Heat sink configuration for multi-chip module

A multi-chip integrated circuit (IC) apparatus includes a substrate, one or more first IC chips mounted on the substrate, and a second IC chip mounted on the substrate. One or more first heat sinks are respectively thermally coupled to the one or more first IC chips. A second heat sink is thermally coupled to the second IC chip. An under side of the second heat sink is located further from the substrate than each of respective one or more top sides of the one or more first heat sinks.

FIELD OF TECHNOLOGY

The present disclosure relates generally to cooling of semiconductor chips, and more particularly to heat sinks for multi-chip modules.

BACKGROUND

A heat sink is often used to dissipate heat generated by an integrated circuit (IC) device or chip to prevent the operating temperature of the IC chip rising to an extent that causes the IC chip to overheat, which may cause the IC chip to malfunction or fail. Typically, a heat sink comprises a thermally conductive material that transfers heat away from the IC chip to thereby cool the IC chip and/or prevent the IC chip from overheating.

A multi-chip module includes multiple IC chips, each dissipating a potentially different amount of heat and/or having a potentially different maximum operating temperature. Some traditional heat sink systems for multi-chip modules attempt to use a single heat sink that lowers the operating temperature of multiple IC chips to a lowest maximum operating temperature of all of the IC chips. However, a heat sink capable of cooling an IC to a temperature far below the maximum operating temperature of the IC may have a prohibitively large size and/or be expensive.

Another traditional heat dissipation solution for multi-chip modules is using individual heat sinks for individual IC chips. However, the area consumed by multiple heat sinks often limits the number of IC chips that can be included within a multi-chip module of a given size.

SUMMARY

In an embodiment, a multi-chip integrated circuit (IC) apparatus comprises: a substrate; one or more first IC chips mounted on the substrate; a second IC chip mounted on the substrate; one or more first heat sinks respectively thermally coupled to the one or more first IC chips, each first heat sink having i) a respective bottom side, and ii) a respective top side opposite the respective bottom side, the respective top side being located further from the substrate than the respective bottom side; and a second heat sink having i) an under side, and ii) a top side opposite the under side, wherein: the second heat sink is thermally coupled to the second IC chip, the top side of the second heat sink is located further from the substrate than the under side of the second heat sink, and the under side of the second heat sink is located further from the substrate than each of the respective one or more top sides of the one or more first heat sinks.

In another embodiment, a method for assembling an apparatus having a substrate and one or more first IC chips and a second IC chip mounted on the substrate, includes: respectively thermally coupling one or more first heat sinks to the one or more first IC chips, each first heat sink having i) a respective bottom side, and ii) a respective top side opposite the respective bottom side, wherein each first heat sink is positioned so that the respective top side is located further from the substrate than the respective bottom side; and after respectively thermally coupling the one or more first heat sinks to the one or more first IC chips, thermally coupling a second heat sink to the second IC chip, the second heat sink having i) an under side, and ii) a top side opposite the under side, wherein the second heat sink is positioned so that: the top side of the second heat sink is located further from the substrate than the under side of the second heat sink, and the under side of the second heat sink is located further from the substrate than each of the respective one or more top sides of the one or more first heat sinks.

DETAILED DESCRIPTION

In various embodiments described below, multiple heat sinks are positioned in different tiers of heights above a substrate of a multi-chip module and are used to dissipate heat from multiple integrated circuit (IC) chips on the multi-chip module. The different heat sinks are thermally coupled to different IC chips facilitating differentiated cooling of the multiple IC chips, which may dissipate potentially different amounts of heat and/or have different maximum operating temperatures, according to an embodiment. Additionally, because the heat sinks are in different tiers of heights from the substrate of the multi-chip module, an area occupied by the heat sinks is smaller as compared to a system in which all of the heat sinks were at about the same height (or substantially co-planar) from the substrate.

FIG.1is a diagram of an example multi-chip module100, according to an embodiment. As will be described below, the multi-chip module100is used with embodiments of heat sink systems in which multiple heat sinks are positioned in different tiers of heights from a substrate104of the multi-chip module100.

The substrate comprises a suitable material such as a multi-layered laminated printed circuit board (PCB), a ceramic substrate, a silicon substrate, etc. The substrate104includes a top side108and a bottom side112, which is opposite the top side108. In an embodiment, the multi-chip module100is a ball grid array (BGA) and a plurality of solder balls116are mounted to the bottom side112in a grid. In other embodiments, the multi-chip module100uses a suitable packaging technology other than BGA, such as pin grid array (PGA), land grid array, etc. In such embodiments, the solder balls116are not mounted to the bottom side112; rather other suitable electrical connection elements are mounted to the bottom side112(and/or other suitable locations on the substrate104), such as pins, pads, etc.

A plurality of IC chips are mounted to the top side108of the substrate104, including: a first IC chip132, a second IC chip136, a third IC chip140, a fourth IC chip144, and a fifth IC chip148. Although the multi-chip module100is illustrated inFIG.1as having five IC chips, the multi-chip module100includes another suitable number of IC chips (e.g., 2, 3, 4, 6, 7, 8, etc.) in various other embodiments.

FIG.2is a diagram illustrating a cross section of an example system200that uses a multi-tiered heat sink system204with the example multi-chip module100ofFIG.1, according to an embodiment. In the system200, the multi-chip module100is mounted to a PCB208.

The multi-tiered heat sink system204comprises a plurality of first heat sinks in a first height tier220above the substrate104. Heat sinks within a particular height tier can be considered to be substantially co-planar relative to one another. For example, the plurality of first heat sinks in the first height tier220comprises a heat sink228thermally coupled to the first IC chip132, and a heat sink232thermally coupled to the third IC chip140. The plurality of first heat sinks in the first height tier220comprises other heat sinks not shown inFIG.2, including a heat sink thermally coupled to the second IC chip136, and another heat sink thermally coupled to the fourth IC chip144.

