JP2002181892A - Method and device for defect search for mounted substrate, and recording medium recorded with control program therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically search a function-defective portion or a production-defect portion of a mounted substrate by a simple device in a short time, without detail circuit information. SOLUTION: Each propagation signal of a measurement network in a nondefective substrate, and each propagation signal an inspection network in an objective substrate corresponding to the measurement network are measured in a measuring point in each one site to compare a measured result in the inspection network with a result in the measurement network. Another one measuring point within the inspection network is measured in order when a difference of a set level or more does not exist, the inspection network is determined as a defective propagation network when the difference of the set level or more exists, the inspection network is is determined as a normal network when the difference of the set level or more is not detected in all the measuring points within the inspection network, and another defective propagation network is searched while tracing in order, using an electronic component connected to the defective propagation network as a repeating point, so as to extract a defective network in the origin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for searching for a defect on a mounting board on which electronic components such as ICs (semiconductor integrated circuits) are mounted, a defect searching device, and a recording medium on which a control program is recorded. The present invention relates to a method of searching for a defective board, a method of searching for a defective net, a method of searching for a defective net, and a recording medium storing a control program therefor.

[0002]

2. Description of the Related Art Causes of defective nets on a mounting board include disconnection or short circuit of an electronic circuit, manufacturing defects such as open or short at a terminal junction of a mounted electronic component, or failure of an electronic component. . As a method of detecting such a defective net, there is generally a method of performing an in-circuit test or an appearance inspection in a manufacturing process of a mounting board, but various other methods have been improved and proposed.

For example, conventionally, there is a method of searching for a defective portion by analyzing the timing of generation of a pulse signal in a digital IC mounted on a substrate to be inspected. A measuring instrument for evaluating a pulse waveform such as a spectrum analyzer is used. As a technique for performing a short-circuit fault test on a printed circuit board, Japanese Unexamined Patent Application Publication No. 7-55894 discloses a binary bisection pattern that is at least once mutually exclusive logic in a combination of logics between nets on a printed circuit board. A printed circuit board test apparatus is disclosed which supplies a plurality of input patterns so as to obtain a fail of a binary bisection pattern so that a shorted net can be found.

[0004]

However, a signal analyzer such as a logic analyzer takes a long time to analyze a pulse signal. Furthermore, this signal analysis device strictly analyzes the pulse signal, but if the purpose is simply to detect a defective net, the pulse number and voltage value of the defective substrate are measured without using the signal analysis device. By comparing with a non-defective substrate, a defective net can be easily detected. The printed circuit board test apparatus proposed in Japanese Patent Application Laid-Open No. 7-55894 is for inspecting a short circuit of an electronic circuit. Therefore, a mounting board having a defective portion other than a short circuit could not be extracted as a defective board. Furthermore, with the recent miniaturization and high-density of circuits on a mounting board, it becomes difficult to probe all terminals and test pads, and a large amount of time is required for one board. It was virtually impossible to detect everything. In addition, as another technique of the device for searching for a defect of a mounting board, for example,
There is known an apparatus for searching for a malfunction of an electronic component mounting board described in JP-A-263571.

[0005] This device for searching for a functional failure of an electronic component mounting board performs a task of searching for a defective net by performing advanced analysis such as synchronization and waveform comparison using expensive measurement equipment such as a function board tester and a signature analyzer. Increases the search cost,
There is a problem that it takes time to acquire and analyze data. The applicant of the present application has proposed a method of inspecting a mounting board for failure in a short time to identify a defective portion of a mounting board on which an IC and an electronic component are mounted, for example, Japanese Patent Application Laid-Open No. H11-3376.
In Japanese Patent Application Publication No. 26, a non-defective board and a board to be inspected are individually operated by a test program created in advance, a net or a signal of the selected net is measured using a measuring means, and a first measurement result is stored. Step, a second step of comparing the measurement results of the non-defective substrate and the substrate to be inspected, and listing defective propagation nets having a difference equal to or greater than a set level, and Going back to the IC connected to the fault propagation net by the output terminal or bidirectional terminal, this IC is used as a relay point, and any fault propagation net connected to another output terminal or bidirectional terminal at this relay point is next. The present invention proposes a defect inspection method including a third step of sequentially going back as a search path and extracting a defective net of a source flow from the list of the defective propagation nets.

Accordingly, the present invention has been made in view of such circumstances, and a main object of the present invention is to reliably detect a defective portion of a mounting board in a short time by using an easily obtained device. It is an object of the present invention to provide a mounting board defect search method, a defect search device, and a recording medium on which a control program thereof is recorded.

[0007]

According to a first aspect of the present invention, there is provided a method for searching for a defective portion of a mounted substrate, comprising the steps of: comparing a non-defective substrate on which electronic components are mounted with a target substrate; A defect search method for a mounting board, wherein the non-defective board is operated, and when measuring a propagation signal in each of the measurement nets of the non-defective board, a first measurement of any one measurement point in the measurement net is performed. Process and
Operate the target substrate, measure the propagation signal in each of the test nets of the target substrate corresponding to the measurement net of the non-defective substrate at any one measurement point in the test net, the measurement result of the test net And a measurement result of the measurement net of the non-defective board corresponding to the inspection net, and if no difference equal to or greater than the set level is detected, another one of the measurement points in the inspection net is sequentially measured. If a difference equal to or higher than the level is detected, the test net is extracted as a failure propagation net. If no difference equal to or higher than the set level is detected at all the measurement points in the test net, the test net is regarded as normal. A second step of extracting the net as a net, and, with respect to the fault propagation net extracted in the second step, the fault propagation net and an output terminal or a bidirectional Going back to the electronic component connected by the child, the electronic component is used as a relay point, and any defective propagation net connected to the output terminal or bidirectional terminal of another electronic component at the relay point is used as the next search path. And a third step of sequentially extracting the defective net of the headwater.

According to a second aspect of the present invention, in the first and second steps, the propagation signal causes the non-defective substrate and the electronic circuit of the target substrate to operate according to a test program. It is characterized by being generated by

In a third aspect of the present invention, in the first and second steps, the non-defective substrate and the target substrate can control the propagation signal by the substrate alone. The propagation signal is generated by supplying power to the electronic circuit on the non-defective substrate and the target substrate.

