High power dissipation mezzanine card cooling frame

Some embodiments are directed to cooling frames for mezzanine cards, mezzanine card assemblies and circuit card assemblies. A recessed cooling frame may be used to dissipate heat generated by components of a mezzanine card. The cooling frame may be directly coupled to a host card or host card cooling frame, thereby reducing the number of interfaces and reducing the thermal resistance of the heat dissipation pathway. The cooling frames of some embodiments may provide more efficient heat dissipation and thereby allow higher performance mezzanine cards to be used. Some embodiments provide a mezzanine card assembly that conforms to the mechanical envelope dimensions of the VITA 20, VITA 42 or VITA 61 specifications.

BACKGROUND OF INVENTION

The techniques described herein relate to a cooling frame for a mezzanine card for use in connection with a host card. The cooling frame and mezzanine card allow for high power heat dissipation.

Circuit card modules are used in many areas of computing and frequently utilize mezzanine cards and cooling frames. Standard bodies, such as the VMEbus International Trade Association (“VITA”) have developed both electrical and mechanical specifications to which most manufacturers adhere. Customers often prefer standardized components because it ensures compatibility between various products purchased from different vendors. Accordingly, most manufacturers adhere to the above standards for circuit card modules and/or mezzanine cards.

Circuit card modules may comprise printed circuit boards (PCBs) or printed wiring boards (PWBs), terms that are often used interchangeably. Electronic components, such as integrated circuits and processors, may be affixed to the boards. Mezzanine cards are PWBs that may be attached both mechanically and electrically to a host card. As the processors and integrated circuits that are affixed to mezzanine cards increase in performance, there arises a need for efficient, high power dissipation of the heat generated by these components.

Previous heat dissipation solutions transfer heat from the mezzanine card components to a top cooling frame, then to the mezzanine card PWB, and then finally to the host card frame.

BRIEF SUMMARY OF INVENTION

Some embodiments are directed to a mezzanine card assembly comprising a mezzanine card of a non-rectangular shape. The mezzanine card may have a a first mezzanine surface with at least one component mounted thereto and a second mezzanine surface opposing the first mezzanine surface. The mezzanine card assembly may also comprise a cooling frame, wherein joint dimensions of the cooling frame and the mezzanine card together conform to a standard dimensions requirements, for example VITA 20, VITA 42, VITA 61, etc. . . . The at least one component is in direct thermal contact with the cooling frame, which may be formed from a metallic material. The cooling frame may comprise at least one protrusion with a first protrusion surface at a first level defined by the second mezzanine surface and a second protrusion surface opposing the first protrusion surface. The PWB may comprise at least one cut-out portion configured to receive the at least one protrusion of the cooling frame. In some embodiments, the second protrusion surface is at a second level defined by the first mezzanine surface.

In some embodiments, the at least one protrusion is substantially rectangular. The at least one protrusion may comprise at least one hole for receiving attachment hardware, the at least one hole configured so that the attachment hardware mounts the cooling frame to a host card and/or a host card frame. Some embodiments may use at least one cooling pad comprising a first pad surface in contact with the cooling frame and a second pad surface, opposing the first pad surface, wherein the second pad surface is in contact with the at least one component.

Some embodiments are directed to a metallic frame for cooling a mezzanine card. The metallic frame may comprise a main body that is substantially rectangular comprising at least a first main body surface, wherein the main body is at a first level. The metallic frame may also comprise at least one protrusion at a second level other than the first level, wherein the at least one protrusion comprising at least a first protrusion surface. There may also be at least one sidewall connecting the main body to the at least one protrusion, wherein the at least one sidewall comprises at least a first sidewall surface, wherein the first sidewall surface is connected to the first main body surface and the first protrusion surface. In some embodiments, the first sidewall surface may be connected substantially perpendicular to the first main body surface and the first protrusion surface. The at least one protrusion may comprise at least one hole for receiving attachment hardware, the at least one hole configured so that the attachment hardware mounts the frame to a host card.

