A study in Using Machine Vision to Inspect the 2D/3D Geometries of the BGA Solder Balls

• Main Authors: Jia-Tang Liu, 劉嘉唐
• Other Authors: Yeong-Shu Chen
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/25485433106178816434

碩士 === 元智大學 === 機械工程學系 === 93 === With the function of today’s IC becomes more complicate than ever before, the I/O counts also increased dramatically. With the increase of the surface packaging density, the development of the Ball Grid Array (BGA) packaging with solder balls as signal connections has replaced many of the traditional pin lead packaging. However, the flatness of the area solder balls’ surface and the roundness of the solder ball itself influence the electronic device reliability intensively. A quick and correct checking method of these properties is always the expectation of many industrial applications. The study will use a series the machine vision techniques to identify these characteristics of solder balls. The two-dimensional image of the BGA solder balls will be taken first with a high resolution CCD camera and then using the image process techniques to make the image clear and correct. The solder ball image are then further calculated with the minimum square rounding edge and chaining area methods to check out its two dimensional geometry such as diameter and roundness. The gray levels of the solder balls are the key factor used in deciding the height of the solder balls in the three-dimensional measurement. The image will be obtained by adjusting the CCD camera to get the image focused first, and then with the Sobel image process algorithm to improve the image focus further. Once it is focused on the top and bottom of the solder ball respectively, the corresponding solder ball height is then obtained. The verification of the results is conducted by with two different BGA components. The two-dimensional geometry is checked both with manual and optical measurement methods. The three-dimensional measurement is checked with a laser displacement measuring system together with an accurate XY table to find out the data of solder ball height. Finally, the errors are discussed with the SPC plot of all experimental data.