Patent Publication Number: US-2007102795-A1

Title: Radiator plate and semiconductor device

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to a radiator plate for effectively radiating heat generated in a semiconductor element on a semiconductor device and the semiconductor device using the same.  
      2. Description of Related Art  
      In recent years, with advancement of high speed of a semiconductor element loaded on a semiconductor device, the heat value generated in the semiconductor element has increased. When temperature of the semiconductor element increases to a certain temperature or more, its required operation characteristic cannot be obtained. So in the semiconductor device with the semiconductor element having large quantity of generated heat, a radiator plate, radiating fin or draft fan for externally dissipating the heat generated in the semiconductor element is used to prevent the semiconductor element from being excessively heated.  
       FIG. 7  shows examples in which a radiator plate is attached to a semiconductor device for a memory buffer used in a memory module. In an example shown in  FIG. 7A , a metallic cap  12  is attached to a substrate  10  on which a semiconductor element is loaded. In an example shown in  FIG. 7B , a radiator plate  14  formed of a thick plate is attached to the substrate  10 . In an example shown in  FIG. 7C , a radiator plate  16  equipped with radiating fins  16   a  is attached to the substrate  10 . In all these examples, the radiating plate is attached to a side of the substrate  10  on which the semiconductor element is mounted so that an inner surface of the cap  12  or a lower surface of the radiator plate  14 ,  16  abuts on a back surface of the semiconductor element.  
      When the heat value in the semiconductor element increases, in the technique for attaching the metallic cap or the radiator plate to the semiconductor device to thereby radiate from the semiconductor element, there is a fear that its temperature cannot be kept at a temperature capable of assuring the operating characteristic of the semiconductor element.  
      For example, also in the above semiconductor device for the memory buffer, when the heat value generated in the semiconductor element increases, heat is accumulated internally in the case where the metallic cap  12  is employed. Thus, sufficient radiating effect cannot be obtained. Further, in the case where the radiator plate  14 ,  16  is employed, when the heat value generated in the semiconductor element increases, the temperature of the semiconductor element cannot be reduced to a predetermined operating temperature or lower.  
      The heat radiating characteristic of the semiconductor element can be also improved by increasing a surface area of the radiator plate in such a manner that size of the radiator plate attached to the substrate or the radiating fins is increased. However, where the large radiator plate is employed, downsizing of the product is hindered. When the product where a plurality of modules are arranged in a small space as in the memory module, increasing the size of the radiating fins is restricted. In view of these facts, a radiating plate which is small in size and can give an excellent heat dissipating effect has been demanded.  
     SUMMARY OF THE INVENTION  
      In order to solve the above problem, this invention has been accomplished. An object of this invention is to provide a radiator plate capable of effectively radiating heat generated in a semiconductor element and not impairing the operating characteristic of the semiconductor element, and a semiconductor device using this radiator plate.  
      In order to attain the above object, this invention provides the following configurations.  
      According to a first aspect of the invention, there is provided a radiator plate mounted on a substrate so as to radiate heat generated in a semiconductor element on the substrate, the radiator plate comprising:  
      first radiating fins provided a first surface of the radiator plate which is an opposite surface of a second surface of the radiator plate which faces the substrate; and  
      second radiating fins on the second surface,  
      wherein a longitudinal direction of the second radiating fin is the same as a longitudinal direction of the first radiating fin, and  
      the second radiating fin is formed at a position which does not interfering with the semiconductor element.  
      According to a second aspect of the invention, as set forth in the first aspect of the invention, it is preferable that the radiator plate is formed in the same square planar shape as that of the substrate; and  
      the second radiating fins are provided at both side edges so as to assure a space for accommodating the semiconductor element therein.  
      According to a third aspect of the invention, as set forth in the first aspect of the invention, it is preferable that the first radiating fin and the second radiating fin are alternately arranged on both sides of the radiator plate.  
      The arrangement of “alternately” means that according to the position of a recess formed between the adjacent radiating fins on the one side and the other side of the radiator plate, the radiating fin is formed on the other side and one side of the radiator plate.  
      According to a fourth aspect of the invention, as set forth in the first aspect of the invention, it is preferable that the radiator plate is made of aluminum subjected to anodizing processing.  
