Monoblock card frame with dual surface thermal interface solid retainers to maximize thermal transfer of plug-in module assemblies in conduction cooling applications

Abstract

The present invention describes a plug-in module assembly (50) employing a monoblock card frame (11) adapted to interface thermally with a chassis slot (40) achieving the lowest possible thermal resistance by reducing the number of elements in the thermal path to one solid retainer (20) and by maximizing the area of contact between the solid retainer (20) and the monoblock card frame (11). The solid retainer (20) features a decreasing thickness from a first end to a second end in a longitudinal plane. The solid retainer (20) includes a first surface (21) to make full contact with the chassis slot (40), a second surface (22) and a third surface (23) to make full contact with the monoblock card frame (11), where the second and third surfaces (22, 23) are perpendicular to each other. The monoblock card frame (11) further includes on each side a lateral thermally connected surface (12), and an integrated inclined guide (19) with an additional thermally connected surface (13). The lateral and inclined thermally connected surfaces (12, 13) are perpendicular to each other and are offset at an angle from 3° to 15° in a transversal plane from the vertical lateral edge of the monoblock card frame (11). Accordingly, the plug-in module assembly (50) can be switched from an unlocked position as to locked position, and backwards. When a locking screw is turned counterclockwise, the first surface (21) pushes against the upper ledge (41) of the chassis slot (40), the counter force presses the solid retainer (20) down increasing the force between the inclined thermally connected surface (13) and the third surface (23), creating a resultant lateral force which presses second surface (22) against the lateral thermally connected surface (12). The relevant advantages of the present invention consist of the maximized area of surfaces in contact and the reduction of the number of intermediary elements in the thermal path resulting in the lowest possible thermal resistance occurring between the monoblock card frame through the solid retainers up to the chassis. A second embodiment includes a spring-loaded screw holder with an antivibration feature so that the locking screw pushes back the spring-loaded screw holder, which flexes elastically keeping constant pressure on the locking screw. In addition, the monoblock card frame of this embodiment includes a visual indicator for locked and unlocked positions.

Description

[0001] MONOBLOCK CARD FRAME WITH DUAL SURFACE THERMAL INTERFACE

[0002] SOLID RETAINERS TO MAXIMIZE THERMAL TRANSFER OF PLUG-IN MODULE ASSEMBLIES IN CONDUCTION COOLING APPLICATIONS

[0003] FIELD OF THE INVENTION

[0004] The present invention relates generally to embedded computing applications in modular open standard architectures where thermal management is achieved by conduction cooling. Some of the architectures suitable for this invention are Open VPX, SOSA, Space VPX, VNX, Compact PCI Serial, Compact PCI Serial Space, and ADHA, an architecture developed under the supervision of the European Space Agency based on PICMG’s Compact PCI Serial Space Specification.

[0005] BACKGROUND OF THE INVENTION

[0006] In conduction cooled embedded computing systems, electronic boards are housed into metal enclosures called plug-in modules, which are thermally connected into their respective chassis using retainers, sometimes referred to as wedgelocks, which are attached to the edges of the card frames. Retainers realize the thermal connection between the plug-in modules’ card frame edges and the chassis, by tightly pressing the edges of the card frame against the inner edge of a metal slot in the chassis, thereby creating a thermal path for heat to flow from the electronic components and board, through the card frame edges to the chassis’ slot by thermal conduction.

[0007] There are many documents in the state of the art, with the objective to solve the problem of improvement of the heat transfer between plug-in modules and chassis. For example, US patents 3,820,592 and 10,129,996 depict plug-in module assemblies including sets of two wedged elements activated by screws or screwed shafts until pressure locks the cards within the chassis. However, the solutions described in these patents, as well as conventional wedgelocks, are limited to being independent assemblies comprised of minimum two interfacing parts which need to be installed onto card frames and they all apply pressure onto one single surface of contact with the card frames in the perpendicular direction to the mounting surface, and therefore limiting the total area available for thermal transfer.

[0008] Some card lock devices are oriented to improve the area of contact to increase thermal transfer by employing elements with two areas of contact for bidirectional heat flow. For example, US patents 4,298,904 and 10,034,403, and US patent application US20070253169 describe complex wedgelocks with multiple sliding components that push the wedgelocks in opposed directions. Albeit some improvement is obtained, these solutions employ multiple components coming into contact with reduced material cross-sections therefore these solutions do not permit obtaining the lowest possible thermal resistance of the assembly because of multiple serial interfaces and reduced areas of contact which increase the thermal resistance of the combined serial connections.

