Micromachined silicon beam interconnect

Details Micromachined silicon beam interconnect Micromachined silicon beam interconnect

1999-08-23

2002-03-26

Sircus, Brian (Department: 2839)

Electrical connectors

Preformed panel circuit arrangement, e.g., pcb, icm, dip,...

With mating connector which receives panel circuit edge

C439S065000, C439S637000

Reexamination Certificate

active

06361327

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to electrical interconnects, and more particularly, to an interconnect structure utilizing silicon cantilever beams that are adapted to be received by a contact terminal of a complementary structure.
BACKGROUND OF THE INVENTION
In recent years, integrated circuits have become increasingly complex. These new complex integrated circuits have created problems for designers because they have a large number of pin-outs requiring a large number of connections to printed circuit boards, etc. In addition, these new complex integrated circuits are operating at ever-increasing clock speeds, which are approaching 1 GHz. Conventional interconnect technologies may not maintain pace with the rapid acceleration in complexity and speed of integrated circuits.
Conventional interconnect technologies complicate the design and manufacturing of electronic equipment such as integrated circuits by requiring such designs to account for component placement, heat generation, power loss, signal propagation delay, cross talk, switching noise and termination problems. Often new interconnect technologies overcome one problem while increasing the negative effects of another. Conventional interconnect technologies provide different approaches to interconnecting electronic components, and include: solder reflow to make permanent, low-ohmic connections; wiping contacts to make temporary, medium-ohmic connections; and filled adhesives to make permanent, medium to high ohmic connections. Each of these technologies has limitations in view of the improvements in electronic components such as integrated circuits.
Solder reflow techniques provide a metallic contact of moderate strength, but require the bonded surfaces and surrounding areas to be subjected to high heat. Thermal stresses induced by solder reflow tend to weaken or damage the components joined and therefore results in higher initial and long term failure rates. In addition, solder bonds are easily broken under moderate stress, and if the bonds are not formed under controlled conditions, they are subject to producing poor connections having high resistance and low mechanical durability.
Wiping action interconnect technology, such as that used by sockets, plugs, needle pins, etc., forms a temporary electrical interconnection to provide for remating of various components and assemblies. A problem with using wiping action technology is the persistent formation of oxides along a contacting surface, which increases contact resistance. In time, these oxides build up causing heat to be generated at the contact surface, causing connection failure and equipment failure. The sockets and connectors used in wiping action technology often use special metals, alloys, and other expensive materials suitable for maintaining a sliding connection. Further limiting these devices is that they often have interfering electrical properties due to their size, orientation on a circuit board, etc., which degrades signal propagation through the interconnect by introducing resistive, capacitive, and inductive components into the signal path. Additionally, wiper interconnects are highly unreliable in environments having excessive vibration, temperature extremes, and/or high levels of contamination exist.
Zero insertion force (ZIF) sockets are an improvement in the wiping action interconnect technology area, but their cost increases significantly as the number pin-outs or connection points increases. This cost increase has made component packages and the connectors used to form an electrical and/or mechanical interface between integrated circuits and assemblies in electronic products the most expensive portion of such products. An additional drawback is that component packages, connectors, sockets, plugs, etc. are also the bulkiest and heaviest portion of such products.
Filled adhesive technology is used to provide a binder and a conductive filling. The adhesives typically utilized are silver or gold. However, these materials are often unsuitable for most interconnect applications because they form medium to high ohmic connections.
Thus, in view of the above, there still remains a need for an improved interconnect structure that allows for higher densities of connection points to electronic equipment, while providing superior electrical performance and being easier to manufacture and produce. The present invention provides such a solution.
SUMMARY OF THE INVENTION
The present invention is directed to an interconnect structure for electronic equipment. According to the present invention, there is provided an interconnect structure adapted to receive an electrical component that includes a dielectric material and a plurality of cantilever beams secured to the dielectric material at a predetermined pitch. The plurality of cantilever beams are deflected by a contact force created when the cantilever beams receive the electrical component in order to place the cantilever beams in mechanical and electrical communication with the electrical component.
According to features of the invention, the cantilever beams maybe made from micromachined silicon and arranged in two generally parallel planes separated by the dielectric material to form a recessed region. A mounting structure having slots may be disposed on the top and bottom of the dielectric material. Each of the cantilever beams has a top surface, a side comprising first and second side surfaces, and a bottom surface. The bottom surface contacts a terminal pad of the electrical component when received by the interconnect structure. The first side surface is formed at a predetermine angle with respect to the top surface. Also, the cantilever beams may be formed having a sloped face at a free end thereof.
According to other features of the invention, design rules are provided to specify various mechanical and electrical constraints that are met to achieve mechanical tolerances and electrical performance as the pitch of the interconnect structure is varied. In particular, the lateral tolerances of the cantilever beams fix a minimum pitch and vertical tolerances of the plurality of cantilever beams fix a spring rate of the cantilever beams.
According to another aspect of the present invention, a method of reducing the pitch between adjacent contacts in an electrical connector is provided which comprises the steps of providing a contact with an extent that defines a volume; adjusting the extent of the contact; and maintaining the volume of the contact. The adjusting step may comprise adjusting the length and the height of the contact while maintaining the width of the contact. The adjusting step may alternately comprise adjusting the length and the width of the contact while maintaining the height of the contact.
According to a further aspect of the present invention, there is provided a method of scaling an electrical connector so as to maintain a generally constant near end cross-talk and characteristic impedance. The method comprises providing a number of contacts, each having a length, a width, and a height that define a volume, the contacts being manufactured to a tolerance; separating the plurality of contacts by a pitch (P); fixing three of the number of contacts, the length, the width, the height, the volume and the tolerance; and adjusting the remaining three of the number of contacts, the length, the width, the height, the volume and the tolerance. The fixing step may comprise fixing the width, the height and the number of contacts and the adjusting step may comprise adjusting the tolerance, the length and the volume.
According to a yet another aspect of the present invention, there is provided an electrical connector system that includes a first electrical connector comprising a contact formed of metalized silicon and a base supporting the contact, and a second electrical connector mateable with the first electrical connector that comprises a contact formed of metalized silicon and a base supporting the contact.
Other features and aspects will be described below.


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