      This permits heat to be effectively dissipated from the radiator plate.  
      According to a fifth aspect of the invention, there is provided a semiconductor device comprising:  
      a substrate;  
      a semiconductor element on the substrate;  
      the radiator plate as set forth in the first aspect of the invention  
      This semiconductor device gives excellent heat dissipation from the semiconductor element and high reliability.  
      According to a sixth aspect of the invention, as set forth in the fifth aspect of the invention, it is preferable that the semiconductor device further comprising:  
      an attachment spring that attaches the radiator plate to the substrate and comprises a depressing portion for depressing the first surface,  
      wherein the attachment spring is made of a wire body bent so as to be U-shape in side shape viewed from a longitudinal direction of the substrate and is provided with hook portions at both ends thereof,  
      at least one communicating space is formed on the first surface so as to extend in a direction perpendicular to the longitudinal direction of the first radiating fin and have a width equal to or larger than that of a slit space formed between the first radiating fins adjacent to each other, and  
      the attachment spring is attached to the radiator plate so that the depressing portion is fit in the communicating space.  
      By using the attachment spring formed by bending the wire body, the radiator plate can be very easily attached to the semiconductor device.  
      According to a seventh aspect of the invention, as set forth in the sixth aspect of the invention, it is preferable that at least one communicating space is formed at a symmetrical center line and on both sides relative to the symmetrical center line, respectively and  
      the attachment spring comprising a U-shape bending portion which extend in the both sides relative to the symmetrical center line, and  
      the attachment spring is attached to the radiator plate so that the depressing portion is fit in the communicating space and the slit space.  
      In this configuration, the radiator plate surely supported by the attachment spring can be attached to the semiconductor device.  
      According to an eighth aspect of the invention, as set forth in the eighth aspect of the invention, it is preferable that the radiator plate is mounted in the substrate so that the hook portions of the attachment spring are fixed in fixing holes in the substrate.  
      In this configuration, the radiator plate can be easily attached to the semiconductor device.  
      According to a ninth aspect of the invention, as set forth in the sixth aspect of the invention, it is preferable that the semiconductor device further comprises a heat transfer material disposed between the substrate and the radiator plate.  
      The fins may be formed such that corrugated portions extend in a longitudinal direction with constant intervals each other.  
      Since the radiator plate according to this invention is small in size and excellent in the radiating characteristic, the radiator plate of the invention can be effectively employed as a radiator plate for the semiconductor element having a large quantity of generated heat. Further, in a semiconductor device with this radiator plate, heat can be effectively radiated from the semiconductor element so that there is provided the semiconductor device in which the operating characteristic of the semiconductor element is not impaired and high reliability is given. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of the configuration of an embodiment of a radiator plate and a semiconductor device according to this invention;  
       FIG. 2  is a front view showing a status where a radiator plate is attached to a semiconductor device;  
       FIG. 3  is a plan view showing a memory module in which a radiator plate is attached to a semiconductor device;  
       FIG. 4  is a plan view showing a status where an attachment spring is attached to a semiconductor device;  
       FIG. 5  is a plan view showing a configuration of a radiator plate employed in a memory module;  
       FIGS. 6A and 6B  are a plan view and a side view of an attachment spring; and  
       FIGS. 7A, 7B  and  7 C are a perspective view of the semiconductor device provided with a radiator plate according to the related art. 
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION EMBODIMENTS  
       FIG. 1  is a perspective view of an exemplary configuration of the semiconductor device in which a radiator plate  20  according to this invention is attached to a substrate  10  on which a semiconductor element is loaded.  
      The radiator plate  20  according to this embodiment has a body  20   a , first radiating fins  20   b  formed on the one side of the body  20   a  (first surface) which is opposite to the surface facing the substrate  10  and second radiating fins  20   c  formed on the other side of the body  20   a  (second surface) which faces the substrate  10 .  FIG. 1  shows the status where the radiator plate  20  is attached to the substrate  10  on which the semiconductor element is mounted. The radiator plate  20  is formed in the same square planar shape as that of the substrate  10 , and is attached to the substrate  10  so that the second radiating fins  20   c  face the side of the substrate  10  on which the semiconductor element is loaded.  
