JP2985895B2 - Test method for semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for testing a semiconductor device, which measures a forward voltage value of the semiconductor device and selects a device having a forward voltage higher than a specified value as a defective product.

[0002]

2. Description of the Related Art One of the characteristics of a diode in a semiconductor device is a forward voltage characteristic. This is a characteristic that a voltage drop occurs when a current flows in the forward direction of the PN junction of the diode, and the smaller the value, the smaller the power loss. Therefore, in general, a test is performed in the final step of a diode production line, and a diode having a specified value or more is selected as a defective product. FIG. 3 schematically shows an apparatus for testing the forward voltage. In the figure, a DC constant current source D. A forward current iF flows from C through a switch S to a diode D to be tested. Further, a voltmeter V is connected as shown in the figure to measure the forward voltage VF between the anode and the cathode of the diode D. Fig. 4
The square wave constant current of the forward current iF as shown in FIG.
Between t1 and S1, the switch S is closed to energize. The forward voltage VF generated at both ends of the diode D at this time is as shown in FIG.
As shown in (b), there are various types as shown in waveform 1, waveform 2, and waveform 3 depending on the type of the diode D under test.

The time when the forward voltage VF is measured is t01, which is a half time between t0 and t1. This t
Since the one which is lower than the specified value VF1 at the time point 01 is a good product, the diodes of the waveforms 1 and 2 are good products. on the other hand,
At time t01, the diode of waveform 3 has the specified value VF1
Higher, so it is sorted as defective. by the way,
A conductor is connected to the anode side and the cathode side of the semiconductor chip on which the PN junction of the diode D is formed, but if there is an incomplete part of the solder connection with this conductor, the following characteristics may be exhibited. It was revealed.

First, FIG. 4A shows actual numerical values. The time t0 to t1 is about 6 ms, and the forward voltage iF is 45A. The time point t01 in FIG. 4B is a point of about 3 ms. FIG. 4 (c) shows a diode which measured the forward voltage at time t01 of 3 ms after the energization of the diode D was started, and was a non-defective diode at a specified value VF1 or less. Some of the values exceed the specified value of VF1 during the end time t1 of the time. Even if such a diode D is considered to be a good product in this test, it clearly exceeds VF1 immediately before the time point t1 for some reason, so that the power loss in the forward direction becomes large in actual use, which is not preferable. There are various possible causes of such a unique forward voltage characteristic. For example, the imperfect solder connection described above is one of the causes. In any case, diodes having such characteristics must be sorted out as defective.

In the conventional method for testing a semiconductor device, since the test is performed by the method as shown in FIG. 3B, a unique forward voltage characteristic as shown in FIG. The indicated diode could not be sorted out as a defective product.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to reliably select a diode having a unique forward voltage characteristic as shown in FIG. It is an object of the present invention to provide a method for testing a semiconductor device which can be performed.

[0006]

According to a method of testing a semiconductor device of the present invention, a square-wave constant current is applied in a forward direction of a PN junction of a semiconductor device, and a forward voltage is measured at a predetermined time within an energization time. To determine whether the forward voltage value is higher or lower than the specified value,
In a semiconductor device test method for determining the quality of a semiconductor device, a forward voltage is measured at a time later than a half of a square wave constant current conduction time, and a forward voltage value at that time is larger than a specified value. High quality semiconductor devices are sorted out as defective products.

[0007]

FIG. 1 shows an embodiment of the present invention. In addition,
The basic configuration of the test apparatus is the same as that shown in FIG. The switch S is an electronic switching element, a control circuit for controlling the ON time of the switching element, a timing for measuring VF with the voltmeter V, a comparison circuit for comparing the measurement result with a specified value, and selecting good or defective products. Since the signal transmission circuit, the specific circuit of the DC constant current source, and the like are known circuits,
Illustration and explanation thereof are omitted.

From the above test equipment, t0 to t1 time 6 ms,
The square wave constant current shown in FIG.
Turn on electricity. The time when the forward voltage is measured is defined as t02. That is, the time t02 is set after the half of the time t0 to t1 and before the end time t1 of the energization time. As a result, a diode having a waveform 2 having a forward voltage value VF2 higher than the specified value VF1 can be selected as a defective product. On the other hand, the diodes of the waveforms 1 and 3 can be selected as non-defective products from the forward voltage value lower than the specified value VF2 as before.

Next, it is also possible to provide a time point for measuring VF at a time point t01 ahead of a half time point between t0 and t1. The prescribed forward voltage value in this case is set to have a relationship of VF1 <VF2. In this case, the measured values of the forward voltage characteristics of the diodes of waveforms 1 to 3 at times t01 and t02 are as shown in FIG. Thus, at both time points t01 and t02, VF1, V
By measuring F2 and removing those with a higher forward voltage value than the specified value at either time, it is possible to select only diodes with more uniform characteristics . Although the present embodiment has been described by taking a diode as an example, the present invention can be widely applied to an element for measuring a forward voltage having a forward characteristic.

[0010]

As described above, according to the method for testing a semiconductor device of the present invention, the VF measurement point is set after the middle point of the period during which the square wave constant current is applied, so that the semiconductor chip is soldered. The semiconductor device having a defect or the like can be surely selected as a defective product, so that only a highly reliable semiconductor device can be shipped.

[Brief description of the drawings]

FIG. 1 is a waveform chart showing a forward voltage characteristic in a semiconductor device test method of the present invention.

FIG. 2 is a waveform diagram of a square wave constant current flowing through a diode under test.

FIG. 3 is a schematic diagram showing a configuration of a test apparatus for implementing the present invention.

4A is a waveform diagram of a square wave constant current flowing through a diode under test in a conventional test method, and FIGS. 4B and 4C are waveform diagrams of forward voltage characteristics of each diode under test. .

FIG. 5 is a diagram showing a comparison with a set voltage value when a time point for measuring the forward voltage VF is set at time points t01 and t02.

[Explanation of symbols]

 iF Forward current VF Forward voltage VF1, VF2 Specified forward voltage value D Diode S Switch V Voltmeter D. C DC constant current power supply

Claims (1)

(57) [Claims] 1. A method in which a square wave constant current is applied in the forward direction of a PN junction of a semiconductor device, and a forward voltage is measured at a predetermined time within an energization time to determine whether the forward voltage value is higher or lower than a specified value. In the semiconductor device test method of judging and judging the quality of the semiconductor device, a forward voltage is measured at a time later than a half of an energizing time of a square wave constant current, and a forward voltage value at that time is defined. A method for testing a semiconductor device, wherein a semiconductor device having a higher value is selected as a defective product.