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AOI – Why is it favored during the PCB Manufacturing?

 Jan 22, 2018

PCB Inspection Made Easy

Most PCB manufacturers are driven by challenges like shortening time-to-market capabilities, reducing profit margins, and increasing customer expectations regarding the product quality. They know a poor quality product may reduce their chances of success in the marketplace. Thus, along with advanced manufacturing techniques, these manufacturers are also adopting various PCB inspection and testing services. Automatic Optical Inspection (AOI) is one such technique which is used to test defects in the printed circuit boards. This post discusses the need and importance of AOI in PCB manufacturing.

A Brief Introduction to Automatic Optical Inspection

This technique is also known as automated optical inspection. As the name suggests, it is an automated inspection of the printed circuit boards using high definition cameras. The camera conducts thorough scan of the printed circuit board for testing quality defects and catastrophic failure. This is non-contact method of inspection, thus it is employed during the PCB manufacturing process. AOI is employed at various stages of PCB manufacturing to avoid manufacturing defects. For example, it is employed for bare board inspection, pre-reflow, solder paste inspection (SPI), and post-reflow stages.

Analyzing the Need for Automated Optical Inspection

Despite various advanced technologies, modern circuit boards have complicated designs. The complications have increased due to the introduction of surface mount technology, as well as the growing demand for compact sized circuit boards. Although small sized, the circuit boards may have hundreds of soldered joints, and various 0201 and 0402 components, which contribute to the complexity. Thus, when it comes to the printed circuit boards, manual inspection isn’t possible.

Currently, there is a huge demand for a reliable inspection method, which increases significance of AOI.

Understanding the Basics of Automatic Optical Inspection

Automatic Optical Inspection uses various advanced visual methods to scan the manufacturing defects on the PCBs. These tests help detect a variety of surface defects like open circuits, stains, and scratches, as well as missing components, incorrect component placements, etc. The system used for inspection compares the images with the ideal diagrams to detect the faults. This type of comparison helps highlight various defects.

The following are some important techniques used to analyze the board for various defects:

  • Pattern Matching: The AOI system uses this technique to store the information on both perfect and faulty assemblies. Also, the system matches the obtained image to the information.
  • Template Matching: The automated optical inspection system compares the scanned images, with the golden board.
  • Statistical Pattern Matching: This method is similar to the above-mentioned methods, with the only difference that it uses statistical data to address the problems. It analyzes the perfection of the image by matching the obtained images with hundreds of stored data. It is designed to accommodate minor imperfections.

Accelerated Assemblies is one reputed and trusted name in the electronics industry. The company is known to provide comprehensive range of PCB testing and inspection services.

Is this all about AOI? No. There is more about it. In the next post, we will discuss, various other aspects of AOI.

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