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Protection Mechanisms for Thyristors


Semiconductor devices play a pivotal role in the modern landscape of electronic systems, powering an array of applications across industries. However, their efficient operation is contingent upon maintaining optimal operating conditions, particularly in the context of temperature management. One of the critical challenges that semiconductor devices face is the risk of overheating, a phenomenon that can lead to irreversible damage and compromise their functionality.

This discourse delves into the intricate dynamics of overheating in semiconductor devices, with a specific focus on mitigating risks and fortifying these components against potential damage. By exploring the nuanced scenarios that contribute to overheating and unveiling tailored protective measures, we aim to provide a comprehensive understanding of the importance of temperature control in ensuring the reliability and longevity of semiconductor devices. Through this exploration, we unravel the multifaceted strategies that encompass monitoring, detection, and circuit design enhancements, ultimately contributing to the creation of robust electronic systems in an ever-evolving technological landscape.

Standard Gate-Turn-Off Thyristors1
Standard Gate-Turn-Off Thyristors1
Standard Gate-Turn-Off Thyristors2
Standard Gate-Turn-Off Thyristors3
Standard Gate-Turn-Off Thyristors4
Standard Gate-Turn-Off Thyristors4

Overvoltage Protection

Within the intricate landscape of electronic devices, overvoltage emerges as a multifaceted challenge, originating from both internal and external sources. This chapter serves as a foundational exploration, providing in-depth insights into the various factors contributing to overvoltage and underscoring the nuanced considerations necessary for implementing robust protection mechanisms.

  1. Internal Overvoltage Dynamics: Carrier Storage Effects in Power Semiconductors:

    A fundamental aspect of internal overvoltage lies in the intricate dynamics of carrier storage effects within power semiconductors. As carriers accumulate, the potential for overvoltage surges, necessitating a nuanced understanding of this phenomenon to develop effective protection strategies.

  2. External Overvoltage Factors: Unveiling Environmental and Circuit Influences:

    External overvoltage is a consequence of dynamic circuit processes and environmental factors. The chapter dissects the impacts of switches along the circuit and external elements like lightning strikes. Specific scenarios, including the no-load switch of transformers, the switch of inductive loads, and fuse breaking, are explored to highlight the diverse external sources of overvoltage.

  3. Microsecond-Level Vulnerabilities in Semiconductor Components:

    A dedicated section emphasizes the susceptibility of thyristors and diodes to microsecond-level overvoltages. The discussion delves into the unique challenges and vulnerabilities faced by these components, underlining the critical importance of understanding potential risks for crafting targeted protection strategies.

  4. Essential Considerations in Overvoltage Protection Design:

    As the chapter unfolds, attention shifts towards pivotal elements in designing effective protection against overvoltage. Specific focus is given to blocking capability (VDRM, VRRM) and the critical voltage rise rate (dv/dt)cr. These considerations lay the groundwork for readers to comprehend the intricacies involved in designing protection mechanisms.

An overburdened voltage thyristor chip
An overburdened voltage thyristor chip
An overburdened voltage thyristor chip
An overburdened voltage thyristor chip

Current Overload Protection

In the intricate realm of thyristor operation, their notable short-term, robust overcurrent capability, reaching approximately 30 times the half power frequency cycle (under the highest junction temperature), stands as a testament to their resilience. However, it is imperative to delve into the nuanced circumstances under which overcurrent damage may manifest, considering the multifaceted nature of thyristor behavior.

  1. Insufficient Triggering Leading to Amplified Gate Destruction:

    One critical scenario that can precipitate overcurrent damage is insufficient triggering. In such cases, the inadequacy in the triggering process may lead to the destruction of the amplifying gate, posing a significant risk of overcurrent damage to the thyristor. Achieving optimal triggering becomes paramount to prevent potential gate-related failures.

  2. Inadequate Circuit Reactance and Short Circuit Faults:

    Another vulnerability arises when the circuit reactance is insufficient or in the presence of load short circuits. In such instances, the risk of amplifying gate destruction heightens. Proper circuit design becomes instrumental in maintaining an adequate level of reactance, thereby mitigating the potential for overcurrent-induced damage to the thyristor.

  3. Prolonged Overcurrent Resulting in Overheating and Damage:

    A noteworthy concern involves the potential consequences of prolonged exposure to overcurrent conditions. Continuous overcurrent situations can lead to extended periods of overheating, ultimately causing thermal damage to the thyristor. Vigilant monitoring and timely intervention are imperative to mitigate the risks associated with long-term overcurrent exposure and prevent catastrophic failures.

