JP2017075860A - Resistance measuring device and inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately measure a resistance value of a measuring object while suppressing an excessive voltage rise in a high potential electrode of a current output unit.SOLUTION: A resistance measuring device comprises: a current output unit 2 which outputs measurement current I to a measuring object 61; a voltage measuring unit 3 which measures voltage V of the measuring object 61; a processing unit 6 which performs resistance measuring processing for measuring a resistance value R of the measuring object 61 on the basis of a current value Ia of the measurement current I and a voltage value Va of the voltage V; a protection circuit 4 including a Zener diode, connected between high potential electrodes Hc and Hp, and for suppressing a rise in voltage of the high potential electrode Hc by passing a part of the measurement current I from the high potential electrode Hc to the high potential electrode Hp as bypass current Iby when voltage of the high potential voltage Hp with respect to the high potential voltage Hc rises beyond Zener voltage of the Zener diode; and a current detecting unit 5 which detects the bypass current Iby. The processing unit 6 performs error processing when a current value Ib of the detected bypass current Iby becomes not less than a threshold current value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a resistance measuring apparatus and an inspection apparatus that have a pair of current supply terminals and a pair of voltage detection terminals connected to a measurement object and measure the resistance value of the measurement object by a four-terminal method.

  As an example of this type of resistance measuring device, several resistance measuring devices disclosed in Patent Document 1 below are known. Among these, the resistance measuring device disclosed as the background art has a basic configuration of a resistance measuring device that measures a resistance value of a measurement object by a four-terminal method. The resistance measuring device 51 will be described with reference to FIG. The resistance measuring device 51 is connected to a pair of current supply terminals (high potential electrode Hc, low potential electrode Lc), and a current output unit 2 capable of outputting a measurement current (for example, DC constant current) between the current supply terminals. And a voltage measuring unit 3 connected to a pair of voltage detection terminals (high potential electrode Hp, low potential electrode Lp) and capable of measuring a voltage generated between the voltage detection terminals.

  In this resistance measuring device 51, as an example, the high potential electrode Hc, which is a current supply terminal, is measured in a state where the low potential electrode Lc, which is a current supply terminal, is defined as a reference potential (the potential of the ground G) in the device. One terminal 62a of 61 is contacted (probed), and the low potential electrode Lc which is a current supply terminal is contacted (probed) to the other terminal 62b of the measuring object 61. Further, the high potential electrode Hp that is a voltage detection terminal is brought into contact (probing) with one terminal 62 a of the measurement object 61, and the low potential electrode Lp that is a voltage detection terminal is brought into contact with the other terminal 62 b of the measurement object 61. (Probed). Further, in the resistance measuring device 51, in this probing state, the current output unit 2 outputs the measurement current I, and the voltage measurement unit 3 generates the voltage between both ends of the measurement object 61 caused by the measurement current I flowing. The voltage value Va of V is measured. Therefore, according to the resistance measuring device 51, by providing a calculation unit (not shown) in addition to the current output unit 2 and the voltage measurement unit 3, the calculation unit is configured so that the current value Ia of the measurement current I and the voltage measurement unit 3 Based on the measured voltage value Va, the resistance value R (= Va / Ia) of the measuring object 61 can be calculated (measured).

JP 2010-2199 A (second page, FIG. 2)

  By the way, when the resistance measuring device 51 measures the resistance value R of the new measuring object 61 while repeating the operation of moving and probing the high potential electrodes Hc, Hp to the new measuring object 61, the measurement current I In this supply state, the contact state between the high potential electrode Hc and the one terminal 62a of the measuring object 61 becomes unstable, resulting in the contact resistance between the high potential electrode Hc and the one terminal 62a. The resistance value of R1 may change. At this time, if the current output unit 2 is configured as a constant current source, the current output unit 2 operates so as to maintain the current value of the measurement current constant even when the resistance value of the contact resistance R1 changes. For this reason, the current output unit 2 reduces the voltage of the high potential electrode Hc when the resistance value of the contact resistance R1 decreases, and supplies the voltage of the high potential electrode Hc when the resistance value of the contact resistance R1 increases. The upper limit of the open upper limit voltage of 2 is increased.

  However, even if the voltage is equal to or lower than the open upper limit voltage, if the voltage of the high potential electrode Hc becomes too high, an electrical stress is applied to the contact portion of the high potential electrode Hc in one terminal 62a. May leave traces. In order to avoid the occurrence of this problem, the applicant of the present application, as shown by a broken line in FIG. 2, sets the protection circuit 4 for preventing the voltage of the high potential electrode Hc from becoming too high. The structure arrange | positioned between the electric potential poles Hp is employ | adopted.

