Tag thermal conductive materials

What Is Thermal Conductivity?

Whether it is the new energy automobile industry, electronic electrician, or LED industry, the application of thermal conductive materials is relatively common. In thermal management, thermal conductivity is an important parameter reflecting the thermal conductivity of materials, and it is also the most concerned technical indicator for users.

Thermal conductivity is a physical quantity that characterizes the thermal conductivity of a material. Its definition means that under stable heat transfer conditions, a 1m thick material has a temperature difference of 1 degree (K, ℃) on both sides of the material, within 1 second (1s), through the heat transferred by the area of 1 square meter, the unit is watt/meter·degree (W/(m·K), where K can be replaced by °C). ( Fourier’s law : The heat flux density at each point in a homogeneous material body is proportional to the temperature gradient. The direction of heat transfer is from high temperature to low temperature and the direction of temperature gradient is opposite from low temperature to high temperature. )

The thermal conductivity of a material is not only related to the material type of the material, but also closely related to its microstructure and filler content. In scientific experiments and engineering design, the thermal conductivity of the materials used needs to be accurately determined by experimental methods. There are many methods for measuring thermal conductivity, and they have different application fields, measurement ranges, precision, accuracy and sample size requirements. Different methods may have large differences in the measurement results of the same sample. , so choosing the appropriate test method is the first and foremost.

At present, the measurement methods of thermal conductivity are divided into two categories: steady-state method and non-steady-state method, with different test principles. In the thermal conductive silicone industry, the common test method is the steady-state hot plate method (reference standard: ASTM D5470)

Standard Test Method for Heat Transport Properties of Thin Thermal Conductive Solid Electrical Insulating Materials: ASTM D5470

This method uses the so-called steady-state heat flow method. The test principle is to place a sample of a certain thickness between the upper and lower plates, apply a certain heat flow and pressure to the sample, and use a heat flow sensor to measure the heat flow through the sample, Test the thickness of the sample and the temperature gradient between the hot plate and the cold plate, and then obtain the corresponding thermal resistance data under different thicknesses and fit a straight line to obtain the thermal conductivity of the sample.

The advantages of this approach are:

  1. It can test the thermal resistance and thermal conductivity of the product;
  2. It is especially suitable for simulating the use state of the product under actual working conditions.

Weakness is:

  1. There are certain requirements for the thickness of the product;
  2. Contact thermal resistance will affect the test results;
  3. In order to reach a steady state, the test takes a long time.

Thermal conductivity is a parameter of the material itself and has nothing to do with shape or size. At present, there are a large number of thermal conductivity test methods, but no one method can be applied to all products and all occasions. Product characteristics, test standards, test environments, etc. will all affect the results of thermal conductivity. The thermal conductivity of materials cannot be compared using data obtained from different test methods. To get accurate and informative results, it is necessary to select a suitable test method for measurement.

What Is Thermal Silicone Pad?

In the field of intelligent manufacturing, electronic instruments and meters such as transistors, automotive electronic components, power modules, printer heads, etc., need to pay special attention to the problem of heat conduction and heat dissipation during use, and thermal conductive silicone pad can solve this problem. So what is a thermal silicone pad? What are the characteristics of silicone thermal pad? Where is the thermal pad used? Let’s take a look together!

Definition of Thermal Silicone Pad

Thermal Silicone Pad is a kind of thermally conductive medium material synthesized by a special process by adding organic silica gel as the base material and adding various auxiliary materials such as metal oxides; in the industry, it is also known as thermal conductive silicone pad, thermal conductive silicone sheet, thermal conductive pad , thermal conductive silicone gaskets, etc., are specially produced for the design scheme of using gaps to transfer heat. They can fill gaps, open up the heat channel between the heat-generating part and the heat-dissipating part, effectively improve the heat transfer efficiency, and also play a role in insulation and shock absorption. , sealing and other functions, can meet the design requirements of equipment miniaturization and ultra-thin, it is extremely manufacturable and practical, and has a wide range of thicknesses, an excellent thermal conductive filling material.

