figure explaining the other structural example of the loop antenna of this invention. It is a figure explaining the other structural example of the loop antenna of this invention. It is the figure which applied the loop antenna of this invention to SiP. FIG. 9B is a side view of FIG. 9A. It is a figure which shows that both the chips | tips shown to FIG. 9A are connected by the wiring on an interposer. It is a figure which compares the magnetic field distribution of the loop antenna of this invention, and the conventional loop antenna. It is a figure explaining the conventional immunity test method. FIG. 11B is a side view of FIG. 11A. It is a figure explaining the conventional loop antenna. It is a figure explaining the measuring method of the magnetic field distribution of the conventional loop antenna vicinity. FIG. 13B is a top view of FIG. 13A. It is a figure which shows an example of the magnetic field distribution of the conventional loop antenna vicinity. It is a figure which shows an example of the magnetic field distribution of the conventional loop antenna vicinity. It is a figure which shows the case where a magnetic field is irradiated over the QFP whole surface in a magnetic field irradiation method. It is a figure which shows the case where a magnetic field is irradiated only to the chip | tip in which the loop wiring with a small outer diameter dimension is created and LSI is formed in the magnetic field irradiation method. It is a figure which shows the case where the part which connects a bonding wire and a bonding wire to a lead frame is selected, and a magnetic field is irradiated in a magnetic field irradiation method. It is a figure which shows the case where a magnetic field is irradiated including even the wiring on a mounting board in a magnetic field irradiation method. It is a figure which shows the case where the test containing all the components connected to the circuit to be tested in a magnetic field irradiation method is performed. It is a figure which shows the case where a magnetic field is not irradiated to a specific lead frame in a magnetic field irradiation method.

Explanation of symbols

1 QFP
2 chip 3 lead frame 4 bonding wire 5 mounting board 6 wiring 10 antenna 11 loop wiring 12 lead 13 printed wiring board 14 connector 15 small magnetic field probe 16 coaxial cable 17 signal generator 18 probe head 20 loop antenna 21 printed wiring board 22 annular conductor 23 annular conductor 24 connection wiring 25 connection wiring 26 coaxial cable 27 sleeve 28 conductor pattern 30a pad 30b pad 31a current 31b current 32 conductor plate 33 via 34 via 50 interposer 51 chip 52 chip 58 wiring 59 wiring 60 spacer 61 annular conductor 62 annular conductor

  The loop antenna according to the present invention includes a first annular conductor and one or more second annular conductors that are smaller than the first annular conductor and are located inside the ring of the first annular conductor. A structure in which an annular magnetic field is generated in a region sandwiched between the annular conductor and the second annular conductor to selectively irradiate the magnetic field and identify a component with low immunity performance. It is.

  The loop antenna of the present invention may be configured such that the first annular conductor and the second annular conductor are connected in series and driven by one signal source. The second annular conductor may be driven by different signal sources.

  In addition, as a shape of the annular conductor of this invention, the polygon containing a rectangle and a circle is included.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram for explaining an embodiment of the loop antenna 20 of the present invention.

  The loop antenna 20 of the present invention includes a printed wiring board 21 and a conductor pattern 28 formed thereon. The conductor pattern 28 includes an annular conductor 22 formed so as to go around the outside, an annular conductor 23 connected in series to a part of the conductor pattern 28, and connection wiring 24 connecting the respective annular conductors. The annular conductor 23 has a smaller outer dimension than the annular conductor 22 and is disposed on the inner side of the annular conductor 22. The annular conductor 22 is connected to the connection wiring 25, and the other end of the connection wiring 25 is connected to the pads 30a and 30b. The side view of FIG. 1B shows a state in which the coaxial cable 26 is vertically connected to the printed wiring board 21, while the central conductor of the coaxial cable is electrically connected to the pad 30a using a method such as soldering. Fixed. On the other hand, the outer conductor of the coaxial cable is connected to the pad 30 b via the sleeve 27. By making such a connection, it is possible to connect the conductor pattern 28 vertically while suppressing the collapse of the coaxial structure. The other end of the coaxial cable 26 is connected to the signal generator 17, and a signal transmitted from the signal generator 17 is transmitted to the annular conductors 22 and 23, and a magnetic field is generated around the annular conductors 22 and 23 according to the laws of electromagnetics. . By fixing the coaxial cable 26 vertically, the antenna 20 can be brought close to the QFP 1 at a constant height as shown in FIG. 11B.

