CN101226159A - Method and system for detecting circuit board contamination - Google Patents

Abstract

The invention relates to a communication device, in particular to a communication device safety check technique, which discloses a circuit board pollution check method and a relative system, for resolving the problem of prior art which is lack of quantitative check method to judge the pollution degree of circuit board to cause low accuracy. The inventive method comprises checking the surface insulated resistance value of an object circuit board, comparing the surface insulated resistance value with one resistance threshold value, while the environment relative humidity is set as humidity threshold value, judging the resistance threshold value is the minimum surface insulated resistance value higher than the value at the safe operation of the circuit board, and when the surface insulated resistance value is not higher than the resistance threshold value, judging the circuit board has surface pollution. The inventive system comprises an insulated resistance check circuit and a first comparison circuit.

Description

Method and system for detecting circuit board contamination

technical field

The invention relates to communication equipment, in particular to the detection technology of communication equipment, and discloses a circuit board pollution detection method and system.

Background technique

Due to the serious air pollution in recent years, there is a lot of dust in the air, coupled with the limitation of the environmental conditions of the communication equipment room, the operation of the equipment air supply system, the renovation and decoration of the machine room, etc., the precision electronic equipment under long-term continuous operation will be in the air. A certain amount of dust is covered within a certain period of time. When the dust accumulates to a certain extent, it will have a negative impact on the reliable operation of the equipment.

In addition, in order to reduce manufacturing costs and operating costs in recent years, many equipment suppliers have launched unsealed outdoor communication equipment and electronic equipment, which makes it easier for harmful dust to enter outdoor communication equipment and electronic equipment, and dust is more easily in the air. A large amount of accumulation on the circuit board will affect the operation reliability of these electronic devices to a certain extent, and in severe cases will cause the circuit board to fail and be paralyzed.

In order to remove dust to improve the reliability of communication equipment or electronic equipment, there are two solutions in the prior art: one is charged cleaning; the other is on-site off-line cleaning.

But when implementing in the prior art, because when judging whether to clean, arbitrariness and subjectivity are too strong, so there are following disadvantages:

Since the user judges whether cleaning is required based on factors such as the operating time of the equipment, the frequency of unexplained failures, or the contaminated appearance of the circuit board, the judgment is too arbitrary and subjective, and lacks scientific basis;

Because it is too subjective, it is easy to cause too frequent cleaning of the circuit board. In addition to increasing the cleaning cost of users, cleaning the circuit board too frequently is more important because quite a lot of non-standard live cleaning projects not only have poor cleaning effect, but will cause damage to the circuit board and affect the normal operation of the equipment. It may even lead to paralysis of the equipment and cause permanent damage to the equipment.

Contents of the invention

Embodiments of the present invention provide a circuit board contamination detection method and system to solve the poor accuracy in judging the degree of contamination of the circuit board caused by arbitrariness and subjectivity in judging the degree of contamination of the circuit board in the prior art The problem.

A method for detecting contamination on the surface of a circuit board, comprising the steps of:

Detect the surface insulation resistance value of the circuit board;

Comparing the surface insulation resistance value and the resistance threshold value, when the relative humidity of the environment is the set humidity threshold value, the resistance threshold value is greater than the minimum surface insulation resistance value required for safe operation of the circuit board;

When the surface insulation resistance is equal to or less than the resistance threshold, it is determined that the surface of the circuit board is polluted.

Embodiments of the present invention also provide a detection system for surface contamination of a circuit board, comprising:

The insulation resistance detection circuit is used to detect the surface insulation resistance value of the circuit board;

The first comparison circuit receives the detection signal from the insulation resistance detection circuit, and determines that the surface of the circuit board is polluted when the detected surface insulation resistance is equal to or less than a resistance threshold value.

