JP4669030B2 - Electrostatic discharge measuring device - Google Patents

Description

  The present invention relates to an electrostatic discharge measuring apparatus that measures a discharge voltage received by a device from a charged body.

  When there is a system consisting only of a charged body and a device (or system), and the electrostatic charge of the charged body is discharged to the device, the discharge voltage corresponding to the discharge energy input to the device is greater than the electrostatic resistance of the device In addition, it is known that electrostatic damage (ESD: Electrostatic Discharge Hazard) occurs. The electrostatic resistance of a device varies from device to device, and its resistance value is determined by the manufacturer's nominal value. On the other hand, this discharge voltage may be a source of causing an electrostatic failure in the device depending on the device receiving the discharge energy, and is an indicator of whether or not the device has an electrostatic failure. Therefore, in the present specification, this discharge voltage is hereinafter referred to as an ESD hazard potential.

  Depending on the environment where the device is actually placed, there are various ways of generating static electricity damage. For example, in a factory where the device is manufactured, countermeasures against ESD hazards such as installing a static eliminator or wearing a wrist strap by an operator are required. Has been given. In order to efficiently implement such ESD hazard countermeasures, it is necessary to correctly recognize the behavior of environmental static electricity surrounding the device.

  Conventionally, a method of measuring the potential of a charged body, which is a source of static electricity, with an electrostatic measuring device such as a surface potential measuring device has been used. In this method, the electrostatic field potential is measured by bringing a static electricity meter closer to a charged body. This measured potential corresponds to the electrostatic energy that the charged body potentially has. However, a charged body rarely releases all electrostatic energy due to electric discharge, and usually releases a part thereof. Further, when the charged body and the device are not in contact, a part of the released energy is consumed in the air between the charged body and the device. That is, the discharge energy actually received by the device is smaller than the electrostatic energy of the charged body, and they are different. That is, the ESD hazard potential cannot be measured with a conventional static electricity meter.

Further, instead of the above-described method of measuring the potential of the charged body with an electrostatic meter, a method of measuring the charge amount of the charged body with an excess moving charge measuring device has been proposed (see Non-Patent Document 1, for example). This excessive dynamic charge measuring device can overcome the deficiencies of the conventional static electricity measuring device when the charged body is a metal, but causes various problems when the charged body is an insulator. A malfunction occurs.
Suzuki, “Electrostatic Discharge Measurement Technology and Prevention Measures for Advanced Electronic Devices”, M & E, Industrial Research Committee, April 2000, p. 210-215

  An object of the present invention is to provide an electrostatic discharge measuring apparatus that discriminates whether or not a discharge voltage received by a device is at a level that causes electrostatic failure in the device.

  The electrostatic discharge measuring apparatus according to the present invention is an electrostatic discharge measuring apparatus that measures the discharge voltage by simulating the discharge voltage received by the device when the static electricity of the charged body is discharged to the device. An electric circuit configured such that an impedance from an input electrode to an output ground electrode is equivalent to an input impedance of the device, and is connected to a signal line branched from the electric circuit, the electric circuit and the signal line A comparison circuit that compares the potential of the connection point with a predetermined voltage value that is a level that causes an electrostatic failure in the device, and outputs a signal when the potential of the connection point is equal to or higher than the predetermined voltage value; An informing means for informing the abnormality based on the output signal of the circuit is provided.

  According to the present invention, the electric circuit has an electrode and a ground electrode, and includes a resistor and the like between them. The impedance of the electric circuit is configured to be equivalent to the input impedance of the device to be subjected to static electricity countermeasures. Further, a signal line is branched from a discharge path connecting the electrode and the ground electrode. The comparison circuit is connected to the signal line, compares the potential at the connection point between the electric circuit and the signal line with a predetermined voltage value, and outputs a signal when the potential at the connection point is equal to or higher than the predetermined voltage value. . This predetermined voltage value is set in advance as a level that causes an electrostatic failure in the device. When the potential at the connection point is equal to or higher than a predetermined voltage value, the abnormality is notified by the notification means. Therefore, it is possible to discriminate whether or not the device is subjected to electrostatic discharge at a level that causes an electrostatic failure.

