WO2008082042A1

WO2008082042A1 - Cooling system for memory module

Info

Publication number: WO2008082042A1
Application number: PCT/KR2007/002797
Authority: WO
Inventors: Eu-Gene Choi
Original assignee: Top Thermal Management Co, . Ltd.
Priority date: 2006-12-29
Filing date: 2007-06-11
Publication date: 2008-07-10

Abstract

Disclosed is a cooling system for a memory module, which includes a plurality of RAMs high-density mounted on a PCB thereof. In the system for radiating heat of a memory module, heat generated in unsymmetrical distribution by a Module Advanced Memory Buffer (AMB) in a Fully Buffered Dual In-line Memory (FBDIMM) can be uniformly distributed to memory devices thereof. In the cooling system for a memory module, the FBDIMM having an unsymmetrical distribution in generating heat effectively radiates heat so that the operating temperature of the AMB can decrease in comparison with the conventional art. Furthermore, temperature variation between the AMB and the RAMs is much improved, thereby securing reliability in the operating temperatureof the memory module.

Description

COOLING SYSTEM FOR MEMORY MODULE

Technical Field

[1] The present invention relates to a cooling system for a memory module including a plurality of memory devices high-density mounted on a PCB, and more particularly to a system for effectively radiating heat of a memory module, in which heat generated in unsymmetrical distribution by a Module Advanced Memory Buffer (AMB) in a Fully Buffered Dual In-line Memory (FBDIMM) can be uniformly distributed to memory devices thereof.

[2]

Background Art

[3] In general, a memory module used for a PC, a workstation, or a server is formed in such a manner that a plurality of memory devices, such as a Random Access Memory (RAM), is high-density mounted on one PCB having an outer electric connecting end. As such a memory module, a Registered Dual In-line Memory Module (RDIMM) has a Double Data Rate Sychronous Dynamic RAM (DDR SDRAM), which is a RAM most widely used in the present, mounted thereon, and a Fully Buffered Dual In-line Memory Module (FBDIMM) has an Advanced Memory Buff er( AMB) mounted on the RDIMM so as to support successive bus connection between DDR SDRAMs and transfer and control data in a packet-type, thereby rapidly performing operation of storing and extracting data without errors.

[4] FIG. Ia is a front view of a typical RDIMM 200, and FIG. Ib is a front view of a

FBDIMMlOO. According to FIG. 1, the RDIMM 200 has a structure where a plurality of RAMs 220 is connected with an outer connecting endformed at a lower part thereof by a circuit printed on a PCB. The FBDIMM 100 has a structure where a plurality of RAMs 120 is connected with an outer connecting end formed at a lower part thereof through an AMB 110 by a circuit printed on a PCB. The RDIMM 200 or FBDIMM 100 is installed in such a manner that the outer connecting end formed at a lower part thereof is inserted into a memory slot formed at a main board of a PC, etc. while having a predetermined interval.

[5] In the RDIMM 200 or the FBDIMM 100 having such a structure, the RAMs 120 and 220 mounted on a PCB have been developedtoward a high integration and a high speed, thereby increasing power consumption, and the width of wires is reduced, thereby increasing current density. Accordingly, even temperature becomes overly high, which is a fatal problemto a semiconductor. Also, in a case of the FBDIMM 100, an mounted AMB 110 radiates heat corresponding to several times as much as heat radiated in the RAMs 120. Therefore, there is a problem that the temperature of an ambient RAMs 120 mounted on the same PCB further increases.

[6] Basically, outer air is introduced between the RDIMM 200 or the FBDIMM 100 which is inserted into the memory slot through a fan so as to enable them to radiate heat. However, in comparison with a RAM adjacent to the fan, a RAM, which is far from the fan, does not radiate heat well. Particularly, the amount of radiation rapidly increases at an AMB 110 so that big temperature variation between heat RAMs is caused.

[7] With reference with FIGs. 2 to 5, the conventional art, which resolves the radiation problem of such memory modules 100 and 200, will be described hereinafter.

