JP2012255659A - Electric conduction point evaluation device of metal plate surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric conduction point evaluation device of a metal plate surface, capable of easily evaluating the state of electrical conduction parts of a replaceable metal sample plate.SOLUTION: An inventive electric conduction point evaluation device includes: a metal base plate 1 provided on insulator-made legs, having a thickness of equal to or less than 1 mm, and having a smooth surface; a plurality of measuring terminals 3 connected to the rear side of the base plate 1 in a grid and a ground line G connected to the rear side of the base plate; a power source 4 applying a voltage between the base plate 1 and a sample plate S mounted thereon to cause electric conduction; a relay part 5 changing connection for each measuring terminal 3; a potentiometer 6 for measuring a potential to the ground line G for each terminal; potential distribution calculation means 7 for obtaining potential distribution of a measuring object part of the rear face of the base plate 1 from measured potentials of all of the plurality of measuring terminals 3 measured by the potentiometer 6; and electrical conduction state information acquisition means 8 for acquiring electrical conduction state information such as the positions and the numbers of electrical conduction parts of the sample plate S on the basis of acquired potential distribution information.

Description

  The present invention relates to a conduction point evaluation device for a metal plate surface used for evaluation of a conduction point on the surface of a metal plate used for a housing or the like of an electronic device.

OA equipment and electrical appliances are required to shield electromagnetic waves leaking from electronic circuits incorporated in the products. This is because leaked electromagnetic waves not only may cause other OA devices and appliances to malfunction, but also may cause electronic devices such as cardiac pacemakers to malfunction and adversely affect the person using them. It is.
In many office automation equipment and electrical appliances, an electromagnetic wave source is housed in a metal casing such as a steel plate or an aluminum plate to suppress leakage of electromagnetic waves. Generally, as shown in FIG. 5, the housing has a structure in which a metal lid is stacked on a metal box with a flange. As shown in the figure, the portion where the flange and the lid of the housing overlap is the “portion where the two metal plates overlap”. Unless the overlapping portions of the metal plates are continuously joined by welding or the like, a gap is generated between the metal plates, and electromagnetic waves leak from the gap.

  Here, when electromagnetic waves leak from the part where the metal plates overlap, it has been empirically known that the lower the surface resistance of the metal plates, the smaller the leakage of electromagnetic waves, and the case where the surface resistance is used as an evaluation index. There are many. The surface resistance of the metal plate is determined by a four-terminal method (see Non-Patent Document 1) or a method as disclosed in Patent Document 1 (the first and second electrodes are spaced from each other on the object to be measured, and the two electrodes are placed In general, an AC voltage is applied to the object to be measured to cause a current to flow through the object to be measured, and the surface resistance of the object to be measured is calculated based on this current.

JP 2000-230949 A JP 2007-139750 A

P. Practical surface modification technology overview 560-P. 561

However, it has been found that when electromagnetic waves leak through a portion where the metal plates overlap, the state of the current-carrying portion at the overlapped portion greatly affects the characteristics of the electromagnetic waves. Therefore, simply measuring the surface resistance of a metal plate is not an essential index for evaluating leakage of electromagnetic waves.
Here, for example, Patent Document 2 proposes a method of measuring the position and shape of the current-carrying portions of the overlapping metal plates. In this measurement method, a metal plate with a conductive wire connected to the surface is overlapped with another metal plate, and a current is passed between these metal plates, and the position and shape of the current-carrying part are determined from the potential distribution on the surface of the metal plate. Looking for. However, since this measurement method is a method of measuring the state of the current-carrying part between specific metal plates, it is possible to freely replace the metal sample plate and evaluate the state of the current-carrying part of the sample plate. Have difficulty.

  Therefore, the present invention has been made paying attention to such problems, and the metal sample plate can be freely replaced, and the state of the current-carrying portion of the replaced sample plate can be easily evaluated. An object of the present invention is to provide a device for evaluating a conduction point on the surface of a metal plate to be obtained.

  In order to solve the above problems, the present invention is an energization point evaluation apparatus for evaluating the state of an energization point of a metal sample plate, and has a thickness of 1 mm or less provided on an insulator leg. A metal substrate having a smooth surface, a plurality of measurement terminals connected in a grid pattern at any one interval within a range of 3 to 10 mm over the entire measurement target portion on the back surface of the substrate, and one ground A line, a power source that applies a voltage between the substrate and the sample plate placed on the front surface of the substrate, and a relay unit that switches connection for each of the plurality of measurement terminals; , A potentiometer that sequentially measures the potential with respect to the ground line for each terminal switched by the relay unit, and from the measured potentials of all of the plurality of measurement terminals measured by the potentiometer, Potential to obtain potential distribution Cloth calculating means; and energization state information acquiring means for acquiring energization state information such as the position of the energizing part and the number of energizing parts of the sample plate based on the potential distribution information acquired by the potential distribution calculating means. It is characterized by that.

