BGA solder ball inspection method

Usually, when we check the soldering status of BGA solder balls, we can usually check them with X-ray inspection machine If we want to check if the solder balls lack solder or cracks/weld bridge/short defects.

BGA solder ball inspection

Basically ,There are three ways to check the solderability of BGA, using X-rays, Red Dye Penetration Test and slicing. Before you want to analyze the welding status of the BGA, it is recommended that you use X-ray machine to see if you can see any problems. The other two methods continue to be used only when X-Ray is unable to determine the problem.

There is also a way to use optical instruments to inspect BGA solder balls, such as microscopes or fiber optic miniature cameras, but since the BGA spacing is getting smaller, it usually only checks the two rows of BGAs. Tin ball, another is a bit difficult, so we won’t introduce it here.

In fact, there is also a way to use optical instruments to check the BGA solder balls, such as the use of a microscope, or a fiber optic miniature camera, but because the BGA spacing is getting smaller and smaller, it can only check the two rows of solder balls outside the BGA. It is difficult to find out other defects, so we won’t introduce them here.

Here are three ways to check the BGA solder status:

X-Ray machine Check BGA solder state:

The general X-Ray 2.5D inspection machine can see the shape of the whole solder ball. From the x ray Imaging, the bridging and cracking problems can be seen. If there are too many or too large bubbles in the solder ball, there is a high possibility that the crack will occur. In addition, if the outer diameter of the solder ball is larger or smaller than other adjacent solder balls, it may cause void welding. If this check can detect a bad BGA problem, there is no need to use other destructive tests.

Red Dye Penetration Test:

This is destructive test, usually using a bad board that cannot be solved by all non-destructive tests. Because the destructive experiment is done, the PCB board and BGA will be scrapped, and even the original evidence may be destroyed. In general, the red test can see the soldering phenomenon of all the solder balls under a whole BGA.

Its theory is to use the more obvious red syrup to fill the bottom of the whole BGA, using the red syrup to penetrate into the characteristics of all the small cracks, and then check the distribution of the red syrup and the solder balls after the BGA is removed from the board. When judging, it is necessary to check the solder pad on the circuit board and the amount of red syrup remaining on the solder ball on the BGA,The recording method usually uses a drawing on the table, which will correspond to the position of the BGA solder ball, Then record the residual phenomenon of red syrup on each solder ball.

Microsection Check BGA solder status:

This method is destructive experiment, and it is more labor-intensive than the red test. It requires a more accurate pre-operation analysis. Use an electrical test to check if the solder ball has a problem. Then take a knife and you think there is a problem. The place is cut across the board, and the cut structure can be used to check the cross-section structure of the solder ball in detail. Even the lines and nodes on the board can be seen. Sometimes the BGA problem is not from the BGA solder ball soldering. It is a line problem from the board, and the use of slices can also be analyzed along with the board’s problems.

If the mechanical action of the slice 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 is necessary to be very careful, slowly grind the section to be inspected, and grind it out. The place has to remove dust and special development, otherwise some phenomena are not easy to be examined by microscopy. Because it is time-consuming and labor-intensive, it is usually sent to the laboratory outside the factory, Let the technicians make the microsection Report.

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