According to a fourth aspect of the present invention, in the first and second steps, each signal measurement of the measurement net on the non-defective substrate and the inspection net on the target substrate is performed by a pulse number. , By measuring at least one of a frequency and a voltage.

According to a fifth aspect of the present invention, in the method for searching for a defect in a mounting board, in the first and second steps, each voltage measurement of the measurement net on the non-defective board and the test net on the target board is performed by the propagation. The measurement is performed by measuring at least one of the highest voltage, the lowest voltage, and the average voltage of the signal.

According to a sixth aspect of the present invention, in the method for detecting a failure of a mounting board, in the first and second steps, the time for measuring the propagation signal is set at a measurement point.
A certain time from the start of the test program, a certain time at an arbitrary timing during the execution of the test program, a time from the start of the test program until a failure occurs, and a time until the number of pulses from the start of the test program reaches a preset value. , Or one cycle of the test program.

According to a seventh aspect of the present invention, in the method for detecting a failure of a mounting board, the determination of a difference in a propagation signal in the second step is performed twice for the number of pulses, frequency, or voltage in the inspection net and the measurement net. The measurement is performed based on the ratio or difference of the measured values.

According to a still further aspect of the invention, there is provided a method of searching for a failure propagation net in the third step, wherein the search for the failure propagation net in the third step comprises connecting the failure propagation net to an output terminal.
And if there is another IC connected by a bidirectional terminal, the IC goes back to the IC connected to the output terminal, the IC is used as a relay point, and the IC is connected to the output terminal of another IC at the relay point. When there is a fault propagation net connected to the propagation net and the bidirectional terminal, the fault propagation net connected to the output terminal is traced back as the next search path.

According to a ninth aspect of the present invention, in the third step, if the search goes back to the already found fault propagation net from another route in the third step, the search is terminated there. It is characterized by the following.

According to a tenth aspect of the present invention, in the third step, in the third step, when there is no fault propagation net that goes back to the input side, the finally reached fault propagation net is regarded as a fault net. It is characterized by the following.

In a third aspect of the present invention, in the third step, a closed loop is formed between the plurality of fault propagation nets, and any fault propagation net on the closed loop is formed. On the other hand, when there is no other fault propagation net that goes back to the input side, all the fault propagation nets on the closed loop are set as fault nets.

According to a twelfth aspect of the present invention, there is provided an apparatus for searching for a defect in a mounted board according to a test program for generating each propagation signal in a measurement net of a good board and an inspection net of a target board. A test program control unit for operating the electronic circuit, a probe for detecting each propagation signal of the measurement net of the good board and the inspection net of the target board, and, based on the output of the probe, each propagation signal of the measurement net of the good board. Measure at any one measurement point, measure the propagation signal in each of the test nets of the target board corresponding to the measurement net of the good board, measure at any one measurement point in the test net, And the measurement result of the measurement net of the non-defective board corresponding to the inspection net, and compared with the set level If no difference is detected, another one of the measurement points in the inspection net is sequentially measured.On the other hand, if a difference equal to or higher than a set level is detected, the inspection net is extracted as a failure propagation net, and If no difference greater than the set level is detected at all the measurement points in the inspection net, the inspection net is extracted as a normal net and traced back to the component connected to the defective propagation net by an output terminal or a bidirectional terminal. And a control unit for sequentially going back to another defective propagation net as a next search path with the component as a relay point and extracting a defective net of a headwater flow.

In a thirteenth aspect of the present invention, in the defect search apparatus for a mounting board, the control unit may be configured to perform the search based on the propagation signal, the extraction signal of the defect propagation net, and the retrospective information of the search path for the defect propagation net. The operation of the test program control unit and the probe is controlled.

Further, a defect search apparatus for a mounting board according to the invention of claim 14 is provided with a function that the non-defective board and the target board include a control unit including a microprocessor and can control the propagation signal by the board alone. The propagation signal is generated by supplying power to the electronic circuit on the non-defective substrate and the target substrate.

According to a fifteenth aspect of the present invention, there is provided the defect detection apparatus for a mounting board, wherein the signal measurement of the measurement net on the non-defective substrate and the signal measurement of the inspection net on the target board are performed by at least one of the number of pulses, the frequency and the voltage The measurement is performed by measuring

In a preferred embodiment of the present invention, the measuring means for measuring the voltage includes the maximum voltage of the propagation signal for the measurement net of the non-defective substrate and the search net of the target substrate. , At least one of the lowest voltage and the average voltage is measured.

Further, in the apparatus for detecting a failure of a mounting board according to the present invention, the time for measuring the propagation signal is set to a predetermined time from the start of a test program at a measurement point, at an arbitrary timing during execution of the test program. A fixed time, a time from the start of the test program to the occurrence of a defect, a time from the start of the test program until the number of pulses reaches a preset value, or a time of one cycle of the test program; It is characterized by doing.

Further, in the defect search apparatus for a mounting board according to the invention of the eighteenth aspect, the determination of the difference between the propagation signals is based on a ratio or a difference between two measurement values of the pulse number, frequency or voltage measurement value. It is characterized by being performed.

According to a nineteenth aspect of the present invention, in the defect search apparatus for a mounting board, the search for the defective net is performed by using an IC connected to the defect propagation net by an output terminal and another IC connected by a bidirectional terminal. In some cases, the IC is connected to the output terminal, the IC is used as a relay point, and the fault propagation net connected to the output terminal of another IC and the fault propagation net connected to the bidirectional terminal at the relay point. In the case where there is, the fault propagation net connected to the output terminal is traced back as the next search path.

According to a twentieth aspect of the present invention, in the defect search apparatus for a defective board, if the search for the defective net has been traced back from another path to the already found defective propagation net, the search is performed there. It is characterized by terminating.

According to a twenty-first aspect of the present invention, in the defect search apparatus for a mounting board, when there is no defect propagation net that goes back to the input side in the search for the defect net, the failure propagation net that has finally arrived is determined to be the defect net. It is characterized by doing.

According to a twenty-second aspect of the present invention, in the defect search apparatus for a mounting board, in the search for the defective net, a closed loop is formed between the plurality of defect propagation nets, and any defect on the closed loop is formed. In the case where there is no other fault propagation net that goes back to the input side with respect to the propagation net, all the fault propagation nets on the closed loop are regarded as fault nets.