[8] FIG. 2 is a perspective view of an RDIMM 200 on which a conventional cooling system is mounted, and the radiating system has radiating plates 10 and 20, such as a aluminum plate having superior thermal conductivity, fixed in a front surface and a rear surface of the RDIMM 200 by a clip 300a.

[9] FIG. 3b is a perspective view of a FBDIMM 100 on which a cooling system according to the conventional art is mounted, and FIG. 3a is an exploded perspective view of the cooling system. The cooling system doesn't have a big technical difference in comparison with the radiating system used for the RDIMM 200 shown in FIG. 2. However, there is a difference where a bent part 31 is formed at the central part of a front radiating plate 30 due to a difference between heights of an AMB 110 mounted on a PCB and the RAMs 120. A bent arm 43a formed at both sides of a rear radiating plate 40 is a fixing means for preventing the FBDIMM 100 from moving in a lateral direction, and the bent arm 43a is assembled with a bentarm 33b formed at both sides of the front radiating plate 30. The front radiating plate 30 and the rear radiating plate 40 are fixed by a clip 300b, and grooves 32a and 32b for fixing the clip 300b are formed at each surface of the both radiating plates 30 and 40.

[10] FIG. 4a is a perspective view of a FBDIMM 100 on which a cooling system according to another conventional art is mounted, and FIG. 4b is an exploded perspective view of the cooling system. In comparison with FIG. 3, the cooling system of the FBDIMM 100 shown in FIG. 4 has a through hole 52 formed at the central part of a front radiating plate 50, and is separately equipped with a radiating plate 50a used for an AMB, which has thermal conductivity superior to that of the front radiating plate 50, by exposing an AMB 110 through the through hole. It is typical that the front radiating plate 50 or the rear radiating plate 60 is an aluminum plate, and the radiating plate 50a used for an AMB is a copper plate.

[11] FIG. 5 is a graph showing thermal distribution curves when outer air used for radiating is blown by a fan toward RAMI at an outer temperature of 2O⁰C. In the RDIMM 200, the temperature gradually increases toward a RAM8. Furthermore, in the FBDIMM 100, the temperature of an AMB 110 of the central part of the chart rapidly increases in comparison with the RDIMM 200. As shown in FIG. 5, in the conventional art, the amount of radiation of the RAM 220 mounted on the RDIMM 200 can be controlled in a predetermined variation range. However, in the FBDIMM 100 having an AMB 110 mounted thereon, the conventional cooling system cannot effectively reduce the temperature of the RAMs 120 and temperature variation.

[12]

Disclosure of Invention Technical Problem

[13] Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and the present invention provides a cooling system allowing an AMB 110 of a FBDIMM 100 to efficiently radiate heat, in which the required operating temperature of the FBDIMM 100 to be sufficiently secured, thereby improving reliability in temperature operating. Also, the present invention provides a cooling system for a memory module which improves temperature variation so as to allow a FBDIMM 100, which has a high temperature variation between a front surface and a rear surface of a FBDIMM 100, a central part of the front surface, and a lateral part thereof by means of an AMB 110, to have an uniform temperature distribution in the whole area thereof.

[14]

Technical Solution

[15] In accordance with an aspect of the present invention, there is provided a cooling system for a memory module, which includes: a plurality of RAMs 120 mounted on a PCB having both surfaces on which a circuit wire is printed; an AMB 110 mounted on a central surface of a front surface of the cooling system a front thermal interface material 500a attached to the front surface of the memory module 100 in which the AMB 110 is mounted, the front thermal interface material 500a being attached on the AMB 110 and the RAMs 120; a heat pipe 80 attached on the front thermal interface material 500a attached to the front surface of the memory module 100, the heat pipe 80 including a bent part 81 formed in such a manner that a central part of the heat pipe 80, which is positioned at the AMB 110, protrudes; a front radiating plate 70 which is attached to a front surface of the heat pipe 80 attached to the memory module 100 and has a through hole 71 formed at the central part of the front radiating plate 70; a rear thermal interface material 500b attached to a rear surface of the memory module 100; a rear radiating plate 90 attached to the rear thermal interface material 500b; and a fixing means 300b allowing the front radiating plate 70, the heat pipe 80, and the rear radiating plate 90 to be fixed in the memory module 100. [16] The heat pipe 80 includes at least one separated hollow part 82 formed at an interior of the heat pipe in a longitudinal direction of the heat pipe 80 and a wick formed at an interior of the hollow part 82 in a longitudinal direction of the heat pipe, and the hollow part 82 is filled with a predetermined amount of operating fluid.

