Abstract:
There is disclosed a heat radiation device for memory modules intended for radiating heat that is generated from a memory module group wherein a plurality of memory modules equipped with memory elements on both the front and rear face sides of a substrate are placed in parallel. The device comprises heat radiation plates in pairs composed of front face side heat radiation plates in contact with memory elements that are installed on the front face side of the substrate for each of the memory modules, and of rear face side heat radiation plates in contact with memory elements that are installed on the rear face side of the substrate; and connecting members for heat radiation plates in pairs which connect the heat radiation plates in pairs so that heat is conducted among a plurality of the heat radiation plates in pairs.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a heat radiation device for memory modules which radiates heat that is generated from memory elements of each of the modules to cool the memory elements, in cases where a plurality of semiconductor memory modules, wherein a plurality of memory elements are installed on a memory substrate (hereinafter sometimes abbreviated to “module”), are placed in parallel on a mother board or the like to form a module group. The above-mentioned semiconductor memory modules are shown as an example, by DIMM (Dual Inline Memory module) wherein a plurality of SDRAM (Synchronous Dynamic Access Memory) are arranged on a memory substrate.  
         [0003]     2. Description of the Related Art  
         [0004]     An example of a module group is shown in  FIG. 1 . Module group  2  shown in  FIG. 1  consists of three modules  2   a  to  2   c . Each of modules  2   a  to  2   c  has memory substrate  3  and a plurality of (generally 16 numbers) memory elements  4  that are arranged along the longitudinal direction of substrate  3  on both front and rear face sides thereof. Memory substrate  3  for each of modules  2   a  to  2   c  is inserted into connector  5  placed at a constant spacing.  
         [0005]     Heat generated from memory elements  4  installed on each of modules  2   a  to  2   c  is radiated through heat radiation and convection from the surfaces of memory elements  4 , and this heat is conducted to mother board  1  via memory substrate  3  and connector  5 , and is radiated from the surfaces of mother board  1  as well. In  FIG. 1 , heat radiation from the surfaces of memory elements  4 , convection therefrom and heat radiation through mother board  1  are schematically shown by arrows X, Y and Z, respectively. Japanese laid-open patent publication No. 94399/1986 (Showa 61) discloses a circuit module which enhances the heat radiation effect by extending the peripheries of a circuit chip or circuit board each corresponding to memory substrate  3  shown in  FIG. 1 , up to the external portion of that case that accommodates the above-mentioned chip or board.  
         [0006]     Moreover in the case of RIMM (Rambus In-line memory Module) wherein a plurality of memory elements that are installed on memory substrates function one by one, the load and heat generation per each memory element increase as compared with other memory modules wherein a plurality of memory elements function simultaneously. Thus as shown in  FIG. 2 , heat radiation plates  6  which radiate heat generated from memory elements  4  in the longitudinal direction of memory substrate  3  are installed on each of modules  2   a  to  2   c . Heat radiation plates  6  are arranged so as to encompass memory elements  4  on both front and rear face side of memory substrate  3  for each of modules  2   a  to  2   c , and are in contact with opposing memory elements  4 . Accordingly, heat generated from a memory element which was installed on memory substrate is dispersed in longitudinal direction of said memory substrate via heat radiation plate  6  with which the memory element comes in contact, and is radiated from the surface of the heat radiation plate  6 .  
         [0007]     It is difficult to maintain module temperature at a stipulated value or lower by heat radiation realized by the structure as shown in  FIG. 1 . In particular, with regard to central module  2   b  among the three modules  2   a  to  2   c  shown in  FIG. 1 , the convectional heat radiation effect is lowered by barriers due to modules  2   a  and  2   c  both of which are on the outside of module  2   b . Further, since module  2   b  receives heat from memory elements  4  installed on modules  2   a  and  2   c  both on the outside of module  2   b , its temperature tends to be increased as compared with modules  2   a ,  2   c.    
