| BGA packaging is a high integration density modern way of integrated circuit device packaging and the development of BGA packaging device directly promote the development of the chip welding technology. However, because solder joints are not visible inside the chip, solder joints are getting smaller and the welding manner is becoming more and more precision, all this caused the weld defects increase and solder joint detection technology has also become a difficult problem in industrial production.However, In domestic enterprises, we mainly adopt the manual visual inspection method to test the BGA defect of solder joint, which greatly increased the test reliability. So how to improve the efficiency and accuracy of BGA solder joint defect detection, how to increase test efficiency and how to improve the quality of electronic products has a very important research value and practical significance.This paper has completed the following works: analyzed the imaging characteristics of BGA solder joint and explained why the result is bad when use common way to image noise reduction for the BGA solder joint, and studied the applicability and effectiveness of PM model in BGA solder joint image noise reduction.A new segmentation algorithm by using the mean of connected area as the threshold is provided. Mainly studied the commonly used threshold method and analyzed the reason of it’s inaccuracy, then a new algorithm is proposed, which uses the mean of connected area as the threshold with mathematical morphology smooth edge of solder joints. The new method not only filters out line bridge effectively, but also uses threshold combining with the experience to identify and filter bridge welding defects and then statistics the connected area. Histogram equalization is used for the BGA solder joint image and analyses why the increase is not obvious. Using histogram equalization to enhancement each solder joint area alone is proposed, and it can make a difference brightness between the solder joint areas and the bubble area. A new algorithm by gradient directional filter is improved.Based on the bubble areas have a low contrast,different size and random location, so a new gradient directional filter is designed to filter the outside bubble area successfully. By generating bubbles area’s blob diagram to extract bubbles. Judging the effectiveness of all the bubbles,then determining the effective air bubbles and statistics of the area statistics the area. Calculating the ratio of the effective bubbles in solder joints, then refer to the IPC standards and the actual production requirement to defect recognition the air bubble defect in BGA solder joint. |
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