Cooling system for high power application specific integrated circuit with embedded high bandwidth memory

The subject disclosure relates to an integrated circuit package having an application specific integrated circuit, a high bandwidth memory, a first heat sink having a first footprint and a first path, and a second heat sink having a second footprint and a second path, wherein the second footprint does not exceed the first footprint. The thermal energy through the first path travels from the application specific integrated circuit to the first heat sink and thermal energy through the second path travel from the high bandwidth memory through one or more heat pipes to the second heat sink.

FIELD OF TECHNOLOGY

The subject technology relates to cooling systems for application specific integrated circuits, and specifically, cooling systems for a high bandwidth memory embedded in an application specific integrated circuit.

BACKGROUND

An application-specific integrated circuit (ASIC) is an integrated circuit (IC) customized for a particular use, rather than intended for general-purpose use. High Bandwidth Memory (HBM) is a high-performance RAM interface for 3D-stacked DRAM that can be embedded within an ASIC. Generally, heat generated at the ASIC and the HBM have to utilize the same conduction path through the package lid to the primary heat sink. The power dissipation at the HBM is lower compared to that of the ASIC, however, due to smaller form factor, of the HBM, the resulting heat flux can be higher compared to that of the ASIC die (e.g., the HBM can have hot spots). Also, the allowable junction temperature for the HBM and the ASIC can significantly differ. As such, the HBM usually has a max temperature limit which can be 20-25 degrees C. less than that of the ASIC die. Accordingly, the HBM requires more aggressive cooling requirements.

DETAILED DESCRIPTION

The advancement of ASICs has translated to increased input/output ports on line cards. With the increased input/output ports, the front-to-back air intake capacity is limited (e.g., lower airflow/higher upstream power dissipation). The limited air intake capacity, results in the downstream packages (e.g., ASIC, HBM, heat sinks, etc.) experiencing preheated airflow and lower cooling capacities. To address the cooling requirements of an ASIC with embedded HBM, a cooling system including an integrated micro heat pipe/vapor chamber and a miniature heat sink can be added to the package. The micro heat pipe/vapor chamber and a miniature heat sink can be added, without increasing the footprint of the assembly (e.g., package and primary heat sink) and can create an additional heat transmit path for cooling the HBM. The additional heat transmit path can be in the lateral direction to the HBM. The micro heat pipe/vapor chamber can be in contact with the HBM inside the package. The transmitted heat from the HBM can then be eventually dissipated in the form of forced convection via the secondary miniature heat sink placed underneath the primary heat sink (and attached to the side of the ASIC). Accordingly, the cooling system can provide a secondary cooling path for the HBM, which has a lower allowable junction temperature.

Disclosed is a cooling system including at least an application specific integrated circuit, a high bandwidth memory, and a first and second heat sink. The first heat sink and the second heat sink are not in direct physical contact. Thermal energy from the application specific integrated circuit can be directed through the first heat sink and thermal energy from the high bandwidth memory can at least partially be diverted from the first heat sink to the second heat sink. Also disclosed are one or more heat pipes, wherein the one or more heat pipes at least partially diverts the thermal energy from the high bandwidth memory to the second heat sink and the one or more heat pipes at least partially overlaps the high bandwidth memory. In some examples, at least one of the heat pipes is a vapor chamber.

In some examples, the application specific integrated circuit is adjacent the high bandwidth memory and the second heat sink is adjacent the high bandwidth memory. A vapor chamber/heat pipe passes through the side wall of the ASIC lid, the cold end of the vapor chamber/heat pipe is attached to the second heat sink and the hot end is the attached to the HBM. In some examples, a footprint of the first heat sink is equal to combined footprints of the application specific integrated circuit, the high bandwidth memory, and the second heat sink.

FIG. 1illustrates a top view of an example ASIC with embedded HBM. Package100can at least include ASIC102and HBM104. In some examples, HBM104can be adjacent ASIC102. WhileFIG. 1illustrates the ASIC and HBM adjacent one another, it should be appreciated that other orientations of the ASIC and HBM are possible.FIG. 2illustrates a front view of an example ASIC with embedded HBM. Cooling System200can include ASIC102and HBM104set on substrate112, and primary heat sink108. Heat sink108can include fins108A and base108B. Thermal interface material (TIM)110can be in between base108A and package100(e.g., attach heat sink108to package100). TIM110can enhance the thermal coupling between heat sink108and package100. In some examples, TIM can be thermal grease, thermal glue, thermal gap filler, thermal pad, thermal adhesive, etc. Heat generated from ASIC102and HBM104can be passively transferred, through TIM110, to primary heat sink108, as shown by arrows106A and106B. Primary heat sink108can transfer the thermal energy from a higher temperature device (e.g., ASIC102, HBM104) to a lower temperature fluid medium (e.g., air, etc.).

