BGA錫球定位與幾何形狀之視覺檢測方法研究

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

劉嘉唐(Jia-Tang Liu)

指導教授 ： 陳永樹

元智大學/工程學院/機械工程學系/碩士(2004年)

摘要

近年來積體電路（IC）晶片隨著運算處理和功能之增強，使得IC的接腳數相對也隨著增加，因而發展出球格陣列（BGA）封裝以錫球取代傳統引腳（Lead），為廣泛應用之高密度表面黏著封裝技術。如何快速檢測這些錫球之二維與三維幾何形狀，深深影響這些電子產品其可靠度，更是工業界所引頸企盼的技術。本研究將利用機器視覺之方法，發展出這些錫球幾何形狀之檢測發法。
研究中首先針對二維之幾何形狀如錫球直徑與真圓度部分作探究。使用CCD照相機擷取BGA錫球影像後，接著使用影像處理程序使錫球影像清晰正確，再分別使用最小平方圓邊緣法和八鄰邊鏈碼面積法兩種判別法則，取得錫球相關形狀尺寸數據。而三維幾何形狀部分如錫球高度等，則先以影像灰階值法轉換求出錫球最高點，再以移動CCD拍攝高度的聚焦法方式，利用Sobel影像處理判斷是否聚焦，分別對錫球最高點與最低點聚焦擷取影像，進而求得錫球高度數據。
其驗證方式以兩種BGA試片作檢測，二維部分分別以手動量測方式加上光學檢測設備量測其錫球形狀尺寸數據;三維部分則利用雷射位移計配合精密XY平移台找出其高度與整體共平面度數據，加上統計品管的觀念，再和先前實驗結果比對並討論其誤差之產生因素，進而繪製出統計管制圖。

關鍵字

影像處理 ； 視覺 ； 聚焦 ； 雷射位移量測系統 ； BGA

並列摘要

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.

並列關鍵字

image process ； vision ； focus ； laser displacement measurement ； BGA

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