A modular assembly for holding electrical circuitry

Abstract

A modular assembly of containers arranged in a stacked formation such that the base of each container provides the lid of the container immediately below it. Each container provides an EMI shield to electrical circuitry within its respective cavity; and wherein each container of the multiple containers is comprised from thermally conductive material to conduct heat away from the electrical circuitry. This arrangement provides an effective means of packaging RF systems where it is needed to provide RF isolation of the various parts of the circuitry from one another.

Description

[0001] A Modular Assembly for Holding Electrical Circuitry

[0002] This invention relates to a modular assembly comprising a stack of radio frequency (RF) shielding containers.

[0003] According to an aspect of the invention there is provided a modular assembly comprising multiple containers, each container having a closed cavity holding electrical circuitry mounted against a base wall of its respective container, the electrical circuitry in at least one of the containers comprising radio frequency (RF) circuitry; the multiple containers arranged in a stacked formation such that the base wall of a first container of the multiple containers sits against an open face of a second container of the multiple containers to provide a lid of the second container; wherein each container provides an EMI shield to the electrical circuitry within its respective cavity; and wherein each container of the multiple containers is comprised from thermally conductive material to conduct heat away from the electrical circuitry.

[0004] The system finds particular application in RF systems comprising multiple circuit boards that require shielding from one another, e.g. to preserve the sensitivity of the RF system over a wide band of frequencies.

[0005] In one application there is provided an electrical system comprising a first circuit board carrying RF circuitry, a second circuit board carrying digital processing circuitry, and a third circuit board carrying electrical power regulation circuitry for regulating electrical power supplied to the first and second circuit boards; the system housed in the modular assembly which comprises three stacked containers, each of the first, second and third circuit boards housed in a different one of the three stacked containers.

[0006] The assembly provides each circuit board of a multiple circuit board system with its own EMI shielded enclosure whilst reducing the amount of metal work and space required to achieve this over a conventional separate box system.

[0007] Each container of the multiple containers may comprise mounting flanges and wherein adjacent containers within the stack formation are mechanically fastened together about their respective mounting flanges.

[0008] Each mounting flange may comprise an aperture receiving a fastener that mechanically fastens the stacked formation of containers together.

[0009] Each of the multiple containers may comprise an upper flange and a lower flange, and wherein the first container and second container are directly fastened together through the fasteners securing the lower flange of the first container to the upper flange of the second container.

[0010] Each container may have side walls; and the base wall of side walls of each container is comprised from metal. This provides an efficient means to provide an EMI shielding container and also provide good heat connection characteristics to effectively draw heat away from the electrical circuitry within the containers. Each container may comprise a single integral piece that defines, at least in part, the side walls and base wall of the container.

[0011] The modular assembly may comprise an electrically conductive lid mounted over an open face of the first container of the multiple containers to close the cavity of the first container to provide an enclosed EMI shield around circuitry within the first container.

[0012] The modular assembly may comprise a physical data connection comprising a circuit connector means that extends through the base wall of the first container to interconnect the electrical circuitry in the first container and the electrical circuitry in the second container. The circuit connector may comprise an electrical connector or an optical connector.

[0013] The multiple containers may include a third container, the second container lying between the first container and third container, a base wall of the second container sits against an open face of a third container to provide a lid of the third container. The physical data connection may interconnect electrical circuitry in the third container with the electrical circuitry in the first container; the physical data connection extending through the base wall of the second container, and optionally through a circuit board that carries the electrical circuitry in the second container.

[0014] The third container may hold electrical power regulation circuitry comprising a power output, and in which the assembly comprises a connector stack that extends through the base walls of at least two of the containers of the stacked multiple containers to connect the power output to the electrical circuitry within the first and second containers to power the electrical circuitry within the first and second containers.

[0015] Separate sets of fasteners (one or more fasteners per set) may be used to mechanically fasten together containers that are immediately adjacent one another. For example, where the stack comprises three containers, a first set of fasteners may be used to mechanically secure the first and second container together, and a second set of fasteners used to secure the second and third containers together. This enables fasteners of the same length to be used irrespective of the number of containers in the stack.

[0016] The invention will now be described by way of example with reference to the Figure which is a side cross-section schematic view of a modular heat sink assembly holding a multi-board RF system.