FIG. 3illustrates a perspective view of an example ASIC with embedded HBM and heat pipe. Cooling system300can include ASIC102, HBM104, heat pipe118(e.g., integrated micro heat pipe) and secondary heat sink114(e.g., miniature heat sink). Heat pipe118can provide path120(e.g., lateral path) for the transfer of heat (e.g., thermal energy) to secondary heat sink114from HBM104(e.g., transmitted heat is dissipated in the form of convection via secondary heat sink). The lateral transfer of heat from package300can also reduce the load (of thermal energy) on primary heat sink108(from ASIC102).

In some examples, heat pipe118can be a micro vapor chamber. Heat pipe118can transfer heat from HBM104to secondary heat sink114by thermal conduction and phase change. At hot end122of heat pipe118, a liquid inside heat pipe118(e.g., a thermally conductive solid surface) can turn into a vapor by absorbing heat from HBM104. The vapor then travels along heat pipe118(e.g., via path120) to secondary heat sink114(e.g., cold interface) and condenses back into a liquid and releases the latent heat. The liquid can then returns to hot end122through capillary action and the cycle can repeat. In some examples, there can be more than one heat pipe between HBM104and secondary heat sink114. Utilizing more than one heat pipe can spread the heat among the multiple heat pipes enhancing cooling capabilities. In some examples, the one or more heat pipes can be attached to the same vapor chamber base (e.g., hot end122of heat pipe118). Arrows116can illustrate the flow of cool air through secondary heat sink114. While not shown inFIG. 3, the flow of air through primary heat sink108in in the same direction as arrows116.

The hot end122of heat pipe118can be shown in detail atFIG. 4. As shown inFIG. 4, hot end122can overlap at least a portion of HBM104. In some examples, hot end122can extend to substantially the entire length of HBM104. In other examples, the hot end112can extend the entire length of HBM104. In other examples, hot end122can extend across HBM104at differing lengths. The extent of overlapping portions between hot end122and HBM104can provide differing cooling characteristics (e.g., the larger amount of overlap, the greater cooling through path120). As shown inFIG. 4, the partial overlap of heat interface122and HBM104can result in a majority (e.g., approximately 80%) of HBM's thermal energy being dissipated via path120created by the heat pipe118. In other examples, when heat interface122of heat pipe118overlaps substantially the entire length of HBM104, approximately substantially all of HBM's thermal energy can be dissipated via path120.

FIG. 5Aillustrates a front view andFIG. 5Billustrates a side view of an example ASIC with embedded HBM and heat pipe. Cooling systems500,550can at least include ASIC102, HBM104, primary heat sink108, heat pipe118and secondary heat sink114. As illustrated inFIG. 5A, primary heat sink108and secondary heat sink114are not in direct physical contact (e.g., separated by space124). By not being in direct physical contact, the primary and secondary heat sinks can establish distinct thermal energy paths (e.g.,106A and106B, and120). Establishing distinct thermal energy paths can enable more efficient dissipation of thermal energy from ASIC102(e.g., through primary heat sink108) and from HBM104(e.g., laterally through heat pipe118to secondary heat sink114). In examples where there is direct contact between the primary and secondary heat sink, efficient of dissipation of thermal energy is reduced (e.g., there are no distinct thermal energy paths).

As further illustrated inFIGS. 5A and 5B, the overall footprint of cooling systems500,550(e.g., size of primary heat sink108) is not increased with the addition of secondary heat sink104and heat pipe118. The arrangement of the elements (e.g.,102,104,108,110,112,114,118,122) can be in any order, as long as the overall footprint is not exceeded and the airflow through the primary and secondary heat sinks are in similar directions. In other examples, different types of packages can be presented. For example, package100can include ASIC102and not HBM104. HBM can be added as a separate element to the cooling systems (e.g.200,300,500,550).FIG. 5AandFIG. 5Bcan also illustrate the direction airflow through primary heat sink108and secondary heat sink114.

FIGS. 6A and 6Bare example heat maps illustrating temperatures of the ASIC and embedded HBM without600and with650the heat pipe, respectively. It should be appreciatedFIGS. 6A and 6Bare provided as examples and the temperatures and data reflected should be not considered limiting. As illustrated inFIG. 6A, the maximum temperature of ASIC102is 111.1 C and, the maximum temperature of HBM104is 97.2 C. As illustrated inFIG. 6B, with the addition of heat pipe118, the resulting dissipation of heat from HBM104, the maximum temperature of ASIC102is 109.9 C and the maximum temperature of HBM104is 93.3 C. The addition of heat pipe118can decrease the maximum temperature of HBM at least approximately 4 C (in the illustrated orientation). It can be appreciated, in examples where heat pipe118extends across HBM104, a larger decrease in maximum temperature can occur. The maximum temperatures when utilizing the heat pipes in an ASIC with embedded HBM can be approximately 78 C in the heat pipe, 93.3 in the HBM, and 109.9 in the ASIC. The remaining thermal energy from the HBM (e.g., thermal energy not dissipated via the heat pipe) is still dissipated through the primary heat sink (e.g.,106A). It can also be appreciated, that the temperature values above are provided as an example, and the temperature values are variable from one application to the next. The example temperature values are also illustrated to show a gradient (or differences) between the ASIC with an embedded HBM with and without the cooling configuration and having a gradient (from without to with) equal to or below the maximum temperature of the HBM.