Advantages of Thermal Silicone Pad

  1. The material is soft, the compression performance is good, the thermal conductivity and insulation performance are good, and the thickness can be adjusted in a relatively large range, suitable for filling the cavity, with natural viscosity on both sides, and strong operability and maintainability;
  2. The main purpose of selecting the thermal interface material is to reduce the contact thermal resistance between the surface of the heat source and the contact surface of the heat sink, and the thermally conductive silicone pad can fill the gap between the contact surfaces well;
  3. Since air is a poor conductor of heat, it will seriously hinder the transfer of heat between the contact surfaces, and installing a thermal silicone sheet between the heat source and the radiator can squeeze the air out of the contact surface;
  4. With the addition of thermal conductive silica gel pad, the contact surface between the heat source and the radiator can be better and fully contacted, so as to truly achieve face-to-face contact. The reaction at temperature can reach as small a temperature difference as possible;
  5. The thermal conductivity of the thermal gap filler is adjustable, and the thermal conductivity is better;
  6. The structural process difference of the thermal pad is bridged to reduce the process tolerance requirements of the radiator and heat dissipation structural parts;
  7. The thermal pad has insulating properties (this feature needs to be added with appropriate materials during production);
  8. The thermal silicone pad has the effect of shock absorption and sound absorption;
  9. The thermal silica pad has the convenience of installation, testing and reusability.

Disadvantages of Thermal Silicone Pad

Compared with thermal grease, thermal pad has the following disadvantages:

  1. Although the thermal conductivity is higher than that of thermal grease, the thermal resistance is also higher than that of silica thermal pad.
  2. The thermal silicone pad with a thickness of less than 0.5mm has a complex process and relatively high thermal resistance;
  3. The thermal grease has a larger temperature resistance range. They are thermal grease -60°C to 300°C, thermal silicone pad -50°C to 220°C;
  4. Price: Thermal grease has been widely used, and the price is relatively low. Thermal silicone pads are mostly used in thin, small and precise electronic products such as notebook computers, and the price is slightly higher.

Thermal Silicone Pad Application

  1. TFT-LCD notebook computer, computer host.
  2. High-power LED lighting, high-power LED spotlights, street lamps, fluorescent lamps, etc.
  3. Power devices (power supply, computer, telecommunications), automotive electronic modules (engine wiper) power modules, high-power power supplies, calculator applications (CPU, GPU, USICS, hard drives) and any place that needs to be filled with heat dissipation .
  4. Close contact between heating power devices (integrated circuits, power tubes, thyristors, transformers, etc.) used in electronic products and electronic equipment and heat dissipation facilities (heat sinks, aluminum casings, etc.) to achieve better thermal conductivity . Thermally conductive silicone insulating sheet.
  5. Thermal silicone pad is used for control motherboards of electronic and electrical products, inner and outer pads and foot pads of motors, electronic appliances, automotive machinery, computer mainframes, notebook computers, DVD, VCD and any materials that need to be filled and heat dissipation modules .

How To Test Whether The Thermal Pad Is Resistant To High Temperature

Thermal pad is often used in the thermal conduction and heat dissipation application scheme of electronic products. It has good thermal conductivity, and can maintain good stability under high temperature, acid and alkali conditions, high and low temperature resistance, and the operating temperature range is -50~200 ℃; then, how to test whether the thermal silicone pad really has high temperature resistance?

The commonly used method to test whether the thermal pad is resistant to high temperature is a simple aging test. The important goal of this test is to see how the silicon molecule volatilizes the thermal conductive silicone pad at high temperature. The specific methods are as follows:

  1. Select 10 samples and place them in a drying oven at 35 ℃ for 80–100h
  2. Put the sample into the oven at 200℃ and dry it continuously for 200h
  3. Take out the sample and place it in a drying oven at 35 ℃ for 80–100h
  4. Accurately weigh the weight G1 of 10 samples respectively
  5. Accurately weigh the weight G2 of the 10 samples again
  6. Calculate weight loss: (G1-G2)/G1×100%

Judgments based:

  1. The weight loss is less than 1%;
  2. All chemical and physical properties are stable after high temperature.

Through the above test steps, you can probably judge the high temperature resistance of a thermal pad, and provide more reference for choosing a suitable thermal silicone pad.