  In the electrostatic discharge measuring apparatus of the present invention, one or a plurality of device pseudo bodies having impedances that are matched in advance to the input impedance of a typical device are provided, and the device pseudo body corresponding to the device to be subjected to static electricity countermeasures is provided. Preferably, the electric circuit is selected.

  For example, a plurality of device pseudo bodies each having an electrode and a ground electrode are provided in advance. At this time, it is desirable to classify the capacitance and resistance that form the impedance of each device pseudo body by the diameter of the electrode and the resistance by the resistance between the electrode and the ground electrode. Then, a device pseudo body corresponding to the device to be subjected to static electricity countermeasures is selected to form an electric circuit. According to the above configuration, it is possible to measure the ESD hazard potential for many types of devices. In addition, it is possible to discriminate whether or not an electrostatic failure occurs for a plurality of devices.

(First form)
FIG. 1 is an external view of an electrostatic discharge measuring apparatus 1 (hereinafter simply referred to as a measuring apparatus 1) according to a first embodiment, and FIG. 2 is a configuration diagram showing a configuration of the measuring apparatus 1.

The measuring apparatus 1 includes a plurality of (for example, 12) spherical electrodes 3 _k (k = 1 to 12) that are exposed to the outside and can be changed in direction on the front surface of a box-shaped housing 2, and the upper surface of the housing 2. The display 4 is exposed and fixed to the outside, and the circuit unit 5 is housed inside the housing 2.

The diameter D of the electrode 3 _k is, for example, three types of D = 1 mm (k = 1 to 4), 5 mm (k = 5 to 8), 10 mm (k = 9 to 12), and four each are provided. ing. The display 4 displays the value of the discharge voltage (ESD hazard potential) received by the electrode 3 from the charged body. A power switch or the like (not shown) is attached to the outer surface of the housing 2.

The circuit unit 5 is connected to the electrode 3 _k and the display 4, and as shown in FIG. 2, 12 sets of discharge circuits 7 _k (k = 1 to 12) to which the electrode 3 _k is connected, A meter 8, a calculation unit 9, and an A / D conversion circuit 10 are provided. The meter 8 and the calculation unit 9 correspond to the measuring instrument of the present invention.

Each of the discharge circuits 7 _k includes a resistor 11 _k (resistance value R _1k ) and a voltage dividing circuit 12 _k (resistance value R _2k ) connected to the resistor 11 _k . The resistor 11 _k is connected to the electrode 3 _k , and the voltage dividing circuit 12 _k is connected to the ground electrode 13. The voltage dividing circuit 12 _k is constituted by a fixed resistor, for example.

Twelve paths from the electrode 3 _k to the ground electrode 13 through the discharge circuit 7 _k form a discharge path 14 _k (k = 1 to 12). Each of the discharge paths 14 _k corresponds to a device mimic of the present invention. In the impedance of the discharge path 14 _k , the electrostatic capacity is determined by the diameter D of the electrode, and the resistance is determined by the resistance R between the grounds, that is, the resistance between the electrode 3 _k and the ground electrode 13. There are four types of resistance R between grounds, for example, 1Ω, 100Ω, 1MΩ, and 100MΩ.

Specific combinations of the electrode diameter D of the discharge path 14 _k and the resistance R to ground R are (D, R) = (1 mm, 1Ω), (1 mm, 100Ω), (1 mm, 1 MΩ), (1 mm, 100 MΩ), (5 mm, 1Ω), (5 mm, 100Ω), (5 mm, 1 MΩ), (5 mm, 100 MΩ), (10 mm, 1Ω), (10 mm, 100Ω), (10 mm, 1 MΩ), (10 mm, 100 MΩ), The cases where k = 1 to 12 are shown.