  The protection circuit 4 shifts from the off state to the on state when the voltage on the high potential electrode Hc side becomes equal to or higher than a predetermined voltage, and causes a current to flow from the high potential electrode Hc side to the high potential electrode Hp side. (Bypassing the current), the current output unit 2 has a function of lowering the voltage of the high potential electrode Hc. As shown in FIG. 2, the protection circuit 4 can be configured, for example, by connecting two Zener diodes in series with opposite polarities. The protection circuit 4 having this configuration shifts from the off state to the on state when the voltage difference between the high potential electrodes Hc and Hp exceeds the Zener voltage of the Zener diode, and from the high potential electrode Hc side to the high potential electrode Hp. By flowing the current to the side, the voltage of the high potential electrode Hc can be suppressed to the Zener voltage, and as a result, electrical stress is not applied to the one terminal 62a.

  However, the resistance measuring device 51 provided with the protection circuit 4 has the following problems to be improved. That is, in this resistance measuring device 51, when the protection circuit 4 is activated, a current flows from the high potential electrode Hc side to the high potential electrode Hp side, so that the contact between the high potential electrode Hp and the one terminal 62a. The voltage drop across the resistor R2 increases by this current. For this reason, when the voltage drop at the contact resistance R2 due to this current exceeds a predetermined voltage value, a measurement error included in the voltage value Va of the voltage V between both ends measured by the voltage measuring unit 3 is allowed. In some cases, the resistance value R measured in this state also includes an unacceptable measurement error. Therefore, the resistance measuring device 51 sometimes measures the resistance value R measured in this state as the final resistance value R of the measuring object 61, and there is a problem that this point should be improved. Yes.

  The present invention has been made in order to improve such a problem, and a resistance measuring device and an inspection capable of accurately measuring a resistance value of a measurement target while suppressing an excessive voltage increase of a high potential electrode of a current output unit. The main purpose is to provide a device.

  In order to achieve the above object, the resistance measuring device according to claim 1 includes a current output unit that outputs a measurement current to a measurement object via a pair of current supply terminals, and both ends generated in the measurement object when the measurement current flows. A voltage measurement unit that measures an inter-voltage via a pair of voltage detection terminals, and a resistance measurement that measures the resistance value of the measurement object by a four-terminal method based on the current value of the measurement current and the voltage value of the voltage between both ends A resistance measuring device including a processing unit that performs processing, including a Zener diode, and a high-potential side supply terminal of the pair of current supply terminals and the pair of voltage detection terminals Connected to the high potential side detection terminal, and when the voltage of the high potential side supply terminal with respect to the high potential side detection terminal rises above the Zener voltage of the Zener diode, A protection circuit that suppresses a rise in the voltage of the high potential side supply terminal by causing a part of the measurement current to flow as a bypass current from the high potential side supply terminal to the high potential side detection terminal, and a current that detects the bypass current A detection unit, and the processing unit executes a predetermined error process when a current value of the bypass current detected by the current detection unit becomes equal to or greater than a predetermined threshold current value.

  The resistance measurement device according to claim 2 is the resistance measurement device according to claim 1, wherein the processing unit again executes the resistance measurement processing in the error processing.

  The resistance measuring device according to claim 3 is the resistance measuring device according to claim 1 or 2, wherein the processing unit indicates that the current value of the bypass current is equal to or greater than the threshold current value in the error processing. Output.

  The resistance measurement device according to claim 4 is the resistance measurement device according to any one of claims 1 to 3, wherein the voltage value between the pair of voltage detection terminals measured by the voltage measurement unit and the current output unit. A voltage monitoring unit that compares a reference voltage value defined in advance below the open upper limit voltage and outputs a voltage limit signal when the voltage value between the pair of voltage detection terminals exceeds the reference voltage value. And the current output unit has a voltage limiting function for limiting the voltage between the pair of current supply terminals to a limit voltage that is defined in advance to a voltage value less than the open upper limit voltage when the voltage limit signal is input. ing.

  The inspection device according to claim 5 includes the resistance measurement device according to any one of claims 1 to 4, wherein the processing unit is executed when the current value of the bypass current is less than the threshold current value. The measurement object is inspected based on the resistance value measured in the resistance measurement process.

  In the resistance measuring device according to claim 1 and the inspection device according to claim 5, between the high potential side supply terminal of the pair of current supply terminals and the high potential side detection terminal of the pair of voltage detection terminals. And a current detector that detects a bypass current flowing in the protection circuit connected to the processor, and the processor executes error processing when the current value of the bypass current becomes equal to or greater than the threshold current value. Specifically, in the error process, for example, the resistance measurement process is executed again.

