Switch assembly and method of forming the same

FIELD OF THE INVENTION

The present invention generally relates to a microelectromechanical system (MEMS), and more particularly to a MEMS switch assembly and a method of forming the MEMS switch assembly.

BACKGROUND OF THE INVENTION

Communications systems such as wireless handsets and other electrical and/or mechanical systems often require high performance switch assemblies that exhibit one or more of the following characteristics: small size, low power consumption in the on-state, high isolation in the off-state, low signal distortion or low activation voltage. Accordingly, it is desirable to provide a MEMS switch assembly that can offer one or more of these characteristics in a variety of applications such as radio frequency (RF) and microwave applications and a method for forming the MEMS switch assembly. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the drawings and the appended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction with the appended drawing figures, wherein like numerals denote like elements, and:

FIG. 1

illustrates a perspective view of a microelectromechanical system (MEMS) switch assembly according to a non-limiting aspect of the present invention;

FIG. 2

illustrates a perspective view of another switch assembly formed according to a non-limiting aspect of the present invention;

FIG. 3

illustrates a perspective view of still another switch assembly formed according to a non-limiting aspect of the present invention; and

FIG. 4

illustrates a perspective view of a portion of a switch assembly being formed according to a non-limiting aspect of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The following detailed description of a preferred embodiment is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention.

The present invention provides a microelectromechanical system (MEMS) switch assembly for radio frequency (RF), Microwave or other applications. Generally, the switch assembly includes a switching member and a first lead that is spaced apart from a second lead. The switching member includes a first portion having an insulating material with a first dielectric constant and a second portion having a conductive material with a second dielectric constant. The switching member is selectively moveable (e.g., translatable, rotatable or otherwise mobile) to allow the second portion of the switching member to provide a robust electrical connection between the first and second leads when such a robust connection is desired and to allow the first portion to provide a less robust electrical connection between the first lead and the second lead when a less robust connection is desired. As defined herein, the term “robust electrical connection” should be construed to include any connection capable of carrying enough current or having a low enough capacitance for its intended application. Also, as defined herein, the term “less robust electrical connection” should be construed to include any connection less robust than the connection allowed by the first portion of the switching member, including a substantially non-existent electrical connection or short. Preferably, the first lead and second lead are configured for substantially continuous contact with one or more surfaces of the switching member as the switching member is moved to selectively provide more and less robust connections between the leads.

Referring to

FIG. 1

, there is illustrated a MEMS switch assembly

10

according to one preferred exemplary embodiment of the present invention. The MEMS switch assembly

10

comprises a switching member

12

, a first lead

14

and a second lead

16

. The switching member

12

includes a cylindrical or “disk-shaped” portion

18

having a first generally circular surface

20

generally opposing a second generally circular surface

22

. The first surface

20

and second surfaces

22

are separated by a thickness

24

. Furthermore, the switching member

12

includes an annular outer periphery

40

that extends along the thickness

24

of the switching member

12

. A cylindrical rod

28

that can be attached to or integral with the disk portion

18

supports the disk portion

18

. The cylindrical rod

28

extends generally centrally through the disk portion

18

and through the first surface

20

and second surface

22

of the disk portion

18

and includes a first end

30

and a second end

32

.

In the embodiment illustrated in

FIG. 1

, the disk portion

18

of the switching member

12

is divided into a first portion

34

and a second portion

36

by an interface

38

. The first portion

34

is at least partially formed of one or more insulating materials. Without intending to be limited thereby, insulating materials for the first portion

34

may include ceramics or other materials having relatively high dielectric constants. Examples of insulating materials may include titanates or zirconates such as lead zirconate (PbZrO

3

) to strontium titanate (SrTiO

3

). Appropriate values for the first dielectric constant (K

1

) of the insulating materials range from about 100 to about 500, and preferably are within the range of about 150 to about 200, and more preferably are about 170 or less than about 170. The second portion

36

is at least partially formed of a relatively conductive material such as borosilicate glass or any other suitable material having a second relatively low dielectric constant (K

2

). Appropriate values for the second dielectric (K

2

) of the relatively conductive material of the second portion

36

range from about 2 to 10 and preferably are within the range 3 to 6 and more preferably are about 3.9 or less than about 3.9.