      Pluralities of the first radiating fins  20   b  are arranged in parallel with constant intervals over an entire area of a planar region of the body  20   a.    
      On the other hand, the second radiating fins  20   c  are arranged at positions which does not interfere with the semiconductor element loaded in the substrate  10 , and the second radiating fins are also arranged so that their longitudinal direction agree with that of the first radiating fins  20   b . In this embodiment, along both side edges of the body  20   a , four second radiating fins  20   c  are formed, respectively. The region sandwiched by the second fins  20   c  formed on both side edges of the body  20   a  constitutes a region where the semiconductor element loaded on the substrate  10  is accommodated.  
       FIG. 2  shows the status when the semiconductor device with the radiator plate  20  attached to the substrate is seen from its front direction. A semiconductor element  11  is mounted on an element mounting face of the substrate  10  by flip-chip connection. The radiator plate  20  is attached to the substrate  10  so that the back surface of the semiconductor element  11  abuts on a lower surface of the body  20   a . In order that the lower surface of the radiating plate  20  abuts on the back surface of the semiconductor element  11  when the radiator plate  20  is attached to the substrate  10 , actually, the quantity of projection (projection height) of the second radiating fins  20   c  from the body  20   a  is made slightly lower than the projection height of the semiconductor element  11  from the element mounting surface of the substrate  10 . Between the back surface of the semiconductor element  11  and the radiator plate  20 , a heat conducting material  11   a  having excellent thermal conductivity is disposed so that heat is effectively conducted from the semiconductor element  11  to the radiator plate  20 .  
      As described above, the first radiating fins  20   b  and second radiating fins  20   c  are formed in the radiator plate  20  so that their longitudinal directions are in parallel to each other. When seeing the radiator plate  20  attached to the substrate  10  from the front direction, the first radiating fins  20   b  and the second radiating fins  20   c  provide communicating spaces in a direction crossing the radiating plate in its front/rear direction. Further, since the semiconductor element  11  is located at an intermediate position between the second radiating fins  20   c  formed on both side edges of the radiator plate  20  so as to be apart by a predetermined distance from the second radiating fins  20   c , communication spaces are formed between the semiconductor element  11  and second radiating fins  20   c  in the front/rear direction of the radiator plate  20 .  
      Thus, in the semiconductor device provided with the radiator plate  20  according to this embodiment, by supplying air from a blower fan in a direction indicated by an arrow in  FIG. 1 , air supply is not hindered by the first radiating fins  20   b  and the second radiating fins  20   c . Thus, by ventilating the communication spaces for the radiating fins  20   b ,  20   c , the radiating fins  20   b ,  20   c  can be effectively cooled so that the radiating characteristic from the semiconductor element  11  can be improved.  
      Further, in the radiator plate  20  according to this embodiment, in the face (lower side) of the body  20   a  facing the substrate  10 , the second radiating fins  20   c  are formed. Owing to this, the surface area of the entire radiator plate  20  can be made larger than a case where the radiating fins are formed only on the one side of the radiator plate. This also permits the radiating characteristic to be improved.  
      In this embodiment, the radiator plate  20  is made of a material of aluminum. The aluminum plate is processed to form the first radiating fins  20   b  and second radiating fins  20   c . Thereafter, the material is subjected to anodizing processing so that the entire outer surface of the radiator plate  20  is colored in black. In this way, by using aluminum as the material of the radiator plate  20  and subjecting the surface of the material to the anodizing processing, the radiating characteristic of the radiator plate  20  can be improved as compared with the radiator plate not subjected to the anodizing processing.  
      Incidentally, the radiator plate may be made of a metallic material other than aluminum, e.g. copper, iron or the metallic material plated with nickel. However, if using the radiator plate with its surface being metallic glossy, this gives rise to filling of internal heat and so is not effective in order to acquire the effective radiating characteristic. Thus, when the metallic material other than aluminum is employed, by anodizing the surface of the radiator plate through oxidation processing, etc., the radiating characteristic of the radiator plate can be improved.  