A recording medium on which a control program according to the invention of claim 23 is recorded is a probe for operating a non-defective substrate by a test program and detecting each propagation signal of a measurement net of the non-defective substrate and an inspection net of a target substrate. ,
And controlling a test program control unit that stores a test program for operating the non-defective substrate and the electronic circuit on the target substrate to generate the propagation signal,
When measuring the propagation signal in each of the measurement nets of the non-defective board, a procedure of measuring any one measurement point in the measurement net, operating the target board, and controlling the probe and the test program control unit Then, a propagation signal in each of the test nets of the target board corresponding to the test net of the good board is measured at any one measurement point in the test net, and the measurement result of the test net and the test net are measured. Is compared with the measurement result of the measurement net of the non-defective substrate, and if no difference equal to or greater than the set level is detected, another one measurement point in the inspection net is sequentially measured. If detected, the inspection net is extracted as a failure propagation net, and further at all measurement points in the inspection net. If a difference equal to or higher than a certain level is not detected, a procedure for extracting the inspection net as a normal net, and a procedure for connecting the extracted fault propagation net to the fault propagation net via an output terminal or a bidirectional terminal. Going back to the component side, the electronic component is used as a relay point, and at the relay point, any fault propagation net connected to the output terminal or bidirectional terminal of another electronic component is sequentially traced back as the next search path, and the source net fault net And a program for executing the procedure for extracting the information.

[0030]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. In the method for searching for a defect in a mounting board according to the present invention, first, when a good board is operated and a propagation signal is measured in each of the measurement nets of the good board, any one of the measurement points in the measurement net is measured. Operate the board, when measuring the propagation signal in each of the test nets of the target board corresponding to the measurement net of the non-defective board, measure any one measurement point in the test net, the measurement result of the test net and Compare the measurement result with the measurement net of the non-defective substrate corresponding to the inspection net, and if no difference equal to or higher than the set level is detected, measure another one measurement point in the inspection net sequentially, and if the difference equal to or higher than the set level is detected, If detected, the inspection net is extracted as a failure propagation net.

On the other hand, if no difference equal to or greater than the set level is detected at all the measurement points in the test net, the test net is extracted as a normal net, and the extracted fault propagation net and the output of the fault propagation net are output. Back to the electronic component side connected by the terminal or the bidirectional terminal, and using the electronic component as a relay point, any fault propagation net connected to the output terminal or the bidirectional terminal of another electronic component at the relay point is next. It goes back as the search route and extracts the defective net of the headwater.

In the measurement of the propagation signal in each of the measurement nets of the non-defective substrate, any one measurement point in the measurement net is measured. On the other hand, in the measurement of the propagation signal in each of the test nets of the target board, the measurement and comparison judgment are performed while changing the measurement point until a difference of the measurement net of the non-defective board corresponding to the test net and the set level or more is detected. Accordingly, a net failure can be detected with high accuracy, and the measurement time can be reduced as compared with the case where all measurement points (terminals, wiring, through holes, etc.) are measured.
Further, if the failure propagation net is extracted in advance from the inspection nets on the target board, the failure search is not performed for other normal nets, so that the failure net can be efficiently detected. Also have.

In the present invention, a non-defective substrate and a target substrate are activated by a test program used in a function test or the like, and a propagation signal is measured. Can be reproduced and measured. Further, in the present invention, when the good board and the board to be searched as the target board can control the propagation signal by the board alone, the propagation signal is supplied to the electronic circuit on the good board and the board to be searched. For example, even for a board having a function of controlling a signal on a board alone by mounting a CPU, a search for a defective net and a defective point can be performed.

Further, in the present invention, in order to determine whether or not the propagation signals of the non-defective substrate and the substrate to be searched are completely the same, the number of pulses and the number of pulses can be determined without performing detailed signal analysis and collecting detailed data. By measuring measurable data with simple measuring equipment such as frequency and voltage measurement, it is possible to sufficiently determine whether or not the measurement net on the search target board is a fault propagation net. In addition, the measurement time and the measurement cost can be reduced.

In the present invention, the time for measuring the propagation signal is set to a certain time from the start of the test program at the measurement point, a certain time at an arbitrary timing during the execution of the test program, and from the start of the test program to the occurrence of a defect. , The time from the start of the test program to the time when the number of pulses reaches a preset value, or the time of one cycle of the test program. Can be set for a certain period of time to find a fault propagation net can be reliably extracted within the set time. In such a setting, the measurement time is a fixed time, and there is a time during which measurement is not performed outside the time range, so that the measurement efficiency can be improved.

The difference between the propagation signals is determined by measuring the measurement value (pulse number, frequency or voltage) of the measurement net of the non-defective substrate corresponding to the measurement value (measurement value of pulse number, frequency or voltage) of the inspection net on the target substrate. Measurement). In this way, in order to determine whether the propagation signal of the non-defective board and the target board are completely the same, advanced signal analysis is performed, and simple measurement such as the number of pulses can be performed without collecting detailed data. If the pass / fail judgment is made based on data that can be measured by the device, it is possible to sufficiently judge whether or not the measurement net on the searched board is a fault propagation net, and to reduce the measurement time and the pass / fail judgment time. And the measurement cost can be reduced.

When there is an electronic component (IC) connected to the failure propagation net at the output terminal and another electronic component connected at the bidirectional terminal, the electronic component connected to the output terminal goes back to the electronic component side. If the component is a relay point, and there is a fault propagation net connected to the output terminal of another electronic component and a fault propagation net connected to the bidirectional terminal at the relay point, the fault propagation net connected to the output terminal Goes back as the next search route. In this way, by performing the tracing based on the input / output attributes of the terminals of the electronic component, it is not necessary to collect and analyze detailed data on the internal circuit of the electronic component, thereby shortening the search time and reducing the search cost. Reduction can be achieved. In addition, by forming a propagation path composed of a failure propagation net, a failure net exists in the source flow of the propagation path due to the propagation characteristic of the failure signal, so that the failure net can be found quickly and reliably. Can be.

