OPTIMIZATION TECHNIQUES Heat management methods in power modules

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This article describes modern heat treatment methods such as direct liquid cooling and thermoelectric coolers, improving thermal conductivity and reliability for demanding applications. Without considering thermal stress aspects that stem issues or attempting to reduce thermal resistance through complex internal connections, these procedures are intended for applications where efficient heat management is essential for performance and longevity.

Heat management is key in power modules to maintain optimal operating temperatures, extend component life, prevent damage, and ensure consistent performance. Semiconductors can degrade, drastically reducing efficiency and shortening the lifespan of the entire system due to overheating caused by switching and conduction losses, ultimately leading to premature failures and higher costs.

The most notable applications are found across various sectors, including electric vehicles, smart factories, industrial automation, and general power electronics, to enhance device efficiency, reliability, and lifespan.

The following industries utilize heat management in their power modules: lighting, industrial automation, renewable energy (wind and solar), automotive (especially electric vehicles), aerospace, and consumer electronics.

Next, we'll cover advanced cooling techniques used in power modules that complement traditional approaches such as forced-air cooling with fans and heat sinks used on PCBs.

Direct Liquid Cooling

Direct Liquid Cooling (DLC) is an advanced cooling technology where a specialized liquid coolant circulates directly onto heat-generating components, like processors (CPUs and GPUs), to absorb and remove heat more efficiently than traditional air cooling, enabling devices to operate at optimal performance levels while reducing energy consumption.

If applied to a chip, it must be attached to a cold plate to achieve efficient heat management. This way, the coolant flows through its internal channels, absorbing heat from its surfaces.

To achieve continuous heat removal, a pump is responsible for circulating this coolant through the system. The cooling cycle is completed when the absorbed heat is transferred from the refrigerant to a radiator or cooling tower through the action of the heat exchanger.

In data center environments, this advanced form of liquid cooling benefits processor chips that may be prone to heat exposure. By requiring less energy to operate than air cooling systems, operating costs and the carbon footprint are reduced.

By keeping CPU temperatures lower for extended periods, they can run at extreme speeds for longer, avoiding thermal throttling¹⁾ and maintaining peak performance. It also achieves space optimization, allowing data centers to maximize their processing power in a smaller footprint.

Thermoelectric Cooler

A thermoelectric cooler (TEC) uses the Peltier effect²⁾ through a solid-state heat pump to transfer heat from one side of a module to the other when an electrical current is applied. This process allows for precise and compact cooling without liquid refrigerants or moving parts, leading to high reliability and longer lifespan.

Battery management systems (BMS) are compact and efficient in electric vehicles, where TEC is integrated with highly conductive materials such as copper plates and heat sinks to enhance cooling efficiency. Acting as a heat pump, TEC absorbs heat from the battery and dissipates it to a heat sink or the surrounding environment, enabling precise, localized temperature regulation.

Applications in processors focus on the TEC's ability to cool specific critical points, improving reliability and performance in high-power-density systems such as graphics processing units (GPUs) and tensor processing units (TPUs).

By controlling the applied current, cooling intensity can be adjusted, enabling adaptation to varying thermal loads. For localized cooling on chips, microscale and film-based TECs can be integrated, attaching them directly to hot spots, minimizing thermal resistance and electrical losses.

Microscale TECs are suitable for cooling microelectronic components, sensors, and optoelectronics in confined spaces, providing precise temperature control and rapid thermal response. Film-based thermoelectric coolers (TFTECs) remove heat directly, without using traditional coolants, making them ideal for cooling microchips, quantum cascade lasers, and other integrated circuits.

Considerations to keep in mind

Among the most common mistakes in heat management in power modules using traditional methods are underestimating heat generation, leading to insufficient cooling mechanisms, and improper thermal interface design, such as not including heatsinks or thermal vias and incorrectly applying thermal paste.

Other frequent errors that cause thermal imbalances include using unsuitable cooling solutions, ignoring the operating environment and ambient temperature, and poor PCB design, which leads to high power density and hot spots resulting from inefficient heat dissipation.

Among the solutions designers propose to address these issues are: minimizing thermal interfaces through component integration, reducing thermal resistance through improved internal connections, and utilizing advanced cooling techniques such as phase-change materials (PCMs) to facilitate heat transfer.

A solid understanding of how heat is generated in components, combined with a mastery of key concepts such as thermal throttling and the Peltier effect, ensure successful heat management. Starting with a detailed analysis of advanced cooling techniques, this article addresses its benefits and applications in real-world use cases.

The purpose of this study is not to forward a thermal management project on real equipment, as additional aspects affecting heat transfer, such as long-term reliability under high heat flux and semiconductor materials, are not taken into account. However, they serve as a starting point for heat treatment procedures on many components in power modules.

References

1) Thermal throttling is an automatic protective measure where a component, like a CPU or GPU, lowers its performance to prevent overheating and potential damage from high temperatures.

2) The Peltier effect occurs when a direct electric current creates a temperature difference between the two sides of the thermoelectric cooler, transporting heat from one surface to the other.

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