# Patent

## Title
Embossed heat spreader

## Abstract

One embodiment of the present invention sets forth a heat spreader module for dissipating thermal heat generated by electronic components. The assembly comprises a printed circuit board (PCB), electronic components disposed on the PCB, a thermal interface material (TIM) thermally coupled to the electronic components, and a heat spreader plate thermally coupled to the TIM. The heat spreader plate includes an embossed pattern. Consequently, surface area available for heat conduction between the heat spreader plate and surrounding medium may be increased relative to the prior art designs.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims benefit of U.S. Provisional Patent Application Ser. No. 61/014,740 filed Dec. 18, 2007, which is hereby incorporated herein by reference in its entirety.


BACKGROUND OF THE INVENTION
1. Field of the Invention
Embodiments of the present invention relate generally to electronic systems and, more specifically, to design of a heat spreader for memory modules.
2. Description of the Related Art
In modern computing platforms, there is provision for population of semiconductor memory using one or more dual inline memory modules (DIMMs). One of the problems commonly encountered during integration of memory modules into a computer system is heat dissipation. The ability to maintain the temperature of components on a module within the required operating range depends on many factors including module surface area, airflow velocity, temperature of incoming air, location of the module in the system and presence or absence of adjacent modules. Designers of electronic systems make tradeoffs between these variables to achieve acceptable system thermal performance while keeping cost to a minimum.
Early designs have employed heat sinks and custom-designed enclosures in an attempt to address the heat dissipation problem. While designs employing heat spreaders have been used in systems to date, the inexorable demand for more, higher speed, and higher density memory modules have caused memory power dissipation requirements to increase faster than improvements in heat sink/heat spreader performance. Oftentimes, some designs are capable of dissipating the heat, but fall short with respect to the mechanical integrity of the module under shipping, handling, and insertion/removal. Other designs may satisfy the mechanical integrity constraints, but fall short in the area of heat dissipation. Still other designs may achieve both the heat dissipation and mechanical requirements, but are impractically expensive.
Another major difficulty in a conventional heat spreader design is that of achieving acceptable thermal performance independent of the large changes in air flow velocity caused by the variation of spacing between modules depending on which modules are installed in the system. Thermal solutions that work well with all modules present in the system often do not perform acceptably with only a single module present, due to the reduced air velocity and tendency of the airflow to bypass around the module.
As the foregoing illustrates, what is needed in the art is a heat spreader design that overcomes these and/or other problems associated with the prior art.
SUMMARY OF THE INVENTION
One embodiment of the present invention sets forth a heat spreader for dissipating thermal heat generated by electronic components. The heat spreader is utilized as an assembly comprising a printed circuit board (PCB), electronic components disposed on the PCB, a thermal interface material (TIM) thermally coupled to the electronic components, and a heat spreader plate thermally coupled to the TIM. Furthermore, the heat spreader plate includes an embossed pattern.
Another embodiment of the present invention sets forth a heat spreader module for dissipating thermal heat generated by electronic components comprising a first PCB, the electronic components disposed on the first PCB, a TIM thermally coupled to the electronic components, and a second PCB thermally coupled to the TIM and adapted to dissipate thermal heat generated by the electronic components.
One advantage of the disclosed heat spreader is that surface area available for heat conduction between the heat spreader plate and surrounding medium may be increased relative to the prior art designs. The embossed pattern may be advantageously adjusted to achieve large surface area and at the same time enhance the rigidity of the heat spreader, allowing thinner material to be used effectively. The embossed pattern may be produced with a simple stamping operation.



BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
FIG. 1 illustrates an exploded view of a heat spreader module, according to one embodiment of the present invention;
FIG. 2 illustrates an assembled view of a heat spreader module, according to one embodiment of the present invention;
FIGS. 3A through 3C illustrate shapes of a heat spreader plate, according to different embodiments of the present invention;
FIG. 4 illustrates a heat spreader module with open-face embossment areas, according to one embodiment of the present invention;
FIG. 5 illustrates a heat spreader module with patterned cylindrical pin array, according to one embodiment of the present invention;
FIG. 6 illustrates an exploded view of a module using PCB heat spreader plates on each face, according to one embodiment of the present invention;
FIG. 7 illustrates a PCB stiffener with a pattern of through-holes, according to one embodiment of the present invention;
FIG. 8A illustrates a PCB stiffener with a pattern of through holes allowing air flow from inner to outer surfaces, according to one embodiment of the present invention;
FIG. 8B illustrates a PCB stiffener with a pattern of through holes with a chimney, according to one embodiment of the present invention;
FIG. 9 illustrates a PCB type heat spreader for combining or isolating areas, according to one embodiment of the present invention;
FIGS. 10A-10D illustrate heat spreader assemblies showing air flow dynamics, according to various embodiments of the present invention; and
FIGS. 11A-11D illustrate heat spreaders for memory modules, according to various embodiments of the present invention.