Further, if the failure propagation net is connected to both the output terminal and the bidirectional terminal, and if the tracing is performed with priority given to the output terminal, the bidirectional terminal will have the input attribute and the output attribute. Because of this, it is possible to leave room for selection of both attributes in the subsequent dating,
Eventually, it is possible to trace all the fault propagation nets. Here, in tracing back the propagation route, the end point is the faulty propagation net that was traversed last.
This fault propagation net can be used as a candidate for the source fault net. If there is no fault propagation net that goes back to the input side, the fault propagation net finally arrived is set as the fault net, and the fault net can be found by searching for the propagation route. If a closed loop is formed between a plurality of fault propagation nets, and there is no other fault propagation net that goes back to the input side for any fault propagation net on the closed loop, all faults on the closed loop Let the propagation net be a bad net.

Next, a description will be given of a mounting board defect searching apparatus according to the present invention which executes the mounting board defect searching method with reference to FIG. This apparatus for searching for a defect on a mounting board includes a test program control unit 1 for operating an electronic circuit of a mounting board 7 according to a test program, a probe 6 for detecting a signal on a net, and a probe moving mechanism for controlling the movement of the probe 6. 2, a counter 4 for counting the number of pulses based on a detection signal (propagation signal) from the probe 6, a voltmeter 5 for detecting a voltage from the detection signal, and measurement results of the counter 4 and the voltmeter 5 are input. And a control section 3 for controlling the test program control section 1 and the probe moving mechanism 2 in accordance with the result of the signal processing. Note that the mounting substrate represents both the non-defective substrate and the target substrate. Therefore, the non-defective substrate and the target substrate can be measured and inspected by the defect search device. The electronic components mounted on the mounting board 7 are connected by a net. Further, the net refers to each of the signal lines connecting the terminals of the electronic component.

The test program control unit 1 includes a reference program for a non-defective board, a test program used in a test data creation step and a defect search step for a board to be searched, a measurement result of a measurement net in the reference data creation step for a non-defective board, And a measurement result of the inspection net in the inspection data creation step of the searched substrate. Note that these test programs and measurement results can also be stored in the control unit 3. The test program is used for a function test or the like. Considering that it is important for the measurement of the propagation signal to reproduce the normal operation state of the search target board, in the defect search method of the present invention, the measurement is performed in a state where the test target board is activated by this test program. Basically,

The probe moving mechanism 2 has a three-axis moving mechanism (not shown) in the X, Y, and Z directions for moving the probe 6 to a designated point on the mounting board. The voltmeter 5 measures a voltage value of a detection signal detected by the probe 6. Further, the control unit 3 is selected from the electronic component terminals connected to the inspection net, the corresponding board pads, or the corresponding board through holes based on the layout data and the net connection information of the mounting board 7 stored in advance. A probe moving mechanism 2 for automatically probing with the probe 6 at one point.
Operation control.

Therefore, according to the configuration of the defect search apparatus, the measurement of the measurement net of the good board is performed by probing only one of the IC terminal, the substrate pad, or the substrate through hole connected to the measurement net. The inspection efficiency can be improved by reducing the number of measurement points. Also, if the measurement of the test net of the target board is performed until the difference from the non-defective product is detected for the IC terminal, the board pad, or the board through hole connected to the test net, the number of measurement points is reduced. By reducing the number, inspection efficiency can be improved. In addition, even if the IC terminal or board pad connected to the test net cannot be probed due to a physical obstacle, other electronic component terminals, board pads or board through holes connected to the test target net can be selected. Therefore, practical measurement can be performed.

Next, a description will be given of a method of searching for a defect of a mounting board by the defect searching apparatus with reference to FIG. FIG. 5 is a flowchart showing a defective net search step according to the present invention, which includes first to third steps S1 to S3.
First, in the first step S1, a non-defective substrate is operated, and a propagation signal in each of the measurement nets of the non-defective substrate is measured.
At this time, probing is performed on any one measurement point in the measurement net. In the second step S2, the target substrate is operated, and a propagation signal in each of the test nets of the target substrate corresponding to the measurement nets of the non-defective substrate is measured. At this time, probing is performed on any one of the measurement points in the inspection net, and the measurement result of the inspection net is compared with the measurement result of the non-defective substrate corresponding to the inspection net. If no difference is detected, another one measurement point in the inspection net is sequentially measured, and if a difference equal to or higher than the set level is detected, the inspection net is extracted as a fault propagation net, and the inspection net in the inspection net is extracted. If no difference equal to or greater than the set level is detected at all measurement points, the test net is extracted as a normal net. In the third step S3, the fault propagation net extracted in the second step S2 is traced back to the electronic component side connected to the fault propagation net by an output terminal or a bidirectional terminal, and using the electronic component as a relay point. An arbitrary fault propagation net connected to an output terminal or a bidirectional terminal of another electronic component at the relay point is sequentially traced back as a next search path, and a faulty net of a source flow is extracted.

The first to third steps S1 to S1
Steps S3 to S3 are implemented by executing a program (control program) on a computer as the control unit 3 included in the defect search device. The control program is read from a computer-readable recording medium (for example, a magnetic disk, an optical disk, a semiconductor memory, or any other recording medium) on which the control program is recorded by the computer of the defect search device and loaded into the main storage. The present invention can be implemented by executing the method. Alternatively, the control program may be downloaded from a server or the like provided with a recording medium storing the control program to a computer of the defect search device via a communication line. By using the recording medium in this manner, management of the control program becomes easy.

Next, the measuring time and measuring method in the first step S1 and the second step S2 will be described. The measurement time in the first step S1 and the second step S2 is a certain time from the start of the test program at a measurement point, a certain time at an arbitrary timing during the execution of the test program, and a time from the start of the test program to the occurrence of a defect. , Counter 4 from the start of the test program
Is the time until the number of pulses counted by the counter reaches the threshold value or the time equal to one cycle of the test program. Generally, a pulse signal such as a control signal has an irregular generation period, and thus a measured value differs depending on a measurement timing and a measurement time. Therefore, in the measurement method of the present embodiment, a fixed time from the start of the test program or a time equal to one cycle of the test program is applied as the measurement time.

