Electrical connectors – With supporting means for coupling part – Supporting plural – independent coupling parts
Reexamination Certificate
2000-05-09
2001-11-13
Bradley, Paula (Department: 2833)
Electrical connectors
With supporting means for coupling part
Supporting plural, independent coupling parts
C439S079000, C439S701000, C361S809000, C248S224700
Reexamination Certificate
active
06315605
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to electrical connectors for connecting a first circuit substrate, such as a daughter Printed Circuit Board (PCB) to a second circuit substrate, such as a backplane. More particularly, the present invention relates to a stiffener assembly and method for mechanically joining and stiffening one or more electrical connectors on a PCB.
BACKGROUND
Electrical connector pairs are commonly used in electronic equipment. Each pair functions to connect and route electrical signals between different PCBs. A typical connector pair consists of a plug, or header, and a receptacle, each including a plastic housing and multiple contact elements. The complimentary shaped plug and receptacle fit together, such that the electrical contacts of the plug are aligned with the electrical contacts of the receptacle. Each contact is provided with a tail portion that extends beyond the plastic housing to engage, for example, a plated through hole in the PCB. The plug and receptacle are attached to separate PCBs, such that the tail portions of each connector make contact with conductive traces formed on or in each PCB. In this manner, a connector pair completes an electrical circuit between the two PCBs. For instance, these type connectors have been used to electrically connect a daughterboard to another daughterboard, to a backplane board, or to other electrical circuitry. In a typical configuration, the receptacle is connected to the daughterboard while the plug is attached to the backplane.
One early limitation in the use of electrical connectors of this type was in maintaining tolerances for the proper alignment of the contact elements of each connector. This problem has been addressed through the development and use of multiple modules in a single connector. Since each individual module is smaller in size than the entire connector and plastic housing, it is easier to maintain manufacturing tolerances within acceptable limits, thereby ensuring that the plug and receptacle elements fit together properly and that the contacts establish an acceptable electrical connection.
The current United States industry standard for a two part modular connector system for electrically coupling a backplane to a daughter board is set out in specification EIA/IS-64 from the Electronic Industries Association. This specification delineates parameters for 2 mm, two part connectors for use with PCBs and backplanes. The international standard for these two part connectors is set out in IEC 1076-4-001 specification 48B.38.1. Both of these specifications define a free board (daughter board) connector that contains receptacle contacts and a fixed board (backplane or mother board) connector that contains pin contacts. The connector half containing receptacle contacts is commonly referred to as a socket connector, and the connector half containing pin contacts is commonly referred to as a header connector.
The use of stiffeners to help hold the individual connector modules together is known to maintain the correct tolerances and alignment between modules, and to help reduce bowing of the PCB. Alignment problems usually result from a difference in thermal expansion between the materials used in the modules and the PCB. When the assembly is heated during a soldering operation, the thermoplastic housing material of the connector can expand at a faster rate than the PCB material. A typical PCB is made from a composite of fiberglass/epoxy resin and contains copper traces with plated through holes or pads. Built-in residual stresses from the connector manufacturing and assembly processes are released by the heat generated during this soldering process. As a result, the components may not return to their original position after they have cooled down. This can result in misalignment of the connector tails when attached by the soldering process. This misalignment causes the more rigid connector housing to pull on the holes of the PCB through the metal contact tails, flexing the less rigid structure of the PCB to the alignment of the connector assembly. The longer the connector, the more this misalignment effect is compounded. The presence of numerous through holes in the PCB also introduces a less rigid area to the PCB which is more prone to flex during loading. Accordingly, stiffeners have become popular in these types of connector assemblies.
Traditional board stiffeners consist of an angled bar, shell, or U-shaped bar. The board stiffener is typically bolted or screwed to the PCB. In other applications, the stiffener is connected to both the connector and the PCB. Stiffeners are usually made from metallic material. These metal stiffeners have a much stronger stiffness when compared to the plastic housing of the connector or the composite material of the PCB. As a consequence, the stiffener helps to reduce the bowing effect. However, these board stiffeners also have several problems or design disadvantages.
One such problem is the increased assembly cost. Traditional stiffeners are difficult to manufacture in various lengths due to their designs and material, requiring expense retooling in the manufacturing process. In addition, traditional stiffeners do not allow for replacement/repair, or upgrading of an electrical connector on the PCB without complete disassembly and removal of the stiffener from all the connector assemblies.
Accordingly, a need still exists for providing means of connecting together and holding down various connectors, and of providing a means of stiffening the PCB to prevent bowing while still allowing individual connector assemblies to be removed from the PCB and also providing for the manufacture of various length board stiffener assemblies in a cost effective manner.
SUMMARY
The present invention is directed to a printed circuit board (PCB) stiffener, stiffener assembly, and method for mechanically supporting and aligning one or more electrical connectors on a PCB while at the same time stiffening the PCB. This invention solves the need of providing a means of manufacturing various length stiffener assemblies, joining together various connector assemblies, and also of providing the advantage of providing a mechanism for removal of one or more connector assemblies from the PCB without complete disassembly of the stiffener assembly from all the connector assemblies. The invention provides a means of stiffening the PCB to prevent bowing, while at the same time, conserving space or real estate on the PCB. The stiffener assembly also aligns the individual connector modules in a mono-block appearance.
The PCB stiffener includes a two-piece body having a top clamp and a bottom channel. The top clamp includes an inverted L-shaped body having a support leg and an engagement leg. The support leg is constructed to fit within the bottom channel and has a plurality of holes formed in a bottom surface for receiving fasteners to connect the top clamp to the PCB through openings formed in the bottom channel. The engagement leg includes a latch that is constructed to connectively engage a structure on the electrical connector thereby holding the stiffener to the connector.
The bottom channel includes a U-shaped body having a first leg and a second leg connected by a web member. The web member has a mounting surface constructed to mount on an upper surface of the PCB. The web member also includes a plurality of openings formed therein for receiving fasteners. The openings in the web member are constructed to correspond to the holes formed in the support leg of the top clamp. The first leg is adapted to form an alignment structure in conjunction with the latch. The alignment structure connectively engages a structure on the electrical connector thereby holding the stiffener to the connector. The second leg acts in conjunction with the first leg to form a channel. The channel is adapted to receive and support a lower portion of the support leg.
The PCB stiffener assembly includes an electrical connector, a stiffener, and a circuit substrate, such as a printed circuit board (P
Billman Timothy B.
Weaver, Jr. John H.
Bradley Paula
FCI Americas Technology Inc.
Figueroa Felix O.
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
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