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What Is Thermal Conductive Material? What Is The Different?

When it comes to cooling systems, most people think of fans and heat sinks, often ignoring one of the less visible but important mediators—the thermal conductive material. So, do you know the types of commonly used thermal conductive materials? What are their advantages and disadvantages? We together look!

Thermal gasket

Thermal gaskets are referred to as thermally conductive gaskets. They are used to fill the air gap between the heating element and the heat sink or metal base. Their flexible and elastic characteristics allow them to be used to cover very uneven surfaces. Heat is conducted from discrete components or the entire PCB to the metal enclosure or diffuser plate, increasing the efficiency and lifespan of heat-generating electronic components.
In the use of thermal pad, pressure and temperature are mutually restricted. With the increase of temperature, after the equipment runs for a period of time, the thermal pad material will soften, creep and stress relaxation, and the mechanical strength will also be reduced. down, the pressure of the seal decreases.

Advantage:

(1) Pre-formed thermally conductive material with ease of installation, testing, and reusability;
(2) Soft and elastic, good compressibility, able to cover very uneven surfaces;
(3) It has the effect of buffering, shock absorption and sound absorption under low pressure;
(4) Good thermal conductivity and high-grade withstand voltage insulation;
(5) Stable performance, no oil leakage at high temperature, and high cleanliness.

Shortcoming:

(1) The thickness and shape are preset, and the thickness and shape will be limited when used;
(2) The thickness of the thermal pad with a thickness of less than 0.3mm is complex, and the thermal resistance is relatively high;
Application environment: When the gap between the heat-generating component and the heat sink is large, the heat-generating component and the shell conduct heat.

Thermal Grease

Thermal grease, also known as thermal conductive grease, thermal paste, etc., is the most widely used thermal conductive medium at present. An ester-like substance formed after decompression, grinding and other processes, the substance has a certain viscosity and no obvious graininess. It can effectively fill various gaps.

advantage:

(1) Exist in liquid form with good wettability;
(2) Good thermal conductivity, high temperature resistance, aging resistance and waterproof properties;
(3) Insoluble in water, not easy to be oxidized;
(4) It has certain lubricity and electrical insulation;
(5) Low cost.

shortcoming:

(1) It cannot be smeared on a large area and cannot be reused;
(2) The product has poor long-term stability. After continuous thermal cycles, it will cause liquid migration, leaving only the filling material, and the surface wettability will be lost, which may eventually lead to failure;
(3) Due to the different thermal expansion rates of the materials on both sides of the interface, a “gas-filled” effect is caused, resulting in an increase in thermal resistance and a decrease in heat transfer efficiency;
(4) It is always liquid and difficult to control during processing, which is easy to cause pollution to other components and waste of materials, increasing costs.
Application environment: Between the high-power heating components and the radiator, the heat-dissipating components need to have their own fixing devices.

Thermal conductive double-sided adhesive

Thermal conductive double-sided tape is referred to as thermal tape, which is composed of acrylic polymer and silicone adhesive.

Advantage:

(1) It has both thermal conductivity and adhesive properties;
(2) It has good caulking performance;
(3) The appearance is similar to double-sided tape, and the operation is simple;
(4) Generally used for some electronic parts and chip surfaces with less heat generation.

Shortcoming:

(1) The thermal conductivity is relatively low, and the thermal conductivity is general;
(2) It is impossible to glue and fix heavy objects;
(3) Once the thickness of the tape is exceeded, effective heat transfer cannot be achieved with the heat sink;
(4) Once used, it is not easy to disassemble, there is a risk of damage to the chip and surrounding devices, and it is not easy to disassemble completely.
Application environment: It is usually used between a heat source with low power and a small heat sink to fix the LED heat sink, etc.

Thermal Gel

Thermal conductive gel is a gel-like thermal conductive material made of silica gel composite thermal conductive filler after stirring, mixing and potting. This material has some advantages of thermal pad and thermal grease at the same time, and better makes up for the weaknesses of both. Thermal gel inherits the advantages of good affinity, weather resistance, high and low temperature resistance, and good insulation properties of silicone materials. At the same time, it has strong plasticity and can meet the filling of uneven interfaces, and can meet the heat transfer requirements in various applications.

