Abstract:
An apparatus and method are provided for retaining thermal transfer pins in a spreader plate adapted to transfer thermal energy from an electronic component. The spreader plate includes pin holes that slidably receive the thermal transfer pins. The apparatus includes a retention member located proximate each pin hole. The retention member interferes with a range of motion of an associated pin in order to retain the associated pin within the pin hole.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention generally relates to a process and apparatus for retaining conductive pins in pin holes of a spreader plate adapted for thermal transfer. More particularly, the present invention relates to a process for creating retention members about the pin holes to retain the conductive pins within a variable gap interface between the spreader plate and an electronic component.  
           [0002]    Electronic devices such as computers contain numerous circuit boards. Each circuit board generally has other electronic components, such as silicon microprocessor chips, mounted and electrically connected thereto. Often the electronic components are connected to the circuit board at an angle to the circuit board such that a top surface of the electronic component is also oriented at an angle to the circuit board. Additionally, the top surfaces of the electronic components may have contours or depressions such that the top surface is not flat or continuous. During operation, the electronic components generate a substantial amount of heat as electrical signals are sent between the electronic components and the circuit board. Typically, heat sinks are connected to the electronic components to absorb and dissipate the heat created by the electronic component. Because the electronic component may have an angled or variably interrupted top surface, most heat sinks do not uniformly contact the electronic component. Hence, the heat sinks do not absorb heat from the electronic component as efficiently as possible when directly connected to the electronic component.  
           [0003]    In the past, a thermally conductive coating containing grease and any one of ceramic, boron or aluminum has been applied to the top surface of an electronic component and covered with a compliant pad. The compliant pad is then covered with additional thermally conductive coating and a heat sink is then positioned on top of the compliant pad. The thermally conductive coating and the compliant pad engage the contours, depressions, and angles of the top surface of the electronic component and conduct heat from the electronic component through the compliant pad to the heat sink.  
           [0004]    However, the thermally conductive coating and compliant pad suffer from several drawbacks. First, though the thermally conductive coating is more conductive than air, it is not an overly efficient substance for conducting heat from the electronic component to the heat sink. Additionally, the compliant pad is thick and therefore does not efficiently conduct heat.  
           [0005]    Recently, a metal thermal transfer intermediary for use between the electronic component and the heat sink has been proposed using a metal spreader plate and a metal variable gap interface (VGI). The spreader plate has a front surface that retains at least one variable gap interface and a flat uninterrupted rear surface. The variable gap interface has a metal base with an array of pin holes. A spring sits in the bottom of each pin hole and supports a metal cylindrical pin such that a portion of the pin extends out of a mouth of the pin hole. The pin may be pushed downward further into the pin hole with the spring being compressed between the pin and the bottom of the pin hole.  
           [0006]    In operation, the pins, metal base, and the interior of the pin holes are covered with a thin layer of the thermal conductive coating. The spreader plate is then inverted and positioned on top of the electronic component such that the pins engage and rest on the top surface of the electronic component. The pins support the spreader plate and are pushed into the pin holes. Groups of pins are located within regions of the spreader plate to engage portions of the top surface of the electronic component that may have a different angle, contour, or depth. Thus, the use of several pins allows for the variable gap interface to engage much of the top surface of the electronic component despite the variable topographical features of the top surface. The rear surface of the spreader plate is then covered with a layer of the thermal conductive coating and the heat sink is then positioned on top of the rear surface of the spreader plate.  
           [0007]    Heat is conducted from the top surface of the electronic component to the pins, which in turn conduct the heat through the spring and the metal base through the rear surface of the spreader plate to the heat sink. The use of the retractable metal pins held in a metal base and metal spreader plate efficiently conducts the heat from the electronic component to the heat sink. Additionally, the thermally conductive coating fills in air gaps between the electronic component, the variable gap interface, the spreader plate, and the heat sink to further enhance the thermal conductivity of the assembly.  
           [0008]    However, the variable gap interface suffers from drawbacks as well. In the recently proposed variable gap interface, the pins are loosely positioned within the pin holes and the thermally conductive coating on the top of the pins sticks to the electronic component. Thus, the pins are pulled out of the variable gap interface when the variable gap interface is removed from the electronic component. Additionally, the pins may fall out of the pin holes whenever the spreader plate is inverted for positioning on the electronic component.  
           [0009]    A need remains for a variable gap interface that overcomes the above problems and addresses other concerns experienced in the prior art.  
