JPH11183548A - Ic connection testing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a testing method wherein, with no complex IC internal circuit or multiple external terminals required, each IC mounted on a substrate is tested separately for connection test with higher precision than a method using a single power source. SOLUTION: A closed circuit comprising a power source 4 to IC2, a power source terminal 21 to transistor, to an output terminal 23, to) bonding wire to IC3 (an input terminal 32 to a protective diode, to a power source terminal 31), to a power source 5, is formed. Then, two power source voltages are adjusted to cause a voltage difference in the closed circuit. With a closed circuit between two power sources connected correctly, a constant leak current is generated, so connection state is confirmed based on the change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying an electric signal to a closed circuit in which an electronic component such as a semiconductor element, a switch, and a power supply is connected using a metal conductor such as solder or a connector inside an electronic computer. More particularly, the present invention relates to a method of testing a connection between an integrated circuit (hereinafter abbreviated as IC) mounted on a substrate and a substrate wiring.

[0002]

2. Description of the Related Art Conventionally, on a board mounted on a computer such as a computer, a connection test for confirming a connection between an IC mounted on the board and a wiring is indispensable due to the diversification and high density of mounting. It is.

As an example of such a connection test method, a brief description will be given of an “evaluation semiconductor integrated circuit and a test method using the same” described in JP-A-7-84008.

In the prior art, in an IC,
It is an object of the present invention to independently supply a power supply voltage to one functional circuit block, detect a current consumption, and evaluate the current consumption.

As shown in FIG. 6, a plurality of circuit blocks having different functions are formed on an IC chip, and a power supply voltage input terminal of the circuit block is not connected to an internal power supply wiring common to each circuit block. Connect to dedicated electrode pads provided on the chip. Thus, the power supply voltage can be freely supplied to the circuit block independently via the electrode pad.

By supplying a power supply voltage to only one circuit block via a current detector to the IC having a plurality of circuit blocks having different functions from each other,
The current consumed only by this circuit block is measured. Thus, the operating current and the non-operating current are measured independently for one circuit block. Therefore, this circuit block can be evaluated independently of other circuit blocks.

If a large abnormal current flows through one of the circuit blocks, which may adversely affect other normal circuit blocks, the power supply voltage is not supplied to the abnormal circuit block, so that accurate operation can be achieved. Evaluation can be performed.

[0008]

Such a prior art IC connection test method requires dedicated electrode pads and external terminals for each circuit block inside the IC in order to carry out the method. Therefore, when the number of circuit blocks inside the IC increases, the number of dedicated pads and the number of external terminals increase in proportion to the increase, and wiring and terminal wiring on the IC chip become complicated. As a result, an increase in the surface area of the IC chip and an increase in cost due to an increase in the number of steps for evaluating the circuit block are inevitable.

Further, when applying a conventional IC connection test to a substrate on which a plurality of ICs are mounted and wired, a test is performed for each circuit block inside each IC, which requires a large number of man-hours. Have to spend. In addition, it is extremely inefficient to provide an electrode pad and an external terminal dedicated to a circuit block test in addition to a common power supply line inside the IC for all the ICs mounted and wired on the board, and it is extremely inefficient. There is a risk that the layout will be greatly affected.

SUMMARY OF THE INVENTION An object of the present invention is to provide a test method capable of performing an inexpensive, quick and accurate connection test of an IC mounted and wired on a substrate.

Further, according to the present invention, each of the mounted ICs can be individually tested on the board without requiring a complicated IC internal circuit or a large number of external terminals, and the accuracy is higher than the method using a single power supply. The purpose is to provide a test method that can perform a connection test.

More specifically, the present invention utilizes a high impedance function (hereinafter referred to as HI-Z) provided in advance at an output terminal and an input / output terminal of an IC to determine the direction of a leak current, thereby providing It is an object of the present invention to provide an IC connection test method capable of performing a connection test of an arbitrary mounted and wired IC.

The HI-Z is a function for setting a plurality of ICs that exchange data with each other via a common bus in order to disconnect an IC irrelevant to the data from the common bus. As a result, it is possible to invalidate the output signal from the bidirectional (input / output) terminal or output terminal of an arbitrary IC or not to output the signal itself.
Most of C are standard.