      In the radiator plate  20  employed in this embodiment, as seen from  FIG. 2 , the first radiating fins  20   b  and the second radiating fins  20   c  are alternately arranged on both sides of the body  20   a . Specifically, the second radiating fin  20   c  is formed according to a recess formed between the first radiating fins  20   b  adjacent to each other. On the other hand, the first radiating fin  20   b  is formed according to a recess formed between the second radiating fins  20   c  adjacent to each other. As described above, when the first radiating fins  20   b  and the second radiating fins  20   c  are alternately arranged on both sides of the body  20   a , for example, the second radiating fins  20   c  can be formed by like half-cutting a metallic plate. Thus, the first radiating fins  20   b  and the second radiating fins  20   c  can be easily integrally formed as projections on both sides of the radiator plate  20 .  
       FIG. 3  shows a memory module with a semiconductor device for a memory buffer in which a radiator plate  22  is attached to the semiconductor device. On both sides of a mounting board (substrate)  30  of this memory module, mounted are a semiconductor device for a memory buffer and semiconductor memories  32 . At the one side edge of the mounting board  30 , a connecting terminal  34  is formed.  
      On the outer surface of the semiconductor device mounted on the mounting board  30 , a radiator plate  22  is attached via an attachment spring  40 . The attachment spring  40  serves to attach the radiator plate  22  so that it is forcibly brought into contact with the back surface of the semiconductor element loaded on the semiconductor device.  
       FIG. 5  is a perspective view of a radiator plate  22  which is attached to a semiconductor device using an attachment spring  40 . This radiator plate  22 , like the radiator plate  20  shown in  FIG. 1 , includes first radiating fins  22   b  and second radiating fins  22   c  formed on the one side and other side of a body  22   a , respectively. In the radiator plate  22  according to this embodiment, the first radiating fins  22   b  are divided into four parts in the longitudinal direction so that communicating spaces A which are linearly continued in a direction perpendicular to the longitudinal direction of the radiator plate  22   b . The first radiating fins  22   b  are divided into four parts so that three communicating spaces A are provided in an arrangement continuing in the width direction of the radiator plate  22 . The communicating spaces Aare formed to have a width nearly equal to that of slit spaces B formed between the radiating fins  22   b  adjacent to each other in the width direction. Since the communicating spaces A are provided, when the radiator plate  22  is seen from top (in a plane direction), the end faces of rectangles of the first radiating fins  22   b  are aligned to provide the communicating spaces A and slit spaces B in rows and columns.  
       FIG. 4  is an enlarged view of the status where the attachment spring  40  is attached to the radiator plate  22 .  FIG. 6A  is a plan view of the attachment spring  40 .  FIG. 6B  is a side view thereof.  
      The attachment spring  40  is made of a wire body having elasticity. In the plane direction, as seen from  FIG. 6A , the attachment spring  40  is configured so that bending portions  40   a ,  40   b  hang over rightward and leftward with respect to a symmetrical center line (C-C line) so as to form square frames (U-shapes). In the side direction, as seen from  FIG. 6B , seen from a longitudinal direction of the substrate (transversal direction in  FIG. 3 ), the attachment spring  40  is configured to provide a gate shape in which upright segments  40   c ,  40   c  are bent in an U-shape. The upright segments  40   c ,  40   c  are provided with hook portions  40   d  at their tips, respectively. The hook portions  40   d  are bent in reverse directions at the one end and the other end of the attachment spring  40 .  
      The area formed by bending and bridging the wire body between the upright segments  40   c ,  40   c  serves as a depressing portion  40   e  for elastically depressing the radiator plate  22  when the radiator plate  22  is attached to the semiconductor device. As seen from  FIG. 6B , in the attachment spring  40  according to this embodiment, the coupling portions between the upright segments  40   c  and the depressing portion  40   e  are bent at an acute angle so that the function of the depressing portion  40   e  of elastically depressing the radiator plate  22  is kept.  
