壓電薄膜製程開發及其聲振特性分析

Abstract

本研究從壓電薄膜製程出發，首先建構一套生產壓電薄膜的流程，製程步驟包含溶液調配、塗佈溶液、退火、極化和電極濺鍍等流程，以這些流程製作所需的壓電薄膜，接著測量相關的材料參數性質後，將其製作成薄膜形式的聲學元件以供振動和聲學上的實驗檢測。 製作出實驗所需的試片後，對於其振動和聲學特性進行分析，分析以理論解析、有限元素模擬和實驗量測進行比較，理論研究方法包含了分別以薄膜振動理論和壓電圓盤振動理論這兩種，同時在搭配雷射都卜勒振動儀(Laser Doppler Vibrometer, LDV)實驗量測結果反算得到的張力，帶入理論和有限元素模擬中，以此得出共振頻率與模態振形的結果，其中模擬如同理論，同樣分別採用薄膜與壓電圓盤的力學模型進行分析，先與理論相互比較結果觀察誤差後，接著利用LDV進行聲學元件的全域模態量測，觀察不同力學模型於實際壓電薄膜的振動分析適用性。 選定與實際壓電薄膜振動較為接近的分析模型後，應用於後續的自由聲場模擬，並與無響室（Anechoic Room）的量測結果做比較，將各種不同類型的自製薄膜試片和市售薄膜試片在無響室量測的頻響曲線進行比較，評估不同試片間的聲音特性以及振動的關係。 最後會將自由音場所量測的不同類型試片，以人工耳(Artificial Ear)進行封閉音場的量測，同樣比較不同試片量測的頻響曲線結果，觀察不同製程條件的試片之聲音特性的優劣，評估未來做為耳機發聲元件的可行性。

This study begins with the process of manufacturing piezoelectric thin films. Initially, a production process for piezoelectric thin films is constructed, which includes solution preparation, solution coating, annealing, polarization, and electrode sputtering. These steps are used to produce the required piezoelectric thin films. After measuring the relevant material parameters, simple acoustic components are made from these films for vibration and acoustic testing. After producing the necessary test samples, their vibration and acoustic characteristics are analyzed. The analysis primarily involves theoretical, finite element simulation, and experimental measurement comparisons. The theoretical research methods include analyzing the piezoelectric thin film samples using thin-film vibration theory and piezoelectric disk vibration theory. Coupled with the tension obtained from the experimental measurements using a Laser Doppler Vibrometer (LDV), the resonance frequencies are calculated by incorporating these values into the theories and finite element simulations. The simulation, using the corresponding theoretical analysis, is conducted with both thin-film and piezoelectric disk models. The results are first compared with theoretical predictions to observe discrepancies, followed by a comparison of the resonance frequencies between the two different models to study their respective vibration characteristics. Subsequently, LDV is used to conduct global modal measurements of the acoustic components to determine which model best fits the actual vibration behavior of the piezoelectric thin films. After selecting the model that closely corresponds with the actual vibration of the piezoelectric thin films, this model is used for the free-field simulations. These simulations are then compared with measurements taken in an anechoic room to analyze and discuss the differences between the results. Additionally, the frequency response curves of various self-made film samples and commercial film samples measured in the anechoic room are compared to evaluate the sound characteristics of different samples. Finally, the various types of samples measured in the free sound field are tested in a pressure field using an Artificial Ear. The measured frequency response curves are compared to observe the sound and vibrating characteristics of different samples and to evaluate their feasibility as headphone sound components in the future.