Key PCB Inspection Methods for Quality Assurance

Apr 23,2019

High-quality printed circuit boards (PCBs) have become a major requirement in the electronics industry that depends on them. These PCBs serve as the integral component of various electronics. So, if they fail to perform due to manufacturing errors, the smooth functioning of various electronic devices will be at stake. To avoid these, nowadays, PCB manufacturers and assembly services are performing various types of inspections on PCBs during different phases of manufacturing. This post discusses various PCB inspection techniques and the types of defects analyzed by them.

Important PCB Inspection Methods Discussed in Detail

Today, due to the increasing complexity of PCBs, identification of manufacturing defects is challenging. Many times, PCBs may have defects such as opens and shorts, wrong orientation, soldering inconsistency, misalignment of components, wrong component placement, defective non-electrical, and electrical components, missing electrical components, and so on. To avoid all these, PCB manufacturers employ the following inspection methods.

All the above-discussed techniques ensure accurate inspection of electronic assemblies, and help PCB assemblers ensure their quality before leaving the facility. If you are considering PCB assemblies for your next project, it is important that you source from trusted PCB assembly services such as Creative Hi-Tech. The company has been delivering PCB assemblies to its clients across industry sectors such as aerospace and satellite, industrial electronics products, computer and business electronics, medical, military, wireless, and telecommunications, since its inception.

• First Article Inspection:

  The quality of production always depends on the proper functioning of SMT. Hence, before the start of volume assembly and production, PCB manufacturers employ first article inspection to ensure the SMT equipment is properly set. This inspection helps them detect vacuum nozzles as well as alignment issues, which can be avoided during volume production.

• Visual Inspection:

  Visual inspection is one of the most common inspection techniques employed during PCB assembly. As the name indicates, this involves inspecting the various components through naked eye or detectors. The choice of equipment will depend on the positions to be inspected. For instance, component placement and solder paste printing is visible to naked eyes. However, solder paste deposition and copper pad can be viewed only using a Z high-degree detector. The most common type of visual inspection is carried out at reflow joints using a prism, where the ray of light reflected is analyzed with different perspectives.

• Automated Optical Inspection (AOI):

  This is the most common, yet comprehensive visual inspection method employed for identifying defects in PCBs. AOI is usually performed using multiple cameras, light sources, and programmable LED libraries. The AOI system clicks images of solder joints at different angles, and these images are compared with a perfect PCB for identifying defects such as stains, scratches, nodes, and more. These systems can also detect missing, incorrect, and skewed components, too. Many AOI systems can inspect 30–50 joints in a second, which helps minimize the time taken to identify and correct defects. Nowadays, these systems are employed during various phases of the PCB assembly. Earlier, these systems were not considered ideal for measuring the height of solder joints on the PCBs. However, with the advent of 3D AOI systems, this has become possible. In addition to this, AOI systems are ideal for inspecting complex shaped components with pitches measuring 0.5mm.

• Automated X-Ray Inspection (AXI):

  The demand for denser and compact-sized circuit boards is increasing, owing to their utilization in miniature devices. Surface Mounted Technology (SMT) has emerged as a popular option among PCB manufacturers who want to design dense and complex PCBs. Although SMT has helped reduce the PCB package sizes, it has also induced several complexities which are not visible naked eyes. For instance, there may be 15,000 solder connections in a small chip package created using SMT, and it is not easy to verify them with naked eyes. This is where AXI is employed. It is capable of penetrating the solder joints, and identifies missing balls, solder disposition, misalignment, and many more. The X-ray penetrates into solid things, and captures their images. These images are then compared by experts to identify defects in PCBs. In short, AXI is capable of penetrating through chip packages that have connections underneath, densely packed boards as well as solder joints.

All the above-discussed techniques ensure accurate inspection of electronic assemblies, and help PCB assemblers ensure their quality before leaving the facility. If you are considering PCB assemblies for your next project, it is important that you source from trusted PCB assembly services such as Creative Hi-Tech. The company has been delivering PCB assemblies to its clients across industry sectors such as aerospace and satellite, industrial electronics products, computer and business electronics, medical, military, wireless, and telecommunications, since its inception.

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