[0017] The Figure shows a modular heatsink assembly 1. The assembly 1 comprises multiple substantially identical stacked containers 10, 20, 30.

[0018] Each container 10, 20, 30 comprises a base wall 3 and one or more side walls 4 that between them provide a cavity 5.

[0019] In the stacked configuration, the containers 10, 20 30, sit upon one another such that the openings of the cavities 5 of the containers 20,30 are completely occluded by the base walls 3 of the containers 10, 20 immediately adjacent it. The cavity 5 of the uppermost container 10 is closed off with lid 6. The base wall 3, side walls 4 and lid 6 are electrically conductive and have high thermal conductivity. A suitable material for base wall 3, side walls 4 and lid 6 includes a metal, e.g. plate metal, such as one or more of: aluminium, steel or copper. Each container may be comprised from a single integral piece of metal that defines, at least in part, the base wall 3 and side walls 4, e.g. formed using a sheet metal fabrication process.

[0020] The above arrangement provides three, stacked, RF shielded enclosures.

[0021] Each container 10, 20, 30 comprises an upper mounting flange 7 and a lower mounting flange 8. The upper and lower flanges 7 8 each comprise through-apertures 7A 8A. The through apertures 7A of the upper flanges having a threaded internal wall.

[0022] In the stacked configuration the upper and lower flanges of neighbouring containers 10, 20, 30 sit against one another and are mechanically secured together by threaded fasteners 9. The apertures 7A of the upper flanges 8 are threaded to engage and retain the threaded fastener 9.

[0023] Separate fasteners 9 are used to fasten immediately adjacent containers of the stack together, i.e. one set of fasteners is used to fasten first container 10 to second container 20, and a second set of fasteners is used to fasten the second container 20 to the third container 30. This arrangement means fasteners 9 of the same length can be used regardless of the number of containers in the stack, providing improved modularity to the assembly. A heat conductive paste or equivalent material may be used in the interface between the contacting faces of the upper and lower flanges 7 8 to improve heat transfer therebetween.

[0024] Housed within each cavity 5, mounted against an inside face of the base wall 3, is a PCB carrying electronic circuitry.

[0025] An application of the assembly 1 is to carry circuitry for an RF system comprising an RF receiver and / or transmitter. For some applications, it is necessary for the RF system to operate over a wide bandwidth, namely three or more octaves, with high sensitivity. This provides the challenge of providing high levels of RF isolation, and thus shielding, between the digital and analogue parts of the system.

[0026] In the cavity 5 of a first container 10 is held RF circuitry 50 of the RF receiver and / or transmitter. In the cavity 5 of the second container 20 is held digital processing circuitry 60. In the cavity 5 of the third container 30 is held power regulating circuitry 70. The circuitries 50, 60, 70 are RF shielded from each other by the EMI shielding provided by its respective closed cavity 5. The EMI shielding also shields the circuitry 50, 60 70 from sources of EMI external to the assembly, as well as shielding sensitive circuitry external to the assembly from the EMI emanating from the circuitries 50, 60, 70 within the stacked containers 10, 20, 30. A data connection between the circuities 50, 60, 70 in each container 10, 20 30 is provided through a data interconnect stack comprised from multiple stacked-through electrical connectors 80, 81. Upward extending connectors 80 of the circuitries 60, 70 of the second and third containers 20, 30 interconnect with downwardly extending connectors 81 of the circuitries 50, 60 of the first and second containers 20, 30 that pass through base walls 3 of first and second containers 20, 30.

[0027] Power is supplied from a power output 71 of the power regulating circuitry 70 in the third container 30 to the RF circuitry 50 and digital circuitry 60 through a power interconnect stack comprised from connectors 9091. Upward extending connectors 90 of the circuitries 60, 70 of the second and third containers 20, 30 interconnect with downwardly extending connectors 91 of the circuitries 50, 60 of the first and second containers 20, 30 that pass through base walls 3 of first and second containers 20, 30.

[0028] In one example, the connectors 80 90 may be multi-pin female head connectors, and the connectors 81 91 may be multi-pin male head connectors.