Advantage:

(1) Compared with the thermal conductive gasket, the thermal conductive gel is softer and has better surface affinity, and can be compressed to a very low thickness, which significantly improves the heat transfer efficiency, and can be compressed to 0.08mm;
(2) The thermal gel has almost no hardness, and will not cause internal stress to the equipment after use;
(3) The thermal conductive gel can be directly weighed and used. The commonly used continuous use method is the glue dispenser, which can realize fixed-point quantitative control, save labor and improve production efficiency.

Shortcoming:

(1) The cost is high;
(2) The process is more complicated.
Application environment: between high-power heating components and radiators, it can be used for quantitative control of dispensing machines.

Thermal silica glue ( RTV )

Thermal conductive glue, also known as thermally conductive silica gel, is made of organic silica gel as the main body, adding polymer materials such as fillers and thermally conductive materials, and kneading silica gel, which has good thermal conductivity and electrical insulation properties, and is widely used in electronic components.

Advantage:

(1) Thermal interface material, which will be cured, has adhesive properties and high adhesive strength;
(2) After curing, it is an elastic body, which is resistant to impact and vibration;
(3) The cured product has good thermal conductivity and heat dissipation function;
(4) Excellent high and low temperature resistance and electrical properties.

Shortcoming:

(1) Not reusable;
(2) The caulking gap is general;
(3) The curing time is longer.
Application environment: thermally conductive silica gel can be widely used in various electronic products, the contact surface between the heating body and the heat dissipation facilities in the electrical equipment, which acts as a heat transfer medium and has the properties of moisture, dust, corrosion and shock resistance.

Thermal potting compound

Thermal potting compound is commonly divided into silicone rubber system and epoxy system, silicone system is soft and elastic, and epoxy system is hard and rigid; it can meet the requirements of large depth of thermal conductivity potting. Improve the resistance to external vibration and improve the insulation and waterproof performance between internal components and circuits.

Advantage:

(1) It has a good waterproof sealing effect;
(2) Excellent electrical properties and insulation properties;
(3) It can be disassembled and repaired after curing.

Shortcoming:

(1) The heat conduction effect is general;
(4) The process is relatively complicated;
(5) poor bonding performance;
(6) The cleanliness is average.
Application environment: potting protection of power modules.

Thermally conductive silicone cloth

Thermally conductive silicone cloth is a silicone polymer elastomer reinforced with glass fiber cloth as a base material.

Advantage:

(1) It can effectively reduce the thermal resistance between the electronic components and the heat sink;
(2) Electrical insulation, with high dielectric strength, good thermal conductivity, and high chemical resistance;
(3) It can withstand circuit short circuit caused by high voltage and puncture of metal parts. It is an excellent thermal insulation material to replace traditional mica and silicone grease.

Shortcoming:

(1) The thermal conductivity is not high;
(2) The thickness and shape are preset, and the thickness and shape will be limited when used.
Application environment: filling between heat source and heat dissipation module or shell, insulation filling between live heating element and shell, etc.

Phase change material ( PCM )

Phase change materials refer to substances that change shape with temperature changes and can provide latent heat. The process of a phase change material from solid to liquid or from liquid to solid is called a phase change process.

Advantage:

(1) It can be repaired and reused, and the coating thickness and shape can be controlled as needed;
(2) It is solid at room temperature, but melts to fill the micro-gap during the operation of the equipment (no vertical flow);
(3) The thermal conductivity is equivalent to the traditional thermal grease, with better performance;
(4) Excellent substitute for silicone grease, there is no phenomenon of traditional silicone grease and silicone oil volatilizing, drying and aging.
(5) There is no glue overflow phenomenon of general silicone grease.
(6) Compared with thermal grease, there is no “inflatable” effect, and it has high reliability for long-term use;
(7) It can be dispensed, screen printed, and manually coated, and can be fully automated to greatly increase production;
(8) Environmentally friendly, in line with Rohs standards.

