Thermal Runaway in Semiconductors: Causes, Effects and Prevention Strategies

Read below:

• Thermal runaway in semiconductors causes device failure due to uncontrolled heat buildup.

• Prevention requires smart design, thermal simulations and active monitoring.

• McKinsey Electronics supports engineers with tier-one components and expert on-ground guidance in South Africa.

Thermal runaway is a self-reinforcing failure mode in semiconductors where increased temperature leads to a higher current draw, which in turn generates more heat, ultimately spiraling out of control and destroying the device. This phenomenon is not limited to batteries but affects a wide spectrum of power semiconductors such as MOSFETs, IGBTs and GaN or SiC devices.

In this blog, we present a comprehensive analysis of the causes, effects and prevention strategies for thermal runaway, supported by real-world data, practical tools and a myth-busting section to clarify common misunderstandings.

What Causes Thermal Runaway?

1. Positive Feedback in Electrical Characteristics

Semiconductors like silicon and SiC can exhibit negative temperature coefficients in their resistance. As the temperature rises, resistance drops, allowing more current to flow, thus generating even more heat.

2. Current Crowding

Localized hotspots can form due to design defects or uneven current distribution. Once one region overheats, it can dominate power dissipation, causing neighboring areas to overheat as well.

3. Inadequate Thermal Management

Heat sinks, thermal vias and ventilation may be undersized or improperly implemented. Once the heat cannot be evacuated effectively, the device enters a thermal feedback loop.

Effects of Thermal Runaway

Power Dissipation Behavior vs. Temperature

Here’s how different MOSFET designs perform under increasing junction temperatures:

Power Dissipation vs. Junction Temperature

Devices with better thermal engineering, such as low R_DS (on), optimized die attach and thermal-enhanced packages, exhibit a slower rise in power dissipation, delaying the onset of runaway.

Prevention Strategies

Circuit and Layout Design Tips

• Use thermal vias under power devices (e.g., in D²PAK footprints) to enhance heat transfer.

• Widen copper traces on power nets to reduce resistive heating.

• Decouple hot components on the PCB to prevent mutual thermal interference.

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Simulation & Sizing Tools

• Thermal Simulation: ANSYS Icepak, COMSOL, and Siemens Simcenter for transient thermal models.

• Heat Sink Calculators: Fischer Elektronik and Aavid offer real-time estimation tools.

 Myth vs. Reality: Clearing Up Misconceptions

Takeaways

• Design with margin: Select components with higher thermal derating and robust packaging.

• Test under worst-case scenarios: Validate at high ambient temperatures and continuous load.

• Use thermal sensors: Include components like the TMP235 (TI) or LM75 (NXP) for active monitoring.

  
  

Thermal runaway in power semiconductors, such as MOSFETs, IGBTs and GaN/SiC devices, poses a significant challenge in high-reliability sectors like automotive and industrial automation. Addressing this issue requires not only robust component selection but also expert engineering support to ensure optimal thermal management and circuit design.

McKinsey Electronics, a trusted distributor of electronic components in South Africa, offers an extensive line card featuring products from leading tier-one manufacturers. Beyond distribution, they provide comprehensive support, assisting partners with circuit design services to recommend optimal components and pin-to-pin equivalents, thereby accelerating time to market.

In South Africa, McKinsey Electronics extends its services to include on-ground technical engineering support. Their team of engineers possesses vast expertise in electronic components and design, and is dedicated to client satisfaction, enabling efficient and prompt responses to the various demands of Original Equipment Manufacturers (OEM) and Electronics Manufacturing Service (EMS) clients.

For engineers and procurement teams dealing with thermal management challenges, McKinsey Electronics provides a diverse line card and the necessary technical support to implement effective prevention strategies against thermal runaway in semiconductor applications.

Contact McKinsey Electronics’ offices in South Africa.