DETAILED DESCRIPTION
Embodiments of the present invention relate to design of a heat spreader (also commonly referred to as a “heat sink”) for memory modules. They may also be applied more generally to electronic sub-assemblies that are commonly referred to as add-in cards, daughtercards, daughterboards, or blades. These are sub-components that are attached to a larger system by a set of sockets or connectors and mechanical support components collectively referred to as a motherboard, backplane, or card cage. Note that many of these terms are sometimes hyphenated in common usage, i.e. daughter-card instead of daughtercard. The common characteristic linking these different terms is that the part of the system they describe is optional, i.e. may or may not be present in the system when it is operating, and when it is present it may be attached or “populated” in different locations which are functionally identical or nearly so but result in physically different configurations with consequent different flow patterns of the cooling fluid used within the system.
FIG. 1 illustrates an exploded view of a heat spreader module 100, according to one embodiment of the present invention. As shown, the heat spreader module 100 includes a printed circuit board (PCB) 102 to which one or more electronic components 104 are mounted. As described below, in various embodiments, the electronic components 104 may be disposed on both sides or only one side of the PCB 102. As is readily understood, the operation of the electronic components produces thermal energy, and it is understood in the art that some means for dissipating the thermal energy must be considered in any physical design using electronic components.
In the embodiment shown in FIG. 1, the heat generated by the electronic components 104 is dissipated by virtue of physical contact to the electronic components 104 by one or more thermally conductive materials. As shown, the electronic components 104 are in physical contact with a layer of thermally conductive material that serves as a thermal interface material (referred to as “TIM”) 106. The TIM 106 is, in turn, in contact with a heat spreader plate 108. Both the TIM 106 and the heat spreader plate 108 are thermally conductive materials, although there is no specific value of thermal conductivity coefficients or thermally conductive ratios required for the embodiments to be operable.
The TIM 106 may come in the form of a lamination layer or sheet made of any from a group of materials including conductive particle filled silicon rubber, foamed thermoset material, and a phase change polymer. Also, in some embodiments, the materials used as gap fillers may also serve as a thermal interface material. In some embodiments, the TIM 106 is applied as an encasing of the electronic components 104 and once applied the encasing may provide some rigidity to the PCB assembly when adhesively attached both to the components and the heat spreader. In an embodiment that both adds rigidity to the package and facilitates disassembly for purposes of inspection and re-work, the TIM 106 may be a thermoplastic material such as the phase change polymer or a compliant material with a non-adhesive layer such as metal foil or plastic film.
The heat spreader plate 108 can be formed from any of a variety of malleable and thermally conductive materials with a low cost stamping process. In one embodiment, the overall height of the heat spreader plate 108 may be between 2 mm and 2.5 mm. In various embodiments, the heat spreader plate 108 may be flat or embossed with a pattern that increases the rigidity of the assembly along the long axis.
In one embodiment, the embossed pattern may include long embossed segments 115a, 115b that run substantially the entire length of the longitudinal edge of the heat spreader plate. In another embodiment, in particular to accommodate an assembly involving c-clips 114, the embossed pattern may include shorter segments 116. As readily envisioned, and as shown, patterns including both long and short segments are possible. These shorter segments are disposed as to provide location guidance for the retention clips. Furthermore, the ends of the segment of embossing, whether a long embossed segment or a shorter segment, may be closed (as illustrated in FIG. 1) or may be open (as illustrated in FIG. 4).
In designs involving embossed patterns with closed ends, those skilled in the art will readily recognize that the embossing itself increases the surface area available for heat conduction with the surrounding fluid (air or other gases, or in some cases liquid fluid) as compared with a non-embossed (flat) heat spreader plate. The general physical phenomenon exploited by embodiments of this invention is that thermal energy is conducted from one location to another location as a direct function of surface area. Embossing increases the surface area available for such heat conduction, thereby improving heat dissipation. For example, a stamped metal pattern may be used to increase the surface area available for heat conduction.
As a comparison, Table 1 below illustrates the difference in surface area, comparing one side of a flat heat spreader plate to one side of an embossed heat spreader plate having the embossed pattern as shown in FIG. 1.