[0009] SUMMARY OF THE INVENTION

[0010] The first object of the present invention is to provide a plug-in module assembly featuring a monoblock card frame configuration incorporating dual perpendicular surfaces of direct and concurrent interface between the top body of the card frame and the body of a solid retainer on each side of the card frame, leading to the lowest possible thermal resistance between the body of the card frame and the solid retainer.

[0011] The second object of the present invention is to maximize the area of direct thermal contact between the body of the bottom edges of the plug-in module and the chassis slot on the opposite side of the solid retainer.

[0012] The third object of the present invention is to improve thermal transfer by employing materials with higher coefficient of thermal conductivity in the manufacturing of the solid retainers.

[0013] The fourth object of the present invention is to realize a monoblock card frame with only one solid retainer on each side resulting in an assembly with lowest possible thermal resistance in the path of the heat flow, and the fewest possible number of components to reduce the number of thermal junctions in the thermal path from components to the chassis. The fifth object of the present invention is to provide a plug-in module assembly with a shock and vibration proof spring locking feature for keeping the plug-in module assembly fully locked position in conditions where the system is exposed to high levels of shock and vibration.

[0014] Other features and advantages of the present invention will be apparent from the detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] For the purposes of illustrating the present invention, the drawings show aspects of one embodiment of the invention, as an example applied to a 3U VPX plug-in module.

[0017] Nonetheless, it should be understood that the invention is not limited to the precise arrangement shown in the drawings and may apply equally to 6U and other size and shape plug-in modules as utilized in VPC, VNX, CPCI and other architectures. The accompanying drawings are not intended to be drawn to scale. In the drawings:

[0018] FIG.1A is a perspective front top view of a first embodiment of the plug-in module assembly, showing a monoblock card frame with the space where the solid retainer would be placed;

[0019] FIG. IB is a perspective rear top view of the first embodiment of the plug-in module assembly, showing the monoblock card frame with the solid retainer in place;

[0020] FIG. 1C is a top plan view of the first embodiment of the plug-in module assembly, showing the monoblock card frame inserted into a section of the chassis;

[0021] FIG. 2A is a cross-section view of the first embodiment of the plug-in module assembly in locked position, along transversal plane A-A of FIG. 1C;

[0022] FIG. 2B is a cross-section view of the first embodiment of the plug-in module assembly in unlocked position, along longitudinal plane B-B of FIG. 1C;

[0023] FIG. 2C is a cross-section view of the first embodiment of the plug-in module assembly in locked position, along longitudinal plane B-B of FIG. 1C; FIG. 2D is a cross-section view of the monoblock card frame of the first embodiment of the plug-in module assembly, along transversal plane A-A of FIG. 1C;

[0024] FIG. 3A is a cross-section view of a second embodiment of the plug-in module assembly in unlocked position, along longitudinal plane B-B of FIG 1C;

[0025] FIG. 3B is a cross-section detailed view of the second embodiment of the plug-in module assembly, showing the solid retainer in unlocked position along a longitudinal plane;

[0026] FIG. 3C is a cross-section detailed view of the second embodiment of the plug-in module assembly, showing the solid retainer in locked position along a longitudinal plane;

[0027] FIG. 4A is an isometric view of one of two solid retainers of the plug-in module assembly of the present invention;

[0028] FIG. 4B is an isometric view of the screw holder of the first embodiment of the plugin module assembly of the present invention;

[0029] FIG. 4C is an isometric view of the screw holder of the second embodiment of the plug-in module assembly of the present invention;

[0030] DETAILED DESCRIPTION OF THE INVENTION

[0031] One or more embodiments of a monoblock card frame with single solid retainers for improved thermal conduction of plug-in module assembly is described herein. In the following description, specific details are set forth to provide a thorough understanding of the embodiment. However, a person skilled in the relevant art will recognize that the techniques described herein can be practiced without one or more of the specific details, or with other components, materials, etc.

[0032] In accordance with FIGS. lAto 1C, the present invention refers to a monoblock card frame (11) to secure a plug-in module assembly (50) within a chassis using solid retainers (20). As can be appreciated from FIG. 2A, in a first embodiment the plug-in module assembly (50) comprises a printed circuit board (55) captured between the monoblock card frame (11), and a bottom cover (59). Further, the plug-in module assembly (50) includes on each side a solid retainer (20) employing a first surface (21) to make full contact with an upper ledge concurrent contact with the monoblock card frame (11). In the preferred embodiment, the second and third surfaces (22, 23) of the solid retainer (20) are perpendicular to each other. In the illustrated embodiment of FIGS. 2B and 2C, the solid retainer (20) has a decreasing thickness from a first end (24) to a second end (25), when seen from longitudinal plane B-B. Therefore, the third surface (23) of the solid retainer (20) has an inclined angle of 1° to 5°, preferably between 2.5° to 3.5°. The bottom of the monoblock card frame (11) is solid and makes direct contact with a bottom ledge (42) of the chassis slot (40). In this embodiment, the bottom cover (59) is shown extended into the chassis slot (40) but in other embodiments, the bottom cover (59) does not extend into the chassis slot (40) and consequently, the bottom of the guide would extend all the way to the bottom ledge (42) of the chassis slot (40).

