Analysis of Chip-Level Thermal Management Cooling Technologies

Chip Thermal Management: Key Technologies for Ensuring Stable Operation of Integrated Circuits and Microelectronic Systems

With the rapid advancement of integrated circuit (IC) technologies—particularly the introduction of advanced packaging techniques like 3D integration—chip integration density and power consumption continue to rise, exacerbating thermal challenges. Below are key cooling technologies summarized by researchers:

Air Cooling

Primarily categorized into two types based on driving mechanisms:

• Natural Convection Cooling: Utilizes air as the heat transfer medium, relying on fluid density differences to induce airflow for heat dissipation. While simple and reliable, its cooling capacity is limited.

• Forced Convection Cooling: Actively drives airflow using fans, significantly improving airflow rates and enhancing heat removal. Estimated to offer 5–10 times greater cooling capacity than natural convection, this is the most widely used method for general applications but may struggle with high heat flux scenarios.

Microchannel Cooling

Liquid cooling is gaining popularity due to rising thermal design power (TDP) and power density in processors, memory, and other IT components. Compared to air cooling, liquid cooling demonstrates superior thermodynamic efficiency owing to the higher heat capacity of liquids, enabling efficient energy absorption, storage, and transport.

Cold Plate Liquid Cooling:

The most common form of liquid cooling, where cold plates replace traditional heat sinks and pumps circulate coolant instead of fans. This method effectively removes concentrated heat in confined spaces, outperforming air cooling systems that disperse heat across larger radiators. Research focuses on optimizing coolant media and microchannel structures. By integrating microfluidic channels on or within chip surfaces, liquid coolant directly absorbs and removes heat, making it ideal for high heat flux applications.

Embedded Cooling

Integrates cooling elements (e.g., microchannels or heat pipes) directly into chips or packaging to enhance heat transfer efficiency. A cutting-edge approach involves embedding micron/submicron-scale microchannels into semiconductor chip backplanes, enabling coolant circulation for direct chip cooling—termed Embedded Liquid Cooling (ELC). This architecture minimizes thermal resistance by shortening heat transfer paths, leveraging the chip backplane as a radiator.

Immersion Cooling

A high-efficiency method where heat-generating devices are submerged in dielectric fluids or non-conductive coolants. This ensures direct contact between coolant and components, achieving superior heat transfer and temperature uniformity. Compared to air and cold plate cooling, immersion cooling eliminates vibration from moving parts, prevents oxidation of electrical contacts, reduces temperature fluctuations, and mitigates external environmental impacts (e.g., particulates, humidity).

Immersion cooling is divided into:

• Single-Phase Immersion Cooling (SPIC): No phase change occurs; coolant exchanges heat through convection. Safer due to no gas generation.

• Two-Phase Immersion Cooling (TPIC): Leverages coolant phase change (evaporation/condensation) and latent heat for enhanced cooling capacity.

Spray Cooling

Directs fine coolant droplets onto heat sources via atomizing nozzles, utilizing phase change (evaporation) for rapid heat removal. Upon impact, droplets spread, form thin films, and undergo evaporation or nucleate boiling. This enables high heat flux dissipation through three stages:

1. Single-Phase Convection at low surface temperatures.

2. Nucleate Boiling as temperatures rise, entering a two-phase regime.

3. Film Boiling at extreme temperatures, where heat flux stabilizes.

Jet Impingement Cooling
Employs high-speed liquid or gas jets to strike heat sources directly, leveraging impact force and evaporation. The technique creates thin thermal/velocity boundary layers on surfaces, maximizing heat transfer. Multiple nozzles are often used to expand cooling coverage.

Two configurations:

• Indirect Cooling: Separates coolant from electronics (e.g., via cold plates).

• Direct Cooling: Coolant contacts chips directly, offering higher efficiency but requiring safeguards against physical/chemical damage.

Heat Pipes
Passive two-phase devices that transfer heat via repeated evaporation/condensation cycles. Key advantages include low thermal resistance, high conductivity, compactness, and reliability. A heat pipe comprises three sections:

1. Evaporator: Absorbs heat, vaporizing working fluid.

2. Adiabatic Section: Transports vapor.

3. Condenser: Releases latent heat, condensing vapor back to liquid. Capillary forces in the wick structure return liquid to the evaporator.

Thermoelectric Cooling (TEC)

Uses the Peltier effect to create temperature differentials via electric current in thermoelectric materials. While compact and solid-state, TEC systems face efficiency and cost limitations. Future research targets advanced materials and system designs.

Electrocaloric Cooling (EC)

An emerging solid-state technology leveraging reversible temperature changes in dielectric materials under electric fields. EC cooling eliminates compressors or pumps, relying on entropy modulation of dipoles. Key materials include:

• Ceramics: High thermal conductivity, suited for thick devices (e.g., multilayer ceramic capacitors).

• Polymers: Require ultrathin structures to minimize thermal resistance.