Abstract:
A device structure includes a printed circuit board (PCB) comprising a thermal conduction plane, at least one heat generating component thermally connected to the thermal conduction plane, and a first frame portion thermally connected to the thermal conduction plane and at least partially enclosing the at least one heat generating component. The thermal conduction plane thermally connects the at least one heat generating component to the first frame portion by way of a plurality of vias from a surface of the PCB to the thermal conduction plane.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of priority under 35 U.S.C. §120 as a continuation of U.S. patent application Ser. No. 13/904,992 entitled “Thermal Management for Solid-State Drive,” filed on May 29, 2013, which claims the benefit of priority under 35 U.S.C. §119 as a nonprovisional of U.S. Patent Application Ser. No. 61/811,577 entitled “Thermal Management for Solid-State Drive,” filed on Apr. 12, 2013, the disclosures of which are hereby incorporated by reference in their entirety for all purposes. 
    
    
     BACKGROUND 
     Solid-state drives (SSDs) are a type of data storage device that use a non-volatile solid-state memory, such as a flash memory, to store data. As SSD performance demands increase, power requirements generally increase. In addition, physical size requirements for SSDs generally stay the same or become smaller. 
     The increase in power requirements without a corresponding increase in physical size leads to challenges to dissipate more heat from SSDs. In addition, new standards for SSDs may specify reduced airflows over SSDs and higher ambient temperatures which further hinder heat dissipation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and advantages of the embodiments of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the disclosure and not to limit the scope of what is claimed. 
         FIG. 1  is a cross-section view of a solid-state drive (SSD) according to an embodiment. 
         FIG. 2  is a cross-section view of an SSD according to an embodiment. 
         FIG. 3  is a cross-section view of an SSD according to an embodiment. 
         FIG. 4A  provides a top view of an exterior of an SSD according to an embodiment. 
         FIG. 4B  provides a side view of the exterior of the SSD of  FIG. 4A  according to an embodiment. 
         FIG. 5A  provides a top view of an exterior of an SSD according to an embodiment. 
         FIG. 5B  provides a side view of an exterior of the SSD of  FIG. 5A  according to an embodiment. 
         FIG. 5C  provides a different side view of the exterior of the SSD of  FIGS. 5A and 5B  according to an embodiment. 
         FIG. 6A  provides a top view of an exterior of an SSD according to an embodiment. 
         FIG. 6B  provides a side view of the exterior of the SSD of  FIG. 6A  according to an embodiment. 
         FIG. 6C  provides a different side view of the exterior of the SSD of  FIGS. 6A and 6B  according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, numerous specific details are set forth to provide a full understanding of the present disclosure. It will be apparent, however, to one of ordinary skill in the art that the various embodiments disclosed may be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail to avoid unnecessarily obscuring the various embodiments. 
       FIG. 1  shows a cross-section view of solid-state drive (SSD)  100  according to one embodiment. As will be appreciated by those of ordinary skill in the art, the cross-section views of  FIGS. 1 to 3  are not drawn to scale to provide a clearer understanding of the present disclosure. 
     As shown in  FIG. 1 , SSD  100  includes a frame with upper frame portion  118  and lower frame portion  142 , with printed circuit board (PCB)  102  mounted into or on lower frame portion  142 . Upper frame portion  118  and lower frame portion  142  are sized to fit a particular form factor for SSD  100  such as a 2.5 inch form factor. Frame portions  118  and  142  can be comprised of a thermally conductive material to dissipate heat from SSD  100 . Such a frame material can include, for example, an aluminum alloy such as 6061-T6 with a thermal conductivity of 167 W/mK. 
     System on a chip (SOC)  110  is mounted on a bottom side of PCB  102  along with DDR  104 , and flash memories  108  and  114 . As shown in  FIG. 1 , DDR  113  and flash memories  106  and  116  are mounted on a top side of PCB  102 . Although one arrangement of heat generating components is shown in  FIG. 1 , those of ordinary skill in the art will appreciate that the present disclosure is not limited to the specific quantities or a particular arrangement of components on PCB  102 . For example, other embodiments can include more or less of the components shown in  FIG. 1  mounted on a single side of PCB  102 . 