         BRIEF SUMMARY OF THE INVENTION  
         [0010]    Certain embodiments of the present invention concern methods and apparatus for retaining thermal transfer pins in a spreader plate adapted to convey thermal energy from an electronic component. The spreader plate includes pin holes that slidably receive the thermal transfer pins. The thermal transfer pins move along a range of motion within the pin holes. The apparatus includes a retention member located proximate each pin hole. The retention member interferes with and defines a limit for the range of motion of an associated pin in order to retain the associated pin within the pin hole. 
       
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 illustrates a front isometric view of a spreader plate formed according to an embodiment of the present invention.  
         [0012]    [0012]FIG. 2 illustrates a rear isometric view of the spreader plate of FIG. 1.  
         [0013]    [0013]FIG. 3 illustrates a side view of a heat dissipating assembly formed according to an embodiment of the present invention.  
         [0014]    [0014]FIG. 4 illustrates a cutaway side partial view of a variable gap interface (VGI) with a pin retained in a first pin hole proximate an empty second pin hole formed according to an embodiment of the present invention.  
         [0015]    [0015]FIG. 5 illustrates an exploded partial isometric view of a VGI, a spring, and a pin formed according to an embodiment of the present invention.  
         [0016]    [0016]FIG. 6 illustrates an exploded partial isometric view of a VGI, a spring, a pin and a peening tool formed according to an embodiment of the present invention.  
         [0017]    [0017]FIG. 7 illustrates an isometric partial view of a portion of a peening tool formed according to an embodiment of the present invention.  
         [0018]    [0018]FIG. 8 illustrates an isometric partial view of a peening tool engaging a pin and the metal base of a VGI formed according to an embodiment of the present invention.  
         [0019]    [0019]FIG. 9 illustrates a cutaway side partial view of a peening tool engaging a pin and the metal base of a VGI formed according to an embodiment of the present invention.  
         [0020]    [0020]FIG. 10 illustrates a cutaway side partial view of a peening tool, pin, and VGI formed according to an embodiment of the present invention.  
         [0021]    [0021]FIG. 11 illustrates a cutaway side partial view of a pin formed according to an embodiment of the present invention.  
         [0022]    [0022]FIG. 12 illustrates a cutaway side partial view of a pin retained in a pin hole formed according to an embodiment of the present invention.  
         [0023]    [0023]FIG. 13 illustrates a cutaway side partial view of a pin retained in a pin hole formed according to an embodiment of the present invention. 
     
    
       [0024]    The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, certain embodiments. It should be understood, however, that the present invention is not limited to the arrangements and instrumentality shown in the attached drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0025]    [0025]FIG. 1 illustrates a front isometric view of a spreader plate  10  formed according to an embodiment of the present invention. The spreader plate  10  is rectangular and made of a thermally conductive metal such as aluminum. The spreader plate  10  has a front surface  30 , from which extends thermal variable gap interfaces (VGIs)  14  formed therewith. The VGIs  14  are square in shape and include a metal base  26  containing an array of pin holes  22  (FIG. 4) that retain corresponding pins  18 . The pins  18  are thermally conductive and retractably held within the pin holes  22  such that the pins  18  may be pushed into the pin holes  22  along a range of motion. During assembly, the pins  18 , pin holes  22 , and the metal base  26  of each VGI  14  are covered with a layer of a thermally conductive coating  46  (FIG. 3), such as a mixture of grease and any one of ceramic, boron, or aluminum.  
         [0026]    [0026]FIG. 2 illustrates a rear isometric view of the spreader plate  10  of FIG. 1. The spreader plate  10  has a flat rear surface  34  that is also covered with the thermally conductive coating  46  (FIG. 3) during assembly.  
         [0027]    [0027]FIG. 3 illustrates a side view of a heat dissipating assembly  54  formed according to an embodiment of the present invention. An electronic component  42  (for example, a silicon microprocessor chip) is connected to, and extends from, a circuit board  38 . The spreader plate  10  is then positioned on top of the electronic component  42  such that the pins  18  of the VGIs  14 , which are covered with the thermally conductive coating  46 , are firmly pressed against a top surface  168  of the electronic component  42  and compressed by different amounts within the pin holes  22  (FIG. 4) in order to accommodate the variable surface features of the electronic component  42 . A heat sink  50  is then connected to the rear surface  34  of the spreader plate  10 , which is also covered with the thermally conductive coating  46 . In operation, the electronic component  42  generates heat that is conducted from the electronic component  42  through the thermally conductive coating  46  to the pins  18 . The pins  18  are partially retracted into the pin holes  22  (FIG. 4) and conduct the heat through the rear surface  34  of the spreader plate  10  and through another layer of thermally conductive coating  46  to the heat sink  50  which absorbs and dissipates the excess heat.  
