可撓性有機發光二極體顯示器的熱應力和翹曲分析

Abstract

可撓性有機發光二極體顯示器(FOLED)是相當受到矚目的新型顯示器，是將OLED製作塑膠基板上。氧化銦錫(Indium tin oxide，ITO)是FOLED的陽極導電層，是一種透光性極佳導電性良好的材料，也是廣泛應用在顯示器及觸控面板中常見的陽極材料。在ITO的製程中，要將ITO濺鍍在具有阻隔層的可撓性基板上，因為ITO的製程需要較高的溫度，在製程降溫過程中，會因多層結構不同的熱膨脹係數，使的基板產生翹曲且有應力的殘留。 本文主要是透過Suhir的三層薄板理論來分析製程降溫產生的翹曲和殘餘應力，並配合商用數值分析軟體Ansys，建構線性和黏彈實體模型來模擬這個現象，不只能與Suhir的二維理論互相作比較，還考慮了材料的黏彈情形，將更符合實際情形。本文並分析不同阻隔層的熱膨脹係數、楊氏模數對於基板翹曲和殘餘應力的影響，也分析各層的厚度對殘餘應力和翹曲的影響，透過這樣的分析，提供設計者最佳的阻隔層材料選擇和各層厚度設計，達到減少殘餘應力和翹曲的目的，提高元件的可靠度和壽命。

Flexible Organic Light Emitting Diodes (FOLEDs) that attracted much attention are new display technology. A flexible organic light emitting diode is typically fabricated on a thin plastic substrate so that the resulting device can be flexible and bendable. Indium tin oxide (ITO) is used as the anode of FOLED because of high optical transmission and low electrical resistivity. Indium tin oxide (ITO) has also been widely applied in the flat panel display and touch panels. A sputtering deposition method is applied to prepare Indium tin oxide (ITO) on a flexible substrate containing thin barrier layer. ITO must be manufactured at an elevated temperature and subsequently cooled to a low temperature. However, the mismatch of coefficient of thermal expansion between every two layer of them induces large warpage and residual stresses during cooling process. The object of this thesis is to analyze warpage and residual stresses by using Suhir’s structural analysis approach. In addition, we also create elastic and viscoelastic models to simulate our problem by using commercial FEM software, Ansys. So we can compare Suhir solution with simulation. In the thesis, we also discuss different kind of barrier and different thickness of each layer to compare warpage and residual stresses. By building the thermal stress analysis system, the analytic results may help designer to choose correct material and thickness to reduce warpage and residual stresses. It is helpful to increase product reliability and life.