  Therefore, according to the resistance measurement device and the inspection device, when the resistance measurement process is performed again while suppressing an excessive voltage increase at the high potential electrode of the current output unit, a bypass current having a current value equal to or greater than the threshold current value is obtained. When the current does not flow, an accurate resistance value can be measured. In error processing, for example, the resistance measurement process is executed again in a state where display of the inaccurate resistance value measured in the resistance measurement process executed when the current value of the bypass current is equal to or greater than the threshold current value is stopped. In this case, an accurate resistance value can be displayed by avoiding an inaccurate display of the resistance value. Further, according to this inspection apparatus, it is possible to inspect the measurement object, and thus the circuit board, with high accuracy based on the measured accurate resistance value.

  According to the resistance measuring device according to claim 3 and the inspection device according to claim 5, since the fact that the current value of the bypass current is equal to or greater than the threshold current value is output, this is indicated by the resistance measuring device and the inspection device. The user can be notified.

  According to the resistance measuring device according to claim 4 and the inspection device according to claim 5, when the voltage value of the voltage between the pair of voltage detection terminals exceeds the reference voltage value, the voltage monitoring unit outputs the voltage limiting signal. In addition to outputting, the current output unit inputs this voltage limit signal, and the voltage between the pair of current supply terminals is limited to the limit voltage, so that the protection circuit is operating (the bypass current is flowing) Even when the contact state between the high potential side detection terminal and the measurement target terminal becomes unstable, the voltage applied to the measurement target is less than the limit voltage (for example, the upper limit that can be applied to the measurement target). Or less), and as a result, application of electrical stress to the high potential side detection terminal and the measurement target terminal can be avoided.

1 is a configuration diagram of a resistance measuring device 1. FIG. It is a block diagram of the resistance measuring apparatus 51.

  Hereinafter, embodiments of a resistance measuring device and an inspection device will be described with reference to the accompanying drawings.

  First, the configuration of the resistance measuring apparatus 1 as the resistance measuring apparatus shown in FIG. 1 will be described.

  The resistance measuring apparatus 1 includes a current output unit 2, a voltage measurement unit 3, a protection circuit 4, a current detection unit 5, a processing unit 6, an output unit 7, a voltage monitoring unit 8, a pair of current supply terminals (a high potential electrode Hc and a low potential electrode). Potential electrode Lc) and a pair of voltage detection terminals (high potential electrode Hp and low potential electrode Lp), and the resistance value R of the measuring object 61 (a mounted component such as a through-hole or a resistance element of a circuit board) can be measured. It is configured.

  The current output unit 2 includes a constant current source (DC constant current source) as an example, generates a measurement current I that is a DC constant current (current value Ia is known), and a pair of output terminals (not shown). Output from. In this example, for example, one output terminal (high potential side terminal) of the pair of output terminals is one current supply terminal (high potential side) configured as a movable probe of the pair of current supply terminals. A high-potential pole Hc) as a supply terminal via a wiring cable, and the other output terminal (low-potential side terminal) of the pair of output terminals is a fixed probe of the pair of current supply terminals. The other configured current supply terminal (low potential electrode Lc) is connected via a wiring cable. The low potential electrode Lc is defined as the reference potential (the potential of the ground G) in the resistance measuring device 1. With this configuration, the current output unit 2 is configured to be able to output the generated measurement current I from a pair of current supply terminals (the high potential electrode Hc and the low potential electrode Lc).

  Further, the current output unit 2 configured by a DC constant current source changes the output voltage according to the resistance value between the pair of current supply terminals (the high potential electrode Hc and the low potential electrode Lc) (the resistance value is low). The output voltage is sometimes lowered, and when the resistance value is high, the output voltage is raised) to maintain the current value of the measurement current I constant. Therefore, for example, when the resistance value is extremely large, such as when the pair of current supply terminals is in an open state, the output voltage rises to the open upper limit voltage of the DC constant current source as the upper limit voltage. To do.

  In addition, when the voltage output signal (described later) is input from the voltage monitoring unit 8, the current output unit 2 preliminarily defines the output voltage (voltage between the pair of current supply terminals) to a voltage value less than the open upper limit voltage. It has a voltage limiting function to limit to the limited voltage. The limit voltage is defined, for example, as a voltage value less than the upper limit voltage value that can be applied to the measurement object 61. When the output of the voltage limiting signal Sc from the voltage monitoring unit 8 (input of the voltage limiting signal Sc) is stopped, the current output unit 2 stops this voltage limiting function and outputs the output voltage (a pair of current supply terminals). The voltage shifts to a state where the voltage can be increased to the open upper limit voltage.

