1. Field of the Invention
The present invention relates to a ground bus, and more particularly to a ground bus for use with an electrical connector and having a plurality of fingers arranged so as to keep adequate spacing between terminal portions of the signal contacts of the connector.
2. Description of Related Art
There are commonly numerous electrical connectors available from the market and which are mounted to a printed circuit board (PCB) of an electronic device for implementing different functions. In order to meet the needs of the trend toward miniaturizaiton, the overall size of the electronic device becomes smaller and smaller. Consequently, a printed circuit board mounted within the device becomes small as well. Conversely, while the dimensions of the device decrease, the functions of the device are often increasing. As such, there is a need to install more and more connectors within a limited area of the printed circuit board. In order to mount more and more connectors on the printed circuit board without increasing the surface area, the dimension of the connector must be reduced. This means the terminal pitch within the connector has to be reduced as well. As such, a high-density connector is required.
In the early stages of the progression toward high density placement of the connectors, through-hole mounting technology was used. Mounting portions of the terminals were placed in through holes of the circuit board and held in place by soldering or some type of mechanical engagement of the pin with sidewalls of the through hole. As the need for high density of the connector increased, the number of through holes required also increased. However, since the diameter of the through holes is relatively large, only a limited number of through holes could be provided in a given area. Therefore, through-hole technology could not meet the requirement for high density applications.
In order to provide for a higher density of connectors on the board, surface mount technology has been utilized. Some surface mount connectors can be referred to U.S. Pat. No. 5,813,871 issued to Grabbe et al. on Sep. 29, 1998 and U.S. Pat. No. 5,860,814 issued to Akama et al. on Jan. 19, 1999. Because no through holes are required, conductive pads on the printed circuit board can be closely spaced, thereby allowing a connector with condensed terminals to be mounted in an area of the board which would be impossible for a through-hole version.
As the progression toward higher density continues, it has become imperative that every possible area of the printed circuit board be effectively utilized. A straddle mount connector located on an edge of the printed circuit board is then developed to occupy a minimal board area. Additionally, with the trend of high speed signal transmission, the straddle mount connector generally employs a ground bus to provide a ground reference to signal contacts for improved signal integrity at higher speeds. Such a straddle mount connector can be referred to U.S. Pat. No. 5,320,541 issued to Korsunsky et al. on Jun. 14, 1994, U.S. Pat. No. 5,199,885 issued to Korsunsky et al. on Apr. 6, 1993 and U.S. Pat. No. 5,120,232 issued to Korsunsky on Jun. 9, 1992.
Referring to FIG. 5 of U.S. Pat. No. 5,199,885, a straddle mount connector is disclosed therein and comprises an insulating housing having a mating surface and an opposite mounting surface. The housing defines a recess in the mating surface for receiving a mating connector therein, two rows of cavities extending from the mounting surface to the recess and a slot extending from the recess to proximate the mounting surface along a longitudinal direction thereof. A plurality of signal contacts is inserted into the cavities from the mounting surface of the housing with terminal portions extending out of the mounting surface so as to mount the connector to an edge of a printed circuit board in a straddle. A ground bus is inserted into the slot from the mating surface of the housing with solder tails penetrating through the mounting surface. When the terminal portions of the signal contacts slide over opposite side surfaces of the printed circuit board, the solder tails of the ground bus are inserted into plated openings in an edge surface of the printed circuit board, thereby establishing an electrical connection between the ground bus and the printed circuit board.
It is quite difficult to form the opening in the edge surface of the printed circuit board, thereby complicating the manufacturing process.
U.S. Pat. No. 6,231,355 issued to Trammel et al. discloses a straddle mount connector with the ground bus also straddle mounted on the printed circuit board for addressing to the problem encountered by the '885 patent. However, in order to minimize the PCB used for signal contacts, the lead-in of the signal terminal portions for placement on the edge of the PCB is abbreviated. This leads to a potential stubbing condition upon placement, particularly because the leads are proportioned to be flexible. This flexibility also results in less accurate side-to-side placement of the leads on pre-soldered pads of the printed circuit board. In addition, the ground bus does not provide a robust lead-in for receiving the inserted printed circuit board. Trammel further discloses other solutions to the captioned connector, such as disclosed in U.S. Pat. Nos. 6,296,496 and 6,419,502 which are believed relevant to the present invention.
Further, the contact pitch of the high density connector is so small so as to create a possibility of “arcing” between the terminal portions of the signal contacts and adjacent solder tails of the ground bus. In order to avoid and prevent this shortcoming, the terminal portions of the signal contacts and the solder tails of the ground bus are kept at a safe distance. However, when the solder tail of the ground bus is cut short to keep this safe distance relative to the terminal portion of the signal contact, the end of the solder tail of the ground bus is almost in alignment with the inserted printed circuit board as the lead-in is cut-off. This will create a great difficulty during the assembly because a front edge of the printed circuit board may easily abut against the solder tails unless the printed circuit board is kept completely and perfectly horizontally with respect to a plane defined by the solder tails. This no doubt increases the difficulty of assembly.
In addition, when the pitch of the contact of the connector becomes smaller and smaller, keeping the terminal portions of the contact in accurate spacing at all times, including handling and delivery, is a challenge to the manufacturer. If the pitch of the contacts is varied or displaced during handling and delivery, it will be impossible to achieve an accurate alignment between the terminal portions and the conductive pads of the PCB on which the connector is mounted. How to keep those terminal portions of the connector accurately aligned with the conductive pads of the printed circuit board even during the assembly is really a challenge to the manufacturer.
Hence, an improved straddle mount connector is required to overcome the disadvantages of the related art.