A Comprehensive Guide On Finding A Faulty Components In PCB

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PCB or Printed Circuit Boards plays an important role in electronic devices as they form the primary part of the device’s functionality and a platform for component placement to operate the circuits. However, similar to any other electronic devices, these PCB components can also experience faults. Hence, it becomes essential to identify and eliminate these components for the optimal performance and reliability of the system. Therefore, this blog serves as a comprehensive guide on finding faulty components in PCB.

Finding Faulty Components In PCB: Manually (Visual Inspection)

Follow the below suggested steps to find faulty components in PCB

  1. The foremost step is to turn-off the power flowing to the board before the examination. Also, ensure to disconnect the power cord present in the AC outlet.
  1. The next step is to identify the fuses where you have to use long pliers to pull out the fuses present within the board. Check for the glass fuses and identify the if it is fused by looking into the filament. In the case of  ceramic fuses, use a multimeter where the probes of the multimeter need to touch the ceramic fuse.
  1. Thirdly, you can conduct a visual inspection by looking over the PCB board for inappropriate connections or components that are overheated. The components that are overheated have burnt marks while inappropriate components look bulged or dull, indicating error. 
  1. Now, turn-on the power for the circuit check for the hot spots on the PCB board to identify the connections that are inappropriate or faulty. However, make sure not to put your hands directly over the PCB circuit to avoid the shock.
  1. Use a multimeter to check the individual components such as capacitor, resistor, and many more. Moreover, each component should show the value below its original value and higher value indicates an issue.

Capacitors:

While checking for capacitors check for fuses, expanded or blown caps. In addition, use a multimeter for a continuity check and switch the leads of the multimeter to check changes in resistance. You can also remove the capacitors and check for their capacitance.

Diodes:

In case of diodes use the multimeter to measure the voltage by placing the negative probe on the cathode and positive probe on the anode. The voltage should be measured as 1V (LEDs) or from 0.1V (Schottky) to 0.7V (rectifier).

BJT Transistors:

For finding faulty components in BJT transistors, check on the board using a diode function on a multimeter. Firstly, to determine whether the diode is working appropriately, find the base pin as it varies as per packages. Also, once you find the base pin and it is NPN diode ensure to have a negative probe on emitter or collector and positive probe on base to check it receives ~0.7V.  If it is PNP the polarity should be reversed.

Coils:

In case of coils, the resistance should be measured which is small and not zero. If the coil resistance is higher check using LCR meter.

Transformers:

The transformers resistance is measured similarly to the coils and the user can identify the secondary and primary coil based on the pad layout. Usually, the primary coil has high resistance compared to the secondary coils. Also, ensure the circuit has no open connection or internal fuses. 

Resistors:

For finding faulty connections in the resistors, first inspect visually for the burn outs or damages.

  1. After checking the different types of components, check out for the Integrated Circuits or IC’s by comparing them with the existing and functional IC’s. In case the IC’s are socketed, replace the individual IC’s with the spare ones. Now test the replaced IC’s by passing the electricity and if it works properly than the previous time, the your IC was defective.
  1. Now, check for the power supply using a multimeter and ensure that your expected value matches with the specifications specified on components. Also, a 0V indicates a short circuit.
  1. Finally, compare your circuit boards with the functional ones to look out for burnouts and components that are misplaced. Also, use a multimeter to compare the component behavior and values. 
  1. For circuits that have complex designs and connections, choose signal probing using a waveform capture system and multimeter.

Apart from visually identifying the faulty components, you can also use an automated device for inspection, compare with the identical board, or use flying probe testing. 

Using OrCAD X:

You can also use the advanced version of the PCB system known as OrCAD X to find faulty components and make your board more reliable.

DRC Or Design Rule Checks:

This tool allows you to automatically check the PCB design as per the pre-defined rules reducing the manufacturing defects and design as per rule in real-time.

Constraint Management

This tool allows you to manage the design setting and manage the design as per the constraints thereby reducing the errors and increasing the reliability of design.

Live Bill Of materials Or BOM:

Through OrCAD you can real-time analysis and updates on the bill on materials to select the low-risk, compliant, and available components for your PCB design.

Checks After Assembly:

With the help of OrCAD X you can check the assembly issues and adjust the placements for smooth and error-free assembly PCB design.

DFT & DFA Constraints:

DFT or Design for Test and Design for Assembly or DFA are the constraints offered by OrCAD X right component placement, spacing, and testing for minimizing assembly errors.

Hence, by applying these strategies you can ensure that your device is well-optimized and performs exceptionally. However, for professional support choose Sunstream for PCB design services as we use advanced PCB softwares like OrCAD X and Allegro PCB Editor to meet the industry standards and quality.