  The voltage measuring unit 3 is, for example, one voltage detection terminal in which one detection terminal (high potential side terminal) of a pair of detection terminals (not shown) is configured as a movable probe of the pair of voltage detection terminals. (High potential electrode Hp as a high potential side detection terminal) is connected via a wiring cable, and the other detection terminal (low potential side terminal) of the pair of detection terminals is a fixed type of the pair of voltage detection terminals. Is connected to the other voltage detection terminal (low potential electrode Lp) configured as a probe via a wiring cable. With this configuration, the voltage measuring unit 3 measures the voltage value Va of the voltage V generated between the pair of voltage detection terminals (the high potential electrode Hp and the low potential electrode Lp) and outputs the voltage value Va to the processing unit 6. The voltage measuring unit 3 receives a voltage V between a pair of voltage detection terminals and outputs a terminal-to-terminal detection voltage Vd having the same voltage value as the voltage value Va of the voltage V (gain is not shown). The inter-terminal detection voltage Vd is output to the voltage monitoring unit 8.

  The protection circuit 4 is connected between the high potential electrode Hc and the high potential electrode Hp, and suppresses an excessive increase in the voltage on the high potential electrode Hc side. That is, the protection circuit 4 suppresses the voltage on the high potential electrode Hc side from becoming an excessively high voltage. Specifically, the protection circuit 4 includes a Zener diode, and when the voltage of the high potential electrode Hc with respect to the high potential electrode Hp exceeds the Zener voltage of the Zener diode, a part of the measurement current I is included. Is caused to flow as a bypass current Iby from the high potential electrode Hc side to the high potential electrode Hp side, thereby suppressing an increase in the voltage of the high potential electrode Hc (the output voltage of the current output unit 2). The Zener voltage is defined to be lower than the open upper limit voltage of the current output unit 2 (for example, about 30% to 60% of the open upper limit voltage).

  In this example, as an example, the protection circuit 4 is configured by connecting two Zener diodes (for example, Zener diodes having the same Zener voltage) in series with opposite polarities. Further, in the protection circuit 4 of this example, the configuration in which the anode terminals of the two Zener diodes are connected to each other is adopted, but the configuration in which the cathode terminals are connected to each other can also be adopted. In the configuration in which the two Zener diodes are connected in series with opposite polarities, the protection circuit 4 actually has the voltage of the high potential electrode Hc with respect to the high potential electrode Hp changed to the Zener voltage of the Zener diode in the forward direction of the Zener diode. When the voltage rises above the applied voltage, it operates so that a part of the measurement current I flows as a bypass current Iby from the high potential electrode Hc side to the high potential electrode Hp side. For simplicity, the forward voltage of the Zener diode is ignored.

  The current detection unit 5 is composed of an ammeter and is connected between the connection point P1 of the protection circuit 4 and the high potential electrode Hp in the wiring cable that connects one detection terminal of the voltage measurement unit 3 and the high potential electrode Hp. The bypass current Iby flowing through the protection circuit 4 is detected, and a detection signal S1 whose voltage value changes in proportion to the current value Ib of the bypass current Iby is output. Although not shown, the current detection unit 5 may be connected (arranged) between the high potential electrode Hc and the high potential electrode Hp in a state of being connected in series with the protection circuit 4. Good.

  For example, the processing unit 6 is configured by an A / D converter and a computer, for example, and based on the current value Ia of the measurement current I and the voltage value Va of the voltage V measured by the voltage measurement unit 3. A resistance measurement process for calculating (measuring) the resistance value R of the measuring object 61 connected between the voltage detection terminals (the high potential electrode Hp and the low potential electrode Lp) is executed. The processing unit 6 detects the current value Ib of the bypass current Iby flowing through the protection circuit 4 based on the voltage value of the detection signal S1 output from the current detection unit 5, and also detects the current value Ib of the detected bypass current Iby. Is determined to determine whether or not is equal to or greater than a predetermined threshold current value (for example, 10 mA as an example within a range of about several mA to several tens of mA). In addition, when the processing unit 6 determines that the current value Ib of the bypass current Iby is greater than or equal to the threshold current value in the determination process, the processing unit 6 performs error processing described later. In addition, the processing unit 6 executes output processing for outputting the resistance value R calculated in the resistance measurement processing, the determination result in the determination processing, and the like to the output unit 7.

  The output unit 7 is configured by a display device such as a liquid crystal display device as an example, and displays the resistance value R and the determination result output from the processing unit 6 on the screen.

