Abstract:
A system for delivering power to a processor enables a DC-to-DC converter substrate to be secured to the processor carrier in the Z-axis direction. The ability to assemble the converter to the processor in this way facilitates assembly compared to systems in which the converter is plugged in to the processor carrier in the direction substantially parallel to the surface of the motherboard.

Description:
BACKGROUND 
     This invention relates generally to power delivery to electronic circuits and particularly to an improved power delivery system for supplying power from a power source to a processor. 
     In a typical computer system, a large printed circuit known as a “motherboard” contains a number of basic components. The motherboard is supplied with voltage from a power supply. The motherboard includes connectors for daughter boards that can be plugged in to provide additional capabilities. Such boards, for example, may provide an interface to disk drives and compact disk read only memories, and may provide modem interfaces for local area networks and the like. 
     Processors operate at lower voltages than some other components on the motherboard. However, because of their high speed, processors consume large amounts of power despite the fact that they use lower voltages. Since the processor is operating at a low voltage with high power, the current required by the processor is large. A localized DC-to-DC converter (known as a voltage regulator module (VRM) or power pod) reduces the main supply voltage for supplying the processor, for example. Typically for Intel 32 bit processors, this DC-to-DC converter plugs into a connector on the motherboard. The lower voltage is then conducted through printed circuit traces on the motherboard to the processor socket. For higher current Intel 64 bit processors, the DC-to-DC converter connects directly to the processor package through an edge connector because of the high loss associated with conveying power through two connectors and the motherboard as in Intel 32-bit systems. The power connector may also provide signal connections related to power supply issues. 
     Conventionally, the processor is plugged into the motherboard in a direction that is transverse to the plane of the motherboard. If the plane of the motherboard defines the X and Y directions, the processor is plugged into the motherboard in the Z-axis direction. In other words, the processor is moved from a position above the motherboard downwardly to plug into the motherboard. Conventionally, the DC-to-DC converter is plugged onto the processor package edge in a direction that is generally parallel to the surface of the motherboard (transverse to the Z-axis direction). 
     This configuration results in a number of difficulties. With the processor already attached to the motherboard, the action of plugging the converter into the processor carrier along the surface of the motherboard (e.g., the X-axis direction) is prone to interference from upwardly directed components already on the motherboard. Moreover, there is little room to manipulate the converter connections along the motherboard. The interconnection of the converter and the processor carrier is awkward, increasing the demands on assembly workers and requiring more elaborate interconnection devices. A complex rigid mount mechanism is used to align the processor package and the DC-to-DC converter in both the Z and X axes. This takes up a large amount of motherboard real estate. 
     Thus, there is a need for an improved way of delivering power to a processor package edge. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevational view of one embodiment of the invention in the course of assembly; 
     FIG. 2 is a top plan view of the embodiment shown in FIG. 1; 
     FIG. 3 is an enlarged, partial, bottom plan view of the DC-to-DC converter substrate planar power contacts shown in FIG. 1; and 
     FIG. 4 is a cross-sectional view taken generally along the line  4 — 4  in FIG.  2 . 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, a processor power delivery system  10  enables a DC-to-DC converter  12  to be assembled to a processor carrier  18  in the Z-axis. The Z-axis (indicated by an arrow in FIG. 1) is the direction that is transverse to the surface of a motherboard  28  and transverse to the lengths of the converter  12  and the processor carrier  18 . 
     The processor carrier  18  may be plugged into a socket  50  that in turn plugs into a motherboard  28 , all in the Z-axis direction. A processor  52  may be attached on the carrier  18 , for example using surface mount solder balls  20 , to a connection layer  21 . Thereafter, the converter  12 , including components  54 , may plugged atop the processor carrier  18  also in the Z-axis direction. This greatly facilitates the connection of the two units. 
     The converter  12  includes contacts  16  on its lower surface  14  to make direct surface to surface contact with the processor carrier  18 . The contacts  16  communicate with the converter  12  components  54  through vias (not shown). The processor carrier  18  includes contacts  22  on its upper surface that mate with the contacts  16  when the carrier  18  and converter  12  are edge combined. The contacts  22  eventually electrically connect to power supply pins (not shown) on the processor  52  through connection layer  21 . In one embodiment, the contacts  16  and  22  may each be formed of a copper land pattern. 
     A pair of upstanding alignment pins  24   a  and  24   b  on the processor carrier  18  pass through holes (not shown in FIG. 1) in the converter  12 . This pin/hole connection aligns the contacts  16  and  22  and facilitates the clamping engagement between the converter  12  and the processor carrier  18 . 
     Thus, referring to FIG. 2, the pins  24   a  and  24   b  pass completely through the converter  12  in one embodiment of the present invention. This engagement aligns the contacts  16  and  22  with respect to one another as the converter  12  is pressed down into firm engagement with the processor carrier  18  in the Z-axis direction. 
     Referring to FIG. 4, the converter  12  laps over an edge and electrically engages, in direct surface to surface contact, the processor carrier  18 . The converter  12  and processor carrier  18  may be clamped together using clamping devices  38 . In one embodiment of the present invention, the pins  24  may be threaded and may be secured using threaded fasteners. However, other clamping devices may be utilized to maintain an even clamping force along the length of the contacts  16  and  22 . 
     Referring to FIG. 3, the contacts  16  of the converter  12  include a first set of planar interdigitated contacts  16 a that may provide a power supply (Vcc) connection. A second set of planar interdigitated contacts  16 b may provide the ground (Vss) or return power connection. The interdigitation may be achieved through fingers  40 , in one embodiment of the present invention. The interdigitation of the fingers  40  reduces the inductance of the power contacts  16   a  and the ground contacts  16   b  since mutual inductance is cancelled out by the interdigitated arrangement. 
     Power control signals (such as a PWRG 00 D signal) may also pass through the contacts  16  from the contacts  22 . For example, a plurality of isolated power signal vias  34  may extend through the contacts  16 . Similarly, vias  36  may pass through the process planar power contacts  22 . The arrangement of the signal vias  34  and  36  is subject to considerable variation. 
     Alignment holes  26  are provided on the converter  12  for engagement with the alignment pins  24  on the processor carrier  18 . The arrangement of the contacts  22  may be identical to that shown in FIG. 3 with the exception that the contacts  22  may include vias  36  to an internal copper land pattern (not shown) and may further include the vias  34  which extend through the contacts  16  for conduction of other signals. 
     In this way, the contacts  16  and  22  may be brought into direct, planar surface to surface contact with one another. The contacts  16  and  22  may be brought into direct engagement in the Z-axis direction, with the converter  12  atop the processor carrier  18 . With the application of a compression force across the converter  12  and the processor carrier  18 , good electrical contact may be obtained. The pins  56  on the socket  50  provide electrical communication with the motherboard  28 . 
     Because the converter  12  and the processor carrier  18  may both be assembled in the Z-axis direction, the assembly of the processor power delivery system  10  is facilitated. Of course, it is not necessary that either the converter  12  or the processor carrier  18  be rigorously moved through the Z-axis direction. Instead, either or both of the converter  12  and the processor carrier  18  may be moved so as to have a component of displacement in the Z-axis direction relative to the plane of the motherboard  28 . Since the contacts  16  and  22  meet along a common plane, the converter  12  may be moved onto the processor carrier  18  at any angle between the Z-axis and the plane of the motherboard  28 . 
     The electrical performance may be optimized in some embodiments by modifying the patterning of the contacts  16  and  22  without re-tooling converter  12  or carrier  18  assemblies. Some embodiments may achieve a mechanical benefit from having a single axis of assembly. 
     While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.