     SOC  110  is an integrated circuit (IC) which can serve as a controller for managing data in SSD  100 . DDRs  113  and  104  are ICs which provide volatile memory for storing data. DDRs  113  and  104  can include, for example, double data rate synchronous dynamic random-access memory (DDR SDRAM) such as DDR SDRAM, DDR2 SDRAM, or DDR3 SDRAM. 
     In the example of  FIG. 1 , flash memories  106 ,  108 ,  120  and  122  provide a non-volatile memory (NVM) for storing data and can include, for example, NAND flash memory. While the example of  FIG. 1  includes flash memory, other embodiments can include any type of solid-state memory. In this regard, such solid-state memory may comprise one or more of various types of memory devices such as Chalcogenide RAM (C-RAM), Phase Change Memory (PC-RAM or PRAM), Programmable Metallization Cell RAM (PMC-RAM or PMCm), Ovonic Unified Memory (OUM), Resistance RAM (RRAM), NAND memory (e.g., single-level cell (SLC) memory, multi-level cell (MLC) memory, or any combination thereof), NOR memory, EEPROM, Ferroelectric Memory (FeRAM), Magnetoresistive RAM (MRAM), other discrete NVM chips, or any combination thereof. 
     SSD  100  also includes thermal interface material (TIM) layers  112 ,  114 ,  116 ,  117  and  119  which provide thermally conductive layers between portions of the frame on one side and components mounted on PCB  102  on another side. TIM layers  112 ,  114 ,  116 ,  117  and  119  can include any thermal interface material or combination of materials known in the art for conducting heat such as a phase change metal alloy (PCMA), graphene, or a silicone based material. In one example, TIM layers  112 ,  114 ,  116 ,  117  and  119  can have a thermal conductivity of 1 to 6 W/mK in a particular direction through the TIM layers. In addition, the TIM layers can include a flexible material or a thermal grease to improve thermal conductivity by filling air gaps due to surface imperfections on frame portions  118  and  142  and on components mounted on PCB  102 . 
     As shown in  FIG. 1 , TIM layer  112  is separated from (i.e., not in direct contact with) TIM layer  117  along the inside surface of lower frame portion  142  by gap  115  which can include air. One reason for separating TIM layers is to reduce heat transfer from a higher heat generating component to other components of SSD  100 . In the example of  FIG. 1 , TIM layer  112  is separated from TIM layer  117  to reduce heat transfer from SOC  110  to DDR  104  and flash memories  108  and  114  since these components may be susceptible to overheating. In addition, SOC  110  ordinarily generates significantly more heat than DDR  104  and flash memories  108  and  114 . For example, when using a peripheral component interconnect exchange (PCIe) standard, SOC  110  may generate 2 to 8 Watts compared to approximately 300 milliwatts generated by DDRs  104  and  113 , and approximately 500 milliwatts generated by flash memories  106 ,  108 ,  120  and  122 . TIM layers  112  and  117  are therefore separated to prevent heat transfer from SOC  110  to other components of SSD  100 . 
     In addition, TIM layers  114  and  117  are separated from each other along the inside surface of lower frame portion  142  by gap  105  to reduce heat which might otherwise conduct between DDR  104  and flash memories  108  and  122 . Similarly, TIM layers  116  and  119  are separated from each other by gap  107  along the inside surface of upper frame portion  118 . 
     The example of  FIG. 1  also includes graphene layers  123  (i.e., graphite sheets) between upper frame portion  118  and lower frame portion  142  which act as a heat spreader and thermally conductive layer between upper frame portion  118  and lower frame portion  142 . Graphene layers  123  ordinarily allow for better heat transfer between upper frame portion  118  and lower frame portion  142 . Due to its high thermal conductivity (approximately 1500 Watts/meter-Kelvin in a parallel x-y plane and approximately 15 Watts/meter-Kelvin in a perpendicular z plane), graphene may also be used in TIM layers  112 ,  114 ,  116 ,  117  and  119 . 
     In other embodiments, graphene layers  123  may be omitted so that frame portions  118  and  142  are in direct contact with each other. In yet other embodiments, graphene layers  123  may be replaced with a different type of thermally conductive layer such as a thermal grease. 
