A Robust Micro Mechanical-Latch Shock Switch With Limited Deformation Space

Abstract

Mechanical-latch mechanisms are often used in shock switches to turn the switches on by the desired inertial force in the specified sensing direction. However, while experiencing an unexpected large inertial force in opposite sensing direction, the switch might slip off the contact electrode and return back to its initial position to cause malfunction, so-called slippage effect. Here a robust micro mechanical-latch shock switch to resist the slippage effect is reported by limiting deformation space on one side of the latch. An analytical model is developed to determine the dimensional parameters. The proposed shock switch made of Ni is fabricated by the metal-based surface micromachining technology so that low contact resistance can be easily achieved. The experimental results show that the switch can be successfully latched after experiencing a downward shock of 13.11 G, close to the simulated threshold level of 12.14 G. Furthermore, even after applying over 2000 G opposite impact acceleration, the switch can remain latched due to the limited deformation space design, whereas the switch without the limited space design cannot. The contact resistance after latching is demonstrated around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40\Omega $ </tex-math></inline-formula> , six orders less than the resistance before latching. These results verify the accuracy of the static model and the robustness of the proposed micro shock switch design to avoid undesired unlatching with low contact resistance at compact size.