Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-04-30
2001-07-10
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S842000, C029S845000, C029S832000, C029S837000, C029S839000, C029S840000, C029S423000
Reexamination Certificate
active
06256879
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 polyimide 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 dendrites on the contacts of the flexible circuit increases the cost of such connectors.
It is therefore an object the present invention to provide a connector which overcomes these drawbacks of the prior art connectors. It is an object of the present invention to provide a compression connector contact that promotes electrical contact with a conductive pad of a printed circuit board. It is an object of the present invention to provide a method for making a connector that utilizes the provided compression connector contact. It is an object of the present invention to provide a method of making a flexible circuit connector that is less costly to manufacture than the prior art flex circuit connectors.
SUMMARY OF THE INVENTION
Accordingly, we have invented a compression connector utilized to electrically connect together conductive pads disposed on one or more substrates. The compression connector includes a flexible substrate having a plurality of conductive through-holes therein and at least one conductive line thereon extending between at least two of the conductive through-holes. The compression connector also includes a plurality of contacts. Each contact has a post connected to a base of a crown-shaped head having a plurality of projections around the periphery of the base that extend away from the base in a direction opposite the post. The post of each contact is secured in one of the plurality of conductive through-holes.
A compression mat can be positioned on the side of the flexible substrate opposite the crown-shaped heads of the plurality of contacts. The compression mat can include a plurality of resilient cylinders extending away from a resilient base. Each resilient cylinder can have a distal end alignable in registration with a distal end of the post of one of the plurality of contacts secured in one of the plurality of conductive through-holes.
A transfer film can be utilized to transfer the plurality of contacts to the flexible substrate prior to securing each post in one of the plurality of conductive through-holes. The transfer film preferably has a plurality of elastically deformable receiving apertures which receive and secure the crown-shaped heads of the plurality of contacts.
The compression connector can also include a rigid substrate, such as a printed circuit board, which has a plurality of the conductive pads on a surface thereof and at least one conductive line connected to at least one of the conductive pads. The rigid substrate and the flexible substrate are alignable so that at least one projection of each contact on the flexible substrate is aligned in registration with one of the conductive pads on the surface of the rigid substrate.
A compression fitting can be positionable adjacent the resilient base of the compression mat. The compression fitting forces together at least one projection of each contact and the conductive pad in registration therewith. Each resilient column of the compression mat contacts the distal end of a post of a contact and functions as the spring when compressed to make and maintain good electrical connection between the projection and the conductive pad.
Preferably, a plurality of alignment holes in each of the flexible substrate, the rigid substrate and the compression fitting co-acts with a like plurality of alignment pins to align the flexible substrate, the rigid substrate and the compression fitting so that the heads of the plurality of contacts are in registration with the plurality of contact pads. Each alignment pin is preferably a bolt having a threaded end adapted to mate with a threaded nut.
We have invented a compression connector contact that includes a crown-shaped head h
Adams, Jr. Grant R.
Neidich Douglas A.
Chang Rick Kiltae
InterCon Systems, Inc.
Young Lee
LandOfFree
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