JP3396834B2 - IC connection test method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention supplies an electric signal to a closed circuit in which electric parts such as semiconductor elements, switches, and power supplies are connected inside a computer using a metal conductor such as solder or a connector. The present invention relates to a board configuration to be operated, and particularly to a connection test method between an integrated circuit (hereinafter abbreviated as IC) mounted on a board and board wiring.

[0002]

2. Description of the Related Art Conventionally, in a board mounted on an electronic computer such as a computer, a connection test for confirming the connection between the IC mounted on the board and the wiring is indispensable as the mounting is diversified and the density is increased. Is.

As an example of such a connection test method, an outline of "evaluation semiconductor integrated circuit and test method using the same" described in Japanese Patent Laid-Open No. 7-84008 will be briefly described.

In the prior art, inside the IC,
The purpose is to independently supply a power supply voltage to one functional circuit block, detect the consumption current, and evaluate the consumption current.

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

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

Further, when a large abnormal current flows in one of the circuit blocks and may adversely affect other normal circuit blocks, the power supply voltage is not supplied to the abnormal circuit block, so that it is accurate. Can be evaluated.

[0008]

In order to carry out this IC connection test method of the prior art, a dedicated electrode pad and an external terminal are required for each circuit block inside the IC. Therefore, when the number of circuit blocks inside the IC increases, the number of dedicated pads and external terminals also increases in proportion to this, and the wiring on the IC chip and the terminal wiring become complicated. As a result, an increase in the surface area of the IC chip and an increase in the number of circuit block evaluation steps inevitably increase costs.

Further, when the conventional IC connection test is to be applied on a board on which a plurality of ICs are mounted and wired, the test is carried out for each circuit block inside each IC, which requires a great deal of man-hours. Have to spend. Moreover, it is extremely inefficient to provide an electrode pad and an external terminal dedicated to the circuit block test to all the ICs mounted and wired on the board, in addition to the common power supply line inside the IC, and wiring on the board. There is also a risk that it will have a major impact on the layout.

An object of the present invention is to provide a test method capable of inexpensively, quickly and accurately performing a connection test of an IC mounted and wired on a substrate.

Further, according to the present invention, each IC mounted on the substrate can be individually tested without requiring a complicated IC internal circuit or a large number of external terminals, which is more accurate than the method using a single power source. The purpose is to provide a test method capable of conducting a connection test.

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

The HI-Z is a function that is set in a plurality of ICs that exchange data with each other via a common bus to disconnect the ICs unrelated 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 the output terminal of an arbitrary IC or to prevent the signal itself from being output.
Most of C are equipped as standard.

[0014]

An IC connection test method according to the present invention comprises a pre-stage IC mounted on a substrate, a post-stage IC mounted on the substrate and connected to the pre-stage IC, and the pre-stage C.
And a ground line which is respectively drawn from the rear stage IC and which provides a ground to the outside of the substrate, and first and second variably adjustable devices which are individually connected to the front stage IC and the rear stage IC and supply arbitrary voltages to the respective ICs. An output buffer having two power supplies and provided in the preceding-stage IC for causing a current supplied from the first power supply to flow out from an output terminal;
The current flowing from the input terminal is provided in the C
In a closed circuit configured by connecting an input buffer that supplies power to the power source of
Both potentials are set to be higher than the potential of the second power source, and the leak current generated by the potential difference is measured.

Further, in addition to the above structure, the present invention has an external terminal drawn out of the substrate from a line connecting the output buffer of the preceding IC and the input buffer of the second IC, An IC in which either the front-stage IC or the rear-stage IC is set to high impedance to cut off current and the high impedance is not set to the external terminal.
In a closed circuit formed between power supplies connected to the IC, a leak current generated by a voltage difference between the power supply connected to the IC in which the high impedance is not set and the external terminal is measured. And

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An 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 the power supply terminals 21 and 31 of both ICs,
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 a GND outside the substrate.

The IC 2 is composed of an input buffer 6, an internal logic circuit 8 and an output buffer 7. These constituent elements are connected to each other by a bonding wire, receive a voltage supply from the power source 4 and are grounded by GND.

The output buffer 7, as shown in FIG.
With one transistor 11 and two protection diodes 10, current can only flow out of the output terminal 23. Also,
Similarly, in the input buffer, the two protection diodes 10 and the transistor 11 allow the current input from the input terminal 22 to flow only to the power supply terminal 21. Since the configuration of IC3 is the same as that of IC2, the description will be 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 consumption current (power supply current) of the substrate 1 in this state is measured.

At this time, between the power supply 4 and the power supply 5, the power supply 4 → IC2 (power supply terminal 21 → transistor 11 → output terminal 23 →) bonding wire → IC3 (input terminal 32)
-> Closed circuit of protection diode 10-> power supply terminal 31)-> power supply 5 is formed. The situation is shown in FIG. At this stage, since the two power supply voltages are equal, a leak current between the two power supplies does not occur in the closed circuit.

