Metal fusion bonding – Process – Plural joints
Reexamination Certificate
1999-12-23
2003-08-19
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
Plural joints
C228S212000
Reexamination Certificate
active
06607120
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electrical connectors and, more particularly, to high density electrical connectors utilized to electrically connect electronic devices disposed on two or more printed circuit boards.
2. Description of the Prior Art
Increased integration of electronic devices has created an interconnection problem for printed circuit boards receiving these devices. Specifically, the number of interconnections required to electrically connect together two or more printed circuit boards receiving these electronic devices has exceeded the connection densities of prior art pin-in-socket connectors. Moreover, these prior art pin-in-socket connectors typically have relatively long and unshielded lengths which have uncontrolled impedances resulting in less than desired electrical performance.
A high contact density connector utilizable for electrically connecting together electronic devices received on two or more printed circuit boards and overcoming the foregoing problems is disclosed in an article entitled “A High Density Edge Connector” by J. Campbell et al., Copyright 1995 IEEE. This article discloses a flex circuit formed of a 2 mil thick polyamide film having 3 mil wide copper lines plated onto one side thereof and 25 mil round contact pads plated on the side of the film opposite the circuit lines and along both edges of the film. 4 mil diameter plated through-holes, or vias, extend between the contact pads on one side of the film and the circuit lines on the other side. Palladium dendrites, or spires, are electro-deposited on surfaces of each contact pad. These dendrites straddle dust or fibers and puncture oils or films present on each contact pad prior to connector mating and produce on each contact pad a multitude of conductive connections. The connector includes a molded plastic force block to which elastomeric cylinders are molded. These cylinders act as springs which provide force, when compressed during assembly, to make and maintain an electrical connection between the contact pads on the film and the pads on a printed circuit board. One cylinder is provided for each contact and compensates for any variation in planarity and tolerance accumulation. Conical alignment pins are utilized to mate alignment holes in the flex circuit with alignment holes in the printed circuit board during assembly, thereby ensuring proper registration between the contact pads on the film and the pads on the printed circuit board.
Another flexible circuit connector for connecting a daughter card and a mother board is disclosed in an article entitled “A High Density Pad-On-Pad Connector Utilizing A Flexible Circuit” by R. S. Pokrzywa, Copyright 1993 IEEE. This connector utilizes a two-sided flex circuit having plated, spherical contacts contacting flat printed circuit pads on the daughter card and on the mother board. The spherical contacts on the flex circuit are 5 mils in diameter and have a copper base metal overplated with nickel and gold. Alignment pins are utilized to align the flex circuit, the daughter card and the mother board so that each spherical contact mates with a desired printed circuit pad. Precipitation hardened stainless steel curved beams provide contact force for reliable connection between the spherical contacts and the printed circuit pads. During actuation, the curved beam is flattened to produce a uniform load across the contact area. An elastomeric pad is positioned between the beam and the contact area to accommodate local discrepancies in load across the contact area and to focus the connector forces. In one embodiment, the elastomeric pad has a plurality of elastomeric cylinders utilized to back-up the spherical contacts. In another embodiment, where size does not permit molding individual cylinders for each spherical contact, an elastomeric rib is utilized to back a row of spherical contacts.
A problem with spherical contact pads and electro-deposited dendrites on contact pads is that they inconsistently break through contaminants, such as oxides, films or foreign materials, that may be present thereon or on the contact pad of a printed circuit board. Hence, inadequate electrical contact or, in some instances, no electrical contact is made between the contact pad of the flexible circuit and the contact pad of the printed circuit board. Moreover, the formation of a geometric surface such as dendrites or spheres on the contacts of the flexible circuit increases the cost of such connectors.
Currently available flexible circuits are expensive to manufacture and must be designed for specific applications. What is desired is a flexible electrical connector device that includes a compression means, yet is adaptable to different applications and is inexpensive to manufacture.
It is therefore an object the present invention to provide a flexible circuit compressor connector system that includes a compression assembly device which overcomes these drawbacks of the prior art connectors. It is a further object of the present invention to provide a flexible circuit compression connector system contact that promotes electrical contact with conductive pads of a printed circuit board tailored to specific applications. It is an object of the present invention to provide a method for making a flexible circuit compression connector system that utilizes a resilient compression assembly device to provide the required contact. It is an object of the present invention to provide a method of making a flexible circuit compression connector system that includes a resilient compression assembly that is less costly to manufacture than the prior art flex circuit connectors and is easy to assemble and align.
SUMMARY OF THE INVENTION
Accordingly, we have invented a flexible circuit compression connector system that includes a compression assembly utilized to electrically connect together conductive pads disposed on one or more substrates. The flexible circuit compression connector system includes a flexible insulating substrate having a plurality of predetermined positions of preapplied conductive material and at least one conductive line thereon extending between at least two of the predetermined positions of preapplied conductive material, such as a solder paste. The system also includes a plurality of contacts of preselected configuration forming a matrix which are assembled to the substrate. Each contact has a head and a base secured to the flexible insulating substrate at the predetermined positions of conductive material, thereby forming a contact matrix. The base and head are conductive materials. Each contact in the matrix has a head of preselected configuration extending away from the base and the flexible substrate. Each contact is conductive so as to allow a flow of current through the preapplied conductive material on the substrate and the base through the preselected configuration of the contact. In one configuration, the flexible circuit compression connector system includes a flexible substrate having a plurality of conductive holes therein and at least one conductive line thereon extending between at least two of the conductive holes. The flexible circuit compression connector system also includes a plurality of contacts. Each contact includes a base and a head that extends away from the base. Optionally the base may include a post that extends away from the base in a direction opposite the head. The base or the optional post of each contact is secured in one of the plurality of conductive holes.
A compression mat is positioned on the side of the flexible substrate opposite the heads of the plurality of contacts. The compression mat includes a plurality of resilient cylinders extending away from a resilient base. Each resilient cylinder has a distal end alignable with each one of the plurality of contacts, but on the side of the flexible substrate opposite the contact heads.
In assembling the contacts to the flexible substrate, a transfer film is utilized to transfer the plurality of contacts to the flexible substra
Adams, Jr. Grant R.
Neidich Douglas A.
Dunn Tom
InterCon Systems, Inc.
Johnson Jonathan
Maria Carmen Santa
McNees Wallace & Nurick LLC
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