[0014]

According to the present invention, there is provided an IC connection test method, comprising: a first-stage IC mounted on a substrate; a second-stage IC mounted on the substrate and connected to the first-stage IC;
C and a ground line extending from the rear-stage IC to provide a ground outside the substrate, and a first and a variably-adjustable first line and a variably-adjustable line that are individually connected to the front-stage IC and the rear-stage IC and supply an arbitrary voltage to each IC. An output buffer that has a second power supply and is provided in the preceding IC and causes a current supplied from the first power supply to flow out of an output terminal; and a current that is provided in the subsequent IC and flows in from an input terminal. In a closed circuit configured by connecting an input buffer that supplies the second power to the first power supply, different voltages are set for the first and second power supplies, and a leakage current generated by the voltage difference is set. It is characterized by measuring.

Still further, according to the present invention, in addition to the above configuration, the semiconductor device further comprises an external terminal drawn out of the substrate from a line connecting the output buffer of the pre-stage IC and the input buffer of the second IC. Any one of the pre-stage IC and the post-stage IC is set to high impedance to interrupt the current, and the external terminal and the IC not set to high impedance
And measuring a leakage current generated by a voltage difference between a power supply connected to an IC not set to the high impedance and the external terminal in a closed circuit formed between power supplies connected to the IC. And

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, two ICs 2 and 3 are mounted on a substrate 1. Power supplies 4 and 5 are connected to power supply terminals 21 and 31 of both ICs, respectively.
Any voltage can be applied to each IC. Both I
C is connected between the signal terminals 23 and 32 by a bonding wire, and is separately grounded by GND outside the substrate.

The IC 2 includes an input buffer 6, an internal logic circuit 8, and an output buffer 7. These components are interconnected by bonding wires, receive a voltage supply from the power supply 4 described above, and are grounded by GND.

As shown in FIG. 2, the output buffer 7
With one transistor 11 and two protection diodes 10, current can flow out only from the output terminal 23. Also,
Similarly, the input buffer can allow the current input from the input terminal 22 to flow out only to the power supply terminal 21 by the two protection diodes 10 and the transistor 11. Since the configuration of IC3 is the same as that of IC2, the description is omitted.

Next, the operation of the IC connection test method of the present invention will be described step by step.

The power supply voltages of the two ICs are set so that the voltages of the power supplies 4 and 5 are equal, and the voltage applied to the substrate input terminal is set so that "H" is output from the signal terminal of the IC2. Then, the current consumption (power supply current) of the substrate 1 in this state is measured.

At this time, between power supply 4 and power supply 5, power supply 4 → IC2 (power supply terminal 21 → transistor 11 → output terminal 23 →) bonding wire → IC3 (input terminal 32)
A closed circuit of → protection diode 10 → power supply terminal 31) → power supply 5 is formed. This is shown in FIG. At this stage, since the two power supply voltages are equal, no leak current occurs between the two power supplies in the closed circuit.

Subsequently, the two power supply voltages are adjusted to create a voltage difference in the closed circuit. At this time, if the voltage difference is too large, an overcurrent may occur and the buffer may be destroyed, so that the voltage of the power supply 4 = 5.
0 V and the voltage of the power supply 5 are set to 4.5 V. Then, the input terminal 22 that outputs “H” from the output terminal 23
Set the applied voltage to.

When the closed circuit between the two power supplies is correctly connected, that is, when there is no abnormality in the connection between the two ICs, a constant leak is caused by the voltage difference through the path indicated by the thick arrow in FIG. An electric current is generated. Since the current consumption of the substrate 1 at this time includes a leak current between the two power supplies, the current consumption fluctuates from the previously measured current consumption value. By reading this change, the connection state of the two ICs mounted on the board 1 is confirmed.

Next, a second embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 4, two I
The external terminal 12 is drawn out from the bonding wire between C. Also, as in the first embodiment, two
A power supply for the system is arranged, and the power supply 4 is connected to the power supply terminal of the IC 2 and the power supply 5 is connected to the power supply terminal of the IC 3. The internal logic circuit 8 in each IC is provided with HI-Z setting terminals 24 and 34 for setting the HI-Z function.

In order to confirm the connection between the power supply 4 and the external terminal 12, the voltages of the power supply 4 and the power supply 5 are adjusted to the same value.
In this embodiment as well, both are adjusted to 5.0 V as in the first embodiment. Then, a signal is input from the HI-Z setting terminal 34 to operate the HI-Z function of the IC 3 and to disconnect the connection of the IC 2 from the signal.
Input from the HI-Z setting terminal 24. Thus, the power supply 5
During the connection test from to the external terminal 12, the power supply voltage of the IC 2 (power supply 4) and the signal terminal HI-Z are maintained and are not subjected to the test.