The meter 8 is connected to the middle point of the resistor 11 _k of the discharging circuit 7 _k and the voltage dividing circuit 12 _{k by} a switch SW1 to SW12 so as to be switchable, and a voltage value V _ak (k = k =) generated between the voltage dividing circuit 12 _k. 1 to 12) are measured. The calculation unit 9 calculates a potential V _bk (k = 1 to 12) generated at the electrode 3 _k from the measurement value V _ak of the meter 8. The potential V _bk is expressed by the following equation (1). Further, the A / D conversion circuit 10 of the circuit unit 5 performs A / D conversion on the output signal of the calculation unit 9 and causes the display 4 to display it.

V _bk = V _ak * (R _1k + R _2k ) / R _2k (1)
Next, the operation of the measuring device 1 will be described. One of the electrodes 3 _k (or the discharge path 14 _k ) is selected according to the design value (nominal value of the manufacturer) of the input impedance of the device to be subjected to static electricity countermeasures. At this time, the selected electrode is extended on the front surface of the measuring device 1 and the other eleven electrodes are bent toward the upper surface of the measuring device 1. Hereinafter, the selected electrode is represented as an electrode 3, and similarly, a discharge circuit 7, a voltage dividing circuit 12, a discharge path 14, resistance values R ₁ and R ₂ , voltage values V _a and V _b , The description will be made with the subscript k omitted. The device is, for example, an integrated circuit such as an IC or LSI, or a component such as an MR head or a digital camera.

When measuring the ESD hazard potential received by a device from a charged body with this measuring apparatus 1, first, after turning on a power switch (not shown), the casing 2 is charged with the electrode 3 facing the charged body. Close to the body, the electrode 3 is brought into contact with the charged body. When the electrode 3 is brought into contact with the charged body, the charged body is discharged to the discharge path 14. That is, the ground electrode 13 is discharged via the electrode 3 and the discharge circuit 7, and a predetermined potential V _b is generated in the electrode 3 with respect to the ground electrode 13.

When the electrode 3 is brought into contact with the charged body, the meter 8 measures the voltage V _a generated between the voltage dividing circuits 12, and the calculation unit 9 converts the output signal of the meter 8 into the potential V _b generated at the electrode 3. . The potential V _b is expressed by the above formula (1) by the voltage V _a generated in the voltage dividing circuit 12 and the voltage dividing resistance values R ₁ and R ₂ . The output signal of the calculation unit 9 is A / D converted by the A / D conversion circuit 10, and the voltage value V _b is displayed on the display unit 4 as the ESD hazard potential V _b for the charged device. The ESD hazard potential V _b is measured.

  According to the first embodiment, the ESD hazard potential received by the device (or system) can be quantified. Further, it is possible to solve the problem that the measured potential value of the charged body by the conventional static electricity measuring device varies significantly depending on the measurement conditions and the manufacturer. In the above embodiment, the number of discharge paths 14 (the number of device pseudo bodies) is 12. However, the number is not limited to this and may be an arbitrary number.

Further, in the embodiment described above, steerable electrodes 3 _k is 12 arranged in the circuit portion 5, the electrode 3 _k is connected 12 pairs of the discharge circuit 7 _k were respectively provided from the electrodes 3 _k Although it has been described that the discharge path 14 _k that reaches the ground electrode 13 through the discharge circuit 7 _k is formed, the present invention is not limited to this. For example, a circuit unit including a meter 8, a calculation unit 9, and an A / D conversion circuit 10 is provided inside the housing, and a cartridge including one electrode and a discharge circuit 7 is detachable from the housing. You may comprise as follows. In this case, when the cartridge is mounted on the housing, the middle point of the resistor 11 and the voltage dividing circuit 12 constituting the discharging circuit 7 is connected to the meter 8, and the voltage dividing circuit 12 and the ground electrode 13 are connected. Is connected. A discharge path 14 is formed from the electrode 3 to the ground electrode 13 through the discharge circuit 7. Twelve types of cartridges are prepared, for example, and are selected according to a device to take measures against static electricity. According to this configuration, a compact electrostatic discharge measuring device can be realized.
(Second form)
FIG. 3 is an external view of an electrostatic discharge measuring device 21 (hereinafter simply referred to as a measuring device 21) according to an embodiment of the present invention, and FIG. 4 is a configuration diagram showing the configuration of the measuring device 21. In addition, the same reference number is given to the same structure as the measuring apparatus 1 of the 1st form mentioned above.

