With the rapid development of electronic technology, SMT technology has become more and more popular, and the size of chips is getting smaller and smaller, and more and more pins of chips, especially the BGA(Ball Grid Array) chips in recent years, because the pins of BGA chips are not distributed around according to the conventional design, but on the bottom of the chip.

There is no doubt that the quality of solder joints cannot be judged at all through the traditional artificial visual inspection, and must pass ICT or even functional testing. However, in general, if there are batch errors, they cannot be detected and adjusted in time. In addition, artificial visual inspection is the most inaccurate and repeatable technology, so x-Ray inspection technology has been increasingly widely used in SMT reflow soldering quality inspection. It can not only carry out qualitative and quantitative analysis of solder joints, but also detect and adjust faults in time.

How the X-Ray machine works:

When the board enters the machine along a guide rail, an X-Ray tube above the board transmits X-rays through the board and is picked up by a detector (usually a camera) located below. Because the solder joint contains lead, which absorbs a lot of X-rays, it is better than X-rays passing through other materials such as fiberglass, copper, and silicon. The X-ray rays shone on the solder joint are heavily absorbed, and the black spot produces a good image, making the analysis of the solder joint fairly straightforward (see Figure 1). Therefore, a simple image analysis algorithm can automatically and reliably check the defects of solder joints.