By setting the signal terminal to HI-Z, between the power supply 5 and the external terminal 11, the external terminal 12 → IC3
(Input terminal 32 → protection diode 10 → power supply terminal 31)
→ A closed circuit as shown in FIG.

After setting the signal terminal to HI-Z, the power supply 4
Is set to 0 V, and an applied voltage is applied from an external terminal. At this time, if the voltage applied to the external terminal is too high, the buffer may be destroyed due to the occurrence of an overcurrent. Therefore, it is desirable to set the voltage in the range of (0 V <voltage difference <0.5 V). .

If the connection between the power supply 5 and the external terminal 12 is normal, a constant leak current is generated in the path indicated by the thick arrow in FIG. By measuring the leak current, the connection between the IC 3 and the external terminal 12 can be confirmed.

On the other hand, when the connection test of the power supply 4 to the external terminal 12 is performed, the two power supply voltages that have been set are exchanged, and a signal for setting the HI-Z function of the IC 3 is sent to the HI-Z setting terminal 34. input. Thereafter, as in the case between the power supply 5 and the external terminal 12, the voltage of the power supply 4 is set to 0, a leak current is measured by applying a voltage of about 0.5 V from the external terminal 12, and the connection between the IC 2 and the external terminal 12 is performed. Check.

[0032]

According to the present invention, a plurality of I / Os mounted and wired on a substrate using a plurality of systems of power supplies supplied to the substrate.
By applying an arbitrary voltage difference to the closed circuit formed by C and measuring a leak current generated at this time, an arbitrary IC can be obtained.
Can be individually tested, and a connection test with higher accuracy can be realized as compared with the method using a single power supply.

Further, according to the present invention, the direction of the above-described leakage current is set by using the HI-Z function of the output terminal and the input / output terminal of the IC, so that any of the components mounted and wired on the substrate can be set. An IC connection test can be set and executed in more detail. Most current ICs are provided with HI-Z functions of output terminals and input terminals, and there is no need to change the specifications of the IC, and it is only necessary to add a power supply system to the board. Thereby, a very inexpensive connection test can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a substrate used in an IC connection test method of the present invention.

FIG. 2 is an IC mounted on a substrate according to the first embodiment of the present invention;
FIG. 2 is a block diagram showing an internal configuration of the device.

FIG. 3 is a diagram showing a flow of a leak current in the first embodiment of the connection test of the present invention.

FIG. 4 is a block diagram showing a second embodiment of the substrate used in the IC connection test method of the present invention.

FIG. 5 is a diagram showing a flow of a leak current in a second embodiment of the connection test of the present invention.

FIG. 6 is a schematic block diagram of an IC used in a conventional IC (integrated circuit) connection test method.

[Explanation of symbols]

 Reference Signs List 1 substrate 2, 3 IC 4, 5 power supply 6 input buffer 7 output buffer 8 internal logic circuit 10 protection diode 11 transistor 12 external terminal 21, 31, power supply terminal 22, 32 input terminal 23 output terminal 24, 34 HI-Z setting terminal

Claims (3)

[Claims] 1. A pre-stage IC mounted on a substrate, and a post-stage IC mounted on the substrate and connected to the pre-stage IC
And ground lines that are respectively pulled out from the pre-stage IC and the post-stage IC and provide a ground outside the substrate, and are individually connected to the pre-stage IC and the post-stage IC, respectively.
A variably adjustable first IC that supplies an arbitrary voltage to each IC
An output buffer that is provided in the preceding-stage IC and allows the current supplied from the first power source to flow out of the output terminal; and an output buffer that is provided in the subsequent-stage IC and flows in from the input terminal. In a closed circuit configured by connecting an input buffer for supplying a current to the second power supply, different voltages are set in the first and second power supplies, and a leakage current generated by the voltage difference is set. An IC connection test method characterized by measuring the following. 2. The semiconductor device according to claim 1, further comprising an external terminal drawn out of the substrate from a line connecting an output buffer of the preceding IC and an input buffer of the second IC. A closed circuit configured between the external terminal and a power supply connected to an IC for which high impedance has not been set, wherein one of the IC and the post-stage IC is set to high impedance to interrupt the current; An IC connection test method, comprising measuring a leak current generated by a voltage difference between a power supply connected to an unset IC and the external terminal. 3. The IC connection test method according to claim 1, wherein the voltage difference between the first power supply and the second power supply is made smaller than 0.5V.