The multi-tiered heat sink system204also comprises a second heat sink240in a second height tier244above the substrate104. In an embodiment, the second height tier244is above the first height tier220(i.e., a lowest portion of the second height tier244is further from the substrate104than a highest portion of the first height tier220), and the second heat sink240is distanced further from the substrate104than the heat sinks in the first height tier220. In such a case, any heat sink contained in the second height tier244would not be substantially co-planar with any heat sink contained in the first height tier220.

The second heat sink240is thermally coupled to the fifth IC chip148. In an embodiment, the second heat sink240is thermally coupled to the fifth IC chip148via a heat conducting structure252. In an embodiment, the heat conducting structure252includes one or more heat pipes256. Generally, heat conductivity is improved by increasing the number of heat pipes256within the heat conducting structure252, but the number of heat pipes256that can be included is limited by a cross-sectional area of the heat conducting structure252.

In an embodiment, the heat conducting structure252comprises copper or another material with suitable heat conducting properties. In various embodiments, each of the one or more heat pipes256comprises a sealed pipe or tube made of a suitable material such as copper, aluminum, etc. A suitable fluid is contained within the sealed pipe or tube, such as water, ammonia, etc., according to various embodiments. Generally, the material of the sealed pipe or tube is chosen to be compatible with the fluid contained within the sealed pipe or tube (e.g., copper tube used with water, aluminum tube used with ammonia, etc.). Generally, the fluid contained within the sealed pipe or tube is chosen so that the heat pipe256contains both vapor and liquid over an operating temperature range of the fifth IC chip148, according to an embodiment.

In operation, at a first end of the heat pipe256proximate to the fifth IC chip148, a liquid in contact with a surface of the pipe/tube turns into a vapor by absorbing heat from the surface. The vapor then travels along the heat pipe toward a second end of the heat pipe proximate to the heat sink240and condenses back into a liquid, releasing latent heat. The liquid then returns toward the first end of the heat pipe256through capillary action and/or gravity, and the cycle repeats.

In other embodiments, the heat conducting structure252is omitted, and the heat sink240comprises a column structure that protrudes through the first height tier220and that is thermally coupled to the fifth IC chip148. In some such embodiments, the column structure is integral with the heat sink240and comprises the same material as the heat sink240. In other such embodiments, the column structure is not integral with the heat sink240but is thermally coupled to the heat sink240; and the column structure comprises the same material as the heat sink240, or another suitable material with suitable heat conducting properties.

The heat sink240includes an under side260and a top side264. The top side264is further from the substrate104than the under side260. Each of the heat sinks in the first height tier220includes a respective top side and a respective bottom side, where the respective top side is further from the substrate104than the respective bottom side. For example, the heat sink228includes a top side268and a bottom side270, and the heat sink232includes a top side272and a bottom side274.

In the embodiment illustrated inFIG.2, the under side260of the heat sink240is located at a height further from the substrate104as compared to i) a height of the top side268of the heat sink228and ii) a height of the top side272of the heat sink232. In some embodiments, the under side260of the heat sink240is located at a height further from the substrate104as compared to respective heights of respective top sides of all of the first heat sinks in the first height tier220. In other embodiments, the under side260of the heat sink240is located at a height further from the substrate104as compared to respective heights of one or more respective top sides of one or more first heat sinks in the first height tier220, and closer to the substrate104as compared to respective heights of one or more respective top sides of one or more other first heat sinks in the first height tier220.

In the embodiment illustrated inFIG.2, the entire top side268of the heat sink228is located beneath the under side260of the heat sink240, and the entire top side272of the heat sink232is located beneath the under side260of the heat sink240; in other words, the heat sink240extends entirely over the heat sink228and extends entirely over the heat sink232. In another embodiment, only a portion of the top side268of the heat sink228is located beneath the under side260of the heat sink240, and/or only a portion of the top side272of the heat sink232is located beneath the under side260of the heat sink240; in other words, the heat sink240extends over only a portion of the heat sink228and/or over only a portion of the heat sink232. More generally, in some embodiments, at least respective portions of respective top sides (e.g., the entire top side or only a portion of the top side) of all of the first heat sinks in the first height tier220are located beneath the under side260of the heat sink240; in other words, the heat sink240extends over at least a respective portion of the respective top side of each of the first heat sinks in the first height tier220(e.g., extends over the entire respective top side or only over a portion of the respective top side). In other embodiments, at least respective portions of respective top sides (e.g., the entire top side or only a portion of the top side) of one or more of the first heat sinks in the first height tier220are located beneath the under side260of the heat sink240, and respective top sides of one or more other first heat sinks in the first height tier220are not located beneath any portion of the under side260of the heat sink240; in other words, the heat sink240extends over at least a respective portion of the respective top side of each of one or more of the first heat sinks in the first height tier220, but does not extend over any portion of the respective top side of each of one or more other first heat sinks in the first height tier220.

The heat sink240is thermally insulated from all of, or at least some of, the first heat sinks in the first height tier220, according to some embodiments. For example, the heat conducting structure252is positioned such that the heat conducting structure252is separated from adjacent first heat sinks in the first height tier220by an air gap276, which provides thermal insulation between adjacent first heat sinks in the first height tier220and the heat conducting structure252, according to an embodiment. Similarly, the heat sink240is positioned such that the underside260is separated from top sides of first heat sinks in the first height tier220by respective gaps, which provides thermal insulation between the first heat sinks in the first height tier220and the heat sink240, according to an embodiment. For example, the underside260is separated from the top side268of the heat sink228by an air gap278, and the underside260is separated from the top side272of the heat sink232by an air gap278.

FIG.3Ais a simplified perspective view of a partially assembled system300that includes the multi-chip module100ofFIG.1with three of the first heat sinks in the first height tier220mounted to three of the IC chips on the multi-chip module100, according to an embodiment. For example, the heat sink232is mounted to (and thermally coupled to) the third IC chip140(not shown inFIG.3A), a heat sink304is mounted to (and thermally coupled to) the second IC chip136, and a heat sink308is mounted to (and thermally coupled to) the fourth IC chip144. The heat sink232, the heat sink304, and the heat sink308are depicted inFIG.3Aas being the same size and type merely for simplicity. In various embodiments, however, two or more of the heat sink232, the heat sink304, and the heat sink308may be the same size or different sizes, and may be of the same type or of different types of heat sinks.