         [0008]     In addition, the structure as shown in  FIG. 2  may or may not uniformize the temperature difference among modules  2   a  to  2   c , but the temperature difference among a plurality of adjacent modules is not uniformized. In particular, the temperature raising tendency of central module  2   b  among the three modules  2   a  to  2   c  is the same as that in the structure shown in  FIG. 1 . In fact, three modules  2   a  to  2   c  shown in  FIG. 2  were made to function simultaneously, and the temperatures thereof were measured. As a result, the highest temperature of central module  2   b  was 67.2° C., while that of modules  2   a ,  2   c , both on the outside was, 61.6° C., thereby causing a temperature difference of 5.0° C. or higher.  
         [0009]     As mentioned above, in the case where a plurality of modules are placed in parallel on a mother board or the like, much difference in temperature is caused among each of the modules, thus bringing about scattering of characteristic parameters (setup time, hold time and the like) of the memory elements that are installed on each of the modules. The scattering of characteristic parameters of the memory elements induces system malfunction. Further, if working frequency of memory elements further increases hereafter, there is also a danger of thermal breakage of memory elements.  
       SUMMARY OF THE INVENTION  
       [0010]     An object of the present invention is to provide a heat radiation device for memory modules which is capable of efficiently radiating heat generated from a plurality of memory modules that are adjacently placed in parallel and at the same time, of uniformizing the temperature of each of the memory modules.  
         [0011]     The heat radiation device for memory modules according to the present invention is a heat radiation device for memory modules intended for radiating heat generated from a memory module group wherein a plurality of memory modules equipped with memory elements on both the front and rear face sides of a substrate are placed in parallel. The device comprises heat radiation plates in pairs composed of front face side heat radiation plates in contact with memory elements that are installed on the front face side of the substrate for each of the memory modules, and of rear face side heat radiation plates in contact with memory elements that are installed on the rear face side of the substrate; and connecting members for heat radiation plates in pairs which connect the heat radiation plates in pairs that are installed per each of the memory modules. Accordingly, the heat generated from the memory elements is radiated from the surfaces of the heat radiation plates in contact with the memory elements, and is conducted to other heat radiation plates in pairs via the connecting member for the heat radiation plates in pairs, whereby the temperature of the entire memory module group is uniformized. As a result, the scattering of characteristic parameters is suppressed which is attributable to the temperature difference among the memory elements. Adhesivity to the memory elements can be enhanced by fixing the above-mentioned front and rear face side heat radiation plates by means of an optional fixing means or a bias means. It is also possible to enhance heat conduction efficiency by forming all of the front face side heat radiation plates, rear face side heat radiation plates and connecting members for the heat radiation plates in pairs out of the same material.  
         [0012]     In the case where each of the memory modules which constitutes the memory module group is equipped with heat radiation plates in advance, the spacing of the above-mentioned heat radiation plates in pairs is set on the outside of the heat radiation plates so as to come into contact with the heat radiation plates. In this case, both the heat radiation effect due to the heat radiation plates with which the memory module is equipped in advance, and the heat radiation effect due to the heat radiation device for memory modules according to the present invention are obtainable without altering the memory modules at all.  
         [0013]     The heat radiation effect can also be further enhanced by forming slits on the above-mentioned connection member for heat radiation plates in pairs.  
