Whether it is for personal use or commercial applications, the defects of flexible circuit boards will cause serious adverse consequences. So, how to quickly detect the fault of flexible circuit board?
1. Determine fault location
Once there are signs of problems, the next step is to track and determine the location until the defect is identified. The different ways to determine the fault location include visual inspection and physical inspection using test equipment. Test technology depends on high-end test equipment or basic tools, such as multimeter, thermal imager, magnifying glass and oscilloscope.
2. Testing equipment
Typical equipment includes automatic flight detection instruments and automatic optical inspection (AOI) machines. AOI uses a high-resolution camera to inspect various defects, including short circuit, open circuit, missing, incorrect or misaligned components.
3. Visual and physical inspection
Visual inspection can identify defects such as overlapping traces, solder joint short circuits, signs of board overheating, and burned components. When some problems are difficult to identify with the naked eye, the magnifying glass can help identify some short circuits, welding bridges, open circuits, cracks in solder joints and circuit board wiring, component offsets, etc.
4. Special testing components
When low resistance is detected between the pins of components, the best way is to take the components out of the circuit of the flexible circuit board for special detection. If the resistance is still very low, then this component is the culprit. Otherwise, further investigation is required.
5. Power on the circuit board for detection
The visual inspection is only applicable to the appearance inspection of the circuit board, not to the internal layer inspection of the circuit board. If there are no obvious visible defects in the appearance, you need to power on the circuit board and perform more detailed tests to detect whether the circuit board is normal.
6. Low voltage measurement
This technology involves controlling the current amount of short-circuit current and finding out the current direction. Since the copper trace on the circuit board also has resistance, the voltage generated through different parts of the copper trace is also different. Using a voltmeter, when you measure the voltage between different parts along a short circuit, you find that the voltage value is getting smaller and smaller, and it is getting closer and closer to the short circuit.
7. Use your finger to sense the heating area of the circuit board
Because the short circuit will cause the local temperature of the circuit board to rise, finding the area with heat can help find the problem point of the short circuit. However, please be careful when using the power supply of the short-circuit copper trace, and avoid scalding or electric shock.
8. Repair short / open circuit
After identifying the short circuit or open circuit point on the flexible circuit board, the next step is to isolate the problem. Although it is easy to do this on the outer surface of the circuit board, it is a challenge for the inner layer. Possible solutions include drilling through holes or cutting appropriate external copper traces.