KR100801629B1 - Method for inspecting and repairing a PCB of atomic power plant facilities - Google Patents

Abstract

The present invention is a method for precisely inspecting the electronic circuit board performing the essential functions of the power generation facilities to ensure the stability and reliability of the nuclear power plant, and to determine whether there is a failure, and repaired if it is determined that the failure or failure is high Repairing to a board with normal performance. The present invention provides a test preparation step for cleaning the substrate to be inspected and removing the insulation coating of the soldered portion; Appearance structure inspection step of inspecting the attachment state between the electronic component and the PCB board; A component inspection step of individually inspecting the performance of important components; A functional test step of checking whether an output signal is normally output by applying an operating voltage and an input signal to the electronic circuit board, and determining the pass failure by estimating the test result and the board design data and the remaining life of the part in the part checking step. A pass rejection determination step and an insulation coating step of insulating coating the soldered portion of the electronic circuit board passed through the above steps are included.

Nuclear power plant, electronic circuit board, board parts inspection, ICT inspection.

Description

Method for inspecting and repairing a PCB of atomic power plant facilities}

1 is a flow chart for explaining the method of the present invention.

2 is a cross-sectional view of a fixture for using the ICT inspection equipment in the present invention.

The present invention relates to a method for precisely inspecting and maintaining an electronic circuit card of a nuclear power plant. In particular, if the quality is degraded as a result of the inspection, the method relates to repairing to normal performance.

In a plant that needs to be operated continuously for a year and a half or two years once the system starts to operate, such as a nuclear power plant, if the operation is stopped once due to an equipment failure or a breakdown of the control system, the system will be restored and restarted. This can be time-consuming and costly, and can cause serious damage to the entire power system, such as having to cut power outages in some areas if a breakdown occurs during the peak summer demand.

Therefore, when overhauling a nuclear power plant, an electronic circuit board (hereinafter, simply referred to as a "substrate") for various controls is removed from the system and inspected for quality. It is necessary to replace it with a substrate. Thus, there is no accidental shutdown, which increases the operating efficiency and ensures safe operation of the power system.

Since a nuclear power plant consists of about 40,000 devices, high-pressure pipes, cables, etc., it is necessary to design, manufacture, and install a large number of devices and components with sufficient quality for safe operation. In addition to regular inspections, there is a need to anticipate and eliminate the elements that cause the failure.

An object of the present invention is to ensure the safety and reliability of power plants by systematically and systematically performing a precise inspection and maintenance quality assurance system for electronic circuit boards of nuclear power plants.

An object of the present invention is to ensure the reliability of the electronic circuit board performing the essential functions of the power plant in order to secure the stability and reliability of the nuclear power plant, a method for judging whether or not the defect by precise inspection of the substrate, and judged as defective If the probability of failure or failure is high, it is intended to provide a way to repair it and repair it to a board of normal performance.

The present invention will be described in detail with reference to FIG. 1.

The present invention provides a quality inspection method for an electronic circuit board of a nuclear power plant, comprising: an inspection preparation step (10) for cleaning a substrate to be inspected and removing an insulation coating of a soldered portion; Exterior structural inspection step 20 to examine the attachment state between the electronic component and the PCB board; A component inspection step 30 for individually inspecting the performance of the critical components; A functional test step 40 of checking whether an output signal is normally output by applying an operating voltage and an input signal to the electronic circuit board; And an insulating coating step 70 for insulating coating the soldered portion of the electronic circuit board which has been determined to pass in the inspection steps. Then, the board repair step 60 for repairing the rejected board is added thereto, and the final functional test step for checking whether the output signal is normally output by applying an operating voltage and an input signal to the electronic circuit board after the insulation coating step ( 80) additionally.

In the inspection preparation step 10, the electronic circuit board to be inspected is sorted by type, washed, and then the coating layer of the soldered portion is removed. In this process, the electronic parts are carefully processed so as not to be damaged.

The substrate from which the coating film is removed is subjected to the external structural inspection step 20. At this time, the soldering state of the lead wires and the PCB board of the electronic component is visually observed, and the soldering is performed at a location that is difficult to judge with the naked eye or cannot be seen with visible light. If the condition is suspected, it is observed by infrared light to determine whether it is defective. With the naked eye, you can check for shortage of solder, damage to leads, discoloration or damage of parts, etc. Inspect Infrared imaging equipment uses inspection equipment that allows real-time viewing of cross sections directly on a monitor.

In the appearance and structure inspection, the board having no problem or the board in which the problem is not clear goes to the component inspection step 30, and if it is clearly defective, the component inspection is performed after repairing first.