TABLE 1






Surface area





(flat heat
Surface area (embossed
Increase in


Characteristic
spreader)
heat spreader)
surface area (%)







Embossed
3175 mm2
3175(+331) mm2
10.6%









In some embodiments, the PCB 102 may have electrical components 104 disposed on both sides of the PCB 102. In such a case, the heat spreader module 100 may further include a second layer of TIM 110 and a second heat spreader plate 112. All of the discussions herein with regard to the TIM 106 apply with equal force to the TIM 110. Similarly, all of the discussions herein with regard to the heat spreader plate 108 apply with equal force to the heat spreader plate 112. Furthermore, the heat spreader plate(s) may be disposed such that the flat side (concave side) is toward the electrical components (or stated conversely, the convex side is away from the electrical components). In various embodiments, a heat spreader may be disposed only on one side of the PCB 102 or be disposed on both sides.
In one embodiment, the heat spreader plate 108 may include perforations or openings (not shown in FIG. 1) allowing interchange of the cooling fluid between inner and outer surfaces (where the term “inner surface” refers to the surface that is closest to the electronic components 104). These openings may be located at specific positions relative to an embossed pattern such that flow over the opening is accelerated relative to the average flow velocity. Alternately, the openings may be located at the top of narrow protrusions from the surface such that they are outside the boundary layer of slower fluid velocity immediately adjacent to the surface. In either case, the TIM 110 may be designed in coordination with the heat spreader plate 108 to ensure that the TIM 110 also allows fluid flow from beneath the heat spreader plate 108 out through the holes. This can be ensured by applying a liquid TIM to either the heat spreader plate 108 or the electronic components 104 using a printing or transfer process which only leaves the TIM 110 on the high points of the surface and does not block the holes of the heat spreader plate 108 or the spaces between the electronic components 104. Alternately a tape or sheet TIM can be used where the TIM material itself allows passage of fluid through it, or the sheet may be perforated such that there are sufficient open passages to ensure there is always an open path for the fluid through the TIM 110 and then the heat spreader plate 108.
In another embodiment, the heat spreader plate 108 may be formed as a unit from sheet or roll material using cutting (shearing/punching) and deformation (embossing/stamping/bending) operations and achieves increased surface area and/or stiffness by the formation of fins or ridges protruding out of the original plane of the material, and/or slots cut into the material (not shown in FIG. 1). The fins may be formed by punching a “U” shaped opening and bending the resulting tab inside the U to protrude from the plane of the original surface around the cut. The formation of the U shaped cut and bending of the resulting tab may be completed as a single operation for maximum economy. The protruding tab may be modified to a non-planar configuration: for example an edge may be folded over (hemmed), the entire tab may be twisted, the free edge opposite the bend line may be bent to a curve, a corner may be bent at an angle, etc.
In another embodiment, the heat spreader plate 108 may be manufactured by any means which incorporates fins or ridges protruding into the surrounding medium or slots cut into the heat spreader (not shown in FIG. 1), where the fins or slots are designed with a curved shape (i.e. an airfoil) or placed at an angle to the incoming fluid so as to impart a velocity component to the impinging fluid that is in a plane parallel or nearly parallel to the base of the heat spreader (contact surface with the TIM or electronic components) and at right angles to the original fluid flow direction. The sum of this velocity component with the original linear fluid velocity vector creates a helical flow configuration in the fluid flowing over the heat spreader which increases the velocity of the fluid immediately adjacent to the heat spreader and consequently reduces the effective thermal resistance from the heat spreader to the fluid. Heat spreaders which are designed to create helical flow are referred to herein as “angled fin heat spreaders,” and the fins positioned at an angle to the original fluid flow direction are referred to herein as “angled fins”, without regard to the exact angle or shape of the fins which is used to achieve the desired result. The angled fins may be continuous or appear as segments of any length, and may be grouped together in stripes aligned with the expected air flow or combined with other bent, cut, or embossed features.
In another embodiment, two or more memory modules incorporating angled fin heat spreader plates are placed next to each other with the cooling fluid allowed to flow in the gaps between modules. When angled fin heat spreaders with matching angles (or an least angles in the same quadrant i.e. 0-90, 90-180, etc.) are used on both faces of each module and consequently both sides of a gap, the fins on both heat spreaders contribute to starting the helical flow in the same direction and the angled fins remain substantially parallel to the local flow at the surface of each heat spreader plate down the full length of the module.
