KR100355716B1 - Test method of low resistor for in-circuit tester - Google Patents

Abstract

The present invention provides a three-wire insert tester in which a four-wire Kelvin measurement method can be applied to inspect resistors of very low resistance using simple software without additional hardware modification or addition. It relates to a low resistance measurement method.

The present invention for this purpose, the control of the measurement unit 3 consisting of the signal generator 9, the signal detector 10 and the mode setting relay 11 via the input and output interface unit 2 in the personal computer 1 Test probes 7 connected to the multiplexer unit 4 by selectively connecting the relay contacts of the multiplexer unit 4 connected to the measuring unit 3 with three measuring lines H, G, and L through the measuring unit 3. In the measurement method of the insert kit tester to measure the resistance value of the resistance to be measured through the selected one of the selected test probes, the information (type, test probe number, etc.) of the component to be examined in the personal computer (1) interface unit ( Transmitting to the measurement unit 3 through 2), the mode setting relay 11 of the measurement unit 3 is operated according to the component information, so that the constant current source is connected to the measurement line H to be connected to the upper end of the resistance to be measured. 12) and the lower end of the measured resistance (30) Connecting the measurement line (L) to be connected to the ground terminal, connecting the voltmeter (14) to the measurement line (G) and connecting the measurement line (G) and the upper end of the resistance to be measured (30) in the multiplexer unit (4) Measuring the voltage drop from the upper end of the resistance 30 to the ground terminal by connecting the relay contact, and temporarily storing the voltage, and turning off the relay contact connecting the upper end of the measurement line G and the resistance 30 to be measured. After that, by connecting the relay contact connecting the measurement line (G) and the lower end of the resistance 30 to be measured, temporarily measuring the voltage drop from the lower end of the resistance to measurement 30 to the ground terminal, and temporarily storing the measured voltage drop. The voltage drop measured by the measured resistance 30 is detected by subtracting the voltage drop measured at the lower end of the measured resistance 30 from the voltage drop measured at the upper end of the measurement resistance 30. The resistance to be measured is divided by dividing the constant current value applied to the resistor 30. Detecting the resistance value and converting it into a digital signal and transmitting it to the personal computer (1), and repeating the detection step for all the measured resistances.

Description

TEST METHOD OF LOW RESISTOR FOR IN-CIRCUIT TESTER}

The present invention is an insert kit that can be applied to the 4-wire Kelvin measurement method that checks resistors of very low resistance using simple software without additional hardware modification or addition in the 3-wire insert kit tester. A low resistance measurement method in a tester.

Insert kit tester is a kind of tester that inspects electronic parts. Unlike general measuring instruments that test a single part, the insert kit tester is an electronic part assembled on a circuit board, that is, the circuit part is composed and affected by surrounding parts. It is a measuring device that automatically inspects all parts according to the inputted information while removing the influence of peripheral circuits and displays defective items, defective contents, and defective locations.

In general, the low current resistance of the insert tester is a method of using a constant current. The constant current set in the insert tester is applied to the resistance under test, and the voltage across the resistance is measured. The voltage is then divided by the applied current to calculate the resistance (Ohm's law). A simple example is shown in FIG. 5A, wherein the measuring section 3 is provided with a DC constant current source 20 and a DC voltmeter 21, and the multiplexer section 4 includes a relay contact including a relay not shown. 22 and 23 are provided, and the fixture 5 is provided with a resistance under measurement 24 which is assembled on a circuit board, and forms a network for measuring the resistance value of the resistance under measurement 24.

If the contact resistance of the relay contacts 22 and 23 included in the multiplexer section 4 and the line resistance from the constant current source 20 to the measured resistance 24 are regarded as 0 Ω, the resistance value is ohm. Using the law, resistance (R) = voltage / current = 0.1 / 0.1 = 1 Ω. However, in the actual insert kit tester, since the contact resistance of the relay contacts 22 and 23 included in the multiplexer section 4 and the line resistance from the constant current source 20 to the resistance under measurement 24 exist, the result is It does not appear exactly as above.

5B shows a result of low resistance measurement in a conventional insert kit tester. The actual value of the measured resistance 24 to be actually tested is 1 Ω, but the measurement result is 2 Ω. That is, the resistance R = voltage / current = 0.2 / 0.1 = 2 Ω. When measuring such low resistance (usually 1Ω or less), accurate measurement cannot be made because of the line resistance between the measuring section 3 and the measured resistance 24 and other contact resistances.