The first portion

34

may be attached to the second portion

36

in a variety of manners to form the switching member

12

. The first portion

34

may be adhesively or otherwise secured to the second portion

36

. Furthermore, the rod

28

may be secured to the first portion

34

and second portion

36

using any number of techniques such as adhesive attachment or otherwise.

In a preferred embodiment, the cylindrical rod

28

is integrally formed as a single component with a generally annular portion

40

and the cylindrical rod

28

and the annular portion

40

are formed of a metal such as gold, aluminum or the like. The annular portion

40

and the rod

28

can also be formed of silicon or other suitable materials. Also preferable, the insulating and conductive materials of the first portion

34

and second portions

36

are deposited or otherwise attached to the annular portion

40

to respectively form layers (

42

,

44

) of such materials. Deposition of the materials can be accomplished by physical vapor deposition methods such as sputtering with a solid cathode or by other suitable deposition methods. Momentarily referring to

FIG. 4

, cathodes

50

can be used to sputter materials through a shadow mask

52

having a pattern

54

such that the materials are deposited according to the pattern

54

upon a substrate

56

such as that shown in

FIG. 4

or upon the annular portion

40

of the assembly

10

of FIG.

1

.

Referring to

FIG. 1

, the first lead

14

and second lead

16

are elongated metal strips that are generally “S-shaped” and extend between a first end

62

and a second end

64

. However, any number of shapes and configurations can be utilized for the leads in accordance with the present invention. Furthermore, the first lead

14

and second lead

16

are in contact with one of the first surface

20

or second surface

22

of the switching member

12

. The first lead

14

and second lead

16

can be arranged such that the first end

62

of the first lead

14

is in contact with the first surface

20

of the switching member

12

and the first end

62

of the second lead

16

is in contact with the second surface

22

of the switching member

12

. The skilled artisan will recognize that a variety of leads are known and can be used in accordance with the present invention. Optionally, the first surface

20

and the second surface

22

of the switching member

12

can be metallized to assist in contacting the first lead

14

and the second lead

16

, and a gap is preferably provided between the metallized surfaces of the first portion

34

and second portion

36

to insure substantial electrical (e.g., DC, AC and RF) isolation of the first portion

34

from the second portion

36

. The second end

64

of the first lead

14

and second lead

16

are electrically connected to components (e.g., circuits, antennas, filters or the like) within an electrical device).

To install the MEMS switch assembly

10

into an electrical device such as a portable telephone, cellular telephone or any other number of mechanical and/or electrical devices, the first end

30

and second end

32

of the support member or cylindrical rod

28

can be inserted into cavities (not shown) formed within the device such that the switching member

12

is rotatable about a central axis

66

that extends through about the center of the switching member

12

. In operation, the switching member

12

may be selectively rotated such that the second portion

36

provides a robust electrical connection between the first lead

14

and second lead

16

and the switching member

12

can be selectively configured with a rotation such that the first portion

36

provides a less robust electrical connection between the first lead

14

and the second lead

16

. The skilled artisan will recognize that the MEMS switch assembly

10

can be used to open and close a variety of electrical connections and/or provide varying impedances and that the first end

62

and second end

64

of the first lead

14

and second lead

16

can be connected to portions of a variety of circuits for switching a component in or out of the circuit.

In one exemplary embodiment, the switching member

12

can be used as an on/off switch for microwave or RF applications. In such an embodiment, the switching member

12

can be selectively rotated about the central axis

66

. During rotation, the first end

62

of the first lead

14

and second lead

16

can maintain a substantially continuous contact with the first surface

20

and second surface

22

of the switching member

12

. The switching member

12

can be rotated to at least two positions (i.e., an ON position and an OFF position). At a first position, the second portion

36

of the switching member

12

is physically located between the first lead

14

and the second lead

16

, thereby providing a robust electrical connection between the first lead

14

and the second lead

16

. This robust connection is provided with the low dielectric constant materials of the second portion

36

. At the first position, the MEMS switch assembly

10

can be configured in the ON position. At a second position, which can be achieved by rotating the switching member

12

approximately one hundred eighty degrees about the axis

66

, the first portion

34

of the switching member

12

is physically located between the first lead

14

and the second lead

16

, thereby providing a less robust electrical connection (e.g., a substantially non-existent electrical connection) between the first lead

14

and the second lead

16

because of the higher dielectric constant of the materials of the first portion

34

. At the second position, the switch assembly

10

can be configured in the OFF position.