FIG.3Bis a simplified perspective view of a more fully assembled system350that includes the multi-chip module100ofFIG.1with all four of the first heat sinks in the first height tier220mounted to four of the IC chips on the multi-chip module100, and the heat sink240mounted to the heat conducting structure252(not shown inFIG.3B), according to an embodiment. For example, the heat sink228is mounted to (and thermally coupled to) the first IC chip132(not shown inFIG.3B), the heat sink304is mounted to (and thermally coupled to) the second IC chip136(not shown inFIG.3B), the heat sink232is mounted to (and thermally coupled to) the third IC chip140(not shown inFIG.3B), the heat sink308is mounted to (and thermally coupled to) the fourth IC chip144(not shown inFIG.3B), and the heat sink240mounted to the heat conducting structure252(not shown inFIG.3B). The heat sinks are depicted inFIG.3Bas being the same size and type merely for simplicity. In various embodiments, however, two or more of the heat sinks may be the same size or different sizes, and may be of the same type or of different types of heat sinks. As merely one illustrative example, the heat sink240may be larger than the two or more first heat sinks in the first height tier220such that larger portions of the top sides of the two or more first heat sinks are underneath the under side of the heat sink240, as discussed above and as illustrated inFIG.2.

Referring again toFIG.2, each of the first heat sinks in the first height tier220is thermally coupled to a respective IC chip with a thermal interface material (TIM)280, according to an embodiment. In an embodiment, the TIM280is the same material for all of the IC chips. In other embodiments, different suitable TIMs are used for different IC chips. During manufacturing, the TIM280is first applied to the IC chip and the first heat sink is then pressed against the TIM280, according to an embodiment. In another embodiment, during manufacturing, the TIM280is first applied to the first heat sink, and the portion of the first heat sink having the TIM280thereon is then pressed against the IC chip. In other embodiments, the first heat sinks in the first height tier220are thermally coupled to respective IC chips in another suitable manner.

The heat conducting structure252is thermally coupled to the fifth IC chip148with a TIM282, according to an embodiment. In an embodiment, the TIM282is the same material as the TIM280. In other embodiments, the TIM282is another suitable material different than the TIM280. During manufacturing, the TIM282is first applied to the fifth IC chip148and the heat conducting structure252is then pressed against the TIM282, according to an embodiment. In another embodiment, during manufacturing, the TIM282is first applied to the heat conducting structure252, and the heat conducting structure252is then pressed against the fifth IC chip148. In other embodiments, the heat conducting structure252is thermally coupled to the fifth IC chip148in another suitable manner. In an embodiment in which the heat conducting structure252is omitted and a heat conducting column is integral with the heat sink240, the heat conducting column is thermally coupled to the fifth IC chip148using the TIM282in a similar manner.

The heat sink is thermally coupled to the heat conducting structure252with a TIM284, according to an embodiment. In an embodiment, the TIM284is the same material as the TIM282. In another embodiment, the TIM284a suitable material different than the TIM282. During manufacturing, the TIM284is first applied to the heat conducting structure252and the heat sink240is then pressed against the heat conducting structure252, according to an embodiment. In another embodiment, during manufacturing, the TIM284is first applied to the heat sink240, and the portion of the heat sink240having the TIM284thereon is then pressed against the heat conducting structure252. In other embodiments, the heat sink is thermally coupled to the heat conducting structure252in another suitable manner.

In an embodiment, the heat sink240is connected to one or more of the first heat sinks in the first height tier220using one or more screws286(or another suitable fastener device). The one or more screws286pass through one or more respective apertures in the heat sink240and are received in one or more respective threaded apertures in one or more respective first heat sinks.

In an embodiment, one or more respective springs (not shown inFIG.2) are included in the air gap(s) between the under side260of the heat sink240and the top side(s) of the one or more first heat sinks, and the one or more screws286are inserted through the respective spring(s). When the screw(s)286are tightened during manufacture the spring(s) are compressed.

In various embodiments, the screws286, springs (not shown), and/or spacers (not shown) are made of suitable material(s) (e.g., plastic or another suitable material) that reduced thermal coupling between the heat sink240and the one or more first heat sinks via the screws286, springs (not shown), and/or spacers (not shown). In various embodiments, the screws286, springs (not shown), and/or spacers (not shown) are coated in a suitable material(s) (e.g., plastic or another suitable material) that reduced thermal coupling between the heat sink240and the one or more first heat sinks via the screws286, springs (not shown), and/or spacers (not shown).

In some embodiments, one or more respective spacers or springs are included in air gap(s) between respective bottom sides of the first heat sinks in the first height tier220and the top side108of the substrate104to provide stability. For example, respective stiffener rings288are mounted on the top side108of the substrate104in a suitable manner (e.g., using epoxy or another suitable fastening material), and respective springs290are inserted in the respective stiffener rings288, according to an embodiment.

In an embodiment, the multi-tiered heat sink system204is attached to the PCB208via a plurality of bolts292and a plurality of nuts294. The bolts292pass through respective apertures in the heat sink240and through respective apertures in the PCB208. In an embodiment, a backing plate296is used between the PCB208and the nuts294to provide additional stability.

In some embodiments, one or more of the bolts292pass through respective apertures in one or more respective first heat sinks in the first height tier220. In some such embodiments, spring(s)298are included in the air gaps between the under side260of the heat sink240and the top side(s) of the one or more first heat sinks, and the bolt(s)292are inserted through the respective spring(s). When the bolts294are tightened during manufacture the spring(s)298are compressed.

In some embodiments in which one or more of the bolts292pass through respective apertures in one or more respective first heat sinks in the first height tier220, one or more respective spacers or springs (not shown inFIG.2) are included in air gap(s) between respective bottom sides of the first heat sinks in the first height tier220and the PCB208to provide stability. When the bolts294are tightened during manufacture the spring(s) (if included) are compressed.

