1. The Field of the Invention
The present invention relates to PC cards, and more specifically, PC cards for controlling electromagnetic interference and thermal dissipation.
2. The Relevant Technology
PC cards are small, thin card-like structures that house a circuit board. Most PC cards are configured to comply with standards defined by the Personal Computer Memory Card International Association (PCMCIA). During use, the PC card is selectively inserted into a small aperture constructed in a personal computer or other electronic equipment. The circuit board of the PC card can be constructed to perform a variety of different functions. Most commonly, PC cards are used for either storing memory or for facilitating communication links over standard or wireless systems.
A conventional PC card comprises a circuit board having an input/output (I/O) connector attached at one end thereof. Mounted around the remaining perimeter of the circuit board is a plastic frame. A casing attaches to the frame to enclose the circuit board. The casing includes a stamped metal top plate that is secured by an adhesive to the frame over the top of the circuit board. A stamped metal bottom plate is likewise secured by an adhesive to the frame over the bottom of the circuit board.
Although PC cards are used extensively, they have several shortcomings. For example, electromagnetic interference can emanate from the circuit board and interfere with other electrical components within the computer. To help eliminate this interference, it is desirable to ground the PC card. The top and bottom metal cover plates, however, are separated by the plastic frame and adhesive which are non-conductive. Accordingly, supplemental connectors extending between the top plate and the bottom plate are required to enable complete grounding of the PC card. Even in this configuration, however, leaking can occur between the connectors.
Use of an adhesive in assembling the PC card results in yet other problems. Most notably, adhesives are both awkward and hazardous to work with. Furthermore, by using adhesives, the top and bottom plates of the casing must be exactly positioned and held in place until the adhesive cures. Likewise, as a result of using the adhesive, it is difficult if not impossible to remove the cover for repairing or modifying the circuit card without damaging the PC card.
An additional problem or limitation associated with conventional PC cards is heat dissipation. That is, to meet standardized size specifications, casings on most PC cards are formed from stamped sheet metal of a relatively thin thickness. As the demand and capabilities on PC cards increase, however, the components on the circuit board require increasing amounts of power. In turn, this increase in power consumption generates relatively high temperatures within the PC card. These elevated temperatures can damage or hamper the operation of the PC card.
An additional problem with conventional PC cards is electromagnetic interference between components on circuit board. Such interference can affect the operation of the PC card.