In the component inspection step (30), the unit components are inspected by ICT inspection equipment while the circuits are connected to the electronic circuit board by soldering, and from the PCB substrate to individually inspect components having a plurality of leads such as semiconductor chips. Inspect separately to see if the component is within the limits of the performance specifications. Many components such as resistors, switches, capacitors, reactors, semiconductor devices, etc. are inspected while being attached to an electronic circuit board. For example, in the case of a capacitor, capacitance, leakage current, insulation resistance, frequency characteristics, etc. are measured.

For this test, a board test system called a Common Board Test System (BTS) or In_Circuit Test (ICT) is used. Inspection using this equipment requires a fixture as shown in FIG. 2 that matches each substrate, which is fabricated and used for each individual substrate.

The fixture includes a probe 12 for connecting a signal to each part lead of the substrate 11 to be inspected or a solder to which the lead is bonded, an individual pin 13 electrically connected to the probe, The first array plate 14 for fixing and supporting the probe at a specific position, and the contact point 16 of the individual pins so that the individual pins 13 are connected to the interface pin 15 for connecting the test signal of the ICT device. It has a second array plate 17 having a hole to penetrate, and a tooling pin 18 for facing the first array plate and the substrate to be inspected in position. The probe 12 is pointed at the tip and the probe 12 'is relatively wide at the end. These probes 12, 12 'and the individual pins 13 are connected by wires 19, respectively. The elastic member 9 is elastically contacted when the substrate 11 to be inspected and the first heat dissipation plate 14 are in contact with each other so that the probes and the solder and the leads of the substrate are not damaged from each other and the sealing function is performed during vacuum adsorption. Is installed. The individual pins 13 have a contact point 16 connected to the interface pins through a through hole formed in the insulating plate in order to connect with the interface pins 15.

Therefore, after the test target substrate 11 and the first array plate are matched to the predetermined position through the tooling pin 18 in a pore adsorption manner, the second array plate 17 and the interface pin 15 of the ICT defense are matched. After the test, the test is carried out.

Electronic components do not have a permanent lifetime, but a lifetime. In general, the failure pattern of components is divided into initial failure, accidental failure, and wear failure period. The curve representing the failure pattern is called the bass curve because it resembles the shape of a bathtub. The substrates in use are those that have gone through an initial failure period, and can be said to fail during the accidental failure period and the wear failure period. Contingent failure is caused by an accidental change in the environment or when there is a defect in something inside the part. This length of contingency failure is called the useful life (or useful life). After this accidental failure period, the part shows the shape of deterioration failure and enters the wear failure period. In the period of wear failure, the failure rate increases with the passage of time, so reaching this period can be regarded as the end of life. The failure of semiconductor parts such as ICs generally has a long service life. Among the device parts, the failure rate is dealt with. For example, aluminum electrolytic capacitors, relays, and the like are treated as typical of life-long parts. Although the service life and service life are highly dependent on the conditions of use, in particular, the aluminum electrolytic capacitor has a lifespan according to the law of Arenius (10 ° C 2 ° C: the service life is doubled every time the ambient temperature drops by 10 ° C). . The life of relays is almost determined by the voltage and current used. For this reason, care must be taken in the installation environment and conditions of use. The life of the aluminum electrolytic capacitor is doubled when the temperature is lowered by 10 ° C. according to the above-mentioned Arrhenius method. For this reason, the concept of a manufacturer's lifespan design may be different, so the lifespan under the conditions of use of the board may be significantly different. As conditions which influence the temperature of a capacitor, the board | substrate ambient temperature and load factor are mentioned. The higher the ambient temperature and the higher the load factor, the harsher the substrate, the shorter the life of the capacitor. The life of the relay is determined by the mechanical life determined by the physical stress applied to the movable part during operation, and the electrical life due to the interruption of the current and voltage flowing through the contact. In general, the life is determined by the electrical life. There are many. The electrical lifespan depends on the voltage and current used. Longer life can be expected by using them less than the rating. Moreover, the lifetime exists even in a transistor and a fuse. The factor that determines their lifetime is the temperature cycle. When used for frequent repeated acceleration and deceleration operations or for applications in which loads are applied intermittently, the component will repeatedly rise and fall in temperature. The rise and fall of this temperature causes the thermal expansion rate of the materials constituting the parts to be distorted, resulting in distortion and physical property degradation. In recent years, the service life of this temperature cycle has also been examined, so it is necessary to check with the substrate manufacturer to predict the life expectancy. In addition, the lifetime also exists in the plastic case constituting the IC, including the CPU. The electrons are greatly affected by aluminum migration, radiation investigation, etc., and also by the environment and vibration.

Therefore, the inspection of the unit parts must be performed inevitably, and the characteristic values for the performance inspection must be measured. In other words, the necessary characteristics such as operating current, voltage, resistance, capacitance, transistor, inductance, operating temperature, operating speed, etc. are measured in order to determine the difference from the prescribed value. In order to check that the chip is fixedly attached to the board such as an IC chip or a micro process, these chips are separated from the board and inspected by a logic circuit inspection device. The logic circuit tester checks the input / output logic of each chip to check whether there is an error operation.