In various embodiments, the bolts292, the springs298, other springs (not shown), and/or spacers (not shown) are made of suitable material(s) (e.g., plastic or another suitable material) that reduced thermal coupling between the heat sink240and the one or more first heat sinks via the bolts292, the springs298, the other springs (not shown), and/or spacers (not shown). In various embodiments, the bolts292, the springs298, other springs (not shown), and/or spacers (not shown) are coated in a suitable material(s) (e.g., plastic or another suitable material) that reduced thermal coupling between the heat sink240and the one or more first heat sinks via the bolts292, the springs298, other springs (not shown), and/or spacers (not shown).

Although the example multi-tiered heat sink system204ofFIG.2includes one heat sink for each IC chip on the multi-chip module100, in other embodiments, one heat sink is provided for multiple IC chips and the multiple IC chips are thermally coupled to the one heat sink. As an illustrative example, one heat sink is provided for two or more of the IC chips132,136,140, and144, and the two or more of the IC chips are thermally coupled to the one heat sink. For instance, IC chips that dissipate similar amounts of heat and/or have similar maximum operating temperatures are coupled to one heat sink in the first height tier220, in an embodiment. Thus, for example, multiple IC chips are thermally coupled to one heat sink in the first height tier220and/or multiple IC chips are thermally coupled to the heat sink240in the second height tier244, in various embodiments. In some embodiments in which multiple IC chips are thermally coupled to the heat sink240in the second height tier244, each IC chip is thermally coupled to the heat sink240via respective heat conducting structures (and/or heat conducting columns) similar to the heat conducting structure252(or heat conducting column) discussed above. In other embodiments in which multiple IC chips are thermally coupled to the heat sink240in the second height tier244, the multiple IC chips are thermally coupled to the heat sink240via one heat conducting structure (or heat conducting column) similar to the heat conducting structure252(or heat conducting column) discussed above.

Although the example multi-tiered heat sink system204ofFIG.2includes one heat sink240in the second height tier244, in other embodiments, the second height tier244includes multiple heat sinks (e.g., substantially co-planar heat sinks) thermally coupled to multiple IC chips via respective heat conducting structures (and/or heat conducting columns) similar to the heat conducting structure252(or heat conducting column) discussed above.

In the example multi-tiered heat sink system204ofFIG.2, one heat sink204is positioned above multiple first heat sinks in the first height tier220, at least according to some embodiments. In other embodiments, multiple heat sinks are positioned above one or more other heat sinks.

FIG.4is a diagram illustrating a cross section of another example system400that uses a multi-tiered heat sink system404with the example multi-chip module100ofFIG.1, according to an embodiment. In the system400, the multi-chip module400is mounted to a PCB408.

The multi-tiered heat sink system404comprises a first heat sink416in a first height tier420above the substrate104. The first heat sink416is thermally coupled to the fifth IC chip148the same as or similar to the thermal coupling between the heat sink228and the IC chip132described with reference toFIG.2, according to some embodiments.

The multi-tiered heat sink system404also comprises a plurality of second heat sinks in a second height tier424above the substrate104. In an embodiment, the second height tier424is above the first height tier420(i.e., a lowest portion of the second height tier424is further from the substrate104than a highest portion of the first height tier420), and the second heat sink416is distanced closer to the substrate104than the heat sinks in the second height tier424.

For example, the plurality of second heat sinks in the second height tier424comprises a heat sink432thermally coupled to the first IC chip132, and a heat sink436thermally coupled to the third IC chip140. The plurality of second heat sinks in the second height tier424comprises other heat sinks not shown inFIG.4, including a heat sink thermally coupled to the second IC chip136, and another heat sink thermally coupled to the fourth IC chip144, according to an embodiment.

In an embodiment, the heat sink432is thermally coupled to the first IC chip132via a heat conducting structure440, and the heat sink436is thermally coupled to the third IC chip140via a heat conducting structure444. In an embodiment, each of the heat conducting structure440and the heat conducting structure444has a same or similar structure as the heat conducting structure252as describe above with reference toFIG.2. In some embodiments, the heat conducting structure440and the heat conducting structure444have a same structure (e.g., a same number of heat pipes, a same material, etc.), whereas in other embodiments the heat conducting structure440and the heat conducting structure444have different structures (e.g., different numbers of heat pipes, and/or different materials, etc.).

In an embodiment, the first heat sink416includes a plurality of apertures shaped to allow heat conducting structures to pass through to IC chips on the multi-chip module100. For example, the first heat sink416includes a first aperture that allows the heat conducting structure440to pass through to the first IC chip132and a second aperture that allows the heat conducting structure444to pass through to the third IC chip140, according to an embodiment.

In other embodiments, the heat conducting structure440is omitted, and the heat sink432includes a heat conducting column structure that is integral with the heat sink432and which thermally couples the heat sink432to the first IC chip132; and/or the heat conducting structure444is omitted, and the heat sink436includes a heat conducting column structure that is integral with the heat sink436and which thermally couples the heat sink432to the third IC chip140. In some such embodiments, the heat conducting column structure(s) of the heat sink432and/or the heat sink436pass through aperture(s) in the first heat sink416to thermally couple with IC chip(s) on the multi-chip module100.

Each of the heat sinks in the second height tier424includes a respective top side and a respective under side, where the respective top side is further from the substrate104than the respective under side. For example, the heat sink432includes an under side460and a top side464. The top side464is further from the substrate104than the under side460. Also, the heat sink436includes an under side468and a top side472. The top side472is further from the substrate104than the under side468.

The heat sink416includes a bottom side476and a top side480. The top side480is further from the substrate104than the bottom side476.

In the embodiment illustrated inFIG.4, the under side460of the heat sink432is located at a height further from the substrate104as compared to a height of the top side480of the heat sink416. Additionally, the under side468of the heat sink436is located at a height further from the substrate104as compared to the height of the top side480of the heat sink416.

