JPH04109177A - Power supply short circuit inspection method for semiconductor circuits - Google Patents

Abstract

PURPOSE:To perform a power short circuit inspection without being affected by power impedance by applying the voltage in the range to keep semiconductor elements at the cutoff state to power terminals of a tested semiconductor circuit in sequence with a voltage source having a current clamping function. CONSTITUTION:Voltage (e) is applied to VTT or VEE power terminals 3, 4 of a tested semiconductor circuit 1 by a voltage source 5 with a current clamping function while a switch 6 is switched, and the voltage of the terminal 3 (4) applied with the voltage (e) and the voltage of the other terminal 4 (3) are measured by voltmeters 7, 8 respectively. If there is no short circuit between the VTT or VEE power source applied with the voltage and the earth Vcc, the voltage of the terminals 3, 4 is equal to the applied voltage, if there is a short circuit, it becomes the earth potential (OV). If there is no short circuit between VTT, VEE power sources, the voltage of the other terminal not applied with the voltage becomes the earth potential, if there is a short circuit, the voltage is equal to the applied voltage. The short circuit between the Vcc and VTT, VEE power sources can be judged regardless of the power impedance of the circuit 1. The voltage in the range to keep semiconductors at the cutoff state is applied, thus elements are not damaged.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for inspecting short circuits between power supplies and power supply ground in circuits composed of semiconductor elements, such as semiconductor integrated circuits and circuit boards on which they are mounted.

[Conventional technology]

In conventional power supply short-circuit inspection, the presence or absence of a short-circuit was determined by measuring the resistance value between each power supply terminal and comparing it with a previously determined resistance value of a normal circuit.

[Problem to be solved by the invention]

The above conventional technology does not take into consideration the power supply impedance of the semiconductor circuit, and the power supply impedance of the semiconductor circuit under test varies depending on the circuit configuration of the semiconductor element, its degree of integration, etc., and its value increases as semiconductor circuits become more highly integrated. In some cases, the resistance is as small as several Ω. For this reason, there is a problem in that it is difficult to judge whether the circuit is normal or short based on the resistance value.6 The purpose of the present invention is to test for power supply short circuits without being affected by the power supply impedance of the semiconductor circuit under test. The object of this invention is to minimize damage to the semiconductor circuit under test by inspecting the power supply short circuit when there is a power supply short circuit in the semiconductor circuit under test.

[Failure to solve the problem]

In order to achieve the above object, a voltage is sequentially applied to each power supply terminal of the semiconductor circuit under test. In order to check for a short circuit between grounds, measure the voltage at the power supply terminal to which voltage is applied, and determine whether or not the voltage is being applied normally. Furthermore, in order to check for short circuits between power supplies, the voltages of other power supply terminals to which voltage is not applied are measured, and a determination is made based on whether or not voltage is applied.

Furthermore, if there is a power supply short circuit in the semiconductor circuit under test,
To minimize damage to the semiconductor circuit under test,
A voltage source with a current clamping function is used, and the applied voltage is set within a range in which the semiconductor element maintains a cut-off state.

[Effect]

A voltage within a range in which the semiconductor element maintains a cut-off state is sequentially applied to each power supply terminal of the semiconductor circuit under test using a voltage source having a current clamping function. If there is no short circuit between the energized power supply and ground, the voltage measurement result at this power supply terminal will be equal to the applied voltage; if there is a short circuit, it will be at ground potential (OV), and if there is no short circuit between the power supplies, The voltage measurement result of other power supply terminals to which no voltage is applied becomes the ground potential (Ov), and if there is a short circuit, it becomes equal to the applied voltage. In this way, by sequentially applying voltage to each power supply terminal and determining the voltage of each power supply terminal each time it is applied, short circuits between ground and power supply can be determined regardless of the power supply impedance of the semiconductor circuit under test. .

If there is a short circuit between power supplies in the semiconductor circuit under test, voltage will be applied to multiple power supplies simultaneously.

Since the applied voltage is within the range where the semiconductor element maintains the cut-off state, the semiconductor element will not be damaged.
If there is a short circuit between power supplies or ground, a short circuit current will flow in the shorted part, but due to the current clamp function of the voltage source, the current will not flow above a certain value, and this value can be set to a small value within the range that can supply the cutoff current. Therefore, damage to the short circuit can be minimized. This can also be achieved by using a voltage source with a small current supply capacity.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows the measurement circuit of this embodiment, 1 indicates ECL (E
2 to 4 are power supply terminals of the semiconductor circuit under test 1, 2 is a Vcc (ground) terminal, and 3 is a Vcc (ground) terminal.
TT power supply terminal, 4 is a v■ power supply terminal, 5 is a voltage source with a power supply clamp function, 6 is a switch for switching the applied power supply terminal, and 7 and 8 are voltmeters for measuring the voltage of the power supply terminal.

Figure 2 shows (1) normal state, (2) VTT-VCC, respectively.
These are the test results when a short circuit occurs and (3) when a Vtt Vzz short circuit occurs.

The voltage applied by the voltage source 5 with a current clamp function is set to a voltage e within a range where the semiconductor circuit under test l maintains a cut-off state (for example -
〇, set to 3V). Further, the clamp current is set to the minimum within a range that satisfies the sum of the interrupting currents flowing to the power supply terminals when voltage e is applied to the VTT power supply terminal 3 and the ■□□ source terminal 4 of the semiconductor circuit under test 1, respectively.

