High-performance integrated circuits (for example, microprocessors, network processors, and high-speed static random access memory (SRAM)) run at high clock speeds and have high standby currents, which can result in very high heat generation during operation. Numerous difficulties are encountered in attempting to adequately remove thermal energy from such integrated circuits to avoid overheating of the circuits.
FIG. 1 shows a prior art semiconductor package construction 10 illustrating conventional methodologies for cooling an integrated circuit. The construction includes an integrated circuit chip or die 12. Such die will comprise a semiconductor material substrate and various integrated circuit components associated with the substrate. The substrate can, for example, comprise, consist essentially of, or consist of monocrystalline silicon. To aid in interpretation of the claims that follow, the terms “semiconductive substrate” and “semiconductor substrate” are defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above.
The die 12 has a frontside surface 14, and has a backside surface 15 in opposing relation to the frontside surface. Typically, the frontside surface of the die will be a surface of a passivation layer formed over various integrated circuit components that are in turn formed over a surface of a semiconductor substrate comprised by the die. In contrast, the backside surface of the die will frequently be a surface of the semiconductor wafer substrate comprised by the die.
The package 10 has various connectors 16 shown along the frontside surface of the die. Such connectors can be, for example, wire bonds or solder balls, and will connect circuitry associate with die 12 to other circuitry external of the die. The package 10 also comprises a board 18 adjacent connectors 16, and having additional conductive connectors 20 on an opposing side from the connectors 16. The board 18 can have various interconnects extending therethrough and connecting conductive connectors 20 on one side of the board with conductive connectors 16 on the other side of the board. The connectors 20 can correspond to pins, solder balls, or other conductive connections utilized for electrically connecting package 10 to circuitry associated with an electronic system.
The package 10 has cooling structures provided adjacent the backside 15 of die 12, and configured for removing thermal energy from the die. The shown structures include a heat spreader 22 and a heat sink 24. The heat spreader is configured to take heat from localized heated regions of die 12 and spread it more uniformly across a relatively large expanse, and the heat sink is utilized to transfer the heat to the environment external of package 10.
The heat spreader can comprise metal, and frequently will comprise a metal having excellent thermal conductivity, such as, for example, copper. Similarly, the heat sink will typically comprise a metal having excellent thermal conductivity and can, for example, comprise copper or aluminum. The heat sink will typically comprise a plurality of projections to enhance transfer of thermal energy from the heat sink to the surrounding environment. The exemplary heat sink 24 comprises a plurality of fins extending outwardly from die 12.
Although the heat sink and heat spreader can be separate from one another, and can have different functions, it is also possible for a single component to be provided that has the functions of both the heat sink and the heat spreader. For this and other reasons, the term “heat sink” is commonly utilized, in modern parlance to be generic in referring to structures traditionally referred to as either heat spreaders or heat sinks. Thus, the term “heat sink” is frequently utilized to refer to traditional heat sinks, as well as to traditional heat spreaders, as well as to structures having the combined functions of the traditional heat sinks and heat spreaders. For purposes of interpreting this disclosure and the claims that follow, the term “heat sink” is to be understood to be generic to both conventional heat spreaders and heat sinks unless it is expressly stated that the term is specific to a traditional heat sink.
The thermal transfer materials of package 10, as well as other thermal transfer materials known in the art for utilization in cooling semiconductor devices, suffer from a number of drawbacks. For instance, conventional heat sinks are made of black-coated metallic materials, and can be large and bulky; and conventional heat spreaders can also be unsuitably bulky. Additionally, conventional cooling methodologies lack suitable efficiency for cooling high-performance integrated circuitry, such as, for example, circuitry being developed for mobile devices like laptops, cell phones, personal digital assistants, etc.
It would be desirable to develop improved structures and methods for cooling integrated circuitry.