以正交相移法提升斑點干涉顯微術的量測範圍

Abstract

檢測為產業界確認產品品質重要的一環，其中光學檢測因為其高精準度、非接觸等特性，因此在檢測中佔了相當重要的角色，本研究以電子斑點干涉術建構出一套成本便宜的的動態量測系統來尋求突破目前運用光學方法來進行精密檢測所遇到的困境。 由於電子斑點干涉術乃是利用物體變形時雷射斑點的變化來推求位移等物理量，故其具有全域、非接觸式和高解析度的特性，為檢驗本論文所開發系統的應用範疇與量測經度，本論文利用電子斑點干涉術來量測電子封裝業常遇到之問題。舉例而言，覆晶時因高溫錫球產生的熱負載，將造成電子元件中因不同的材質具有不同之熱膨脹係數情況下熱變形的行為。本論文提出利用時進正交的演算法來降低相移時的誤差及簡化架構與去除相移機構成本等創新點，同時還藉由本論文的開發，擴充了顯微系統下的量測範圍。研究過程中，還使用相移法，經過濾波和利用傅立葉轉換的方式求解相位偏微分方程及重建相位，進而求出變形量。影像擷取方面，在降低成本的考量下，更換高速電耦合元件攝影機(Charge Couple Device Camera，簡稱CCD攝影機)改用一般的CCD攝影機，為了保有低曝光時間的功能，因此以改變觸發訊號寬度去控制曝光時間的長短。由於CCD攝影機擷取影像的方式乃是採用非同步取向模式，因此本論文所開發系統仍可精準的紀錄下觸發時的資訊。 為因應微機電系統(MEMS)技術的快速發展，本研究實際量測微機電結構，使用的待測物為一白金與高分子層構成的微幫浦，除充分運用時進正交演算法來提昇量測範圍之功能在顯微系統下做一驗證，同時應鉦量測結果的精準度。

Metrology plays an important role in verifying the product quality within the industries. Due to merits such as high precision and non-contact of optics, optical metrology has long benn a major field within optical metrology. A newly developed low-cost high-precision ESPI (electronic spckle pattern interferometrty) was developed during the coruse of this research.. ESPI is a full-field, non-contact, and high resolution optical metrology technique for displacement measurement, which utilized the interference fringes induced by the speckle pattern induced by the specimen surfaces. In this thesis, ESPI was applied to evaluate the thermal deformation associated with electronic packaging. For example, the high-temperature solder joints used in a flip-chip will induce large local deformation due to the differenence in thermal expansion coefficients of various materials invoved. Combining ESPI with time-stepped quadrature phase shifting was found to effective in reducing the phase shifting errors and to eliminate the phase shifting device needed, all of which were verified to improve the measurement range within the microscopic system operating conditions. In addition, the newly developed setup used for out-of-plane displacement measurement incorporated direct correlation with phase shifting, a noise reduction filter for phase unwrapping, and Fourier transform based partial differential equation solver with an attempt to improve system accuracy and measurement speed. For image data acquisition part, the high speed CCD camera was replaced by using a traditional off-the-shelf CCD camera. It is worth noting that this replacement reduced the system cost without sacrificing the measurement speed as the exposure time was controlled by using the width of the triggering pulse and the image capture was synchronized by using the external trigger shutter mode. With the rapid advancement of microelectromechanical system (MEMS), time-stepped quadrature phase shifting with a ESPI system implemented in this thesis was used to measure the motion of a micro-pump that was composed of platinum and parylene. The results obtained verified the system capability and metrology accuracy.