JPH0569690U - IC test equipment - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an IC tester capable of high-speed operation. [Structure] The same DC voltage as the voltage applied to the core wire is applied to the first shield conductor to test the DC characteristics of the terminal pin of the IC under test with a driving guard structure.
In the IC test apparatus configured to connect the shield conductor of 1 to a common potential and to match the impedance with the core wire to a specific impedance, a second shield conductor is provided outside the first shield conductor. The two shield conductors are connected to a common potential at both ends thereof, so that the characteristic impedance between the core wire and the second shield conductor can be maintained at a predetermined value.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an IC tester of the type that performs both DC characteristics and functional tests of ICs.

[0002]

[Prior Art]

 There are a direct current test and a functional test in the IC test. The direct current test is a voltage applied current measurement test to see if a predetermined current flows when a predetermined voltage is applied to each terminal of the IC under test, and a predetermined current is applied to each terminal of the IC under test. Alternatively, there is a current applied voltage measurement test in which a predetermined current is discharged and whether or not the expected voltage is generated at the terminal in that state. Each test is a test to see whether or not the DC characteristics of the terminals of the IC under test are made to have the characteristics that are planned in advance.

On the other hand, the functional test is a test in which a test pattern signal is applied to an IC under test, and whether or not the IC normally responds to the test pattern signal is tested to see whether the IC normally operates. FIG. 3 shows a connection structure between a test device and an IC under test in a conventional IC test device. In the figure, 10 is an IC to be tested, 20 is a DC test device, 30 is a functional test device, and 40 is a cable connecting between the test devices 20 and 30 and the IC 10 to be tested.

In this example, the DC test apparatus 20 shows a case where it is switched to the voltage applied current measurement mode. In the voltage applied current measurement mode, the voltage generator 21, the output amplifier 22 that applies the voltage generated by the voltage generator 21 to the force line F of the cable 40, and the voltage generated at the terminal of the IC 10 under test are detected by the sense line of the cable 40. A buffer amplifier 23 that returns from S to the output amplifier 22, and a current detection resistor 24 that measures the current flowing from the output amplifier 22 to the IC under test 10 when the output amplifier 22 applies a predetermined voltage to the terminal of the IC under test 10. The differential amplifier 25 for extracting the voltage generated in the current detection resistor 24 and the buffer amplifier 26 for forming the driving guard by applying the output voltage of the output amplifier 22 to the shield conductor 40A of the cable 40. Is configured.

The cable 40 houses two core wires F and S inside a shield conductor 40A. Here, the core wire F operates as a signal drive force wire, and the core wire S operates as a sense wire for detecting the voltage of the terminal pin of the IC under test 10. The shield conductor 40A is connected to the output side of the output amplifier 22 through the buffer amplifier 26, biases the potential of the shield conductor 40A to the same potential as the cores F and S, and the potential difference between the shield conductor 40A and the cores F and S. The driving guard is configured so that it does not occur.

As described above, the driving guard structure in which the potential difference is not generated between the core wires F and S and the shield conductor 40A is equivalent to a state in which no capacitor is formed between the core wires F and S and the shield conductor 40A. become. As a result, even if the DC voltage applied to the core wires F and S changes at high speed, there is equivalently no stray capacitance, so that the DC voltage applied to the terminals of the IC under test 10 can also change at high speed. Moreover, since there is no stray capacitance, neither charging current nor discharging current flows between the core wire and the shield conductor. Therefore, even if a minute DC current is applied to the IC under test 10, the minute current can be accurately transmitted. Further, since the core wires F and S are covered with the shield conductor 40A, noise and the like are prevented from entering. In this way, the cores F and S are protected by the driving guard during the DC test.

At the time of the function test, the relays RY 1, RY 2, RY 3 inserted between the DC test device 20 and the cable 40 are cut off, the relays RY 4, RY 5 are turned on, and the function test device 30 is connected to the cable 40. The function test apparatus 30 has a driver 31 and a comparator 32, and the driver 31 gives a test pattern signal to the IC under test 10. Further, when the IC under test 10 is switched to the output mode, the comparator 32 takes in the response output signal output from the IC under test 10 and makes a logical comparison to determine whether or not the logic matches the expected value.

