Several inspection methods of common defects in BGA welding

Date：2023-03-10 15:46:02Views：520

When producing electronic products, we need to pay attention not only to the production process, but also to the product defects, especially the defect detection, which can mainly detect the defects on the product surface, and can use advanced detection technology. Generally, when we check the soldering quality of BGA solder ball, if it is a defect in bridging/short circuit, it can be detected by using X-Ray equipment; However, it is more complicated to check whether the solder ball has empty soldering or cracks.

Basically, there are three ways to check the solderability of BGA, including X-Ray, dye penetration test and sectioning. In any case, before you want to analyze the weldability of BGA, it is recommended that you use X-Ray to check first to see if there is any problem, because this is a non-destructive inspection after all. Only when X-Ray can not judge the problem can you continue to use the latter two destructive methods.

1、 Check BGA weldability with X-Ray

The general X-ray inspection machine can only see two-dimensional (2D) images, but it is difficult to see whether there is empty soldering or solder ball cracking in two-dimensional, because the image can only see the shape of the whole solder ball, but if there are too many or too large bubbles in the solder ball, it is very likely to cause the problem of fracture. In addition, if the outer diameter of the solder ball is larger or smaller than other adjacent solder balls, it may also cause empty soldering.

In addition, there is a new X-ray inspection machine recently, which can produce three-dimensional image results similar to that of hospital CT scan, and can present three-dimensional images and check whether there are solder defects. However, due to the high cost of this machine, it is not possible for ordinary factories to purchase such equipment at all. The more feasible way is to rent this kind of X-ray machine to the outside laboratory for preliminary inspection. If this kind of inspection can find out the problem of bad BGA, there is no need to go to the later destructive test.

2、 Red Dye Penetration Test

This is a destructive test, which is usually used for the defective board that cannot be untied in all non-destructive tests. Because if the destructive test is carried out, this board and BGA will have to be scrapped, and even the original evidence may be destroyed. Generally speaking, the soldering phenomenon of all tin balls under a whole BGA can be seen in the red dye test.

Its theory is to fill the whole BGA with obvious red potion, and use the characteristics of red potion that can penetrate into all small cracks. Then, after the BGA is removed from the circuit board, check the distribution of red potion and the results of tin balls. When judging, it is necessary to check how much red potion is left on the solder pad on the circuit board and the tin balls left on the BGA at the same time. The recording method is usually a drawing with a table, These tables will correspond to the position of BGA solder balls, and then record the residual phenomenon of red potion on each solder ball.

3、 Inspection of BGA solderability by circuit board section

This method is also a destructive experiment, and it is more labor-intensive than the dye red test. It usually requires more accurate pre-job analysis. Use the electrical test to check whether there is a problem with the tin ball, and then do the sectioning. You can temporarily imagine that the sectioning is to take a knife to cut from the place where you think there is a problem, and then you can check the section structure of the tin ball in detail, Even the circuit and nodes on the circuit board can be seen. Sometimes the problem of BGA is not from the solder ball soldering of BGA, but from the circuit board. The chip can also be used to analyze the problem of the circuit board together.

However, if the mechanical action of slicing is too large or too fast, it is easy to destroy the original BGA and the circuit connection structure on the circuit board, so it must be very careful to grind out the section you want to check slowly, and the grinding out place must also remove dust and special development, otherwise some phenomena are not easy to be detected by the microscope, because it is time-consuming and time-consuming, Therefore, it is usually sent to the laboratory outside the factory for slicing.

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