JPH0714924Y2 - In-circuit tester with discharge power supply circuit and in-circuit tester with power supply circuit for both measurement and discharge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to an in-circuit tester equipped with a discharge power supply circuit for a parallel circuit of an object to be measured and a capacitor and a power supply circuit for both measurement and discharge.

2. Description of the Related Art Conventionally, various electronic devices and the like use parallel circuits of resistors and inductances and capacitors in order to configure their electric circuits. In addition, there is a capacitor in which a capacitor is equivalently in parallel with a resistor or an inductance. Such an electric circuit is usually assembled in the form of a mounting board suitable for miniaturization and handling. However, if an electric component is soldered to a printed circuit board and a printed circuit board is simply used as it is, the repair cost after the product is naturally increased. Therefore, before mounting, the mounting board uses an in-circuit tester to measure and inspect the electrical characteristics of the components mounted on the board to determine the quality of the mounting board.

Such in-circuit testers are classified into a press type and a vacuum type due to the difference in the fixing method of the mounting board to the tester during measurement. In the former, the mounting board is placed on a fixture (pinpod) that is an inspection jig, and a press plate with a large number of holding bars is lowered from above to clamp and fix it, whereas in the latter, there is no press plate. The mounting board is sucked onto the fixture and fixed. After fixing, the measurement power supply circuit with discharge function shown in Fig. 3 was used, and in the press-type in-circuit tester, it was mounted on a printed circuit board (not shown) mounted on the pin board 10 and connected in parallel.
The resistance value R1 of the DUT 14 having 12 is measured, and the electric charge stored in the capacitor 12 is discharged. That is, a constant voltage from the power supply 16 to the DUT 14 (its value E1)
Is applied, and the current flowing therethrough reaches a steady value I1 and is then measured by the ammeter 18, and the resistance value R1 is calculated from the equation of R1 = E1 / I1 by the measuring unit 20 including an arithmetic means such as a microcomputer. Further, if the measuring unit 20 further determines that the resistance value R1 is appropriate, the quality of the mounting substrate can be determined. In addition,
22 and 24 are wiring resistances (their resistance values r1 and r1 ').
Immediately after measurement, switch 26 is closed and the protective resistance (value
The capacitor 12 is discharged through R2) 28. Incidentally, if the wiring resistance values r1 and r1 ′ are sufficiently large as the protection resistance value, the protection resistance 28 is not necessary.

The reason why the capacitor 12 is discharged immediately after the measurement as described above is because if the electric charge remains forever, it is inconvenient for subsequent handling and measurement of other parts. However, if the time during which the switch 26 is closed is lengthened, it is possible to surely discharge all the capacitors 12 having various electrostatic capacities, but of course, the determination of the quality of the mounting board is completed in a short time. Can't do it. Therefore, the switch 26 is closed for a certain period of time, for example, a few ms, or the voltmeter 30
Is connected to both ends of the capacitor 12, closed until the voltage across both ends becomes 0, and is opened again to complete the measurement.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in such a measurement power supply circuit with a discharging function, if the capacitance of the capacitor 12 is large when the switch 26 is closed for a certain period of time like the former, the discharging time becomes insufficient and the electric charge is On the contrary, if it is small, the discharge time becomes unnecessarily long. Also, like the latter, switch 26 to a voltmeter.
If the 30 scale is closed until it reaches 0, the voltage will be 0.
However, the electric charge still remains due to the internal resistance of the capacitor 12, the wiring resistances 22 and 24, and the like. This is because, even if a current is flowing, the voltage based on the electrostatic capacity of the capacitor 12 is canceled by the voltage drop of their internal resistance and the like, and the scale of the voltmeter 30 shows 0.

The present invention has been made by paying attention to such a conventional problem, and it is mounted by surely discharging the discharge time according to the capacitance of the capacitor connected in parallel to the DUT. To provide an in-circuit tester with a discharge power supply circuit that can measure and inspect a board in a short time and accurately judge whether it is good or bad, and an in-circuit tester with a power supply circuit that also measures and can measure an object to be measured. With the goal.

Means for Solving the Problems Means for achieving the above object will be described below with reference to FIGS. 1 and 2 corresponding to the embodiments.

This in-circuit tester with discharge power circuit is the object to be measured.
A power supply 44 connected to one end 42 of the parallel circuit 40 via the ground, targeting the capacitor 38 connected in parallel to the 36.
An applied voltage switch 46 that switches the power supply voltage E2 applied to the parallel circuit 40 to the ground potential, and an operational amplifier 50 that directly applies the applied voltage to the other end 48 of the parallel circuit 40 via an input terminal.
And the output terminal of the operational amplifier 50 and the other end 48 of the parallel circuit 40.
And the discharge current detection resistor 52 that is interposed between
A voltmeter 54 for measuring the voltage V across 52 and the measured voltage V
And a voltage comparator 56 that outputs a discharge end signal S1 by comparing with a threshold voltage Vd for ending the discharge of the capacitor 38.