The metallic frame may also comprise a secondary body comprising at least a first secondary body surface substantially parallel to the first main body surface, wherein the secondary body is coupled to the main body by at least the at least one protrusion. The at least one protrusion may be configured to fit into a cut-out in a printed wiring board (PWB). A first thickness of the at least one protrusion may be configured to be substantially equal to a second thickness the PWB, wherein the first thickness and the second thickness are in the direction of the at least one sidewall.

Some embodiments are directed to a circuit card assembly comprising a host card, a mezzanine card and a cooling frame. The mezzanine card may be substantially parallel to the host card and comprise a first mezzanine surface with at least one component mounted thereto and a second mezzanine surface opposing the first mezzanine surface. The mezzanine card may be non-rectangular. The cooling frame may be in contact with the host card, wherein the cooling frame and the mezzanine card together have joint dimensions conforming to dimensions of a standard. The standard may be a VITA 20 standard, a VITA 42 standard, a VITA 61 standard or an IEEE standard.

The cooling frame may comprise at least one protrusion comprising a first protrusion surface at a first level defined by the second mezzanine surface and a second protrusion surface opposing the first protrusion surface. The mezzanine card may comprise at least one cut-out portion configured to receive the at least one protrusion of the cooling frame. The second protrusion surface may be at a second level defined by the first mezzanine surface. The cooling frame may further comprise a main body and a secondary body connected to the main body by the at least one protrusion, wherein the secondary body is substantially parallel to the main body. The mezzanine board may have at least one component in contact with the main body and at least one additional component in contact with the secondary body.

DETAILED DESCRIPTION OF INVENTION

The inventors have recognized and appreciated that one of the factors limiting performance of mezzanine cards and the components thereon is the ability to dissipate the heat generated during operation. Heat may be more efficiently transferred away from the components of a mezzanine card by reducing the number of interfaces between the hot components and a heat sink. Moreover, heat dissipation can be made more efficient through the primary usage of lower impedance thermal conduction materials, such as metallic interfaces as opposed to standard PWB construction. The inventors have recognized and appreciated that more efficient heat dissipation permits higher operating temperatures for mezzanine cards, higher performance, and/or longer lifetime of the components thereon with no other changes to the architecture.

The ability to transfer heat may be increased by reducing the number of interfaces heat must traverse. Thermal resistance of a heat path increases with the number of interfaces. Moreover, conducting the heat through highly conductive materials, such as metal, greatly increases the ability to dissipate heat. Accordingly, some embodiments of the invention are directed to techniques for directly thermally coupling a metallic cooling frame of a mezzanine card to the host card and/or a cooling frame associated with the host card, bypassing the need to transfer heat through the relatively low conductivity PWB of the mezzanine card. To achieve this direct coupling, some embodiments replace a thermal interface area of the PWB with a recessed metallic frame that both top cools the mezzanine card components and dissipates heat directly to the host card.

There are a variety of standards for circuit card modules. For example, VITA 61, VITA 42 and VITA 20 define mechanical and electrical specifications for a switched mezzanine card (XMC) and PCI (Peripheral Component Interface) Mezzanine Card (PMC), respectively. The standards each define a standoff height and a mechanical envelope to which mezzanine cards must adhere. A mechanical envelope may be a set of dimensions to which a mezzanine card assembly must adhere. There are many off-the-shelf components that are designed to work with cards abiding by these standards, such as connectors that match the standoff height. Therefore, some embodiments comprise a mezzanine card and cooling frame that together conform to the mechanical envelope and standoff height dictated by the VITA standards. A mezzanine card and a cooling frame together may be referred to as a mezzanine card assembly. A mezzanine card assembly may also include additional components. Similarly a circuit card assembly may refer to a host card and a mezzanine card assembly. A computer card assembly may also include additional components, including a cooling frame associated with the host card.

Embodiments of the invention are not limited to VITA standards. Other standard bodies exist for defining circuit card dimensions. For example, some embodiments are based on a IEEE specification of dimensions.

