US 20020042214 A1
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.
1. A method comprising:
plugging a DC-to-DC converter on top of a processor carrier in turn secured to a motherboard; and
providing substantially planar power and ground contacts on said converter and said processor carrier; and
engaging said contacts on said converter with said contacts on said carrier through a resilient interconnect having resilient electrical contacts.
2. The method of
3. The method of
4. The method of
5. The method of
6. The method of
7. The method of
8. A interconnect comprising:
a non-conductive polymer film; and
a plurality of conductive polymer contacts formed in said film.
9. The interconnect of
10. The interconnect of
11. The interconnect of
12. The interconnect of
13. A motherboard comprising:
a circuit board;
a processor carrier on said board;
a DC-to-DC converter secured on said carrier; and
a film layer sandwiched between said carrier and said converter, said film layer including conductive polymer contacts in said film layer.
14. The motherboard of
15. The motherboard of
 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 axis. 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.
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;
FIG. 4 is a cross-sectional view taken generally along the line 4-4 in FIG. 2;
FIG. 5 is a partial exploded view of the embodiment shown in FIG. 4; and
FIG. 6 is a top plan view of a component shown in FIG. 5.
 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 and clamping housing 58. 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 PWRGOOD 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.
 The processor power delivery system 10 may include a plurality of components that may be resiliently clamped together between the housing 58 and the motherboard 28 as shown in FIG. 5. The housing 58 may include an upper surface with a plurality of reinforcing ribs 62 and a body 60. Formed in the body 60 is a corrugated spring 64. The ends 66 of the spring 64 may be held within the body 60 for example by molding the spring 64 into the body 60.
 When the body 60 is pressed against the converter 12, the spring 64 vees are compressed, applying a uniform force through the body 60 to the converter 12. In one embodiment, the spring 64 may be formed of beryllium copper. It may be shaped in a corrugated shape with a plurality of vees extending into the spring 64 from above and below. Each of the vees may form a V-shaped compression spring pressed against either the body 60 or the converter 12. The arrangement of the corrugated spring 64 serves to make more uniform the forces applied through the body 60.
 Ideally, the housing 58 supplies a substantially constant pressure over the life of the system 10. The spring 64 may be defined with the cold flow properties of the related substrates over time in mind. The housing 58 may be formed of extruded aluminum or plastic as two examples. In one embodiment, the housing 58 may be hinged and latched to clear the contact region and to allow for Z-axis assembly or replacement of components while providing a registration feature to align the underlying substrates.
 Sandwiched between the converter 12 and the processor carrier 18 is a relatively low profile conductive polymer interconnect 68 including a polymer film 70 having captured therein conductive polymer contacts 72. In one embodiment of the present invention, the film 70 may be formed of kapton and the polymer contacts 72 may be formed of a polymer that has been made conductive for example by doping it with conductive particles such as silver particles or oriented metallic wires. In each case, the polymer contacts 72 may be formed of a plastic material that is relatively resilient so that the material may be compressed between the converter 12 and the carrier 18. The polymer contacts 72 produce a conductive contact between the converter 12 and the carrier 18. Moreover, because of the resilient nature of the interconnect 68, surface irregularities may be accounted for and more reliable interconnection may be achieved in some cases.
 In some embodiments, the conductive polymer contacts 72 may be substantially thicker than the film 70. For example, in one embodiment, the contacts 72 may have a thickness four times that of the film 70.
 As shown in FIG. 6, the interconnect 68 includes a pair of openings 74 to receive and pass the alignment pins 24 a and 24 b. The alignment pins 24 a and 24 b also act to precisely position the contacts 72 with respect to the converter 12 and the carrier 18. The pins 24 a and 24 b may extend upwardly through the interconnect 68 and the converter 12 and in one embodiment through the housing 58 for securement by securement devices 38 shown in FIG. 4. In other cases, as mentioned previously, a hinged clamping device may be positioned for selectively applying a clamping force to the converter 12 and carrier 18 through the body 60 and the spring 64.
 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 an embodiment is illustrated in FIGS. 1 through 6 using planar contacts, embodiments of the present invention may be applied to other designs as well. The combination of the spring 64 and the interconnect 68 may be particularly desirable because the pressure applied by the spring 64 may result in more even pressure applied to the conductive contacts 72 in some embodiments.
 In an embodiment using conductive polymer contacts captured in a kapton film, the film may be formed by molding the conductive contacts into a previously formed film, as one example. Another way of forming the interconnect 68 includes shaking conductive contacts into holes in the film and then bonding the contacts in place. Generally, pressure may be applied to the contacts to increase their conductivity.
 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.