[0033] Referring to FIG. 1A, the monoblock card frame (11) includes a lateral thermally connected surface (12), and a solid inclined guide (19) integrated into the body of the monoblock card frame (11). Furthermore, the inclined guide (19) which has an inclined thermally connected surface (13) with an inclination angle of 1° to 5°, preferably between 2.5° to 3.5°. In the preferred embodiment, the lateral thermally connected surface (12) and the inclined thermally connected surface (13) are perpendicular to each other. In this embodiment, the lateral and inclined thermally connected surfaces (12, 13) are tilted inwardly towards the monoblock card frame (11) at an angle from 3° to 15° from the vertical lateral edge of the monoblock card frame (11), when seen from transversal plane A- A, as illustrated in FIG. 2D.

[0034] In accordance with FIGS. 2B and 2C, the inclined thermally connected surface (13) has a decreasing thickness from a third end (15) to a fourth end (14), when seen from longitudinal plane B-B. During the assembly of this embodiment, the first end (24) of the solid retainer (20) is located proximate to the fourth end (14) of the inclined guide (19), while the second end (25) of the solid retainer (20) is located proximate to the third end (15) of inclined guide (19).

[0035] Moreover, in the first embodiment illustrated in FIGS. 2B, 2C and 4B, the plug-in module assembly (50) further includes a screw holder (35) to interact with a locking screw (30). The screw holder (35) is preferably L-shaped. The screw holder (35) includes a base (36) to be fixed to the monoblock card frame (11), and a wall (37) with a slot (38). The screw holder (35) is placed in proximity to the front end (14) of the monoblock card frame (11). In addition, the solid retainer (20) further includes a treaded borehole (29) in the first end (24) for receiving the locking screw (30), as depicted in FIGS. 2B, 2C and 4A. The borehole (29) is shown in the figures only as a threaded borehole, however in various embodiments depending on the material used to make the solid retainer (20), a spiral threaded insert is used in order to prevent damage of threads when torque is applied to the locking screw (30).

[0036] In the preferred embodiment, the locking screw (30) passes through the monoblock card frame (11), it is secured in place by the slot (38) of the screw holder (35), and treads into the treaded borehole (29) of the solid retainer (20). Accordingly, the plug-in module assembly (50) can be switched from an unlocked position as depicted in FIG. 2B to a locked position as depicted in FIG. 2C. When the locking screw (30) is turned counter-clockwise, and first surface (21) of the solid retainer (20) pushes against the upper ledge (41) of the chassis slot (40), the counter force presses the solid retainer (20) down increasing the force between the inclined thermally connected surface (13) and the third surface (23) of the solid retainer (20), creating a resultant lateral force which presses second surface (22) of the solid retainer (20) against the lateral thermally connected surface (12) of the card frame, thereby achieving solid thermal interfaces concurrently between surfaces (13) with (23) and (12) with (22). The relevant advantage of the present invention consists of the increased area of contact resulting in improved thermal transfer flow between the monoblock card frame (11) through the solid retainer (20) and into the chassis slot (40). As can be understood by a skilled person in the art, the plug-in module assembly (50) can be switched from the locked position to the unlocked position when the locking screw (30) is turned clockwise.

[0037] In order to enhance the thermal conductivity, it is relevant for the present invention to mention that the solid retainer (20) is manufactured from high conductivity copper alloy, with suitable plating finish, with a thermal conductivity among 355W / m*K to 391W / m*K, or copper-silver alloy, with suitable plating, with a thermal conductivity about 410W / m*k.