Does Thermal Resistance Have An Effect On Thermal Conductive Materials?

The heating of electrical equipment is a phenomenon that people often come into contact with in life and work. If the internal temperature of the equipment is not effectively controlled, equipment failure or even circuit short circuit may occur due to excessive temperature. So what is the heating of electrical equipment?

Electrical equipment is a kind of mechanical equipment that converts electrical energy into other energies. During operation, electrical energy will flow through the equipment, but when electrical energy is converted into other energies, complete conversion cannot be achieved, and some energy will be lost, and a large part of this energy will be lost. It is lost in the form of heat, which is one of the reasons why the electrical equipment will heat up when it is running.

Thermally conductive material is one of the materials specially designed to solve the problem of heat dissipation in the field of thermal management. In the past, people would install heat sinks on the surface of power-consuming electronic components, but the heat dissipation effect was very low and the temperature could not be effectively controlled. In the gap, no matter how smooth the surfaces of the two are, there is still a gap at the interface, and there is hot bad conductor air in the gap, so the heat conduction effect is very poor. At this time, it is necessary to fill the gap with a thermally conductive material, so that the two can be in close contact and eliminate the interface. Air to improve heat transfer, thereby improving heat dissipation.

There is a saying in the thermal conductivity material industry: purchasing depends on thermal conductivity, while engineering depends on thermal resistance. It is well known that thermal conductivity is the main point among the many parameters of thermally conductive materials. It is the standard for measuring the thermal conductivity of thermally conductive materials. However, for engineers, they often pay attention to thermal resistance. Does thermal resistance affect thermally conductive materials? The answer is yes.

In professional academic analysis, thermal resistance is the temperature difference formed at both ends of the object when the heat flow passes through the object. The thermal resistance reaction in the thermal conductive material is to guide the ability of the thermal material to hinder heat conduction. The greater the thermal resistance of the thermal conductive material, the stronger the ability to hinder the thermal conduction. The two sides of the surface are the starting point and the ending point. When the heat enters the thermal conductive material through the surface, it begins to conduct to the other side. The thermal resistance is the railing on the track, which hinders the transfer of heat. The greater the thermal resistance, the harder it is for heat to pass. Pass it to the other side, which is also the essence of thermal resistance.

Some people think that the higher the thermal conductivity of a thermally conductive material, the lower the thermal resistance. In fact, this is not true. The thermal resistance does not necessarily depend on the high or low thermal conductivity, but one thing can be said. For a thermally conductive material with the same other parameters except the resistance value, the thermally conductive material with a small thermal resistance value has a better thermal conductivity effect, whereas a thermally conductive material with a large thermal resistance value has a poor thermal conductivity effect.

When people buy or purchase thermally conductive materials, in addition to knowing their thermal conductivity, size and thickness, compressibility, and hardness, thermal resistance should also be paid attention to. After all, it is one of the key factors affecting the thermal conductivity of thermally conductive materials.

Why Is The Thermal Silicone Pad Oily?

The application of electrical and electronic equipment enriches people’s daily life and improves work efficiency. When the equipment is running, heat is often emitted, because part of the energy is lost when electrical energy is converted into other energy, and a large part of the energy will be heat. It is emitted in the form of heat, so manufacturers will use thermally conductive materials to assist the device to dissipate heat.

As one of the traditional thermal interface materials on the market, thermal silicone pads are widely used in industrial production. Thermally conductive silicone pads are made of silicone resin as the base material, and thermally conductive and heat-dissipating materials are added to make thermally conductive gap filling materials, generally in the form of solid sheets. The size and shape can be customized according to customer needs. Due to its good softness, it can effectively remove the air at the interface and has good contact. The surface of the device or shell can reduce the interface thermal resistance and improve the thermal conductivity.