  According to the energization point evaluation apparatus for the metal plate surface according to the present invention, the sample plate is placed on the front surface of the metal substrate, so that the sample plate can be freely replaced. The substrate is a metal plate having a thickness of 1 mm or less and a smooth surface provided on the legs made of an insulator, and within a range of 3 to 10 mm over the entire measurement target portion on the back surface. A plurality of measurement terminals connected in a grid pattern at any one interval are attached, and the potentiometer sequentially measures the potential with respect to one reference ground line for each terminal switched by the relay unit. Therefore, a current can be passed between the substrate and the sample plate, and the potential of each terminal with respect to the ground line can be measured. As a ground line, any terminal may be used as a potential reference (ground), and the other measurement terminals are connected to the relay unit. A potentiometer is connected so that the potential difference between the terminal selected in the relay section and the reference terminal can be measured, and a voltage is applied between the substrate and the sample plate placed on the front surface of this substrate by the power supply. By measuring the potential difference between all terminals and one reference ground line by switching the relay, the potential distribution of the entire substrate surface can be measured.

The potential distribution calculating means can determine the potential distribution of the measurement target part on the back surface of the substrate from the measured potentials of all the plurality of measurement terminals measured by a potentiometer. Based on the potential distribution information acquired by the distribution calculation means, it is possible to acquire energization state information such as the position of the energization part of the sample plate and the number of energization parts, so the state of the energization part of the replaced sample plate can be easily Can be evaluated. Since the exchange of the sample plate is easy, it is possible to easily acquire the energization state information for each sample.
In the evaluation, for example, a method similar to the measurement method disclosed in Patent Document 2 may be used.

  Here, when a metal sample plate is placed on a metal substrate, the state of the current-carrying part between the substrate and the sample plate is the uneven shape between the substrate surface and the sample plate surface, or the state of an insulating layer such as an oxide film. It depends on. Therefore, in order to better evaluate the difference in the state of the current-carrying portion due to the sample plate, it is desirable to make the substrate surface as smooth as possible to reduce the influence of the substrate. More specifically, the arithmetic average roughness Ra of the front surface of the substrate is preferably 0.1a to 1.6a. Moreover, since rust on the surface of the substrate greatly affects the state of the current-carrying portion, it is preferable to use a stainless steel plate that does not easily rust on the substrate.

  As described above, according to the present invention, a metal sample plate can be freely replaced, and the state of the current-carrying portion of the replaced sample plate can be easily evaluated.

It is a perspective view explaining the board | substrate part of one Embodiment of the conduction point evaluation apparatus of the metal plate surface which concerns on this invention. It is explanatory drawing of one Embodiment of the conduction point evaluation apparatus of the metal plate surface which concerns on this invention. It is a figure which shows the result of having investigated the state of the electricity supply part of a sample board (Example 1) using the conduction point evaluation apparatus of the metal plate surface which concerns on this invention. It is a figure which shows the result of having investigated the state of the electricity supply part of a sample board (Example 2) using the conduction point evaluation apparatus on the surface of a metal plate which concerns on this invention. It is a figure for demonstrating the state of the electromagnetic wave leakage from a metal housing | casing, The figure (a) is the top view, (b) is a front view.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate. FIG. 1 and FIG. 2 show an embodiment of an apparatus for evaluating a conduction point on the surface of a metal plate according to the present invention. This apparatus is for evaluating the state of the energization point of a metal sample plate.
As shown in FIG. 2, in this energization point evaluation device 10, a substrate 1 is fixed on a leg 2 made of an insulator. The substrate 1 is preferably a metal plate that is horizontally provided on the legs 2 and has a thickness of 1 mm or less and a smooth surface. Moreover, it is preferable that the surface 1f (refer FIG. 1) of the surface of the board | substrate 1 is 0.1a-1.6a in the arithmetic mean roughness Ra. Furthermore, since rust on the surface of the substrate 1 greatly affects the state of the current-carrying portion, it is preferable to use a stainless steel plate that does not easily generate rust for the substrate 1. In the present embodiment, the substrate 1 is a stainless steel plate (SUS304) having a plate thickness of 1.0 mm, and the arithmetic average roughness Ra of the front surface 1f of the substrate 1 is 0.5a.

