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AOI X-Ray testing for PCB assembly pcba printed circuit assembly

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When a circuit board is soldered, checking whether the circuit board can work normally, usually do not directly supply power to the circuit board, but follow the steps

below:

1. Whether the connection is correct.

2. Whether the power supply is short-circuited.

3. Installation status of components.

4. Perform open circuit and short circuit tests first to ensure that there will be no short circuit after power on. The power-on test can only be started after the above hardware test before power-on is completed.

Testing-for-PCBA

Other work in electronic circuit debugging

1. Determine the test point

2. Set up a debugging workbench

3. Choose a measuring instrument

4. Debugging sequence

5. Overall debugging

Power-on detection

1. Power-on observation

2. Static debugging

3. Dynamic debugging

During the debugging process, it is necessary to carefully observe and analyze the experimental phenomena and make records to ensure the integrity and reliability of the experimental data.

Matters needing attention in circuit debugging

Whether the debugging result is correct is largely affected by whether the test volume is correct or not and the test accuracy. In order to ensure the test result, the test error must be reduced and the test

To test the accuracy, you need to pay attention to the following points:

1. Use the ground terminal of the test instrument correctly

2. The input impedance of the instrument used to measure the voltage must be much greater than the equivalent impedance of the measured place

3. The bandwidth of the test instrument must be greater than the bandwidth of the circuit under test.

4. Select the test point correctly

5. The measurement method should be convenient and feasible

6. In the process of debugging, not only must carefully observe and measure, but also be good at recording

 

Troubleshooting during debugging

Look for the cause of the fault carefully, and never remove the line and reinstall it once the fault cannot be resolved. Because if it is a problem in principle, it will not be solved even if you reinstall

 

Problem.

1. General method of fault inspection

2. Failure phenomenon and cause of failure

1) Common failure phenomenon: the amplifying circuit has no input signal but output waveform

2) The cause of the failure: the finalized product fails after a period of use, which may be due to damage to the components, short circuit or open circuit in the connection, or changes in conditions, etc.

3. General method to check failure

1) Direct observation method: Check whether the selection and use of the instrument are correct, whether the power supply voltage level and polarity meet the requirements; whether the polarity component pins are connected correctly,

Whether there is wrong connection, missing connection or mutual collision. Whether the wiring is reasonable; whether the printed board is short-circuited, whether the resistors and capacitors are burnt or burst. Power-on observation components have

No hot, smoking, burnt smell of the transformer, whether the filament of the electron tube and oscilloscope tube is on, whether there is high-voltage ignition, etc.

2) Check the static operating point with a multimeter: the power supply system of the electronic circuit, the DC operating status of the semiconductor transistor and the integrated block (including components, device pins, power voltage), resistance value in the circuit, etc. can be measured with a multimeter. When the measured value differs greatly from the normal value, the fault can be found after analysis.

By the way, the static operating point can also be measured with the oscilloscope "DC" input mode. The advantage of using an oscilloscope is that the internal resistance is high, and the DC working status and the signal waveform at the measuring point and the possible interference signal and noise voltage are more conducive to fault analysis.

3) Signal tracing method: For various more complex circuits, a signal of a certain amplitude and appropriate frequency can be connected to the input end (for example, for multi-stage amplifiers.


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