During the functional test, the cable 40 must operate as a high speed transmission line. Therefore, in order to match the cable 40 with a predetermined characteristic impedance, the shield conductor 40A is connected to a common potential by the relay RY5, the cable 40 is operated as a coaxial line, and the characteristic impedance is provided between the core wire and the shield conductor 40A. I am trying to let you.

[0009]

[Problems to be solved by the device]

 According to the conventional circuit structure, the shield conductor 40A is only connected to the common potential by the relay RY5 on the side of the functional test device 30 and is not connected to the common potential on the side of the IC under test 10. For this reason, the cable 40 causes impedance mismatch on the device under test 10 side, and gives a waveform distortion as shown in FIG. 4 due to signal reflection or the like. Due to this waveform distortion, the test pattern signal PA cannot be speeded up.

That is, it is required to shorten the time required for the test by accelerating the repetition cycle of the test pattern signal PA so that many elements can be tested in a short time. Since waveform distortion is generated at the rising portion of, when the test pattern signal is speeded up (the pulse width is narrowed), most of the pulse width is applied to the distorted portion, so that malfunction easily occurs.

To solve this drawback, the shield conductor 40A of the cable 40 may be connected to the common potential even on the IC 10 side to be tested. However, in order to provide a relay on the IC 10 side under test, the control line of the relay must be wired on the IC 10 side under test. The number of cables 40 must be the same as the number of terminal pins of the IC under test 10. Since the number of terminal pins of an IC is large, some of which are several hundred, it is necessary to prepare a test device assuming the maximum number of pins of an existing IC so that it can be tested. As a result, the number of cables 40 becomes several hundreds, and the same number of relay control lines as this number must be wired, and the same number of relays as the number of cables 40 are mounted on the side of the IC under test 10, that is, the performance. It will have to be mounted on the board.

However, there is no space for mounting such a relay on the performance board, and it is inappropriate to connect the same number of relay control lines as the cable 40. For this reason, it is conceivable that the shield conductor 40A is directly connected to the common potential on the IC10 side under test. However, in such a configuration, the shield conductor 40A is always connected to the common potential on the IC10 side under test. In this state, there is an inconvenience that the driving guard for canceling the stray capacitance of the cable 40 cannot be configured during the DC test. From such a background, there is a disadvantage that the test pattern signal cannot be conventionally speeded up.

An object of the present invention is to eliminate the impedance mismatch in the cable 40, and thereby to provide an IC test apparatus capable of high-speed operation without waveform distortion.

[0014]

[Means for Solving the Problems]

 In this invention, a direct current is applied to the IC under test by using a cable having a shield conductor as an outer jacket, and the same potential as this direct current is applied to the shield conductor to perform driving guard on the core wire to which direct current is applied. In an IC tester that performs a DC test and a functional test by applying a test pattern signal to the IC under test by using a core wire that applies a DC to the IC under test, a shield conductor for configuring a driving guard during the DC test. A second shield conductor is provided on the outside of the insulation so that both ends of the second shield conductor are connected to a common potential so that the second shield conductor and the core wire are matched to a predetermined characteristic impedance. To configure.

According to the configuration of this invention, the second shield conductor is connected to the common potential on both sides of the test apparatus side and the IC under test side. As a result, it is possible to match a predetermined characteristic impedance between the core wire and the second shield conductor. Since the shield conductor for the driving guard exists between the core wire and the second shield conductor as in the conventional case, the driving guard can be constructed during the DC test. As a result, a direct current test can be performed with the driving guard to eliminate the effects of cable stray capacitance. During the functional test, the tested IC side of the cable can also be matched to the regular characteristic impedance. Therefore, no reflection occurs on the IC side to be tested, so that there is an advantage that the test pattern signal can be speeded up.

[0016]

【Example】

 FIG. 1 shows an embodiment of this invention. In FIG. 1, parts corresponding to those in FIG. 3 are designated by the same reference numerals. In this invention, the second shield conductor 40B is provided outside the first shield conductor 40A for constituting the driving guard, and both ends of the second shield conductor 40B, that is, the test device side and the IC 10 side to be tested side. The feature is that both sides are connected to a common potential.