  Here, the thickness of the substrate 1 is set to 1.0 mm or less because the state of the current-carrying portion between the substrate 1 and the sample plate S can be measured by the measurement method described in Patent Document 2 when the substrate 1 is thin. This is because the present inventor has found that it is limited to the above. That is, this measurement method is because the potential distribution on the front surface 1f of the substrate 1 (the surface in contact with the sample plate S) is substantially reflected on the back surface of the substrate 1 (to which the conducting wire is connected). In other words, if the thickness of the substrate 1 exceeds 1.0 mm, the potential distribution on the front surface 1 f of the substrate 1 is not reflected on the back surface of the substrate 1. For this reason, the state of the energization unit cannot be measured. However, even if the substrate 1 is made too thin, there is a problem that the strength is weakened. Therefore, in this embodiment, the thickness of the substrate is 1.0 mm.

  A sample plate S is placed on the front surface 1 f of the substrate 1. A plurality of measurement terminals 3 are connected to the back surface of the substrate 1. The plurality of measurement terminals 3 are preferably connected in a grid pattern at any one interval within a range of 3 to 10 mm over the entire measurement target portion of the sample plate S to be placed. In the example of the present embodiment, the conductive wire base end portion of the measurement terminal 3 is connected to the back surface of the portion where the dotted line (image) on the surface of the substrate 1 shown in FIG. 1 intersects by soldering. If the contact resistance between the measurement terminal 3 and the connection portion of the substrate 1 is large, accurate measurement cannot be performed. Therefore, it is preferable that the conductive wire is connected to the substrate 1 by soldering or spot welding or the like.

  In addition, the reason why the distance between the connection points of the measurement terminals 3 is 5 mm is that if the distance between the welds is about 3 mm or less, it is difficult to connect the conductors to the substrate, and the cost of connecting the conductors becomes very high. This is because if the interval exceeds 10 mm, the measurement accuracy is lowered and it is difficult to obtain a desired evaluation. The width of the dotted line (image) shown in FIG. 1 is 5 mm in both the X direction and the Y direction. That is, in this embodiment, the conductors are connected to the substrate in a grid pattern at intervals of 5 mm.

Here, when electromagnetic waves are transmitted through the gaps between the metal plates, the characteristics of the transmitted electromagnetic waves are as follows: a rectangular waveguide in which the distance between the current-carrying portions between the metal plates is the width and the distance between the metal plates is regarded as the height. It follows the characteristics of the transmitted TE10 wave (2010 IEEJ National Convention 1-159). In this case, when the distance between the current-carrying parts becomes 1/2 or less of the wavelength of the electromagnetic wave, the attenuation of the electromagnetic wave increases.
Assuming that the minimum distance between the current-carrying parts (or insulating parts) that can be measured is the resolution in this measurement, the resolution is equal to or greater than the distance between the conductors of the measurement terminals 3 connected to the substrate 1. When the distance between the conductors is 5 mm, the resolution is 5 mm or more. In this case, the wavelength of the leaked electromagnetic wave that can be evaluated is 10 mm or more, and the frequency of the electromagnetic wave is 30 GHz or less. In order to make the upper limit of the frequency region of leakage electromagnetic waves that can be evaluated as high as possible, the distance between the connection points of the conducting wires of the measurement terminal 3 was set to 5 mm.

The power source 4 can be energized by applying a voltage between the substrate 1 and the sample plate S placed on the front surface 1 f of the substrate 1.
The ends of the plurality of measurement terminals 3 are connected to the relay unit 5. The relay unit 5 has terminal switching means corresponding to the plurality of measurement terminals 3 inside, and switches the input to the potentiometer 6 for each of the plurality of measurement terminals 3. The relay unit 5 is connected so as to sequentially switch a plurality of measurement terminals 3 based on a command from the computer 9 and to input the current of one measurement terminal 3 to the potentiometer 6. The potentiometer 6 sequentially measures the potential with respect to one ground line G as a reference for each terminal 3 switched by the relay 5. The measured potential information for the ground line G for each terminal 3 is input to the computer 9.

  The computer 9 includes a potential distribution calculation unit 7 and an energization state information acquisition unit 8. These means 7 and energization state information acquisition means 8 are composed of the hardware of the computer 9 and a program of the energization point evaluation process, and the terminal 3 for the measured ground line G by executing the energization point evaluation process. Based on each potential information, desired energization state information is output.