Shortcoming:

(1) It is not easy to store;
(2) Transportation, the cost is relatively high.
Application environment: on the cooling module.

Different thermal conductive materials have their own characteristics. No matter which thermal conductive material is used, there is no way to meet the heat dissipation needs of all electronic devices, and it has more or less some of its shortcomings. The advantages are magnified.

Thermal solution for EMS motor management system

Thermal Interface Materials Designed for Cooling Electronic Components

With the development of the new energy vehicle industry, new forces of new energy vehicle manufacturing continue to emerge, and automotive intelligence also develops rapidly, and technology companies have deployed automotive electronics.
As people have higher and higher requirements for driving comfort, safety, entertainment, economy and other performance, the number of electronic components in the car is also increasing, and the automotive electronic system is also complicated, which is bound to its safety and reliability. put forward higher requirements.

High temperature is an acceleration factor for the aging of electronic components. Poor heat dissipation design will seriously affect the reliability, safety, and durability of electronic components. Cars will also produce bad noise and vibration during driving, causing auto manufacturers to maintain product warranty maintenance. , vehicle quality satisfaction and other issues.

Cohetion series thermal conductivity products have mature thermal management material solutions in new energy vehicle battery pack, motor controller (MCU), body electronic control (ECU), vehicle charger, chassis control, vehicle entertainment and other systems, which can provide heat dissipation /Heat soaking/thermal conduction/thermal insulation and other series of product supporting solutions to help customers achieve the safety and reliability of automotive electronic products.

Thermal Solution for EMS Motor Management System

Compared with traditional industrial motors, new energy vehicle motors have higher requirements on power density, and the increase in power density will inevitably pose higher challenges to the heat dissipation design of the motor management system.

thermal pad

EMS (pure electric bus) rated voltage: 500V;
Rated power: 80kw~200kw;
Cooling method: water cooling

This cooling solution can use Cohetion thermal pad LC200R series between the motor controller and the radiator and combine with water cooling, which can effectively reduce the thermal resistance of the system, improve the power density of the system, and enhance the module’s ability to resist mechanical vibration and mechanical shock. Application requirements for long-term vibration of electric buses.

thermal sheet

LC200R series thermal pads are materials with high thermal conductivity, with breakdown voltage greater than 10Kv/mm, high tear strength, low thermal resistance under low pressure, self-adhesive and easy to operate.

How to use: Fill between the transformer on the power board and the aluminum die-casting shell to improve thermal conductivity.

Thermal solution for BMS battery management system

Thermally Conductive Interface Materials Designed for Cooling Electronic Components

Program overview

With the development of the new energy vehicle industry, new forces of new energy vehicle manufacturing continue to emerge, and automotive intelligence also develops rapidly, and technology companies have deployed automotive electronics.

As people have higher and higher requirements for driving comfort, safety, entertainment, economy and other performance, the number of electronic components in the car is also increasing, and the automotive electronic system is also complicated, which is bound to its safety and reliability. put forward higher requirements.

High temperature is an acceleration factor for the aging of electronic components. Poor heat dissipation design will seriously affect the reliability, safety, and durability of electronic components. Cars will also produce bad noise and vibration during driving, causing auto manufacturers to maintain product warranty maintenance. , vehicle quality satisfaction and other issues.

Cohetion series thermal conductivity products have mature thermal management material solutions in new energy vehicle battery pack, motor controller (MCU), body electronic control (ECU), vehicle charger, chassis control, vehicle entertainment and other systems, which can provide heat dissipation /Heat soaking/thermal conduction/thermal insulation and other series of product supporting solutions to help customers achieve the safety and reliability of automotive electronic products.

Thermal solution for BMS battery management system

BMS battery management system, commonly known as battery nanny, is mainly to ensure that the battery pack works within a safe range, provide information required for vehicle control, deal with abnormal situations in time, according to ambient temperature, battery status and online fault diagnosis, charging control, automatic balance, thermal management, etc.