An additional benefit which may be achieved with the angled fins is insensitivity to the direction of air flow—cooling air for the modules is commonly supplied in one of three configurations. The first configuration is end-to-end (parallel to the connector). The second configuration is bottom-to-top (through holes in the backplane or motherboard). The third configuration is in both ends and out the bottom or top. The reverse flow direction for any of these configurations may also occur. If the fin angle is near 45 degrees relative to the edges of the module, any of the three cases will give similar cooling performance and take advantage of the full fin area. Typical heat spreader fins designed according to the present art are arranged parallel to the expected air flow for a single configuration and will have much worse performance when the air flow is at 90 degrees to the fins, as it would always be for at least one of the three module airflow cases listed above. The angle of the fins does not have to be any particular value for the benefit to occur, although angles close to 45 degrees will have the most similar performance across all different airflow configurations. Smaller or larger angles will improve the performance of one flow configuration at the expense of the others, but the worst case configuration will always be improved relative to the same case without angled fins. Given this flexibility it may be possible to use a single heat spreader design for systems with widely varying airflow patterns, where previously multiple unique heat spreader designs would have been required.
In yet another embodiment, the heat spreader plate 108 may be manufactured by any means which includes a mating surface at the edge of the module opposite the connector (element 1108 in FIG. 11A) to allow for heat conduction to an external heat sink or metal structure such as the system chassis. The mating surface will typically be a flat bent tab and/or machined edge designed to lie within a plane parallel to the motherboard or backplane and perpendicular to the module PCB and heat spreader seating plane. Other mating surface features which facilitate good thermal conduction are possible, such as repeating parallel grooves, flexible metal “fingers” to bridge gaps, etc. Thermal interface material or coatings may be applied to the module to improve conductivity through the surface. The heat spreader plate 108 may include alignment features (not shown in FIG. 1) to ensure that the mating surfaces of the heat spreader plates on both sides of a module lie within the same plane to within an acceptable tolerance. These alignment features may include tabs or pins designed to contact one or more edges or holes of the PCB 102, or tabs or pins which directly contact the heat spreader plate 108 on the other face of the module.
In another embodiment, the heat spreader plate 108 may be applied to the electronic components 104 (especially DRAM) in the form of a flexible tape or sticker (i.e. the heat spreader has negligible resistance to lengthwise compressive forces). TIM 110 may be previously applied to the electronic components 104 or more commonly provided as a backing material on the tape or sticker. In this embodiment the heat spreader plate 108 is flexible enough to conform to the relative heights of different components and to the thermal expansion and contraction of the PCB 102. The heat spreader plate 108 may be embossed, perforated, include bent tabs, etc., to enhance surface area, allow air passage from inner to outer surfaces, and reduce thermal resistance in conducting heat to the fluid.
FIG. 2 illustrates an assembled view of a heat spreader module, according to one embodiment of the present invention. The heat spreader module is accomplished using commonly available electronics manufacturing infrastructure and assembly practices. Fastening mechanisms such as the C-clip shown in this embodiment are employed to provide sufficient clamping force and mechanical integrity while minimizing obstruction to thermal dissipation performance. Often thermal interface materials are pressure sensitive and require controlled force application in order to optimize thermal conduction properties. Fastening mechanisms such as the c-clips shown can be designed to maximize heat spreader performance while complying with industry standards for form factor and mechanical reliability
In the discussions above, and as shown in FIG. 1, the heat spreader plate 108 may be substantially planar. In other embodiments, the heat spreader plate 108 may be formed into a shape conforming to the contour of the components on the underlying circuit assembly utilizing the stamping or other low cost forming operation. FIGS. 3A through 3C illustrate shapes of a heat spreader plate, according to different embodiments of the present invention. Following the example shown in FIGS. 3A and 3B, the undulation may form an alternating series of high-planes and low-planes. In a preferred embodiment, the high-plane portions and the low-plane portions follow the terrain of the shapes of the components mounted to the PCB 102.
In yet another embodiment, the pattern of embossing substantially follows the undulations. That is, for example, each of the high-plane and low-plane regions may be embossed with one or more embossed segments 302 substantially of the length of the planar region, as shown in FIG. 3C.
FIG. 4 illustrates a heat spreader module 400 with open face embossment areas, according to one embodiment of the present invention. In designs involving embossed patterns with open faces, the ends of the embossed segments may be sufficiently expanded to facilitate more heat spreader surface area contact with the surrounding fluid (air or other gases, or in some cases liquid fluid) as compared with closed-ended embossed segments. These open face embossments may significantly increase thermal performance by enabling exposure of the concave side of the heat spreader plate in addition to the convex while not significantly blocking the available channel area for air flow.
As a comparison, Table 2 below shows the difference in surface area, comparing one side of a flat heat spreader plate to one side of an embossed heat spreader plate having the embossed pattern shown in FIG. 4.