In the functional inspection step 40 performed after the component inspection, the rated voltage and necessary input signals are input to the input terminal of the board, and then the normal output is inspected at the output terminal. If the normal output does not come out, it may be due to deterioration of the parts or poor soldering condition.

The checked and measured data is used in the pass failure determination step 50. By using the characteristic data of the unit parts, the degree of deterioration and secular variation of the parts are estimated, and the probability of leaving the specification within two years until the next overhaul. If it is estimated that it is out of the specification limit within that period, it is treated as a defective product and transferred to the board repair stage. Based on the data measured in the component inspection stage, the more inspection data and the accumulated inspection data in the previous stage, the higher the accuracy of the estimation. At least one previously examined data is needed to show how much degradation has occurred in approximately one overhaul cycle (about a year and a half) of a nuclear power plant. In addition to the comparison of these data, estimates of the remaining life of critical components are made using design data and general data indicating the life of the component itself. Based on this estimated lifetime, parts that are expected to degrade in less than two years are rejected. In nuclear power plants, devices that perform important functions have sufficient parallel redundancy and standby redundancy, but the ripple effect of a single card failure can be serious. Therefore, performance deterioration of major parts is more strictly judged than that of general parts. Apply.

In this way, the current and past measurement data of the electronic circuit board, the rating value, the design value, the importance of redundancy, etc. are comprehensively judged to determine whether the substrate passes. If it is determined that this is a failure, it is sent to the board repair step 60 for repair or disposal, and the board that passes is sent to the insulating coating step 70.

In the board repair step 60, the parts determined as defective parts are replaced with the normal parts. That is, remove the solder in the soldered state, remove it from the board and solder the normal parts again. Replace all defective parts.

The board passed in the pass rejection determination step 50 and the board repaired in the board repair step 60 are normally functionally coated again to prevent and insulate the board and the solder from deterioration.

In the insulating coating step (70) by coating in the same way as manufacturing an electronic circuit board to protect the substrate from the external environment.

The recovered substrates are inspected once more to see if they perform normal functions in the final functional inspection step 80, and when they pass, complete the detailed inspection process and are installed or stored at the power plant site.

The present invention can ensure the operation safety and reliability of the nuclear power plant and can help to establish a systematic maintenance quality assurance system.

In addition, according to the present invention, by inspecting an electronic circuit board that controls a number of devices of a nuclear power plant or manages safety at every overhaul period, it is not only broken but also replaces all the boards that are likely to fail. It has the effect of preventing it in advance and making the operation of the power plant efficient.

In particular, since the electronic circuit board is very expensive and the old one is difficult to hold or secure the maintenance board, the spare part can be repaired and the spare part can be economically saved.

In addition to the nuclear power plant, the present invention can be used to secure the reliability of the electronic circuit board of the facility that is required to always operate the equipment that requires extremely safety and reliability.

Claims (5)

As a method for overhauling and maintaining electronic circuit boards of nuclear power plants, An inspection preparation step of cleaning the substrate to be inspected and removing the insulation coating of the soldered portion; Appearance structure inspection step of inspecting the attachment state between the electronic component and the PCB board; A component inspection step of individually inspecting the performance of important components; A functional test step of checking whether an output signal is normally output by applying an operating voltage and an input signal to the electronic circuit board; A pass failure determination step of estimating a pass failure by estimating the test result and the board design data and the remaining life of the part in the part inspection step; Precision inspection method for electronic circuit board of nuclear power plant, characterized in that it comprises an insulation coating step of insulating coating the soldered portion of the electronic circuit board passed through the above steps. The method according to claim 1, In the external structure inspection step, first, by visually observing the soldering state of the lead wire of the electronic component and the PCB board, Soldering conditions in places that are difficult to judge with the naked eye or visible light are investigated by infrared thermal inspection equipment to determine whether they are defective. The method according to claim 1, In the component inspection step, the unit component is inspected by ICT inspection equipment while soldered to the electronic circuit board, and separated and inspected from the PCB board to individually inspect components having a plurality of leads such as semiconductor chips. Inspection method of nuclear power plant electronic circuit board characterized by collecting the measured data The method according to any one of claims 1, 2, 3, In the pass failure determination step, the remaining life of the important part is estimated based on the measurement data collected in the part inspection step and the board design ratings, and within two years even if the product is already defective or the current state is not defective. The parts that can be turned into defective parts include a repair process for repairing boards by replacing them with new parts. The method according to claim 4, After the insulation coating step, further comprising a final functional test step of checking whether the output signal is normally output by applying the operating voltage and the input signal to the electronic circuit board, nuclear power plant electronic circuit board precision inspection method

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