       FIG. 2  shows a cross-section view of a portion of SSD  200  according to an embodiment. As shown in  FIG. 2 , SSD  200  includes frame  218  which is mounted on PCB  202 . SOC  210  is also mounted on PCB  202  via solder balls  212 . PCB  202  includes plane  204  which serves as a thermally conductive layer on one side of SOC  210 . Plane  204  can include copper and may also serve as an electrical conductor for providing a ground or for transmitting a signal between components mounted on PCB  202  such as SOC  210  and memory components (not shown). On the other hand, plane  204  can be a dedicated thermal conduction plane to direct heat transfer from SOC  210  to frame  218  without connecting to other components on PCB  202 . 
     As understood by those of ordinary skill in the art, PCB  202  may include multiple planes. Certain planes, such as plane  204 , may be predisposed for thermal conduction by being thicker than other planes and/or using a material (e.g., copper) with a heavier weight and/or a higher thermal conductivity than materials in other planes. In addition, such thermal conduction planes may be located closer to an outer surface of PCB  202  to better improve heat transfer. 
     As shown in  FIG. 2 , SOC  210  is connected to plane  204  through balls  212  and vias  208  (e.g., microvias). Balls  212  can be part of a ball grid array (BGA) for mounting SOC  210  on PCB  202 . It will be understood by those of ordinary skill in the art that the quantities of balls and vias in  FIG. 2  are used for illustrative purposes and that actual quantities of balls and vias may differ without departing from the scope of the present disclosure. 
     Vias  206  provide a thermally conductive path from plane  204  to frame  218  through graphene layers  223 . In the example of  FIG. 2 , frame  218  is connected to PCB  202  so as to define a first thermally conductive path between the frame and SOC  210 . The first thermally conductive path is illustrated with arrows  222  and  220 , which represent heat being extracted from SOC  210  to frame  218  through balls  212 , vias  208 , plane  204 , vias  206  and graphene layers  223 . As with the thermal conduction planes discussed above, certain vias such as vias  206  and/or vias  208  may be predisposed for thermal conduction by being thicker than other vias and/or by using a material (e.g., copper) with a heavier weight and/or a higher thermal conductivity than materials in other vias. In addition, such thermal conduction vias may be located to better improve heat transfer. 
     On the opposite side of SOC  210 , TIM layer  214  is located between SOC  210  and graphene layer  216  so as to define a second thermally conductive path between frame  218  and SOC  210 . In one embodiment, by having two thermally conductive paths for SOC  210 , it is ordinarily possible to increase heat extraction from SOC  210  to frame  218  where heat from SSD  200  can dissipate from the exterior of frame  218 . 
     The second thermally conductive path is illustrated with arrows  228  which represent heat being extracted from SOC  210  to frame  218  through TIM layer  214  and graphene layer  216 . Since graphene layer  216  extends along a length of frame  218 , graphene layer  216  spreads heat over the interior surface of frame  218  to increase heat transfer to frame  218 . 
     TIM layer  214  can include any thermal interface material or combination of materials known in the art for conducting heat such as a phase change metal alloy (PCMA), graphene, or a silicone based material. In addition, TIM layer  214  can include a flexible material or a thermal grease to improve thermal conductivity by filling air gaps due to surface imperfections on SOC  210 . In other embodiments, TIM layer  214  or graphene layer  216  may be omitted from the second thermally conductive path such that the thermally conductive layer between SOC  210  and frame  218  only includes graphene layer  216  or TIM layer  214 . 
       FIG. 3  shows a cross-section view of a portion of SSD  300  according to an embodiment. As shown in  FIG. 3 , SSD  300  includes upper frame portion  318  and lower frame portion  342  which are mounted on PCB  302 . SOC  310  and flash memory  309  are also mounted on a bottom side of PCB  302  via balls  312 . 
     PCB  302  includes plane  304  which serves as a thermally conductive layer on one side of flash memory  309  and SOC  310 . Plane  304  can include copper and may also serve as an electrical conductor for providing a ground or for transmitting a signal between other components mounted on PCB  302 . 
     As understood by those of ordinary skill in the art, PCB  302  may include multiple planes. In this regard, certain planes, such as plane  304  may be predisposed for thermal conduction as discussed above with reference to  FIG. 2 . In addition, such thermal conduction planes may be located closer to an outer surface of PCB  302  to better improve heat transfer. 