TABLE 2






Surface area
Surface area
Increase



(embossed
(embossed
in



segments with
segments with open 
surface


Characteristic
closed ends)
ends)
area (%)







Open end Embossed
3175 mm2
3175 + 2118 mm2
67%









FIG. 5 illustrates a heat spreader module 500 with a patterned cylindrical pin array area, according to one embodiment of the present invention. In designs involving such pin patterns the surface area exposed to air flow can be increased merely by increasing the density of the protrusions. The protrusions may be formed by forging or die-casting.
FIG. 6 illustrates an exploded view of a module 600 using PCB heat spreader plates 640 on each face, according to one embodiment of the present invention. This embodiment consists of a heat spreader which is manufactured as an additional separate PCB for each face of the module (or using similar processes to a PCB, i.e. plating metal or thermally conductive material onto the surface of a substantially less conductive substrate). As shown, the module 600 includes electronic components mounted on a two-sided PCB 610. It must be noted that, typically, the heat spreader plates 640 require mechanical stiffness to distribute the clamping forces from localized contact points using fasteners 650 (also referred to herein as clamps and/or clips) to a TIM 630 at each heat source (e.g., ASIC, DRAM, FET, etc). Given a layout with a relatively low concentration of heat sources (e.g. on a DIMM), more, and/or thicker heat spreader material (e.g. copper or aluminum) is required to provide mechanical stiffness than would be needed simply to carry the heat away. The PCB heat spreader plates 640 use a non-metallic core material to provide the required stiffness in place of the usual solid copper or aluminum heat spreader plates. The PCB heat spreader plates 640 might have devices 635 mounted on one or both sides. Some examples of the PCB heat spreader plates are described in greater detail in FIGS. 7, 8A, and 8B. The entire assembly 600 may be squeezed together with the fastener 650, applying forces on the faces of the assembly. Use of a compressible TIM permits the PCB heat spreader plates 640 to deform somewhat under the clamping pressures while still maintaining sufficient thermal coupling. In some embodiments, the PCB heat spreader plates 640 may be formed of a fiberglass or phenolic PCB material and may employ plated through-holes to further distribute heat.
The heat spreader module 600 may utilize a low cost material to fabricate the PCB heat spreader plates 640. The low cost material may have low thermal conductivity as a “core” to provide the desired mechanical properties (stiffness, energy absorption when a module is dropped), while a thin metal coating on one or both sides of PCB(s) 640 provides the required thermal conductivity. Thermal conduction from one face of the core to the other is provided by holes drilled or otherwise formed in the core which are then plated or filled with metal (described in greater detail in FIG. 7). The advantage of this method of construction is that the amount of metal used can be only the minimum that is required to provide the necessary thermal conductivity, while the mechanical properties are controlled independently by adjusting the material properties and dimensions of the core. The use of standard PCB manufacturing processes allows this type of heat spreader to include patterned thermally conductive features that allow some parts of the heat spreader module 600 to be effectively isolated from others. This allows different parts of the heat spreader module 600 to be maintained at different temperatures, and allows measurement of the temperature at one location to be taken using a sensor attached elsewhere (described in greater detail in FIG. 9).
