Everything You Need To Know About PCB Inspection

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The fabrication and manufacturing of printed circuit boards is a complex process. PCBs are designed by placing different electrical components within a tightly constrained space. Hence, it is essential to test the PCB for any possible faults or errors, leading to the malfunctioning of the circuit boards. PCB inspection best practices enable the OEMs to optimize the functioning of the PCB to its full potential. 

Performing robust inspection in the design, manufacturing, and assembly processes helps to ensure that the PCB meets the specified standards. As the PCBs are becoming more advanced, the manufacturers need to deploy stringent inspection strategies to establish that the PCB is of supreme quality. It helps highlight defects and rectifies them on time before proceeding to the next stage in the production process. Using a PCB inspection system on the output of the soldering process also helps eliminate any problem from occurring again, hence improving the efficiency of the circuit board. In addition, PCB inspection helps to reduce the chance of failure and maintain customer satisfaction.

You need to test the PCBs to verify their electrical conductivity, mechanical strength, soldering quality, cleanliness, lamination, hole wall quality, component placement and polarity, and more. It helps to address the gaps in the PCB before it goes into final production, hence saving time and money. Improper application of solder paste and wrong positioning of components can impact the board’s performance and lifespan. The OEMs can undergo appropriate PCB inspection training to conduct robust in-house testing. While carrying out a PCB inspection, you need to keep track of the following points.

Components You Should Test

A printed circuit board consists of various complex components, including capacitors, resistors, transistors, diodes, and fuses. You need to comprehensibly test these parts to identify if there are any errors and malfunctions. While testing the capacitors, you need to apply voltage to ensure that it delivers desirable functions. If the outcome is not satisfactory, either a short leak or the capacitor does not work. A diode is a sensitive component. Hence it is advisable to consult an expert to prevent damage. For testing resistors, you require an ohmmeter. If it records high readings, it may have an open resistor. You need to monitor the functioning of each component of your PCB.

Manual PCB Inspection 

Manual visual inspection or MVI is the simplest form of PCB inspection. The inspector visually inspects the board assembly to identify the issues. Then, they compare the board with the design documents to ensure that the board meets the listed specifications. You can perform the MVI after every step of the PCB fabrication and assembly process. MVI typically includes inspection of the board’s thickness, surface roughness, assembly dimensions related to electric connectors, integrity, clearness of conductive patterns, and checking for surface quality. MVI does not require any specialized types of equipment. However, you need human resources to carry out this kind of testing. The drawback of manual inspection is that it has limited capabilities in identifying different error types.

AOI PCB Inspection

In Automated Optical Machine (AOI) inspection method, a machine carries out the visual inspection of the PCB. It uses various light sources and one or more still or video cameras to image an exemplary assembly. The machine compares both images to identify faults or issues. 2D AOI machine makes use of colored lighting from multiple angles and side-angle cameras for inspecting components. 3D AOI equipment has the potential to measure component height accurately. An AOI machine can identify minor and complex defects, including bridging, insufficient solder, and damaged parts.

AXI PCB Inspection

Because of the increasing complexity of PCB boards that feature smaller components and chip packages such as BGAs and chip-scale packages (CSPs), it becomes difficult to view the solder connections. Automated X-Ray Inspection, AXI is capable of viewing the solder joints under the chip. The materials can absorb x-rays based on their atomic weight. Lighter elements absorb less, while heavier elements absorb more, enabling you to distinguish the materials easily. Hence, X-ray inspection is ideal for more complex boards. However, it is an expensive inspection technique.

Automatic Laser Test Measurement

Automatic laser test (ALT) measurement helps to measure solder joints dimension, solder joint deposition, and reflectivity of different parts. It uses laser technology to measure these aspects. Hence, ALT measurement is ideal for defining the quantity and position of solder paste deposition. In addition, it helps validate that the solder paste printing has produced proper alignment, viscosity, and board cleanliness.

To Conclude:

These inspection techniques help PCB assemblers to ensure the quality of the circuit board. It helps to assess the PCB for the correct number, size, and placement of components. PCB testing is crucial for minimizing waste, reducing returned products, and optimizing board safety. If the developer does not practice the inspection and testing strategy, it can significantly decrease the profit margins and result in unhappy customers and product liability lawsuits. Hence, it is essential to create a robust inspection plan to develop a high-quality product.

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