However, when a fixed time from the start of the test program is set as the measurement time, within the measurement time,
In some cases, a difference between signals generated between a good substrate and a defective substrate is not detected. In such a case, if the time until the difference in the measurement result is detected by the test program is known, the measurement time is reset to the detection time, thereby extracting the defect within the minimum necessary time. be able to. Further, as a method of measuring a propagation signal in the present embodiment, there is a method of measuring the number of pulses or a method of measuring a voltage value. For the measurement of the number of pulses, the voltage threshold is set near the lower limit of the high-level and low-level judgment ranges, and at the time of the falling edge (transition from high level to low level) or the rising edge (transition from low level to high level). Perform the measurement.

On the other hand, for the measurement of the voltage value, for example,
When the detection signal is an output from the digital IC, the measurement is performed on a DC signal in which there are two voltage values of a high level and a low level as a logical determination value in addition to the pulse signal. Also, in the case where the voltage level of the pulse signal is near the lower limit of the high level and a failure occurs suddenly, there is a possibility that the defective portion may be missed by comparing only the number of pulses. By measuring the minimum voltage, the maximum voltage, the minimum voltage, or the average voltage of the measurement pulses simultaneously in addition to the measurement of the number of pulses, it is possible to accurately detect a portion where a difference from a good substrate occurs.

In the first and second steps described above, signals are measured by operating the mounting board with a test program. However, a board having a microprocessor (CPU) mounted thereon and having a function of controlling a propagation signal by itself, for example, a motherboard of a personal computer, is fixed to a certain steady state in a power-on state or a reset state. You can think. Therefore, the defect inspection can be performed by measuring the number of pulses and the voltage within a predetermined time at an arbitrary timing in a state where only the power is turned on.

Next, a method of extracting a fault propagation net in the second step will be described. In the method of extracting a defective propagation net in the second step, for example, two measurement results of the non-defective substrate and the target substrate are compared with each other, and a difference (difference or ratio) greater than or equal to a set level is detected in both corresponding nets. Then, the net of the target board is extracted as the fault propagation net. Here, by setting the threshold value, when the difference is smaller than the threshold value, the test net having the difference is determined to be a net within the allowable range of normal operation, and is not extracted as a fault propagation net. It is. Further, the target substrate in which the defect propagation net is found has a defective portion in any of the inspection nets. And
As will be described later, since a defective signal propagates using a defective portion as a source flow, the detected fault propagation net and the inspection net located at the source flow are connected by a path (propagation path) through which the defective signal propagates. become. Therefore, by following the propagation path formed by the inspection net found as the defective propagation net in the direction toward the headwater, it is possible to reach the defective portion.

Next, the propagation of a defective signal when a defective portion exists in an electronic circuit formed on a mounting board will be described with reference to FIG.
This will be described with reference to FIG. FIG. 1 is a circuit configuration diagram showing an electronic circuit formed on a mounting substrate. A defective portion A exists in a net N11 of this electronic circuit. The occurrence of the defective portion A is caused by the defect of the electronic component P51 and the electronic component P51.
Of the output terminal O, or a disconnection failure of the net N11. In an electronic circuit having such a defective portion A, a defective signal is propagated from the defective portion A.

For example, the electronic component P52 is transmitted from the electronic component P51 connected to the other end of the net N11 because the net N11 connected to the input terminal I is a defective net having a defective portion. Normal signal cannot be received. Therefore, since the electronic component P52 cannot perform a normal operation, it is assumed that a failure signal is propagated. Next, the nets N12 and N13 connected to the electronic component P52 have
11, the normal signal transmitted from the electronic component P51 does not arrive. Therefore, nets N12 and N13
Is a net through which a defective signal is propagated (defective propagation net). Subsequently, the net N which is regarded as a fault propagation net
The electronic component P53 having the input terminal 12 connected to the input terminal 12 and the electronic component P54 having the input terminal I connected to the net N13 cannot perform a normal operation because a normal signal does not reach. Therefore, it is assumed that a defective signal is propagated.

Similarly, these electronic components P53 and P5
4, a net N14 connected to each output terminal O of
N15 and N16 are defective propagation nets, and this influence spreads to electronic components P55 and P56 located downstream, and further to nets N17, N18 and N19.
Then, the defective signal propagates to the electronic components P57, P58 and P59 and the nets N20, N21 and N22 on the further downstream side. Therefore, if it is possible to trace the propagation path formed by these defective propagation nets and reach the source of the defective signal, it is possible to specify that the net located at this source is a defective net. Here, the source flow refers to a root position of a defect or a fault located at the starting point of a defect signal, and the cause of the defect in the source flow affects the downstream end of the electronic circuit.

The third step in this embodiment will be described using the electronic circuit shown in FIG. 3 as a specific example. This electronic circuit includes electronic components P51 to P59 and nets N11 to N2.
2. Of these, Net N11
Is a defective net because it has a defective portion. Then, due to the existence of the defective portion, the nets N12 to N22 become defective propagation nets. Therefore, a specific example of the defect tracking method in the third step will be described using the electronic circuit as an example. First, the net N2, which is regarded as a fault propagation net,
From 2, the backward propagation of the fault propagation path is started. This net N
Reference numeral 22 is connected to the output terminal O of the electronic component P59.
Therefore, the electronic component P59 goes back as a relay point.

Next, the electronic component P59 is set as a relay point, and the fault propagation net N16 connected to the output terminal of another electronic component P56 at the relay point is traced back (search path).
It goes back as. Subsequently, the electronic component P56 is set as a relay point, and a failure propagation net connected to the output terminal of another electronic component at the electronic component P56 is used as a trace path. Net N15 connected to output terminal O of P53 and output terminal O of electronic component P54
Is connected to the net N16 connected to. As described above, when there are a plurality of backward route candidates, any one may be selected, but here, the net N15 is set as the next backward route.

Further, the selected net N15 is connected to the output terminal O of the electronic component P53, the electronic component P53 is traced back as the next relay point, and connected to the output terminal O of the electronic component P52 at the relay point. The net N12 is set as the next backward route. Further, the selected net N12 is connected to the output terminal O of the electronic component P52, the electronic component P52 is traced back as the next relay point, and the net N11 connected to the output terminal O of the electronic component P51 at the relay point is connected. This is the next backward route. Navigating back in this manner, N22
Following the route of → N19 → N15 → N12 → N11, the search is once ended in the fault propagation net N11 to which the next relay point is not connected. Then, the fault propagation net N11 located at the end point is set as a fault net candidate.

