PCB Technical - PCBA inspection method

Nowadays, due to the increasing complexity of printed circuit boards, the identification of manufacturing defects has become full of challenges. Many times, PCB may have defects such as open circuit and short circuit, wrong direction, inconsistent soldering, misalignment of components, wrong component placement, defective non-electrical components, missing electrical components, etc. To avoid all these situations, turnkey PCB board assembly manufacturers use the following inspection methods.

All the techniques discussed above can ensure accurate inspection of electronic PCB components and help ensure the quality of PCB components before they leave the factory. If you are considering PCB assembly for your next project, be sure to obtain resources from trusted PCB assembly services.

First Article Inspection

Production quality always depends on the normal operation of SMT. Therefore, before starting mass assembly and production, PCB manufacturers must conduct a first article inspection to ensure that SMT equipment is installed correctly. This inspection helps them detect vacuum nozzles and alignment problems, which can be avoided in mass production.

Vision check

Visual inspection or naked eye inspection is one of the most commonly used inspection techniques in the PCB assembly process. As the name suggests, this involves checking various components through the eyes or detectors. The choice of equipment will depend on the location to be inspected. For example, the placement of components and the printing of solder paste are visible to the naked eye. However, the solder paste deposits and copper pads can only be seen with the Z height detector. The most common type of visual inspection is performed at the reflow solder joint of a prism, where the reflected light is analyzed from different angles.

Automated optical inspection

AOI is the most common but comprehensive visual inspection method used to identify defects. AOI is usually performed using multiple cameras, light sources and programmed LED libraries. The AOI system can also click images of solder joints and inclined parts at different angles. Many AOI systems can inspect 30 to 50 joints in one second, which helps minimize the time required to identify and correct defects. Today, these systems have been used in all stages of PCB assembly. Previously, AOI systems were not considered ideal for measuring the height of solder joints on PCBs. However, with the advent of 3D AOI systems, this has become possible. In addition, the AOI system is very suitable for inspecting complex-shaped parts with a pitch of 0.5mm.

X-ray inspection

Due to their use in miniature devices, the demand for denser and compact size circuit board assemblies is growing. Surface mount technology (SMT) has become a popular choice among PCB manufacturers who wish to use BGA package components to design dense and complex PCBs. Although SMT helps reduce the size of the PCB package, it also causes some complexity that is invisible to the naked eye. For example, there may be 15,000 solder connections in a small chip package (CSP) created using SMT, and it is not easy to verify them with the naked eye. This is where X-rays are used. It has the ability to penetrate solder joints and can identify missing solder balls, solder positions, misalignments, etc. X-rays penetrate the chip package, which has connections between the tightly connected circuit board and solder joints underneath.