In some embodiments, the height of the top side480of the heat sink416is below the respective height of the respective under side of each heat sink in the second height tier424. In other embodiments, the height of the top side480of the heat sink416is above one or more respective heights of one or more respective under sides of one or more heat sinks in the second height tier424. In such a case, any heat sink contained in the second height tier424would not be substantially co-planar with any heat sink contained in the first height tier420.

In the embodiment illustrated inFIG.4, a first portion of the top side480of the heat sink416is located below at least a portion of the under side460of the heat sink432, and a second portion of the top side480of the heat sink416is located below at least a portion of the under side468of the heat sink436; in other words, at least a portion of the heat sink432extends over the heat sink416, and at least a portion of the heat sink436extends over the heat sink416. In an embodiment, the first portion of the top side480of the heat sink416is located below the entire under side460of the heat sink432, and/or the second portion of the top side480of the heat sink416is located below the entire under side468of the heat sink436; in other words, the heat sink432extends over the heat sink416, and the heat sink436extends over the heat sink416.

The heat sink416is thermally insulated from all of, or at least some of, the heat sinks in the second height tier424, according to some embodiments. For example, the heat conducting structure440is positioned such that the heat conducting structure440is separated from sides of the first aperture of the heat sink416by an air gap, which provides thermal insulation between the heat sink416and the heat conducting structure440, according to an embodiment. Similarly, the heat conducting structure444is positioned such that the heat conducting structure444is separated from sides of the second aperture of the heat sink416by an air gap, which provides thermal insulation between the heat sink416and the heat conducting structure444, according to an embodiment.

Also, the heat sink432is positioned such that the underside460is separated from the top side480of the heat sink416, which provides thermal insulation between the heat sink416and the heat sink432, according to an embodiment. Similarly, the heat sink436is positioned such that the underside468is separated from the top side480of the heat sink416, which provides thermal insulation between the heat sink416and the heat sink436, according to an embodiment.

The heat sink416is thermally coupled to the fifth IC chip148by a TIM in the same or similar manner as the heat sink228(FIG.2) is thermally coupled to the first IC chip132as discussed above with reference toFIG.2. The heat conducting structure440is thermally coupled to the first IC chip132by a TIM in the same or similar manner as the heat conducting structure252(FIG.2) is thermally coupled to the fifth IC chip148as discussed above with reference toFIG.2. The heat conducting structure444is thermally coupled to the third IC chip140by a TIM in the same or similar manner as the heat conducting structure252(FIG.2) is thermally coupled to the fifth IC chip148as discussed above with reference toFIG.2. The heat conducting structure440is thermally coupled to the heat sink432by a TIM in the same or similar manner as the heat conducting structure252(FIG.2) is thermally coupled to the heat sink240as discussed above with reference toFIG.2. The heat conducting structure444is thermally coupled to the heat sink436by a TIM in the same or similar manner as the heat conducting structure252(FIG.2) is thermally coupled to the heat sink240as discussed above with reference toFIG.2.

In some embodiments, the heat sink432is connected to the heat sink416using one or more screws (or another suitable fastener device) in the same or similar manner as the heat sink240(FIG.2) is connected to one or more of the first heat sinks in the first height tier220(FIG.2) using the one or more screws286(or another suitable fastener device), as discussed above with reference toFIG.2. Similarly, in some embodiments, the heat sink436is connected to the heat sink416using one or more screws (or another suitable fastener device) in the same or similar manner as the heat sink240(FIG.2) is connected to one or more of the first heat sinks in the first height tier220(FIG.2) using the one or more screws286(or another suitable fastener device), as discussed above with reference toFIG.2.

In some embodiments, the multi-tiered heat sink system404is attached to the PCB408via a plurality of bolts and a plurality of nuts in the same or similar manner as the multi-tiered heat sink system204(FIG.2) is attached to the PCB208(FIG.2) via the plurality of bolts292and the plurality of nuts294, as discussed above with reference toFIG.2.

Springs and/or spacers are used to increase stability in the same or similar manner as screws, springs, and/or spacers were used to increase stability in the system200(FIG.2), as discussed above with reference toFIG.2.

Although the example multi-tiered heat sink system404ofFIG.4includes one heat sink for each IC chip on the multi-chip module100, in other embodiments, one heat sink is provided for multiple IC chips and the multiple IC chips are thermally coupled to the one heat sink. As an illustrative example, one heat sink is provided for two or more of the IC chips132,136,140, and144, and the two or more of the IC chips are thermally coupled to the one heat sink. For instance, IC chips that dissipate similar amounts of heat and/or have similar maximum operating temperatures are coupled to one heat sink in the second height tier424, in an embodiment. Thus, for example, multiple IC chips are thermally coupled to the heat sink416in the first height tier420and/or multiple IC chips are thermally coupled to one heat sink in the second height tier424, in various embodiments.

In some embodiments in which multiple IC chips are thermally coupled to one heat sink in the second height tier424, each IC chip is thermally coupled to the one heat sink via respective heat conducting structures (and/or heat conducting columns) similar to the heat conducting structures432,444(or heat conducting column)s discussed above. In other embodiments in which multiple IC chips are thermally coupled to one heat sink in the second height tier424, the multiple IC chips are thermally coupled to the one heat sink via one heat conducting structure (or heat conducting column) similar to the heat conducting structure252(or heat conducting column) discussed above.

Although the example multi-tiered heat sink system404ofFIG.4includes one heat sink416in the first height tier420, in other embodiments, the first height tier420includes multiple heat sinks (e.g., substantially co-planar heat sinks) thermally coupled to one IC chip (or multiple IC chips) using techniques such as discussed above.

In the example multi-tiered heat sink system204ofFIG.2and the example multi-tiered heat sink system404ofFIG.4, heat sinks are arranged in two height tiers. In other embodiments, heat sinks are arranged in more than two height tiers.

