微機電系統化的模仁及其配套熱壓成形技術的開發

Abstract

熱壓成形技術可用以製造高精度、高品質、高深寬比之塑膠微結構。在熱壓成形的冷卻脫模步驟中，由於使用之高分子材料與模仁的熱膨脹係數不同，造成收縮夾模，加上仍然持續於保壓狀態下，在微結構根部會產生應力集中，容易發生脫模斷裂的缺陷。為使塑膠微結構在微成形加工能達到良好賦形性，本研究以微機電系統技術製作一矽基的可自加熱模仁，期望在冷卻脫模過程中，模仁仍能保持適當高溫，以消除成形微結構的應力。此模仁以P型(110)之矽晶片為基材，在其中製造出有阻值、能導電的區域，同時引入熱電阻的觀念，對導電區域通入電壓或電流，讓導電區域能夠導通並產生熱量，作為模仁脫模時維持溫度的來源。再者，並探討導電區域阻值與溫度及阻值與壓力的關係，期能發展出嵌入式壓力、溫度感測器，以便實際感測模仁近旁的局部溫度、壓力，達到即時監控溫度、壓力的目的，如此有助我們提高脫模時成形品的品質。 此微機電系統化模仁之設計亦可易於應用在大面積的密集且深寬比大之微結構製品，對於解決大面積熱壓時收縮不均勻的問題，有非常良好的效果。

Hot embossing technology is used to manufacture high precision, high quality, and high aspect ratio of polymer micro structures. Due to the differences of thermal expansion coefficient between polymer and mold insert, shrinking of polymer material in the cooling step may lead the mold cavities to press micro structures from both sides. In addition, because of it under the state of pressing, the stress concentration will occur in the root of micro structures, and the defect of rupturing will happen during the demolding step. In order to eliminate stress concentration and attain good shape-transformation, this research attempts to develop a MEMS systematic mold insert, which keeps the mold insert at a satisfactory high temperature while the mold is cooling. P type (110) silicon wafer, as a substrate, is used to produce conducted regions with desired resistance. Moreover, these conducted regions with suitable resistance are utilized as the heaters, which are charged an electric current to heat the mold insert in the cooling stage. Furthermore, effects of temperature and pressure on the resistance are investigated respectively to develop the temperature-sensing and pressure-sensing function on the mold insert. The design of this MEMS systematic mold insert can also be easily applied to manufacturing a large area of intensive and high aspect ratio micro structures. It shows effective results in solving the problem of shrinkage on a large area when hot embossing is used.