The Use of X-Rays in Circuit Board Assembly

Lying beyond ultraviolet light on the electromagnetic spectrum, X-rays, named for their enigmatic nature to their discoverers, have found a multitude of scientific and technological applications. The doctor’s office and airport security, of course, are our most common brushes with X-ray radiation—and fortunately, they’re brief ones. However, people also use X-rays in the assembly of printed circuit boards—namely, the post-assembly quality-control processes that assure all technological components are free of defects and in the proper position. Let’s learn more about the use of X-rays in circuit board assembly.

How It Works

An X-ray inspection device for PCB assembly consists of a tube that generates X-rays, a moving platform on which the PCB rests, and a detector for rendering images. X-ray photons pass through some but not all material on their way from the generator to the detector. Generally, the heavier an element’s atomic weight, the more X-rays it absorbs, thus appearing translucent or opaque in images. This is advantageous in examining PCBs, which contain a variety of materials and therefore offer high-contrast images.

What It Finds

This high contrast between components makes defects readily apparent. Imperfections within a board’s soldering, from inadvertent connections to unwanted gas bubbles within the solder, are invisible to the naked eye and even to magnification. However, they appear within X-ray images thanks to the variations in radiation absorption. While there are many different varieties of PCB inspection, from manual inspection to laser-based and ultrasonic approaches, only X-ray inspection can discover defects that lie deep within components.

Why It Matters

Immaculate quality control is integral to the operations of PCB manufacturers, and the use of X-rays in circuit board assembly is a means to that end. If there’s one constant in the field of technology, it’s advancement—developments in circuitry seem to happen daily. Chief among these developments is the further layering of PCBs. Circuit boards become smaller yet denser, with key components lurking below surface level upon interior layers of boards. Manufacturers can’t afford to send out such intricate circuit boards that are destined for failure—failure that wouldn’t be evident to the naked eye. X-ray inspection of PCBs preemptively finds the critical errors lurking deep within today’s most advanced printed circuit boards, keeping quality control high as the industry presses ever forward.

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Written by Logan Voss

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