FIG. 1Ashows an exemplary mezzanine card100illustrative of some embodiments. The mezzanine card100may comprise a PWB and one or more components (not shown inFIG. 1A). The components may include processors, integrated circuits or any other suitable electrical component. The mezzanine card100has two surfaces, surface130is shown inFIG. 1Aand there is a second surface opposing surface130not shown inFIG. 1A. Components may be mounted to one or both surfaces of the mezzanine card100. The distance between the first surface130and the second surface determines the thickness of the PWB of the mezzanine card.

In some embodiments, the mezzanine card100is non-rectangular in shape. Any suitable shape may be used.FIG. 1Aillustrates an “I-shaped” mezzanine card100with a rectangular PWB with two rectangular “cut-outs”110and120along the long edge of the PWB. The cut-outs110and120are voids in the PWB of the mezzanine card100. The cut-outs110and120need not be precisely rectangular. For example, the corners of the rectangle may be rounded in any suitable way such that cut-outs are substantially rectangular. Embodiments are not limited to two cut-outs. For example, some embodiments may use four cut-outs—two along each long side of the PWB. Embodiments are not limited to any size, shape or number of cut-outs. The VITA standards define a rectangular envelope to which the dimensions of mezzanine card assemblies must conform. While the mezzanine card100does not adhere to the defined standard mechanical envelope due to the cut-outs110and120, as will be seen in connection withFIG. 1Cbelow, the mezzanine card100together with cooling frame150conform to the specified mechanical envelope of a particular standard.

The standard may also mandate the location and size of at least one hole105through the mezzanine card100. Attachment hardware may be placed through the hole to attach the mezzanine card100to the host card.

FIG. 1Bshows an exemplary cooling frame150illustrative of some embodiments. The cooling frame150may be placed in thermal contact with components of mezzanine board100in order to dissipate heat generated during the operation of said components. The cooling frame150is preferably made of a material with a high thermal conductivity. For example, any metal or metal alloy may be used, such as aluminum or copper. Alternatively, one or more thermally conductive polymers may be used to dissipate heat. Embodiments are not limited to any particular material. In some embodiments the cooling frame150is made from a single, integral piece of metal.

Cooling frame150may be any suitable shape that, when combined with the shape of mezzanine card100conforms to the mechanical envelope and standoff height defined by particular standards.FIG. 1Billustrates a cooling frame150with a relatively large, single main body152. The main body152may be placed in thermal contact with components of mezzanine card100in order to dissipate heat therefrom. The main body152may be substantially rectangular, substantially flat and substantially parallel to the surfaces of the mezzanine card100. In some embodiments, main body152may include cooling pedestals180-181designed to adjust the specific height of the main body at particular locations that correspond to a location of a component mounted to mezzanine card100. Cooling pedestals180-181need not be present in embodiments and, if they are, the size and shape are not limited in any way.

A sidewall154may run around the perimeter of main body152. The sidewall154determines the level at which the main body152sits relative to the components of mezzanine card100and must allow the form factor of the mezzanine card assembly to fit within the maximum material condition in the selected standard. The sidewall154may be any suitable thickness. The sidewall thickness must be enough to accommodate a variety of bolt holes that are mandated by the standard. However, as the sidewall154is made thicker, there will be less room for components on mezzanine card100under main body152. Accordingly, in some embodiments, the sidewall will be thicker near the bolt holes and thinner where there are no bolt holes.

The sidewall154connects main body152to protrusions160and170. Protrusions of the cooling frame150may be referred to as wings, ears or tabs. Cooling frame150may comprise any suitable number of protrusions. The number and shape of the protrusions may match the number and shapes of the cut-outs of mezzanine card100. Protrusions160and170comprise a first surface and a second surface opposing the first surface. The first and second surface of protrusions160and170may be substantially parallel to the surfaces of main body152. The distance between the first and second surface of the protrusions defines the thickness of the protrusions. As will be discussed in connection withFIG. 4below, in some embodiments the thickness of the protrusions may be the same as the thickness of the PWB of the mezzanine card.

