10 PCB maintenance inspection method and storage method

10 PCB maintenance inspection method and storage method
10 kinds of circuit board maintenance and detection methods
The maintenance and inspection methods of circuit boards are mainly divided into the following ten categories:
1. Off-line measurement
When the circuit board is not soldered into the circuit, compare the DC resistance between pins with the known normal DC resistance between pins of the circuit board of the same model to determine whether it is normal.
2. Online measurement
Measure whether the voltage, resistance and current values of each pin of the circuit board are normal on the circuit to determine whether the circuit board is damaged.
3. Alternative method
Replace the tested circuit board with a well-known circuit board of the same model and specification. It can determine whether there is a problem with the circuit board and repair the circuit board.
4. Separation test
Circuit board

A fault checking method used to separate circuit parts related to faults in electronic equipment, so as to define the scope of the circuit where the fault occurs. This method is to confirm some circuits and deny some circuits through multiple independent inspections, so as to gradually narrow the range of possible fault circuits until the fault location is found and the circuit board is repaired.
5. Signal injection
Different output signals of external signal sources are used as known test signals, and terminal indicators of electronic equipment under test are used to display test results. In the detection process, corresponding signal sources are selected according to specific requirements to obtain known signals of different quota; Check from the next stage to the previous stage, that is, inject a known signal from the input terminal of the terminal indicator of the equipment under test, and then move the circuit of the next stage to the circuit of the previous stage in turn. In the maintenance of industrial circuit board, known and different test signals are injected into the input terminals at all levels of the circuit to observe whether the response of the terminal surface indicator of the equipment under test is normal, so as to determine the location of the fault and analyze the cause of the fault.
6. Intuition check
Do not use any equipment or solder any circuit components. This is a method to check engine faults. PCB circuit boards are based on human intuitive vision to repair, smell, hear, and touch Visual inspection is the simplest method for equipment failure
7. Signal tracking method
With the help of oscilloscope, electronic voltmeter, etc., use a single test signal to check step by step from front to back. This method can deeply and quantitatively check all levels of circuits and quickly determine the fault location.
8. AC short circuit method
A method of bypassing a part of the circuit of the electronic equipment under test by using a capacitor with appropriate capacity and withstand voltage. It is applicable to judge the circuit components that generate power interference and parasitic oscillation in electronic equipment circuits.
9. Parameter test
A fault detection method for electronic equipment, which uses instruments to test the voltage value, current value, element value, equipment parameters, etc. in electronic equipment circuits. Usually, the resistance value is measured when the power is not on; Measure the voltage value and current value when power on; Or remove the components to measure the relevant parameters.
10. Waveform observation method
Use an oscilloscope to observe the waveform of the faulty components and related components of the electronic equipment; According to the difference between the measured waveform, amplitude parameter, time parameter and the normal waveform parameter of the electronic equipment, the failure cause is analyzed, and the circuit board repair measures are taken.
PCB board storage method
PCB board is subject to final product inspection. When waiting for shipment or not rushing to assemble finished products, PCB boards need to be stored at this time. Prevent the storage time from being too long, otherwise the product efficiency will be affected.
Vacuum packaging storage
PCB board shall not be in direct contact with water or exposed to humid air for a long time. At this time, we need to vacuum pack the PCB board, and wrap the packaging box with bubble film and place moisture-proof beads around it. Then mark and classify. Store in a dry and ventilated place away from direct sunlight.
Brush 3 anti paint
PCB boards with surface treatment such as gold dipping, electrogilding, tin spraying and silver plating can be stored for 6 months in general, and PCB boards with surface treatment such as silver dipping, tin plating and OSP can be stored for 3 months in general. It is recommended to apply a layer of conformal paint on PCB boards that have not been used for a long time. In this way, the storage life of PCB will be increased to about 9 months.
Temperature and humidity control
The temperature of the warehouse The storage temperature of polychlorinated biphenyls should be controlled at 23 ± 3 ° C, the relative humidity 55 ± 10%, the temperature under good storage conditions should be lower than 25 ° C, the relative humidity should be lower than 65%, and the indoor environment should be free of corrosive gases