The net N16, which is the other backward route, is connected to the output terminal O of the electronic component P54. The electronic component P54 goes back as the next relay point, and is connected to the output terminal O of the electronic component P52 at the relay point. The set net N13 is set as the next backward route. Here, the net N11 connected to the output terminal O of the electronic component P51 goes back as the next traversal route, and this net N11 has already been traversed. Therefore, backtracking is temporarily terminated at this point.

Next, the net N that has not been searched yet
From 21, the fault propagation path is traced back. This net N21 is connected to the output terminal O of the electronic component P58. Therefore,
The electronic component P58 is traced back as a relay point. Next, the electronic and electronic component P58 is set as a relay point, and the output terminal of the electronic and electronic component P55 and the net N18 connected to the bidirectional terminal I / O of the electronic component P57 at the relay point are set as the next backward route. Next, the electronic component P55 connected to the output terminal O of the net N18 and the electronic component P57 connected to the bidirectional terminal I / O are candidates for the next relay point. Thus, when there is an electronic component connected at the output terminal and another electronic component connected at the bidirectional terminal with respect to the defect propagation net,
Going back to the electronic component P55 connected to the output terminal, the electronic component P55 is set as a relay point, and the net N14 connected to the output terminal O of the electronic component P53 is set as the next search path.

Here, the selected net N14 is connected to the output terminal O of the electronic component P53, the electronic component P53 goes back as the next relay point, and is connected to the output terminal O of the electronic component P52 at the relay point. Will be traced back to the net N12 as the next route.
Backtracking has already taken place. Therefore, backtracking is temporarily terminated at this point. Next, net N2 that has not been searched yet
From 0, the fault propagation path is traced back. This net N20 is connected to the output terminal O of the electronic component P57. Therefore, the electronic component P57 is traced back as a relay point. Next, with the electronic / electronic component P57 as a relay point, a net N18 connected to the electronic / electronic component P55 at the output terminal O and a net N17 connected to the electronic component P55 with the bidirectional terminal I / O at the relay point are next. Is a candidate for a backward route.

As described above, when there is a fault propagation net connected to the output terminal of another electronic component and a fault propagation net connected to the bidirectional terminal at the relay point, the fault propagation net N18 connected to the output terminal is changed. Although it goes back as the next search route, this net N18 has already gone back. Therefore, backtracking is temporarily terminated at this point. Next, the fault propagation path is traced back from the net N17 for which the search has not been performed yet. The net N17 is connected to the electronic / electronic component P57 via a bidirectional terminal I / O, and to the electronic / electronic component P55 via a bidirectional terminal I / O. Net N connected to electronic component P55 at output terminal O with electronic component P57 as a relay point
18 and the electronic component P5 with the electronic component P55 as a relay point.
3 and the net N14 connected at the output terminal O are the next forward candidates. In this case, either may be selected, but here, the net N14 is set as the next retroactive route. This net N14 has already been traced back. Therefore, backtracking is temporarily terminated at this point. Also, in the case where the net N18 is used as the next tracing route, the tracing is already ended at this point because the tracing of the net N18 has already been performed. Therefore,
Through the above-described search, tracing is performed on all the failure propagation nets, and the net N11 is specified as a failure net.

Next, a case where the fault propagation net forms a closed loop in the third step of the present embodiment will be described using the electronic circuit shown in FIG. 4 as a specific example. FIG. 4 is an example of a configuration of a failure propagation net having a failure location B and an electronic component when the failure propagation net in the present embodiment forms a closed loop. Since the fault propagation nets N23 to N26 form a closed loop, it is not possible to specify the faulty net of the source flow. In this case, all nets forming a closed loop, that is, the failure propagation nets N23 to N26 are regarded as failure nets.

Next, the extraction of the fault propagation net in the second step and the search for the fault net in the third step will be described using the electronic circuit shown in FIG. 5 as a specific example. This electronic circuit includes electronic components P64 to P66, a net N27, and measurement points T1 to T4. Among them, the electronic component P64 has a defective portion C. Then, it is assumed that a defective signal propagates to the net N27 due to the existence of the defective portion C. In the net N27 of the target substrate, when the measurement is first performed by probing to the measurement point T1,
The difference from the measurement result in the net N27 of the non-defective substrate is detected. Therefore, the net N27 is extracted as the fault propagation net, and the measurement and determination of the net N27 are terminated.

Next, the same measurement and determination are sequentially repeated for another net of the target board. Net N of target board
27, since the difference from the measurement result of the non-defective board is detected regardless of the measurement point of any of the measurement points T2 to T4, the net N27 is extracted as the fault propagation net, and the net N27 is extracted to another net of the target board. The measurement and the judgment are sequentially repeated. In the failure net search in the third step, since no failure propagation net exists upstream of the failure propagation net N27, the net N27 is extracted as a failure net. And the net N27 and the net N27
Is finally extracted as a defective candidate.

Next, another example of extracting a fault propagation net in the second step will be described using the electronic circuit shown in FIG. 6 as a specific example. This electronic circuit includes electronic components P67 to P69, a net N28, and measurement points T5 to T8. Of these, the net N28 has a defective portion D due to disconnection. On a good board, a pulse signal propagates from the output terminal of the electronic component P67.
It is assumed that a normal pulse signal propagates at 5, T6, and T8, but no signal propagates at the measurement point T7 due to disconnection failure.

In the net N28 of the target board, first,
When the measurement is performed by probing to the measurement point T5, a difference from the measurement result in the net N28 of the non-defective substrate is not detected. Therefore, the measurement point T6 is measured next. At the measurement point T6, since no difference is detected from the measurement result in the net N28 of the non-defective substrate, the measurement point T7 is measured next. At the measurement point T7, since the difference from the measurement result in the net N28 of the good board is detected,
The net N28 is extracted as a fault propagation net, and measurement and determination are sequentially repeated for another net of the target board.

