Extended heat frame for printed circuit board

A circuit board assembly for installation in a cabinet includes a first standards based size first mounting frame portion having a PCB mounted thereto. A second mounting frame portion is connected to the first mounting frame portion having no portion of the PCB connected thereto. A combination size of the first and second mounting frames defines a larger second standards based size. Multiple heat transfer components may be connected to the first or second mounting frame portion provide a conduction/convection cooling path. The first mounting frame portion may include a first false board edge and the second mounting frame portion includes one or more false board edge(s) positioned laterally and oppositely directed to the first false board edge. The first and second false board edges are slidably received in opposed slots created in a cabinet.

FIELD

The present disclosure relates to heat frames used in conjunction with printed circuit boards.

BACKGROUND

Ruggedized electronic systems commonly include one or more printed circuit boards (PCBs) which have a heat frame made for example of a heat conductive metal such as aluminum which is used to conductively transfer component heat from the PCB outward through the heat frame to a cooling structure of the electronics chassis or to a finned cooling component. PCBs are normally slidably received in the electronics chassis via opposed chassis guide rails, which sequentially located multiple PCBs, as well as provide the location to mechanically couple the PCB to the chassis. PCBs can also include a false board edge, which is a location where the main PCB is locally cut away at a location where the PCB would normally interface with the chassis guide rails, which is filled with mechanical structure in place of the PCB portion.

False board edges are provided to act as a load carrying member at the chassis guide rails. In place of a relatively heavy heatsink/heat frame that bends the PCB in response to vibration, the rigid metal structure of the heatsink/heat frame is instead tied to the chassis, and the PCB is connected to the rigid mechanical structure.

SUMMARY

According to several aspects, a circuit board assembly includes a first mounting frame portion of a first standards based size having a PCB mounted thereto. A second mounting frame portion is connected to the first mounting frame portion having no portion of the PCB connected thereto. A combination size of the first and second mounting frames defines a larger second size. At least one heat transfer component may be connected to the second mounting frame portion creating a conduction/convection cooling path away from the first mounting frame portion for removing heat generated by the PCB via the second mounting frame portion.

According to other aspects, a circuit board assembly for installation in a cabinet includes a first mounting frame portion of a first standards based size having a PCB mounted thereto. A second mounting frame portion is connected to the first mounting frame portion having no portion of the PCB connected thereto. A combination size of the first and second mounting frames defines a larger second size. Multiple heat transfer components may be connected to the second mounting frame portion providing a conduction/convection cooling path away from the first mounting frame portion for removing heat generated by the PCB via the second mounting frame portion. The first mounting frame portion may include a first false board edge and the second mounting frame portion includes one or more false board edge positioned laterally and oppositely directed with respect to the first false board edge. The first and second false board edges are slidably received in opposed slots created in a cabinet.

According to further aspects, an electronic cabinet system includes a cabinet having multiple first board slots created in a cabinet first wall and multiple second board slots created in a cabinet second wall. A circuit board assembly may include a first mounting frame portion of a first standards based circuit board size having a PCB mounted thereto. A second mounting frame portion is connected to the first mounting frame portion having no portion of the PCB connected thereto. A combination size of the first and second mounting frames defines a larger second circuit board size. At least one heat transfer component may be connected to the second mounting frame portion providing a conduction/convection cooling path away from the first mounting frame portion for removing heat generated by the PCB via the second mounting frame portion. The first mounting frame portion may include a first false board edge slidably received in one of the first board slots and the second mounting frame portion includes one or more false board edge(s) positioned laterally and oppositely directed with respect to the first false board edge.

DETAILED DESCRIPTION

Referring toFIG. 1, a circuit board assembly10can be adapted for sliding insertion into a chassis or housing such as a cabinet12. Circuit board assembly10is slidably received in an installation direction “A” within first and second board slots14,16created in each of a cabinet first wall18and a cabinet second wall19. Cabinet12can include a single set of first and second board slots14,16to receive a single circuit board assembly10or multiple sets of first and second board slots14,16to receive multiple circuit board assemblies10. Cabinet12can be used as a housing for a communication device such as a radio set or a computer station that can be exposed to atmospheric temperature conditions. Cabinet12and the components therein can therefore be exposed to ambient temperatures that may impose additional constraints on the ability to cool the components of circuit board assembly10.

According to several aspects, circuit board assembly10includes a standard sized printed circuit board (PCB)20such as a 3U board which is mounted to a first mounting frame portion22. A heat frame24is provided in contact with PCB20. Heat generated by the electrical components of PCB20can be conductively transferred away from PCB20via the heat frame24through a false board edge26to the cabinet second wall19via direct contact. The components of circuit board assembly10represented by a standard size (for example a 3U or a 6U standards based OVPX board) define a first portion28of circuit board assembly10. In certain operating conditions such as the high ambient temperature conditions in a desert environment, the heat generated by PCB20exceeds the conductive capability of the heat frame24to remove. To increase the heat removal capability without changing PCB20, a second portion30is added to circuit board assembly10.

Second portion30includes a second mounting frame portion32extending from the first mounting frame portion22. Second mounting frame portion32does not include any portion of PCB20. Second mounting frame portion32includes an extension portion false board edge34which is provided at a perimeter edge36of second mounting frame portion32oppositely directed with respect to false board edge26. Extension portion false board edge34is slidably and frictionally received in first board slot14of cabinet first wall18. Because second mounting frame portion32is positioned above PCB20when mounted in cabinet12, the surface area of second mounting frame portion32provides a conductive heat transfer path “B” to cabinet first wall18. To further increase the heat transfer capability of circuit board assembly10, at least one and according to several aspects multiple heat transfer components38may be mounted to second mounting frame portion32. Heat transfer components38can be provided in one example in the form of heat transfer fins, however any device providing increased surface area for convective heat transfer can be used, including tabs, wafers, plates and the like. The heat transfer components38and second mounting frame portion32increase a convective heat transfer area of circuit board assembly10without making any changes to the standard size PCB20or to heat frame24.

