MEMS fabrication technology has very high fabrication precision, but there is still fabrication error inevitably like any
other fabrication technology. We adopt LIGA technology to fabricate a Micro Electro-Mechanical System. From the
analysis of fabrication process, the fabrication errors of MEMS part consist of mask and LIGA fabrication error. The
designed MEMS parts can be divided into metal and PMMA part. Synthesizing the mask and LIGA fabrication errors,
the errors of metal entity and cavity structure are -10.5μm~+5.5μm and -5.5μm~+10.5μm. The errors of PMMA entity and cavity structure are -5μm~+10μm and -10μm~+5μm. Analyzing each situation, the most interference dimension of the four assembling situations is 20μm. According to the conclusion, we leave 10μm margin for each of the two parts
assembling together. So the whole margin of the two parts is 20μm, which ensures that the two MEMS parts can be assembled reliably. Measuring the fabricated MEMS part with a micro precision measurement equipment indicated that the fabrication error was in the scope of theoretical analysis. The fabricated LIGA MEMS system can be assembled
reliably and the centrifugal experiment indicated that the motional part worked well and moved to the destination position.
With good mechanical performance and mature fabrication technology of LIGA and UV-LIGA, Ni is chosen as the
material of S style MEMS microspring. At 24°C and 25% relative humidity, five different points in LIGA Ni sample
were tested with the MICRO HARDNESS TESTER, and the Young's modulus was 219GPa. From the tensile tests of
UV-LIGA Ni sample the Young's modulus of UV-LIGA Ni is 180GPa. The S style microspring was fabricated by LIGA
and UV-LIGA technology separately. Applying the Castigliano second theorem of energy method in macro theory, the
spring constant formulas of S style microspring in three application modes were deduced, and the correctness was
verified by the FEA (Finite Element Analysis) simulation. The experiments of S style microspring's deformation
properties were carried out by the Tytron250 micro force test machine and a tensile measurement system separately. The
experimental results agree with the theoretical analysis. Based on the above analysis, the change laws of microspring's
spring coefficient in different application patters are summarized.
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