In recent years, with the rapid development of solar power generation, new energy vehicles, and 5G communication, the preferred heat dissipation material with high thermal conductivity----aluminum alloy, has also been increasingly valued by people.
For solar power generation, the efficiency of inverters is an important factor to determine the performance of solar photovoltaic systems. Photovoltaic inverter is a type of power electronic device that converts the direct current which is generated in photovoltaic modules into alternating current. Its main components include switch transistors (IGBT, MOSFET), magnetic core components (inductor, transformer), etc. If the photovoltaic inverter fails due to high temperature, it will cause the photovoltaic system to shut down, resulting in huge power loss;
For new energy electric vehicles, the level of intelligence and electrification is increasing day by day, and the heat dissipation of their internal electrical equipment will directly affect the safety of the entire vehicle;
For 5G base stations, their power consumption is 2.5-3.5 times that of 4G. RRU (Remote Radio Unit) is an important device in 5G base stations, providing stable and reliable channels for user information exchange, ensuring accurate and real-time delivery of information.
In the work, each module will produce a large amount of heat. If not dissipated in time, it will lead to a high temperature rise in the internal environment.
Once the rated temperature is exceeded, electronic devices will not work stably, which will affect the timeliness of user information transmission and even shorten the service life.
In addition to the above fields, other components such as high-power LED lights and fiber optic modules in communication have high requirements for heat dissipation.
The electronic components in these devices have a rated operating temperature. If heat cannot be transferred to the outside world and the temperature continues to accumulate, it will become increasingly high.
In order to maintain the working temperature of electronic components inside such devices within the rated temperature range, ensure their efficiency and service life, it is necessary to use thermal conductive materials to transfer the internal heat of the device.
Therefore, high thermal conductivity materials used for manufacturing heatsinks have always been a focus of research.
Optical Module
5G communication base station
Multimedia housing of a certain new energy vehicle
Definition of thermal conductivity
Thermal conductivity is a parameter indicator that characterizes the thermal conductivity of a material. It indicates the thermal conductivity per unit time, per unit area, and under a negative temperature gradient, in units of W/m · K or W/m · ℃.
The thermal conductivity coefficients of common substances are shown in Table 1:
Table 1 Thermal conductivity coefficients of different substances
Metal suitable as a heat Sink material
From Table 1, it can be seen that for metallic materials, the heat dissipation coefficients of gold, silver, copper, and aluminum all exceed 200W/(m · K), all of them are indicating excellent thermal conductivity.
However, gold and silver cannot be widely used due to their soft texture, high density, and high cost;
The thermal conductivity coefficient of copper is also very high, which can be hindered by unfavorable conditions such as insufficient hardness, high density, slightly high cost, and high processing difficulty, and is less used in related fields of heat sinks fins;
Aluminum, as the metal with the highest content in the Earth's crust, is favored due to its high thermal conductivity, low density, and low price. However, due to the low hardness of pure aluminum, various formula materials are usually added in various application fields to make aluminum alloys, which obtain many characteristics that pure aluminum does not possess and become an ideal choice for heat sink processing materials.
Aluminum alloy heatsink
The research status of thermal conductive aluminum alloys is mainly divided into two categories: deformed aluminum and cast aluminum, each with different characteristics.
Deformed aluminum alloys: Existing research on the thermal conductivity of aluminum alloys mainly focuses on deformed aluminum alloys. Deformed aluminum alloys for thermal conductivity are mainly used in fields such as automobiles and electronics, such as aluminum alloy radiators, heaters, air conditioners, etc.
Compared to traditional copper or steel heat sinks, aluminum heatsinks have advantages such as light weight, good corrosion resistance, and low operating costs, and have been widely used. In terms of computer heat sinks, aluminum heat sinks have become mainstream, replacing copper/steel heat sinks and plastic fans. The disadvantage of deformed aluminum alloy is that it is difficult to make parts responsible for the structure.
Casting aluminum alloy: Casting belongs to solidification forming and is currently the best process for forming complex structural parts. For cast aluminum alloys, in order to ensure the filling performance and mechanical properties of the alloy, it is usually necessary to add more alloy elements. Silicon in cast aluminum alloys can improve the fluidity of the alloy, but as the silicon content increases, the thermal conductivity decreases. Therefore, the difficulty in developing high thermal conductivity cast aluminum alloys lies in ensuring good fluidity while still maintaining high thermal conductivity through alloy design and microstructure control.
The effect of heat treatment on thermal conductivity
The heat treatment of aluminum alloys mainly includes solid solution, aging, and annealing, and their effects on thermal conductivity are different.
Solid solution treatment: After solid solution treatment, the thermal conductivity and thermal diffusion performance of aluminum alloy in which the elements exist in a solid solution state are lower than those in the aluminum alloy matrix when the element phase is precipitated. The reason is that after solid solution treatment, the material structure undergoes significant changes, and some alloy elements and strengthening phases will dissolve again in the matrix, forming supersaturated solid solutions, causing severe lattice distortion, increased strength, and decreased thermal conductivity.
Aging treatment: Aging treatment can be divided into high-temperature aging and low-temperature aging. During high-temperature aging, atomic diffusion is easy, and the repair speed of vacancies and dislocation defects in the alloy is faster. The thermal conductivity will reach its highest value in a short period of time. With the extension of time, the thermal conductivity will have a downward trend, mainly due to the solid solution of excess Si and other elements in the alloy structure and the growth of precipitated phases at high temperatures; During low-temperature aging, due to slow atomic diffusion and minimal dissolution of elements such as Si at lower temperatures, the time for thermal conductivity to reach its peak is significantly longer than during high-temperature aging, and the improvement in thermal conductivity is not as significant as during high-temperature aging.
Annealing treatment: Different annealing temperatures and cooling methods have different effects on the thermal conductivity of aluminum alloys. As the annealing temperature increases, the thermal conductivity decreases, and the degree of decrease in thermal conductivity varies with different cooling methods. This is because as the annealing temperature continues to rise, more second phases in the aluminum alloy dissolve in the aluminum matrix, leading to an increase in the solid solubility of alloy elements, causing severe lattice distortion and hindering the movement of free electrons, resulting in a decrease in thermal conductivity. The thermal conductivity obtained by the slow cooling method with the furnace is higher than that of the fast cooling method, because the slower the cooling speed, the more favorable it is for the precipitation of solid solution atoms.
Therefore, in order to achieve higher thermal conductivity, a lower annealing temperature and cooling method with furnace cooling should generally be chosen.