FIG. 7 illustrates a PCB stiffener 700 with a pattern of through-holes 710, according to one embodiment of the present invention. The PCB stiffener 700 may be used as the PCB heat spreader plates 640 illustrated in FIG. 6. As shown, plated through holes 710 may be purposefully formed through the PCB 700. In such an embodiment, there may be many variations. For example, a thickness 720 of the PCB 700 may be selected according to the mechanical stiffness properties of the PCB material. Furthermore, a size of the through-holes 710, thickness of the walls between the through-holes 710, dimensions and composition of the though-hole plating, and surface plating thickness 730 may affect the thermal spreading resistance. The through-holes 710 may be plated shut, or be filled with metal (e.g. copper) or non-metal compositions (e.g. epoxy). Given these independently controlled variables, various embodiments support separate tuning of mechanical stiffness (e.g. based on PCB thickness and materials used, such as, for example phenolic, fiberglass, carbon fiber), through-thickness conductivity (e.g. based on number and size of the plated through-holes 710), and planar conductivity (e.g. based on thickness of copper foil and plating).
Adapting a PCB to be used as the heat spreader minimizes coefficient of thermal expansion (CTE) mismatch between the heat spreader (e.g., the PCB 640 or the PCB stiffener 700) and the core PCB (e.g., the PCB 610) that the devices being served are attached to (e.g., the electronic components 620). As a result, warpage due to temperature variation may be minimized, and the need to allow for relative movement at the interface between the electronic components and the heat spreader may be reduced.
FIG. 8A illustrates a PCB stiffener 870 with a pattern of through holes allowing air flow from inner to outer surfaces, according to one embodiment of the present invention. The PCB stiffener 870 may be used as the PCB heat spreader plates 640 illustrated in FIG. 6. As shown in FIG. 8A, unfilled plated through-holes 810 may be used to allow the airflow from the space under the PCB 870 to pass out through the unfilled holes due to the air pressure differential. Top surface 825 and bottom surface (not shown in FIG. 8A) are thermally conductive surfaces, and acting together with the TIM 820 contribute to reducing effective total thermal resistance of the PCB 870, thus improving the heat spreading effectiveness of the assembly.
In fact, and as shown in FIG. 8B, multiple layers of substrate material used to make the PCB 870 may be included and then some thickness (e.g. one or more layers) of the substrate material can be removed by acid or melting to leave the via structures as hollow pins 830 protruding above the surface of the remaining layers. Because the top end 840 of the hollow pins 830 is out of the boundary layer of slow air near the surface 850, there is a “smokestack effect” which increases the air pressure differential between the pressure due to airflow 806 relative to the pressure due to airflow 860, leading to increased airflow through the hollow pins 830, and thus reducing the total thermal resistance of the heat spreader to the air.
FIG. 9 illustrates a heat spreader for combining or isolating areas, according to one embodiment of the present invention. As shown, thermally conductive materials may be shaped into traces 910 disposed on a substrate 920 so as to thermally combine certain areas (and/or thermally separate others) so that a “hot” component 930 does not excessively heat immediately adjacent components 940. Additionally, any of the traces etched into the board might be used to carry temperature information from one location to another, for example, to measure the temperature of a hot component with a thermal diode that makes contact with the heat spreader at another location on the board. In effect, the board is used as a “thermal circuit board” carrying temperatures instead of voltages. This works especially well in situations where the thermal conductivity of the transmitting material is greater than that of material forming the PCB. In embodiments demanding a separate area for components with different temperature limits or requiring separate temperature measurement, the aforementioned techniques for distributing or transmitting temperatures, or thermally combining or thermally isolating areas might be used.