The beneficial effects of the present invention are as follows:

1. The method of the present invention utilizes the relationship between the surface insulation resistance of the circuit board and the degree of ion pollution, and achieves the purpose of quantitatively detecting the degree of ion pollution by detecting the surface insulation resistance of the circuit board, effectively reminding the user to carry out electronic equipment and communication in time when necessary. Cleaning of equipment to improve operational reliability of electronic equipment and communication equipment;

2. At the same time, using the principle that the dust thickness has a certain influence on the heat dissipation of the circuit board, the temperature detection device is used to quantify and judge the dust accumulation thickness, so as to ensure that the dust composition and the relative humidity of the environment have little influence on the surface insulation resistance, and the alarm signal can still be issued in time remind the user;

3. The technical solution of the present invention provides equipment manufacturers with quantitative standards for understanding the pollution of circuit boards at the operating site, which is conducive to controlling reasonable cleaning frequency, saving maintenance costs, and avoiding excessive frequent cleaning of electronic equipment and communication equipment in the network. Risks caused by service switching during operation.

Description of drawings

Fig. 1 is a schematic structural diagram of the circuit board pollution detection system of the present invention;

Fig. 2 is a schematic diagram of the insulation resistance of the communication circuit board under different environmental relative humidity;

Fig. 3 is a schematic diagram of insulation resistance at different pollution degrees under the same ambient relative humidity;

Fig. 4 is a circuit structure diagram for monitoring the pollution according to the change of the surface insulation resistance of the circuit board.

Detailed ways

Before specifically introducing the circuit board pollution detection and alarm method and system of the present invention, some factors that will affect the judgment are introduced:

In fact, when judging whether it is necessary to clean, we should not only rely on the dust of the equipment to pollute the appearance, but also judge the chemical composition and humidity of the substances in the dust, as follows:

1. When the chemical composition of the dust is mainly neutral and insoluble in water, and the humidity in the area is relatively low, even if there is a high accumulation on the circuit board, it will generally not cause equipment corrosion and cause failure, that is In this case, the frequency of cleaning should be low, and cleaning is only required when the thickness of the dust is so large that it may affect the heat dissipation of the heat-generating device.

2. When the chemical composition of the dust contains a large amount of halogen salts and the relative humidity is high or the temperature difference between day and night is large, condensation may occur on the surface of the circuit board. At this time, even if the accumulated dust on the surface of the equipment and the circuit board is not serious, it is still possible. Cause equipment corrosion and trigger failure. At this time, not only cleaning is required, but also coating (Conformal Coating) may be required to try to reduce the relative humidity inside the equipment.

3. When there are few corrosive salts in the dust and the environment is dry, cleaning may not be necessary, but in humid areas, because the dust has a large total surface area, it may absorb a large amount of water vapor and corrosive gases and corrode the equipment and affect the equipment. To ensure the reliability of the operation of the equipment, it is necessary to clean the equipment.

It can be known from the above analysis that because the environment in which the circuit board is located is very complex, the purpose of the present invention is to accurately judge whether cleaning should be performed, and provide objective and scientific judgment standards through quantification.

The research shows that the important factor affecting the reliable operation of the circuit board is the insulation resistance on the surface of the circuit board. When the insulation resistance value is too small, it is very easy to generate noise, malfunction, and even cause short-circuit accidents. The change of the insulation resistance value is directly related to the degree of pollution. When the salt in the dust accumulated on the surface of the circuit board reaches a certain amount, the insulation resistance value will decrease accordingly, and the more salt in the dust, the more the circuit board will be damaged. The smaller the insulation resistance value of the board surface, it can be seen that when the dust containing the salt substances accumulates to a certain extent, it must be cleaned to ensure the insulation resistance value of the board surface.

At the same time, under the same pollution conditions, the greater the relative humidity on the surface of the circuit board, the smaller the surface insulation resistance; The method of humidity can improve the insulation resistance without cleaning the surface of the circuit board.

The specific changes are shown in Figure 2 and Figure 3 below: As shown in Figure 2, Figure 2 shows the change of the surface insulation resistance of the circuit board under different relative humidity under the same pollution conditions, where: the ordinate is the measured The surface insulation resistance, the abscissa is the change of the relative humidity of the environment. It can be seen that after the circuit board accumulates a certain amount of dust, the greater the relative humidity of the environment, the smaller the surface insulation resistance of the circuit board.

Please refer to Figure 3, when the relative humidity of the environment is fixed, the surface insulation resistance of the circuit board decreases with the increase of the pollution degree.

From the above analysis, it can be seen that the change of the surface insulation resistance of the circuit board can directly reflect the pollution of the circuit board under a certain relative humidity of the environment, so the surface insulation resistance of the circuit board can be used as a quantitative value to measure the pollution degree of the circuit board to judge the degree of pollution.