[17]

Advantageous Effects

[18] The cooling system of a memory module according to the present invention, which has a structure as described above, allows a FBDIMM having an unsymmetrical radiating distribution to effectively radiate so as to improve temperature variation of a

RAM and an AMB at a high degree, thereby improving reliability in the operating temperature of a memory module. [19]

Brief Description of the Drawings [20] The above and other objects, features and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: [21] FIG. Ia is a front view of a typical RDIMM, and FIG. Ib is a front view of a

FBDIMM [22] FIG. 2 is a perspective view of a RDIMM on which a conventional cooling system is mounted; [23] FIG. 3b is a perspective view of a FBDIMM on which a cooling system according to another conventional art is mounted, and FIG. 3a is an exploded perspective view of the cooling system [24] FIG. 4b is a perspective view of a FBDIMM on which a cooling system according to another conventional art is mounted, and FIG. 4a is an exploded perspective view of the cooling system [25] FIG. 5 is a graph shows thermal distribution of each memory device (RAM) in a

RDIMM, on which the conventional cooling system shown in FIG. 2 is mounted, and a

FBDIMM on which the conventional cooling system shown in FIG. 4 is mounted [26] FIG. 6b is a perspective view of a FBDIMM on which a cooling system according to the first embodiment of the present invention is mounted, and FIG. 6ais an exploded perspective view of the cooling system [27] FIG. 7 is an exploded perspective view of a cooling system according to the second embodiment of the present invention

[28] Fig. 8 is a perspective view of a heat pipe according to the present invention;

[29] FIG. 9 is a perspective view of the interior of the heat pipe according to the present invention; and [30] FIG. 10 is a thermal distribution chart of each RAMin a FBDIMM on which a cooling system according to the present invention is mounted. [31]

Best Mode for Carrying Out the Invention

[32] Hereinafter, an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

[33] The following description of the present invention is provided so as to make the present invention described above be completed and those skilled in the art fully understand the feature and spirit of the present. In the accompanying drawings, so as to make the feature of the present invention clear, some drawings are exaggeratingly illustrated, and some additional parts are omitted.

[34] FIG. 6a is an exploded perspective view of the cooling system according to the first embodiment of the present invention, and FIG. 6b is a perspective view of a FBDIMM on which a cooling system is mounted. Referring to FIG. 6, a plurality of RAMs 120 is mounted on a PCB on which circuit wires are printed. In a memory module 100 having an AMB 110 mounted on the central part of the front surface thereof, a front thermal interface material 500a and a rear thermal interface material 500b are attached to front and rear surfaces of the memory module 100, respectively, so as to reduce thermal contact resistance against the AMB 110 and the RAMs 120. A heat pipe 80, which includes a bent part 81 having the central surface thereof protruding according to the difference of height between the AMB 110 and the RAMs 120, is attached to the front surface of the front thermal interface material 500a. It is preferable that the front thermal interface material 500a is attached while having a size suitable for the size and position of the AMB 110 and the RAMs 120 or suitable for the size of the heat pipe 80.

[35] A front radiating plate 70, which has a through hole 71 so as to allow the bentpart

81 to be exposed, makes contact with the front surface of the heat pipe 80, and a rear radiating plate 90 having superior thermal conductivity makes contact with the rear surface of the rear thermal interface material 500b. The front radiating plate 70, the heat pipe 80, the front thermal interface material 500a, the rear thermal interface material 500b, and the rear radiating plate 90 are mounted on the memory module 100 by a fixing means 300b locked in a protruding part 72 formed at the front radiating plate 70 and a protruding part (not shown) of the rear radiating plate 90 so as to be fixed.