  As an example, the voltage monitoring unit 8 includes a reference voltage output circuit 8a and a comparison circuit 8b. The reference voltage output circuit 8a is composed of, for example, a power supply device that can change the output voltage, and a reference voltage Vr of a preset reference voltage value Vr (the same sign as the reference voltage value Vr for easy understanding of the invention). Is used). The comparison circuit 8b is configured by a comparator, for example, and compares the voltage value of the inter-terminal detection voltage Vd output from the voltage measurement unit 3 with the reference voltage value Vr, while the voltage value of the inter-terminal detection voltage Vd is When the voltage value exceeds the reference voltage value Vr, the voltage limit signal Sc is output. When the voltage value of the inter-terminal detection voltage Vd is equal to or lower than the reference voltage value Vr, the output of the voltage limit signal Sc is stopped. The reference voltage value Vr is defined as an arbitrary voltage value less than the open upper limit voltage of the current output unit 2 and less than the upper limit voltage value that can be applied to the measurement target 61. With this configuration, the voltage monitoring unit 8 outputs the voltage limit signal Sc when the voltage value between the pair of voltage detection terminals measured by the voltage measurement unit 3 exceeds the reference voltage value Vr, and the pair of voltage When the voltage value between the detection terminals is equal to or lower than the reference voltage value Vr, the output of the voltage limiting signal Sc is stopped. When the voltage measurement unit 3 does not output the inter-terminal detection voltage Vd, the voltage monitoring unit 8 directly outputs the voltage value Va between the pair of voltage detection terminals instead of the configuration in which the inter-terminal detection voltage Vd is input. A configuration for detection can also be adopted.

  Next, the operation of the resistance measuring apparatus 1 will be described.

  In the resistance measuring apparatus 1, the other current supply terminal (low potential electrode Lc) and the other voltage detection terminal (low potential electrode Lp) are fixed probes. Therefore, as shown in FIG. It is assumed that the other terminal 62b (the lower terminal in the figure) is previously probed in such a small state that the resistance value of the contact resistance can be ignored.

  In this state, in the resistance measuring apparatus 1, one current supply terminal (high potential pole Hc) and one voltage detection terminal (high potential pole Hp) configured as a movable probe have a moving mechanism (not shown) or the like. By this, it is moved to one terminal 62a (the upper terminal in the figure) of the measuring object 61 and is probed to this one terminal 62a. The current detection unit 5 continuously detects the bypass current Iby flowing in the protection circuit 4 (that is, the current flowing between the high potential electrode Hc and the high potential electrode Hp), and outputs the detection signal S1 to the processing unit 6. Is output.

  The current output unit 2 measures the current measured between the high potential electrode Hc and the low potential electrode Lc in accordance with the timing (probing completion timing) when the probing of the high potential electrode Hc and the high potential electrode Hp to the one terminal 62a is completed. I is output only during a constant current output period (that is, in a pulse form). The voltage measuring unit 3 measures and measures the voltage value Va of the voltage V generated between the high potential electrode Hp and the low potential electrode Lp in the current output period in which the current output unit 2 outputs the measurement current I. The obtained voltage value Va is output to the processing unit 6. Further, the voltage measuring unit 3 outputs the inter-terminal detection voltage Vd having the same voltage value as the measured voltage value Va to the voltage monitoring unit 8. The voltage monitoring unit 8 compares the voltage value of the inter-terminal detection voltage Vd with the reference voltage value Vr.

  The processing unit 6 performs the determination process while inputting the detection signal S1 output from the current detection unit 5 in the current output period. In this determination process, the processing unit 6 samples the detection signal S1 at a sampling period sufficiently shorter than the current output period, and displays voltage data indicating the instantaneous value (data indicating the instantaneous value of the current value Ia of the bypass current Iby). But also). The processing unit 6 compares the current value Ib of the bypass current Iby indicated by the voltage data with the threshold current value, and determines whether or not the current value Ib (peak value) is equal to or greater than the threshold current value. To do.

  In addition, the processing unit 6 performs a resistance value measurement process in parallel with the determination process in the current output period. In this resistance value measurement process, the processing unit 6 is configured to generate a pair of voltage detection terminals (a high potential electrode Hp and a low potential) based on the voltage value Va output from the voltage measurement unit 3 and the current value Ia of the measurement current I. A resistance value R (= Va / Ia) between the potential electrodes Lp) is calculated (measured).

  When the processing unit 6 determines that the current value Ib is not equal to or greater than the threshold current value in the determination process after the end of the current output period, the processing unit 6 uses the resistance value R calculated in the resistance value measurement process as the measurement target 61. Measure (specify) as the final resistance value.