      As seen from  FIG. 4 , the attachment spring  40  is attached to the radiator plate  22  by inserting the wire body of the attachment spring  40  into the communicating spaces A and slit spaces B on the side of the radiator plate  22  where the first radiating fins  22   b  are formed. The wire body constituting the attachment spring  40  has an outer diameter precisely fit in the communicating spaces A and slit spaces B. Thus, by inserting the wire body into the communicating spaces A and the slit spaces B, the attachment spring  40  is attached to the radiator plate  22 .  
      The bending shape of the bending portion  40   a ,  40   b  formed in the depressing portion  40   e  of the attachment spring  40  is preliminary designed so as to be inserted in the communicating spaces A and the slit spaces B according to the arrangement of the radiating fins of the radiator plate  22  and the arrangement of the communicating spaces A and the slit spaces B.  
      The attachment spring  40  is attached to the radiator plate  22  so that the position of the upright segments  40   c ,  40   c  agrees to the position of the communicating space A passing the symmetrical center line position of the radiator plate  22 . When attaching the attachment spring  40  to the radiator plate  22 , the radiating fins  22   b  serve as guides for inserting the wire body of the attachment spring  40  into the communicating spaces A and the slit spaces B so that the attachment spring  40  can be easily positioned on the radiator plate  22 . In the status where the attachment spring  40  has been mounted in the radiator plate  22 , the attachment spring  40  is sandwiched by the radiating fins  22   b  and so preliminary fixed. Thus, with the attachment spring  40  being attached to the radiator plate  22 , the radiator plate  22  can be easily attached to the semiconductor device.  
      The radiator plate  22  can be mounted in the mounting board  30  by attaching the attachment spring  40  to the radiator plate  22  and fixedly inserting the hook portions  40   d  in fixing holes  31  formed in the mounting board  30 . By fixing the hook portions  40   d  in the fixing holes  31 , the radiator plate  22  is mounted in the mounding board  30  in a state positioned relative to the semiconductor device with the internal face of the radiator plate  22  being depressed on the semiconductor element loaded on the semiconductor device.  
      The height of the upright segments  40   c ,  40   c  of the attachment spring  40  is set so that the radiator plate  22  elastically abuts on the back surface of the semiconductor device loaded on the semiconductor device when the hook portions  40   d  are fixed in the fixing holes  31  of the mounting board  30 . Further, since the attachment spring  40  is provided with the bending portion  40   a ,  40   b  hanging over leftward and rightward, it serves to press the radiator plate  22  with a face contact state. Thus, the radiator plate  22  can be surely supported in a state forcibly kept in contact with the semiconductor element.  
      In the memory module in which the semiconductor device provided with the radiator plate  22  according to this embodiment, the radiating function of the radiator plate  22  effectively acts. So, by supplying air to the memory module from the blower fan, the operating temperature of the semiconductor element in an operating state of the semiconductor device can be lowered to a required temperature or lower.  
      Further, in this embodiment, the radiator plate  22  is downsized by forming its outer shape in the same shape as the planar shape of the semiconductor device. This preferably contributes to space saving. Further, since the attachment spring  40  is attached to the radiator plate in such a manner that its depressing portion  40   e  is fit in the communicating spaces A and slit spaces B, the depressing portion  40   e  of the attachment spring  40  enters internally from the end face of each the radiating fins  22   b . Thus, the attachment spring  40  attached to the radiator plate is not obstructive in mounting the semiconductor device.  
      Further, since the radiator plate  22  is attached to the mounting board  30  using the attachment spring  40 , its attaching operation can be easily executed. Furthermore, since the attachment spring  40  is formed by bending the wire body, it can be manufactured at low cost.  
      The attachment spring  40  employed in the above embodiment is formed to have the depressing portion  40   e  with the bending portion  40   a ,  40   b  having a U-shape hanging over leftward and rightward, and its wire body is fit in the adjacent spaces of the radiating fins  22   b  arranged in an aligned manner. The depressing portion  40   e  of the attachment spring  40  is not limited to such a configuration, but may be appropriately designed to be fit between the adjacent radiating fins  22   b.    
      While the invention has been described in connection with the exemplary embodiments, it will be obvious to those skilled in the art that various changes and modification may be made therein without departing from the present invention, and it is aimed, therefore, to cover in the appended claim all such changes and modifications as fall within the true spirit and scope of the present invention.