Photosensitive polymers or dielectric materials such as polyimides (PIs) have been used in fan-out wafer-level packaging process (FOWLP) as a redistribution layer for quite some time. In the condensed 2-D and 3-D packaging processes, the dielectric materials are applied multiple times to create as many as four or five redistribution layers. At the end of the process, the first layer may experience up to four times of heat cycles in which the polymer properties may change. However, the effect of heat cycles on properties of dielectric film as well as their contributions to the wafer-level warpage is still unclear. To understand the changes of materials’ properties after several heat cycles, the thermal and thermo-mechanical properties of negative-tone and positive-tone types of dielectric films are characterized by using the thermomechanical analysis (TMA), dynamic mechanical analysis (DMA), and thermogravimetric analysis (TGA). The glass transition temperature ( ${T}_{g}$ ), coefficient of linear thermal expansion (CTE), and modulus (storage, ${E}'$ , and loss, ${E}''$ ) are analyzed and compared. In addition, the morphology of the films before and after heat cycles is also analyzed.

中文翻译：

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热循环对介电材料热力学性能的影响

在扇出晶圆级封装工艺（FOWLP）中，光敏聚合物或介电材料（如聚酰亚胺（PI））已经用作重新分配层已有相当一段时间了。在压缩的2D和3D封装过程中，多次应用介电材料以创建多达4个或5个重新分布层。在该过程结束时，第一层可能经历多达四次的热循环，其中聚合物性质可能会发生变化。然而，热循环对介电膜性能的影响以及它们对晶片级翘曲的影响仍然不清楚。为了了解几次热循环后材料性能的变化，通过使用热机械分析（TMA），动态力学分析（DMA）和热重分析（TGA）来表征负电类型和正电类型的介电膜的热和热机械特性。玻璃化温度（ $ {T} _ {g} $ ），线性热膨胀系数（CTE）和模量（存储， $ {E}'$ 和损失， $ {E}''$ ）进行分析和比较。另外，还分析了热循环之前和之后的膜的形态。