**Experimental Discussion on Improving the Temperature Resistance of LED Light Sources (II)**
**Introduction**
Semiconductor lighting has become a technological revolution in this century, yet it is still in its infancy in terms of technical maturity. Despite rapid progress in high-power white LED technology, issues such as light degradation and heat dissipation remain significant challenges that hinder the widespread adoption of LED lighting. These inherent problems affect every stage of the supply chain, from chip manufacturing to packaging, material selection, and lamp development.
Currently, there is a lack of clear understanding and authoritative explanations regarding the concept of light decay, its causes, and effective solutions. This ambiguity leads to confusion and a chaotic environment where many adopt unproven or ineffective techniques. While heat dissipation methods have been widely used to reduce light degradation, their impact has been minimal. As a result, solving the issue of light decay has become a central concern for the industry.
The question arises: Why haven't designers explored alternative approaches to address the root causes of light degradation? In this article, the author delves into both theoretical and practical aspects of improving the temperature resistance of LED light sources to reduce light decay. Further articles and experimental reports will follow.
**Keywords**
LED light effect, LED thermal resistance, LED light decay, WFCOB light source, LED module lighting
**Table of Contents**
Chapter One
1. LED light effect: Understanding the difference between transient and steady-state light effects
2. LED thermal resistance: Distinguishing internal and external thermal resistance
3. LED light decay: Luminous flux reduction is not equivalent to irreversible damage
Chapter Two
4. Causes of LED light decay
5. Enhancing temperature resistance can reduce LED light decay
6. Why improve the temperature resistance of LED light sources?
7. How to make LED light sources withstand high temperatures
Chapter Three
8. Aluminum substrates are unnecessary for achieving 3750V insulation
9. Solving drive power short circuits
Chapter Four
10. Introducing the WFCOB light source
Chapter Five
11. Introducing an LED module lighting system
**Chapter Two: The Cause of LED Light Decay**
1. LED light decay refers to irreversible failure caused by material damage.
Light decay occurs when, after prolonged use, the luminous intensity of an LED decreases below its original level. Although China has no official standard for light decay, industry norms often consider a luminous flux maintenance rate of ≥70% after 5000 hours as acceptable.
2. A decrease in luminous flux does not equate to light decay.
When an LED operates, its light output may temporarily decrease due to rising junction temperature. However, if the component doesn’t exceed its temperature limit, the light intensity typically recovers once the temperature drops. This temporary decline should not be considered as light decay. True light decay involves permanent loss of luminous flux due to material damage.
3. The main cause of light decay is poor thermal resistance of the encapsulation material.
While chips and phosphors are inorganic and can withstand high temperatures, the gel or encapsulant used in packaging is often the weak link. Most current encapsulants can only tolerate up to 100°C, but in high-power applications, temperatures can exceed 200°C. Prolonged exposure leads to cracking, carbonization, and separation from the chip, resulting in light decay.
From the luminaire system perspective, light decay is also influenced by the thermal resistance of the entire system, including heat dissipation channels, materials, and design. The quality of the packaging process, the type of support structure, the phosphor’s performance, and the thermal resistance of the encapsulant all play critical roles in determining the longevity of the LED.
**Chapter Five: Enhancing Temperature Resistance to Reduce Light Decay**
1. Why Improve the Temperature Resistance of LED Light Sources?
LEDs are semiconductor devices that generate relatively low heat, making natural cooling less efficient. Heat dissipation is more effective when the temperature difference between the heat sink and ambient air is greater. According to theory, radiative heat transfer increases with the fourth power of temperature. Therefore, raising the operating temperature of the heat sink allows for better heat dissipation, which helps maintain stable light output over time without light decay. This approach not only reduces the size and cost of the heat sink but also improves the current capacity of the chip and extends the lifespan of the LED. It represents a revolutionary design strategy with multiple benefits.
2. How to Make LED Light Sources Withstand High Temperatures?
Several technologies have been explored to enhance the thermal performance of LEDs:
- **Flip-chip technology**: This method avoids using substrate glue and reduces thermal resistance. However, it requires expensive ceramic substrates and complex processes, limiting its widespread adoption.
- **Phosphor-away-from-chip technology**: Keeping phosphor away from the chip can reduce thermal resistance, but it presents challenges in optical matching and protection of the chip.
- **Liquid cooling**: Immersing LEDs in a transparent, heat-conductive liquid can significantly improve heat dissipation, though it is difficult to implement in small-scale designs.
- **COB (Chip-on-Board) packaging**: Multiple low-power chips arranged in parallel can improve the light-to-thermal resistance ratio.
- **High-temperature resistant materials**: Using advanced glues and substrates that can withstand extreme conditions is another promising approach.
- **Optimizing optical efficiency**: Reducing losses in the light path and lens design can lower overall system heating.
**Conclusion**
LEDs are low-temperature semiconductor devices, and their heat dissipation efficiency is limited under natural conditions. Increasing the operating temperature of the heat sink enhances heat dissipation, reducing light decay and extending the life of the LED. This innovative approach not only lowers costs but also improves performance, marking a significant advancement in LED design.
**About the Author**
Wang Feng, born in 1941 in Tianjin, holds a university degree and is an engineer with over 40 years of experience in electronic and mechanical systems. He has worked as a technician, chief engineer, factory manager, and company executive. With more than 10 years of experience in LED system design, he holds several invention patents. Wang possesses strong R&D capabilities and project management skills, along with extensive industry connections.
**Contact:**
Phone: 13430533163 | QQ: [Not provided]
Website: [http://news.chinawj.com.cn](http://news.chinawj.com.cn)
Editor: Hardware Business Network Information Center
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