在先進電子封裝設計中，由於晶圓級封裝具有尺寸及電性上的優勢而成為手持式電子產品中主要零件之一，而擴散型晶圓級封裝因擁有特殊之重新佈線(redistribution)與凸塊(bumping)的製程且擁有不需要底膠保護之特性，具有高度系統整合及重工性而受到重視，高分子介電材料在擴散級晶圓級封裝製程中扮演著重要的腳色，當整體結構設計不良時，晶圓級封裝將會因為晶片與基板間的熱膨脹量之不匹配而導致破壞，進而造成元件的失效，因此，連接矽晶片和銅墊片之介電材料，除了用來絕緣外，還具有應力隔絕的作用，在晶圓級封裝中，由於少了底膠的保護，介電保護層的厚度更能使互聯系統的可靠度上升，增加疲勞壽命。
為了正確模擬材料行為並預測可靠度，本文利用25°C至175°C之潛變實驗來量測介電薄膜之線黏彈行為，並使用時間－溫度重疊原理(time-temperature superposition principle)來建構材料之本構模型；經由時間－溫度重疊原理可得到材料在長時間下之主曲線，並使用9級之Prony級數來進行曲線擬合與參數求得；最後利用此模型進行實驗結果之比對與模擬，驗證結果顯示，此模型可良好地預測介電薄膜在不超過200°C時之線黏彈行為，可用來此推測薄膜在封裝過程中反覆升溫降溫時的反應。

The fan-out wafer level package (WLP) is one of the focus areas in packaging research for handheld electronic applications due to its advantages in body size, electrical performance and system integration capability. The fan-out WLP is constructed by molding single or multiple silicon chips in one package, and forming the electrical interconnection between dies and the motherboard-connecting solder balls by using redistribution copper traces sandwiched in polymer dielectric thin film layers. The polymer dielectric material plays an important role in the package reliability in the way of providing stress buffering to the solder bump structure. In order to accurately assess the reliability of various WLP designs, it is critical to characterize the constitutive behavior of the polymer dielectric thin film and apply it in the stress and reliability modeling.
In this study, creep experiments at uniform temperatures between 25°C and 175°C were performed to characterize the viscoelastic behavior of the polymer dielectric of interest. From the experimental results it is observed that the polymer dielectric material exhibits linear viscoelastic behavior under strain level lower than 3%. A Prony series is developed to model the viscoelastic behavior of the dielectric material. Estimations of the dielectric material responses under creep and additional loading profiles were obtained by directly integrating the stress-strain convolution integral and by numerical finite element simulations, and were compared to experimental data for model validation. The comparison showed that the predictions by using the Prony series based linear viscoelastic model agrees well to the experimental data.

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