Electrical connectors – Preformed panel circuit arrangement – e.g. – pcb – icm – dip,... – Distinct contact secured to panel circuit
Reexamination Certificate
1999-06-07
2001-06-05
Patel, Tulsidas (Department: 2839)
Electrical connectors
Preformed panel circuit arrangement, e.g., pcb, icm, dip,...
Distinct contact secured to panel circuit
C439S074000
Reexamination Certificate
active
06241535
ABSTRACT:
This application is also related to U.S. patent application Ser. No. 08/777,579, entitled “High Density Connector”; Ser. No. 08/778,380, entitled “Method for Manufacturing High Density Connector”; and U.S. patent application Ser. No. 08/778,398, entitled “Contact for Use in an Electrical Connector”, all filed on December 31, 1996. The disclosures of the above identified applications are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electrical connectors and more particularly to high I/O density connectors, having a low mated height.
2. Brief Description of Prior Developments
The drive to reduce the size of electronic equipment, particularly personal portable devices, and to add additional functions to such equipment, has resulted in an ongoing drive for miniaturization of all components, especially electrical connectors. Efforts to miniaturize connectors have included reducing the pitch between terminals in single or double row linear connectors, so that a relatively high number of I/O or other lines can be interconnected by connectors that fit within tightly circumscribed areas on the circuit substrates allotted for receiving connectors. The drive for miniaturization has also been accompanied by a shift in preference to surface mount techniques (SMT) for mounting components on circuit boards. The confluence of the increasing use of SMT and the required fine pitch of linear connectors has resulted in approaching the limits of SMT for high volume, low cost operations. Reducing the pitch of the terminals increases the risk of bridging adjacent solder pads or terminals during reflow of the solder paste.
To satisfy the need for increased I/O density, array connectors have been proposed. Such connectors have a two dimensional array of terminals mounted on an insulative substrate and can provide improved density. However, these connectors present certain difficulties with respect to attachment to the circuit substrates by SMT techniques because the surface mount tails of most, if not all, of the terminals must be beneath the connector body. As a result, the mounting techniques used must be highly reliable because it is difficult to visually inspect the solder connections or repair them, if faulty.
In the mounting of an integrated circuit (IC) on a plastic or ceramic substrate the use of ball grid array (BGA) and other similar packages has become common. In a BGA package, spherical solder balls attached to the IC package are positioned on electrical contact pads of a circuit substrate to which a layer of solder paste has been applied, typically by use of a screen or mask. The unit is then heated to a temperature at which the solder paste and at least a portion or all of the solder ball melt and fuse to an underlying conductive pad formed on the circuit substrate. The IC is thereby connected to the substrate without need of external leads on the IC.
While the use of BGA and similar systems in connecting an IC to a substrate has many advantages, a corresponding means for mounting an electrical connector or similar component on a printed wiring board (PWB) or other substrate has become desirable. It is important for most situations that the substrate-engaging surfaces of the solder balls are coplanar to form a substantially flat mounting surface, so that in the final application the balls will reflow and solder evenly to a planar printed circuit board substrate. Any significant differences in solder coplanarity on a given substrate can cause poor soldering performance when the connector is reflowed onto a printed circuit board. To achieve high soldering reliability, users specify very tight coplanarity requirements, usually on the order of 0.004 to 0.008 inches (or 0.1016 mm to 0.2032 mm). Coplanarity of the solder balls is influenced by the size of the solder ball and its positioning on the connector. The final size of the ball is dependent on the total volume of solder initially available in both the solder paste and the solder balls. In applying solder balls to a connector contact, this consideration presents particular challenges because variations in the volume of the connector contact received within the solder mass affect the potential variability of the size of the solder mass and therefore the coplanarity of the solder balls on the connector along the mounting surface.
Another problem presented in soldering connectors to a substrate is that connectors often have insulative housings which have relatively complex shapes, for example, ones having numerous cavities. Residual stresses in such thermoplastic housings can result from the molding process, from the build up of stress as a result of contact insertion, or a combination of both. These housings may become warped or twisted either initially or upon heating to temperatures necessary in SMT processes, such as temperatures necessary to reflow the solder balls. Such warping or twisting of the housing can cause a dimensional mismatch between the connector assembly and the PWB, resulting in unreliable soldering because the surface mounting elements, such as solder balls, are not sufficiently in contact with the solder paste or close to the PWB prior to soldering. The parent and related applications previously identified are directed to solutions to these design challenges. The drive for reduced connector size relates not only to footprint dimensions but also to mated connector height. As electrical equipment shrinks in size, the necessity arises for stacking circuit boards closer together. This invention concerns high density connectors, particularly low profile connectors for reducing the spacing between stacked circuit boards, and more particularly connectors utilizing ball grid array attachment techniques.
SUMMARY OF THE INVENTION
Electrical connectors according to the present invention provide high I/O density and reduced stacking height.
Mated connector height is reduced by utilization of recessed areas in the mating interface of one connector body for receiving the distal portion of a terminal associated with a mating connector. Reduced mated connector height is also achieved by providing a relief area in the connector body to allow flexure of the lower sections of the contact arms of the contact terminal.
Overall contact length is reduced by extending cantilevered receptacle contact arms beyond a bight in the terminal toward a plug contact having a relatively short retention base. Both the plug and receptacle contact terminals are received in a passage having a retention feature that engages the contact terminal centrally, thereby allowing a maximization of beam length and the achievement of acceptable performance characteristics. Contact terminal retention features may be located at an intermediate location along the length of one or more of the contact arms.
Thermal breaks may be placed in the retention section of the contact terminal. The breaks control solder wicking along the terminal from a mounting surface, where a body of fusible material is formed on the terminal.
Contact terminals may be retained in the connector body by a projection or projections in the terminal retention passage that engage the retention section of the terminal or an opening formed in the retention section of the terminal. This terminal mounting arrangement minimizes the accumulation of stress in the connector body, thereby reducing the tendency of the molded connector body to bow or warp.
REFERENCES:
patent: 2231347 (1941-02-01), Reutter
patent: 2980881 (1961-04-01), McKee
patent: 3320658 (1967-05-01), Bolda et al.
patent: 3719981 (1973-03-01), Steltz
patent: 3838382 (1974-09-01), Sugar
patent: 3864004 (1975-02-01), Friend
patent: 3865462 (1975-02-01), Cobaugh et al.
patent: 3889364 (1975-06-01), Krueger
patent: 4056302 (1977-11-01), Braun et al.
patent: 4097266 (1978-06-01), Takahaski et al.
patent: 4140361 (1979-02-01), Sochor
patent: 4217024 (1980-08-01), Aldridge
patent: 4380518 (1983-04-01), Wydro
patent: 4395086 (1983-07-01), Marsh
patent: 4396140 (1983-08-01),
Houtz Timothy W.
Lemke Timothy A.
Berg Technology Inc.
Hamilla Brian J.
Page M. Richard
Patel Tulsidas
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