  Referring to FIG. 3, the measuring device 21 includes an electrode 3 that is exposed and fixed to the front portion of the box-shaped housing 2 and a circuit unit 25 that is housed inside the housing 2. The circuit unit 25 is connected to the electrode 3 and includes a discharge circuit 7 to which the electrode 3 is connected, a comparison circuit 26, an amplifier 27, and a notification unit 28 as shown in FIG.

The discharge circuit 7 includes a resistor 11 (resistance value R ₁ ) and a voltage dividing circuit 12 (resistance value R ₂ ) connected to the resistor 11. The resistor 11 is connected to the electrode 3, and the voltage dividing circuit 12 is connected to the ground electrode 13. The voltage dividing circuit 12 is composed of, for example, a fixed resistor. A discharge path 14 is formed from the electrode 3 to the ground electrode 13 through the discharge circuit 7.

Comparison circuit 26, compared with the resistor 11 of the discharging circuit 7 is connected via a signal line to the midpoint of the voltage divider circuit 12, the voltage value V _a with a predetermined voltage value V _C generated between the voltage dividing circuit 12 To do. Then, the signal S1 is output when the voltage value V _a is equal to or higher than the predetermined voltage value V _C. The amplifier 27 is composed of, for example, a bipolar transistor, amplifies the output signal S1 of the comparator 26, and supplies the amplified signal to the notification unit 28. The notification unit 28 is composed of, for example, a piezo buzzer made of a piezoelectric ceramic, and emits a buzzer sound according to an input signal.

Next, the operation of the measuring device 21 will be described. When the measuring device 21 discriminates whether or not the ESD hazard potential of the charged body causes an electrostatic failure in the device, a predetermined voltage value V _C is set in advance. The voltage value V _C is determined by the nominal value of the manufacturer of the device to be subjected to static electricity countermeasures, and is set at the manufacturing stage of the measuring device 21 dedicated to the device. When the device has a protection circuit for protecting the internal circuit from static electricity, the predetermined voltage value V _C is determined in consideration of the protection circuit.

  First, after a power switch (not shown) is turned on, the housing 2 is brought close to the charged body with the electrode 3 facing the charged body, and the electrode 3 is brought into contact with the charged body. Or it is made to approach from the direction which a device approaches a charged body on the manufacturing line etc. to the position which actually approaches like the environment where it is actually exposed to static electricity.

When the electrode 3 is brought into contact with or close to the charged body, the charged body is discharged to the ground electrode 13 through the electrode 3 and the discharge circuit 7, so that the electrode 3 has a predetermined potential V with respect to the ground electrode 13. _b occurs. In this case, the comparison circuit 26 compares the voltage V _a generated in the voltage dividing circuit 12 obtained by dividing the potential V _b generated in the electrode 3 with a predetermined voltage value V _C.

The comparison circuit 26 outputs a signal S1 when the voltage value V _a is equal to or higher than a predetermined voltage value V _C. The output signal S1 is amplified by the amplifier 27, and the notification unit 28 emits a buzzer sound. On the other hand, when the voltage value V _a is smaller than the predetermined voltage value V _C , the notification unit 28 does not emit a buzzer sound. Therefore, the buzzer can be sounded only when the device is discriminated when an electrostatic failure due to a charged body occurs.