  Here, when the current value Ib of the bypass current Iby does not exceed the threshold current value in the current output period (that is, when the bypass current Iby hardly flows), the high potential electrode Hc with respect to the high potential electrode Hp. The voltage did not exceed the Zener voltage of the Zener diode constituting the protection circuit 4 (that is, the output voltage of the current output unit 2 was always lower than the open upper limit voltage of the current output unit 2). Become. This is because, in the current output period, the contact state between the high potential electrode Hc and one terminal 62a of the measurement object 61 was stable with the resistance value of the contact resistance R1 being sufficiently small, This indicates that the voltage value of the output voltage of the current output unit 2 is maintained below the upper limit voltage value that can be applied to the measurement target 61 due to the above. In addition, the fact that the bypass current Iby hardly flows during the current output period means that the voltage measuring unit 3 causes the bypass current Iby to be generated in the contact resistance R2 between the high potential electrode Hp and the one terminal 62a during the current output period. The voltage value Va of the voltage V (that is, the voltage value of the voltage between both ends of the measurement target 61) can be accurately measured without being affected by the voltage drop that occurs when flowing. Therefore, the processing unit 6 measures the resistance value R calculated in the resistance value measurement process as the final resistance value of the measurement object 61 as described above.

  The processing unit 6 executes an output process and outputs the resistance value R to the output unit 7. The output unit 7 displays this resistance value R on the screen. Thereafter, in the resistance measuring apparatus 1, one current supply terminal (high potential pole Hc) and one voltage detection terminal (high potential pole Hp) configured as a movable probe are connected to each other by a moving mechanism (not shown). The probe is moved to one terminal of the measurement object and probing, and the processing unit 6 starts measuring the resistance value of the measurement object.

  On the other hand, when the processing unit 6 determines that the current value Ib is greater than or equal to the threshold current value in the determination process after the end of the current output period, the processing unit 6 executes a predetermined error process. In this error process, the processing unit 6 does not measure (specify) the resistance value R calculated in the resistance value measurement process as the final resistance value of the measurement object 61, that is, the resistance value R is calculated. Without outputting to the output unit 7, an output process for outputting information indicating that the current value Ib of the bypass current Iby is equal to or greater than the threshold current value to the output unit 7 is executed. The output unit 7 displays characters, symbols, and the like indicating that the current value Ib is equal to or greater than the threshold current value on the screen.

  Here, when the current value Ib of the bypass current Iby becomes equal to or greater than the threshold current value in the current output period (that is, when the bypass current Iby flows), the high potential electrode Hc and one terminal 62a of the measurement target 61 are used. The contact state between the two becomes unstable (for example, chattering has occurred), so that the resistance value of the contact resistance R1 between the two changes in an increasing direction, and as a result, the current output unit As a result of the rise of the output voltage of 2 and the voltage of the high potential electrode Hc with respect to the high potential electrode Hp exceeding the Zener voltage of the Zener diode constituting the protection circuit 4, the protection circuit 4 is activated and the high potential This means that the voltage of the high potential electrode Hc with respect to the electrode Hp is clamped (maintained) to the Zener voltage.

  In the resistance measuring device 1, the protection circuit 4 operates in this manner, and thus the output voltage of the current output unit 2 rises above the zener voltage (and thus higher than the open upper limit voltage of the current output unit 2). This can prevent a situation in which the voltage of the high potential electrode Hc is excessively increased (that is, becomes too high), and the electrical connection to the contact portion of the high potential electrode Hc at one terminal 62a is caused. The application of stress (and the occurrence of defects such as traces due to the application of electrical stress) can be avoided.

  In this case, the fact that the bypass current Iby flows during the current output period means that the voltage measuring unit 3 causes the bypass current Iby to flow through the contact resistance R2 between the high potential electrode Hp and the one terminal 62a during the current output period. That is, the voltage value Va of the voltage V is measured under the influence of the voltage drop that occurs during the measurement (that is, the voltage value of the voltage across the measurement object 61 cannot be measured accurately). . Therefore, the processing unit 6 does not measure (specify) the resistance value R calculated in the resistance value measurement process as the final resistance value of the measurement target 61 as described above. Therefore, the processing unit 6 does not output the resistance value R to the output unit 7. In the resistance measuring apparatus 1, the resistance value R calculated based on the voltage value Va of the voltage V that is highly likely to be inaccurate (the resistance value R is also likely to be inaccurate). ) Is avoided as the final resistance value of the measuring object 61.

  Further, in this error processing, the processing unit 6 causes the current output unit 2 to output the measurement current I again during the current output period (period having the same length as the previous current output period), and the voltage measurement unit 3 In this new current output period, the voltage value Va of the voltage V is measured. In addition, in the new current output period, the processing unit 6 again executes the determination process and the resistance measurement process in parallel. Therefore, when the current value Ib of the bypass current Iby does not exceed the threshold current value in this new current output period (that is, when the bypass current Iby hardly flows), the resistance measuring device 1 The processing unit 6 was measured in this current output period in which the contact state between the high-potential electrode Hc and one terminal 62a of the measurement object 61 is stable with a sufficiently small resistance value of the contact resistance R1. An accurate resistance value R is measured (calculated) based on the voltage value Va of the voltage V (that is, the voltage value of the voltage across the measuring object 61 that is accurately measured), and the final resistance of the measuring object 61 is measured. It can be measured as a value.