Anyone who has used the thermal silicone pad will find that the thermal silicone pad will be oily after being used for a long time, so why does the thermal silicone pad, which is a solid sheet, have such a situation? Next, CoolThermo will explain to you.

It is normal for the thermally conductive silicone pad to emit oil, because most of the production process of the thermally conductive silicone pad is to mix silicone oil with heat-conducting, heat-resistant, and insulating materials in a certain proportion, and refining it through a specific machine, and the finished product is not much. There will be few small molecules that are free and not completely mixed. In a long-term heat and pressure environment, small siloxane molecules will slowly precipitate out. This is the reason why the thermally conductive silicone pad emits oil and why It is normal to say that the thermal conductive silicone pad is oily.

The oil output rate of the thermal silicone pad is an important factor affecting the reliability of electronic products. Although it is normal for the thermal silicone pad to emit oil, the thermal silicone pad is used as a thermal interface material to fill the gap between the heating element and the radiator. The direct contact between the two causes the siloxane small molecules to be adsorbed on the surfaces of the two after precipitation, which affects the performance and safety of electronic components, and causes pollution to the equipment.

Of course, it is not that the thermal conductive silicone pad has silicone oil precipitation and do not use it. The oil yield of the thermally conductive silicone sheet produced by the domestic big-brand thermal conductive silicone sheet manufacturers will be controlled within the qualified range, so when purchasing the thermally conductive silicone sheet, you should choose a well-known domestic Manufacturers of thermally conductive silicone sheets, especially recommend those high-quality manufacturers with their own R&D, production and quality departments.

How To Choose/Buy Thermal Silicone Pad

During the operation of any electronic device, a large amount of heat energy will be generated, and these will cause damage to many parts in the device. Therefore, in most electronic devices with different functions, a large number of thermal silicone pad with good market reputation will be used. Although the silicone thermal pad can indeed play a very good role, it must be under the premise of choosing the right thermal gap filler. So, what factors should be considered when choosing a thermal silicone pad? CoolThermo analyzes the selection criteria of thermal interface material for you.

Hardness

The thermal silicone pads is an accessory used between the parts in the electronic equipment. Its main function is to have a thermal conductivity effect as its name. However, because of the operation between the parts, a friction will be formed, and if the hardness of the thermal pads If it is too low, there will be hidden dangers, so the silicone thermal pads used in this position should pay more attention to whether its own hardness is more suitable, which is the guarantee to ensure that it plays a better role.

Viscosity

A good-quality thermally conductive silicone pad not only has good compressibility, thickness and hardness, but also must have good viscosity. This is because ordinary thermal insulation pads need to be glued on the outside during the production process. However, this method will cause the thermal resistance of this type of thermal interface material to increase, so that it cannot effectively isolate heat energy. Therefore, when choosing this type of thermally conductive product, you should pay attention to the viscosity of the thermal interface pad, because good thermally conductive silicone The stickiness of the sheet material itself will reach a higher standard.

Color

In fact, the color of the thermal conductive pad also has an impact on its own thermal conductivity. For example, the darker the color, the better the heat absorption capacity. Such a thermal silicone pad is very suitable for use in equipment that needs to reduce the temperature, while other shallow Colored thermal conductive pad are more suitable for thermal insulation devices, so when choosing a thermal gap filler pad, you should pay attention to its own color to choose.

Although the thermal silicone pad is a seemingly simple material with little technical content, in fact, the role of this gasket is obviously more important than what people know, so learning and understanding how to correctly select the thermal gasket pay attention to its true hardness, pay attention to its own stickiness, and pay attention to three-way matters such as choosing the right one from many colors.

How To Calculate Thermal Conductivity

Thermal conductivity refers to the heat transfer through 1 square meter area in 1 second for a 1m thick material with a temperature difference of 1 degree (K, ℃) on both sides of the material under stable heat transfer conditions, the unit is watts /m.degree (W/m.K, where K can also be replaced by °C). It is a physical quantity that expresses the thermal conductivity of a material, and uses Fourier’s law as the formula for calculating its thermal conductivity.