FIG.5is a diagram of another example multi-chip module500, according to an embodiment. The multi-chip module500is similar to the multi-chip module100ofFIG.1, and like-numbered elements are not described again in detail for purposes of brevity. As will be described below, the multi-chip module500is used with embodiments of heat sink systems in which multiple heat sinks are positioned in different tiers of heights from the substrate104of the multi-chip module500.

A sixth IC chip504is also mounted to the substrate104. Although the multi-chip module500is illustrated inFIG.5as having six IC chips, the multi-chip module100includes another suitable number of IC chips (e.g., 3, 4, 5, 7, 8, etc.) in various other embodiments.

FIG.6is a diagram illustrating a cross section of another example system600that uses a multi-tiered heat sink system604with the example multi-chip module500ofFIG.5, according to an embodiment. The system600is similar to the system400ofFIG.4, and like-numbered elements are not described again in detail for purposes of brevity.

In the system600, the multi-chip module600is mounted to a PCB608.

The multi-tiered heat sink system604includes a third heat sink612in a third height tier616above the substrate104. In an embodiment, the third height tier616is above the second height tier424(i.e., a lowest portion of the third height tier616is further from the substrate104than a highest portion of the second height tier424), and the third heat sink612is distanced further from the substrate104than the heat sinks in the second height tier424. In such a case, any heat sink contained in the third height tier616would not be substantially co-planar with any heat sink contained in the first height tier420, and would not be substantially co-planar with any heat sink contained in the second height tier424.

The third heat sink612is thermally coupled to the sixth IC chip504via a heat conducting structure620, and the heat sink436is thermally coupled to the third IC chip140via the heat conducting structure440. In an embodiment, the heat conducting structure620has a same or similar structure as the heat conducting structure252as describe above with reference toFIG.2.

In other embodiments, the heat conducting structure620is omitted, and the heat sink612includes a heat conducting column structure that is integral with the heat sink612and which thermally couples the heat sink612to the sixth IC chip504. In some such embodiments, the heat conducting column structure of the heat sink612passes through the aperture in the first heat sink416to thermally couple with the sixth IC chip on the multi-chip module500.

In an embodiment, the first heat sink416includes an aperture shaped to allow the heat conducting structure620(or the heat conducting column structure integral with the heat sink612) to pass through to the sixth IC chip504. In an embodiment, the heat sink436also includes an aperture shaped to allow the heat conducting structure620(or the heat conducting column structure integral with the heat sink612) to pass through to the sixth IC chip504. In another embodiment, the heat conducting structure620(or the heat conducting column structure integral with the heat sink612) is laterally spaced from a side of the heat sink436and does not pass through an aperture in the heat sink436.

The heat sink612includes a top side632and an under side636, where the top side632is further from the substrate104than the under side636.

In the embodiment illustrated inFIG.6, the under side636of the heat sink612is located at a height further from the substrate104as compared to i) the height of the top side464of the heat sink432, and ii) the height of the top side472of the heat sink436.

In some embodiments, the under side636of the heat sink612is located at a height further from the substrate104as compared to respective heights of respective top sides of all of the heat sinks in the second height tier424. In other embodiments, the under side636of the heat sink612is located at a height further from the substrate104as compared to respective heights of one or more respective top sides of one or more heat sinks in the second height tier424, and closer to the substrate104as compared to respective heights of one or more respective top sides of one or more other heat sinks in the second height tier424.

In the embodiment illustrated inFIG.6, the entire top side464of the heat sink432is located beneath the under side636of the heat sink612, and the entire top side472of the heat sink436is located beneath the under side636of the heat sink612; in other words, the heat sink612extends entirely over the heat sink432and extends entirely over the heat sink436. In another embodiment, only a portion of the top side464of the heat sink432is located beneath the under side636of the heat sink612, and/or only a portion of the top side472of the heat sink436is located beneath the under side636of the heat sink612; in other words, the heat sink612extends over only a portion of the heat sink432and/or over only a portion of the heat sink436.

The heat sink612is thermally insulated from the heat sink416in the first height tier420, and from all of, or at least some of, the heat sinks in the second height tier424, according to some embodiments. For example, the heat conducting structure620is positioned such that the heat conducting structure620is separated from sides of the aperture in the heat sink416by an air gap, which provides thermal insulation between the heat sink416and the heat conducting structure620, according to an embodiment. Additionally, the heat conducting structure620is positioned such that the heat conducting structure620is separated from sides of the aperture in the heat sink436by an air gap, which provides thermal insulation between the heat sink436and the heat conducting structure620, according to an embodiment.

Similarly, the heat sink612is positioned such that the underside636is separated from top sides of heat sinks in the second height tier424by respective gaps, which provides thermal insulation between the heat sinks in the second height tier424and the heat sink612, according to an embodiment.

The heat conducting structure620is thermally coupled to the sixth IC chip504by a TIM in the same or similar manner as the heat conducting structure252(FIG.2) is thermally coupled to the fifth IC chip148as discussed above with reference toFIG.2. The heat conducting structure620is thermally coupled to the heat sink612by a TIM in the same or similar manner as the heat conducting structure252(FIG.2) is thermally coupled to the heat sink240as discussed above with reference toFIG.2.

In some embodiments, the heat sink612is connected to the heat sink432and/or the heat sink436using one or more screws (or another suitable fastener device, not shown) in the same or similar manner as the heat sink240(FIG.2) is connected to one or more of the first heat sinks in the first height tier220(FIG.2) using the one or more screws286(or another suitable fastener device), as discussed above with reference toFIG.2.

In some embodiments, the multi-tiered heat sink system604is attached to the PCB608via a plurality of bolts and a plurality of nuts in the same or similar manner as the multi-tiered heat sink system204(FIG.2) is attached to the PCB208(FIG.2) via the plurality of bolts292and the plurality of nuts294, as discussed above with reference toFIG.2.

Springs and/or spacers are used to increase stability in the same or similar manner as screws, springs, and/or spacers were used to increase stability in the system200(FIG.2), as discussed above with reference toFIG.2.