The total area of circuit board assembly10provided by both first and second areas28,30directly corresponds to an area of a larger footprint board. For example, if PCB20and first mounting frame portion22have a 3U standards based OVPX footprint, the total footprint of circuit board assembly10can be configured to correspond to a 6U standards based OVPX design. This permits interchangeability of circuit board assembly10for boards in a cabinet designed for larger (i.e., 6U OVPX) boards, thereby maintaining spacing, wedge-lock usage and board installation/removal parameters.

Referring toFIG. 2and againFIG. 1, circuit board assembly10includes PCB20connected to the first mounting frame portion22. One or more computer components40are connected to printed circuit board20, which can include items such as a central processing unit (CPU)42, a DIP switch44, multiple memory devices46, and other components such as a MOSFET, a power circuit, and/or a field programmable gate array (FPGA). During operation, the heat generated by CPU42can also in part be conductively dissipated for example by heat transfer to the cold edge at22and34. The conductive thermal transfer device such as heat frame24is directly connected to first mounting frame portion22. Heat frame24is in proximity to PCB20and provides additional conductive heat transfer paths for all of the heat generating components of circuit board assembly10, including CPU42. Second mounting frame portion32can be an integral portion extending from first mounting frame portion22, or can be separately connected to first mounting frame portion22.

Referring toFIG. 3and again toFIGS. 1 and 2, a circuit board assembly52is similar to circuit board assembly10having a PCB54mounted to a first mounting frame portion56, and further includes additional structural features including first and second support wings58,59connected to a second mounting frame portion60. An assembly62of heat transfer components64includes multiple rows of heat transfer components64configured in at least first, second, third, fourth and fifth rows66,68,70,72,74extending in a lateral direction “C” with respect to PCB54. The quantity of rows of heat transfer components64can also vary depending on the size and spacing of heat transfer components, therefore the quantity of rows or direction of the rows can vary between different circuit board assemblies of the present disclosure.

Referring toFIG. 4and again toFIGS. 1-3, according to further aspects a circuit board assembly76is further modified to provide heat transfer components extending not only in the lateral direction “C”, but further in a longitudinal direction “D” with respect to a PCB78. PCB78is mounted to a first mounting frame portion80having a first false board edge82on a first edge thereof. A second mounting frame portion84is connected to mounting frame portion80and extends in the lateral direction “C” with respect to first mounting frame portion80. Second mounting frame portion84includes a second false board edge86oppositely directed with respect to first false board edge82.

An assembly88of heat transfer components90includes multiple rows of heat transfer components90configured in exemplary first, second and third rows extending in the lateral direction “C”. Additional heat transfer components90are provided on a third mounting frame portion92which is directly connected to and extends in a longitudinal direction “D” with respect to second mounting frame portion84and is oriented coplanar to both first and second mounting frame portions80,84. A longitudinal second assembly96having multiple heat transfer components90is arranged on the third mounting frame portion92. Heat transfer components90provided on third mounting frame portion92are thereby longitudinally extended with respect to PCB78in the longitudinal direction “D” away from PCB78. Heat generated by PCB78can therefore be conductively and convectively transferred past a backplane98(only partially shown for clarity) to a lower temperature component area100of the cabinet12, where for example additional air flow may be available for convection cooling.

Circuit board assemblies and false board edges of the present disclosure allow for extending the size, and heat dissipating power of a heatsink and heat/mounting frame, while keeping the PCB within standard specified geometries. For example, for an air cooled 3U OVPX board, in a forced convection design (fan cooled), a standards based 3U air cooled heat/mounting frame could be employed. When for example the same design PCB was needed in a 6U natural convection system, the heat/mounting frame can be extended as noted herein to match the 6U OVPX footprint, which provides for the necessary cooling, while keeping the PCB unchanged. Beyond cooling or the reuse of boards in adjacent mechanical footprints, the additional space provided by the extended heat/mounting frame of the present disclosure can address mechanical concerns as well. For example, a large PCB can have issues under severe shock and vibration loads. One or more of the presently disclosed mounting frame portions/extensions could extend away from the PCB to provide additional stiffness, such as having a third set of wedge-locks in the center of the heat/mounting frame. Alternately, a single larger heat/mounting frame can be used to mechanically tie several smaller PCBs together into a single integrated unit.

According to several embodiments, the circuit board assembly10,52,76includes a first mounting frame portion22,56,80of a first standards based size (for example having a 3U OVPX size/space envelope) having PCB20,54,78mounted thereto. The first standards based size therefore provides the capability of the circuit board assembly10,52,76to slidably fit within the first and second slots of a cabinet designed to receive circuit board assemblies of the first standards based size. The second mounting frame portion32,60,84is connected to the first mounting frame portion22,56,80having no portion of the PCB20,54,78connected thereto, such that the size of PCB20,54,78does not change when incorporated on the circuit board assembly10,52,76. A combination size (defined as having a spacing or distance “E” between the first and second false board edges such as first and second false board edges26,36) of the first and second mounting frame portions22,56,80and32,60,84defines a larger second size (for example having a 6U OVPX size/space envelope). The second size therefore provides the capability for the circuit board assembly10,52,76to slidably fit within the first and second slots14,16of cabinet12. At least one heat transfer component38,74,90is connected to the second mounting frame portion32,60,84creating the conduction/convection cooling path “B” away from the first mounting frame portion22,56,80for removing heat generated by the PCB20,54,78via the second mounting frame portion32,60,84.