The embodiments shown in FIGS. 6 through 9 may be employed in any context of heat spreader module designs, including the contexts of FIGS. 1-5.
FIGS. 10A-10D illustrate heat spreader assemblies showing air flow dynamics, according to various embodiments of the present invention. As shown in FIGS. 10A and 10C, in some cases functioning modules (e.g. DIMMS on motherboards) may be seated in a socket electrically connected to the motherboard, and in cases where multiple DIMMS are arranged in an array as shown, the one or more DIMMS may be disposed in an interior position, that is, between one or more other sockets. FIG. 10B shows a side view of such a situation. As may be seen, the airflow over the surfaces of the interior functioning module is unshaped. According to one embodiment of the present invention, in such a case, the airflow to the one or more interior DIMMS may be made more laminar in some sections, or made more turbulent in some sections or otherwise enhanced by populating the neighboring sockets with a shaped stand-off card, as shown in FIGS. 10C and 10D. As may be seen, the airflow over the surfaces of the interior functioning module is shaped as a consequence of the shaped stand-off card. Of course, the shaped stand-off card might be as simple as is shown in FIG. 10D, or it might include a funnel shape, or a convex portion or even an airfoil shape.
FIGS. 11A-11D illustrate various embodiments of heat spreaders for a memory module. The embodiments shown in FIGS. 11A through 11D may be employed in any context, including the contexts of FIGS. 1-10D. In fact, memory module 1101 depicts a PCB or a heat spreader module assembly in the fashion of assembly 100, or 200 or 500, or 600, or any other PCB assembly as discussed herein. In one embodiment, the memory module 1101 comprises a DIMM. Moreover the element 1103 depicts an embossing (e.g. 116) or pin fin (e.g. 510) or even a hollow pin 830. In some embodiments, a memory module 1101 may be an assembly or collection of multiple memory devices, or in some embodiments, a memory module 1101 may be embodied as a section on a PCB or motherboard, possibly including one or more sockets. FIG. 11A shows a group of memory modules 1101 enclosed by a duct 1102. In the exemplary embodiments shown in FIG. 11A-11D, the memory modules section might be mounted on a motherboard or other printed circuit board, and relatively co-located next to a processor, which processor might be fitted with a heat sink 1106. This assembly including the memory module(s), processor(s) and corresponding heat sinks might be mounted on a motherboard or backplane 1109, and enclosed with a bottom-side portion 1107 of a housing (e.g., computer chassis or case). The duct 1102 encloses the memory module section, and encloses a heat sink assembly 1104 disposed atop the memory modules 1101, possibly including TIM 1108 between the memory modules 1101 and the heat sink assembly 1104. FIG. 11B shows a side view of a section of a motherboard, and depicting the memory modules 1101 in thermal contact with a top-side portion 1114 of a housing, possibly including TIM 1110. FIG. 11C shows a memory module enclosed by a duct 1102. The duct 1122 encloses the memory module section. The heat sink assembly 1104 may be disposed atop the duct 1122, possibly including TIM 1120 between the memory modules 1101 and the duct 1122. FIG. 11D shows a memory module enclosed by a duct. This embodiment exemplifies how heat is carried from the DIMMS to the bottom-side portion 1107 of the housing through any or all structural members in thermal contact with the bottom-side of the housing.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

