非接觸式精微量測中心機之開發與應用

Abstract

本研究針對精微模具，開發一部非接觸式複合量測中心機。工件特徵尺度小於200 µm的精微模具，很難以現有的三次元接觸式量測機、雷射位移計或光學顯微鏡等傳統量測技術檢驗其精度，主要是量測面氧化層與深度打光問題難以克服之故。本研究突破傳統精微量測的微力接觸概念，自行研發一部精密三軸微型量測中心機，並以微放電技術進行線上微細探針製作。再利用機器視覺對量測部位進行影像快速擷取、二值化與辨識，所得圖像特徵用於導引微細探針，快速定位於圖像的特徵部位。藉由探針深入此特徵部位，如微細孔或窄縫中，透過電容式感測與頻譜訊號轉換，進行特徵部位的非接觸式幾何精度量測，由於探針保持非接觸狀態，故無量測力與氧化膜層問題，且線上製作微細探針，能針對工件的各種幾何形狀，迅速線上提供各種適用的探針，所以探針也無定位、夾持與校正所引發的精度問題。量測中心機之量測精度先以0級塊規校驗及比對，再對IC導線架精微模具上的陣列窄縫(100 µm)，進行垂直精度的測試，所得精度值在量測系統的定位精度內，顯示本研究所開發的非接觸式精微量測技術，具有很高的量測精度與其可行性。Many side walls of micro holes and slots are not easily measured by current measuring instruments, such as: coordinate measuring machine, laser displacement meter, or high magnification toolmaker microscope. It is very difficult for overcoming the oxide layer on the workpiece and lighting in the deep hole of the workpiece. A non-contact micro measurement center combining automatic optical inspection (AOI), micro EDM with capacitance sensing is designed and developed to automatically, precisely measure the perpendicularity of micro slot-wall on the precision mould. The measurement center can on-machine makes various micro probes to rapidly provide for the needed stylus in measurement. The AOI acquires the image from the feature profile of workpiece by way of the developed machine vision and perform the image binary to determine the centric position for guiding the movement of the micro probe. Capacitance sensing, by which a signal with very low voltage and high frequency is employed, is used for precisely measuring the slot-wall. To ensure the measuring accuracy, a ‘four steps feed’ strategy of the probe is proposed. The measuring data are converted to digital data, and then transferred into frequency domain from time domain via fast Fourier transform (FFT) to regulate the feed of the probe and record the positions. Owing to non-contact measurement, the measurement will not be affected even if the oxide layer exists on the workpiece. The measuring accuracy which the probe is first calibrated via the gauge block of grade-0 can be maintained within the positional accuracy of the measurement center and the working time decreased. A geometrical accuracy of narrow slot on the IC lead frame is successfully measured which demonstrates the developed measurement center possesses very high feasibility. It is expected that the techniques of measurement center willsignificantly contribute to the precision machining industry.