  2A and 2B show the results of measuring the magnetic field on the loop antenna 20 using the same measurement system as in FIGS. 13A and 13B. Each figure is normalized and displayed with the maximum value. In FIG. 2A, the center of the annular conductor of the loop antenna 20 is at (x, y) = (18 mm, 18 mm). The outer dimension of the annular conductor 24 is 24 mm, the outer dimension of the annular conductor 23 is 15 mm, and the wiring width is 1 mm. In FIG. 2A, it can be seen that the magnetic field strength at the center portion is reduced, and a strong magnetic field is generated in an annular shape. FIG. 2B shows the result of measuring the distribution on the AA ′ line in FIG. 13B, but two peaks are observed.

  This peak is almost located in a region sandwiched between the annular conductor 22 and the annular conductor 23. Assuming that the current 31a supplied from the signal generator 17 flows through the annular conductor 22 in FIG. 1A, the annular conductor 22 generates a magnetic field in the center portion in a direction penetrating from the front to the back of the page. At this time, since the current 31b flowing through the annular conductor 23 is opposite to the current 31a, a magnetic field is generated in the central portion in a direction penetrating from the back side to the front side of the drawing.

  In FIG. 1A, since the centers of the annular conductor 22 and the annular conductor 23 coincide, the strength of the combined magnetic field of the annular conductor 22 and the annular conductor 23 decreases near the center. It can also be considered that the conductor pattern 28 includes two loop antennas having different directions of oscillation in the same phase.

  The above results are obtained when the two loop antennas in FIG. 1A are driven with a signal having a frequency that is sufficiently longer than the total length of the annular conductors 22 and 23, and such frequencies are selected. As a result, the annular conductors 22 and 23 are driven in phase and generate a magnetic field, so that the annular magnetic field distribution shown in FIG. 2A can be obtained. When the wavelength is shorter than the entire length of the annular conductor, the influence of the voltage / current distribution on the annular conductor becomes large, and it becomes impossible to generate an annular magnetic field distribution having a uniform magnetic field strength.

  In FIG. 1A, the annular conductors 22, 23 have a shape close to a square. When the measurement object is QFP, the test can be performed over the entire surface of the object by making it square. Usually, the QFP 1 and the chip 2 are substantially square and have a positional relationship such that each side is parallel. Therefore, as shown in FIG. 1A, by arranging the annular conductor 23 in the center of the annular conductor 22 so that each side is parallel, the irradiation range shown in FIG. 15 can be selected and irradiated.

  When the measurement object is circular or when it is desired to irradiate a part of the measurement object with a magnetic field, the conductor pattern 28 may be designed according to the shape. Therefore, the conductor pattern 28 is manufactured in a rectangular shape, a trapezoidal shape, a circular shape, an elliptical shape, or a polygon shape according to the purpose. The annular conductor 22 and the annular conductor 23 do not need to have the same shape, and a combination of different shapes as shown in FIG. 3A is allowed. FIG. 3C is an example in which a plurality of annular conductors 23 are arranged.

  In addition, the center of the annular conductor 22 and the center of the annular conductor 23 do not have to coincide with each other, and the annular conductor 23 can be installed at an asymmetric position with respect to the annular conductor 22. In a package such as SiP (System in Package), the chip is often mounted at an asymmetric position, and such a mounting method can be supported.

  By using the loop antenna 20 described above, it becomes possible to irradiate a magnetic field to the annular region shown in FIGS. 15C and 15D, which is useful for specifying components and circuits having high electromagnetic sensitivity.

  If the chip 2, the bonding wire 4, the lead frame 3, and the printed wiring 6 are assigned to the factor A, the factor B, the factor C, and the factor D, respectively, the factor A is always included in the test method using the conventional antenna 10. In other words, if the test is performed while changing the outer dimensions of the loop wiring 11, the electromagnetic immunity in the combination of factor A, factor (A + B), factor (A + B + C), factor (A + B + C), factor (A + B + C + D) is measured. become. In such a method of selecting the irradiation area in the addition formula, for example, when the contribution of the factor A to the immunity is large, the contribution of the other factors cannot be separated. There was a demerit that the effect of was difficult to separate. In the present invention, for example, it is possible to perform a test in which some of the adjacent factors such as the factor (B + C), the factor (C + D), and the factor C are excluded, thereby facilitating the factor analysis and reducing the electromagnetic sensitivity. Helps identify high components and circuits.