In another preferred exemplary embodiment of the present invention, the switching member

12

can be used for configuring an antenna in a portable telephone, cellular telephone or any other electrical device utilizing an antenna. When used for configuring an antenna, a second set of leads (not shown) may be contacted with the first surface

20

and the second surface

22

of the switching member

12

in addition to the first lead

14

and the second lead

16

. One of the first set or second set of leads is connected to a transmitter (not shown) while the other set of leads is connected to a receiver (not shown) The leads are configured for contact with the first surface

20

and second surface

22

, and the switching member

12

is rotatable between at least two positions. When the phone is receiving transmissions, the member

12

is in a first position wherein the first high dielectric portion

34

is between the leads connected to the transmitter and the second low dielectric portion

36

is between the leads connected to the receiver. When the phone is transmitting, the member

12

is in a second position wherein the second low dielectric portion

36

is between the leads connected to the transmitter and the first high dielectric portion

34

is between the leads connected to the receiver.

Rotation of the switching member

12

can be accomplished with a variety of mechanisms and with a variety of methods and techniques. For example, the switching member

12

may be mechanically rotated with gears or the like. The switching member

12

can be rotated magnetically or electrostatically. The person of skill in the art will recognize that a variety of methods and/or apparatus are available for rotating the switching member

12

that are within the scope of the present invention.

Referring to

FIG. 2

, there is illustrated an alternate embodiment of a MEMS switch assembly

70

according to a preferred exemplary embodiment of the present invention. The MEMS switch assembly

70

comprises an alternative switching member

72

for use with the first lead

14

and the second lead

16

discussed with reference to FIG.

1

. In the alternate embodiment of

FIG. 2

, the switching member

72

is generally rectangular and has a first rectangular surface

74

generally opposing a second rectangular surface

76

. The first surface

74

and second surface

76

are separated by a thickness

78

. Furthermore, the switching member

72

includes a generally rectangular outer periphery

80

that extends along the thickness

78

of the switching member

72

.

In the alternate embodiment of the MEMS switch assembly

70

according to a preferred exemplary embodiment of the present invention, the switching member

72

is divided into a first portion

84

and a second portion

86

by an interface

88

. In a non-limiting embodiment, the first portion

84

is at least partially formed of an insulating material such as those described for the first portion

34

of the switching member

12

of

FIG. 1

, and the second portion

86

is at least partially formed of a conductive material such as those described for the second portion

36

of the switching member

12

of FIG.

1

. The insulating and conductive materials can be applied in a first layer

90

and second layer

92

, respectively, to a rectangular metal substrate

94

by deposition techniques such as those previously described in this detailed description of the drawings. The first lead

14

and second lead

16

can be arranged such that the first end

62

of the first lead

14

is in contact with the first surface

74

of the switching member

72

and the first end

62

of the second lead

16

is in contact with the second surface

76

of the switching member

72

.

The switching member

72

can be supported by the first lead

14

and second lead

16

and/or can be supported by a surface (not shown) of an electrical device along which the switching member

72

can be configured to slide and/or translate. Other suitable supports may also be used to support the switching member

72

while still allowing the switching member

72

to translate. In operation, the switching member

72

can be selectively translated such that the second portion

86

provides a robust electrical connection between the first lead

14

and second lead

16

and the switch member

72

can be selectively translated such that the first portion

84

provides a less robust electrical connection between the first lead

14

and second lead

16

. During such translation, the end

62

of the first lead

14

and second lead

16

can be configured to maintain substantially continuous contact with the first surface

74

and second surface

76

of the switching member

72

.