         [0014]     The objects, characteristics and advantages of the present invention will become from the description mentioned below and the attached drawings which illustrate some examples of the present invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is an enlarged cross-sectional view illustrating one example of a memory module group;  
         [0016]      FIG. 2  is an enlarged cross-sectional view illustrating a memory module group which is constituted of memory modules each equipped with heat radiation plates;  
         [0017]      FIG. 3  is an enlarged cross-sectional view illustrating one example of an embodiment of a heat radiation device for memory modules according to the present invention;  
         [0018]      FIG. 4A  is a plan view illustrating the heat radiation device for memory module as shown in  FIG. 3 ;  
         [0019]      FIG. 4B  is a partially cutaway side view illustrating the heat radiation device for memory module as shown in  FIG. 3 ;  
         [0020]      FIG. 5  is an enlarged cross-sectional view illustrating a heat radiation device for memory modules wherein heat radiation plates in pairs are extensionally provided;  
         [0021]      FIG. 6  is an enlarged cross-sectional view illustrating another example of an embodiment of a heat radiation device for memory modules according to the present invention;  
         [0022]      FIG. 7  is an enlarged cross-sectional view illustrating another example of an embodiment of a heat radiation device for memory modules according to the present invention;  
         [0023]      FIG. 8  is a plan view illustrating another example of an embodiment of a heat radiation device for memory modules according to the present invention; and  
         [0024]      FIG. 9  is an enlarged cross-sectional view of a heat radiation device for memory modules for comparison with the device of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     First Embodiment of the Present Invention  
       [0025]      FIG. 3  is an enlarged cross-sectional view illustrating heat radiation device  10  for memory modules installed on memory module group  2  having three memory modules  2   a  to  2   c  according to the present invention.  FIG. 4A  is a plan view illustrating heat radiation device  10  for memory modules installed on memory module group  2  according to the present invention.  FIG. 4B  is a partially cutaway side view illustrating heat radiation device  10  for memory modules installed on memory module group  2  according to the present invention, wherein mother board  1  and connector  5  as illustrated in  FIG. 3  are not shown in this drawing for the sake of convenience. Memory module group  2  and each of memory modules  2   a  to  2   c  which constitute memory module group  2 , each shown in  FIG. 3 , have structures that are the same as those of the memory module group and the memory modules that are shown in  FIG. 1 . As such, the same structure is marked with the same symbol without repeating the same description. Among the outside faces of memory substrate in this example, the right side and left side faces in  FIG. 3  are defined as front face and rear face, respectively, but the foregoing definition is nothing more than a definition for the sake of convenience.  
         [0026]     As illustrated in detail in  FIG. 3 , heat radiation device  10  for memory modules according to the present invention has three heat radiation plates in pairs  13   a  to  13   c  each made up of front face side heat radiation plates  11  and rear face side heat radiation plates  12 , opposite each other at a constant gap, and connection members  14  for heat radiation plates in pairs which connect three heat radiation plates in pairs  13   a  to  13   c  in order to integrate them. All of front face side heat radiation plates  11  and rear face side heat radiation plates  12 , both constituting each of heat radiation plates in pairs  13   a  to  13   c , are metallic thin sheets. Front face side heat radiation plate  11  for heat radiation plates in pairs  13   a  has a width (W 1 ) which is somewhat larger than the width (W 2 ) of opposing rear face side heat radiation plate  12 . On the other hand, rear face side heat radiation plate  12  for heat radiation plates in pairs  13   c  has a width (W 1 ) which is somewhat larger than the width (W 2 ) of opposing front face side heat radiation plate  11 . That is to say, in regard to heat radiation plates in pairs  13   a  and  13   c , the relationship of the various sizes is reversed between front face side heat radiation plate  11  and rear face side heat radiation plate  12 . In addition, front face side heat radiation plate  11  for heat radiation plates in pairs  13   b  and rear face side heat radiation plate  12  each have the same width, which is the same as the width (W 2 ) of rear face side heat radiation plate  12  for heat radiation plates in pairs  13   a  and the width (W 2 ) of front face side heat radiation plate  11  for heat radiation plates in pairs  13   c.    
         [0027]     As illustrated in  FIG. 4B , communication holes  21  are opened at the upper and lower two positions on both ends in the longitudinal direction for all of front face side heat radiation plates  11  and rear face side heat radiation plates  12 . When heat radiation device  10  for memory modules is installed on memory module group  2 , each of communication holes  21  communicates with through holes  20  that are opened on substantially four corners of corresponding memory substrate  3 .  
         [0028]     Again reference is made to  FIG. 3 . The upper side face of front face side heat radiation plate  11  for heat radiation plates in pairs  13   a  protrudes upwardly by (W 1 -W 2 ) from the upper end of rear face side heat radiation plate  12 . The protruded upper side face of front face side heat radiation plate  11  for heat radiation plates in pairs  13   a  is assigned to the surface of either end in width direction of connection member  14  for heat radiation plates in pairs. The upper end surface of rear face side heat radiation plate  12  opposite to front face side heat radiation plate  11  at a prescribed gap is assigned to the rear face of connection member  14  for heat radiation plates in pairs. Further L—letter type fixing member  15  is assigned to a corner portion that is formed by contact between the upper end surface of rear face side heat radiation plate  12  and rear face of connection member  14  for heat radiation plates in pairs. Assigned fixing member  15  is fixed to rear face side heat radiation plate  12  and connection member  14  for heat radiation plates in pairs by means of a fastener (clip  16 ). Front face side heat radiation plate  11  and rear face side heat radiation plate  12  are each fixed to memory substrate  3  for memory module  2   a  by means of fixing tool  22  which is inserted into communication hole  21  of front face side heat radiation plate  11 , through-hole  20  of memory substrate  3  and communication hole  21  of rear face side heat radiation plate  12 , and front and rear side heat radiation plates  11  and  12  closely adhere to memory elements  4 .  
