Joints and connections – Biased catch or latch
Reexamination Certificate
2000-08-21
2003-05-13
Browne, Lynne H. (Department: 3679)
Joints and connections
Biased catch or latch
C403S329000, C024S625000, C024S453000
Reexamination Certificate
active
06561725
ABSTRACT:
TECHNICAL FIELD
The present invention relates in general to mechanisms for coupling two components, and in specific to pressure fitting receptacles for coupling microcomponents.
BACKGROUND
Extraordinary advances are being made in micromechanical devices and microelectronic devices. Further, advances are being made in MicroElectroMechanical (“MEMs”) devices, which comprise integrated micromechanical and microelectronic devices. The terms “microcomponent” and “microdevice” will be used herein generically to encompass microelectronic components, micromechanical components, as well as MEMs components. A need exists in the prior art for a mechanism for coupling microcomponents. For example, a need exists for some type of mechanical connector that provides either a permanent mechanical coupling or a temporary coupling between two or more microcomponents.
Generally, microcomponent devices are devices having a size below one millimeter by one millimeter. Although, microcomponents as large as one centimeter by one centimeter have been provided in the prior art. Moreover, microcomponents may be smaller than one millimeter by one millimeter in size. Furthermore, techniques for fabricating microcomponents typically produce such microcomponents having a minimum feature size of approximately one micron. Although, such microcomponents may be implemented with a minimum feature size of greater or less than one micron.
Various types of coupling mechanisms are well known for large scale assembly. For example, mechanisms such as screws, bolts, rivets, snap connectors, clamps, and a variety of other types of coupling mechanisms are well known and commonly used for coupling large scale components. However, such coupling mechanisms for large scale components are very difficult to implement on the small scale necessary for coupling microcomponents. That is, many large scale coupling mechanisms are unacceptable and are not easily adaptable for coupling microcomponents.
Microcomponents, such as MEMs, are generally fabricated as two dimensional (“2-D”) components. That is, microcomponents generally have a defined 2-D shape (e.g., defined X dimension and Y dimension), but the third dimension (e.g., the Z dimension) is generally set for the entire part. Limited control over the Z dimension may be achieved by using multiple layers in microcomponent designs. Although, any given layer of the microcomponent is a given thickness. Thus, a more desirable method to alter the Z dimension, is to combine microcomponent parts together.
One prior art technique commonly used for assembling microcomponents, such as MEMs, is serial microassembly, which may also be referred to as “pick and place” assembly. With serial microassembly, each device is assembled together one component at a time, in a serial fashion. For example, if a device is formed by combining two microcomponents together, a placing mechanism is used to pick up one of the two microcomponents and place it on a desired location of the other microcomponent. While such a serial microassembly technique using pick and place operations initially appears to be a simple technique, when working with microcomponents, such pick and place operations are very complex. For microassembly, the relative importance of the forces that operate is very different from that in the macro world. For example, gravity is usually negligible, while surface adhesion and electrostatic forces dominate. (See e.g.,
A survey of sticking effects for micro parts handling
, by R. S. Fearing, IEEE/RSJ Int. Workshop on Intelligent Robots and Systems, 1995;
Hexsil tweezers for teleoperated microassembly
, by C. G. Keller and R.T. Howe, IEEE Micro Electro Mechanical Systems Workshop, 1997, pp. 72-77; and
Microassembly Technologies for MEMS
, by Micheal B. Cohn, Karl F. Böhringer, J. Mark Noworolski, Angad Singh, Chris G. Keller, Ken Y. Goldberg, and Roger T. Howe). Due to scaling effects, forces that are insignificant at the macro scale become dominant at the micro scale (and vice versa). For example, when parts to be handled are less than one millimeter in size, adhesive forces between a gripper (e.g., micro-tweezers) and a microcomponent can be significant compared to gravitational forces. These adhesive forces arise primarily from surface tension, van der Waals, and electrostatic attractions and can be a fundamental limitation to handling of microcomponents. While it is possible to fabricate miniature versions of conventional robot grippers in the prior art, overcoming adhesion effects for such small-scale components has been a recognized problem.
Often in attempting to place a microcomponent in a desired location, the component will “stick” or adhere to the placing mechanism due to the aforementioned surface adhesion forces present in microassembly, making it very difficult to place the component in a desired location. (See e.g.,
Microfabricated High Aspect Ratio Silicon Flexures
, Chris Keller, 1998). For example, small-scale “tweezers” (or other types of “grippers”) are used to perform such pick and place operations of serial microassembly, and often a microcomponent will adhere to the tweezers rather than the desired location, making placement of the microcomponent very difficult. It has been recognized in the prior art that to grip microcomponents and then attach them to the workpiece in the desired orientation, it is essential that a hierarchy of adhesive forces be established. For instance, electrostatic forces due to surface charges or ions in the ambient must be minimized. Adhesion of the micropart to the unclamped gripper surfaces (with zero applied force) should be less than the adhesion of the micropart to the substrate, to allow precise positioning of the part in the gripper.
Accordingly, unconventional approaches have been proposed for performing the pick and place operations. For example, Arai and Fukada have built manipulators with heated micro holes. See
A new pick up and release method by heating for micromanipulation
, by F. Arai and T. Fukada, IEEE Micro Electro Mechanical Systems Workshop, 1997, pp. 383-388). When the holes cool, they act as suction cups whose lower pressure holds appropriately shaped objects in place. Heating of the cavities increases the pressure and causes the objects to detach from the manipulator. Alternatively, some type of external adhesive (e.g., a type of liquid “glue”) may be utilized to enable the microcomponent to be placed in a desired location. That is, because the components themselves provide no mechanism for coupling, an external adhesive may be required to overcome the adhesive force between the component and the placing mechanism (e.g., tweezers). For example, the target spot on the workpiece may have a surface coating that provides sufficiently strong adhesion to exceed that between the micropart and the unclamped gripper.
Another prior art technique commonly used for assembling microcomponents, such as MEMs, is parallel microassembly. In parallel microassembly, microcomponents of one wafer are coupled to microcomponents of another wafer simultaneously in a single step. For example, the above pick and place operations may be performed on an entire wafer, such that one wafer is picked up and placed onto another wafer, thereby coupling the microcomponents of one wafer with the microcomponents of the other wafer. Therefore, parallel assembly involves the simultaneous precise organization of an ensemble of microcomponents. This can be achieved by microstructure transfer between aligned wafers or arrays of binding sites that trap an initially random collection of parts. Binding sites can be micromachined cavities or electrostatic traps; short-range attractive forces and random agitation of the parts serve to fill the sites.
Parallel microassembly techniques may be categorized as either “deterministic” or “stochastic,” depending on whether the microcomponents are initially organized. There are two general approaches to parallel microassembly in the prior art, one based on the massively parallel transfer between wafers of arrays of microcom
Ellis Matthew D.
Skidmore George D.
Browne Lynne H.
Cottingham John
Fulbright & Jaworski L.L.P.
Zyvex Corporation
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