The thermal conductivity of materials varies with composition, physical structure, state of matter, temperature, pressure, etc. The thermal conductivity of different components varies greatly, resulting in a large difference in thermal conductivity of materials composed of different components. Air is a poor conductor of heat, and the thermal conductivity of single-grain materials is better than that of stacked materials.

In addition, in general the thermal conductivity we defined above is for homogeneous materials. In practice, there are porous, multi-layer, multi-structure, and anisotropic materials. The thermal conductivity obtained by this material is actually a performance of comprehensive thermal conductivity, also known as the average thermal conductivity.

Fourier’s law is a basic law in heat transfer, which can be used to calculate the amount of heat conduction (Fourier’s law of heat conduction).

So, what is the formula for calculating thermal conductivity?

According to Fourier’s law of thermal conductivity, the relevant thermal conductivity calculation formula is expressed as follows:

Φ=-λA(dt/dx)

q=-λ(dt/dx)

Where Φ is the thermal conductivity, the unit is W

λ: thermal conductivity

A: Heat transfer area, the unit is ㎡

t: temperature, in K

x: the coordinate on the heat conduction surface, the unit is m

q: The heat flux density transferred along the x direction (strictly speaking, the heat flux density is a vector, so q should be the component of the heat flux density vector in the x direction) in W/㎡

dt/dx: the rate of temperature change of the object along the x direction

Mathematical expression in general form: q=-λgradt=-λ(dt/dx)n

In the formula: gradt refers to the temperature gradient of a certain point in space; n refers to the normal unit vector on the isotherm passing through the point, which refers to the direction of temperature increase.

The negative sign in the above formula indicates that the direction of heat transfer is opposite to the direction of the temperature gradient

λ is a physical parameter that characterizes the thermal conductivity of the material (the larger the λ, the better the thermal conductivity).

Usually, the thermal conductivity of materials in daily experiments cannot be obtained simply by using the thermal conductivity calculation formula, and the combination of theory and experiment is an important source of thermal conductivity data.

Why Do Thermal Silicone Pad Have Bubbles? How To Deal With It?

Many thermal silicone pad manufacturers will inevitably encounter problems of one kind or another in the process of producing thermal silicone pad. One of the problems that plagues thermal silicone pad manufacturers is that the thermal silicone pad foams during the production process. Once the thermal silicone pad foams, it will be regarded as a defective product and thrown away without recycling or any other value, which directly increases the defect rate to the thermal silicone pad manufacturer and causes cost pressure. Then, Nuofeng Electronics analyzes the reasons and solutions for the foaming of thermal silicone pad.

There are many reasons for blistering in the production process of thermal silicone pad, which are mainly as follows:

