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A thermal pad is part of a thermal system. How does a thermal pad dissipate the heat generated by the CPU? First, it is important to understand that there are three types of heat conduction: conduction, convection and radiation.Conduction refers to the exchange of kinetic energy between molecules, the collision of lower energy particles and higher energy particles to obtain energy (through direct physical contact), a single piece of heat conduction is not able to achieve heat conduction. In a word, conduction is the most important way that the heat conductor gets heat from the CPU.Convection is the transfer of heat through the movement of hot matter. It means that heat comes from a source of heat surrounded by a gas or liquid, which is transferred by the movement of molecules. We can achieve forced convection by adding a fan to the heat conducting sheet. Convection is the main mode of fan/heat exchanger combination refrigeration. Most of the heat generated by the CPU is carried away by the convection formed by the fan, and only a very small amount of the heat is emitted through radiation.In order to achieve this effect, a heat conductor must be designed to enhance the effect.Two methods are usually used to achieve this: the surface area of the heat conductor is increased as much as possible to facilitate the flow of air. The use of metal fins not only increases the heat conduction area, but a good metal fin design also makes convection more efficient. Make the contact surface between the thermal pad and the CPU as smooth as possible, otherwise, the thermal insulation layer will be formed between the CPU and the thermal pad. Of course, even if the contact surface is very smooth, there will inevitably be the existence of gaps, therefore, in the contact place can use thermal paste, thermal silicon grease or special thermal patch as an aid to improve the contact area.Radiation, as the name suggests that heat is emitted directly from a heat source in the form of an electromagnetic field (transmitted by photons). Radiation can take place in a vacuum. The heat transfer efficiency of radiation depends on the material of the heat source and the color of the surface.

Metal thermal pad as one of the important techniques to enhance heat transfer, is widely used to improve the heat transfer rate of solid wall. Such as aircraft, air conditioning, electronic components, motor vehicle thermal conductivity, Marine thermal conductivity and so on. The research on the heat transfer enhancement of thermal conductive pad has attracted the attention of many researchers at home and abroad, such as the research on the natural convection of thermal conductive sheet and the research on the forced convection of thermal conductive sheet.Heat conduction pad is mainly used to strengthen the heat conduction of the heating surface to the air, so we take the heat conduction sheet in contact with the air as the research object.Due to the low surface temperature (generally no more than 250 ℃) of the thermal conductive pad, the radiative heat transfer ratio of the thermal conductive pad group to the air is less than 3% of the total thermal conductivity. Therefore, the heat conduction between the surface and the surrounding environment is mainly convection heat transfer. Influence of height on the heat conduction of heat conducting pad: increasing the height of heat conducting pad H can increase the heat exchange area A, thus achieving the purpose of strengthening heat transfer. However, increasing the height will reduce the local heat transfer coefficient on the top of the heat conducting sheet and lead to the decrease of the average heat transfer coefficient. In addition, the height also affects the temperature drop from the base surface of the heat conducting sheet to the end. The higher the height, the greater the temperature drop, resulting in a decrease in the average temperature difference between the surface and the surrounding atmosphere, which is not conducive to heat conduction.In fact, the height of the heat conductor will also be limited by the overall size of the machine. Influence of thickness on the heat conduction of heat conducting sheet: the thinner the heat conducting sheet is, the more heat conducting sheet can be loaded per unit length, thus increasing the heat conducting area and strengthening the heat conducting pad; Along with the rising of the slice thickness of thermal conductivity, thermal conductivity and surface atmosphere around the average heat transfer temperature difference Δ T decreases, which is harmful for thermal conductivity. In practical applications, thickness is often limited by the technological level. Generally, the thickness of the casting heat conducting sheet shall be no less than 2 mm, and the thickness of the machined heat conducting sheet shall be no less than 1 mm.

TIM-PAD-I, TIM-PAD-PRO, TIM-PAD-ULTRA are metal material with a melting point between 58 and 60 degrees. When the operating temperature of the CPU / GPU is higher than this range, the metal thermal conductive sheet can also be used to replace aluminum and copper sheets, which is an environmentally friendly product that complies with the EU ROHS standard.The heat dissipation performance of metal thermal pad is 60-70 times of water. Based on the unique thermal physical properties of low melting point metals, it can be widely used not only in the chip thermal management of high-performance servers, desktops, industrial computers, notebook computers, and communication base stations. , And also plays an indispensable role in many key areas, such as: advanced energy fields (industrial waste heat utilization, solar thermal power generation, focused photovoltaic cell cooling, fuel cells), aviation thermal control fields (satellite, thermal protection), photovoltaic devices (Projectors, power electronics), LED lighting, micro / nano electromechanical systems, biochips, and electric vehicles, etc., have great industrial applications. High-end applications determine the high standards of product quality, accuracy, and appearance. In order to meet such a large market demand, stricter requirements have been placed on the production method of metal thermal conductive sheets. Santech can follow the customer's requirements to produce metal thermal pad of different sizes and shapes, including rectangular, circular, triangular, and can customize metal thermal conductive sheets of different melting points to achieve customer use in different environments.