  FIG. 4A shows a structure in which the inner annular conductor 23 is replaced with a conductor plate 32 made of a metal plate having a predetermined area. In FIG. 4A, the conductor plate 32 is disposed at the center of the annular conductor 22. When the annular conductor 22 is driven at a predetermined frequency, a strong magnetic field is generated inside the ring. However, if the conductor plate 32 is thick enough to prevent the magnetic field from penetrating, the magnetic field at the center of the conductor plate 32 is attenuated. Although the operation is not positively canceled as in the case of the loop antenna 20, an annular distribution similar to that of the loop antenna 20 can be obtained. If each side of the conductor plate 32 is formed to be parallel to each side of the annular conductor 22, the magnetic field distribution shown in FIGS. 15B and 15C can be generated. Moreover, what is necessary is just to select arbitrary shapes, such as a trapezoid, as the shape of the conductor board 32 according to the state to measure. Moreover, you may comprise so that the shape of an annular conductor and the shape of a metal plate may differ.

  In FIG. 4A, pads 30a and 30b for connecting the coaxial cable 26 are arranged outside the annular conductor 22 provided on one surface of the printed wiring board 21, but FIG. In this example, the connection pads 31 a and 31 b are arranged inside the annular conductor 22.

  4C is a conductor plate 32 provided on the other surface of the printed wiring board 21 of FIG. 4B. The conductor plate 32 is connected by a pad 31b and a via 33, and the ground conductor of the coaxial cable 26 together with the pad 31b. Connected to. Also in this case, the magnetic field attenuates around the conductor plate 32 as in FIG. 4A. Since the coaxial cable 26 can be installed inside the annular conductor 22, the size can be reduced.

  Although not shown, the conductor plate 32 is disposed inside the annular conductor 22, the conductor plate 32 is formed on the same surface as the annular conductor 22, and the pads 31 a and 31 b are opposed to the conductor plate 32 to be a conductor. You may comprise so that it may provide in the surface different from the surface in which the board 32 is provided.

  In FIG. 5A, the shape of the annular conductor 22 is a polygon, and a magnetic field is applied only to the area indicated by the oblique lines in FIG. 16A. Normally, the loop antenna is square or annular, but as shown in FIG. 5A, a magnetic field can be applied only to the lead frame to be tested if it matches the shape of the QFP lead frame. Furthermore, if an annular conductor is formed inside as shown in FIG. 5B, the magnetic field strength around the lead frame not to be tested can be attenuated as shown in FIG. 16B.

  FIG. 6A shows an embodiment of the present invention in the case where the connection wirings 24 and 25 are arranged in parallel with the side of the QFP. When the connection wiring 25 is formed in this way, a distribution in which the magnetic field is not originally required is formed around the connection wiring 25, the magnetic field strength is lowered, and there is a possibility that some lead frames are not irradiated with a sufficiently strong magnetic field. . On the other hand, in FIG. 1A or FIG. 6B, the connection wiring 25 is connected to the corner of the annular conductor 22 formed in a rectangular shape, and is drawn out at an angle of 45 degrees with each side of the annular wiring. On the other hand, the connection wiring 24 is disposed adjacent to the connection wiring 25, and the angle formed by the connection wirings 24 and 25 is 0 degree. When the measurement object is QFP, the lead frame is often not arranged at the corner. Therefore, as shown in FIGS. 1A and 6C, the lead frame inside the QFP is extended with respect to the adjacent side of the QFP, so that the interval in the 45 degree direction is wide. If the connection wiring 25 is arranged in the diagonal direction where there is no lead frame, a uniform magnetic field can be applied to a region necessary for the test. The connection wiring 25 does not have to be arranged linearly with the connection wiring 24, and may form an angle of 45 degrees. In FIG. 6B, the connection wiring 24 and the connection wiring 25 are partially shared.