For this reason, the present invention provides the technical scheme based on following basic principle, comprises steps:

1. Monitor the surface insulation resistance value when the circuit board is running;

Monitoring the easily polluted circuit board in the equipment can realize the detection of the pollution of the entire equipment. The easily polluted circuit board is generally located at the air inlet of the equipment cooling air. According to the relationship between the degree of pollution and the surface insulation resistance of the circuit board, the measurement method is: set the surface insulation test on the part where dust is most likely to accumulate on each circuit board (or a certain functional board of each subrack), that is, the cooling windward side. The resistance change circuit can use any currently commonly used circuit pattern (parallel lines and comb electrodes, etc.), the surface insulation resistance detection circuit must be exposed to the air (or cooling airflow), without solder mask and other substances Coverage, otherwise it will affect the sensor to perceive the change of pollution degree.

2. Determine whether the surface insulation resistance of the circuit board has dropped to the set resistance threshold;

According to the characteristics of electronic equipment and communication equipment, the threshold value of the change of the surface insulation resistance of the circuit board is set. In general, in order to ensure the safety performance of the circuit board under various operating conditions, the surface insulation of the circuit board should be selected in the highest relative humidity environment where the circuit board can operate. The resistance minimum is the resistance threshold. For example: when the relative humidity is 85% RH, when the detection distance is 0.318mm, the minimum value of surface insulation resistance should be between 3.00E+6Ω～1.00E+7Ω/0.318mm (it can also be marked by leakage current picoampere PA) .

3. When the surface insulation resistance value of the circuit board is equal to or lower than the set resistance threshold, an alarm will be issued.

When the set threshold is reached, an alarm signal is reported. In general, the user can go to the equipment site to confirm after receiving multiple alarm signals. Whether there is too much dust on the equipment, the relative humidity is too high, or there is condensation on the circuit board. For rainwater dripping, users can decide whether to clean the equipment, try to reduce the relative humidity of the operating environment, or find the source of dripping to eliminate hidden dangers that affect operational reliability.

In some operating environments of the circuit board, since the dust may not contain too much salt, it has little effect on the surface insulation resistance of the circuit board, but at this time the normal heat dissipation of the circuit board is affected, and it is still necessary to The circuit board is cleaned. Therefore, in addition to using a sensor for surface insulation resistance change at a specific position on the circuit board to monitor the degree of dust pollution on the circuit board, according to the principle that too much dust will affect the heat dissipation of the circuit board, it is also possible to install a sensor at a specific position on the circuit board Set up a temperature sensor for detection. When the accumulation of dust increases, the dry dust will affect heat dissipation and increase the temperature sensed by the temperature sensor. Install a heating element at the position where the device first contacts the cooling airflow circuit board. When the dust increases, it will affect Its heat dissipation makes the temperature rise. When the temperature of the heating element is higher than the ambient temperature by a certain threshold, it means that the dust has seriously affected the heat dissipation. At this time, an alarm should be issued to remind the user to go to the site to investigate and check that it is indeed dust on the circuit board. More, decide whether cleaning of electronic equipment and communication equipment is required. The temperature threshold is set according to the power of the specific heating element. According to experience, it can be set according to the following principles:

1) In an environment with stable temperature, the temperature threshold = ambient temperature + 1-2 degrees Celsius;

2) In an environment with unstable temperature, the temperature threshold = ambient temperature + 2-5 degrees Celsius.

The circuit structure for realizing the above method is shown in Figure 1, including: a detection circuit 1, a comparison circuit 2 connected to the detection circuit 1, an alarm display circuit 3 connected to the comparison circuit 2, and a remote center connected to the alarm display circuit 3 through a transmission network The monitoring circuit 4 and the remote center monitoring circuit 4 are generally arranged centrally in the monitoring room of the communication system to perform centralized monitoring of the entire communication system.