An overloaded current thyristor chip
An overloaded current thyristor chip

Overheat Protection

Exceeding the specified maximum operating junction temperature poses a significant risk of overheating damage to the semiconductor device. Two primary scenarios merit careful consideration regarding the prevention of overheating and associated destruction:

  1. Inadequate Heat Dissipation Leading to Overheating Destruction:

    One of the critical factors influencing overheating is insufficient heat dissipation. Implementing a comprehensive strategy involves incorporating temperature monitoring mechanisms for heat sinks. This includes deploying sensors to detect variations in heat sink temperatures, enabling timely intervention to prevent overheating. Additionally, integrating a system for detecting fan malfunctions ensures that the cooling mechanism operates optimally. Monitoring cooling water flow further enhances the overall heat dissipation efficiency, providing a multi-layered approach to prevent overheating-related damage.

  2. Prolonged Overcurrent and the Risk of Overheating Damage:

    The second notable risk factor involves the potential for prolonged overcurrent conditions, which can result in overheating and subsequent damage. To address this concern, an essential step is the refinement of the circuit design. This includes the implementation of measures to prevent and mitigate long-term overcurrent situations. Ensuring optimal circuit design not only prevents overheating but also contributes to the longevity and reliability of the semiconductor device.

By delving into these specific risk scenarios and implementing tailored measures, it becomes possible to fortify the semiconductor device against overheating-related damage. A holistic approach that encompasses monitoring, detection, and proactive circuit design ensures robust protection, ultimately enhancing the overall performance and durability of the electronic component.

Installation Guidelines for Thyristors

Module Devices:

  1. Heat Sink Surface Quality: Ensure the flatness of the heat sink surface is within the tolerance of ≤30um and the roughness is ≤10um. This guarantees a smooth and even surface for effective heat dissipation.
  2. Cleanliness Standards: Prior to installation, rigorously clean the heat sink surface, eliminating any oil stains or foreign particles. A thorough wipe-down with a clean non-woven cloth is recommended to maintain a pristine surface.
  3. Thermal Conductive Paste (TCP) Application: When applying Thermal Conductive Paste (TCP), it is crucial to achieve uniform coverage. The recommended thickness for the application of silicone grease is 50-100um, ensuring an optimal interface for heat transfer.
  4. Bolt Tightening Procedure: During the bolt tightening process, follow a diagonal sequence for manual tightening initially. Subsequently, adhere to the torque values specified in the technical documentation, guaranteeing secure and evenly distributed fastening.

Flat Plate Devices:

  1. Heat Sink Surface Specifications: Adhere to stringent specifications for the flatness and roughness of the heat sink surface, ensuring it remains within the prescribed limits of ≤10um. This meticulous attention to surface quality is critical for efficient heat dissipation.
  2. Pre-Installation Surface Preparation: Maintain a spotless heat sink surface by eliminating any oil residues or foreign particles before the installation process. Employ a clean non-woven cloth for a meticulous cleaning routine.
  3. Specialized Press-Fit Installation: Utilize a specialized press-fit machine for installation, employing a two-stage pressure application method to prevent any pressure leakage. This involves initially pressurizing the machine to 80% of the specified pressure, tightening the bolts to the recommended torque. Follow this by a secondary pressurization to the maximum allowable value, re-tightening the bolts to the specified torque.
  4. Consideration for Conductive Adhesive: If deemed necessary, contemplate the application of conductive adhesive on both sides of the flat plate device. This additional measure enhances conductivity and ensures optimal performance in diverse operational conditions.

These meticulous guidelines for both module and flat plate devices underscore the importance of precision, cleanliness, and adherence to specifications in the installation process, ultimately contributing to the reliability and efficiency of the semiconductor components.

Thyristor installation


In conclusion, safeguarding semiconductor devices from overheating-related damage is paramount to ensuring their optimal performance and longevity. The risk of overheating, stemming from exceeding the maximum operating junction temperature, demands a multifaceted approach for prevention.

Implementing effective heat dissipation strategies, including temperature monitoring for heat sinks, fan malfunction detection, and monitoring cooling water flow, serves as a critical first line of defense. These measures collectively contribute to maintaining temperatures within safe limits, mitigating the risk of overheating-induced destruction.

Furthermore, addressing the challenge of prolonged overcurrent requires a meticulous focus on circuit design. By refining the circuitry to prevent and manage long-term overcurrent conditions, the potential for overheating damage is significantly reduced. This not only enhances the resilience of the semiconductor device but also underscores the importance of proactive design considerations in ensuring sustained reliability.

In essence, a comprehensive approach that integrates monitoring, detection, and circuit design enhancements forms a robust defense against overheating risks. By adopting these measures, electronic components can operate optimally, providing a reliable and durable foundation for various applications in diverse operational environments.


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For all your thyristor inquiries and purchases, look no further than LJ-MD. Visit our website, diodethyristor.com, to discover our wide range of high-quality stud type thyristors and related products. Our experienced team is ready to assist you in selecting the ideal components to meet your manufacturing requirements. Contact us today to embark on a journey toward improved efficiency, precision, and success in your industry.

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