  In the state where the bypass current Iby flows as described above, when the contact state between the high potential electrode Hp and one terminal 62a of the measurement target 61 becomes unstable (for example, chattering has occurred). ), The resistance value of the contact resistance R2 between the high potential electrode Hp and the one terminal 62a of the measuring object 61 changes in the increasing direction, and as a result, a pair of voltage detection terminals (the high potential electrode Hp and There may be a case where an attempt is made to shift to an undesirable state in which the voltage between the low potential electrodes Lp) increases. In such a case, in the resistance measuring apparatus 1, the voltage monitoring unit 8 compares the voltage value of the inter-terminal detection voltage Vd with the reference voltage value Vr, and the voltage value of the inter-terminal detection voltage Vd is the reference voltage. When the value Vr is exceeded (that is, when the voltage value Va of the voltage V between the pair of voltage detection terminals exceeds the reference voltage value Vr), the voltage limiting signal Sc is output. Further, when the voltage limiting signal Sc is input from the voltage monitoring unit 8, the current output unit 2 operates the voltage limiting function to limit the output voltage to the limiting voltage. Therefore, in this resistance measuring apparatus 1, even when the contact state between the high potential electrode Hp and the one terminal 62a becomes unstable in a state where the bypass current Iby flows, the resistance measuring device 1 is applied to the measurement object 61. The voltage to be applied is limited to a limit voltage or less (a voltage value less than an upper limit voltage value that can be applied to the measurement object 61).

  As described above, the resistance measurement apparatus 1 includes the current detection unit 5 that detects the bypass current Iby flowing in the protection circuit 4 connected between the high potential electrode Hc and the high potential electrode Hp, and the processing unit 6 includes: Error processing is executed when it is determined in the determination process that the current value Ib of the bypass current Iby is greater than or equal to the threshold current value.

  Therefore, according to this resistance measuring apparatus 1, the processing unit 6 starts a new current output period, for example, again in error processing while suppressing an excessive voltage rise of the high potential electrode Hc of the current output unit 2. By executing the resistance measurement process, an accurate resistance value R can be measured when the bypass current Iby having a current value Ib greater than or equal to the threshold current value does not flow during this current output period. In addition, according to the resistance measuring apparatus 1, the processing unit 6 performs error processing, for example, resistance measurement processing executed in a current output period in which it is determined that the current value Ib of the bypass current Iby is equal to or greater than the threshold current value. By stopping the output of the measured resistance value R, it is possible to avoid the display of the inaccurate resistance value R and display the accurate resistance value R.

  The operation of the processing unit 6 in error processing is not limited to this configuration. For example, the output of the resistance value R is stopped and the error processing is executed (the current value Ib of the bypass current Iby is a threshold current). This is to be described together with the resistance value R, which is likely to be inaccurate without adopting a configuration in which an error display indicating that the value has exceeded the value is displayed on the output unit 7 or without stopping the output of the resistance value R. It is also possible to employ a configuration in which an error display is displayed on the output unit 7. According to this configuration, the error display can notify the user of the resistance measuring device 1 that the current value Ib of the bypass current Iby is equal to or greater than the threshold current value.

  Further, according to the resistance measuring apparatus 1, when the voltage value Va of the voltage V between the pair of voltage detection terminals exceeds the reference voltage value Vr, the voltage monitoring unit 8 outputs the voltage limiting signal Sc, Since the current output unit 2 receives the voltage limit signal Sc and limits the output voltage (voltage between the pair of current supply terminals) to the limit voltage, the protection circuit 4 is in operation (bypass current Iby flows). Even when the contact state between the high potential electrode Hp and the one terminal 62a becomes unstable, the voltage applied to the measuring object 61 is less than the limit voltage (applied to the measuring object 61). The voltage can be limited to a voltage value less than the upper limit voltage value), and as a result, application of electrical stress to the high potential electrode Hp and the terminal 62a can be avoided.

  In the resistance measuring apparatus 1, even when the contact state between the high potential electrode Hp and the one terminal 62a becomes unstable in a state where the protective circuit 4 is operating, A preferred configuration (configuration including the voltage monitoring unit 8) that limits the applied voltage to a limit voltage or less is adopted, but the current detection unit 5 that detects the bypass current Iby is provided, and the processing unit 6 performs the discrimination process. When it is sufficient to perform error processing when it is determined that the current value Ib of the bypass current Iby is greater than or equal to the threshold current value, the voltage monitoring unit 8 may be omitted.

