为了实现流场壁面剪应力等动态定点分布测量,提出了一种新的柔性热膜传感器阵列结构,并介绍了其制作工艺。旋涂并升温固化制备聚酰亚胺柔性薄膜衬底,在衬底上溅射沉积金属镍膜,并用剥离工艺成型热敏电阻元件阵列及其引线区底膜。然后在引线区底膜上电镀沉积铜膜,再剥离成型铜引线。通过电镀可以经济快速地获得较厚的引线铜膜,使得引线电阻远小于热敏元件阻值,有利于减小引线的热敏干扰。经热敏性能测试,其电阻温度系数达到3.6×10-3/℃以上,线性度优于0.7%,并且热敏响应速度极快;结合风洞试验验证了该传感器测量壁面剪应力的有效性,并且获得了较好的测量重复性。该传感器阵列结构简单,工艺成本和复杂度较低,提高了用于非平面应用时柔性热膜元件与引线间的连接可靠性,为高曲率表面的非破坏性动态流场参数测量提供了新手段。
In order to measure dynamically the local temperature or wall shear stress of a flow, a new structure of flexible hot-film sensor array and its fabrication process are proposed. The thermal sensing material, nickel, is sputtered on a polymide flexible substrate, and then patterns to form both the thermal resistor array and the leads' sublayer, on which copper is electroplated and lift-off patterned to form the metal leads. Electroplating can realize economically higher thickness of the lead film than does sputtering to keep the lead resistance small and minimize its influence on thermal sensing. High temperature coefficient of resistance (TCR) is obtained over 3.6×10-3/℃ with nonlinearity under 0.7%. Wind tunnel experiments show that the developed sensor can measure wall shear stress with high repeatability. This flexible sensor array possesses reliable connections between the flexible thermal resistors and leads, and can be used to measure the dynamic distribution of flow parameters on non-planar surfaces.
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