In the failure net search in the third step, since no failure propagation net exists upstream of the failure propagation net N28, the net N28 is extracted as a failure net. Then, at measurement points T5 and T6, no difference from a non-defective product is detected, and at measurement point T7, a difference from a non-defective product is detected. Therefore, net N28 is finally extracted as a defective candidate. In this manner, by repeating the measurement and the comparison judgment for a plurality of measurement points in each net of the target board until a difference from the measurement result of the net of the corresponding non-defective board is detected, accurate and quick The fault propagation net can be extracted. That is, according to the present embodiment, for each net on the mounting board, the number of pulses, frequency, or voltage that can be easily measured and compared is measured. By repeating the measurement and comparison judgment while changing the measurement point, the fault propagation net can be extracted.Furthermore, by going back based on the input / output attribute of the terminal of the electronic component connected to the fault propagation net, the fault location of the source flow can be detected. It can be extracted and can be implemented automatically and at high speed with a simple system configuration.

The defect search method according to the present embodiment is performed by the control unit 3 provided in the mounting board defect search device. In the above-described embodiment, the case of searching for a defect of an IC, an LSI, or the like mounted on a substrate has been described. In addition, a digital signal processor (DSP) or an application-specific IC formed on a silicon wafer may be used. The present invention can be applied to an IC such as an (ASIC) and the LSI itself. In this case, not the IC pins but the logic terminals of the logic circuit are used for searching for a defective portion.

[0067]

As described in detail above, according to the present invention, the conventional inspection method uses a measuring instrument such as a board tester or a signature analyzer to compare the timing or operation waveform with non-defective products. By measuring and comparing the number of pulses, the frequency or the voltage of the net on the non-defective substrate and the substrate to be searched, the amount of information accompanying the measurement can be greatly reduced. Further, the measurement time and the processing time can be greatly reduced, and the system cost can be reduced by configuring the system with simple measuring devices such as a counter and a voltmeter as a means for measuring the number of pulses and the voltage.

In addition, one arbitrary measurement point in the measurement net of the non-defective substrate is measured, and the inspection is performed until the difference between the measurement result of the non-defective substrate and the measurement result of the target substrate corresponding to the measurement net of the non-defective substrate is detected. The measurement points in the net are measured and compared sequentially, and when a difference equal to or greater than the set level is detected, the inspection net is extracted as a failure propagation net, so that the failure of the search target board can be detected with high accuracy. In addition, the measurement time can be reduced as compared with the case where all the measurement points are measured. Furthermore, based on the input / output attributes of the terminals of the electronic components connected to the fault propagation net,
By tracing back to the extracted fault propagation net and extracting the faulty part of the headwater, the effect of quickly specifying the faulty part is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an apparatus for searching for a defect of a mounting board according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a procedure for searching for a defective point in the embodiment of the present invention.

FIG. 3 is a circuit configuration diagram for explaining a failure signal propagation, a headwater flow, and a failure search procedure according to the present invention.

FIG. 4 is another circuit configuration diagram for explaining a failure signal propagation, a source flow, and a failure search procedure according to the present invention.

FIG. 5 is another circuit configuration diagram for explaining the propagation, source flow, and failure search procedure of the failure signal according to the present invention.

FIG. 6 is another circuit configuration diagram for explaining a failure signal propagation, a headwater flow, and a failure search procedure according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Test program control part 2 Probe moving mechanism 3 Control part 4 Counter 5 Voltmeter 6 Probe 7 Mounting board P51, P52, P53, P54, P55, P56, P
57, P58, P59 P60, P61, P62, P6
3, P64, P65, P66 Electronic components N11, N12, N13, N14, N15, N16, N
17, N18, N19 N20, N21, N22, N2
3, N24, N25, N26, N27 net (inspection net)

Claims (23)