Most of the test kit testers cannot accurately check the low resistance for this reason. However, a technique has been proposed to test the very low resistance without the influence of the surroundings using the 4-wire Kelvin measurement method. Shows a low resistance measurement method in an insert kit tester using the 4-wire Kelvin measurement method. That is, the measuring section 3 is provided with a DC constant current source 20 and a DC voltmeter 21, and the multiplexer section 4 includes relay contacts 22, 23, 25, 26 including a relay (not shown). The fixture 5 is provided with a resistance under measurement 24, and at one end of the resistance under measurement 24, the DC constant current source 20 and the DC voltmeter 21 through the respective lines H1 and H2. In addition to the positive terminal of the other end of the DC constant current source 20 and the negative terminal of the DC voltmeter 21 is connected through each line (L2, L1).

Since the input impedance of the voltmeter 21 is almost infinity, no current flows in the direction of the voltmeter 21, so there is no unnecessary voltage drop between the resistance under measurement 24 and the voltmeter 21. Accurate measurement of the actual voltage across both ends can be made, and the resistance value can be calculated to allow for very low resistance inspection.

The present invention has been invented a method for measuring low resistance by applying the four-wire Kelvin measurement method to an insert kit tester having a three-wire measurement unit and a multiplexer unit, and has already been widely used in production. Most of the three-wire insert kit testers used are to provide a low resistance measurement method in the insert kit tester that enables high precision low resistance measurement with a simple software change.

1 is a block diagram showing an insert kit tester and a personal computer according to an embodiment of the present invention;

2 is a flowchart illustrating a low resistance measuring method in the insert kit tester of the present invention;

3 and 4 are circuit diagrams showing in detail the measuring unit and the multiplexer shown in FIG.

5 is a circuit diagram showing a low resistance measurement method in a conventional insert kit tester.

* Explanation of symbols for main parts of the drawings

1: personal computer 2: interface unit

3: measuring section 4: multiplexer section

5: fixture 6: substrate under test

7: test probe 8: air cylinder

Low resistance measurement method in the insert kit tester of the present invention for achieving the above object, the signal generation unit 9, the signal detection unit 10 and the mode setting via the input and output interface unit 2 in the personal computer 1 By selectively connecting the relay contact of the multiplexer unit 4 connected to the measuring unit 3 by three measuring lines H, G, and L through the control of the measuring unit 3 including the relay 11. In the measuring method of the insert tester to measure the resistance value of the resistance to be measured through a test probe selected from among the test probes 7 connected to the multiplexer unit 4, the component to be inspected in the personal computer 1 Transmitting the information (type, test probe number, etc.) of the measuring unit 3 to the measuring unit 3 via the interface unit 2, and operating the mode setting relay 11 of the measuring unit 3 based on the component information. Measurement line (H) to be connected to the top of the resistor Connecting the constant current source 12 and connecting the measurement line L to be connected to the lower end of the resistance 30 to the ground terminal, connecting the voltmeter 14 to the measurement line G, and multiplexer portion 4 Measuring a voltage drop from the upper end of the measured resistance 30 to the ground terminal by connecting a relay contact connecting the upper end of the measured line G to the measured resistance 30 and temporarily storing the measured line. (G) turns off the relay contact connecting the upper end of the resistance 30 to be measured, and then connects the relay contact connecting the lower end of the measurement line G with the resistance 30 to be measured. Measuring and temporarily storing the voltage drop from the lower end to the ground terminal, subtracting the voltage drop measured at the lower end of the measured resistance 30 from the voltage drop measured at the upper end of the measured resistance 30 The voltage drop by the resistance 30 to be detected is detected and Dividing the constant current value applied to the resistance to be measured 30, detecting the resistance value of the resistance to be measured 30, converting it into a digital signal, and transmitting it to the personal computer 1, wherein the detecting step is performed on all the resistances to be measured. Characterized in that it comprises a step for repeating for.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing an insert kit tester and a personal computer according to an exemplary embodiment of the present invention, using a simple software without additional hardware modification or addition to the insert kit tester of the 3-wire method. It is possible to apply the 4-wire Kelvin measurement method to check the resistor of low resistance.

The personal computer 1 includes a signal generator 9, a signal detector 10, a mode setting relay 11, and the like. Control signal, multiplexer control signal and measurement data are connected to each other. The measuring section 3 is connected to the multiplexer section 4 of the relay matrix through three measuring lines H, G, and L, and the fixture 5 is connected to the corresponding relay contact of the multiplexer section 4. While the test probe 7 is connected, the test probe 7 is in contact with the substrate 6 to be moved by the air cylinder 8 of the press unit.