Translation of the switching member

12

can be accomplished with a variety of apparatus and/or methods. For example, the switching member

12

can be mechanically, electrostatically, magnetically actuated or actuated by any number of suitable means, for example. The skilled artisan will recognize that a variety of apparatus and/or methods of translating the switching member

72

can be employed within the scope of the present invention.

Referring to

FIG. 3

, there is illustrated still another alternate of a MEMS switch assembly

100

formed according to a preferred exemplary embodiment of the present invention, which is particularly suited for high-speed operations (e.g., as an antenna switch for time division multiple access (TDMA) radio applications). The MEMS switch assembly

100

comprises a switching member

102

similar in geometric configuration to the switching member

12

of FIG.

1

. The MEMS switch assembly

100

further comprises a first lead

104

, a second lead

106

and a third lead

108

. The switching member

102

of

FIG. 3

further comprises the rod

28

and the cylindrical or “disk shaped” portion

18

that has the first circular surface

20

generally opposing the second circular surface

22

, wherein the first surface

20

and second surface

22

are separated by a thickness

24

as discussed with reference to FIG.

1

.

In the alternate embodiment shown in

FIG. 3

, the cylindrical switching member

102

is divided into a first portion

114

, a second portion

116

, a third portion

118

and a fourth portion

120

by a pair of interfaces

126

. In a non-limiting embodiment, the first portion

114

and second portion

116

are at least partially formed of an insulating material such as those materials having a first higher dielectric constant (K

1

) previously discussed for the switch assembly

10

of FIG.

1

. The third portion

118

and the fourth portion

120

are at least partially formed of a conductive material such as those materials having a second lower dielectric constant (K

2

) previously discussed for the switch assembly

10

of FIG.

1

. The first portion

114

and second portion

116

can be attached to the third portion

118

and fourth portion

120

in a variety of configurations to form the switching member

102

. Preferably, the insulating and conductive materials are respectively deposited in layers (

122

,

124

) on the annular portion

40

of the switching member

102

in a manner similar to that previously described for the switching member

12

of FIG.

1

. Each of the first lead

104

, second lead

106

and third lead

108

are elongated metal strips that are generally “S-shaped” and extend between a first end

138

and a second end

140

. However, any number of shapes and configurations can be utilized for the leads in accordance with the present invention.

Furthermore, each of the leads (

104

,

106

,

108

) is placed into contact with the surfaces (

20

,

22

) of the switching member

102

. The leads (

104

,

106

,

108

) can be arranged such that the first end

138

of the first lead

104

and the second lead

106

are in contact with the first surface

20

of the switching member

102

and the first end

138

of the third lead

108

is in contact with the second surface

22

of the switching member

102

.

The MEMS switch assembly

100

can be mounted or installed within an electrical device in a manner substantially similar or identical to the installation of the assembly

10

of

FIG. 1

or by other suitable installation techniques. In operation, the switching member

102

may be selectively rotated such that the third portion

118

and fourth portion

120

can provide a robust electrical connection between the first lead

104

and third lead

108

or between the second lead

106

and third lead

108

such that the first portion

114

and second portion

116

provide a less robust electrical connection between the first lead

104

and third lead

108

and between the second lead

106

and third lead

108

. Rotation of the switching member

102

can be provided by methods and/or apparatus similar to that of the switching member

12

previously described with reference to

FIG. 1

or by other appropriate methods and/or apparatus. The skilled artisan will recognize that by appropriately timing the rotation of the switching member

102

to selectively provide robust electrical connections between the leads (

104

,

106

,

108

), the MEMS switch assembly

100

can provide appropriate switch for TDMA applications, and any other existing or future cellular communication protocol, and future generations thereof. The skilled artisan will further recognize that such timing will depend upon the particular TDMA application.

Although various embodiments of this invention have been shown and described, it shall be understood that variations, modifications and substitutions, as well as rearrangements and combinations of the preceding embodiments can be made by those skilled in the art without departing form the novel spirit and scope of this invention.