Patent Application
20080116589
This relates to computer systems and, more particularly, to providing supply voltages to power integrated circuits such as a processor.
Advances in integrated circuit technology continue to provide faster, more robust, more densely packed integrated circuits. With each technological advance, power delivery, input/output, and thermal solutions become problematic.
A socket may be used to couple a processor to a system board, such as a motherboard. A number of leads connect the various input/output ports on the processor to various buses, control lines, and power lines on the system board. Each lead has associated with it a certain amount of inductance. Inductance, related to the length of leads, must be below a certain critical inductance level in order for input and output operations to work properly. The critical inductance decreases as the operating frequency of the processor increases. The maximum allowable length of the leads tends to decrease as operating frequency increases.
A voltage regulator provides the power delivery solution for the processor. Processors usually operate at different voltage levels and tolerance levels than those typically provided by most power supplies used in computer systems.
Processors also commonly consume power at a higher rate than most power supplies provide. The amount of power that a processor consumes depends on clock speed and transistor density. A voltage regulator may not only convert power to appropriate voltage and tolerance levels, but also supplies power at the required slew rate. Capacitors may store power from the power supply so that it can be provided at a rate faster slew rate. The amount of capacitance needed to sustain the slew rate increases as the slew rate increases and increases as the distance between capacitors and the processor increases. Larger capacitance may mean larger and/or more capacitors must be provided.
Because the voltage regulator needs to be as close as possible to the processor to provide power at the required slew rate and in an efficient manner, it is advantageous to use an integrated voltage regulator that provides power proximate to the processor. For example, in connection with pin grid array circuits, an integrated voltage regulator may be provided within a socket that couples the processor package to a motherboard. The socket provides sufficient vertical height to receive the integrated voltage regulator so that the voltage regulator can be mounted on the bottom of the pin grid array package.
Increasingly, ball grid array packages are becoming more popular. They have many advantages, including lower costs and much smaller package sizes. However, ball grid arrays generally must have solder balls of a certain size to achieve the desired input/output density. As a result, the size of the solder balls tends to be too small to receive an integrated voltage regulator below the processor package.
Referring to
Some of the balls 14 on the integrated circuit 12 may connect via vias 20 through the package 18 to balls 26 on an integrated voltage regulator 28. The integrated voltage regulator 28 may be a bare (unpackaged) die mounted on the bottom of the ball grid array package 18 so that it is in close proximity to the integrated circuit 12. The integrated voltage regulator 28, in some embodiments, may include not only the voltage regulator, but also on-chip decoupling capacitors, a pulse width modulation circuit, and the inductors integrated within one package. An underfill 24 may be provided between the voltage regulator 28 and the ball grid array package 18 to seal the region therebetween.
The balls 22 must be of a certain size in order to obtain the desired density of inputs and outputs between the motherboard 32 and the integrated circuit 12. As a result, in some cases, the solder ball height, for the desired input/output density, may be too small to fit the integrated voltage regulator 28 on the bottom of the package 18 without interfering with the motherboard 32. Again, it is desirable to locate the integrated voltage regulator 28 on the bottom of the package 18 for the electrical performance reasons described previously.
In one embodiment, a recess 30 may be formed in the motherboard 32 to receive the integrated voltage regulator 28 when the package is placed on the motherboard. For example, the package may be surface mounted to the motherboard. It may be positioned by a pick-and-place machine in the appropriate position on the motherboard. In this position, the integrated voltage regulator 28 fits in the recess 30. Then heat may be applied to solder the package to the motherboard 32, thereby fixing the integrated voltage regulator 28 at least partially within the hole 30 in the motherboard 32.
The motherboard recess 30 may be formed by various techniques, including drilling, etching, laser drilling, and punching. The recess 30 may partially or completely penetrate the motherboard 32.
In accordance with another embodiment, in a system 40, also involving a ball grid array integrated circuit package and its securement to a motherboard with an intervening integrated voltage regulator, referring to
As shown in
Formed through the motherboard 32 are a plurality of thermal vias 38. The thermal vias 38 may be formed by drilling vias through the motherboard 38 and then filling the vias with a thermally conductive material, such as a metal, including one or more of copper, gold, or aluminum. As a result, heat is transmitted from the integrated voltage regulator 34 externally of the package and the motherboard. This heat may arise from the operation of the integrated voltage regulator 34, as well as heat transferred from the integrated circuit 12 and otherwise blocked from dissipation by the intervening voltage regulator 34.
In both embodiments described above, conventionally, a heat sink would be provided over the integrated circuit 12 to dissipate heat upwardly away from the package.
Referring to
In accordance with one embodiment, the voltage regulator 150 is an integrated voltage regulator that is external to the processor 100. The voltage regulator 150 may provide one or more supply voltages to the processor 100 alone or in addition to providing one or more supply voltages to other components of the computer system. In addition, there may be one or more additional voltage regulators that provide one or more additional supply voltages to the processor. The voltage regulator may be an integrated voltage regulator, as in the case of the voltage regulators 28 and 34, shown in
Thus, in some embodiments, the voltage regulator may be thicker in a vertical direction than the solder balls joining the package to the board. In one such embodiment, the system board may include a recess to accommodate the regulator. In some embodiments, the recess may extend completely through the system board. In other cases, the recess may not extend all the way through the board. If the recess does not extend completely through the board, a thermal via may be installed under the voltage regulator through the remaining portion of the board, below the recess.
In some embodiments, the regulator may have a thickness in the vertical direction that is less than or equal to the vertical height of the solder balls when coupled between the board and the package. In such cases, a thermal interface material may be used between the board and the regulator. In some cases, the thermal interface may be used to conduct heat through the board from said voltage regulator.
As still another possibility, a donut-shaped interposer may be used to extend the solder balls and to pass the regulator through a central opening in the interposer. The interposer may be positioned between the package 18 and the board 32. It may be coupled by solder balls to the board and the package. The interposer may provide additional vertical space to accommodate the voltage regulator.
References throughout this specification to “one embodiment” or “an embodiment” mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one implementation encompassed within the present invention. Thus, appearances of the phrase “one embodiment” or “in an embodiment” are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be instituted in other suitable forms other than the particular embodiment illustrated and all such forms may be encompassed within the claims of the present application.
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.
