用于低g_n值微惯性开关的低刚度平面微弹簧设计与制作

Development of planar micro-spring with low stiffness in low g_n micro inertial switch

针对低gn值微惯性开关对微弹簧系统刚度的要求（0．1～1N／m数量级），设计了一种基于平面矩形螺旋梁结构的平面微弹簧。假设材料均匀、连续且具各向同性，根据材料力学的卡氏定理和线弹性理论，推导得到了微弹簧的弹性系数计算公式，并根据ANSYS有限元仿真分析结果对其进行了修正。基于多层高深宽比硅台阶刻蚀方法，采用MEMS体硅加工工艺，完成了微弹簧的制备，划片后微弹簧芯片尺寸为7mm×7mm×0．3mm。分析结果表明，完善后的弹性系数计算公式与ANSYS仿真结果更为接近，可直接应用于微弹簧的结构优化设计以简化设计过程。纳米压痕法的测试结果表明，微弹簧样品的弹性系数约为0．554N／m，满足设计要求。该微弹簧具有体积小、结构简单、加工容易实现等特点，其成功研制为实现低gn值微惯性开关的工程实用化奠定了基础。

A planar micro-spring based on a planar rectangular helical spring was designed for a low-gn micro inertial switch with the micro-spring in stiffness up to 0.1-1 N/m magnitude. The elastic coef- ficient formula of the micro-spring was derived with the Castigliano＇s theory and the linear elasticity theory based on the assumption that the material property was uniform, homogeneous and isotropic, and then it was modified by the ANSYS finite element method. The micro-spring was fabricated by using the MEMS bulk micromachining process based on the multi-step ICP etching method, and the bulk of chip was about 7 mm × 7 mm× 0.3 mm in size. The theoretic analysis shows that the results agree well with the ANSYS simulation results, which demonstrates that the optimized formula can be directly applied to the optimization design of the micro-spring to simplify the design process. The nanoindentation test results show that the elastic coefficient of the fabricated micro-spring is about 0. 554 N/m. The planar micro spring has the advantages of small size, simple structure and easy fabrication, and it can lay the foundation for the engineering applications of low-gn micro inertial switchs.