Essential PCB Inspection Techniques for Quality Assurance

Feb 12,2019

Over the years, the demand for PCB-driven devices has increased. These devices are being used in every industry right from military and defense to the toy industry. This suggests an increasing dependability on PCBs, isn’t it? A proper utilization of these PCBs is only possible if they meet certain quality standards. Thus, PCB manufacturers are adopting several PCB inspection techniques, which helps them assure the quality at various stages of manufacturing. Also, it helps them reduce the losses incurred due to project rejects, and loss of goodwill. Do you want to know what are the different PCB inspection techniques adopted by the PCB manufacturers? Read the post to find the answers.

A Brief Discussion on Various Types of PCB Inspection Techniques Adopted by PCB Board Companies

The demand for compact-sized electronics is on the rise. This is challenging the PCB manufacturers to develop compact sized PCBs. These PCBs have a large number of solder connections, which aren’t visible to naked eye. With such a high-density of connections, there are all chances of misalignments, wrong orientations, defective components, etc. This is where these techniques come to rescue:

Advanced 3D AOI equipment allows manufacturers to inspect the appropriate height of the component.

• Manual Inspection:This is the basic inspection method adopted by all small and big PCB manufacturers. It involves visual inspection of boards to detect major problems of the PCBs. Although this technique is considered incomplete in some contexts, still it is practiced by manufacturers.

• Automated Optical Inspection:This technique is most commonly referred by its abbreviation AOI. The printed circuit boards are scanned using advanced video cameras. The board is closely examined at various angles, and images are clicked by the cameras. These images are mapped with the design specifications or the golden board to identify various defects. This technique is more effective for identifying various types of dimensional defects. These may include skewed components, missing or incorrectly placed components, etc.

• X-ray Inspection:There has been a huge surge in the demand for Surface Mount Technology (SMT) devices. Why? Because these devices are compact, and are densely populated. Do you know there can be printed circuit boards, which may have more than 25,000 solder connections! The advances in SMT have also increased demand for microchip packages such as Quad Flat Package (QFP), Ultra-fine Ball Grid Array (uBGA), and small chip packages (pitch of 0.2mm), where the solder connections are invisible to eyes. These chip packages are nowadays inspected using X-ray machines because they possess several complex soldering joints. The X-rays produce digital graphics of the soldered joints in a gray scale of 256. The gray graphics helps analyze characteristics, including the thickness of the solder joint, distribution of the joints, and their integrity throughout the circuit board. In short, the X-ray inspection helps to identify various soldering defects, such as insufficient soldering, cracks, misalignment, etc.

• Automated Laser Triangle (ALT) Measurement: As the name suggests, this technology utilizes the laser technology to measure the height of solder paste deposition or solder joints. The ALT inspection is mainly employed for controlling the procedure of solder paste printing. For instance, it helps determine the viscosity of soldering, cleanliness of soldering, leakage board alignment, the pressure of applying solder paste, squeezing velocity and flow, etc.

In addition to the above-mentioned PCB inspection techniques, there are various techniques, which are usually employed during the manufacturing phases. However, in some production phases, the inspection is conducted after the pick and place stage. Many advanced pick and place machines used today are equipped with optical PCB inspection systems. These systems enable to minimize soldering irregularities, and other manufacturing defects.   

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