         [0029]     The upper side face of rear face side heat radiation plate  12  for heat radiation plates in pairs  13   c  protrudes upwardly by (W 1 -W 2 ) from the upper end of front face side heat radiation plate  11 . The protruded upper side face of rear face side heat radiation plate  12  is assigned to the surface of the other end in the width direction of connection member  14  for heat radiation plates in pairs. Moreover, front face side heat radiation plates  11  and connection member  14  for heat radiation plates in pairs are fixed with fixing member  15  and clip  16  as is the case with heat radiation plates in pairs  13   a . In addition, front face side heat radiation plates  11  and rear face side heat radiation plates  12  are each fixed to memory substrate  3  for memory module  2   c  by means of fixing tool  22 , and closely adhere to memory elements  4  as is the case with heat radiation plates in pairs  13   a.    
         [0030]     The upper end surfaces of front face side heat radiation plate  11  for heat radiation plates in pairs  13   b  and rear face side heat radiation plate  12  opposite to each other at a prescribed gap are each assigned to the rear face of connection member  14  for heat radiation plates in pairs. The upper end surfaces of front face side heat radiation plate  11  and rear face side heat radiation plate  12 , both assigned to the rear surface of connection member  14  for heat radiation plates in pairs, are each fixed to connection member  14  for heat radiation plates in pairs by means of fixing member  15  and clip  16 . Front face side heat radiation plate  11  and rear face side heat radiation plate  12  are each fixed to memory substrate  3  for memory module  2   b  by means of fixing tool  22 , and closely adhere to memory elements  4  as is the case with heat radiation plates in pairs  13   a  and  13   c.    
         [0031]     As described hereinabove, when heat radiation device  10  for memory modules according to the present invention is installed on memory module group  2 , each of heat radiation plates in pairs  13   a  to  13   c  cover corresponding memory modules  2   a  to  2   c . Front face side heat radiation plates  11  and rear face side heat radiation plates  12  each for heat radiation plates in pairs  13   a  to  13   c , which cover memory modules  2   a  to  2   c  are connected to each in order to integrate them. Further, front face side heat radiation plates  11  and rear face side heat radiation plates  12  each for heat radiation plates in pairs  13   a  to  13   c  are each brought into surface contact with the surface of memory elements  4  that are installed on opposite memory substrate  3 , and closely adhere thereto.  
         [0032]     According to the above-described structure, heat generated from any of the memory elements for any of memory modules is conducted to the front face side heat radiation plates or rear face side heat radiation plates each closely adhering to the memory elements, and is dispersed in the memory modules, and is conducted to other heat radiation plates in pairs via other connection members for heat radiation plates in pairs. As a result, heat generated from any of the memory elements for any of memory modules is dispersed in the memory module group so that the temperatures among the memory modules are uniformized. For instance, heat generated from memory element  4  installed on the front face of memory substrate  3  for memory module  2   b  shown in  FIG. 3  is conducted to front face side heat radiation plate  11  for heat radiation plates in pairs  13   b , is dispersed in the longitudinal direction of heat radiation plate  11 , and is radiated from the front face of heat radiation plate  11 . Likewise, heat generated from memory element  4  installed on the rear face of memory substrate  3  for the memory module  2   b  is conducted to rear face side heat radiation plate  12  for heat radiation plates in pairs  13   b , is dispersed in the longitudinal direction of heat radiation plate  12 , and is radiated from the surface of heat radiation plate  12 . Further, heat conducted to front face side heat radiation plate  11  is conducted to connection member  14  for heat radiation plates in pairs, is radiated from the surface of connection member  14 , and is mainly conducted to heat radiation plates in pairs  13   a  and also to memory module  2   a . Further, heat conducted to rear face side heat radiation plate  12  is conducted to connection member  14  for heat radiation plates in pairs, is radiated from the surface of connection member  14 , and is mainly conducted to heat radiation plates in pairs  13   c  and also to memory module  2   c . As is the case with the prior art, heat generated from memory element  4  is conducted to mother board  1  via memory substrate  3  and connector  5 , and is radiated from the surface of mother board  1 . The above-described heat conduction state is schematically shown in  FIG. 3  by the use of arrows with intermittent lines.  