In some embodiments, protrusions160and170may comprise at least one hole162and172, respectively. Holes162and172may receive attachment hardware, such as screws or bolts. The location and size of the holes162and172may be mandated by, for example, the VITA specification. Any suitable number of holes may be in each protrusion. For example,FIG. 1Billustrates protrusions160and170with two holes each.

FIG. 1Cillustrates the mezzanine card100and cooling frame150fitted together to form a mezzanine card assembly101in accordance with some embodiments of the invention. Protrusions160and170of cooling frame150may be fitted into cut-outs110and120of the mezzanine card100, respectively. Together, the mezzanine card100and the cooling frame150may conform to the rectangular envelope mandated by the VITA standard. Also, the cooling frame150may be designed such that it does not interfere with the at least one hole105required for attachment hardware, as mandated by the VITA standard.

FIG. 1Calso illustrates components131-132of mezzanine card100. In some embodiments, the components131-132may be in direct contact with cooling frame150, allowing efficient heat dissipation away from the components. In other embodiments, cooling pads135(illustrated inFIG. 5) may be placed between the components131-132and the cooling frame to facilitate thermal coupling. A cooling pad may comprise a first surface in contact with one or more of the components131-132and a second surface, opposed to the first surface, in contact with the main body152of the cooling frame150. The heat from components131-132may travel through the main body152to protrusions160and170. The protrusions160and170may be directly attached to the host card (not shown) via attachment hardware through holes162and172, respectively. This allows direct flow of heat from the cooling frame to the host card without the need for heat to dissipate through the PWB of mezzanine card100.

For illustrative purposes,FIG. 1Calso shows additional components134and136that do not dissipate heat through the cooling frame150. Also shown are connectors140-141, which may be used to electrically couple the mezzanine card100to the associated host card. Mezzanine card100may comprise additional components, either under main body152or not under the main body152, which are not shown for purposed of clarity.

FIG. 2Aillustrates a second mezzanine card200according to some embodiments of the invention. Many aspects of mezzanine card200may be similar to mezzanine card100. For example, mezzanine card200has a first surface230, a second surface opposed to the first surface, and mezzanine card200is non-rectangular due to two cut-outs210and220. Cut-outs210and220are larger than cut-outs110and120of mezzanine card100. This may provide additional direct thermal coupling of the mezzanine card to the host card. Also, as illustrated inFIG. 2B, it allows the cooling frame250to have additional areas to which components of the mezzanine card may dissipate heat.

The standard may mandate the location and size of at least one hole205through the mezzanine card200. Attachment hardware may be placed through the hole to attach the mezzanine card200to the host card.

FIG. 2Bshows a second exemplary cooling frame250illustrative of some embodiments. There are many similarities between cooling frame250and cooling from150. For example, cooling frame250may have a main body252, a sidewall254, cooling pedestals280-281, protrusions260and270, and holes262and272. Certain aspects of these components are the same as the corresponding components of cooling from150and are not repeated.

Protrusions260and270are longer than protrusions160and170. This additional surface area may provide additional direct thermal contact to the host card. The longer protrusions260and270allow for cooling frame250to have an a secondary body253, which may be smaller than main body252. The secondary body253may be attached to the main body252by the protrusions260and270. The secondary body253may be substantially parallel to main body252and at the same height, wherein the height of each of the bodies may be defined as the distance from the PWB of the mezzanine card200to one of the surfaces of the body. In some embodiments, the height of the secondary body253may be different from the height of main body252. There may be a gap between the main body252and the secondary body253. This gap may be any size, but as discussed below in connection withFIG. 2C, it must be large enough to accommodate the at least one hole205in mezzanine card200mandated by the VITA standard.

FIG. 2Cillustrates the mezzanine card200and the cooling frame250fitted together to form a mezzanine card assembly201in accordance with some embodiments of the invention. Protrusions260and270of cooling frame250may be fitted into cut-outs210and220of the mezzanine card200, respectively. Together, the mezzanine card200and the cooling frame250may conform to the rectangular mechanical envelope mandated by the VITA standard.

