Electrical connectors – Preformed panel circuit arrangement – e.g. – pcb – icm – dip,... – With provision to conduct electricity from panel circuit to...
Reexamination Certificate
1999-10-26
2002-06-25
Sircus, Brian (Department: 2839)
Electrical connectors
Preformed panel circuit arrangement, e.g., pcb, icm, dip,...
With provision to conduct electricity from panel circuit to...
Reexamination Certificate
active
06409521
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a solderless connector with multiple modes of compliance and to a replaceable chip module utilizing the present connector for electrically connecting one or more first circuit members to a second circuit member.
BACKGROUND OF THE INVENTION
The current trend in connector design for those connectors utilized in the computer field is to provide both high density and high reliability connectors between various circuit devices. High reliability for such connections is essential due to potential system failure caused by improper connections of devices. Further, to assure effective repair, upgrade, testing and/or replacement of various components, such as connectors, cards, chips, boards, and modules, it is highly desirable that such connections be separable and reconnectable in the final product.
Pin-type connectors soldered into plated through holes or vias are among the most commonly used in the industry today. Pins on the connector body are inserted through plated holes or vias on a printed circuit board and soldered in place using conventional means. Another connector or a packaged semiconductor device is then inserted and retained by the connector body by mechanical interference or friction. The tin lead alloy solder and associated chemicals used throughout the process of soldering these connectors to the printed circuit board have come under increased scrutiny due to their environmental impact. The plastic housings of these connectors undergo a significant amount of thermal activity during the soldering process, which stresses the component and threatens reliability.
The soldered contacts on the connector body are typically the means of supporting the device being interfaced by the connector and are subject to fatigue, stress deformation, solder bridging, and co-planarity errors, potentially causing premature failure or loss of continuity. In particular, as the mating connector or semiconductor device is inserted and removed from the present connector, the elastic limit on the contacts soldered to the circuit board may be exceeded causing a loss of continuity. These connectors are typically not reliable for more than a few insertions and removals of devices. These devices also have a relatively long electrical length that can degrade system performance, especially for high frequency or low power components. The pitch or separation between adjacent device leads that can be produced using these connectors is also limited due to the risk of shorting.
Another electrical interconnection method is known as wire bonding, which involves the mechanical or thermal compression of a soft metal wire, such as gold, from one circuit to another. Such bonding, however, does not lend itself readily to high density connections because of possible wire breakage and accompanying mechanical difficulties in wire handling.
An alternate electrical interconnection technique involves placement of solder balls or the like between respective circuit elements. The solder is reflowed to form the electrical interconnection. While this technique has proven successful in providing high density interconnections for various structures, this technique does not allow facile separation and subsequent reconnection of the circuit members.
An elastomer having a plurality of conductive paths has also been used as an interconnection device. The conductive elements embedded in the elastomeric sheet provide an electrical connection between two opposing terminals brought into contact with the elastomeric sheet. The elastomeric material that supports the conductive elements compresses during usage to allow some movement of the conductive elements. Such elastomeric connectors require a relatively high force per contact to achieve adequate electrical connection, exacerbating non-planarity between mating surfaces. Location of the conductive elements is generally not controllable. Elastomeric connectors may also exhibit a relatively high electrical resistance through the interconnection between the associated circuit elements. The interconnection with the circuit elements can be sensitive to dust, debris, oxidation, temperature fluctuations, vibration, and other environmental elements that may adversely affect the connection.
The problems associated with connector design are multiplied when multiple integrated circuit devices are packaged together in functional groups. The traditional way is to solder the components to a printed circuit board, flex circuit, or ceramic substrate in either a bare die silicon integrated circuit form or packaged form. Multi-chip modules, ball grids, array packaging, and chip scale packaging have evolved to allow multiple integrated circuit devices to be interconnected in a group.
One of the major issues regarding these technologies is the difficulty in soldering the components, while ensuring that reject conditions do not exist. Many of these devices rely on balls of solder attached to the underside of the integrated circuit device which is then reflown to connect with surface mount pads of the printed circuit board, flex circuit, or ceramic substrate. As discussed above, these joints have not been proven to be extremely reliable nor easy to inspect for defects. The process to remove and repair a damaged or defective device is costly and many times results in unusable electronic components and damage to other components in the functional group.
Multi-chip modules have had slow acceptance in the industry due to the lack of large scale known good die for integrated circuits that have been tested and burned-in at the silicon level. These dies are then mounted to a substrate which interconnect several components. As the number of devices increases, the probability of failure increases dramatically. With the chance of one device failing in some way and effective means of repairing or replacing currently unavailable, yield rates have been low and the manufacturing costs high.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to a solderless electrical connector in which the contact members provide at least two modes of compliance. The first mode of compliance is determined primarily by the resilience of the encapsulating material. The contact members rotates and/or translates within the encapsulating material during the first mode of compliance, although elastic deformation of the contact members may also be factors. The encapsulating material provides a relatively large range of motion at a low force, allowing for the array of contact members to achieve continuity and planarity despite a significant mismatch. Once the encapsulating material between the contact members and a surface of the housing is substantially compressed, further movement is constrained to promote elastic bending of the contact members in the second mode of compliance.
The present multi-mode compliance connector provides a natural coupling and decoupling between devices, the connector housing, and a PCB. Movement of the contact members corrects for lack of co-planarity, provides shock/vibration dampening, and reduces stress at the interface. The housing and contact member geometry and material are designed to primarily to provide the desired deflection mechanism, rather than contact retention. The solderless suspended contact set allows for compression of both contact tips approximately, at same time. The achievable pitch is less than comparable technologies.
The present multi-mode compliance connector leverages existing infrastructure and technology, requiring less capital investment than other technologies. The encapsulation method allows for the use of shielded, controlled impedance contact members or attenuator, rather than just connector members. Since the contact members are accessed from both the top and bottom of the housing, the contact members typically experience less bending than traditional methods that rely on only topside compliance.
The base metal of the contact members substantially defines the second mode of compliance, providing long term conne
Faegre & Benson LLP
Gryphics, Inc.
Le Thanh-Tam
Sircus Brian
LandOfFree
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