  When the annular conductor is a polygon, it is desirable to provide the connection wiring 25 at the corner where two sides of the polygon intersect.

  In FIG. 7, the annular conductor 22 and the annular conductor 23 are formed in different layers. The annular conductor 23 is disposed inside the annular conductor 22, and the annular conductor 22 and the annular conductor 23 are connected in series by a via 34. The distance in the direction perpendicular to the loop surface of the annular conductor 22 and the annular conductor 23 can be changed by controlling the thickness of the printed circuit board 21 and the intensity distribution on the QFP 1 can be controlled.

  As described above, a characteristic magnetic field distribution can be generated by using the antenna of the present invention in a frequency band having a wavelength sufficiently longer than the entire length of the annular conductor. If a loop antenna 20 in which two annular conductors illustrated in FIG. 1A are connected in series is used, an annular magnetic field distribution can be generated immediately.

  Further, as shown in FIG. 8, if the two annular conductors are operated independently, the strength of the magnetic field can be locally adjusted, and the same effect as the loop antenna 20 can be obtained. In the case of FIG. 8, since the annular conductors 61 and 62 can be controlled independently, the phase of the supplied signal can be reversed or the amplitude can be changed, and the generated magnetic field distribution can be controlled efficiently. Therefore, precise control is possible as compared with the integrated type of FIG. 1A.

  By using these magnetic field distribution generation methods, as already described, it is possible to test the QFP 1 and chip 2 constituting the LSI package and the wiring on the printed circuit board, and to perform an immunity test for analyzing the malfunction state of the LSI. Efficiency can be improved.

  Next, another embodiment of the present invention will be described.

  The loop antenna of the present invention described above can be applied to a transmission / reception antenna built on a printed wiring board or an LSI package.

  9A and 9B show an apparatus in which a printed wiring board 21 in which a loop antenna is formed is mounted on a SiP (System in Package) via a spacer 60. FIG.

  The reason why the planar antenna is mounted on the printed board is to realize a reduction in thickness and size. For this reason, the distance between SiP and an antenna conductor is very near, for example, 1 mm or less. Two chips 51 and 52 are mounted on the interposer 50 by BGA. As shown in FIG. 9C, the chips 51 and 52 are connected to each other by wirings 58 and 59 on the interposer. This is for recombination of wiring on the interposer 50. When the number of wirings to be connected increases, the wiring 58 becomes a first layer and the wiring 59 becomes a second layer.

  Such SiP is used in a wireless medium such as an IC card or a wireless tag that reads and writes information without contact. Moreover, it may be mounted inside an information terminal device such as a mobile phone. The loop antenna 20 of this embodiment is used when wirelessly transmitting / receiving information to / from an external device. A typical example of a conventional antenna is the loop antenna 10 illustrated in FIG. As described above, such a loop antenna 10 generates a substantially uniform magnetic field distribution as shown in FIG. 14A.

  The loop antenna 20 of the present invention is driven by a chip 51 to generate a magnetic field, and communicates with an external LSI at an extremely short distance. At this time, since the wiring formed on the interposer such as the wirings 58 and 59 is longer than the on-chip wiring, it is easily affected by an external electromagnetic field in a frequency band lower than that of the chips 51 and 52. For this reason, when the conventional antenna 10 is used in place of the loop antenna 20, a large noise voltage is generated in the wirings 58 and 59, which becomes conductive noise and enters the circuits inside the chips 51 and 52, causing the circuit to malfunction. That is, the result is that the intrusion of noise is eventually allowed by the wirings 58 and 59 that are more sensitive to electromagnetic fields coming from the outside than the chips 51 and 52 alone.

  As already described, the loop antenna 20 of the present invention generates an annular magnetic field distribution in the vicinity of the loop antenna 20 and has a weak magnetic field strength at the center. That is, in the region where the wiring having strong electromagnetic sensitivity exists in the central portion of FIG. 9A, the magnetic field strength becomes weak, and thus it is possible to reduce the risk of malfunction.

