JP2002190436A - Electrostatic monitoring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge whether electrostatic countermeasures have been completed for each product. SOLUTION: A measurement value regarding electrostatic environments is collected in time series (step 1000), and the collected measurement value is stored, in connection with the product (step 1010). The steps 1000 and 1010 are carried out for each working region. The product having an abnormal, related measurement value, is distinguished from others as being a product that may have been affected by electrostatics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a static electricity monitoring system for monitoring a static electricity environment in a factory which handles static sensitive products, and more particularly, a complete countermeasure against static electricity in a production / inspection line for electronic components sensitive to static electricity. And a static electricity monitoring system that guarantees each product.

[0002]

2. Description of the Related Art In a production and inspection line for electronic components sensitive to static electricity, a wrist strap, a conductive work board,
An ionizer or the like is used. The wrist strap is worn on the worker's arm and is grounded via a resistance of about 1 MΩ. If the ground resistance of the worker is too high, the worker is likely to be charged with static electricity, and if the ground resistance is too low, a large discharge current will flow when it comes into contact with charged components, so the wrist strap prevents them beforehand. . Further, the ionizer supplies ionized air to a product, a jig, a worker's clothes, and the like to lower a charged potential.

Whether these countermeasures against static electricity are functioning effectively can be known by measuring the grounding resistance of an operator, measuring the potential with a charging electrometer, and the like. However, conventionally, these measurements have been
According to the MIL standard, when an abnormal measurement value is output after completion of the work, it is sometimes necessary to discard all products for one day according to the MIL standard.

[0004] Devices are also commercially available that periodically measure the grounding resistance of the worker during work and notify the operator of any abnormalities by means of a lamp display or a warning sound (a 724 workstation monitor manufactured by 3M Corporation). It does not automatically identify the affected products when they do.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to periodically measure the static electricity environment of a manufacturing / inspection line, and to distinguish products which may be affected by an abnormality in the event of an abnormality. An object of the present invention is to provide a static electricity monitoring system that can be specified.

[0006]

According to the present invention, there is provided a means for collecting, as a time series, measured values relating to an electrostatic environment of each work area of a production line including a plurality of work areas, and A static electricity monitoring system is provided that includes means for storing in association with a product present in the work block at the time, and means for classifying each product according to the associated measurement value.

[0007] Preferably, the measured value includes a ground resistance of a worker in a work area. It is also desirable that the measurements include the charging potential of an operator in the work area. It is also desirable that the system further comprises means for processing the collected measurements for each worker to determine the suitability of each worker for the task.

[0008]

FIG. 1 shows an electrostatic monitoring system according to an embodiment of the present invention. Although FIG. 1 shows only one work area 10 on the production line 12, many similar work areas are arranged on the production line 12. A to E represent electronic components flowing on the production line 12. By reading a bar code (not shown) attached to each electronic component with a bar code reader 14, a control computer 16
Recognizes which product is currently in area C within each work area. Further, the control computer 16 recognizes which worker is performing the work in each work area by means such as an IC card and a magnetic card (not shown).

The conductive work board 18 suppresses the triboelectric potential on the work surface to a low level, and is, for example, 8345J-2 manufactured by 3M. The ionizer 20 reduces the charged potential by supplying ionized air to a product, a jig, a worker's clothes, and the like.
3. The charge potentiometer 22 measures the charge potential of the area C, and is, for example, a 718 electrostatic tester manufactured by 3M. The wrist strap 24 is attached to the arm of the worker to maintain the ground resistance of the worker in an appropriate range, and is, for example, 2381 manufactured by 3M. Monitor 26
Is a device for continuously monitoring whether the ground resistance of the conductive work board 18 and the worker is within an appropriate range, and is, for example, a 724 workstation monitor manufactured by 3M. The conductive work board 18 and wrist strap 24 are grounded via a workstation monitor 26.

Although not shown in FIG. 1, a charging potentiometer 28 as shown in FIG.
Is provided. The electrostatic potentiometer 28 is connected to the wrist strap 24
It measures the potential of the worker by measuring the potential of the cable between the terminal and the workstation monitor 26, and is, for example, a 711 charge analyzer manufactured by 3M.

The ground resistance of the worker and the conductive work board 18 grounded by the wrist strap 24 is measured by a wrist strap monitor 26, and the charging potential of the worker is periodically measured by a charging potentiometer 28 and sent to the computer 16. . The current for measuring the grounding resistance of the conductive work board 18 is always flowing and the resistance value is also constantly measured, but the current for measuring the grounding resistance of the worker is 5 ms to 2 s.
And the measurement is also performed in a pulsed manner. The measurement of the charged potential is always performed. Since the voltage generated by the current pulse for measuring the ground resistance is about 2 V, it does not substantially affect the measurement of the charged potential. This effect can be completely eliminated if the measurement of the charging potential is performed in synchronization with the current pulse.

