With MEMS (Micro-electro-mechanical systems) becoming increasingly commonplace
in many different industries, the need for more robust microstructures
that can withstand high-shock environments is growing in importance.
Literature currently available is yet to reveal a MEMS shock-absorber which
meets our set of requirements, namely that it is suitable for both space and
terrestrial applications, is easily incorporated into current MEMS fabrication
methods and can absorb significant amounts of energy without needing
a power source or without adversely affecting the performance of the device.
This thesis presents a novel solution for the shock protection of MEMS
which successfully satisfies the requirements stated above. Metal microstructures,
created through the reflow of solder, are successfully used to armour
and protect delicate silicon MEMS suspensions. A brittle silicon-silicon impact
is replaced with a ductile metal-metal impact. The metal protects the
silicon from fracturing at the point of impact during a high-shock event and
absorbs a significant proportion of the collision energy through plastic deformation.
A model suspension system is used to assess the performance of metalarmouring
as a MEMS shock-absorber. Two metal-bumper designs, surface-mounted solder bumpers and solder bumpers integrated into the sidewalls
of the suspension system are fabricated and tested in a drop-test rig at acceleration
levels of up to 6000g. The surface-mounted bumpers, formed by reflowing solder on metallised pads (plated on the suspension surface), were
found to fail on impact at the pad-wafer interface. The integrated bumpers
are designed to combat the short-comings of the surface-mounted bumpers.
Two solder balls are reflowed in through-wafer conduits within the suspension
sidewalls, creating substantial solder bumpers which are mechanically
keyed in place. The integrated bumpers proved to be shear resistant and to
double overall the shock resistance of the MEMS suspension.