Home > News > Methods for Testing PCB Circuit Boards: Look, Listen, Smell, Touch
 

Methods for Testing PCB Circuit Boards: Look, Listen, Smell, Touch


Calendar Icon April 10, 2025


When testing PCB circuit boards, paying attention to details is key to ensuring product quality. Here are nine important guidelines:


01 Nine Guidelines for PCB Testing

1.Safety Precautions: Never use grounded testing equipment to touch live television, audio, or video devices without an isolation transformer. Always confirm whether the device chassis is live to avoid short circuits and damage to integrated circuits.
2.Soldering Iron Safety: Do not use a soldering iron while it is live. Ensure the iron is not energized, ideally grounding the outer casing, and use a low-voltage soldering iron (6-8V) for increased safety.

3.Understand Integrated Circuit Principles: Before inspecting or repairing integrated circuits, familiarize yourself with their functions, internal structure, key electrical parameters, and pin functions. This will simplify analysis and inspection.
4.Avoid Pin Short Circuits: When measuring voltage or testing waveforms, ensure probes do not slip and cause short circuits between IC pins. Measurement should ideally be conducted on the surrounding printed circuit board.
5.Use High Internal Resistance Instruments: When measuring DC voltage on IC pins, select a multimeter with an internal resistance greater than 20KΩ/V to reduce measurement errors.


6.Heat Management for Power ICs:Ensure power integrated circuits have adequate cooling and do not operate at high power without heat sinks.


7.Proper Wiring:When connecting external components to replace damaged parts of integrated circuits, use small components and ensure proper wiring to avoid unnecessary parasitic coupling, especially in audio amplification circuits.


8.Ensure Soldering Quality:Confirm that solder joints are secure and avoid cold solder joints. Soldering time should generally not exceed 3 seconds, using a 25W internal thermal soldering iron. Check for short circuits between pins after soldering, and ensure no solder bridges exist before powering on.


9. Assess Integrated Circuit Status:Avoid hastily concluding that an integrated circuit is damaged. Voltage changes may be caused by issues in other circuits, and some soft faults may not cause noticeable changes in DC voltage.


02 PCB Debugging Methods

For a new PCB, first, check for visible issues such as cracks and short circuits. If necessary, verify that the resistance between the power supply and ground is sufficiently high. Debugging newly designed circuit boards can be challenging, especially when the board is large and contains many components. However, mastering effective debugging methods can enhance efficiency.


PCB Debugging Steps:

1.Initial Check: Inspect the PCB for visible cracks or short circuits and check the resistance between the power supply and ground if needed.

2.Component Installation: Install modules progressively, ensuring each one works correctly. Avoid installing all components at once. Start with the power section, then check the output voltage upon powering on.
3.Incremental Testing: After installing each module, perform voltage tests to ensure no components are damaged due to design or installation errors.


03 Methods for Identifying PCB Faults

1.Voltage Measurement Method: Confirm whether the voltage at each chip's power pin is normal, and check various reference voltages and operational voltages.
2.Signal Injection Method: Apply a signal to the input and measure the waveforms at each stage to locate faults. Sometimes, you can simply touch the input terminals with a tweezer to check for output responses, but ensure safety.

3.Other Inspection Methods:
Look: Check for visible mechanical damage to components, such as cracks or burn marks.
Listen: Listen for abnormal sounds during operation.
Smell: Check for unusual odors, such as burning or electrolyte smells.
Touch: Feel the temperature of components to ensure they are within normal ranges. Generally, power transistors and voltage regulators should operate below 70 degrees Celsius.



By following these methods, you can effectively test and debug PCB circuit boards, ensuring stable performance.


  

Previous PCB Stacking Structure & Four Key Parameters of Materials

Next Differences Between PCB Plated Holes and Via Holes