         [0028]    [0028]FIG. 4 illustrates a cutaway side partial view of a VGI  14  with a pin  18  retained in a first pin hole  22  proximate an empty second pin hole  22  formed according to an embodiment of the present invention. Each pin hole  22  has an inner wall  58  extending into the metal base  26  from a cylindrical mouth  62  at a front surface  114  of the metal base  26  to a pointed bottom portion  66  defined by angled walls  90 . A portion of the front surface  114  of the metal base  26  is deformed about the mouth  62  of the pin hole  22  to form retention material or retention members  110 .  
         [0029]    The pin holes  22  each receive and retain a spring  70  and a pin  18 . The spring  70  has a top end  106  and a bottom end  86 . The pin  18  is cylindrical and has first and second segments  74  and  78 . The first segment  74  has a smaller diameter than the second segment  78  such that the pin  18  has a stepped outer surface defined by outer walls  118  and  122  of the first and second segments  74  and  78 , respectively. A ledge  82  is located at an intersection between the first and second segments  74  and  78 . The first segment  74  has a top surface  102  and the second segment  78  has a bottom surface  94 .  
         [0030]    In operation, the spring  70  is compressed in the pin hole  22  between the bottom portion  66  and the pin  18 . The bottom end  86  of the spring  70  is resistibly engaged by the angled walls  90  of the bottom portion  66  and the top end  106  of the spring  70  is resistibly engaged by the bottom surface  94  of the pin  18 . The compressed spring  70  pushes the pin  18  upward in the direction of arrow A. The first segment  74  of the pin  18  extends up through the mouth  62  out of the pin hole  22 . The retention members  110  extending along the front surface  114  of the metal base  26  resistibly engage the ledge  82  downward in the direction of arrow B such that the second segment  78  of the pin  18  is retained within the pin hole  22  and engaging the spring  70  at the top end  106 .  
         [0031]    The pin  18  may be positioned downward further into the pin hole  22  in the direction of arrow B such that the ledge  82  no longer engages the retention members  110  and the spring  70  is further compressed between the pin  18  and the angled walls  90  of the bottom portion  66 . Also, the retention members  110  hold the pin  18  in the pin hole  22  such that the VGI  14  may be inverted upside down without the pin  18  falling out of the pin hole  22 . Thus, the VGI  14  may be positioned on the electronic component  42  (FIG. 3) without the pins  18  falling out of the pin holes  22 . Additionally, the pins  18  may be pushed further into the pin holes  22  as the pins  18  are resistibly engaged by the top surface  168  (FIG. 3) of the electronic component  42 . Because each pin  18  retracts individually, the VGI  14  may be firmly pressed against an electronic component  42  having an angled, variable, or contoured top surface  168  with each pin  18  engaging the top surface  168 . Heat is conducted from the electronic component  42  through the thermally conductive coating  46  (FIG. 3) to the pin  18 . The pin  18 , in turn, conducts the heat to the spring  70 , which conducts the heat into the metal base  26  at the bottom portion  66  of the pin hole  22 . The heat is then conducted through the metal base  26 , the rear surface  34  (FIG. 2) of the spreader plate  10  (FIG. 2), and the thermally conductive coating  46  to the heat sink  50  (FIG. 3).  
         [0032]    [0032]FIG. 6 illustrates an exploded partial isometric view of a VGI  14 , a spring  70 , a pin  18  and a peening tool  126  formed according to an embodiment of the present invention. The peening tool  126  has a cylindrical body  130  formed with a head  134 . A contact end  138  of the body  130  opposite the head  134  has two rounded deformation beams  142  oriented on opposite sides of the contact end  138  and directed outward from the body  130 .  
         [0033]    [0033]FIG. 7 illustrates an isometric partial view of a portion of the peening tool  126 . The body  130  contains a flat pin contact surface  146  that is set back a short distance from the contact end  138  to define a cavity  139  that accepts a portion of the pin  18 . The pin contact surface  146  engages the top surface  102  (FIG. 6) of the pin  18  (FIG. 6) when the peening tool  126  is used to secure the pin  18  in the VGI  14  (FIG. 6).  
