Electronics manufacturing has consistently become more sophisticated over the past several decades, with electronics in industrial, communication, military and aerospace industries advancing in ways that make inspection significantly more difficult. Some of the most significant trends that negatively affect inspection include:
- Component placement: Equipment is becoming smaller and more layered to save space and maximize functionality. As a result, many solder joints and components are being moved to inner layers within electronics, either placed between PCB layers or hidden within the final product itself.
- Component size: More circuit board components are trending toward miniaturization. With the need to create more dense boards, PCB components are expected to continue toward this trend.
- SMT: Surface mount technology makes leads and packages smaller, which has resulted in PCBs having higher density with more components hidden between layers.
The increasing density, decreasing size and more complex placement of PCBs and their components have made it nearly impossible for traditional inspection methods to find faults thoroughly. Optical, ultrasonic and thermal imaging methods are relatively ineffective due to the density of modern PCBs.
However, x-ray inspection can collect detailed images where these other methods cannot. X-ray has the ability to penetrate layers of PCB to inspect inner layers and packaging, making it more useful for inspecting the solder joints of complex PCB assemblies. For this reason, PCB inspection with x-ray technology is becoming increasingly popular.
What are the working the principles of X-ray inspection?
To understand what x-ray PCB inspection is, you first need to know how x-ray inspection works. All x-ray inspection devices are made up of three basic features:
- X-ray tube: This tube has the ability to generate x-ray photons.
- Platform: The operation platform moves the sample in different directions, allowing it to be inspected from various angles and magnitudes.
- Detector: The detector on the other side of the sample catches and collects x-ray photons, converting them into an image.
X-ray imaging works using x-ray photons, which are passed through a material and collected on the other side. The x-ray photons pass through materials differently based on their physical properties, including atomic weight, density and thickness.
Generally, heavier elements absorb more x-ray photons, making them easier to image, while lighter elements are more transparent. Because different materials behave uniquely, differing amounts of photons are collected on the other side of the object, resulting in an image. Components in a PCB typically consist of heavier elements, making them easy to see on an x-ray image.