[36] A pair of coupling pins 73 and 93 is included at each upper part of the front radiating plate 70 and the rear radiating plate 90, respectively. A bent arm (not shown) is included at a lower part of front radiating plate 70 so as to make contact with a lower surface of the heat pipe 80, and a bent arm 91 is included in a lateral part of the rear radiating plate 90 so as to be locked in a lateral part of the memory module 100. According to the above described structure, the cooling system can be prevented from being separated from the memory module 100 by the coupling pins 73 and 93 and the bent arm (not shown), and the cooling system can be prevented from being separated from the memory module 100 in a left or right direction by the bent arm 91.

[37] Also, the front radiating plate 70 further includes a plurality of heat transfer promoting holes 74 so as to promote contact with outer air introduced along the front surface of the front radiating plate 70.

[38] The front thermal interface material 500a and the rear thermal interface material

500b are preferably made from a radiating pad, which can reduce thermal contact resistance, or made from phase change material so as to transfer radiated heat of the AMB 110 and the RAMs 120 to the heat pipe 80 and the rear radiating plate 90.

[39] The front radiating plate 70 or the rear radiating plate 90 is preferably made from aluminum or copper material having superior thermal conductivity, so as to smoothly radiate transferred heat to the outer air, and particularly the front radiating plate 70 is preferably made from them so as to protect the heat pipe 80 and sufficiently support coupling structure of the cooling system.

[40] Hereinafter, the present having a structure as shown in FIG. 6 will be described.

Thermal contact resistance is reduced by the front thermal interface material 500a and the rear thermal interface material 500b so that the heat radiated in the AMB 110 and the RAMs 120 is smoothly transferred to the heat pipe 80 and the rear radiating plate 90, and some amount of the heat transferred to the heat pipe 80 is transferred to the front radiating plate 70. The heat transferred to the heat pipe 80, the front radiating plate 70, and the rear radiating plate 90 is radiated to the outer air, and particularly, the heat is easily radiated through the bent part 81 of the heat pipe 80 and heat transfer promoting hole 74.

[41] Also, the heat pipe 80 is arranged only on the front surface of the memory module

100 on which the AMB 110 radiating a large amount of heat in comparison with the RAMs 120 is mounted, and the rear surface of the memory module 100 radiates a small amount of heat in comparison with the front surface thereof so that the desired radiating character can be obtained only by the rear radiating plate 90. Generally, the thickness of the memory module including a radiating system inserted into a memory slot has to be minimized by considering the interval between memory modules adjacent to each other and introduction of outer air used for radiating, so that the heat pipe 80 is attached only to the front surface thereof.

[42] FIG. 7 is an exploded perspective view of a cooling system according to the second embodiment of the present invention. The cooling system shown in FIG. 7 has the same structure as the structure of the cooling system of FIG. 6. However, a heat transfer promoting hole 74 of the front radiating plate 70 has the same shape as the shape of a through hole 71 of the central part thereof. Particularly, such a shape can secure the maximum effectiveness of radiation of the heat pipe 80 while keeping a frame suitable for mounting the cooling system to the memory module 100.

[43] FIG. 8 is a perspective view illustrating the heat pipe 80 according to the present invention, and FIG. 9 is a perspective view illustrating the interior structure of the heat pipe 80 show in FIG. 8.

[44] With reference to FIGs. 8 and 9, the heat pipe 80 includes at least one separated hollow part 82 formed at the interior thereof in the longitudinal direction, and further includes a wick (not shown) causing capillary force at the interior surface of the hollow part 82. Also, the hollow part 82 is filled with a predetermined amount of operating fluid (not shown), and both ends of the hollow part 82 are sealed by an attachment surface 83 at both ends of the heat pipe 80. The heat pipe 80 has a flat plate-shape so as to allow the attachment surface between the RAMs 120 and the AMB 110 to be maximized, and has a bent part 81 protruding from the front surface thereof, at which the AMB 110 is positioned, by considering the difference between heights of the RAMs 120 and the AMB 110 mounted on the memory module 100. The heat pipe 80 may be made by pressing molding or pressing process.

