JPH032267B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a signal line insulation/continuity determining device particularly suitable for determining insulation/continuity of signal lines on a multilayer board.

[Technical Background of the Invention] Conventionally, a signal line insulation continuity determination device using the capacitance value of a signal line pattern has been used as a device for determining insulation continuity of a board having a large number of terminals such as a multilayer board. ing. This signal line insulation continuity determination device detects the same signal line pattern when measuring the capacitance between each signal line and the electrode with the electrodes facing each other with an insulator in between. This takes advantage of the fact that a certain amount of capacitance is generated.

The structure and operation of a conventional circuit board signal line insulation continuity determination device using this principle will be described with reference to FIG.

FIG. 1 is a block diagram schematically showing the configuration of a conventional signal line insulation continuity determination device.

This signal line insulation continuity determination device includes a measuring device 1 that measures the capacitance of each signal line on a board, and a limit value memory 2 that stores the upper and lower limits of allowable capacitance for each signal line. and a comparator 3 that compares and determines the upper and lower limit values of the limit value memory 2 and the actual capacitance value of the signal line measured by the measuring device 1;
The upper and lower limits of allowable capacitance for each signal line are calculated from the display 4 that displays the judgment results, the reference capacitance registered by the worker, and the judgment parameters, and stored in the limit value memory 2. Its main part is composed of a control device 5 that holds the device and controls each part.

Judgment of insulation continuity of a signal line using such a conventional signal line insulation/continuity judgment device is performed according to the procedure shown in the flowchart of FIG.

That is, before starting work, the worker first sets the reference capacitance for each signal line and the judgment parameters for giving an allowable range that takes manufacturing and measurement errors into account, and registers these in the control device 5. do.

The determination of the reference capacitance as the pre-processing described above has conventionally been performed using the following two methods.

One method is to use a board manufactured from the same original board as the test item and determined to have a regular conductor structure as a result of a continuity test as a standard sample, and measure the capacitance value of each signal line on this board. This method is to register the value as a reference value. Another method is to pick up the area of each signal line from the design drawing of the board, calculate the theoretical capacitance from this, and register it.

The control device 5 calculates an upper limit capacitance and a lower limit capacitance for each signal line of the board from the registered reference capacitance and determination parameters, and causes the limit value memory 2 to store and hold the upper limit capacitance and lower limit capacitance. Here, thick lines and thin lines in the figure respectively indicate the control signal line and the information signal line of this signal line insulation continuity determination device.

When measurement of the board to be inspected is started by the measuring device 1, the capacitance values for each signal line output from the measuring device 1 are sequentially taken into the comparator 3, while the corresponding capacitance values are taken in from the limit value memory 2. The upper and lower limit values of the signal line are taken into the comparator 2, and it is determined whether the actually measured capacitance value is within the allowable range indicated by the upper and lower limit values, and the result is displayed. It is output to device 4.

[Problems in the Background Art] In the conventional board signal line insulation continuity determination device described above, the measured capacitance of each signal line on the board falls within a certain range determined from the reference capacitance registered by the worker and the determination parameter. The only thing that guarantees the reliability of the judgment result is whether the determined range is within the range of possible values for a good signal line. It was left to the discretion of the workers.

In other words, the reliability of the judgment result using arbitrarily determined judgment parameters depends on whether or not a circuit element mounted on a board recognized as passing by this judgment constitutes a circuit with regular functions. Since the judgment is made for the first time, the operator corrects the judgment parameters based on the results.However, even if the values are within the allowable range, if they are close to the limit values, a visual inspection and continuity test are performed separately. It was. In other words, in the past, a secondary limit value was set empirically within the permissible range. This is because there is no sufficient basis for determining conventional determination parameters, and moreover, the set reference capacitance itself is set as a single reference sample with a substrate having certain unique characteristics.

Therefore, the operator had to repeat trial and error to modify and re-register the determination parameters and change the reference values until the reliability of the determination results reached a value that was satisfactory.

As described above, in order to satisfy the functions desired by the worker, in the conventional judgment device, pre-processing such as registration of the reference capacity and judgment parameters by the worker,
It is necessary to go through complex and cumbersome processes such as analysis of judgment results, correction of judgment parameters, and post-processing such as re-registration, which has been a major obstacle in improving the efficiency and reliability of the system. In particular, the task of determining the reference capacitance has the disadvantage of requiring an enormous amount of time for multilayer boards in which 1,000 to 2,000 signal lines are printed on each board.

In addition, the conventional method of reviewing judgment parameters relies entirely on the empirical judgment of the operator, which has the disadvantage of lacking reliability.