Subsequently, the two power supply voltages are adjusted to generate 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. Therefore, the voltage of the power supply 4 = 5.
The voltage of the power source 5 is set to 0V and the voltage of the power source 5 is set to 4.5V. 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 properly connected, that is, when there is no abnormality in the connection between the two ICs, due to the voltage difference, there is a constant leak through the path indicated by the thick arrow in FIG. Electric current is generated. Since the current consumption of the substrate 1 at this time includes the leak current between the two power supplies, it varies from the value of the current consumption measured previously. By reading this change, the connection state of the two ICs mounted on the substrate 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's on the substrate 1 are
The external terminal 12 is pulled out from the bonding wire between C. In addition, as in the first embodiment, the substrate 1
A power supply for the system is arranged, and the power supply 4 is connected to the power supply terminal of the IC2 and the power supply 5 is connected to the power supply terminal of the IC3. 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 source 4 and the external terminal 12, the voltages of the power source 4 and the power source 5 are adjusted to the same value.
In this embodiment, both are adjusted to 5.0V as in the first embodiment. Then, a signal is input from the HI-Z setting terminal 34 to activate the HI-Z function of the IC3 and to disconnect the connection of the IC2.
Input from the HI-Z setting terminal 24. Thus, power supply 5
During the connection test between the external terminal and the external terminal 12, the power supply voltage of the IC 2 (power supply 4) and the HI-Z of the signal terminal are maintained and kept out of the test target.

By setting the signal terminal to HI-Z, the external terminal 12 → IC3 is provided between the power source 5 and the external terminal 11.
(Input terminal 32 → protection diode 10 → power supply terminal 31)
→ A closed circuit called the power supply 5 as shown in FIG. 7 is formed.

After setting the signal terminals 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 large, the buffer may be destroyed due to the occurrence of overcurrent. Therefore, it is desirable to set this in the range of (0V <voltage difference <0.5V). .

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 this leak current, the connection between the IC 3 and the external terminal 12 can be confirmed.

On the contrary, when the connection test from the power source 4 to the external terminal 12 is carried out, a signal for exchanging the two set power source voltages and setting the HI-Z function of the IC 3 is sent to the HI-Z setting terminal 34. input. Similarly to the case between the power source 5 and the external terminal 12, the voltage of the power source 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. To confirm.

[0032]

According to the present invention, a plurality of I's mounted and wired on a substrate are supplied by using a plurality of power sources for the substrate.
An arbitrary voltage difference is applied to the closed circuit formed by C, and the leak current generated at this time is measured to determine an arbitrary IC.
It is possible to individually test the above, and it is possible to realize a highly accurate connection test as compared with the method using a single power source.

Further, according to the present invention, the HI-Z function of the output terminal and the input / output terminal of the IC is utilized to set the direction of the above-mentioned leakage current, so that the arbitrary mounting and wiring on the substrate is possible. The IC connection test can be set and executed in more detail. Most current ICs are provided with HI-Z functions for output terminals and input terminals, and there is no need to change the specifications of the ICs, and only a power supply system needs to be added to the board. This makes it possible to realize a very inexpensive connection test.

[Brief description of 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 the substrate according to the first embodiment of the present invention.
3 is a block diagram showing the internal configuration of FIG.

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

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

FIG. 5 is a diagram showing a leak current flow 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]

1 substrate 2,3 IC 4, 5 power supply 6 input buffer 7 Output buffer 8 Internal logic circuit 10 Protection diode 11 transistors 12 external terminals 21, 31 Power supply terminal 22, 32 input terminals 23 output terminals 24, 34 HI-Z setting terminal

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-7-84008 (JP, A) JP-A-5-190637 (JP, A) JP-A-9-260595 (JP, A) JP-A-8- 43494 (JP, A) JP 4-288900 (JP, A) JP 9-130223 (JP, A) JP 5-302951 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01R 31/02 G01R 31/26-31/3193

Claims (3)

(57) [Claims] 1. A front-stage IC mounted on a substrate, a rear-stage IC mounted on the substrate and connected to the front-stage IC, and drawn out from the front-stage IC and the rear-stage IC respectively, and grounding is provided outside the substrate. A grounding wire, and individually connected to the front IC and the rear IC,
Adjustable first variable voltage supply to each IC
And an output buffer having a second power supply, the output buffer being provided in the front stage IC for flowing out a current supplied from the first power source from an output terminal, and being provided in the rear stage IC, flowing in from an input terminal. In a closed circuit configured by connecting an input buffer that supplies a current to the second power supply, the potential of the first power supply is higher than the potential of the second power supply.
Both potentials are set so that the leak current generated by the potential difference is measured, and an IC connection test method is characterized. 2. The apparatus 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. In a closed circuit configured to set either the IC or the latter-stage IC to high impedance to interrupt current, and to connect the external terminal and a power source connected to an IC not set to high impedance, the high impedance An IC connection test method comprising measuring a leak current generated by a voltage difference between a power supply connected to an IC that is not set 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 smaller than 0.5V.