Abstract
The use of micro-contacts has been demonstrated in various radio frequency (RF) applications. However, the premature failure of such devices under alternating current (AC) operations is still a hurdle to further development. In this work, modified gray scale lithography is performed to fabricate two types of gold–gold (Au–Au) micro-contacts: hemispherical-planar and hemispherical-2D pyramid. The performance of these devices was investigated under low frequency, low amplitude AC conditions with external circuit loads. A custom-made experimental setup which uses various load configurations, controls the frequency of the applied voltage and modifies the cycle rate of switch operation to obtain the contact resistance as a function of number of cycles (up to 107 cycles). Nearly 87% of the tested devices (13 out of 15 hemispherical-planar micro-contacts) were found to be in good operational condition and passed the 10 million cycle mark successfully. A steady gain and large swing in the value of contact resistance was also observed near the end of all, but one, tests. Such changes in contact resistance were found to be permanent as none of the devices recovered completely. On the other hand, the hemispherical-2D pyramid micro-contact performed better than the planar one as it also passed 107 cycle mark with low and remarkably stable contact resistance throughout the testing span. This study suggests that micro-contacts with ‘engineered’ surface structures with external loads applied are a viable solution to premature failure and high contact resistance in micro-contacts under low frequency AC operations.
Highlights
Micro-contacts have been the center of active research for years due to their potential use in various radio frequency (RF) applications, such as telecommunications and remote sensing [1,2,3]
It is clear that external load components are critical for extending a micro-contact’s lifetime, assuming some level of variability in contact resistance is tolerable
It is concluded that while this external loading clearly extends the lifetime of the micro-contacts, contact resistance is still being affected
Summary
Micro-contacts have been the center of active research for years due to their potential use in various RF applications, such as telecommunications and remote sensing [1,2,3]. Despite such intense research, there are specific concerns that need to be resolved to improve their performance and lifetime. One possible solution is to first gain an understanding of the micro-switch response at lower frequencies to provide essential insight into the fundamentals that help to explain higher frequency behavior. In a previous study on the effect of low frequency AC conditions, device failure occurred between 103 –105 cycles which was much lower than the set target of 107 switching cycles [4]
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