Automated X-ray Inspection in the Manufacturing of Printed Circuit Board Assemblies

Printed circuit boards (PCBs) are an integral part of the modern electronic devices we use every day. From smartphones to home appliances, PCBs enable the complex circuitry that makes these devices function. As such, the quality of PCBs is of utmost importance in the electronic assembly manufacturing process.

One of the critical stages in ensuring high-quality PCBs is inspection. Traditionally, visual inspection was the primary means of detecting defects in PCBs. However, as electronic devices become increasingly complex and miniaturized, visual inspection alone is no longer sufficient. That’s where Automated X-ray Inspection (AXI) technology comes in.

AXI technology provides a non-destructive and reliable means of detecting defects in PCBs. This article provides an introduction to AXI and its role in the manufacturing of printed circuit board assemblies.

PCB Basics

Before delving into AXI technology, it’s essential to understand what a PCB is and its role in electronic devices. Simply put, a PCB is a board that connects electronic components together. It’s made of a non-conductive substrate material, such as FR4, with conductive traces etched onto the surface. The conductive traces connect the components together and form a circuit that enables the device to function.

There are several types of PCBs, including basic circuit boards, custom PCBs, and flexible PCBs. Additionally, heavy copper PCBs and LED light PCBs are used in specialized applications.

Electronic Assembly Manufacturing

PCB assembly is a critical stage in electronic assembly manufacturing. The process involves mounting electronic components onto a PCB to form a functioning circuit. There are two primary types of PCB assembly: Through-Hole Technology (THT) and Surface Mount Technology (SMT).

THT involves mounting components onto a PCB by inserting their leads through holes in the board and soldering them on the opposite side. SMT, on the other hand, involves mounting components directly onto the surface of the board using solder paste.

SMT technology has become the preferred method of PCB assembly due to its high-density packaging, reduced board size, and low cost. SMD (surface mount devices) components and soldering paste are used in SMT assembly. However, the miniaturization of components in SMT assembly makes detecting defects using visual inspection alone difficult.

What is Automated X-ray Inspection?

Automated X-ray Inspection (AXI) technology provides a non-destructive means of detecting defects in PCBs. AXI systems use X-rays to create a three-dimensional image of the PCB and its components. The system then compares the image to a reference image of a good PCB to detect any defects.

AXI technology is particularly useful in detecting defects in SMT components and soldering paste. It can detect defects such as insufficient solder paste, voids, and tombstoning, which are challenging to detect with visual inspection alone.

There are several types of AXI systems available, including real-time and off-line systems. Real-time systems provide immediate feedback during the production process, while off-line systems provide more detailed inspection after production. Major players in the AXI technology market include ViTrox Corporation, Omron, Nordson, Viscom, NIKON, Innometry, Comet Yxlon, Unicomp Technology, Zhengye Technology, Waygate Technologies (Baker Hughes), Test Research Inc. (TRI), DC Precision, Saki Corporation, ZEISS, Techvalley, SEC, Seamark ZM, Goepel Electronic, and Scienscope.

Common defects during the manufacturing of PCBAs:

  1. Solder defects: These defects can occur when the solder joints between components and the PCB are not properly formed. Possible causes include inadequate soldering temperature, incorrect soldering techniques, or contamination of the soldering surface.
  2. Missing or misaligned components: This defect occurs when components are not properly placed on the PCB or are not properly aligned with the PCB pads. Possible causes include incorrect component placement, incorrect stencil design, or problems with the pick-and-place machine.
  3. Shorts and opens: Shorts occur when two or more conductive traces on the PCB are in contact with each other, resulting in an unintended electrical connection. Opens occur when a conductive trace on the PCB is not in contact with any other conductive element, resulting in a break in the circuit. Both shorts and opens can be caused by incorrect component placement, contamination of the PCB surface, or damage to the PCB during handling.
  4. Thermal issues: Excessive heat can cause damage to components and PCBs, resulting in defects. Possible causes include incorrect component placement, incorrect soldering techniques, or problems with the reflow oven.

Benefits of Automated X-ray Inspection

Automated X-ray inspection offers many benefits to PCB manufacturers. One of the biggest advantages is the ability to inspect components and solder joints without damaging them. This is especially important for surface mount technology (SMT) components, which are becoming increasingly popular in PCB design. With automated X-ray inspection, manufacturers can quickly and accurately check for defects and ensure that components are properly placed and soldered.

Another benefit of automated X-ray inspection is the speed and efficiency it provides. Traditional inspection methods, such as manual visual inspection or manual testing, can be time-consuming and prone to human error. Automated X-ray inspection, on the other hand, can quickly scan an entire PCB and identify any potential issues. This allows for faster production times and reduces the likelihood of costly errors.

Automated X-ray inspection also allows for more accurate inspections. Because the technology is capable of detecting even the smallest defects, manufacturers can be confident that their PCBs are of the highest quality. Additionally, with the use of advanced software and machine learning algorithms, automated X-ray inspection can detect trends and patterns in defects, allowing manufacturers to identify and address potential issues before they become widespread.

Top Brands in Automated X-ray Inspection

There are several top brands in automated X-ray inspection, including ViTrox Corporation, Omron, Nordson, Viscom, NIKON, Innometry, Comet Yxlon, Unicomp Technology, Zhengye Technology, Waygate Technologies (Baker Hughes), Test Research Inc. (TRI), DC Precision, Saki Corporation, ZEISS, Techvalley, SEC, Seamark ZM, and Scienscope.

Each of these brands offers unique features and capabilities, making it important for manufacturers to do their research and choose the brand that best fits their needs. Some brands, such as Viscom and NIKON, offer high-resolution imaging capabilities, while others, such as Unicomp Technology and Test Research Inc. (TRI), specialize in automated optical inspection (AOI).

Automated X-ray inspection is an essential technology in the manufacturing of printed circuit board assemblies. By allowing for quick and accurate inspections, manufacturers can ensure that their PCBs are of the highest quality, while reducing production times and costs. With a wide range of top brands to choose from, manufacturers have many options when it comes to choosing an automated X-ray inspection system.