  That is, the potential distribution calculating means 7 obtains the potential distribution of the measurement target portion on the back surface of the sample plate S from the measured potentials of all the plurality of measurement terminals 3 measured by the potentiometer 6. The potential distribution is obtained, for example, by representing the height of the acquired potential as a gray value of 256 gradations, and as a contour line of the potential difference as shown in the sample plate S (Examples 1 and 2) shown in FIGS. Is preferred. Then, the energization state information acquisition unit 8 acquires energization state information such as the position of the energization unit and the number of energization units of the sample plate S based on the potential distribution information acquired by the potential distribution calculation unit 7. ing. The acquired energization state information is configured to be output to an output device such as a display device (not shown) or a printer attached to the computer 9. Various methods can be set for obtaining the energization state information. For example, a portion exceeding the predetermined value (threshold value) in the 256 gradations is recognized as an energization unit, and the position (for example, As an embodiment, the position indicated by the arrows in FIGS. 3 and 4 can be output and displayed as an energization unit.

Next, the Example which evaluated the sample board S by the conduction point evaluation apparatus 10 of the structure mentioned above is demonstrated.
In this example, two types (Examples 1 and 2) of electroplated steel plates were used as sample plates S. When the sample plate S is placed on the front surface 1f of the substrate 1 described above, the resistance between the sample plate S and the substrate 1 measured by a tester is zero in any sample plate S, There was no difference.

  As shown in FIGS. 1 and 2, first, the sample plate S was placed on the substrate 1 and then a voltage was applied between the substrate 1 and the sample plate S by the power source 4 to pass a current of 10 A. . Next, when the computer 9 executes the energization point evaluation process, the relay unit 5 sequentially switches the plurality of measurement terminals 3 based on a command from the computer 9, and the potentiometer 6 sequentially changes the potential with respect to the ground line G for each terminal 3. The measured potential information for each terminal 3 is input to the computer 9. The computer 9 can easily visually recognize the potential distribution of the measurement target portion on the back surface of the substrate 1 from the measured potentials of the plurality of measurement terminals 3 measured by the potentiometer 6 by the potential distribution calculating means 7 and the energization state information acquiring means 8. It is obtained as potential distribution information expressed as contour lines of a significant potential difference. Then, based on the acquired potential distribution information, a portion exceeding a predetermined value (threshold) is acquired and acquired as energization state information such as the position of the energization portion and the number of energization portions of the sample plate S. A caution display by an arrow or the like is displayed on the screen corresponding to the energization state information together with the potential distribution information on the screen of the display device, and these are output to the printer.

  An example of the energization state information output to the printer as described above for each sample plate S (Example 1, Example 2) is shown in FIGS. 3 and 4, respectively. 3 and 4 show the potential distribution with respect to the ground line G measured on the back surface of the substrate 1 with contour lines, and the arrows in each figure are the acquired energization state information, and the potential is lower than the surroundings. This is a portion that is determined to be a current-carrying portion between the substrate 1 and the sample plate S.

As can be seen by comparing these figures, in the case of the sample plate S shown in FIG. 3 (Example 1), the three portions are energized portions, whereas the sample plate S shown in FIG. ), There are two energizing portions, and it can be seen that the energizing portion is more likely to occur in the sample plate S (Example 1) shown in FIG.
As described above, according to the energization point evaluation apparatus 10, the metal sample plate S can be freely replaced, and the state of the energized portion of the replaced sample plate S can be easily evaluated. In addition, the electric conduction point evaluation apparatus on the surface of the metal plate according to the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Leg 3 Measurement terminal 4 Power supply 5 Relay part 6 Potentiometer 7 Potential distribution calculation means 8 Current supply state information acquisition means 9 Computer 10 Current supply point evaluation apparatus S Sample board

Claims (3)

An energization point evaluation device for evaluating the state of the energization point of a metal sample plate,
A metal substrate having a thickness of 1 mm or less and a smooth surface provided on the legs made of an insulator, and any one interval within a range of 3 to 10 mm over the entire measurement target portion on the back surface of the substrate A plurality of measurement terminals connected in a grid pattern, one ground line, and a power source for applying a voltage between the substrate and the sample plate placed on the front surface of the substrate; A relay unit that switches connection for each terminal of the plurality of measurement terminals, a potentiometer that sequentially measures the potential with respect to the ground line for each terminal that is switched by the relay unit, and the potentiometer that is measured by the potentiometer Potential distribution calculation means for obtaining the potential distribution of the measurement target portion on the back surface of the substrate from the measurement potentials of all of the plurality of measurement terminals, and the energization state information of the sample plate based on the potential distribution information acquired by the potential distribution calculation means Energization point evaluation apparatus of the metal plate surface and having an energized state information acquiring means for acquiring.   2. The conduction point evaluation apparatus for a metal plate surface according to claim 1, wherein the front surface of the substrate has an arithmetic average roughness Ra of 0.1 a to 1.6 a.   The said board | substrate is a stainless steel plate, The conduction point evaluation apparatus of the metal plate surface of Claim 1 or 2 characterized by the above-mentioned.

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