  In the resistance measuring apparatus 1, the processing unit 6 causes the current output unit 2 to output the measurement current I again during the current output period (a period having the same length as the previous current output period) in the error process. In this new current output period, the voltage measurement unit 3 adopts a preferable configuration for measuring the voltage value Va of the voltage V. However, the resistance measurement without executing the process in the new current output period. A configuration in which the measurement operation is stopped may be employed.

  The processing unit 6 includes an A / D converter and a computer to detect the peak value of the bypass current Iby. Instead of this configuration, a reference voltage indicating a threshold current value and Comparing the voltage value of the detection signal S1 and outputting a pulse signal when the voltage value of the detection signal S1 is equal to or higher than the reference voltage, and converting the pulse signal output from the comparator into a level signal and outputting it to the computer The self-holding circuit can also be configured.

  Further, in addition to the configuration of the resistance measuring apparatus 1 described above, the accurate resistance value of the measurement object 61 measured by the processing unit 6 in the resistance measurement process executed when the current value Ib of the bypass current Iby is less than the threshold current value. Based on R, it is also possible to adopt a configuration in which an inspection process for inspecting the measurement object 61 is executed. In this configuration, the resistance measuring device 1 functions as an inspection device that inspects the measurement object 61 arranged on the circuit board (that is, inspects the circuit board). In this case, the processing unit 6 in the inspection process, for example, the resistance value R of the measurement object 61 measured in the resistance measurement process and the predetermined determination range (for example, the measurement object) of the resistance value R of the measurement object 61 When the measured resistance value R is included in the determination range, it is determined to be a non-defective product, and when it is not included, it is determined to be a defective product. Thus, the measurement object 61 is inspected, and the result of the inspection is output to the output unit 7.

  In this way, according to the resistance measuring device 1 functioning as an inspection device (that is, the inspection device), an accurate resistance value R measured while suppressing an excessive voltage increase of the high potential electrode Hc of the current output unit 2. Based on the above, it becomes possible to inspect the measuring object 61 and the circuit board with high accuracy. In addition, the processing unit 6 stops the inspection based on the resistance value R measured in the resistance measurement process performed in the current output period in which it is determined that the current value Ib of the bypass current Iby is equal to or greater than the threshold current value in the error process. By doing so, the display of inaccurate inspection results can be avoided.

DESCRIPTION OF SYMBOLS 1 Resistance measuring device 2 Current output part 3 Voltage measurement part 4 Protection circuit 5 Current detection part 6 Processing part 61 Measurement object Hc, Hp High potential electrode I Measurement current Iby Bypass current Lc, Lp Low potential electrode

Claims (5)

A current output unit that outputs a measurement current to a measurement target via a pair of current supply terminals, and a voltage measurement unit that measures a voltage across the measurement target when the measurement current flows via a pair of voltage detection terminals And a processing unit that executes a resistance measurement process for measuring the resistance value of the measurement object by a four-terminal method based on the current value of the measurement current and the voltage value of the voltage between both ends. And
A zener diode is included and connected between a high potential side supply terminal of the pair of current supply terminals and a high potential side detection terminal of the pair of voltage detection terminals, and the high potential side When the voltage of the high potential side supply terminal with respect to the detection terminal rises above the Zener voltage of the Zener diode, a part of the measurement current is bypassed from the high potential side supply terminal to the high potential side detection terminal. A protection circuit that suppresses a rise in the voltage of the high potential side supply terminal by flowing,
A current detection unit for detecting the bypass current;
The resistance measurement device that performs a predetermined error process when the current value of the bypass current detected by the current detection unit is equal to or greater than a predetermined threshold current value.   The resistance measurement apparatus according to claim 1, wherein the processing unit performs the resistance measurement process again in the error process.   The resistance measuring device according to claim 1, wherein the processing unit outputs that the current value of the bypass current is equal to or greater than the threshold current value in the error processing. Comparing the voltage value between the pair of voltage detection terminals measured by the voltage measurement unit with a reference voltage value defined in advance below the open upper limit voltage of the current output unit, between the pair of voltage detection terminals A voltage monitoring unit that outputs a voltage limit signal when the voltage value of the voltage exceeds the reference voltage value,
The current output unit includes a voltage limiting function that limits a voltage between the pair of current supply terminals to a limit voltage defined in advance to a voltage value lower than the open upper limit voltage when the voltage limit signal is input. The resistance measuring apparatus according to claim 1.   5. The resistance measurement device according to claim 1, wherein the processing unit measures the resistance measured in the resistance measurement process executed when the current value of the bypass current is less than the threshold current value. An inspection apparatus that inspects the measurement object based on a value.

Images