[0038] A second embodiment of the plug-in module assembly (50’) is shown in FIGS. 3 A to 3C, which differ from the first embodiment in that the holder is a spring-loaded screw holder (35’), individually illustrated in FIG. 4C. The spring-loaded screw holder (35’) is preferably L-shaped, including a base (36’) to be fixed to the monoblock card frame (11), and a wall having an angled portion (39’) and a straight portion (37’) which has a slot (38’). Similarly to the first embodiment, the plug-in module assembly (50’) can be switched from an unlocked position as depicted in FIG. 3B to a locked position as depicted in FIG. 3C. The spring-loaded screw holder (35’) is placed in proximity to the fourth end (14) of the monoblock card frame (11), the locking screw (30) passes through the monoblock card frame (11), it is secured in place by the slot (38’) of the spring-loaded screw holder (35’), and treads into the treaded borehole (29) of the solid retainer (20). However, the spring-loaded screw holder (35’) is configurated to maintain constant pressure on the locking screw (30) when it is in fully locked position and to prevent unwanted rotation when the assembly is subjected to high levels of shock and vibration. When the locking screw (30) is turned counterclockwise and the solid retainer (20) reaches the chassis (40) to the fully locked position, the locking screw (30) pushes back the angled portion (39’) of the wall of the spring-loaded screw holder (35’), which flexes elastically keeping constant pressure on the locking screw (30).

[0039] In addition, the spring-loaded screw holder (35’) provide clear visual feedback confirming whether the solid retainer (20) is locked or unlocked into the chassis slot (40) through a visual indicator. When the solid retainer (20) is unlocked, the head the locking screw (30) is recessed and clears an indication area (10) of the monoblock card frame (11). This area is visually observable by the user. When the solid retainer (20) is fully locked into the chassis slot (40), the head of the locking screw (30) is flush with the front surface of the monoblock card frame (11), covering over the indication area (10).

[0040] Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, this invention is not limited to the details provided. There are alternative ways of implementing the invention. The disclosed embodiments are illustrative and not restrictive.

Claims

CLAIMS1. A plug-in module assembly comprising a monoblock card frame with two perpendicular thermally connected surfaces per side; the plug-in module assembly comprising a solid retainer per side having a decreasing thickness from a first end to a second end in a longitudinal plane; the solid retainer including a first surface to make full contact with an upper ledge of a chassis slot, a second surface and a third surface to make full concurrent contact with the monoblock card frame; wherein the second and third surfaces are perpendicular to each other; and the plug-in module assembly is characterized in that: the monoblock card frame including a lateral thermally connected surface, and an integrated inclined guide incorporating an inclined thermally connected surface; wherein the lateral and inclined thermally connected surfaces are perpendicular to each other and are tilted inwardly at an angle from 3° to 15° in a transversal plane from a vertical lateral edge of the monoblock card frame; and the inclined guide having a decreasing thickness from a third end to a fourth end in a longitudinal plane; wherein the first surface pushes against the upper ledge of the chassis slot, the counter force presses the solid retainer down increasing the force between the inclined thermally connected surface and the third surface, creating a resultant lateral force which presses second surface against the lateral thermally connected surface.

2. The plug-in module assembly in accordance with claim 1, wherein the first end of the solid retainer is located proximate to the fourth end of the card frame and the second end of the solid retainer is located proximate to the third end of the monoblock card frame.

3. The plug-in module assembly in accordance with claim 1, wherein each of the second surface of the solid retainer and the inclined thermally connected surface has an inclined angle of 1° to 5°, preferably between 2.5° to 3.5°.

4. The plug-in module assembly in accordance with claim 1, wherein the solid retainer is secured to the monoblock card frame by a locking screw.

5. The plug-in module assembly in accordance with claim 1, wherein the solid retainer is manufactured from high conductivity copper alloy or copper-silver alloy.

6. The plug-in module assembly in accordance with claim 4, wherein the monoblock card frame includes an L-shaped screw holder having a base to be fixed to the monoblock card frame and a wall with a slot.

7. The plug-in module assembly in accordance with claim 6, wherein the screw holder is placed in proximity to the fourth end of the monoblock card frame.

8. The plug-in module assembly in accordance with claim 7, wherein the solid retainer further includes a treaded borehole in the first end for receiving the locking screw.

9. The plug-in module assembly in accordance with claim 8, wherein the locking screw passes through the monoblock card frame, the slot of the screw holder and treads into the treaded borehole of the solid retainer.

10. The plug-in module assembly in accordance with claim 6, wherein the wall has an angled portion and a straight portion which has the slot.

11. The plug-in module assembly in accordance with claim 10, wherein the locking screw pushes back the angled portion of the wall of the screw holder, which flexes elastically keeping constant pressure on the locking screw.

12. The plug-in module assembly in accordance with claim 10, wherein the monoblock card frame includes a visual indicator for locked and unlocked positions.

13. The plug-in module assembly in accordance with claim 12, wherein the visual indicator consists in that the head the unlocked screw clears an indication area of the monoblock card frame, while the head of the locked screw flush with the front surface of the monoblock card frame and covers the indication area.

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