Wave transmission lines and networks – Coupling networks – With impedance matching
Reexamination Certificate
1999-08-05
2001-07-24
Lee, Benny (Department: 2817)
Wave transmission lines and networks
Coupling networks
With impedance matching
C361S748000, C361S761000, C361S767000
Reexamination Certificate
active
06265952
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to attaching electrical components to printed circuit boards, and more particularly, to adapters for surface mount devices.
An integrated circuit combines numerous active and passive electrical circuitry elements on a single device called a die or chip. These integrated circuits are interconnected by attaching them to printed circuit boards. Such circuits are inherently small and fragile devices. Thus, they are usually embedded in a substrate called a chip carrier or package before they are attached to the printed circuit board. Protruding from the package are a number of electrical conducting leads. The conducting leads may protrude from the package by extending through the bottom of the package (e.g., pin or pad grid arrays), may be arrayed along two edges of the package (e.g., dual in-line pins), or may fan out from the edges of the package (e.g., gull wing and jay pins).
The wiring on printed circuit boards may include thin metallic strips embedded in an insulating material. These strips interconnect leads from different circuit packages mounted on the same board. For all of the required connections, the boards may have several layers of interconnected wiring. The wiring is used to determine the placement of the integrated circuit packages on the board. Also, the wiring is employed to route electrical signals among the integrated circuits. The leads may connect to the wiring in a variety of ways. One technique includes drilling holes in the board and through the wiring at appropriate locations, inserting the leads through the holes, and making mechanical and electrical attachments among the leads, the wiring, and the holes. Another technique is called surface mount technology (SMT). This method includes arranging contact pads on the surface of the printed circuit board. The pads are used to deliver electrical signals to the leads and to the appropriate embedded wires. Leads may be placed on top of the pads and mechanically and electrically attached.
SMT is widely used for high speed digital communications. Typical packages include plastic leaded chip carriers (PLCC), dual in-line packages (DIP), single in-line packages (SIP), small outline packages (SO), and small outline T-leaded packages (SOT). To test or prototype these type devices, custom device-specific evaluation boards supplied by the manufacturer are required. This is because each device has a different specific footprint. In many cases, a large number of the device-specific evaluation boards are required. As a result, prototyping can be limited. For example, if a certain device-specific evaluation board was not available, an entire prototype procedure may be impeded.
Also, these high speed devices require controlled impedance inputs and outputs that are not easily implemented in a general printed circuit board configuration. Certain commercially available surface-mount to DIP and SIP adapters have been employed. However, these adapters are not suitable for high frequency applications. These adapters have long traces between the device footprint and the pins of the DIP or SIP. This can create excessive noise in the resulting signal, and also, poor performance from the integrated circuit. Additionally, critical components, such as a power supply pin, must be located on the printed circuit board. As a result, long wire traces must be used to interconnect the device to other components in the system. This can also contribute to faulty signal and circuit operation.
SUMMARY OF THE INVENTION
In general, the present invention is directed to a surface mount adapter for a surface mount device that includes a plurality of matched impedance input/output lines for connecting the surface mount device to a plurality of through hole pins. The adapter may be connected to a motherboard or other prototyping board for testing or prototyping the surface mount device.
Accordingly, in one aspect, the adapter includes a printed circuit board having a top layer and bottom layer, and a footprint formed on the top layer of the printed circuit board for receiving the surface mount device. A plurality of impedance matching input/output lines are connected between a plurality of electrical pins of the surface mount device and a plurality of through hole pins attached to the printed circuit board.
Implementations of the invention include one or more of the following. The surface mount device may be an emitter coupled logic device or a high frequency surface mount device. The adapter may include at least one ground plane and at least one power plane. The surface mount device may be connected to the ground plane via an input termination resistor, and may be connected to the power plane by at least one decoupling capacitor. The ground plane may be formed between the top layer and the bottom layer. The input/output pins may be 50 &OHgr; transmission lines. The number of electrical pins may be between 8 and 30. The adapter may further include a clamp and an input termination resistor electrically connected to the through hole pins through the clamp. A decoupling capacitor may also be electrically connected to the through hole pins through the clamp.
In accordance with another aspect, the adapter may include a printed circuit board having a top layer and a bottom layer, and a footprint formed on the top layer of the printed circuit board for receiving the surface mount device. A plurality of vias may be formed in the printed circuit board for receiving a plurality of electrical pins of the surface mount device. A plurality of impedance matching input/output lines may be connected between a plurality of pads formed on the bottom layer and the electrical pins through the vias. A plurality of series components or shunt components may be connected between the pads and a plurality of through hole pins attached to the printed circuit board.
Implementations of the invention include one or more of the following. The surface mount device may be a radio frequency device. The adapter may include a plurality of connecting strips for forming a filter network. The series components may be coupling capacitors or jumpers. The adapter may be connected to a motherboard or a prototyping board.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
REFERENCES:
patent: 4604678 (1986-08-01), Hagner
patent: 5151039 (1992-09-01), Murphy
patent: 5173767 (1992-12-01), Lange et al.
patent: 5424693 (1995-06-01), Lin
patent: 5572409 (1996-11-01), Nathan et al.
patent: 5612657 (1997-03-01), Kledzik
patent: 6090647 (2000-07-01), Grass
Fish & Richardson PC
Jones Stephen E.
Lee Benny
Pulse Research Labs
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