Further, in the in-circuit tester with a power supply circuit for both measurement and discharge, the ammeter 64 for outputting the steady current value detection signal S2 is further connected in series between the one end 42 of the parallel circuit 40 and the ground.
Is added.

When the discharge power supply circuit configured as described above is provided, a constant voltage is applied to the DUT 36 having the capacitor 38 connected in parallel to perform measurement, and then the applied voltage switch 46 causes the non-inversion of the operational amplifier 50. The voltage applied to the input terminal (+) can be switched to 0 (ground potential). Then, due to the imaginary short circuit of the operational amplifier 50, the inverting input terminal (-)
Also becomes 0. Therefore, the electric charge stored in the capacitor 38 flows into the output terminal of the operational amplifier 50 through the discharge current detection resistor 52. The voltage V across the detection resistor 52 is measured by a voltmeter 54 and input to a voltage comparator 56. The voltage comparator 56 compares the measured voltage V with a threshold voltage Vd for ending the discharge according to the capacitance of the capacitor 38, and outputs a discharge end signal.
Output S1. The applied voltage switch 46 allows
Once the voltage applied to the non-inverting input terminal (+) of the operational amplifier 50 is made negative and then set to 0, the discharge of the capacitor 38 is further accelerated, and the voltage V across the discharge current detection resistor 52 is set below the threshold value. You can

Further, when a power supply circuit for both measurement and discharge is provided, by adding an ammeter 64, it can be used for measuring the DUT 36 prior to discharging the capacitor 38. That is, when the constant voltage E2 is applied from the power source 44 to the non-inverting input terminal (+) of the operational amplifier 50 through the applied voltage switch 46, the constant voltage E2 appears at the inverting input terminal (-) due to an imaginary short circuit, and the constant voltage E2 appears. Measured object 36
Apply to. Therefore, an ammeter 64 interposed between one end 42 of the parallel circuit 40 of the DUT 36 and the capacitor 38 and the ground.
Then, the current flowing through the DUT 36 is measured after reaching the steady current value I2, and the detection signal S2 is output. As a result, the resistance value R4 of the DUT 36 can be calculated from the quotient of the constant voltage value E2 and the steady current value I2.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a configuration diagram showing a main part including a discharge power supply circuit of a press-type in-circuit tester to which the present invention is applied. In the figure, 32 is a pin board having upwardly protruding probe pins 34 (34a, 34b), 36 is a resistor mounted with a capacitor 38 mounted in parallel on a printed circuit board (not shown) and a coil Is the object to be measured. When measuring the DUT 36 as described above, the electric charge is naturally stored in the capacitor 38 connected in parallel to the DUT 36. Therefore, it is necessary to immediately discharge the electric charge after the measurement. Therefore,
A discharge power supply circuit for the capacitor 38 is provided. This discharge power supply circuit includes a power supply 44 connected to one end 42 of the parallel circuit 40 via a ground, an applied voltage switcher for switching the power supply voltage E2 applied to the parallel circuit 40 to a ground potential, and a changeover switch 46, and its application. An operational amplifier 50 that directly applies a voltage to the other end 48 of the parallel circuit 40 via an input terminal, a discharge current detection resistor 52 interposed between the output terminal of the operational amplifier 50 and the other end 48 of the parallel circuit 40, and its detection. A voltmeter 54 that measures the voltage V across the resistor 52, and the measured voltage V
And a voltage comparator 56 that outputs a discharge end signal S2 in comparison with a threshold voltage Vd for ending discharge according to the electrostatic capacitance of 38, for example, 10 mV, and the discharge end signal S2 is a calculating means such as a microcomputer. Enter the measuring unit 58 including. The resistance values r2 and r2 'of the wiring resistors 60 and 62 are smaller than the resistance value R3 of the discharge current detection resistor 52 and can be ignored.

If such a discharge power supply circuit is provided, a constant voltage is applied to the DUT 36 having the capacitor 38 connected in parallel to measure the resistance value and the like, and then the changeover switch 46 as an applied voltage changer is operated. Then, the non-inverting input terminal (+) of the operational amplifier 50 can be quickly switched to the ground side and the voltage applied thereto can be adjusted to zero. Then, the potential of the inverting input terminal (-) becomes 0 due to the imaginary short circuit of the operational amplifier 50. Therefore, the electric charge stored in the capacitor 38 flows into the output terminal of the operational amplifier 50 through the discharge current detection resistor 52. Incidentally, the input impedance of the operational amplifier is very large, and the output impedance is very small. The voltage V across the detection resistor 52 is measured by a voltmeter 54 and a voltage comparator
Put in 56. In the voltage comparator 56, the threshold voltage for ending the discharge according to the measured voltage V and the electrostatic capacity of the capacitor 38.
The discharge end signal S2 is surely output by comparing with Vd. Since this discharge end signal S2 is confirmed to enter the measuring unit 58, it is possible to quickly shift to measurement of other components. It should be noted that the voltage applied from the power supply 44 to the non-inverting input terminal (+) of the operational amplifier 50 is once made negative by the applied voltage switch 46, and then set to 0, whereby the discharge of the capacitor 38 is further accelerated, and both ends of the discharge current detection resistor are made. The voltage V can be quickly reduced to the threshold value or less.