Next, three specific configuration examples will be described.
(Configuration example 1)
When the measuring apparatus 21 is used in a production line of a factory that manufactures a digital camera, for example, the device is a part of the digital camera, and the charged body is, for example, a manufacturing apparatus or an operator disposed on the production line. It is. In this case, it is assumed that the static electricity discharge frequency is relatively low (about 100 MHz), such as HBM (Human Body Model) and MM (Machine Model). .

Many parts of digital cameras are known to have an electrostatic resistance of approximately 200 [V]. Therefore, static electricity in which the instantaneous value of the voltage input to the electrode 3 of the measuring device 21 reaches 200 [V] causes an electrostatic failure to the device. That is, the measuring apparatus 21 is configured to sound an alarm when the ESD hazard potential received by the device is 200 [V] or higher. More specifically, the resistance value R ₁ of the resistor 11 constituting the discharging circuit 7 of the circuit unit 25 is 5 [kΩ], the resistance value R ₂ of the voltage dividing circuit 12 is 500 [Ω], and a predetermined voltage value. V _C is set to 17 [V]. With the above configuration, it is possible to discriminate whether or not the discharge voltage of the charged body input to the electrode 3 of the measuring device 21 causes an electrostatic failure in the parts of the digital camera.
(Configuration example 2)
When the measuring apparatus 21 is used in a production line of a factory for producing a semiconductor integrated circuit such as an IC or LSI, the device is a semiconductor integrated circuit, and the charged body is disposed in the production line, for example. Manufacturing equipment. In this case, in general, there are many kinds of charged bodies to which the device is exposed, and there are various ways of approaching the devices to the charged body, and the fluctuation range of the discharge energy is larger than those of the other configuration examples 1 and 3. It can be said that it is a big case. Therefore, a plurality of types of measuring devices may be prepared according to the type of charged body. However, for the convenience of measurement, it is possible to cover with one measuring device.

In this case, it is known that if the instantaneous value of the voltage input to the electrode 3 of the measuring device 21 is static electricity of 50 [V] or less, no electrostatic failure is caused to the device. That is, the predetermined voltage value V _C of the measuring device 21 is determined so as to sound an alarm when the ESD hazard potential received by this device is 50 [V] or higher. More specifically, as shown in FIG. 5, the resistance value R ₁ of the resistor 11 constituting the discharging circuit 7 of the circuit unit 25 is set to 100 [Ω], and the voltage dividing circuit 12 is set to a capacitance of 100 [Ω]. pF] capacitor. With the above configuration, it is possible to discriminate whether or not the discharge voltage of the charged body input to the electrode 3 of the measuring device 21 causes an electrostatic failure in the semiconductor integrated circuit.
(Configuration example 3)
For example, when the measuring apparatus 21 is used in an assembly line of a factory that assembles a GMR head (Giant Magnet Resistive head), the device is a part of the GMR head, and the charged body is disposed in the assembly line, for example. Assembly equipment. It can be said that the electrostatic failure that occurs in the GMR head or the like is due to a steep spiked electrostatic phenomenon compared to the other structural examples 1 and 2.

In this case, it is known that if the instantaneous value of the voltage input to the electrode 3 of the measuring device 21 is static electricity of 5 [V] or less, no electrostatic failure is caused to the device. That is, the predetermined voltage value V _C of the measuring device 21 is determined so that an alarm is sounded when the ESD hazard potential received by this device is 5 [V] or more. More specifically, as shown in FIG. 6, the resistance value R ₁ of the resistor 11 constituting the discharging circuit 7 of the circuit section 25 is set to 2 [Ω], and the voltage dividing circuit 12 is constituted by a coil. With the above configuration, it is possible to discriminate whether or not the discharge voltage of the charged body input to the electrode 3 of the measuring device 21 causes an electrostatic failure in the GMR head.

  According to the embodiment, it is possible to measure whether or not the ESD hazard potential received by a device (or system) is at a level that causes an electrostatic failure in the device. Therefore, when the level is high, it is possible to take measures such as previously removing static electricity that may be exposed to the device in its manufacturing process or assembling process by, for example, a static eliminator. Conversely, it is possible to check whether the static electricity countermeasures applied to the device against environmental static electricity are appropriate.