The production technology of metal thermal pad includes cutting, aluminum extrusion, metal powder jet forming and so on.A. cutting: turning, drilling, milling and grinding. In the forming process of thermal conductive sheet, cutting technology is required to obtain some special and fine shapes.The advantage is that according to different ways, cutting tools, can be applied to a variety of purposes.The disadvantage is the tool wear fast, most of the need for manual participation or automation control, high cost.Suitable for all heat conducting sheet: sheet (heat absorbing bottom, fin, etc.) forming, heat conducting sheet grooving, bottom dressing, special carving, etc.B. Aluminum extrusion: heat the original ingot of aluminum alloy to about 520~540℃, use mechanical pressure, make the aluminum liquid flow through the extrusion mold made of mold steel, cool the aluminum liquid at the outlet of the mold, make it solidified quickly, and become the first embryo of thermal conductive sheet with continuous parallel structure. Advantages are less investment, low technical threshold, short development cycle, easy to put into production; Mold cost, low production cost, large output; It can be used in a wide range of applications. It can be used to manufacture either individual heat sink or the fin part of the combined heat conductor. The disadvantage is that the fin shape is relatively simple and it is not possible to obtain a large (> 20) lane-to-length ratio. Suitable for heat sink processing, aluminum extrusion technology is mainly used to produce the initial blank of sheet fin or cylindrical fin. C. Metal powder jet forming: mainly using materials with high melting point and high heat conduction (such as copper). The metal powder is sprayed at high speed to make the first embryo of thermal conductive sheet directly, and then sintered at high temperature to make the finished product with considerable strength and density. The advantage lies in the metal powder sintering in one, high thermal conductivity; Heat conducting sheet with complex shape can be machined, the designer has less limitation. Disadvantages for raw materials, equipment, mold cost, complex process, low yield, not easy to mass production. It is mainly applied to electronic products with high calorific value and space limitation. The manufacturing cost and price are very high.

Metal thermal pad 's typical structure of the combination onto the fan is that a number of sheet heat conducting fins are engaged in a certain process on the heat-absorbing bottom with a certain thickness.Disadvantages: the airflow needs to change the direction in the thermal plate, which is easy to form a "no wind zone". Moreover, the overhead type of the traditional axial flow fan is easy to form a dead Angle -- "wind blind zone" -- in the part of the inter-bearing, but the thermal plate is in the center of the contact is the heating equipment (CPU core, etc.). A typical metal thermal pad design, with a solid copper column as the main shaft, radiates the thermal fin outward from the inside, and inversely bends the fin towards the fan to increase contact with the airflow. With this kind of design, the blind area of the axial flow fan just corresponds to the copper core of the thermal conductor, and the copper core itself has a small exposed surface area, which is difficult to improve the thermal conductivity with the aid of airflow. Meantime, some of the outer fins are just under the fan's strong wind, the thermal effect of nature excellent. Its design can be said to be an "evasive" approach: the wind blind area is avoided by clever design, minimizing the negative impact brought by it; And compared to the "conventional turbo" fan mentioned later, the copper core has a larger contact area with the thermal fins, which can better transfer heat to all parts of the fins.

CPUThermal conductivity of passive means without other auxiliary way of thermal conductivity of thermal conductivity, by conducting strip their contact with the chip, heat conduction take away heat gathering on the chip, but the present computer parts and components manufacturing more and more complex, the instant heat, only a passive thermal far cannot satisfy the needs of CPU heat conduction, so now we can only in the low calorific value control motherboard north and south bridge chip or some graphics display chip calorific value is not high to see this kind of way of thermal conductivity.Air cooling heat conduction is now the most common and the highest utilization of a heat conduction, belongs to the active heat conduction, this heat conduction can solve our usual heat conduction needs, the technology is mature and the price is moderate, so it is widely used in the market. The air-cooled heat conductor is simple in structure, cheap in price, safe and reliable. However, it also has some disadvantages, such as not being able to lower the temperature below room temperature, noise due to the rotation of the fan, and the improper installation of the fan will cause vibration, which will damage the computer components in the long run, and the fan life is also limited.Water cooling heat conduction is the use of water to replace air, through the movement of water in the heat between the heat convection to take away the excess heat.The water cooling system works simply by using pumps to pull water out of the water storage unit, which is then piped into a heat exchanger that covers the CPU. The water then comes out of another opening in the heat exchanger and flows back through the water pipe to the storage tank. The whole water cooling system includes heat exchanger, circulation system, water tank, water pump and so on. The thermal conductivity of the water-cooling system is very strong, which is very suitable for some overclocking enthusiasts. The principle of liquid cooling heat conduction is the same as that of water cooling heat conduction, and the heat conduction method adopted by them is the same. The difference is that the flow in the circulation system is thermal silicone oil instead of water, which has obvious benefits. It will not cause the computer hardware damage due to the damage of the circulation system to the silicon oil flowing out. At present the market for the sale of the aokma liquid cooling thermal conductivity belongs to this type of thermal conductivity. In addition to the above mentioned methods of active heat conduction, there are heat conduction of heat pipe, heat conduction of semiconductor refrigerator, heat conduction of compressor refrigeration, heat conduction of liquid nitrogen, etc.

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