  1. The vulcanization temperature is too low: the vulcanization temperature is an important parameter affecting the molding of silicone rubber. Usually the thermal silicone pads is set at 160~200℃, but sometimes the mold is too long due to the long operation time of the mold or other reasons. The temperature of the silicone molding mold is low, and there is a temperature difference with the vulcanization temperature of the silicone, which will cause the silicone product to foam after molding. In this regard, we only need to increase the molding temperature, or open the empty mold into the machine for a period of time and then operate to solve the problem.
  2. The vulcanization temperature is too high: The first point is that the vulcanization temperature is too low, which will cause the thermal conductive silicone to foam. In fact, in many cases, the molding temperature is too high. Why? When the molding temperature is too high, the silica gel material on the surface has already begun to be formed during the mold clamping and pressurization process. At this time, the air has been trapped inside and it is difficult to discharge, so it will cause molding bubbles. For this reason, it is only necessary to appropriately lower the molding temperature.
  3. Insufficient exhaust: After the silicone raw material is placed in the forming mold, a lot of air will be brought in at the moment of closing the mold, and it is impossible for the air to be integrated with the thermal conductive silicone material. If the air is not discharged, it will cause After the silicone is molded, air bubbles are formed on the surface.
  4. The structure of the mold is unreasonable: the unreasonable design of the silicone molding mold will also cause bubbles in the molding of thermally conductive silicone. For example, the arrangement of the products in the mold, the partition method, the mold parting method, and the design of the mold size will cause poor foaming. , but the cost of opening a set of molds is very high, and it is not easy to modify. If the silicone molding foams due to the structure of the mold, it is usually solved from the points mentioned above.
  1. The vulcanization time is too short: Like the vulcanization temperature, the vulcanization time is also one of the important parameters affecting the molding of the thermally conductive silica gel. The length of the vulcanization time determines whether the thermally conductive silica gel can be completely vulcanized. If the curing time is too short, it will not only cause the silicone to become soft after molding, but also more likely to cause surface bubbles. If such defects occur, the curing time of silica gel can be appropriately extended.
  2. The production process is also very important: the anti-aging agent RD is easy to produce bubbles during the mixing operation of the open mill, which is mainly due to the high melting point of the anti-aging agent RD and the low operating temperature of the open mill. Special attention should be paid to the dispersion of zinc oxide during refining, and the uniformity of its dispersion will also cause the generation of small bubbles, so the silicone rubber mixing process is also a very important part.
  3. Whether the moisture content of the raw materials used in the formula, the mixing operation and the extruded water vapor of the products, and whether the drying is sufficient after cooling, will also cause bubbles in the molding of the thermally conductive silica gel, which is mainly caused by the evaporation of water during vulcanization.

After the thermal silicone pad is foamed and then attached to the heat source to dissipate heat, it will not only affect the effective contact area of ​​the thermal silicone pad, but also air will enter the bubbles, thereby increasing the thermal resistance. The size of the effective contact area and the size of the thermal resistance are the two main performance parameters to judge the thermal conductivity of a thermal silicone pad except for the thermal conductivity. Therefore, the thermal silicone pad should not be shipped after foaming and must be classified as Defective products.

Thermal Interface Materials Apply in LED Lighting

Design challenges encountered in high-power LED lighting solutions are thermal design and thermal protection. A power and thermal management system is required for LED light sources because most of the electrical energy supplied to LEDs is converted to heat compared to other light sources. Without proper thermal management, this heat will affect the LED life and color output. Solving the heat dissipation problem of LED lighting fixtures is an indispensable link in the lighting design.

The thermally conductive materials commonly used in LED lighting fixtures are mainly divided into: structural thermally conductive materials and filling thermally conductive materials according to their functions in the lamps.

In addition to the function of the shell of the lamp, the structural thermal interface material is also used for the heat dissipation of the LED light source, such as thermal conductive plastics. The complementary thermal interface material is mainly used between the heating element and the heat dissipation element, as the connection between the two is used for heat conduction. Since the thermal conductivity of the thermal interface material relative to the heating element and the metal heat sink is low, the choice of the thermal interface material is also very important. Crucially, this determines how fast the heat is transferred.

The following are several thermal interface materials for high-power LED solutions:

Thermal grease: It has the characteristics of excellent thermal conductivity, electrical insulation, use stability, high and low temperature resistance, etc. It is a commonly used thermal conductive material for high-power LED lighting;

Thermal silicone pad: fill the air gap between the heating device and the heat sink or metal base to achieve heat transfer between the heating part and the heat dissipation part, and also play the role of insulation and shock absorption, which can meet the requirements of miniaturization and ultra-thin Design requirements, the ease of use is unmatched by thermal grease;

Thermal adhesive tape: Bonding between the heating sheet and the heat sink is simple and convenient to use, which is beneficial to improve production efficiency.

Potting compound: a room temperature curing one-component silicone adhesive sealant, non-corrosive to most metals; has excellent resistance to cold and heat alternating performance, aging resistance and electrical insulation performance, excellent moisture resistance, Shock resistance, corona resistance, anti-leakage performance.