[45] FIG. 10 shows temperature distribution of each memory device 120 in the memory module 100, on which a cooling system according to the present invention is mounted, and in the memory module 100 on which a conventional cooling system is mounted. The standard of radiating efficiency is the temperature of the surface of the AMB 110 and each RAMs 120 mounted on the memory module 100 including a FBDIMM. As the temperature of the surface of the AMB 110 and each RAMs 120 is low and temperature variation is less, the radiating efficiency is superior.

[46] The experiment shows a result respective to the front surface of memory module

100, on which the AMB 110 is mounted, and doesn't include a result respective to the rear surface thereof. The conventional art compared with the present invention is the cooling system shown in FIG. 4. The result is measured in a state where the memory module 100 is installed at the server and is operated at a maximized degree, in which the temperature of each surface of 8 RAMs and IAMB is measured. A RAM 8 positioned at an end portion in a direction that air is introduced has a high temperature. This is because that heat transference character is reduced toward the RAM 8 due to the air introduction character formed between the memory modules inserted into the memory slot.

[47] With reference to FIG. 10, the temperature of the surface of the conventional memory module (FBDIMM) 100 has temperature distribution having a parabolic shape respective to the temperatures of ambient RAMs 120 while having a maximum value at the temperature of the AMB 110. Meanwhile, in the cooling system for a memory module according to the present invention, the heat pipe 80 rapidly absorbs heat radiated at the AMB 110 so as to rapidly diffuse the absorbed heat in the longitudinal direction of the heat pipe 80. Therefore, temperature variation between the AMB 110 and the RAMs 120 is much improved in comparison with the conventional art.

[48] The present invention described above is not limited by the described embodiments and the accompanying drawings, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention.

[49]

Claims

[1] A cooling system for a memory module, comprising: a plurality of memory devices (RAMs) 120 mounted on a PCB having both surfaces on which a circuit wire is printed; an AMB 110 mounted on a central part of a front surface of the cooling system a front thermal interface material 500a attached to the front surface of a memory module 100 on which the AMB 110 is mounted, the front thermal interface material 500a being attached on the AMB 110 and the RAMs 120 a heat pipe 80 attached on the front thermal interface material 500a attached to the front surface of the memory module 100, the heat pipe 80 including a bent part 81 formed in such a manner that a central part of the heat pipe 80, which is positioned at the AMB 110, protrudes; a front radiating plate 70 attached to a front surface of the heat pipe 80 attached to the memory module 100; a rear thermal interface material 500b attached to a rear surface of the memory module 100; a rear radiating plate 90 attached to the rear thermal interface material 500b; and a fixing means 300b allowing the front radiating plate 70, the heat pipe 80, and the rear radiating plate 90 to be fixed in the memory module 100.

[2] The cooling system for a memory module as claimed in claim 1, wherein the heat pipe 80 includes at least one separated hollow part 82 formed at an interior of the heat pipe in a longitudinal direction of the heat pipe 80 and a wick formed at an interior of the hollow part 82 in a longitudinal direction of the heat pipe, and the hollow part 82 is filled with a predetermined amount of operating fluid.

[3] The cooling system for a memory module as claimed in claim 1, wherein the front radiating plate 70 has a through hole 71 formed so as to allow the bent part 81 of the heat pipe 80 to be exposed and a plurality of heat transfer promoting holes 74 formed so as to a predetermined surface of the heat pipe 80 to be exposed.

[4] The cooling system for a memory module as claimed in claim 1, wherein the heat pipe 80, the front radiating plate 70, or the rear radiating plate 90 is made from aluminum or copper material.