         [0033]     As illustrated in  FIG. 3 , when silicone grease  25  is applied between memory element  4  and front face side heat radiation plates  11 /rear face side heat radiation plates  12  for each of heat radiation plates in pairs  13   a  to  13   c , adhesivity between the surface of memory element  4  and front face side heat radiation plates  11 /rear face side heat radiation plates  12  is improved, thereby enhancing heat conduction efficiency. Moreover, front face side heat radiation plates  11 , rear face side heat radiation plates  12  and connection member  14  for heat radiation plates in pairs, when formed of the same material, bring about further enhanced heat conduction efficiency. A material to be selected in this case has preferably high heat conductivity, and is for example by copper (Cu) which is preferable. However, it is not an indispensable requirement of the present invention to form, with the same material, all of front face side heat radiation plates  11 , rear face side heat radiation plates  12  and connection member  14  for heat radiation plates in pairs.  
         [0034]     The heat radiation plates in pairs can be properly added in accordance with the number of memory modules.  FIG. 5  illustrates an example of added new heat radiation plates in pairs  13   e  on the right side of heat radiation plates in pairs  13   a  as shown in  FIG. 3 . Heat radiation plates in pairs  13   e  that are to be added have front face side heat radiation plate hand rear face side heat radiation plate  12  both being the same as those of heat radiation plates in pairs  13   a , and are connected to heat radiation plates in pairs  13   a  with connection member  30  that is to be added having a width smaller than that of connection member  14  as shown in  FIG. 3 . Specifically one end in the width direction of connection member  30  that is to be added is upwardly folded and bent. Bent flexure  31  is assigned to protrusion  32  (the portion upwardly protruding from connection member  14 ) of front face side heat radiation plate  11  for heat radiation plates in pairs  13   a . Assigned bent flexure  31  and protrusion  32  are fixed with connection fixing tool  33 . The upper portion of front face side heat radiation plate  11  for heat radiation plates in pairs  13   e  whose portion protrudes higher than the connection member  30  that is to be added, functions in the same manner as protrusion  32  in the case of adding another heat radiation plates in pairs.  
         [0035]     The fixing structure for front face side heat radiation plate  11 /rear face side heat radiation plate  12 , each constituting heat radiation plates in pairs  13   e  that is to be added and connection member  30  that is to be added, is the same as the fixing structure for front face side heat radiation plate  11 /rear face side heat radiation plate  12  for heat radiation plates in pairs  13   a  and connection member  14  for heat radiation plates in pairs. Likewise, the fixing structure for front face side heat radiation plate  11 /rear face side heat radiation plate  12  each constituting heat radiation plates in pairs  13   e  that is to be added and memory substrate  3 , is the same as the fixing structure for front face side heat radiation plate  11 /rear face side heat radiation plate  12  for heat radiation plates in pairs  13   a  and memory substrate  3 .  
       Second Embodiment of the Present Invention  
       [0036]     Another embodiment of a heat radiation device for memory modules according to the present invention is illustrated in  FIG. 6 . The fundamental structure of heat radiation device  10  for memory modules shown in  FIG. 6  is the same as that of heat radiation device  10  for memory modules shown in  FIG. 3 . The same structure is marked with the same symbols without repeating the same description, but a description is made only for different structures.  
         [0037]     In regard to heat radiation device  10  for memory modules shown in  FIG. 6 , front face side heat radiation plates  11 /rear face side heat radiation plates  12 , each constituting heat radiation plates in pairs  13   a  to  13   c  and memory substrates  3 , are connected by an elastic body (spring  40 ). Thereby front face side heat radiation plates  11  and rear face side heat radiation plates  12  are attracted to the opposite side of memory substrates  3 , and closely adhere to the surfaces of memory elements  4  on memory substrates  3 .  
