可撓式AMOLED顯示器取下過程之應力分析

Abstract

本研究主要透過雙材料破壞力學理論，探討可撓式AMOLED顯示器於機械式取下過程之應力分析。由於雙材料界面特性，當裂紋承受負載時會同時出現開裂及剪裂的破壞模式，而應變能釋放率G受到破壞模式之影響。本研究利用Sun等人提出的位移比例法，藉由有限元素分析，計算裂紋尖端的應變能釋放率與破壞模式混合比。 可撓式面板於機械取下製程中，易產生失效，為提升製程良率，將建立有限元素模擬分析，瞭解取下過程中面板所受之應力分佈，並針對各項取下製程參數進行討論分析，找出可撓式面板所承受較低應力時之參數。首先設計三種不同結構的取下試片，藉由取下實驗量測界面破壞時的臨界取下力量，瞭解PI基板與玻璃載板間破壞韌性GC與破壞模式混合比ψ之關係。接著探討兩種不同取下方式，分別為定角度直接取下及吸盤正面取下，分析當PI基板與玻璃載板之間界面裂紋滿足破壞準則時，結構中OLED的最大主應力，藉此比較兩種取下技術之優劣。此外本研究亦探討直接取下及吸盤取下的不同製程參數，對OLED結構最大主應力之影響，結果顯示吸盤取下相較於直接取下方式，OLED會承受較小之應力，因此正面取下技術應可有效的提升取下良率。

This research aims to investigate the stress distribution of a flexible active-matrix organic light-emitting diode (AMOLED) display during the debonding process using bimaterial fracture mechanics theory and finite element analysis. Since the bimaterial interface properties will induce the open and shear failure modes when the crack subjected to load at the same time. According to the displacement ratio method and finite element model calculate the energy release rate and mode mixity of crack tip. To enhance the yielding rate of AMOLEDs, their stress distribution must be investigated by finite element analysis during the debonding process. In addition, the parameters possibly influencing the stress states of the AMOLED in the debonding process are discussed and analyzed. First, design three different structure specimens and record the critical load of peeling test. In order to understand the fracture toughness and mode mixity relationship. Second, two debonding techniques are discussed respectively. In the FEM simulation, when the total energy release rate at the crack tip exceed the fracture toughness to analyze the maximum principal stress of OLED. And base on the principal stress to compare the strengths and weaknesses of two techniques. According to FEM simulation results, sucker top side peeling will induce lower principal stress state that can improve the yielding rate of the AMOLED display.