[0029] Each container 10, 20 30 acts as a heatsink for the circuitry within its cavity 5. A good thermal path may be provided between the circuity and the inside face of the base wall 3 through use of a thermal paste or other conformal medium. Due to the high thermal conductivity of the base wall 3 compared with the air space within the cavity 5, heat is preferentially drawn laterally outwards through the base wall 3 to the side walls 4, whence it is the drawn vertically through the side walls 4 of the stack to a cold wall (not shown) upon which the assembly 1 is mounted when in use, either against the exterior face of the base wall 3 of the bottom container 30 or the lid 6 on the top container 30, or both. The thickness of the base walls 3 and side walls 4 are selected to provide sufficient rate of heat flow towards the cold wall based on anticipated heat generated by the circuitry 50, 60, 70 and operating environment, to maintain the circuitry 50, 60, 70 below a desired maximum operating temperature.

[0030] The nomenclature used above, e.g. the terms upper, lower, etc is made in reference to the orientation of the assembly 1 as illustrated in the Fig and is not to be taken as limiting.

[0031] In this example there are three stacked containers but this is not to be taken as limiting.

[0032] Similar arrangements with two, or more than three, containers could be used.

Claims

Claims1. A modular assembly comprising multiple containers, each container having a closed cavity holding electrical circuitry mounted against a base wall of its respective container, the electrical circuitry in at least one of the containers comprising radio frequency (RF) circuitry; the multiple containers arranged in a stacked formation such that the base wall of a first container of the multiple containers sits against an open face of a second container of the multiple containers to provide a lid of the second container; wherein each container provides an EMI shield to the electrical circuitry within its respective cavity; and wherein each container of the multiple containers is comprised from thermally conductive material to conduct heat away from the electrical circuitry; and wherein each of the multiple containers comprises an upper mounting flange and a lower mounting flange, each comprising an aperture, and wherein the first and second containers are directly fastened together by a fastener received in the apertures to secure the lower mounting flange of the first container to the upper flange of the second container.

2. A modular assembly according to any previous claim wherein each container has side walls; and the base wall and side walls of each container is comprised from metal.

3. A modular assembly according to claim 2 wherein each container is comprised from a separate single integral piece, each single integral piece defining, at least in part, the side walls and base wall of the container.

4. A modular assembly according to any previous claim comprising an electrically conductive lid mounted over an open face of the first container of the multiple containers to close the cavity of the first container.

5. A modular assembly according to any previous claim comprising a data circuit connector means that extends through the base wall of the first container to interconnect the electrical circuitry in the first container and the electrical circuitry in the second container to carry data therebetween.

6. A modular assembly according to claim 7 wherein the multiple containers comprise a third container, the second container lying between the first container and third container, a base wall of the second container sits against an open face of the third container to provide a lid of the third container to close the cavity of the third container; and wherein the data circuit connector interconnects electrical circuitry in the third container with the electrical circuitry in the first container to carry data therebetween; the data circuit connector extending through the base wall of the second container, and optionally through a circuit board that carries the electrical circuitry in the second container.

7. A modular assembly according to any previous claim wherein the multiple containers comprise a third container holding electrical power regulation circuitry comprising a power output, and in which the assembly comprises a connector stack that extends through the base walls of at least two of the containers of the stacked multiple containers to connect the power output to the electrical circuitry within each of the first and second containers to power the electrical circuitry within the first and second containers.

8. An electrical system comprising a first circuit board carrying RF circuitry, a second circuit board carrying digital processing circuitry, and a third circuit board carrying electrical power regulation circuitry for regulating electrical power supplied to the first and second circuit boards; the system housed in a modular assembly of any previous claim comprising three stacked containers, each of the first, second and third circuit boards housed in a different one of the stacked containers of the modular assembly.

9. A modular assembly comprising multiple containers, each container having a closed cavity holding electrical circuitry mounted against a base wall of its respective container, the electrical circuitry in at least one of the containers comprising radio frequency (RF) circuitry; the multiple containers arranged in a stacked formation such that the base wall of a first container of the multiple containers sits against an open face of a second container of the multiple containers to provide a lid of the second container; wherein each container provides an EMI shield to the electrical circuitry within its respective cavity; and wherein each container of the multiple containers is comprised from thermally conductive material to conduct heat away from the electrical circuitry.

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