         [0034]    Returning to FIG. 6, during assembly, the spring  70  is first inserted into the pin hole  22 . The pin  18  is then inserted downward in the direction of arrow B into the pin hole  22  on top of the spring  70  such that the bottom surface  94  of the pin  18  engages the top end  106  of the spring  70 . The pin  18  rests atop the spring  70  such that the ledge  82  of the pin  18  extends out of the pin hole  22  above the front surface  114  of the metal base  26 . The peening tool  126  is then slid over the pin  18  until the cavity  139  receives the first segment  74  of the pin  18  and the top surface  102  of the pin  18  engages the pin contact surface  146  (FIG. 7) of the peening tool  126 .  
         [0035]    As shown in FIG. 8, the peening tool  126  is then pushed downward against the VGI  14  such that the deformation beams  142  engage the front surface  114  of the VGI  14  proximate the mouth  62  of the pin hole  22 . The pin contact surface  146  (FIG. 7) pushes the pin  18  into the pin hole  22  in order that the ledge  82  (FIG. 6) moves slightly below the front surface  114  of the metal base  26  about the mouth  62  of the pin hole  22 . The peening tool  126  is then struck on the head  134  in the direction of arrow B such that the deformation beams  142  deform portions of the metal base  26  proximate the mouth  62 , thereby forming the retention members  110  (FIG. 4).  
         [0036]    Alternatively, during mass assembly of the VGIs  14 , an array of peening tools are assembled to a press. Each VGI  14  on a spreader plate  10  (FIG. 1) is then positioned under the array of peening tools such that each pin hole  22  is aligned with a peening tool. The press is then closed down on the VGI  14  such that the peening tools deform the front surface  114  of the metal base  26  about all the mouths  62  of the VGI  14  at once. Thus, incorporating an array of peening tools with a press allows for the creation of retention members  110  (FIG. 4) on a mass scale.  
         [0037]    [0037]FIG. 5 illustrates an exploded partial isometric view of a VGI  14 , a spring  70 , and a pin  18  along with an array of pins  18  retained in pin holes  22  by the retention members  110 . The retention members  110  created by the deformation beams  142  (FIG. 8) in the front surface  114  of the metal base  26  are located on opposite sides of the mouth  62  of each pin hole  22 . The retention members  110  resistibly engage the ledges  82  of the pins  18  to retain the pins  18  within the pin holes  22 . Portions of the first segments  74  of the pins  18  retractably extend out of the pin holes  22 . The VGI  14  may thus be inverted and positioned on top of the electronic component  42  (FIG. 3) such that the top surfaces  102  of the pins  18  engage the top surface  168  (FIG. 3) of the electronic component  42 .  
         [0038]    Alternatively, all the material around the mouth  62  of the pin hole  22  may be deformed by a peening tool with a cylindrical deformation beam such that a circular retention member is formed about the mouth  62  to engage the entire ledge  82  of each pin  18 .  
         [0039]    [0039]FIG. 9 illustrates a cutaway side partial view of a peening tool  126  engaging a pin  18  and the metal base  26  of a VGI  14 . The body  130  of the peening tool  126  has an inner diameter defined by an inner wall  148  and an outer diameter defined by an outer wall  150 . The inner diameter of the body  130  is greater than the outer diameter of the first segment  74  but slightly less than the outer diameter of the second segment  78  and the diameter of the pin hole  22 . The outer diameter of the body  130  is greater than the outer diameter of the second segment  78  and the diameter of the pin hole  22 . The deformation beams  142  have impact edges  154  that extend at an acute angle to a horizontal axis  158  from the outer wall  150  to the inner wall  148  of the body  130  to define impact tips  162  along the outer wall  150 .  
         [0040]    The peening tool  126  as shown in FIG. 9 is in an alignment stage where the first segment  74  of the pin  18  is received in the body  130  of the peening tool  126  between the deformation beams  142 . The peening tool  126  is positioned on the VGI  14  such that the impact tips  162  engage the metal base  26  about the mouth  62  of the pin hole  22 . The pin contact surface  146  engages the top surface  102  of the pin  18  such that the pin  18  is retained in the pin hole  22  with the ledge  82  slightly beneath the front surface  114  of the metal base  26 . The spring  70  is thus compressed between the bottom surface  94  of the pin  18  and the angled walls  90  of the pin hole  22 .  
         [0041]    [0041]FIG. 10 illustrates a cutaway side partial view of the peening tool  126 , pin  18 , and VGI  14  formed according to an embodiment of the present invention. The peening tool  126  is in an impact stage where it has been struck downward in the direction of arrow B such that the impact tips  162  have pushed into the front surface  114  of the metal base  26  and deformed portions of the front surface  114  about the mouth  62  of the pin hole  22  to form the retention members  110 . The retention members  110  resistibly engage the ledge  82  of the pin  18  to hold the pin  18  in the pin hole  22 . The peening tool  126  is then removed and used to secure another pin  18  into a pin hole  22 .  