In the above embodiment, the measurement apparatus 21 is configured by providing one discharge path 14 in conformity with the device and usage pattern. However, as in the first mode, the measurement apparatus 21 is provided with versatility, and a plurality of devices and usage patterns are preliminarily provided. A plurality of adapted discharge paths 14 and a plurality of predetermined voltage values V _C may be provided. In this case, a plurality of discharge paths 14 (device mimics) are provided, and the impedance of each discharge path is configured to match the input impedance of a typical device. Note that the term “match” includes not only exactly the same but also a range that is substantially the same. More specifically, the capacitance forming the discharge path 14 is classified by the diameter of the electrode 3, and the resistance is classified by the resistance between grounds (resistance between the electrode and the grounding electrode). Then, the user selects an optimal device pseudo body (discharge path 14) according to the device and usage pattern, and causes the electrodes 3 forming the selected discharge path 14 to discharge static electricity from the charged body.

  In order to provide versatility, for example, a circuit unit including a comparison circuit 26, an amplifier 27, and an informing unit 28 is provided inside the housing, and a cartridge including one electrode and the discharging circuit 7 is provided in the housing. It may be configured to be detachable from the body. In this case, when the cartridge is mounted on the housing, the middle point of the resistor 11 and the voltage dividing circuit 12 constituting the discharging circuit 7 is connected to the comparison circuit 26, and the voltage dividing circuit 12 and the ground electrode are connected. 13 is connected. A discharge path 14 is formed from the electrode 3 to the ground electrode 13 through the discharge circuit 7. In this case, a plurality of cartridges are prepared and are selected according to the device to take measures against static electricity.

In the above embodiment, the notification unit 28, the voltage V _a generated voltage dividing circuit 12, it is assumed that the buzzer when the above predetermined voltage value V _C, the voltage V _a of a predetermined provided display lamps The display lamp may be turned on when the voltage value is equal to or higher than the voltage value V _C , or the buzzer and the display lamp may be used together for notification.

The external view of the electrostatic discharge measuring apparatus of a 1st form. The block diagram of the electrostatic discharge measuring apparatus. The external view of the electrostatic discharge measuring apparatus of embodiment of this invention. The block diagram of the electrostatic discharge measuring apparatus of embodiment. The block diagram of the electrostatic discharge measuring device for demonstrating the example 2 of a structure. The block diagram of the electrostatic discharge measuring device for demonstrating the structural example 3. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,21 ... Electrostatic discharge measuring device, 2 ... Housing, 3 ... Electrode, 4 ... Display, 5,25 ... Circuit part, 7 ... Discharge circuit, .. Meter, 9... Calculation unit, 10... A / D conversion circuit, 11... Resistor, 12. 26... Comparison circuit, 27... Amplifier, 28.

Claims (2)

An electrostatic discharge measuring apparatus that measures the discharge voltage by artificially reproducing the discharge voltage received by the device when static electricity of the charged body is discharged to the device,
An electrical circuit configured such that the impedance from the electrode to which electrostatic discharge is input to the output ground electrode is equivalent to the input impedance of the device;
A potential of a connection point between the electrical circuit and the signal line is connected to a signal line branched from the electrical circuit, and a predetermined voltage value that is a level causing an electrostatic failure in the device is compared. A comparison circuit that outputs a signal when the potential is equal to or higher than the predetermined voltage value;
An electrostatic discharge measuring apparatus comprising: an informing means for informing an abnormality based on an output signal of the comparison circuit.   One or a plurality of device mimics having an impedance previously matched with the input impedance of a typical device are provided, and the device mimics corresponding to the device to be subjected to static electricity countermeasures are selected to form the electric circuit. The electrostatic discharge measuring apparatus according to claim 1, wherein

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