Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Polarity-responsive
Reexamination Certificate
2002-04-19
2004-08-17
Nguyen, Tuyen T. (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Polarity-responsive
C335S080000, C200S181000
Reexamination Certificate
active
06778046
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to latching micro magnetic relays.
More particularly, the present invention relates to methods of packaging latching micro magnetic relays and the various packages.
BACKGROUND OF THE INVENTION
Recently, novel latching micro magnetic relays were discovered. The novel latching micro magnetic relay is based on preferential magnetization of a soft magnetic cantilever in a permanent external magnetic field. Switching between two magnetic states is accomplished by momentarily changing the direction of the cantilever's magnetization by passing a short current pulse through a planar coil situated adjacent the cantilever. Once the relay is switched, it is held in this nonvolatile state (latched) by the permanent external magnetic field. Additional information as to the construction and operation of the novel latching micro magnetic relay is disclosed in a copending U.S. patent application entitled “Electronically Switching Latching Micro-Magnetic Relay and Method of Operating Same”, with Ser. No. 09/496,446, filing date Feb. 2, 2000, and incorporated herein by reference. While a specific latching micro magnetic relay is described above, it will be understood that other Micro Electro Mechanical Systems (MEMS) devices that incorporate magnets are also included in this description.
In the prior art, the cantilever for micro magnetic switches was fabricated as a complete portion of the switch by providing a sacrificial layer of photoresist, depositing the material of the cantilever on the surface of the photoresist and then etching or otherwise dissolving the photoresist layer to provide a cantilever. One problem with this prior art method is that any process steps performed subsequent to the application of the photoresist layer are seriously limited because of potential damage to the photoresist material and, thus, potential faults or weaknesses in the final product.
Also, in most prior art packaging techniques relatively high temperatures are required for some of the later steps. These high temperatures can seriously affect magnets and some of the other components enclosed in the packages. Further, the materials that could be used as the supporting substrate for the MEMS devices is seriously limited by the fabrication and packaging techniques.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object the present invention to provide a new and improved latching micro magnetic relay and package.
Another object of the present invention is to provide a new and improved latching micro magnetic relay package that can be fabricated on a variety of substrates.
Another object of the present invention is to provide a new and improved latching micro magnetic relay package that is easy and inexpensive to manufacture.
A further object of the present invention is to provide a new and improved latching micro magnetic relay package fabricated with low temperature assembly.
Still another object of the present invention is to provide a new and improved latching micro magnetic relay package that can be hermetically sealed on any of a variety of improved substrates using relatively low temperature.
SUMMARY OF THE INVENTION
Briefly, to achieve the desired objects of the present invention in accordance with a preferred embodiment thereof, provided is a method of forming a package and sealing a MEMS device in the package including the steps of providing a supporting substrate, forming at least one contact for the MEMS device on the surface of the supporting substrate and providing an external connection to the contact, forming a cantilever on the surface of the supporting substrate, the cantilever being positioned to come into electrical engagement with the contact in one orientation, and depositing a seal ring on the surface of the supporting substrate circumferentially around the contact and the cantilever. The method further includes the steps of forming a cap member with a cavity and a continuous edge circumferentially around the cavity, the cavity being designed to receive the cantilever and contact therein, and depositing a seal ring on the continuous edge of the cap member. The package is then sealed by sealingly engaging the seal ring on the continuous edge of the cap member to the seal ring on the surface of the supporting substrate.
In a preferred and more specific embodiment, the sealed package includes a supporting substrate with a surface, at least one contact for the MEMS device on the surface of the supporting substrate with an external connection to the contact and a cantilever on the surface of the supporting substrate, the cantilever being positioned to come into electrical engagement with the contact in one orientation. A metal seal ring is fixed on the surface of the supporting substrate circumferentially around the contact and the cantilever. A cap member is formed with a cavity and a continuous edge circumferentially around the cavity. The cavity is designed to receive the cantilever and contact therein with the continuous edge in mating engagement with the metal seal ring on the surface of the supporting substrate. A metal seal ring is fixed on the continuous edge of the cap member. The metal seal ring on the continuous edge of the cap member is sealingly engaged with the metal seal ring on the surface of the supporting substrate. In the preferred embodiment the two metal seal rings are sealingly engaged or fixed together by a solder alloy that is reflowed in an inert environment without the use of flux.
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Shen Jun
Stafford John
Tam Gordon
Goltry Michael W.
Magfusion Inc.
Nguyen Tuyen T.
Parsons Robert A.
Parsons & Goltry
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