         [0042]    [0042]FIG. 11 illustrates a cutaway side partial view of a pin  200  formed according to an alternative embodiment of the present invention. The pin  200  has first and second segments  204  and  208  having the same outer diameters and that are separated by a small groove  212  in the exterior perimeter of the pin  200 . The pin  200  along the groove  212  has a smaller diameter than the first and second segments  204  and  208 . As the spring  70  pushes the pin  200  upward in the direction of arrow A, the retention members  110  of the VGI  14  are received in the groove  212  and resistibly engage the pin  200  along a ledge  216  of the groove  212  to retain the pin  200  in the pin hole  22 . The retention members  110  are created around the groove  212  of the pin  200  by use of the peening tool  126  shown in FIGS.  9 - 10 . The groove  212  receives the retention members  110  such that the pin  200  may be depressed in the direction of arrow B into the pin hole  22  when the VGI  14  is positioned on the electronic component  42  (FIG. 3).  
         [0043]    [0043]FIG. 12 illustrates a cutaway side partial view of the pin  18  retained in the pin hole  22  formed according to an embodiment of the present invention. A thin metal plate clip  300  is connected to the front surface  114  of the metal base  26  and has an aperture with a smaller diameter than the diameter of the second segment  78 . The aperture is positioned about the mouth  62  and receives the first segment  74  of the pin  18 . The plate clip  300  has a bottom resistance surface  304  that resistibly engages the ledge  82  of the pin  18  about the mouth  62 . The spring  70  pushes the pin  18  upward in the direction of arrow A within the pin hole  22  such that the ledge  82  is resistibly engaged by the resistance surface  304  of the plate clip  300  to retain the pin  18  in the pin hole  22 . The pin  18  is depressed in the direction of arrow B into the pin hole  22  against the spring  70  when the pin  18  is positioned against the electronic component  42  (FIG. 3).  
         [0044]    [0044]FIG. 13 illustrates a cutaway side partial view of a pin  400  retained in the pin hole  22  formed according to an embodiment of the present invention. The pin  400  has first and second outer segments  404  and  408  having the same outer diameters and that are separated by a peripheral notch  412  extending about the pin  400 . The peripheral notch  412  includes a lower ledge  416  and an upper ledge  418 . A thin metal plate clip  420  is connected to the front surface  114  of the metal base  26  and has an aperture with a smaller diameter than the diameters of the first and second outer segments  404  and  408 . The aperture is positioned about the mouth  62  and receives the peripheral notch  412  of the pin  400 . The plate clip  420  has a bottom resistance surface  424  and a top resistance surface  430 . The bottom resistance surface  424  resistibly engages the lower ledge  416  of the pin  18  about the mouth  62 . A thick cap  440  is connected to the plate clip  420  and has an aperture with a diameter generally equal to the diameter of the pin hole  22  and slightly greater than the diameter of the first outer segment  404 . The spring  70  pushes the pin  400  upward in the direction of arrow A within the pin hole  22  such that the lower ledge  416  is resistibly engaged by the bottom resistance surface  424  of the plate clip  420  to retain the pin  400  in the pin hole  22 . The pin  400  is depressed in the direction of arrow B into the pin hole  22  when the pin  400  is positioned on the electronic component  42  (FIG. 3) such that the upper ledge  418  of the first outer segment  404  engages the top resistance surface  430  of the plate clip  420 . The cap  440  surrounds the first outer segment  404  to guide and support the first outer segment  404  as the pin  18  is depressed in the direction of arrow B into the pin hole  22 .  
         [0045]    The method and apparatus for retaining the pins in the VGI provides several benefits. Deforming the metal around the mouth of the pin holes to engage a ledge or groove in the pins holds the pins within the pin holes when the VGI is inverted. Thus, the VGI can be used in orientations where the pins are turned upside down to be applied to an electronic component. Also, the retention material retains the pins against the compressed springs in the pin holes such that the first segments of the pins are always extending out of the pin holes when the VGI is unengaged and the first segments can be pushed down into the pin holes when the VGI is engaged against an electronic component. Thus, the retention members allow the pins to efficiently conduct heat away from the electronic component when the electronic component is in any number of orientations and has a variable surface.  
         [0046]    While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.