The detection circuit 1 includes a circuit 101 for detecting the surface insulation resistance of a circuit board and a circuit 102 for detecting temperature change. After the dust enters the device with the airflow, it is attracted by the static electricity of the circuit board, and most of it settles on the side of the circuit board facing the cooling wind. Therefore, the edge of the circuit board cooling side facing the wind receives the most serious dust pollution, so the detection circuit should be set in The edge of the circuit board facing the side of the cooling air, the direction of the cooling air is shown by the arrow in Figure 1, so that the purpose of monitoring the entire circuit board can be achieved. For the pollution of the entire equipment, since the circuit board at the tuyere is the most It is easy to be polluted, so detecting the circuit board at the tuyere can achieve the purpose of monitoring the entire equipment.

The surface insulation resistance detection circuit 101 can use any currently commonly used circuit pattern (parallel line, rotary line or comb-shaped electrode, etc.), directly design it in the wiring pattern and print it on the printed circuit board or print it on the printed circuit board. After being soldered to the board, the surface insulation resistance detection circuit 101 must be exposed to the air (or cooling airflow), and must not be covered with solder resist ink (Sold Mask) or other substances, otherwise it will affect the change of the sensor's perception of pollution. The working power required by the detection circuit 101 to detect the surface insulation resistance is provided by the comparison circuit 2 , and the detection result is input into the comparison circuit 2 .

The surface temperature detection circuit 102 includes a constant power heating element, such as a diode or a triode, and a first temperature sensor for detecting the operating temperature of the constant power heating element and a second temperature sensor for detecting the ambient temperature. The temperature sensing device can be controlled directly by using the detection results, without having to separately install the first temperature sensor. The power heating element and the first temperature sensor can be directly arranged on the cooling windward side of the circuit board, or an insulating plate perpendicular to the cooling wind direction can be fixedly connected to the edge of the circuit board, and the constant power heating element and the temperature sensor can be fixed on the On the windward side, the detection result of the temperature sensor is input into the comparison circuit 2 for judgment.

The comparison circuit 2 includes a first comparison sub-circuit 201 for comparing whether the insulation resistance is lower than a set resistance threshold, and a second comparison sub-circuit 201 for comparing whether the difference between the operating temperature of the constant power element and the ambient temperature exceeds the set temperature threshold. The comparison sub-circuit 202, whose output is connected to the alarm display circuit 3 in parallel, when the insulation resistance is equal to or less than the set resistance threshold, or the difference between the operating temperature of the constant power element and the ambient temperature is equal to or higher than the set temperature threshold , outputting an alarm signal to the alarm display circuit 3 to trigger an alarm. The alarm mode can include common forms such as sound and light. After the alarm circuit 3 receives the alarm signal, it transmits it to the remote monitoring center through the communication network for remote alarm display.

There are many circuit structures that control according to the change of insulation resistance, and the following only takes one of the circuit structures as an example to illustrate:

As shown in Figure 4, Figure 4 is an insulation resistance detection and comparison circuit, including three standard resistances Rs, and the detected insulation resistance Rx form a bridge, the a and c terminals are respectively connected to the two electrodes of the detection circuit 101, and the test voltage V _DC is added to terminals a and b of the bridge, terminal c is grounded, terminal d is connected to the non-inverting input terminal of the voltage comparator, and the set voltage Ur applied to the inverting input terminal of the voltage comparator is: when Rx is The voltage output from terminals c and d at the lowest set threshold, the set voltage can be obtained through actual testing. The working process of the circuit is: when the circuit board is polluted, the insulation resistance Rx decreases, and the voltage value input to the positive-phase input terminal increases. Once the insulation resistance Rx is lower than the set threshold, the voltage value of the positive-phase input terminal of the voltage comparator is equal to or exceeds the set voltage, at this time, the output terminal of the voltage comparator outputs a signal to control the alarm display device to give an alarm, such as the alarm light shown in the figure.

The higher the test voltage V _DC is, the higher the test accuracy is. According to the actual power supply configuration of the equipment, the highest DC power supply is generally selected.

There are many ways to realize the control by using the difference between the two temperatures. It can be realized by a hardware circuit composed of a voltage comparator, or by software control, which is well known to those skilled in the art and will not be repeated here.

