Channel plates for liquid metal micro switches (LIMMS) can be made by sandblasting channels into glass plates, and then selectively metallizing regions of the channels to make them wettable by mercury or other liquid metals. One problem with the current state of the art, however, is that the feature tolerances of channels produced by sandblasting are sometimes unacceptable (e.g., variances in channel width on the order of ±20% are sometimes encountered). Such variances complicate the construction and assembly of switch components, and also place limits on a switch's size (i.e., there comes a point where the expected variance in a feature's size overtakes the size of the feature itself).
One aspect of the invention is embodied in a switch comprising a channel plate and a switching fluid. The channel plate defines at least a portion of a number of cavities, a first cavity of which is defined by an ultrasonically milled channel in the channel plate. The switching fluid is held within one or more of the cavities, and is movable between at least first and second switch states in response to forces that are applied to the switching fluid.
Another aspect of the invention is embodied in a method for making a switch. The method comprises 1) ultrasonically milling at least one feature into a channel plate, and 2) aligning the at least one feature cut in the channel plate with at least one feature on a substrate and sealing at least a switching fluid between the channel plate and the substrate.
Other embodiments of the invention are also disclosed.
Illustrative embodiments of the invention are illustrated in the drawings, in which:
When sandblasting channels into a glass plate, there are limits on the feature tolerances of the channels. For example, when sandblasting a channel having a width measured in tenths of millimeters (using, for example, a ZERO automated blasting machine manufactured by Clemco Industries Corporation of Washington, Mo., USA), variances in channel width on the order of ±20% are sometimes encountered. Large variances in channel length and depth are also encountered. Such variances complicate the construction and assembly of liquid metal micro switch (LIMMS) components. For example, channel variations within and between glass channel plate wafers require the dispensing of precise, but varying, amounts of liquid metal for each channel plate. Channel feature variations also place a limit on the sizes of LIMMS (i.e., there comes a point where the expected variance in a feature's size overtakes the size of the feature itself).
In an attempt to remedy some or all of the above problems, switches with ultrasonically milled channel plates, and methods for making same, are disclosed herein. It should be noted, however, that the switches and methods disclosed may be suited to solving other problems, either now known or that will arise in the future.
When channels are ultrasonically milled in a channel plate, variances in channel width for channels measured in tenths of millimeters (or smaller) can be reduced to about ±15% using the methods and apparatus disclosed herein.
Another advantage to ultrasonic milling is that channel features of varying depth can be formed at the same time (i.e., in parallel), whereas channel plate features of varying depth must be formed serially when they are sandblasted. As a result, the ultrasonic milling of channel features increases manufacturing throughput.
It is envisioned that more or fewer channels may be formed in a channel plate, depending on the configuration of the switch in which the channel plate is to be used. For example, and as will become more clear after reading the following descriptions of various switches, the pair of actuating fluid channels 102, 106 and pair of connecting channels 108, 110 disclosed in the preceding paragraph may be replaced by a single actuating fluid channel and single connecting channel.
Although it is possible to ultrasonically mill all of a channel plate's features 102-110, it may be desirable to laser cut those features 108, 110 that are smaller than a predetermined size (as well as those that need to be formed within smaller tolerance limits than are achievable through ultrasonic milling). To this end,
If the channel plate 100 is formed of glass, ceramic, or polymer, the channel plate 100 may, by way of example, be cut with a YAG laser. An example of a YAG laser is the Nd-YAG laser cutting system manufactured by Enlight Technologies, Inc. of Branchburg, N.J., USA.
As previously discussed, ultrasonically milling features 102-106 in a channel plate 100 is advantageous in that ultrasonic milling machines are relatively fast, and it is possible to mill more than one feature in a single pass (even if the features are of varying depths). Feature tolerances provided by ultrasonic milling are on the order of ±15%. Laser cutting, on the other hand, can reduce feature tolerances to ±3%. Thus, when only minor feature variances can be tolerated, laser cutting may be preferred over milling. It should be noted, however, that the above recited feature tolerances are subject to variance depending on the machine that is used, and the size of the feature to be formed.
In one embodiment of the invention, larger channel plate features (e.g., features 102-106 in
In one embodiment of the switch 500, the forces applied to the switching fluid 518 result from pressure changes in the actuating fluid 520. The pressure changes in the actuating fluid 520 impart pressure changes to the switching fluid 518, and thereby cause the switching fluid 518 to change form, move, part, etc. In
By way of example, pressure changes in the actuating fluid 520 may be achieved by means of heating the actuating fluid 520, or by means of piezoelectric pumping. The former is described in U.S. Pat. No. 6,323,447 of Kondoh et al. entitled “Electrical Contact Breaker Switch, Integrated Electrical Contact Breaker Switch, and Electrical Contact Switching Method”, which is hereby incorporated by reference for all that it discloses. The latter is described in U.S. patent application Ser. No. 10/137,691 of Marvin Glenn Wong filed May 2, 2002 and entitled “A Piezoelectrically Actuated Liquid Metal Switch”, which is also incorporated by reference for all that it discloses. Although the above referenced patent and patent application disclose the movement of a switching fluid by means of dual push/pull actuating fluid cavities, a single push/pull actuating fluid cavity might suffice if significant enough push/pull pressure changes could be imparted to a switching fluid from such a cavity. In such an arrangement, the channel plate for the switch could be constructed as disclosed herein.
The channel plate 502 of the switch 500 may have a plurality of channels 102-110 formed therein, as illustrated in
A second channel (or channels) may be formed in the channel plate 502 so as to define at least a portion of the one or more cavities 506, 510 that hold the actuating fluid 520. If these channels are sized similarly to the actuating fluid channels 102, 106 illustrated in
A third channel (or channels) may be formed in the channel plate 502 so as to define at least a portion of one or more cavities that connect the cavities 506-510 holding the switching and actuating fluids 518, 520. If these channels are sized similarly to the connecting channels 108, 110 illustrated in
Additional details concerning the construction and operation of a switch such as that which is illustrated in
Forces may be applied to the switching and actuating fluids 618, 620 in the same manner that they are applied to the switching and actuating fluids 518, 520 in FIG. 5.
The channel plate 602 of the switch 600 may have a plurality of channels 102-110 formed therein, as illustrated in
A second channel (or channels) may be laser cut into the channel plate 602 so as to define at least a portion of the one or more cavities 606, 610 that hold the actuating fluid 620. If these channels are sized similarly to the actuating fluid channels 102, 106 illustrated in
A third channel (or channels) may be laser cut into the channel plate 602 so as to define at least a portion of one or more cavities that connect the cavities 606-610 holding the switching and actuating fluids 618, 620. If these channels are sized similarly to the connecting channels 108, 110 illustrated in
Additional details concerning the construction and operation of a switch such as that which is illustrated in
A channel plate of the type disclosed in
An exemplary method 700 for making a fluid-based switch is illustrated in FIG. 7. The method 700 commences with the ultrasonic milling 702 of at least one feature in a channel plate. Optionally, portions of the channel plate may then be metallized (e.g., via sputtering or evaporating through a shadow mask, or via etching through a photoresist). Finally, features formed in the channel plate are aligned with features formed on a substrate, and at least a switching fluid (and possibly an actuating fluid) is sealed 704 between the channel plate and a substrate.
One way to seal a switching fluid between a channel plate and a substrate is by means of an adhesive applied to the channel plate.
Although
While illustrative and presently preferred embodiments of the invention have been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed, and that the appended claims are intended to be construed to include such variations, except as limited by the prior art.
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