         [0038]     In regard to heat radiation device  10  for memory modules shown in  FIG. 3 , front face side heat radiation plates  11 /rear face side heat radiation plates  12  and memory substrates  3  are fixed by the use of fixing tool  22  in the form of a pin. On the other hand, regarding heat radiation device  10  for memory modules shown in  FIG. 6 , a fixing means corresponding to fixing tool  22  shown in  FIG. 3  is made unnecessary, though fixing tool  22  shown in  FIG. 3  and spring  40  shown in  FIG. 6  can be used in combination. In this case, when the communication holes for front face side heat radiation plates  11 , through-holes for memory substrates  3 , communication holes for rear face side heat radiation plates  12  and fixing tools  22 , are in a free state without being fixed, fixing tool  22  functions as a regulating means for regulating the dislocation of front face side heat radiation plates  11 , rear face side heat radiation plates  12  and memory substrates  3  without at all impairing the function due to the bias of spring  40 .  
       Third Embodiment of the Present Invention  
       [0039]     Another embodiment of a heat radiation device for memory modules according to the present invention is illustrated in  FIG. 7 . The fundamental structure of heat radiation device  10  for memory modules shown in  FIG. 7  is the same as that of heat radiation device  10  for memory modules shown in  FIG. 3 . The same structure is marked with the same symbols without repeating the same description, but a description is made only for different structures.  
         [0040]     The memory module shown in  FIG. 7  is characterized mainly by an improvement that enables each of memory modules  2   a  to  2   c  to be installed on memory module group  2  equipped in advance with heat radiation plate  6 . Specifically, the gap between front face side heat radiation plates  11  and rear face side heat radiation plates  12  each constituting radiation plates in pairs  13   a  to  13   c  is increased by a necessary and sufficient degree as compared with heat radiation plates in pairs  13   a  to  13   c  shown in  FIG. 3 .  
         [0041]     Thereby, it is possible to cover heat radiation plates  6  each installed on memory modules  2   a  to  2   c  from outside with heat radiation plates in pairs  13   a  to  13   c . More specifically, when heat radiation plates in pairs  13   a  to  13   c  are made to cover corresponding memory modules  2   a  to  2   c , each of front face side heat radiation plates  11  and rear face side heat radiation plates  12  adheres to heat radiation plates  6  for memory modules  2   a  to  2   c . When silicone grease  25  is applied between each of front face side heat radiation plates  11  and rear face side heat radiation plates  12  and each of heat radiation plates  6 , the adhesion therebetween is further enhanced and thus heat conductivity is further improved.  
       Fourth Embodiment of the Present Invention  
       [0042]     It is possible to form at least one slit  50  as shown in  FIG. 8  on the connection member for heat radiation plates in pairs which constitutes the heat radiation device for memory modules, the device being described in the first to third embodiments of the invention. In the case of forming slit  50 , the heat that is generated mainly from front face side heat radiation plates  11  and rear face side heat radiation plates  12  becomes more prone to be radiated to the outside of heat radiation device  10  for memory modules, thereby further enhancing the heat radiation effect. Each of slits  50  shown in  FIG. 8  measures 5.0 by 10.0 mm, but slits  50  is not restricted to the form, shape, size, dimension and arrangement as shown in the drawings.  
         [0043]     In the following, a description will be given of one example of a test which was carried out in order to confirm the working effect of the heat radiation device for memory modules according to the present invention. In this test, the following three specimens were prepared.  
         [0044]     Specimen 1: memory module group equipped with the heat radiation device for memory modules according to the present invention as shown in  FIG. 3   
         [0045]     Specimen 2: memory module group equipped with a heat radiation device for memory modules different from that of the present invention.  
         [0046]     Specimen 3: memory module group not equipped with any heat radiation device for memory modules (memory module group shown in  FIG. 1 ).  
         [0047]     The structure of the heat radiation device for memory modules of specimen 2, is shown in  FIG. 9 . This heat radiation device for memory modules has a structure which is the same as that of heat radiation device  10  for memory modules as shown in  FIG. 3  except that it is not equipped with connection member  14  for heat radiation plates in pairs installed on heat radiation device  10  for memory module as shown in  FIG. 3  (the heat radiation device for memory modules according to the present invention), and those of each of heat radiation plates in pairs  13   a  to  13   c  are independent.  