Since the second shield conductor 40B is provided, the first shield conductor 40A need only be connected to the output terminal of the buffer amplifier 26 that constitutes the DC test apparatus 20 by the relay RY3 during the DC test. During the functional test, it is cut off from any electric potential and the floating state occurs. Therefore, since the relay RY5 conventionally provided for connecting the first shield conductor 40A to the common potential is unnecessary, in this embodiment, the relay RY5 is connected between the sense line S and the function test device 30, During the functional test, the test pattern signal can be applied to both the force line F and the sense line S.

FIG. 2 shows a modified embodiment of the present invention. The example of FIG. 2 shows a case where the cable 40 is configured by using a shielded cable having a single-core double shield structure. In other words, one of the single-core shielded cables is used for the force line and the other one is used for the sense line, and the first shield conductor 40A inside each of these single-core double shielded cables is commonly connected. It is connected to the relay RY3 to form a driving guard, and the outer second shield conductor 30B is connected to the common potential at both ends thereof. According to the embodiment of FIG. 2, the single-core double shielded wire can be obtained at a low cost, so that it is possible to provide an IC test apparatus capable of operating at high speed without increasing the cost of the apparatus.

[0019]

[Effect of the device]

 As described above, according to the present invention, by controlling the relay RY3 to be turned on during the DC test, the same potential as that of the force line F and the sense line S is applied to the first shield conductor 40A. Since the so-called driving guard structure is used, even when a minute current is applied to the IC under test 10 because the current is not charged or discharged through the floating capacitance, the minute current can be accurately transmitted to the IC under test 10. Further, even if the DC voltage or the current is changed at high speed, there is no stray capacitance, so that the change can be transmitted to the IC under test 10 without delay.

Of course, during the functional test, the first shield conductor 40A is set to the floating state, so that in this state, the presence of the first shield conductor 40A can be electrically ignored and the second shield conductor 40A can be seen. Since the shield conductor 40B is connected to the common potential at both ends thereof, the characteristic impedance can be matched to a regular value at both ends of the cable 40. As a result, signal reflection does not occur on the IC 10 side under test. Therefore, it is possible to eliminate the distortion of the waveform of the test pattern signal, and it is possible to provide an advantage that it is possible to provide an IC test apparatus that does not malfunction even if the repetition period of the test pattern signal is increased.

[Submission date] January 27, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Since the second shield conductor 40B is provided, the first shield conductor 40A need only be connected to the output terminal of the buffer amplifier 26 that constitutes the DC test apparatus 20 by the relay RY3 during the DC test. During the functional test, it is cut off from any electric potential and the floating state occurs. The relay RY5, which is conventionally provided to connect the first shield conductor 40A to the common potential, is connected between the sense line S and the function test device 30, and is connected to both the force line F and the sense line S during the function test. The test pattern signal is provided.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an embodiment of the present invention.

FIG. 2 is a connection diagram showing a modified embodiment of the present invention.

FIG. 3 is a connection diagram for explaining a conventional technique.

FIG. 4 is a waveform diagram for explaining a conventional inconvenience.

[Explanation of symbols]

 10 IC under test 20 DC test device 30 Functional test device 40 Cable 40A First shield conductor 40B Second shield conductor

Claims (1)

[Scope of utility model registration request] 1. A direct current is applied to an IC under test using a cable having a shield conductor as an outer jacket, and the same potential as this direct current is applied to the shield conductor to protect a core wire to which the direct current is applied. In an IC test apparatus capable of performing a direct current test performed by performing a DC test and a functional test performed by applying a test pattern signal to the IC under test by using a core wire that applies the direct current to the IC under test, a driving guard is provided during the DC test. A second shield conductor is provided on the outside of the first shield conductor for forming the second shield conductor, and both ends of the second shield conductor are connected to a common potential to connect between the second shield conductor and the core wire. An IC test device configured to match a predetermined characteristic impedance.