In the example multi-tiered heat sink systems described above, heat conducting structures (e.g., the heat conducting structure252ofFIG.2, the heat conducting structures440and444ofFIG.4, and the heat conducting structure620ofFIG.6) are used to thermally couple IC chips with heat sinks located in higher height tiers of the multi-tiered heat sink systems. In other embodiments, similar heat conducting structures are used to fit more heat sinks within a single height tier.

Although the example multi-tiered heat sink system604ofFIG.6includes one heat sink for each IC chip on the multi-chip module500, in other embodiments, one heat sink is provided for multiple IC chips and the multiple IC chips are thermally coupled to the one heat sink. As an illustrative example, one heat sink is provided for two or more of the IC chips132,136,140, and144, and the two or more of the IC chips are thermally coupled to the one heat sink. For instance, IC chips that dissipate similar amounts of heat and/or have similar maximum operating temperatures are coupled to one heat sink in the second height tier424, in an embodiment. Thus, for example, multiple IC chips are thermally coupled to the heat sink416in the first height tier420, multiple IC chips are thermally coupled to one heat sink in the second height tier424, and/or multiple IC chips are thermally coupled to the heat sink612in the third height tier616, in various embodiments. In some embodiments in which multiple IC chips are thermally coupled to one heat sink in the second height tier424, the multiple IC chips are thermally coupled to the one heat sink via one heat conducting structure (or heat conducting column) similar to the heat conducting structure252(or heat conducting column) discussed above. In other embodiments in which multiple IC chips are thermally coupled to one heat sink in the third height tier616, the multiple IC chips are thermally coupled to the one heat sink via one heat conducting structure (or heat conducting column) similar to the heat conducting structure252(or heat conducting column) discussed above.

Although the example multi-tiered heat sink system404ofFIG.4includes one heat sink416in the first height tier420, in other embodiments, the first height tier420includes multiple heat sinks (e.g., substantially co-planar heat sinks) thermally coupled to one IC chip (or multiple IC chips) using techniques such as discussed above.

Although the example multi-tiered heat sink system404ofFIG.4includes one heat sink612in the third height tier616, in other embodiments, the third height tier616includes multiple heat sinks (e.g., substantially co-planar heat sinks) thermally coupled to one IC chip (or multiple IC chips) using one or more heat conducting structures (and/or one or more heat conducting columns) similar to the heat conducting structure620(or heat conducting column) discussed above.

FIG.7is a diagram of the example multi-chip module500ofFIG.5with which a heat conducting structure704is used to thermally couple a heat sink within a first height tier closest to the substrate104, according to an embodiment. The heat conducting structure704is thermally coupled to the sixth IC chip504, e.g., using a TIM or another suitable material.

In an embodiment, the heat conducting structure704has a same or similar structure as the heat conducting structure252as describe above with reference toFIG.2. The heat conducting structure704includes a top side708to which a heat sink (not shown) can be thermally coupled, e.g., using a TIM or another suitable material. Use of the heat conducting structure704permits the heat sink to be spaced laterally away from the sixth IC chip504, which may permit more heat sinks to be included in the first height tier closest to the substrate104, according to an embodiment.

FIGS.2,3A,3B,4, and6depict extruded aluminum or copper heat sinks. In other embodiments, however, other suitable heat sinks are utilized, such as pin fin heat sinks, straight fin heat sinks, parallel stacked fins heat sinks, etc. In some embodiments, the same type of heat sink is used for all heat sinks in a multi-tiered heat sink system such as described above. In other embodiments, different types of heat sinks are used in a single multi-tiered heat sink system such as described above. In some embodiments, all heat sinks in one height tier are of the same first type, whereas one or more heat sinks in another height tier are of a different second type, in multi-tiered heat sink systems such as described above. In some embodiments, heat sinks in one height tier are of different types in multi-tiered heat sink systems such as described above. In some embodiments, a single heat sink comprises multiple materials in multi-tiered heat sink systems such as described above. As an illustrative example, a heat sink with fins comprises an aluminum base and copper fins, or vice versa.

FIG.8is a flow diagram of an example method800for assembling an apparatus that includes i) a substrate, ii) one or more first IC chips and a second IC chip mounted on the substrate, and iii) a plurality of heat sinks, according to an embodiment. The method800is used in conjunction with a multi-chip module such as the multi-chip module100ofFIG.1, the multi-chip module500ofFIG.5, or another suitable multi-chip module. The method800is also used in conjunction with a multi-tiered heat sink system such as the multi-tiered heat sink system204ofFIG.2, the multi-tiered heat sink system404ofFIG.4, the multi-tiered heat sink system604ofFIG.6, or another suitable multi-tiered heat sink system.

At block804, respectively thermally coupling one or more first heat sinks to the one or more first IC chips, each first heat sink having i) a respective bottom side, and ii) a respective top side opposite the respective bottom side, wherein each first heat sink is positioned so that the respective top side is located further from the substrate than the respective bottom side;

At block808, thermally coupling a second heat sink to the second IC chip, the second heat sink having i) an under side, and ii) a top side opposite the under side, wherein the second heat sink is positioned so that: the top side of the second heat sink is located further from the substrate than the under side of the second heat sink, and the under side of the second heat sink is located further from the substrate than each of the respective one or more top sides of the one or more first heat sinks. In an embodiment, block808is performed after block804is performed.

In an embodiment, thermally coupling the second heat sink to the second IC chip at block808comprises thermally coupling the second heat sink to the second IC chip via a heat conducting structure. In an embodiment, a particular first heat sink includes an aperture; and the heat conducting structure is positioned to pass through the aperture.

In another embodiment, the second heat sink includes a heat conducting column structure that is integral with the second heat sink; and thermally coupling the second heat sink to the second IC chip comprises thermally coupling the heat conducting column structure to the second IC chip. In an embodiment, a particular first heat sink includes an aperture; and the heat conducting column structure is positioned to pass through the aperture.

In an embodiment, the method800further comprises attaching the second heat sink to the one or more first heat sinks.

In another embodiment, the method800further comprises mounting the substrate to a PCB; and compressing the one or more first heat sinks and the second heat sink toward the PCB.