         [0000]     Conditions and details of the test are as follows  
         [0048]     Each memory module  2   a  to  2   c : capacity 1 GB Unb-DIMM  
         [0049]     Memory elements  4 : DDR SDRAM 512 Mbit×8×2 (total number of 16)  
         [0050]     Single body package: TSOP  
         [0051]     Number of modules: 3 (three plug in)  
         [0052]     Working frequency of memory element  4 : DDR 333 [MHz] 
         [0053]     Environment: natural convection  
         [0054]     Gap between adjacent connector: 11.0 mm  
         [0055]     Gap between modules  2   a  to  2   c  (DIMM gap): 5.0 mm  
         [0056]     Materials of construction for heat radiation plates in pairs  13   a  to  13   c  and connection member  14  for heat radiation plates in pairs: copper  
         [0057]     Height of memory substrates  3  (distance from mother board  1  to substrate  3 ): 30.48 mm  
         [0058]     Height of heat radiation plates in pairs  13   a  to  13   c : 50.8 mm (distance from mother board  1  to connection member  14  for heat radiation plates in pairs)  
         [0059]     Object of measurement: Memory elements  4  having highest temperature are to be installed on central memory module  2   b.    
         [0000]     {Test 1} 
         [0060]     On the assumption that either the front or rear elements of memory elements  4  which are installed on both front and rear face side of memory substrate  3  are used, power consumption of each of memory modules for specimens 1 to 3 was set as follows. 
        memory module  2   b : eight memory elements installed on the front face of memory substrate: 542 [mW]
            eight memory elements installed on the front face of memory substrate: 58 [mW]   
            memory modules  2   a  and  2   c : all of 16 memory elements: 58 [mW]       
 
         [0064]     Highest temperatures of memory elements  4  for memory module  2   b  of specimens 1 to 3 were measured under the foregoing conditions. The following results were obtained.  
         [0065]     Specimen 1: 59.8° C.  
         [0066]     Specimen 2: 63.3° C.  
         [0067]     Specimen 3: 80.5° C.  
         [0068]     It has been confirmed that specimen 1 (heat radiation device  10  for memory modules according to the present invention) has a high cooling effect of about 4.0° C. (63.3-59.8) as compared with the heat radiation device for memory module according to specimen 2 in which each of the heat radiation plates is independent.  
         [0000]     {Test 2} 
         [0069]     On the assumption that memory elements  4  installed on both the front and rear face side of memory substrates  3  alternately function, power consumption of each of memory modules for specimens 1 to 3 was set as follows. 
        memory module  2   b : eight memory elements installed on the front face of memory substrate: 300 [mW]
            :eight memory elements installed on the front face of memory substrate: 300 [mW]   
            memory modules  2   a  and  2   c : all of the 16 memory elements: 58 [mW]       
 
         [0073]     Highest temperatures of memory elements  4  for memory module  2   b  of specimens 1 to 3 were measured under the foregoing conditions. The following results were obtained.  
         [0074]     Specimen 1: 58.4° C.  
         [0075]     Specimen 2: 62.4° C.  
         [0076]     Specimen 3: 75.1° C.  
         [0077]     As is the case with test 1, it has been confirmed that specimen 1 (heat radiation device  10  for memory module according to the present invention) has a high cooling effect of about 4.0° C. (62.4-58.4) as compared with the heat radiation device for memory module according to specimen 2 in which each of the heat radiation plates is independent.  
         [0078]     Furthermore, measurements were made of the highest temperatures of the memory elements for the memory module groups on which heat radiation device  10  for memory module, according to the present invention as shown in  FIG. 8 , was installed under the same conditions as in this test. As a result, the highest temperature of the memory elements installed on the central memory module was 57.6° C. Thereby, it has been confirmed that a further cooling effect of about 1.0° C. is exhibited by forming slits  50  on connection member  14  for heat radiation plates in pairs.  
         [0079]     Although the embodiments selected from the present invention are described by the use of specific terminology, it should be understood that this is done solely by way of example, and that change and modification may be made without departing from the scope and spirit of the claims as described hereunder.