微米級旋轉列印立體微影系統之開發

Abstract

立體微影(Stereolithography, SLA)是加法製造(Additive manufacturing, AM)的一種，利用特定波長的光固化聚合液態之光固化樹脂以成形物體。相關技術不斷朝向提高列印的精度與速度發展。然而，其列印速度、面積與精度在技術上難以兼得，速度提升與面積加大往往需要犧牲部分精度，反之亦然。本論文致力於開發改善一套立體微影系統，使用伺服主軸馬達與步進滑台作列印光碟的極座標定位，這樣的配置擁有連續轉動高速列印的優勢，而且具有高速列印大面積微結構之潛力。系統使用低成本、體積小且聚焦光點小之藍光光碟讀取頭(Optical pickup unit, OPU)作為光源，以達到微米尺度之製作精度。此外，為使OPU雷射在列印時能穩定聚焦於基底光碟表面，系統採用雙讀取頭分別配置於基底光碟之上方與下方。上方OPU作為光固化之光源使用。下方OPU則利用對焦誤差訊號(Focus error signal, FES)做為回饋參考訊號，並同步控制上下方OPU內部之音圈馬達(Voice coil motor, VCM)進行即時對焦調整。欲列印圖形經過程式以極座標轉換對應旋轉列印之位置，配合解碼主軸馬達編碼器訊號控制藍光開關列印。系統可以穩定列印之最高線速度達80 mm/s，列印連續線之線寬約22 μm，徑向位移最小達1.2 μm，角度方向定位解析度最小達到1.25 μm，得以清楚列印小至長寬16 × 18 μm、線寬3 μm之數字圖形。在達到微米級列印精度的同時，亦可以列印公分級大小之圖形。

Stereolithography is a type of additive manufacturing that uses a specific wavelength of light to cure and polymerize photocurable resin to form objects. Related technologies continue to improve the accuracy and speed of printing. However, it is technically difficult to have high printing speed, large printing area, and high accuracy at the same time. The increase in speed and area often sacrifice accuracy, and vice versa. This research is devoted to developing and improving a stereolithography system, using servo spindle motor and stepper linear actuator as the polar coordinate positioning of printed disc. Such configuration has the advantage of continuous rotation and high-speed printing, and has the potential to print large-area microstructures at high speed. The system uses Blu-ray optical pickup unit which is lost-cost, compact and has small focus spot as the light source to achieve micro-scale fabrication accuracy. In addition, in order to make the OPU laser focus stably on the surface of the base disc during printing, the system adopts dual pickup heads, which are respectively arranged above and below the base disc. The upper OPU is used as a light source for light curing. The lower OPU uses the focus error signal as a feedback reference signal, and synchronously controls the voice coil motor inside the upper and lower OPUs to make instant focus adjustments. The printing pattern is converted to polar coordinates corresponding to the position of spin printing. And control the Blu-ray switch with the decoded spindle motor encoder signal to print. The system can stably print with a maximum linear speed of 80 mm/s, a line width of about 22 μm for continuous printing, a minimum radial displacement of 1.2 μm, and a minimum angular positioning resolution of 1.25 μm. Patterns as small as 16 × 18 μm in length and width can be clearly printed with 3 μm line width. While achieving micron-level printing accuracy, it can also print patterns in the size of centimeters.