[Claims] 1. A defect search method for a mounting board for searching for a defective portion by comparing a non-defective board on which an electronic component is mounted and a target board, wherein the non-defective board is operated, and each of the measurement nets of the non-defective board is operated. When measuring the propagation signal in, the first step of measuring any one measurement point in the measurement net, operating the target board, the test net of the target board corresponding to the measurement net of the good board Propagation signals in each are measured at any one measurement point in the inspection net, and the measurement result of the inspection net is compared with the measurement result of the measurement net of the non-defective substrate corresponding to the inspection net. If no difference above the level is detected, another one of the measurement points in the inspection net is sequentially measured, while if a difference above the set level is detected, Extracting a test net as a fault propagation net, and if no difference equal to or greater than a set level is detected at all measurement points in the test net, extracting the test net as a normal net; With respect to the fault propagation net extracted in the above, it goes back to the electronic component side connected to the fault propagation net by an output terminal or a bidirectional terminal, and the electronic component is used as a relay point, and the output of another electronic component is performed at the relay point. A third step of sequentially traversing an arbitrary fault propagation net connected to the terminal or the bidirectional terminal as a next search path and extracting a faulty net of a source flow. 2. The mounting according to claim 1, wherein in the first and second steps, the propagation signal is generated by operating an electronic circuit of the non-defective substrate and the target substrate by a test program. Substrate defect search method. 3. In the first and second steps, when the non-defective substrate and the target substrate can control the propagation signal by the substrate alone, the transmitted signal is transmitted to the electronic circuit on the non-defective substrate and the target substrate. 2. The method according to claim 1, wherein the defect is generated by supplying power to the mounting board. 4. In the first and second steps, each signal measurement of the measurement net on the non-defective substrate and the test net on the target substrate is performed by measuring at least one of the number of pulses, frequency and voltage. 4. The method according to claim 1, wherein the method is performed. 5. In the first and second steps, each voltage measurement of the measurement net on the non-defective substrate and the test net on the target substrate is performed by at least one of a highest voltage, a lowest voltage, and an average voltage of the propagation signal. 5. The method according to claim 4, wherein the method is performed by measuring the number of defects. 6. The method according to claim 1, wherein in the first and second steps, the time for measuring the propagation signal is a certain time from a start of a test program at a measurement point, a certain time at an arbitrary timing during execution of the test program, The time from the start of the program until the failure occurs,
3. The failure of the mounting board according to claim 2, wherein the time is one of a time from the start of the test program until the number of pulses reaches a preset value and a time of one cycle of the test program. Search method. 7. The determination of a difference between propagation signals in the second step is performed based on a ratio or a difference between two measurement values of the inspection net and the measurement net with respect to the number of pulses, frequency, or voltage. 2. The method according to claim 1, wherein 8. The search for a fault propagation net in the third step is performed when there is an IC connected to the fault propagation net at an output terminal and another IC connected at a bidirectional terminal. Back to the side, the IC is used as a relay point, and when there is a fault propagation net connected to the output terminal of another IC and a fault propagation net connected to the bidirectional terminal at the relay point, the IC is connected to the output terminal. 2. The method according to claim 1, wherein the defective propagation net is traced back as a next search path. 9. The mounting board according to claim 1, wherein in the third step, when the search has been traced back from another route to the already found defect propagation net, the search is terminated there. Failure inspection method. 10. The method according to claim 1, wherein, in the third step, if there is no fault propagation net that goes back to the input side, the fault propagation net finally reached is a fault net.
3. The method for searching for a defect of a mounting board according to the item 1. 11. In the third step, a closed loop is formed between a plurality of fault propagation nets, and for any fault propagation net on the closed loop, there is no other fault propagation net going back to the input side. 2. The method according to claim 1, wherein all of the fault propagation nets on the closed loop are fault nets. 12. A test program control unit for operating an electronic circuit on the non-defective board and the target board according to a test program for generating each propagation signal in the measurement net of the non-defective board and the inspection net of the target board; A probe that detects each propagation signal of the measurement net and the inspection net of the target board; and, based on the output of the probe, measures each propagation signal of the measurement net of the good board at any one measurement point to measure the good board. The propagation signal in each of the test nets of the target board corresponding to the net is measured at any one measurement point in the test net, and the measurement result of the test net and the measurement of the non-defective board corresponding to the test net are measured. Compare with the measurement result of the net, if no difference of more than the set level is detected, another one in the inspection net The measurement points are sequentially measured.On the other hand, when a difference equal to or higher than the set level is detected, the inspection net is extracted as a failure propagation net, and the difference equal to or higher than the set level is detected at all the measurement points in the inspection net. If it is not detected, the inspection net is extracted as a normal net, and the fault propagation net is traced back to the component connected to the output terminal or the bidirectional terminal, and another fault propagation net is set as the relay point to the next fault propagation net. A failure detecting device for a mounting board, comprising: a control section that sequentially goes back as a search path and extracts a failure net of a headwater flow. 13. The control unit controls the operation of the test program control unit and the probe based on the propagation signal, the extracted signal of the defective propagation net, and the retroactive information of the search path for the defective propagation net. Claim 1
3. The failure search device for a mounting board according to 2. 14. The non-defective substrate and the target substrate include a control unit including a microprocessor, and have a function of controlling the propagation signal by the substrate alone. 14. The defect search device according to claim 12, wherein the defect search device is generated by supplying power to a circuit. 15. The signal measurement of the measurement net on the non-defective substrate and the test net of the test net on the target substrate is performed by measuring at least one of the number of pulses, the frequency, and the voltage. A defect search device for a mounting board according to claim 13. 16. The measuring means for measuring the voltage measures at least one of a highest voltage, a lowest voltage and an average voltage of the propagation signal with respect to the measurement net of the good board and the search net of the target board. The apparatus for searching for a defect of a mounting board according to claim 15, wherein: 17. A time period for measuring the propagation signal is defined as a certain time from the start of the test program at a measurement point, a certain time at an arbitrary timing during the execution of the test program, and a time from the start of the test program until a failure occurs. 14. The method according to claim 12, wherein the time is any one of a time, a time from the start of the test program until the number of pulses reaches a preset value, or a time of one cycle of the test program. A defect search device for a mounting board as described in the above. 18. The method according to claim 12, wherein the determination of the difference between the propagation signals is performed based on a ratio or a difference between two measurement values of the pulse number, the frequency, or the voltage measurement value. 4. A defect search device for a mounting board according to claim 1. 19. The method for searching for a defective net includes, when there is an IC connected to the defective propagation net at an output terminal and another IC connected at a bidirectional terminal, the IC connected to the output terminal.
Going back to the C side, the IC is used as a relay point, and at the relay point, there is a fault propagation net connected to the output terminal of another IC and a fault propagation net connected to the bidirectional terminal,
14. The defect search device for a mounting board according to claim 12, wherein the defect search net connected to the output terminal is traced back as a next search path. 20. The method according to claim 12, wherein, in the search for the defective net, if the search has been traced back from another path to the already-detected defective propagation net, the search is terminated there. A defect inspection device for a mounting board as described in the above. 21. The fault net according to claim 12, wherein, in the search for the fault net, when there is no fault propagation net that goes back to the input side, the fault propagation net finally reached is set as the fault net. Search device for mounting boards. 22. In the search for a defective net, a closed loop is formed between a plurality of the defective propagation nets, and another defective propagation net that goes back to the input side with respect to an arbitrary defective propagation net on the closed loop. 14. The apparatus according to claim 12, wherein all of the fault propagation nets on the closed loop are determined as fault nets when there is no fault net. 23. A probe for operating a non-defective substrate by a test program to detect each propagation signal of a measurement net of the non-defective substrate and an inspection net of a target substrate, and the non-defective substrate and the target for generating the propagation signal. When controlling a test program control unit that stores a test program for operating an electronic circuit on the board, and measuring a propagation signal in each of the measurement nets of a good board,
A step of measuring any one measurement point in the measurement net; and operating the target board, controlling the probe and the test program control unit, and inspecting the target board corresponding to the measurement net of the good board. Propagation signals in each of the nets are measured at any one measurement point in the inspection net, and the measurement result of the inspection net is compared with the measurement result of the measurement net of the non-defective substrate corresponding to the inspection net. If no difference above the set level is detected, another one of the measurement points in the inspection net is sequentially measured, while if a difference above the set level is detected,
Extracting the test net as a fault propagation net, and if no difference equal to or greater than a set level is detected at all measurement points in the test net, extracting the test net as a normal net; and With respect to the net, it goes back to the electronic component side connected to the failure propagation net with the output terminal or the bidirectional terminal, and the electronic component is used as a relay point, and the output terminal or the bidirectional terminal of another electronic component is used at the relay point. A computer-readable recording medium for recording a program for sequentially executing an arbitrary fault propagation net connected thereto as a next search path, and executing a procedure of extracting a source fault net.