As described above, conventional determination devices rely on workers for most of the important parts of the determination standard setting process, such as setting the reference capacitance and determination parameters, and therefore, conventional signal line insulation continuity determination devices Although it only functions as an automatic verification device, and the process by which operators set judgment criteria is complicated and requires a considerable amount of time and effort, its determination method is based on property prediction from a single sample. As a result, it became unreliable.

Therefore, with such a conventional signal line insulation/continuity determination device, high-speed, large-scale processing of a large number of products cannot be expected, and improvements have been desired.

[Objective of the Invention] The object of the present invention is to significantly reduce operator intervention in the signal line insulation continuity determination device for a board as described above, and to analyze the characteristics of the signal line for each measurement to achieve high reliability. An object of the present invention is to provide a signal line insulation continuity determination device for a board that can automatically set determination criteria at high speed.

Another object of the present invention is to eliminate uncertain factors such as the conventional single sample and arbitrary parameters in setting judgment criteria, and to analyze past measurement data of the substrate to eliminate manufacturing errors and measurement errors. It is an object of the present invention to provide a signal line insulation continuity determination device for a board, which automatically determines determination criteria that reflect various characteristic factors such as the following.

[Summary of the Invention] The signal line insulation continuity determination device for a board of the present invention statistically processes the capacitance value of each signal line for each board for each measurement, and sequentially updates the average capacitance and deviation. However, the present invention is characterized in that the determination device itself employs a distribution function for determining the reference capacitance and the allowable range.

When the capacitance of a signal line is measured over many test items, the actual measured values will vary within a certain range depending on the characteristics of each test item. If this variation due to the characteristics of the signal line is caused by similar factors such as manufacturing errors and measurement errors, the degree of this variation can ultimately be approximated by a normal distribution. Therefore, as a conversion coefficient for selecting the desired reference capacitance and degree of dispersion from the actually measured capacitance value of each signal line, the actual value of the i-th test item is used as the conversion coefficient.
When Xi and the number of measurements are n, the following conversion coefficients can be used.

=1/n _o 〓 ⁱ⁼ⁿ Xi ......(1) σ ² =1/n-1 _o 〓 ⁱ⁼ⁿ (Xi-) ² ...(2) The X obtained here is the reference capacitance, σ By using the standard deviation as the standard deviation, it becomes possible to conduct an analysis that covers all characteristic factors.

Here, according to the definition of normal distribution, 99.73% of the inspected items are included in the range S expressed by the following formula: S=+3σ (3).

Therefore, the characteristics of the signal line are uniformly affected by manufacturing errors and
If it is caused by a defect other than a measurement error such as a short circuit or disconnection with another signal line,
It is possible to determine pass/fail of the signal line within the range indicated by S.

Also, whether or not the actual measurement value distribution of the signal line can be approximated by a normal distribution is determined by the following formula based on the definition of the workability index. In other words, if the maximum value among the measured values is C and the minimum value is C, then in the following formula B = σ / (C _MAX + C _MIN ) / 2 ... (4), if B≦1, it is sufficiently reliable. There is, B
If >1, it becomes clear that the influence of manufacturing errors on this signal line is too large, and that approximating the actual measurement value distribution by a normal distribution is unreliable. Since each signal line is printed from the same original board, this error indicates that some problem has occurred in the manufacturing process.

The insulation continuity determination apparatus of the present invention performs the above-described determination based on determination criteria automatically created from the capacitance values of each signal line accumulated each time a board is measured.

[Embodiment of the Invention] An embodiment of the signal line insulation continuity determination device for a substrate according to the present invention will be described with reference to FIGS. 3 to 5. FIG.

In these figures, parts common to those in FIG. 1 are designated by the same reference numerals as in FIG. 1.

As shown in FIGS. 3 and 4, the circuit board signal line insulation continuity determination device of this embodiment includes a measuring device 1, a limit value generator 2', a comparator 3, a display 4, and a control device 5. The main part consists of a limit value generator 2', a cumulative distributor 6, a counter 7, a cumulative memory 8, a distribution function generator 9, and a reference value calculator 1.
0, an extreme value memory 11, and a judgment function monitor 12.

In the embodiment with the above configuration, the control device 5 outputs various control signals such as operation timing signals to various parts of the determination section when measuring the signal line of the board. Measuring device 1
receives a timing signal from the control device 5, sequentially measures the capacitance of each signal line on the board, and transmits the measured values to the cumulative distributor 6 and the comparator 3.

The cumulative distributor 6 receives the identification signal on the signal line from the control device 5, opens the corresponding gate of the cumulative storage 8, and transmits the measured value to the cumulative storage 8. The cumulative storage section 8 cumulatively adds and holds the received measurement values, and transmits this to the distribution function generator 9.

