How to use X-ray to detect faulty soldering of circuit board?

Date：2021-08-12 17:08:00Views：2091

In the production of electronic enterprises, welding is one of the important links in the manufacture of electronic products. If there is no corresponding process quality assurance, there will be some circuit board problems, and some defects can not be judged by the naked eye. The common defects of PCB board are false soldering, bonding and copper foil falling off. In mass production, from screening and testing of components to assembly and welding of circuit boards are completed by automatic machinery, which is conducive to ensuring the consistency of process conditions and assembly and welding operations and improving product quality.

Causes of false soldering

1. Poor solderability of circuit board holes will lead to false soldering, which will affect the parameters of components in the circuit, resulting in unstable conductivity of multilayer board components and inner wires, resulting in failure of the whole circuit function.

2. Circuit boards and parts will warp during welding, and defects such as false welding and short circuit will occur due to stress and deformation. Warpage is usually caused by a temperature imbalance between the upper and lower parts of the circuit board.

3. In addition, the design of circuit board will also affect the welding quality of PCB.

Cause of adhesion: the temperature of the soldering iron should not be too high. Too high will burn the iron head of the soldering iron and can't eat tin, and it is easy to make the copper foil fall off. The reason why the copper foil falls off is that the soldering iron can't eat too much tin at one time. Too much tin will lead to the adhesion between the two solder joints.

Principle of X-ray

X-ray testing is a non-destructive testing method to find defects by using the characteristics of X-ray penetration and attenuation in materials. The wavelength of X-ray is very short, generally 0.001 ~ 0.1nm. X-rays propagate in a straight line at the speed of light, are not affected by electric and magnetic fields, can penetrate substances, attenuate in the process of penetration, and can make the film sensitive. Many minor defects can be found by power on inspection, such as circuit bridging that cannot be observed by visual inspection, but it is not easy to detect the hidden danger of internal false welding. Therefore, the enterprise will choose X-ray to check the welding inside the circuit board. X-ray can pass through the package and scan the image inside the circuit board, so as to judge the integrity rate of the product and detect the quality of the circuit board.

Conclusion: X-ray can effectively detect defects such as false soldering, adhesion and copper foil falling off of PCB. Test equipment on the market needs to be able to fully detect these defects. X-ray testing is a good choice. The reason is that X-ray has the function of penetration. Its wave length and energy are large. When it shines on the material, only part of it is absorbed by the material, and most of it passes through the atomic gap, showing a strong penetration ability. The ability of X-ray to penetrate matter is related to the energy of X-ray photons. The shorter the wavelength of X-ray, the greater the energy of photons and the stronger the penetration. The penetration of X-ray is also related to the density of substances. Substances with different densities can be distinguished by using the property of differential absorption.