Fabrication of a novel contact-enhanced horizontal sensitive inertial micro-switch with electroplating nickel

• A nickel MEMS inertia switch has been designed and fabricated.
• The switch was modeled and simulated by finite element ANSYS software.
• The threshold acceleration and work frequency was analyzed and predicted.
• The process is easier and the contact time is prolonged effectively.
• The switch has better unidirectivity and reliability.

A nickel MEMS inertia switch with horizontal single sensitive direction has been designed and fabricated on quartz substrate based on surface micromachining technology. MEMS inertia switch consisting of three main parts: the proof mass suspended by the folded springs as the movable electrode, the upper beam and back pillars as a barrier system and the forward novel L-shaped elastic cantilever beams as the fixed electrode. The threshold acceleration of designed inertial micro-switch is analyzed and predicted. The stiffness of folded spring has been simulated, which indicates that it is much stiffer in one direction than the other two ones. The simulation of dynamic contact process of the model demonstrates that the threshold acceleration of designed micro-switch is about 18 g and contact time is about 210 μs when the applied shock pulse width period is 0.006 s. The modal analysis and the simulation of impact process in non-sensitive direction reveal the designed structure has a good reliability. The fabricated micro-switch has been tested by dropping hammer system, and the test results show that the threshold acceleration is about 18 g and contact time is about 216 μs, which are in good agreement with those simulated ones.

The inertia micro-switch consists of three main parts: the proof mass as the movable electrode which is suspended by four folded rectangle springs; two elastic cantilever beams with contact point as fixed electrode to prolong the contact time; and the barrier system which consists of reverse direction protection pillars and two bridge-type beams above the proof. In this design, the movable electrode moves toward to fixed electrode and touches it, switching the external circuit on when the acceleration in the sensitive direction exceeds the threshold.Figure optionsDownload as PowerPoint slide