MEMS COMMUNITY,
I am a graduate student at North Carolina State University working on a
project for my Technology Commerialization course. Our team is
currently looking at using an MSM (Magnetic Shape Memory) alloy to
replace the cantilever and magnet switching mechanism in MEMS switches,
most notably in RF applications. I have attached a brief "memo" {pasted
below} about our idea, and would appreciate if you took the time to read
it. In the memo, we have made quite a few assumptions. If you read
something that you would tend to disagree with, please let me know. In
our research on MEMS, we met with a professor here at NC State
University. He raised the doubt that the MSM would consume too much
power. He pointed out the following specs for MEMS switching:
1) Power handling capacitance
cell phone application: 1W
radar application: 100W
current MEMS switch: 2W
2) Switching time
cell phone application: 10u
radar application: <10u
Microlab's product: ? It seems like 200us
3) Power consumption:
cell phone application: 1-5mA(He is not sure about this figure)
How do you think the MSM alloy would suffice in a MEMS application,
given the specs above? Please provide any additional information,
advice, insight, etc...
Again, this is just a newly developed product idea/thought. Extensive
research needs to be done, but we are very interested MSM MEMS
technology.
These markets are new to us, as we are graduate students doing actuator
research and product ideation. We have no prior experience with
actuator technologies.
It may be necessary for us to talk over the phone. If so, what would be
a number & time I could reach you? Please let me know how you feel
about these ideas, any concerns you may have, etc... I greatly
appreciate you taking the time to help.
Sincerely,
Clinton Miller
MEMO
Microelectromechanical Systems (MEMS) Switch
With an estimated market of nearly $350M within the next
five years, the fast-growing arena of RF applications for MEMS devices
offers a substantial opportunity to newcomers1. With a market demand
for reliable, low power wireless systems, the use of MEMS devices in
wireless applications is increasing. Although MEMS switches can offer
low power consumption and decreased distortion, the performance of these
switches has been doubted due to considerable warping and buckling under
heavy stresses2. In addition, heavy packaging constraints can also
greatly affect the performance of the device, not to mention the cost to
the consumer. We propose a new MEMS device where the current switching
technology is replaced by an MSM alloy switching technology.
The basic structure of a bistable MEMS switch (Microlab's MagLatch) is
shown below:
As residual stresses act on the cantilever, it can
experience warping and buckling affects. To alleviate this problem, we
propose the replacement of the cantilever and magnet with an actual MSM
alloy and base. Instead of components that are susceptible to residual
stresses, an MSM alloy with a high strain vs. load capability would be
used. This capability allows the alloy to endure high stresses under
heavy loads, a much-needed characteristic in MEMS switching. Because of
this capability, the durability and reliability of current MEMS devices
will be greatly enhanced.
Under current packaging constraints, great care must be taken to ensure
that no outside moisture or contaminants contact the packaging. These
outside forces can greatly affect the magnetization of the cantilever
and magnets, switching thresholds, and overall reliability1. Because of
these rigorous constraints, packaging costs account for a significant
portion of the actual cost of the MEMS device. By replacing the current
switching technology with an MSM alloy technology, packaging constraints
would be drastically lowered. MSM alloys offer a low susceptibility to
outside contaminants, thus allowing for the minimization of these
constraints as well as allowing large volume application costs to be
drastically reduced.
The basic MSM switching technology that we propose as a replacement to
the current technology is outlined below3:
A short current pulse is generated through the coil, causing the MSM
alloy to expand lengthwise. As this alloy expands against the
stationary base, the extension will cause the base to bend towards the
electrical contact. This bending will continue until the contact on the
alloy has completed the circuit by connecting with the electrical
contact. A reverse magnetic field would then be applied to open the
switch ("break" the connection). As with the current switching
technology, this proposed replacement would also be a bistable
technology, thus resulting in a low power device.
[1] Bogatin, E. "RF MEMS Switches and Their Packaging Challenge."
Technology News; Assembly and Packaging; Pg. 44. August 01,
2002.
2 Peroulis, D., Pacheco, P., Sarabandi, K. , Katehi, L. "Alleviating
the Adverse Effects of Residual Stress in RF MEMS Switches."
3 www.microlab.net
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