|Monday, 11 December 2006|
Regardless the type and design of a PC board, external signal and power connections must be made. Printed circuit boards, as well as other electronic components, in many instances are electronically joined through connectors. The components are typically interconnected to define a given function through a printed circuit board having contact pads complementary to pads of the components to which printed circuit board is to be joined. A wide variety of electrical connectors are designed for mounting to a printed circuit board. Such connectors typically include a dielectric housing, such as a unitarily molded plastic housing, adapted for mounting to one side of the board. The housing typically includes a front mating face for mating with a complementary connecting device and a rear terminating face from which a plurality of terminals exit the housing for termination to circuit traces on the printed circuit board. The terminals normally include mating portions for mating with the terminals of the complementary connecting device, and terminating or tail portions projecting from the housing for interconnection, as by soldering, to circuit traces on the board or in holes in the board into which the tails are inserted. Circuit board connectors are used for mounting a daughter circuit board to a primary circuit board. The connector includes an elongated insulative housing which forms a slot dimensioned to receive an edge of the daughter circuit board. The daughter circuit board may be, for example, a memory module, interface card, or some other auxiliary circuit card. These connectors may support daughter circuit boards in different planes with respect to the primary circuit board. For example, a connector may support a daughter circuit board in a generally perpendicular orientation in a vertical plane or it may support the daughter board in a parallel orientation in horizontal plane above the primary circuit board. The former connector requires more vertical space than the latter connector, and in view of the trend toward reduction in size of electronic devices, the latter style connector is gaining in popularity because it will reduce the overall height of the electronic component in which it is used. These types of connectors which engage a secondary circuit board and support it in a horizontal plane are often referred to as "low profile" connectors. Flexible printed circuit connectors are widely used in electronic devices such as mobile telephones, keyboards, hard disk drives and fax machines etc. Such kind of FPC connectors comprises a housing, a plurality of terminals received in the housing, and an actuator rotatably mounted on the housing. Each terminal has a bifurcate contact section and a solder tail soldered onto a PCB. One end of an FPC board is inserted into an opening defined in the housing, for engaging the bifurcate contact sections of the terminals. Thus, mechanical and electrical engagement between the PCB and the FPC board is attained.
A typical printed circuit board connector comprises an isolating housing and contact elements which are arranged therein, are preferably formed angled and have a plug-in side, an intermediate portion and a connecting side with contact ends adapted to be mounted at a printed circuit board. Printed circuit boards can be "one sided," in which all of the traces are formed on one side of the dielectric sheet of material. PCBs can also be "two sided," where traces are formed on both sides of the sheet of dielectric material. A single-sided printed-circuit board generally consists of a fiberglass substrate having a component-side and a solder-side. On the solder-side, conducting paths are imprinted or deposited. On the component side, various electrical components are mounted and connected to the conducting paths on the solder-side through strategically located through holes. Printed circuit board zero insertion force connectors serve to connect two printed circuit boards to one another without any expenditure of force or at least without any significant expenditure of force during insertion of the printed circuit board. PCB zero force connectors have the particular feature that their contact elements are arranged on one or more movable parts and can be moved together with them. By moving the parts carrying the contact element, the printed circuit board zero force connector can be brought from an assembly position allowing an printed circuit board to be plugged into, or removed from a connecting position without the contacts touching the printed circuit board. Electrical connectors for printed circuit boards have terminals with a portion often referred to as a "solder tail" extending rearwardly from a contact in an insulating housing for insertion into holes in a printed circuit board. Miniaturization of such connectors led to the development of surface mount connectors having terminals with solder tails configured for positioning against and connection to conductive pads or circuit traces on the surface of the board. The solder tails mounted to a surface of the board is the reason for terming this type of connector "surface mount". A wide variety of surface mount connectors have been developed, some including socket-type terminals with receptacle contacts for mating with pins of a complementary mating male connector, and others containing terminal pin headers which mount a plurality of terminals with contact pins projecting therefrom for mating with socket-type terminals. Surface mount electrical connectors typically employ a number of electrical contacts mounted in an insulative connector housing. Typically in a surface mount terminal connector of either the socket or pin header terminal type, the receptacle contacts or contact pins typically project from the connector in spaced apart horizontal rows parallel to the board, whereas all the solder tails are in a single horizontal plane for connection to the planar array of conductive pads on the one side of the board. The solder tails of the terminals are typically arranged in a single row or coplanar rows for automated interconnection to the conductive pads on the circuit board. In fact, automated assembly is a critical design consideration with respect to surface mount connectors. Surface mount electrical connectors are, however, available for use on printed circuit boards that use only surface mount devices.
Some printed circuit board mounted electrical connectors are designed for mounting at an edge of the board. Such printed circuit boards have a number of surface pads located along an edge of the board. The surface pads are connected to the integrated circuit packages by routing layers of the printed circuit board. The edge of the board and surface pads are plugged into a corresponding connector within a computer assembly. The integrated circuits are coupled to a motherboard of the assembly through the routing layers, surface pads and connector. The connectors are commonly referred to as edge card connectors or card edge connectors. Edge card connectors electrically connect a daughter board to a mother board within the limited space of a computer or other like electronic device. An edge connector receives a printed circuit board having a mating edge and a plurality of contact pads adjacent the edge. Such edge connectors have an elongate housing defining an elongate receptacle or slot for receiving the mating edge of the printed circuit board. Usually the connector includes a housing provided with contacts which effect an electrical connection between the circuits of the connected mother and daughter boards. A plurality of terminals are spaced along one or both sides of the slot for engaging the contact pads adjacent the mating edge of the board. In many applications, such edge connectors are mounted on a second printed circuit board. The mating edge board or card commonly is called the daughter board, and the board to which the connector is mounted commonly is called the mother board. A typical card-edge connector configuration will have 20 terminals on each side of the PC board. The number of contacts depends upon the number of external board connections required. To mate with a card edge connector, PC boards are generally preformed with a rectangular projecting tab along one side having a width and height selectively sized to fit within the socket of the card-edge connector of a predetermined size. A PC motherboard may include an array of multipurpose card-edge connectors of the same size into which a variety of special purpose circuit boards are inserted, such as a memory card, a modem, etc. Each such special purpose board may have different connection requirements and a different number of contacts.