Ten commonly used detection methods for PCBA faults

Circuit board testing is divided into:

Dedicated circuit board test system: It is a test system developed for specific PCB test tasks or specific test objects. Often named according to the test object, such as BTS control board test, remote control circuit board test, energy meter circuit board test, etc.

General circuit board testing: It is a circuit board testing system developed for certain fields and PCBs under test. For example, Teradyne's C3065 series circuit board testing machine can complete the testing of nanoamp level circuit boards in space laboratories, and HBM's SmartA2000 circuit board testing system belongs to the general circuit board testing category.

Damage to an industrial control board PCB is usually caused by damage to a certain component, which may be a certain chip, a certain capacitor, or even a small resistor. The repair process is to find the damaged component and replace it. This seems simple, but in fact it requires profound knowledge, rich experience and necessary expensive testing equipment. In particular, to quickly find faulty components, in addition to rich experience, it also requires maintenance engineers to have quick thinking that is good at analysis and judgment. Below, we will introduce you to several circuit board detection methods:

1. Signal injection method:

This method uses different output signals of external signal sources as known test signals, and uses the terminal indicator of the electronic equipment under test to display the test results. When checking, select the corresponding signal source according to the specific requirements to obtain the known test results of different targets. The signal is checked from the downstream stage to the front stage, that is, a known signal is injected from the input end of the terminal indicator of the equipment under inspection, and then sequentially moved from the subsequent stage circuit to the front stage circuit. During the repair of industrial circuit boards, known and different test signals are injected into the input terminals of circuits at all levels, and at the same time, it is observed whether the response of the terminal indicator of the equipment under inspection is normal, as a basis for determining the presence of faults and analyzing the occurrence of faults. The basis for the reason.

2. Substitution method: refers to replacing the tested circuit board with a known and complete circuit board of the same model and standard, which can determine whether the circuit board is damaged.

3. Off-line measurement:

Refers to non-online measurement, when the circuit board is not soldered into the circuit, the DC resistance value between the pins is measured and compared with the known DC resistance value between the normal pins of the same type of circuit board repair to determine the DC resistance value between the pins. Is it normal?

4. Online measurement:

Refers to the online measurement method, which uses voltage measurement method, resistance measurement method, current measurement method, etc., to determine whether the circuit board repair is damaged by measuring the voltage value, resistance value and current value of each pin of the circuit board repair on the circuit to see if it is normal. .

5. Parameter test method:

It is an electronic equipment fault checking method that uses instruments (such as online maintenance testers) to test the voltage values, current values, component values, equipment parameters, etc. in the circuits of electronic equipment. Generally, the resistance value is measured when the power is off, the voltage value and current value are measured when the power is on, or the components are removed to measure their related parameters.

6. Waveform survey method:

This is a dynamic detection method for electronic equipment. It relies on an oscilloscope to observe the waveform of the faulty part or related parts of the electronic equipment, and based on the difference between the tested waveform shape, fluctuation parameters, time parameters and the normal waveform parameters of the electronic equipment, it analyzes the cause of the fault and takes maintenance measures. In the repair of industrial control circuit boards Waveform observation method is a very important and quantitative testing and maintenance method.

7. Intuitive viewing method:

This method refers to a method that uses human intuition - vision, smell, hearing and touch to check the fault location of the circuit board to be repaired without using any equipment or soldering any circuit components. Intuitive inspection method is the simplest method of equipment failure. This method can be divided into two types: energized inspection method and non-energized inspection method.

8. Signal tracing method:

This method is to use a single test signal and use test instruments (such as oscilloscopes, electronic voltmeters, etc.) to check (trace) step by step from front to back. This method can conduct in-depth quantitative inspection of circuits at all levels and quickly determine the location of the fault.

9. Communication short circuit method:

Also known as the capacitor bypass method, it is a method of using capacitors with appropriate capacity and withstand voltage to bypass a certain part of the circuit of the electronic equipment being inspected. This is a relatively quick and simple method of fault inspection. The AC short circuit method is suitable for identifying circuit locations where power interference and parasitic oscillations occur in electronic equipment circuits.

10. Separation test method:

Also known as the circuit segmentation method, it is a fault checking method that reasonably separates the fault-related circuits in electronic equipment part by part in order to clarify the scope of the circuit where the fault is located. This method is to confirm part of the circuit and deny part of the circuit through multiple separate inspections, thus step by step narrowing the scope of the circuit where the fault may occur until the fault location is found.