On the other hand, when the cumulative distributor 6 opens the gate of the cumulative memory 8, the counter 7 corresponding to this gate is set to 1.
are added, this counter 7 holds the number of measurements for each signal line, and transmits this to the distribution function generator 9. The distribution function generator 9 receives the total number of measurements and the cumulative capacitance value of each signal line, calculates a normal distribution function from these data, and transmits the above range of S to the reference value calculator 10. The reference value calculator 10 determines the range of S that is the range where the existence probability is most guaranteed based on the normal distribution, that is, the range whose upper and lower limits are the sample mean plus three times the standard deviation, respectively. and transmits this to the comparator (3).

Here, the comparator 3 determines whether each signal line is good or bad depending on whether the measured value transmitted from the measuring device 2 is within the tolerance range consisting of the upper limit value and the lower limit value, and displays this result on the display 4. Output to.

Furthermore, when the maximum and minimum values among the measured values of each signal line are taken into the cumulative storage 8, they are also stored in the extreme value storage 11 at the same time. Judgment function monitor 1
2 takes out the measured maximum and minimum values of each signal line from the extreme value memory 11, determines whether or not the normal distribution is applied based on their spread, and outputs a message to this effect on the display 4 if the reliability is extremely low. .

The operation of the apparatus of this embodiment has been described above in chronological order, but the operation timing of the apparatus of this embodiment, the opening and closing of the information transmission gate, etc. are all controlled by control signals from the control apparatus 5.

In this device, the preprocessing work required by the operator is to measure the capacitance of the signal lines of about 5 to 10 boards prior to inspection, and store the values in the cumulative memory 8, as shown in the flowchart in Figure 5. Just to create a track record,
After this, based on the measurement data measured by measuring device 1,
The reference capacitance and tolerance range of the signal line are determined in sequence, and the measurement data is compared with this tolerance range and the result is displayed on the display 4. Judgment criteria are also constantly monitored, and if reliability is low, This information is also displayed on display 4.
will be displayed.

As described above, according to this embodiment, the reference value is determined simply by creating the measurement results in the cumulative memory 8, and for the board that has been measured and registered once, there is no need for repeated measurements, and new By simply registering measurement data for each board, each time one board is measured, the capacitance value stored in the cumulative memory 8, that is, the measurement results, is sequentially updated, and the new reference capacitance and tolerance are updated. The range is determined, and the quality of the board is determined by comparing it with this standard.
In addition, the judgment criteria are constantly monitored.

[Effects of the Invention] As explained above, according to the signal line insulation continuity determination device for a board of the present invention, the reference capacitance and tolerance range reflecting the characteristic error of each signal line are automatically determined each time a board is inspected. , and the more the number of inspections increases, the more accurate the tolerance range can be learned and updated for pass/fail determination.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a conventional circuit board signal line insulation/continuity determining device, FIG. 2 is a flowchart showing a procedure for determining signal line insulation/continuity according to the conventional method, and FIG. 3 is an embodiment according to the present invention. 4 is a block diagram schematically showing the configuration of the signal line insulation continuity determination device for the board of
This figure is a block diagram specifically showing the configuration of the limit value generating device shown in FIG. 3, and FIG. 5 is a flowchart showing the procedure for determining insulation and continuity of the signal line by the device of this embodiment. 1...Measuring instrument, 2'...Limit value memory, 3...
Comparator, 4...Display device, 5...Control device, 6...
Cumulative distributor, 7... Counter, 8... Cumulative memory, 9... Distribution function generator, 10... Reference value calculator, 11... Extreme value memory, 12... Judgment function monitor.

Claims (1)

[Claims] 1. A measuring device that measures the capacitance values between a plurality of signal lines provided on a substrate and electrodes arranged opposite to these signal lines with an insulator interposed therebetween; a cumulative storage unit that cumulatively adds and stores capacitance values obtained as a result of measurements for each of the signal lines; a counter that counts and holds the number of times the board is measured by the measuring device; a distribution function generator that generates a probability distribution function from the cumulative capacitance value stored in the cumulative storage unit and the number of measurements held in the counter; a reference value calculator that determines a reference capacitance and its allowable range used to determine the validity of the capacitance value of a signal line; and a capacitance value newly measured by the measuring device and the reference value. A comparator that compares the reference capacitance calculated by the calculator and determines whether the difference between the two is within the allowable range, and a capacitance value of the signal line corresponding to each board. An extreme value memory that stores and holds the maximum and minimum values, respectively, and the reference value calculator based on the maximum and minimum values of the capacitance values for each of the signal lines stored in the extreme value memory. 1. A signal line insulation continuity determination device for a circuit board, comprising: a reference capacitance output from the circuit board; and a determination function monitor for determining reliability within an acceptable range.