When the conductive work board 18 is grounded through the workstation monitor 26 and the worker is grounded through the wrist strap 24, the charged potential of the worker does not exceed 5V. However, if the grounding of the conductive work board 18 or the wrist strap 24 is incomplete for some reason, the charge amount may exceed 50 V after one second. For reference, FIG. 3 shows the measurement results of the charged potential when an operator who does not wear the wrist strap performs various operations.
Similarly, if the operation of the ionizer 20 is incomplete, the ion balance may be disrupted and static electricity of 20 V or more may be generated. The occurrence of such an event is detected by the workstation monitor 26 or the electrostatic voltmeter 22 and immediately linked to the product identifier input from the bar code reader 14, and the part C sensitive to static electricity may be deviated from appropriate measures against static electricity. And a warning is given to the operator through the control computer 16.

FIG. 4 is a flowchart of the static electricity monitoring process in the control computer 16. FIG. 4 shows only the processing for one work area, but the same processing is executed in parallel for each work area. In FIG. 4, first, measured values such as the ground resistance of the worker, the charged potential of the worker, and the ground resistance of the work board are taken in (step 10).
00) Next, data representing the operation state of the device such as the ionizer 20 is fetched (step 1002). The barcode value is fetched from the barcode reader 14 (step 1004), and it is determined whether there is a change from the previous value (step 1006).

If there is no change, the process returns to step 1000 and repeats the processing of steps 1000, 1002, and 1004. If there is a change, it is determined that a new product has arrived at area C, (Step 1008). That is, regarding the ground resistance of the worker, the maximum value and the minimum value during the period when the product is present in the area C are calculated, and if it exceeds the limit value (for example, 10 MΩ and 1 MΩ), a flag indicating that is exceeded. Set. The maximum value is calculated for the charging potential of the worker, and the maximum value is calculated (for example,
If it exceeds V), a flag indicating that fact is set. If there is data indicating that the device operation state is abnormal, that fact is set. When these flags are set, the flags are simultaneously transmitted to the worker by means such as a buzzer and a lamp.

The result of the data processing is stored in the storage device together with the bar code value or the product number determined from the bar code value (step 1010).
Return to 0. As a result, when an abnormal value is observed in the grounding resistance and / or the charged potential of the worker, it is possible to identify the products considered to have been affected by the abnormal values. It is ensured that a proper process such as disposal is performed only for the former. Also, although not shown in the figure,
Data processing is performed on the measured values of the ground resistance and the charged potential for each worker, and suitability for the work is determined for each worker.

FIGS. 5 and 6 show the results of data processing on the ground resistance and the charged potential of the worker, respectively. In FIG. 5, when the product of the lot number “KE-1008” is in the process 2 in which the worker B works, the maximum value of the ground resistance is 18.17 MΩ, which exceeds the upper limit of 10 MΩ, and at the same time, In FIG. 6, the maximum value of the charging potential is 10
2.80 V, which exceeds the upper limit of 100 V. Therefore, it is understood that the product of the lot number “KE-1008” may have been affected by static electricity. The other products do not exceed the upper limit in any process and are not shown. However, the minimum value of the ground resistance of the worker is not less than the lower limit of 1 MΩ, and the ground resistance of the work board is not reduced. Also, since the operating state of the device was normal, it was guaranteed that the measures against static electricity were perfect.

FIG. 7 shows the result of calculating the maximum value of the grounding resistance per unit time (30 minutes) for each worker,
FIG. 8 is a graph thereof. from this result,
Worker B tends to have a high grounding resistance, and is determined to be unsuitable for this work.

[0018]

As described above, according to the present invention, there is provided a static electricity monitoring system capable of determining whether or not the static electricity environment is good for each product and each worker.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a static electricity monitoring system according to the present invention.

FIG. 2 is a diagram illustrating a connection for measuring a charging potential of an operator.

FIG. 3 is a diagram showing a measurement result of a charged potential of a human body when no countermeasures against static electricity are taken;

FIG. 4 is a flowchart of a static electricity monitoring process of the control computer.

FIG. 5 is a diagram showing a data processing result of a ground resistance of an operator.

FIG. 6 is a diagram illustrating a data processing result of a charging potential of an operator.

FIG. 7 is a diagram showing a result of data processing for each worker.

FIG. 8 is a graph showing a result of data processing for each worker.

[Explanation of symbols]

 14 bar code reader 18 conductive work board 20 ionizer 22 28 charging electrometer 24 wrist strap 26 monitor

Claims (4)

[Claims] 1. A means for collecting measured values relating to an electrostatic environment of each working area of a production line including a plurality of working areas as a time series, and applying the collected measured values to products existing in the working area at the time. An electrostatic monitoring system comprising: means for storing in association with each other; and means for classifying each product according to the associated measured value. 2. The system of claim 1, wherein the measurement includes a ground resistance of a worker in a work area. 3. The system according to claim 1, wherein the measured value includes a charged potential of a worker in a work area. 4. The system according to claim 2, further comprising means for processing the collected measurement values for each worker to determine suitability of each worker for a task.