With the continuous development of society, semiconductors, as electronic materials, are widely used in production and daily life, promoting the development of various fields. We should have a comprehensive understanding of the performance of semiconductor materials so that we can better utilize their functions. In refrigeration and heat dissipation systems, the heat dissipation effect affects the performance of semiconductor refrigeration systems. To improve the cooling effect, thermoelectric coolers are now widely used in portable refrigeration devices.
1. The concept of semiconductors
Semiconductors are materials whose conductivity at room temperature falls between that of conductors and insulators. They are primarily used in radios, televisions, and temperature measurement. Semiconductors are materials with controllable conductivity, ranging from that of insulators to conductors. From the perspective of science, technology, and economic development, semiconductors have impacted people's daily work and lives; however, this material was not recognized by the academic community until the 1930s.
2. Properties of semiconductor materials
(1) Elemental Semiconductors. Elemental semiconductors refer to semiconductors composed of a single element, among which silicon and tin were studied earlier. They are solid materials with semiconductor properties composed of the same element, and are easily affected by trace impurities and external conditions. Currently, only silicon and germanium have good performance and are widely used, while selenium is used in electronic lighting and optoelectronic fields. Silicon is widely used in the semiconductor industry, mainly due to the influence of silicon dioxide, which can form a mask in device fabrication, improve the stability of semiconductor devices, and facilitate automated industrial production.
(2) Inorganic compound semiconductors. Inorganic compounds mainly consist of semiconductor materials composed of a single element, although there are also semiconductor materials composed of multiple elements. The main semiconductor properties include compounds combining Group I with Groups V, VI, and VII; Group II with Groups IV, V, VI, and VII; Group III with Groups V and VI; Group IV with Groups IV and VI; Group V with Group VI; and Group VI with Group VI. However, due to the characteristics of the elements and the manufacturing method, not all compounds can meet the requirements of semiconductor materials. This type of semiconductor is mainly used in high-speed devices. InP transistors have higher speeds than those made from other materials and are mainly used in optoelectronic integrated circuits and radiation-resistant devices. Materials with high conductivity are mainly used in LEDs and other applications.
(3) Organic compound semiconductors. Organic compounds refer to compounds containing carbon bonds in their molecules. When organic compounds and carbon bonds are stacked perpendicularly, a conduction band can be formed. Through chemical addition, these compounds can enter the energy band, thus generating electrical conductivity and forming organic compound semiconductors. Compared with previous semiconductors, this type of semiconductor is characterized by low cost, good solubility, lightweight materials, and easy processing. Its conductivity can be controlled by manipulating the molecules, and it has a wide range of applications, mainly in organic thin films and organic lighting.
(4) Amorphous semiconductors. Also known as amorphous semiconductors or glass semiconductors, they belong to a class of semiconducting materials. Like other amorphous materials, amorphous semiconductors have a short-range ordered and long-range disordered structure. They are mainly formed by changing the relative positions of atoms, altering the original periodic arrangement. The main difference between crystalline and amorphous semiconductors lies in whether the atomic arrangement has a long-range order. The performance control of amorphous semiconductors is difficult, but with technological advancements, amorphous semiconductors have begun to be used. This manufacturing process is simple and is mainly used in engineering applications. They have excellent light absorption properties and are primarily used in solar cells and liquid crystal displays.
3. Types of semiconductor cooling and heat dissipation systems
(1) Air convection cooling. Air convection cooling mainly uses heat sinks as components. The temperature difference between the atmosphere and air convection carry away excess heat, thus achieving a cooling effect. This method of heat dissipation is mainly affected by three factors: First, the thermal conductivity of the heat sink, which maximizes the contact between the heat-generating components and the air. Second, the airflow speed. When the speed increases, the heat dissipation speed increases. Therefore, an additional fan is added to the convection cooling system to increase the airflow speed, accelerate the removal of heat, and improve the heat dissipation effect. Third, the temperature of the air itself. High temperatures in summer will affect the heat dissipation effect, mainly because the air is also very hot, making it difficult to ensure the heat dissipation effect. This method itself has a relatively low heat dissipation efficiency.
(2) Water cooling. This is a relatively new and widely used cooling method. It mainly uses coolant to circulate in closed pipes, thus removing heat from components. Water cooling is more efficient than the previous method. Compared to fan cooling and passive heat sink cooling, its cooling effect is about 100 times greater. It has high cooling efficiency and low noise, and is mainly used in machinery. In addition to adding a fan, water cooling radiators also make full use of the characteristics of convection heat dissipation to improve the cooling effect. This cooling method is mostly used in water pipes, power supplies, and water pumps. It is complex to operate and difficult to maintain, which limits its application, especially in situations where it is inconvenient to carry and is not suitable for small-sized applications.
(3) Heat pipe heat dissipation. The main characteristic of a heat pipe is its ability to quickly maintain a constant temperature. It is a metal tube and mainly consists of a liquid working fluid, a core, and a shell. The shell contains a core with a capillary structure, on which the liquid working fluid is placed. This allows for multiple circulations of the liquid within the tube to transfer heat. This liquid working fluid has good thermal conductivity, a low boiling point, and low viscosity, enabling it to achieve a heat conduction effect during continuous circulation. The design of the core is influenced by the capillary structure, which reduces contact thermal resistance. The shell is in a closed space, which can better generate a certain pressure for the circulation of the liquid working fluid. The shell has a certain degree of plasticity and can be modified to the required shape for convenient use.
During operation, a heat pipe radiator consists of a heat dissipation component at one end and a heat sink at the other. Connecting the two allows the liquid working fluid inside the pipe to vaporize, creating a pressure difference that allows it to flow to the other end, thus carrying away heat. Heat is released at the cooler end and then transferred to the air through the heat sink and fan. This cycle repeats to achieve the purpose of heat dissipation.
Heat pipe cooling technology primarily utilizes thermal superconductivity. Heat pipe radiators are a novel heat dissipation technology that combines the advantages of air convection cooling to create a new type of radiator. They consist of heat pipes, heat sinks, and fans, with the heat pipes being the main component. The heat sinks transfer heat, and the fans accelerate convection. Heat pipe radiators represent a completely new and improved cooling method, characterized by lightweight materials, high efficiency, low noise, and portability, making them well-suited to current green and environmentally friendly principles and particularly suitable for spaces with limited space.
4. Conclusion
In conclusion, with economic development, people are paying increasing attention to environmental protection. To address the greenhouse effect, research into refrigeration technology has begun, leading to various refrigeration methods, with thermoelectric cooling being the primary approach. As people increasingly use electronic devices, heat dissipation remains a crucial issue requiring further research.