     As shown in  FIG. 3 , plane  304  includes break  321  such that plane  304  is not continuous across its total length. Breaks such as break  321  may serve to direct heat transfer and/or reduce heat transfer from high heat components such as SOC  310  to lower heat components such as flash memory  309 . Other embodiments may also include multiple dedicated thermal conduction planes within PCB  302  to direct heat transfer and/or reduce heat transfer between components mounted on PCB  302 . 
     As shown in  FIG. 3 , flash memory  309  and SOC  310  are connected to plane  304  through balls  312  and vias  308 . In the example of  FIG. 3 , upper frame  318  and lower frame  342  are connected to PCB  302  so as to define thermally conductive paths between the frame and SOC  310 . 
     From flash memory  309 , there are two thermally conductive paths to the frame. The first thermally conductive path from flash memory  309  is illustrated with arrows  320  and  324  which represent heat being extracted from flash memory  309  to frame portions  318  and  342  through balls  312 , vias  308 , plane  304 , vias  306 , and a graphene layer  323 . As noted above with reference to  FIG. 2 , vias  306  and  308  may be predisposed for thermal conduction by being thicker than other vias and/or using a material (e.g., copper) with a heavier weight and/or a higher thermal conductivity than materials in other vias. In addition, such thermal conduction vias may be located to better improve heat transfer. 
     The second thermally conductive path from flash memory  309  is illustrated with arrows  330  which represent heat being extracted from flash memory  309  to lower frame portion  342  through TIM layer  313  and graphene layer  315 . As noted above, by having two thermally conductive paths for a heat generating component, it is ordinarily possible to increase heat extraction from the heat generating component to the frame where heat can dissipate from SSD  300 . 
     In addition to break  321  in plane  304 ,  FIG. 3  shows gap  317  between TIM layers  313  and  314  and between graphene layers  315  and  316 . Gap  317  may include air to reduce conduction of heat between flash memory  309  and SOC  310 . In addition, graphene layers  315  and  316  extend in opposite directions from gap  317  which further directs heat from gap  317  as a result of the high thermal conductivity along the lengths of graphene layers  315  and  316 . 
     As with flash memory  309 , there are two thermally conductive paths from SOC  310  to the frame. The first thermally conductive path from SOC  310  is illustrated with arrows  316  and  322  which represent heat being extracted from SOC  310  to frame portions  318  and  342  through balls  312 , vias  308 , plane  304 , vias  306 , and a graphene layer  323 . As noted above with reference to  FIG. 2 , vias  306  and  308  may be predisposed for thermal conduction by being thicker than other vias and/or using a material (e.g., copper) with a heavier weight and/or a higher thermal conductivity than materials in other vias. In addition, such thermal conduction vias may be located to better improve heat transfer. 
     The second thermally conductive path from SOC  310  is illustrated with arrows  328  which represent heat being extracted from SOC  310  to lower frame portion  342  through TIM layer  314  and graphene layer  316 . As noted above, by having two thermally conductive paths for a heat generating component, it is ordinarily possible to increase heat extraction from the heat generating component to the frame where heat can dissipate from SSD  300 . 
     In the example of  FIG. 3 , upper frame portion  318  includes exterior protrusions such as fins  334  and  336  which have different shapes to improve fluid flow over SSD  300  for convective cooling. The shapes and sizes of the exterior protrusions can vary based on different design considerations. As discussed in more detail below with reference to  FIGS. 4 to 6 , exterior protrusions on the frame ordinarily improve heat transfer with exterior fluids (e.g., air, helium) by increasing a surface area of the frame and/or by adding material to the frame for heat sinking. 
       FIGS. 4A and 4B  provide a top view and a side view of an exterior of SSD  400  according to an embodiment. SSD  400  includes upper frame portion  420  (i.e., top cover) with exterior protrusions such as fins  434  and  436  which define channels between the exterior protrusions. The exterior protrusions ordinarily improve heat transfer from SSD  400  to an ambient fluid such as air or helium by increasing the exterior surface area of the frame. 
     In the example of  FIGS. 4A and 4B , a fluid flows over SSD  400  to provide convective cooling. In addition, the extra surface area of the exterior protrusions increases heat dissipation from SSD  400  when fluid is not flowing over SSD  400 . The exterior protrusions also add mass to the frame for heat sinking. 