At present, thermally conductive materials such as thermal conductive grease, thermal pads, thermal double-sided adhesive tape, and potting compound have been widely used in LED lighting solutions; CoolThermo, as a thermally conductive material manufacturer, is committed to providing customers with comprehensive solutions for LED lighting. , to meet customer one-stop purchasing needs.

What Is The Hardness of Thermal Silicone Pad? How to Test And Select Hardness of Themral Pad?

With the advent of the 5G era, thermal silicone pads are increasingly favored by the electronics manufacturing industry. The main reason is that thermal silicone pads are widely used, such as filling cooling devices, communication hardware, new energy vehicle control units, and drones. , base station, LED lighting, LCD display, medical beauty equipment, etc.; in these applications, the thermal silicone pad will produce a certain compression to bridge the gap to achieve good thermal conductivity.

When choosing a thermal silicone pads, you cannot just look at thermal conductivity, blocking voltage, thickness, density, and hardness is also very important; when choosing a thermal silicone pad, you must first consider the product structure, such as shape, specification, breakdown, temperature resistance range, thickness, density, thermal conductivity We all know that the thermal conductivity of a thermal silicone pad is an important indicator to measure its performance, and its hardness also affects the performance of the thermal silicone pad; many people have doubts about the hardness of the thermal silicone pad when choosing, so CoolThermo came to Analyze the hardness of the thermal silicone pads.

First of all, what is the concept of hardness?
Hardness, a technical term in physics, the ability of a material to locally resist the pressing of a hard object into its surface is called hardness. The local resistance of a solid to the intrusion of foreign objects is an indicator for comparing the softness and hardness of various materials. Hardness is used to characterize the degree of softness and hardness of a material, which refers to the ability of a material to resist local deformation, especially plastic deformation, indentation or scratching.

So, what is the hardness of the thermal silicone pad?

One advantage of high-quality silicone thermal pad is that the material is usually soft, and the softness precisely refers to the hardness of the silicone thermal pad. Its hardness directly reflects the soft and hard compressibility of the silicone thermal pad. A very important parameter in the physical properties of silicone thermal pads.

Thermal Silicone Sheet Hardness Test Standard

Since different test methods are specified, there are different hardness standards. The mechanical meanings of various hardness standards are different and cannot be directly converted to each other, but can be compared through tests. Common hardness is classified according to the test method: scratch hardness, indentation hardness, callback hardness. According to the specific hardness names, there are: Rockwell hardness, Brinell hardness, Leeb hardness, Shore hardness, etc.

According to the standard ASTM D2240 “Standard Test Method for Testing Rubber Hardness with Durometer”, the thermal silicone sheet uses Shore hardness to express its hardness. The corresponding measuring instrument for Shore hardness is the Shore hardness tester, which is mainly divided into three categories: A type, C type and 00 type. The measurement principle is exactly the same, the difference is the size of the stylus, especially the diameter of the tip, the 00 type is the largest, and the A type is the smallest. The Shore A durometer is suitable for measuring hard thermal pads; the Shore 00 durometer is suitable for measuring soft thermal pads.

Shore hardness belongs to indentation hardness. The test method is to insert a Shore hardness tester into the material to be tested. The pointer on the dial is connected to a needle through a spring, and the needle is used to pierce the surface of the tested object. The value displayed on the dial is the hardness. value.

Is the hardness of the thermal silicone pads good or low?

The lower the hardness of the thermal silicone pads, the softer the product and the higher the compression rate, which is suitable for use in low-stress environments. Conversely, the higher the hardness of the thermal pad, the harder the product and the lower the compression rate. Under the same application conditions, products with low hardness have higher compressibility, shorter heat conduction paths, shorter heat transfer time, and better heat conduction effect than products with high hardness.

However, it is not that the lower the hardness, the better. The thermal conductive gasket has a certain hardness so that it is not easy to deform. Generally speaking, thermally conductive gaskets with higher hardness have better mechanical properties. In the application, it is necessary to comprehensively consider the actual situation to select a thermally conductive gasket with appropriate hardness.

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