FIG. 2 is a configuration diagram showing a main part including a power supply circuit for both measurement and discharge of a press-type in-circuit tester to which the present invention is applied. In this embodiment, as compared with the above embodiment, a series connection is provided between the one end 42 of the parallel circuit 40 and the ground shown in the above embodiment, further an ammeter 64 is interposed, and a steady current value detection signal S2 measured there is provided. All are the same except that they are given to the measurement unit. Therefore, in the following description, the same components are designated by the same reference numerals.

When the ammeter 64 is added in this manner, it can be used for the measurement of the DUT 36 prior to the discharge of the capacitor 38, and thus the power supply circuit for both measurement and discharge is provided. Therefore, in order to measure the resistance value R4 of the DUT 36, first, the constant voltage E2 is applied to the non-inverting input terminal (+) of the operational amplifier 50 from the power supply 44 through the applied voltage switching device 46 to cause an imaginary short circuit. Utilizing this, a constant voltage E2 is generated at the inverting input terminal (-) and applied to the DUT 36. Then the ammeter 64
Then, the current flowing through the DUT 36 can be measured after reaching the steady current value I2 and the detection signal S2 can be output. Since this detection signal S2 enters the measuring section 58, the resistance value of the DUT 36 is
R4 can be calculated from the quotient of the constant voltage value E2 and the steady current value I2. Further, the discharging operation of the capacitor 38 is the same as that in the above embodiment. As a result, a series of operations including the measurement of the resistance value R4 of the DUT 36 and the discharging of the capacitor 38 connected in parallel therewith can be reliably performed in a short time.

Although the press-type in-circuit tester is described in each of the above embodiments, the same applies to the vacuum-type in-circuit tester.

According to the present invention described above, according to the first aspect of the present invention, the capacitance of the capacitor, which is provided with the discharge power supply circuit and is connected in parallel to the DUT, is discharged and the discharge current is measured. The discharge can be reliably performed in a short discharge time according to. Therefore, the mounting substrate can be measured and inspected in a short time, and its quality can be accurately determined. Further, in claim 2, since the circuit for both measurement and discharge is provided, the power supply circuit can be shared for measurement and discharge, and a series of operations from measurement to end of discharge can be performed in a short time.
Can be done reliably.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a main part including a discharge power supply circuit of a press-type in-circuit tester to which the present invention is applied. FIG. 2 is a configuration diagram showing a main part including a power supply circuit for both measurement and discharge of a press-type in-circuit tester to which the present invention is applied. FIG. 3 is a configuration diagram showing a main part including a measurement power supply circuit with a discharge function of a conventional press-type in-circuit tester. 32 ... Pin board, 36 ... DUT, 38 ... Capacitor, 40 ...
Parallel circuit, 42, 48 ... One end, the other end, 44 ... Power supply, 46 ... Applied voltage switching device, 50 ... Operation amplifier, 52 ... Discharge current detection resistor, 54 ... Voltmeter, 56 ... Voltage comparator, 64 ... Ammeter

Claims (2)

[Scope of utility model registration request] 1. A power supply for a capacitor connected in parallel to an object to be measured, which is connected to one end of the parallel circuit via a ground, and an applied voltage for switching a power supply voltage applied to the parallel circuit to a ground potential. A switching device, an operational amplifier for directly applying the applied voltage to the other end of the parallel circuit through an input terminal, a discharge current detection resistor interposed between the output terminal of the operational amplifier and the other end of the parallel circuit, and the detection resistor A discharge power supply circuit comprising a voltmeter for measuring the voltage across both ends and a voltage comparator for outputting a discharge end signal by comparing the measured voltage with a threshold voltage for ending the discharge of the capacitor. In-circuit tester with discharge power circuit. 2. A power supply connected to an ammeter for outputting a steady current value detection signal, which is connected in series to one end of a parallel circuit, which is intended for a capacitor connected in parallel to an object to be measured, and a grounded power supply. An applied voltage switcher that switches the power supply voltage applied to the parallel circuit to the ground potential, an operational amplifier that applies the applied voltage directly to the other end of the parallel circuit via an input terminal, an output terminal of the operational amplifier, and the other end of the parallel circuit. Between the discharge current detection resistance and the voltmeter that measures the voltage across the detection resistance, and the voltage comparison that outputs the discharge end signal by comparing the measured voltage with the threshold voltage that ends the discharge of the capacitor. An in-circuit tester with a power supply circuit for both measurement and discharge, which has a power supply circuit for both measurement and discharge.