1. Field of the Invention
The present invention generally relates to a circuit host card with modules connected thereto and, more particularly, to a circuit host card having three electronic circuit board modules or mezzanine cards connected thereto.
2. Background Description
Printed circuit boards (PCB) or printed wiring boards (PWB) have been known for many years and may be formed by many techniques (e.g. screening, plating, etching, etc.). Printed wiring boards provide for a compact, structurally robust and easily manufactured electronic circuit structure. In use, discrete electronic components and integrated circuits are affixed to the boards via a host of commonly known techniques. Input/Output (I/O) pins are connected to the printed circuit boards (PCB) or printed wiring boards (PWB) in order to make connections to other components of an integrated system.
As electronic systems, such as communication systems and data processors, have become more complex, the use of multiple printed circuit boards connected to each other has been implemented. For ease of maintenance and repair, these complex systems have been fabricated in a modular form, often of standardized dimensions. These standardized dimensions, though, place limits on the size and shape of the module and hence the packaging density or packaging area of the system.
At the present time, a prevalent standard for modular circuit packaging is commonly known as the xe2x80x9cVersa Module Europaxe2x80x9d (VME) which incorporates a number of design standards including those known in the art as IEEE standard 1101.1, IEEE standard 1101.2, VITA20, ANSI/VITA1, VITA1.1 (VME64X) and IEEE standard P1386. While these standards allow some degree of freedom in component layout within the module, all of the standards involved in the collective VME standard are directed to modules including only a single printed wiring board having components mounted on only a single side thereof. Thus, in order to augment the area of the single VME standard board (also known as a host or main board), one or two circuit boards may be mounted to the host board via interconnections. These boards are known in the art as mezzanine boards or cards. Although the mezzanine boards increase the packaging density, the mezzanine board solution is limited to less than doubling the available area of the host board due to the configuration of the host board and placement of the connectors in accordance with the VME standard.
At present, there is only very limited ways known to further augment the printed wiring board area. This is due to several different reasons; namely, for example:
(i) The size of the host board;
(ii) The size of the mezzanine boards;
(iii) The placement and configuration of the I/O pins;
(iv) The placement and configuration of the connector assemblies between the host board and the mezzanine boards; or
(v) The cooling requirements of the entire system.
Being more specific, the host board is limited to certain dimensions, i.e., approximately 233.5 mm by 160 mm (equivalent to approximately 9xe2x80x3xc3x976.25xe2x80x3), which limits the mounting area of the connectors and mezzanine boards. The mezzanine board is also limited in size to approximately 74 mmxc3x97145 mm (approximately 3xe2x80x3xc3x975.5xe2x80x3). The I/O pins are placed at the edge of the board and are typically designated P1, P2, P0, where P0, P1 and P2 are multiple row multiple-pin configurations. This pin configuration also limits the placement of additional components and mezzanine boards. The mezzanine connector assemblies, on the other hand, may range from two to four connectors, but a first set of connectors must be placed within a range of approximately 40 mm+/xe2x88x9225.5 mnm from a side edge of the host board (leaving a space on the other opposite edge side of the board). This latter requirement provides a very exacting standard for the placement of the mezzanine boards thus, again, limiting the placement of additional components and mezzanine boards. Lastly, cooling ribs run along the length of the host board for dissipating heat generated from the mezzanine boards. This further limits the space and placement of the mezzanine boards. Thus, taking all of this into account, further augmenting the printed wiring board area has been difficult to achieve by card designers.
But, to overcome many shortcomings associated with the industry standard, the card design industry has devised several different solutions from adding additional host boards to removing certain functions from the host board or mezzanine boards. The former solution, though, requires additional costs, manufacturing and installation; whereas, the latter solution simply is not a very viable option. Another approach has been to add additional circuit cards to the backplane of the host board. This option adds complicated design considerations such as, for example, connection problems, the placement of the I/O pins and the like. All of these design considerations also add needlessly to the manufacturing and assembly costs.
The present invention is directed to overcoming one or more of the problems as set forth above.
In a first aspect of the invention, a circuit card assembly includes a host card having connector assemblies and a conduction-cooling path mounted thereon. At least one base mezzanine card having electronic circuitry defining a component field is provided. The at least one base mezzanine card is mounted to the conduction-cooling path of the host card and is further connected to the connector assemblies. A supplementary mezzanine card having electronic circuitry mounted thereon is mounted to the host card and over at least a portion of the component field. The mounting configuration provides a cooling path between the supplementary mezzanine card and the host card and also prevents mechanical interference between the supplementary mezzanine card and the component field. The supplementary mezzanine card is connected to another of the connector assemblies of the host card outside of the connector and PWB component field area of the at least one base mezzanine card.
In embodiments, the at least one base mezzanine card is a first base mezzanine card and a second base mezzanine card mounted in substantially a same mounting plane with respect to one another. The supplementary mezzanine card is a third mezzanine card mounted outside the connector and PWB component field area of the first and second base mezzanine cards. The third mezzanine card may be mounted over one of:
(i) a portion of the component field of the first base mezzanine card,
(ii) a portion of the component field of the first base mezzanine card and the component field of the second base mezzanine card, and
(iii) the component field of the first base mezzanine card and the component field of the second base mezzanine card.
The circuit card assembly, in further embodiments, includes a center cooling rib running along a length of the host card and side edge cooling ribs running along opposing edges of the host card. The at least one base mezzanine card is mounted to the center cooling rib and the supplementary mezzanine card is mounted to the side edge cooling ribs. In still further embodiments, the supplementary mezzanine card includes a cooling rib corresponding to a location of and mounted to the side edge cooling ribs and a faceplate cooling rib of the host card. A profile of the side edge cooling ribs and the cooling rib prevents mechanical interference between the another mezzanine card and the component field and further provides the cooling path. In yet another embodiment, the supplementary mezzanine card includes opposing cooling ribs corresponding to side edges of the host card for mounting thereon, and has a profile that prevents mechanical interference and provides the cooling path between the another mezzanine card and the host card.
In another aspect of the present invention, the host card has connector assemblies and a conduction-cooling path mounted thereon. A first base mezzanine card has electronic circuitry defining a component field. The first base mezzanine card is mounted to the conduction-cooling path and is further connected to a first set of the host mezzanine connector assemblies. A second base mezzanine card has electronic circuitry defining a component field and is mounted to the conduction-cooling path and is connected to a second set of the connector assemblies. A third mezzanine card is mounted to the host card over at least a portion of the component field of the first and/or second base mezzanine cards such that mechanical interference between the third mezzanine card and the component field of the first and second base mezzanine cards is prevented. The third mezzanine card is further connected to a third set of the connector assemblies of the host card outside of the connecting area and component field of the first and second mezzanine cards. At least the conduction-cooling path provides a cooling path between the first and second mezzanine cards and the host card.
In embodiments, the conduction-cooling path of the host card also provides a cooling path between the third mezzanine card and the host card. Alternatively, a conduction-cooling path on either the third mezzanine card or both the third mezzanine card and the host card provides the cooling path.
In yet another embodiment, a circuit card assembly includes first, second and third mezzanine cards mounted and connected to a host card. The third mezzanine card is connected outside a connecting area of the first and second mezzanine cards. A cooling path of the host card is used to mount the first, second and third mezzanine cards. The third mezzanine card also includes a conduction-cooling path that is mounted to the conduction-cooling path of the host card. The combination of the conduction-cooling paths provide a cooling path between the third mezzanine card and the host card. In embodiments, the profile of the conduction-cooling paths also prevents mechanical interference between the third mezzanine card and the first and second mezzanine cards.