  In an IC card or the like, a receiving antenna is installed so as to face the antenna 20, and communication at an extremely short distance is performed. When the loop antenna 10 having substantially the same outer dimensions is used as the reception antenna, the output of the reception antenna of the loop antenna 20 is lowered when the antenna 10 and the loop antenna 20 are excited with the same power. This is because the magnetic field strength at the center of the loop antenna 20 is attenuated. If the total amount of the magnetic field in the loop of the receiving antenna is equal, the gain at the time of transmission / reception does not decrease. Comparing the integrated value of the magnetic field in the loop with the same outer dimensions of the receiving antenna as the transmitting side, if the transmission power of the loop antenna 20 is increased by 1.8 times, a magnetic field equivalent to the antenna 10 is generated, and the output of the receiving antenna Are equivalent. FIG. 10 compares the magnetic field distribution at this time. Even in this case, the magnetic field strength near the center of the loop antenna 20 is about 30% smaller than the magnetic field strength near the center of the loop antenna 10 and about 10 dB smaller in decibel notation. Therefore, it is possible to expect the effect that the parts near the center are protected while having the same gain as the conventional type. FIG. 10 shows the result of measuring the magnetic field distribution generated by the antenna 10 and the loop antenna 20 and is normalized by the maximum value of the loop antenna 20.

  This application claims the priority on the basis of Japanese application Japanese Patent Application No. 2008-30739 for which it applied on February 12, 2008, and takes in those the indications of all here.

  The present invention is applicable to a loop antenna, an electronic device having an extremely short-range communication function, and other related devices.

Claims (10)

An immunity test method that uses a loop antenna to generate an annular magnetic field distribution in the vicinity of the loop surface and examines malfunction of an electronic device, wherein the loop antenna is
A first annular conductor;
One or more second annular conductors that are smaller than the first annular conductor and are located inside the ring of the first annular conductor;
The second annular conductor is connected in series with the first annular conductor;
By using a signal having a frequency having a sufficiently long wavelength compared with the total length of the first annular conductor and the second annular conductor, the signal between the first annular conductor and the second annular conductor is used. wherein said that the circular magnetic field distribution is formed in the region
Immunity test method. 2. The immunity test method according to claim 1, wherein the shape or arrangement of the first annular conductor and the second annular conductor is designed so that the shape of the magnetic field distribution matches a measurement target. .   An electronic device that performs extremely short-range communication using a loop antenna,
  The loop antenna is mounted on the electronic device so that the magnetic field strength of the loop antenna in a region where a circuit or component that is not desired to be irradiated with a magnetic field is weaker than the magnetic field strength of the loop antenna in another region,
  The loop antenna is
A first annular conductor;
One or more second annular conductors that are smaller than the first annular conductor and are located inside the ring of the first annular conductor;
The second annular conductor is connected in series with the first annular conductor;
By using a signal having a frequency having a sufficiently long wavelength compared with the total length of the first annular conductor and the second annular conductor, the signal between the first annular conductor and the second annular conductor is used. An annular magnetic field distribution is formed in the region
Electronics. An annular conductor;
A conductor plate made of a metal plate having a predetermined area disposed inside the ring of the annular conductor;
A magnetic field generated by energizing the annular conductor is attenuated by the conductor plate, thereby forming an annular magnetic field distribution in a region between the annular conductor and the outer peripheral portion of the conductor plate. Loop antenna. 5. The loop antenna according to claim 4, wherein the shape or arrangement of the annular conductor and the conductor plate is designed such that the shape of the magnetic field distribution matches a measurement target. The loop antenna according to claim 4 or 5, wherein the annular conductor and the conductor plate are formed on different surfaces of the substrate . The conductor plate, the loop antenna according to any one of claims 4-6, characterized in that connecting the ground conductor and electrically coaxial cable for supplying electricity to the annular conductor. The loop antenna according to claim 7, wherein a connection point between the conductor plate and the ground conductor is inside the annular conductor. Immunity Test method characterized by to generate a magnetic field distribution in the annular near the loop plane, examine the malfunction of electronic equipment using a loop antenna as claimed in any one of claims 4-8. An electronic device for performing very short-range communications using a loop antenna as claimed in any one of claims 4-8,
Magnetic field intensity of the loop antenna of the area circuits or components do not want to irradiate the magnetic field is arranged so as to be weaker than the magnetic field intensity of the loop antenna in the other region, the loop antenna is mounted to the electronic device electronic apparatus, characterized in that there.

Images