The beneficial effects brought by the technical solution of the present invention are as follows:

1. The method of the present invention utilizes the relationship between the surface insulation resistance of the circuit board and the degree of ion pollution, and achieves the purpose of quantitatively detecting the degree of ion pollution by detecting the surface insulation resistance of the circuit board, effectively reminding the user to carry out electronic equipment and communication in time when necessary. Cleaning of equipment to improve operational reliability of electronic equipment and communication equipment;

2. At the same time, use the principle that the dust thickness has a certain influence on the heat dissipation of the circuit board, and use the temperature detection device to quantify and judge the dust accumulation thickness, so as to ensure that the dust composition and the relative humidity of the environment have little influence on the surface insulation resistance, and send an alarm signal in time to remind the user ;

3. The technical solution of the present invention provides equipment manufacturers with quantitative standards for understanding the pollution of circuit boards at the operating site, which is conducive to controlling reasonable cleaning frequency, saving maintenance costs, and avoiding excessive cleaning of electronic equipment and communication equipment. The risk of switching services brought about by operation.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (16)

1. a detection method for circuit board surface contamination, is characterized in that, comprises the steps: Detect the surface insulation resistance value of the circuit board; Comparing the surface insulation resistance value and the resistance threshold value, when the relative humidity of the environment is the set humidity threshold value, the resistance threshold value is greater than the minimum surface insulation resistance value required for safe operation of the circuit board; When the surface insulation resistance is equal to or less than the resistance threshold, it is determined that the surface of the circuit board is polluted. 2. The method according to claim 1, characterized in that, after determining that the surface of the circuit board is polluted when the surface insulation resistance is equal to or less than the resistance threshold value, it further comprises the step of: sending out according to the determination result warning signal. 3. The method according to claim 1, wherein the humidity threshold value is a humidity value of the environment with the highest relative humidity in which the circuit board can operate. 4. The method according to claim 1, wherein the set humidity threshold is less than or equal to 85% RH. 5. The method according to claim 1 or 4, characterized in that, when the relative humidity threshold is 85% RH, the required minimum surface insulation resistance ranges from 3.00E+6Ω to 1.00E+7Ω. 6. The method according to claim 1, characterized in that, while detecting the surface insulation resistance value of the circuit board, the operating temperature of the constant power element on the surface of the circuit board and the ambient temperature of the circuit board are also detected; calculating the difference between said operating temperature and ambient temperature; When the temperature difference is equal to or greater than the set temperature threshold, it is determined that the surface of the circuit board is polluted. 7. The method according to claim 6, characterized in that, after determining that the surface of the circuit board is polluted when the temperature difference is equal to or greater than the set temperature threshold value, it further comprises the step of: according to the determination The result is a warning signal. 8. The method according to claim 6, wherein the temperature threshold=environmental temperature+1-2 degrees Celsius; or, the temperature threshold=environmental temperature+2-5 degrees Celsius. 9 . The method according to claim 6 , wherein the position for detecting the insulation resistance of the surface of the circuit board and/or the surface temperature of the thermostatic element is: the edge of the surface of the circuit board facing the cooling air. 10. A detection system for surface contamination of a circuit board, comprising: The insulation resistance detection circuit is used to detect the surface insulation resistance value of the circuit board; The first comparison circuit receives the detection signal from the insulation resistance detection circuit, and determines that the surface of the circuit board is polluted when the detected surface insulation resistance is equal to or less than a resistance threshold value. 11. The system according to claim 10, wherein the insulation resistance detection circuit is arranged at the edge of the side of the surface of the circuit board facing the cooling wind. 12. The system according to claim 10, wherein the insulation resistance detection circuit is two parallel rotating wires or comb electrodes printed or soldered on the circuit board. 13. The system according to claim 10, characterized in that: the system further comprises: a constant power element arranged on the surface of the circuit board; A first temperature sensor that detects the operating temperature of the constant power element and a second temperature sensor that detects the ambient temperature of the circuit board; The second comparison circuit receives the detection signals of the first temperature sensor and the second temperature sensor, and judges that the circuit is Board surface is contaminated. 14. The system according to claim 13, wherein the constant power element and the temperature sensor are fixed on the side of the circuit board facing the cooling air. 15. The system according to claim 13, further comprising: an alarm circuit, connected to the first comparison circuit and the second comparison circuit, for sending out an alarm signal according to the determination result. 16. The system according to claim 15, further comprising: a remote monitoring circuit connected to the alarm circuit through a communication network for remote alarm display.

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