FIG. 2 shows a low resistance by applying a Kelvin measurement method that can be measured by a 4-wire method in an insert kit tester including a measuring part 3, a multiplexer part 4, and a fixture 5 made of a 3-wire method. First, the measuring substrate 6 to be inspected by the operator is placed on the fixture 5 of the press unit, and the measuring substrate 6 is operated by operating the air cylinder 8. And the test probe 7 of the fixture 5 are in intimate contact.

At this time, the information (type, test probe number, etc.) of the component to be inspected is transmitted from the personal computer 1 to the measuring unit 3 through the interface unit 2, and the measuring unit 3 The mode setting relay 11 is operated to generate a source signal for measurement. Then, the relay matrix of the multiplexer unit 4 is selectively operated to connect the corresponding test probes 7 to the measurement lines H, G, and L, and to measure the signals of the measurement lines H, G, and L. It converts into a digital signal, and the measurement result converted into a digital signal is transmitted to the personal computer 1 through the interface unit 2. Since the process of converting and transmitting the measurement result into the digital signal as described above is performed in a conventional insert kit tester, a detailed description thereof will be omitted in order to prevent the gist of the present invention from being confused.

As described above, the process of measuring the low resistance value of the resistance to be measured and transmitting the measurement result to the personal computer 1 is to inspect one part at a time, and thus repeats the above measurement process up to the last part. Therefore, when the inspection of all the components on the substrate 6 is finished, the press is automatically raised. When all the components on the substrate 6 are inspected to the end, all the measurement results are analyzed and the final The results can be displayed on the screen or printed out and printed on a printer.

The method of measuring the low resistance in the insert kit tester of the present invention will be described in detail with reference to FIGS. 3 and 4. FIG. 3 shows the measurement unit 3, the multiplexer unit 4, and the resistance under test 30: FIG. 4. ) Is a three-wire in-circuit tester that connects the fixture (5) in contact with the three-wire measuring line (H, G, L), and is connected to each part of the three-wire measuring line (H, G, L). The switching relay contacts can be operated individually individually by a program set in the personal computer 1. The measuring unit 3 is connected to a relay contact through a 0.1 A constant current source 12 so as to selectively supply constant current to the measuring line H or G, and a constant voltage source 13 of 0.2 V is measured. It is connected via relay contact to supply constant voltage selectively to the line (H or G), and through the relay contact so that the voltmeter 14 can measure the voltage of the measuring line (H or G) selectively. In addition, the ammeter 15 is connected to measure the current flowing in the measurement line (L). In addition, the measuring section 3 is provided with a relay contact that can selectively connect the measuring lines H, G, and L to the ground side, and a multiplexer section connected to the measuring lines H, G, and L. (4) is common to one test probe (7) in which one terminal of the relay contact is connected to each measuring line (H, G, L) and the other terminal of the relay contacts is fixed to the fixture (5). As described above, the test probes 7 as described above are provided in plural so as to measure resistance values of resistors assembled in various printed circuit boards. In FIG. 3, the test probes 7 may include 1, 2, 3…. 2048 pieces are provided and show the connected state, respectively.

4 is a view for explaining a method of precisely measuring the low resistance of a resistor by a four-wire Kelvin measurement method using a three-wire insert kit tester according to the present invention, and for this purpose, the relay of the multiplexer unit 4 The constant current source 12, the voltmeter 14, and the ground terminal of the measuring section 3 are selectively connected to the resistance under test 30 according to the contact state of the contact. In the following description, for simplicity of explanation, a terminal located on the side opposite to the ground side of the resistor 30 to be measured, that is, a terminal capable of measuring a voltage drop from the ground side to the resistor 30 to be measured is referred to as a "resistance measured". And the voltage drop between the ground side and the measured resistance 30 in the state in which the terminal connected to the ground side, i.e., the resistance under measurement 30, is excluded from the resistance under measurement 30. The terminal which can be referred to as "lower end of the resistance 30 to be measured." In the measurement of the resistance 30 to be measured, first, the output of the DC constant current source 12 is connected to a relay contact to the measurement line H. Then, one side is connected to the ground side and the other side is connected to the relay contact is connected to the measurement line (L) to connect the measurement line (L) to the ground side. Subsequently, the multiplexer unit 4 turns on the relay contact 16 connected to the constant current source 12 and the upper end of the resistance 30 under test, and is connected to the ground side and the lower end of the resistance 30 under measurement. Turn on the relay contact 17. Accordingly, the same current of 0.1 A supplied from the constant current source 12 flows through the relay contacts 16 and 17 and the resistance under test 30. For example, the contact resistance of the relay contacts 16 and 17 is 0.5, respectively. If Ω and the measured resistance 30 is 1 Ω, a voltage drop of 0.05 V occurs at each of the relay contact portions, and 0.1 V across both of the measured resistance 30.