In another embodiment, a third IC chip is mounted on the substrate; and the method800further comprises: after thermally coupling the second heat sink to the second IC chip, thermally coupling a third heat sink to the third IC chip, the third heat sink having i) an under side, and ii) a top side opposite the under side, wherein the third heat sink is positioned so that: the top side of the third heat sink is located further from the substrate than the under side of the third heat sink, and the under side of the third heat sink is located further from the substrate than the top side of the second heat sink.

In another embodiment, thermally coupling the third heat sink to the third IC chip comprises thermally coupling the third heat sink to the third IC chip via a heat conducting structure.

Embodiment 1: A multi-chip integrated circuit (IC) apparatus, comprising: a substrate; one or more first IC chips mounted on the substrate; a second IC chip mounted on the substrate; one or more first heat sinks respectively thermally coupled to the one or more first IC chips, each first heat sink having i) a respective bottom side, and ii) a respective top side opposite the respective bottom side, the respective top side being located further from the substrate than the respective bottom side; and a second heat sink having i) an under side, and ii) a top side opposite the under side, wherein: the second heat sink is thermally coupled to the second IC chip, the top side of the second heat sink is located further from the substrate than the under side of the second heat sink, and the under side of the second heat sink is located further from the substrate than each of the respective one or more top sides of the one or more first heat sinks.

Embodiment 2: The multi-chip IC apparatus of embodiment 1, wherein the second heat sink is thermally insulated from each of the one or more first heat sinks by one or more respective air gaps.

Embodiment 3: The multi-chip IC apparatus of either of embodiments 1 and 2, further comprising: a heat conducting structure thermally coupled to the second IC chip and thermally coupled to the second heat sink.

Embodiment 4: The multi-chip IC apparatus of embodiment 3, wherein the heat conducting structure comprises a plurality of heat pipes.

Embodiment 5: The multi-chip IC apparatus of either of embodiments 3 and 4, wherein: a particular first heat sink includes an aperture; and the heat conducting structure passes through the aperture.

Embodiment 6: The multi-chip IC apparatus of one of embodiments 3 and 4, wherein: the one or more first heat sinks include multiple first heat sinks; and the heat conducting structure is laterally spaced from the multiple first heat sinks.

Embodiment 7: The multi-chip IC apparatus of either of embodiments 1 and 2, wherein: the second heat sink includes a heat conducting column structure that is integral with the second heat sink; and the heat conducting column structure is thermally coupled to the second IC chip.

Embodiment 8: The multi-chip IC apparatus of any of embodiments 1-7, further comprising: a third IC chip mounted on the substrate; and a third heat sink having i) an under side, and ii) a top side opposite the under side, wherein: the third heat sink is thermally coupled to the third IC chip, the top side of the third heat sink is located further from the substrate than the under side of the third heat sink, and the under side of the third heat sink is located further from the substrate than the top side of the second heat sink.

Embodiment 9: The multi-chip IC apparatus of embodiment 8, further comprising: a heat conducting structure thermally coupled to the third IC chip and thermally coupled to the third heat sink.

Embodiment 10: The multi-chip IC apparatus of embodiment 9, wherein: the second heat sink includes an aperture; and the heat conducting structure passes through the aperture.

Embodiment 11: The multi-chip IC apparatus of embodiment 10, wherein: the aperture is a first aperture; a particular first heat sink includes a second aperture; and the heat conducting structure passes through the second aperture.

Embodiment 12: A method for assembling an apparatus that includes a substrate, and one or more first integrated circuit (IC) chips and a second IC chip mounted on the substrate, the method comprising: respectively thermally coupling one or more first heat sinks to the one or more first IC chips, each first heat sink having i) a respective bottom side, and ii) a respective top side opposite the respective bottom side, wherein each first heat sink is positioned so that the respective top side is located further from the substrate than the respective bottom side; and after respectively thermally coupling the one or more first heat sinks to the one or more first IC chips, thermally coupling a second heat sink to the second IC chip, the second heat sink having i) an under side, and ii) a top side opposite the under side, wherein the second heat sink is positioned so that: the top side of the second heat sink is located further from the substrate than the under side of the second heat sink, and the under side of the second heat sink is located further from the substrate than each of the respective one or more top sides of the one or more first heat sinks.

Embodiment 13: The method of embodiment 12, wherein thermally coupling the second heat sink to the second IC chip comprises thermally coupling the second heat sink to the second IC chip via a heat conducting structure.

Embodiment 14: The method of embodiment 13, wherein: a particular first heat sink includes an aperture; and the heat conducting structure is positioned to pass through the aperture.

Embodiment 15: The method of embodiment 12, wherein: the second heat sink includes a heat conducting column structure that is integral with the second heat sink; and thermally coupling the second heat sink to the second IC chip comprises thermally coupling the heat conducting column structure to the second IC chip.

Embodiment 16: The method of embodiment 15, wherein: a particular first heat sink includes an aperture; and the heat conducting column structure is positioned to pass through the aperture.

Embodiment 17: The method of any of embodiments 12-16, further comprising: attaching the second heat sink to the one or more first heat sinks.

Embodiment 18: The method of any of embodiments 12-17, further comprising: mounting the substrate to a printed circuit board (PCB); and compressing the one or more first heat sinks and the second heat sink toward the PCB.

Embodiment 19: The method of any of embodiments 12-18, wherein: a third IC chip is mounted on the substrate; and the method further comprises: after thermally coupling the second heat sink to the second IC chip, thermally coupling a third heat sink to the third IC chip, the third heat sink having i) an under side, and ii) a top side opposite the under side, wherein the third heat sink is positioned so that: the top side of the third heat sink is located further from the substrate than the under side of the third heat sink, and the under side of the third heat sink is located further from the substrate than the top side of the second heat sink.

Embodiment 20: The method of embodiment 19, wherein thermally coupling the third heat sink to the third IC chip comprises thermally coupling the third heat sink to the third IC chip via a heat conducting structure.