     Although the exterior frame protrusions in  FIGS. 4A and 4B  are depicted as fins having a rectangular shape, other embodiments can include exterior protrusions having a different shape such as a cylindrical shape (i.e., pins) to increase the surface area and/or mass of the frame. 
     Upper frame portion  420  and/or lower frame portion  418  can be etched to remove coatings from the frame that may otherwise hinder thermal conductivity. In particular, SSD  400  can be etched at specific locations where SSD  400  is to be mounted so as to provide thermally conductive paths from the exterior of SSD  400 . Such etching can be performed with an etching laser or a chemical removal of surface coatings. 
     As shown in  FIGS. 4A and 4B , SSD  400  includes raised portion  440  which provides an area for locating thermally conductive label  438 . Labels may be provided as part of a standard for indicating characteristics of a data storage device on its exterior. Thermally conductive label  438  can be made of aluminum or another material having a relatively high (non-insulating) thermal conductivity to dissipate heat from SSD  400  in an area which might otherwise not dissipate much heat with a conventional label. Label  438  may also include a thermally conductive adhesive for affixing label  438  to SSD  400  while allowing for heat dissipation. 
     Raised portion  440  also serves to house components in SSD  400  which would not otherwise fit under upper frame portion  420 . By housing taller components under raised portion  440 , exterior protrusions can be added to areas around raised portion  440  without increasing an overall height of SSD  400 . In this regard, raised portion  440  may also be used to house stacked PCBs within SSD  400  to achieve a smaller footprint for SSD  400  while allowing room for exterior protrusions within an overall height specification for SSD  400 . 
     As shown in  FIGS. 4A and 4B , raised portion  440  includes ramp  442  on its right side so as to reduce the turbulence of fluid flowing raised portion  440 . Ramp  442  includes exterior protrusions on its top surface and can be positioned to receive a flow from a particular direction such as from a fan (not shown) outside of SSD  400 . In  FIGS. 4A and 4B , fluid flows from the right side of SSD  400  toward the left side of SSD  400 . Other embodiments may include other modifications to frame portions such as lower frame portion  418  or upper frame portion  420  to increase fluid flow over SSD  400  and thereby increase convective cooling of SSD  400 . 
       FIGS. 5A, 5B and 5C  provide top and side views of an exterior SSD  500  according to an embodiment. SSD  500  includes exterior protrusions such as fins  534  and  536  which define channels on upper frame portion  520  between the fins. In comparison to the fins of SSD  400 , the fins of SSD  500  are longer in a direction of fluid flow over SSD  500 . The longer fins of SSD  500  ordinarily reduce turbulence and increase the fluid flow over SSD  500  to increase heat dissipation from SSD  500 . 
     SSD  500  also includes a lower frame portion  518 , a thermally conductive label  538 , a raised portion  540 , and a ramp  542 . As shown in  FIG. 5A , exterior protrusions such as fin  536  cut into ramp  542 . As with SSD  400  of  FIGS. 4A and 4B , the frame of SSD  500  may also be etched to remove coatings from the frame that may hinder thermal conductivity. 
       FIGS. 6A, 6B and 6C  provide top and side views of an exterior of SSD  600  according to an embodiment. SSD  600  includes exterior protrusions such as fins  634 ,  636 , and  642  which define channels on upper frame portion  620  between the fins. Unlike SSD  500 , the exterior protrusions of SSD  600  define channels in two directions. Although the fins of SSD  600  are longer in a direction of fluid flow over SSD  600 , channels are provided along a width of the fins to increase a surface area of upper frame portion  620  and/or improve convective cooling from a fluid flow in a second direction. 
     As shown in  FIGS. 6A, 6B and 6C , SSD  600  also includes lower frame portion  618 , raised portion  640  and thermally conductive label  638 . 
     The foregoing description of the disclosed example embodiments is provided to enable any person of ordinary skill in the art to make or use the embodiments in the present disclosure. Various modifications to these examples will be readily apparent to those of ordinary skill in the art, and the principles disclosed herein may be applied to other examples without departing from the spirit or scope of the present disclosure. The described embodiments are to be considered in all respects only as illustrative and not restrictive and the scope of the disclosure is, therefore, indicated by the following claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.