## Claims

1. An apparatus comprising:
a printed circuit board (PCB);
electronic components disposed on the PCB;
a thermal interface material (TIM) thermally coupled to the electronic components; and
a heat spreader plate with a surface thermally coupled to the TIM, the surface of the heat spreader plate having edges and an embossed pattern with embossed segments having open ends; wherein
a portion of the heat spreader plate extends between each open end and a closest one of the edges.

2. The apparatus of claim 1, wherein the embossed pattern comprises one or more long embossed segments that run substantially an entire length of a longitudinal one of the edges of the surface of the heat spreader plate and two or more short embossed segments such that, cumulatively, the two or more short embossed segments run substantially the entire length of the longitudinal one of the edges of the surface of the heat spreader plate.

3. The apparatus of claim 2, wherein the one or more long embossed segments and the two or more short embossed segments have open ends.

4. The apparatus of claim 1, wherein the open ends are expanded.

5. The apparatus of claim 2, wherein the two or more shorter segments are disposed so as to provide location guidance for one or more retention clips.

6. The apparatus of claim 2, wherein the two or more shorter segments comprises two or more groups of substantially parallel shorter segments, wherein each group of substantially shorter segments is separated from another one of the groups of substantially shorter segments by a part of the heat spreader plate.

7. The apparatus of claim 1, wherein each embossed segment has a concave side and a convex side, wherein the convex side faces away from the electronic components.

8. The apparatus of claim 1, wherein the embossed segments having open ends are stamped.

9. The apparatus of claim 8, wherein a surface of the heat spreader plate that has been stamped to create the embossed segments is physically in contact with the TIM.

10. The apparatus of claim 1, wherein the heat spreader plate includes a concave side and a convex side, and the convex side is facing away from the electronic components.

11. The apparatus of claim 1, wherein a shape of the heat spreader plate is substantially planar.

12. The apparatus of claim 1, wherein a shape of the heat spreader plate conforms to a contour of the electronic components.

13. The apparatus of claim 12, wherein the shape of the heat spreader plate comprises an alternating series of high planes and low planes.

14. The apparatus of claim 12, wherein the embossed pattern follows the shape of the heat spreader plate.

15. The apparatus of claim 1, further comprising a fastening mechanism adapted to clamp the PCB, the electronic components, the TIM, and the heat spreader plate.

16. The apparatus of claim 15, wherein the fastening mechanism comprises one or more C-clips.

17. The apparatus of claim 1, wherein the embossed pattern comprises one or more long embossed segments that run substantially an entire length of a longitudinal edge of the heat spreader plate.

18. The apparatus of claim 1, wherein the embossed pattern comprises two or more short embossed segments such that, cumulatively, the two or more short embossed segments run substantially an entire length of a longitudinal edge of the heat spreader plate.

19. The apparatus of claim 18, wherein the two or more short embossed segments are adapted to provide location guidance for retention clips.

20. The apparatus of claim 1, wherein the TIM comprises a lamination layer.

21. The apparatus of claim 20, wherein the lamination layer comprises at least one of a conductive particle filled silicon rubber, a foamed thermoset material, a phase change polymer, and a gap filler material.

22. The apparatus of claim 1, wherein the TIM provides an encasing for the electronic components.

23. The apparatus of claim 22, wherein the TIM comprises a phase change polymer or a material with a non-adhesive layer.

24. The apparatus of claim 23, wherein the material with a non-adhesive layer comprises a metal or a plastic film.

25. The apparatus of claim 1, wherein a thickness of the heat spreader plate is between 2 millimeters and 2.5 millimeters.

26. The apparatus of claim 1, wherein the TIM is shaped to thermally connect a first area of the PCB to a second area of the PCB, wherein the first area and the second area do not overlap.

27. The apparatus of claim 26, wherein thermal conductivity of the TIM is higher than thermal conductivity of a material comprising the PCB.

28. The apparatus of claim 1, wherein the heat spreader plate comprises openings adapted to allow interchange of a cooling fluid between inner and outer surfaces of the heat spreader plate.

29. The apparatus of claim 28, wherein the openings are disposed at specific positions relative to the embossed pattern such that air flow over the openings is accelerated relative to the average air flow velocity.

30. The apparatus of claim 1, wherein the heat spreader plate comprises a mating surface adapted to allow for heat conduction to an external heat sink or a metal structure.

31. The apparatus of claim 30, wherein the metal structure comprises a system chassis.

32. The apparatus of claim 30, wherein the apparatus is a part of a memory device comprising a motherboard, and the mating surface comprises a flat bent tab and/or machined edge designed to lie within a plane parallel to the motherboard and perpendicular to the PCB and a heat spreader plate seating plane.

33. The apparatus of claim 1, wherein the heat spreader plate comprises a flexible tape or a sticker adapted to have negligible resistance to lengthwise compressive forces acting on the heat spreader plate.

34. The apparatus of claim 1, wherein the apparatus is a part of a memory device.

35. The apparatus of claim 34, wherein the memory device is arranged in a stack with other memory devices.

36. The apparatus of claim 34, wherein the memory device comprises a dynamic random access memory chip.

37. The apparatus of claim 1, wherein the apparatus is included in a dual in-line memory module (DIMM).

38. The apparatus of claim 37, wherein:
the DIMM is mounted into a DIMM socket included in an assembly comprising multiple DIMMS and a motherboard, and the DIMM socket is electrically connected to the motherboard.

39. The apparatus of claim 1, wherein the apparatus is included within a computing device.