While switching the switch 6, a voltage e is sequentially applied to the Vtt power supply terminal 3 and the v0 power supply terminal 4 of the semiconductor circuit under test l using the voltage source 5 with a current clamping function in which the applied voltage and clamp current are set. The voltage between the power supply terminal that is applying voltage and the voltage of the other power supply terminal.

Measure with voltmeters 7 and 8, respectively. Semiconductor circuit under test 1
If there is no short circuit between the VTT power supply and the v0 power supply between the ground (Vcc) and the power supply, as in the normal state (1) in Figure 2,
The applied voltage e is measured only to the power supply terminal to which the voltage is applied, and the measurement result of the other power supply terminal is ov.* If the Vtt power supply is short-circuited to the ground (Vcc), the Vtt power supply terminal 3
Even if voltage e is applied to (2) Vtt-Vcc in Figure 2,
As in the case of a short circuit, the measured value of the voltmeter 7 is Ov. The same applies when the v0 power supply is short-circuited to ground (V c c ).

If there is a short circuit between VTTll[ and v00 power supply, (
3) As in the case of VTTV□ short circuit, the applied voltage e is measured at the power supply terminal to which no voltage is applied.

VT? If there is a short circuit between the power supply and the v0 power supply, between the ground (Vcc) and between the power supply, a short circuit current will flow through the short circuit, but
A current exceeding the set value does not flow through the voltage source 5 with a current clamp function, and damage to the short-circuited portion can be minimized.

Also, if there is a short circuit between the VTT power supply and the V□ power supply, the VT
A voltage e is simultaneously applied to the T power supply and the Vzz power supply, but the applied voltage e is set within a range in which the semiconductor circuit under test 1 maintains a cut-off state, so that it does not damage the semiconductor circuit under test 1.

According to this embodiment, it is possible to test for short circuits in the power supply by applying voltage to the power supply terminals and checking whether the voltage is being applied normally or whether voltage is being applied to the power supply terminals to which no voltage is being applied. , there is no need to determine the resistance value between the power supply terminals and between the power supply and ground terminals in advance in a normal circuit, and even if the difference between the resistance value during normal operation and the resistance value at the time of a short circuit is small, it is possible to detect a short circuit. Can be detected. Furthermore, damage to short-circuited parts is minimized and semiconductor elements are not damaged.
This has the effect of being able to repair semiconductor circuits with short circuits in the power supply.

Figure 3 shows the voltage source 5 with current clamp function, switch 6, and voltmeters 7 and 8 shown in Figure 1 realized by a programmable power supply that can set the output voltage value and clamp current value as desired, and has an output voltage measurement function. This is what I did. 9 and 10 are program power supplies.

The difference from the embodiment shown in FIG. 1 is that a program power supply 10 (or 9) is connected to the power supply terminal to which no voltage is applied. Set Ov to the output voltage value of the program power supply 10 (or 9) that does not apply this voltage a
If there is a short circuit between the VTT power supply and the VER power supply, the outputs of the program power supply 9 (or 10) whose output voltage value is set to voltage e and the program power supply 10 (or 9) whose output voltage value is set to Ov will be short-circuited. The program power supply 10 (or 9) that has set Ov will no longer be able to control Ov output,
This function is the same as when the voltage source 5 with current clamp function shown in FIG. 1 is disconnected by the switch 6.

According to this embodiment, in addition to the effects of the embodiment shown in FIG. 1, the measurement circuit can be configured using only the program power supply, so that it is possible to use a device that supplies power to a semiconductor circuit under test using the program power supply, such as a semiconductor circuit testing device. This has the advantage that power supply short circuit inspection can be performed without adding a special measurement circuit.

〔Effect of the invention〕

According to the present invention, a power supply short circuit test can be performed by applying a voltage to the power supply terminal of the semiconductor circuit under test and checking whether the voltage is applied normally and whether the power supply terminal to which no voltage is applied is Ov. , compared to the conventional judgment based on resistance values, there is no need to determine the resistance values between the power supply terminals of a normal circuit and between the power supply and ground terminals in advance, and the difference between the resistance value of a normal circuit and the resistance value at the time of a short circuit is not necessary. This has the effect of detecting short circuits regardless of their size.

Furthermore, even if there is a power supply short circuit in the semiconductor circuit under test, the applied voltage is set within a range where the semiconductor element maintains the cut-off state, and the short circuit current is limited by the current limiting function of the voltage source, so the semiconductor circuit under test This also has the effect of minimizing damage to the semiconductor circuit under test and allowing repair of the semiconductor circuit under test.

[Brief explanation of drawings]

FIG. 1 is a prescribed circuit diagram of one embodiment of the present invention, and FIG.
FIG. 3 is a diagram illustrating a short circuit test result using the measurement circuit shown in FIG. 3. FIG. 3 is a measurement circuit diagram when the measurement circuit shown in FIG. 1... Semiconductor circuit under test, 2... Ground (Vcc)
terminal. 3...VTT power supply terminal, 4...v0 power supply terminal. 5... Voltage source with current clamp function, 6... Switch, 7, 8... Voltmeter, 9
．． 10...Program power supply.

Claims (1)

[Claims] 1. Sequentially apply a voltage within a range that allows the semiconductor element to maintain a cut-off state to one or more types of power supply terminals of a circuit composed of semiconductor elements using a voltage source with a current clamp function. A power supply short-circuit inspection method for a semiconductor circuit, comprising: measuring the voltage at a power supply terminal of each power supply type at the time of application.