Subsequently, the output terminal of the DC voltmeter 14 is connected to the measurement line G through a relay contact connection, and then the multiplexer unit 4 connected between the DC voltmeter 14 and the upper end of the resistance 30 to be measured. Turns on the relay contact 18, while turning off the other relay contact 19 of the multiplexer section 4, which is connected between the DC voltmeter 14 and the lower end of the resistor 30 to be measured. At this time, the voltmeter 14 detects 0.15V, which is the sum of the voltage drop due to the contact resistance of the relay contact 17 and the voltage drop across the measured resistance 30, and stores the value temporarily in a memory (not shown). (V1 = 0.15).

Next, it is connected between the DC voltmeter 14 and the upper end of the resistance under measurement 30 in order to measure the voltage between the voltmeter 14 and the ground side in the state except the voltage drop due to both ends of the resistance under measurement 30. In addition to turning off the relay contact 18 of the multiplexer unit 4, the relay contact 19 connected between the DC voltmeter 14 and the lower end of the resistor 30 to be measured, the voltmeter 14 detects a voltage drop of 0.05 V due to the contact resistance of the relay contact 17. Then, as described above, subtracting the voltage detected at the lower end of the measured resistance 30 from the voltage V1 = 0.15 V detected at the upper end of the measured resistance 30 causes the voltage drop generated at both ends of the actual measured resistance 30 to be 0.1V. It can be measured that, and dividing the measured voltage 0.1V by the current value 0.1A flowing through the resistance 30 to be measured accurately to measure that the resistance 30 to be measured 1Ω. When the measurement of one resistance is completed as described above, all relay contacts 16-19 are turned off to wait for the measurement operation on the next measurement resistance.

As described above, according to the present invention, since the low resistance can be measured using the Kelvin measurement method without any hardware configuration modification or addition in the conventional three-wire insert kit tester, expensive equipment is not newly introduced. It is also possible to inspect low resistance of less than 1 Ω, and it is advantageous to expand the measuring range of the insert kit tester economically.

In the present invention, the resistance test of 1 Ω or less has been described as an example, but the capacity test of the fuse can be easily performed within a range not departing from the technical gist.

Claims (3)

In the personal computer 1, the measuring unit 3 is controlled by the measuring unit 3 including the signal generator 9, the signal detector 10, and the mode setting relay 11 via the input / output interface unit 2. Selected among the test probes 7 connected to the multiplexer unit 4 by selectively connecting the relay contact of the multiplexer unit 4 connected to the three-wire measuring line (H, G, L) to In the measuring method of the insert kit tester to measure the resistance value of the resistance to be measured through the personal computer 1, the information (type, test probe number, etc.) of the component to be examined in the personal computer 1 through the measurement unit through the interface unit 2 (3) the step of connecting the constant current source 12 to the measurement line (H) to be connected to the upper end of the resistance to be measured by operating the mode setting relay 11 of the measurement unit 3 according to the part information; In addition, the measurement line (L) to be connected to the lower end of the resistance to be measured (30) Connecting to the ground terminal, connecting the voltmeter 14 to the measurement line (G) and connecting the relay contact connecting the measurement line (G) and the upper end of the resistance to be measured (30) in the multiplexer (4) Measuring and temporarily storing the voltage drop from the upper end of the resistor 30 to the ground terminal, and after turning off the relay contact connecting the measuring line (G) and the upper end of the resistance to be measured 30, the measuring line (G) ) And connecting the relay contact connecting the lower end of the resistance 30 to measure the voltage drop from the lower end of the resistance 30 to the ground terminal and temporarily storing the voltage drop, at the upper end of the resistance 30 The voltage drop measured by the actual measured resistance 30 is detected by subtracting the measured voltage drop from the lower end of the measured resistance 30 from the measured voltage drop. The resistance value of the resistance under measurement 30 is detected by dividing the constant current value. Low-resistance measuring method of the inserter kit tester, characterized in that by converting a digital signal consisting of, including the step of repeating the steps carried out, the detection method comprising: transmitting to the personal computer 1 to all the measured resistance. delete delete