PCBA Tech - What is the effect of X-rays on PCBA circuit boards?

X-ray is an electromagnetic wave with extremely short wavelength and high energy, which has very strong penetrating ability.

When an X-ray irradiates a sample, its transmission intensity is not only related to the energy of the X-ray, but also related to the material density and thickness of the sample material. The smaller the material density and the thinner the thickness, the easier X-rays can penetrate. The principle of X-ray detection is to use X-rays to irradiate the sample, and then use the image receiving and conversion device to image the X-ray transmission intensity with the contrast between the brightness and darkness of the grayscale. PCBA contains a wide range of materials with different thicknesses. According to the density of the material, they are generally divided into four categories:

(1) Solder joints composed of tin, lead or tin-lead alloy with higher material density;

(2) Metal and ceramic packaging shells, gold wires and chip bonding materials;

(3) Easily permeable materials such as molding compound and silicon;

(4) Defects such as voids, cracks and PCB through holes. When X-rays pass through the first and second types of materials, the X-rays pass less and the resulting image has a higher gray value; when X-rays pass through the third type, the resulting image has a lower gray value; In the fourth category, X-rays are completely transmitted through and eventually become bright images.

x-ray

The 2DX ray detector can be tilted at an angle of ±70°. First, adjust the voltage, power and contrast of the X-ray detector through reasonable settings to adjust the PCBA imaging quality to the best state. The whole detection process is mainly divided into four steps, which is also called three plus one method in this article.

(1) Conduct a global inspection of PCBA, mainly including PCB and components;

(2) Enlarge the image for partial inspection to find defects or suspected defects;

(3) Identify, analyze and confirm suspected defects through re-magnification and tilt imaging;

(4) Carry out oblique imaging for all BGA packaged devices, and preliminarily check whether there are any defects in solder joints.

In the current PCBA, the problem of invisible welding defect detection is difficult. Based on the 2DX ray detector, the detection method and detection process are proposed. The X-ray inspection scheme was verified through experiments, and the results showed that the X-ray inspection scheme given was reasonable and feasible. According to this inspection scheme, common welding defects in PCBA can be identified, and it can also guide PCB design and welding process improvement. The X-ray inspection program has the following advantages when inspecting PCBA welding quality: clear imaging, easy to identify defects; covering common defects of PCBA, high work quality; standardized operating procedures, and high inspection efficiency.

Strict attention to product quality is not only a manifestation of high-quality production services provided by enterprises, but also a favorable guarantee for industrial safety in production. Strengthening the quality inspection of castings and ensuring production quality is the key to ensuring the sustainable development of my country's manufacturing industry.