FIG. 2Calso illustrates components230-231of mezzanine card200. In some embodiments, the components230-231may be in direct contact with cooling frame250, allowing efficient heat dissipation away from the components. In other embodiments, cooling pads135(illustrated inFIG. 5) may be placed between the components230-231and the cooling frame to facilitate thermal coupling. The heat from components230-231may travel through the main body252to protrusions260and270. The protrusions260and270may be directly attached to the host card (not shown) via attachment hardware through holes262and272, respectively. This allows direct flow of heat from the cooling frame to the host card without the need for heat to dissipate through the PWB of mezzanine card200.

Not shown inFIG. 2Care additional components that may be on the surface of mezzanine card200under the secondary body253. Just as components230-231may be in contact with main body252, additional components may be in contact with secondary body253. The heat created by the additional components is carried away from the components by the secondary body253and transferred to the host card via protrusions260and270. The secondary body253may be separated from main body253to allow a gap between the bodies to accommodate the at least one hole205required by the VITA specification.

For illustrative purposes,FIG. 2Calso shows additional components234and236that do not dissipate heat through the cooling frame150. Also shown are connectors240-241, which may be used to electrically couple the mezzanine card200to the associated host card. Mezzanine card200may comprise additional components, either under main body252or not under the main body252, which are not shown for purposed of clarity.

FIG. 3illustrates a circuit card assembly300comprising the mezzanine card200, cooling frame250(only protrusions260and270are visible in the drawing), host card310, and host card cooling frame320. In some embodiments, the size of the mezzanine card assembly201may be mandated by a mechanical envelope defined in a VITA specification. The mezzanine card assembly201comprises the mezzanine card200and the cooling frame250. The cooling frame250may be mounted directly to the host card310and/or the host card cooling frame320using attachment hardware (not shown).

The host card310may be one of a plurality of host cards that are interconnected using a backplane of a larger computing device. The host card310may dissipate heat in any suitable way. For example, in military applications, the host card may be conduction cooled by being thermally coupled to the host card cooling frame320. The host card cooling frame320may ultimately be coupled to a larger metal chassis that dissipates the heat transferred from the mezzanine card200and the host card310. Conduction cooling may be preferred in military applications, such as military avionics, where the device must operate in harsh environments and air-flow over the electronic components must be prevented. Other embodiments may use air flow cooling of the components. Embodiments are not limited to a particular method of heat dissipation.

Host card cooling frame320may be considered part of host card310. The cooling frame320not only provides a means for dissipating heat generated by the host card, but it also provides structure and support to host card310. Similarly the cooling frames150and250associated with mezzanine cards100and200, respectively, also provide support and structure to the mezzanine cards.

FIG. 4andFIG. 5illustrate a close-up cross-section of mezzanine card assembly101, which comprises mezzanine card100and cooling frame150. Component132is mounted to mezzanine card100and is in direct thermal contact with the main body152of cooling frame150inFIG. 4. InFIG. 5, an embodiment where a cooling pad135is placed between the component132and the cooling frame150to facilitate thermal coupling. The cooling pad includes a first pad surface in contact with the cooling frame150and a second pad surface, opposing the first pad surface, in contact with the at least one component132. Protrusion160may have a thickness defined by the level450of a first surface and level451of a second surface. In some embodiments, this thickness is the same thickness as sidewall154and main body152. In some embodiments, the PWB of mezzanine card100has the same thickness defined by levels451and450. Surface130of the mezzanine card's PWB may be at the same level450as the first surface of protrusion160. By being at the same level450, the cooling frame150together with the mezzanine card100adhere to the VITA specification mechanical envelope dimensions.

Attachment hardware410may be used to mount the cooling frame150via protrusion160to the host card and/or the host card's cooling frame. Any suitable attachment hardware410may be used. For example, attachment hardware410may be a bolt or a screw.

Embodiments of the invention have been described with reference to the VITA standard, particularly the VITA 20, VITA 42 and VITA 61 specifications. Embodiments of the invention are not so limited and any circuit card module standard may be used. For example, a IEEE standard may be used.