BMS battery management system

BMS needs to perform a lot of calculations and signal control when it is working. As it develops in the direction of simplicity and miniaturization, heat must be generated inside it. In order to avoid affecting its normal operation, the heat must be transferred out. The thermal interface material is filled between the heat dissipation components to efficiently solve the problems of heat conduction, insulation and shock absorption.

BMS rated voltage: 5V~12V; heat dissipation method: aluminum shell heat dissipation

The heat dissipation scheme can use Cohetion thermal conductive silicone gasket LCP200 series. LCP200 is a super soft material with high thermal conductivity, which has low stress on the structure and plays the role of buffer protection. Thermal resistance, can cut different shapes according to customer needs, high and low temperature resistance, anti-oxidation, long-term use of product performance is stable and reliable.

thermal pad

How to use: Attach the electronic original pin corner surface on the back of the PCB;

Function 1: Conduct the heat of the electronic components to the shell to dissipate heat;

Function 2: The function of covering the pin surface to prevent leakage and piercing of the shell to protect the electronic originals.

EV Battery solution – Thermal interface material for cooling electronic components

EV Battrey Solution

NEW ENERGY VEHICLE SOLUTIONS

The importance of thermal management system

The heat-related issues of the battery are the key factors that determine its performance, safety, life and cost. First of all, the temperature level of lithium-ion batteries directly affects their energy and power performance in use. When the temperature is low, the available capacity of the battery will rapidly decay. Charging the battery at a too low temperature (such as below 0°C) may cause an instantaneous voltage overcharge phenomenon, which will cause internal lithium deposition and cause a short circuit.

Secondly, the heat-related issues of lithium-ion batteries directly affect the safety of the batteries. Defects in the manufacturing process or improper operation during use may cause partial overheating of the battery, which will cause a chain exothermic reaction, and eventually cause serious thermal runaway events such as smoke, fire or even explosion, which threatens the lives of vehicle drivers and passengers Safety.

In addition, the operating or storage temperature of lithium-ion batteries affects their service life. The suitable temperature of the battery is about 10~30°C, too high or too low temperature will cause the battery life to decay quickly. The large-scale power battery makes the ratio of its surface area to volume relatively reduced, the internal heat of the battery is not easy to dissipate, and it is more likely to have problems such as uneven internal temperature and excessive local temperature rise, which further accelerates battery degradation, shortens battery life, and increases users’total cost.

thermal insulation solution

The battery thermal management system is one of the key technologies to deal with battery heat-related issues and ensure the performance, safety and life of power batteries. The main functions of the thermal management system include: 

1) Effective heat dissipation when the battery temperature is high, to prevent thermal runaway accidents; 

2) Warm-up when the battery temperature is low, increase the battery temperature, and ensure the charging and discharging performance at low temperatures And safety; 

3) Reduce the temperature difference in the battery pack, inhibit the formation of local hot zones, prevent the battery from decaying too quickly at high temperature locations, and reduce the overall life of the battery pack.

Tesla Roadster thermal management system

THE THERMAL MANAGEMENT SYSTEM OF TESLA ROADSTER BATTERY

Tesla Motors’ Roadster pure electric vehicle uses a liquid-cooled battery thermal management system. The vehicle-mounted battery pack composed of 6831 18650-type lithium-ion batteries, of which 69 connected in parallel to form a set (brick), 9 sets connected in series to form a sheet, and finally 11 layers stacked in series. The cooling fluid of the battery thermal management system is a mixture of 50% water and 50% ethylene glycol.

Figure 1. (a) is the thermal management system inside the sheet. The cooling pipe arranged in a zigzag between the batteries, and the coolant flows inside the pipe to take away the heat generated by the battery. Figure 1. (b) is a schematic diagram of the structure of the cooling pipe. The inside of the cooling pipe divided into four channels, as shown in Figure 1.(c). In order to prevent the gradual increase in the temperature of the coolant during the flow of the coolant, the heat management system adopts a two-way flow field design, and the two ends of the cooling pipe are both the liquid inlet and the liquid outlet, as shown in the figure. As shown in 1(d). Fill between batteries and between batteries and pipes with materials with electrical insulation but good thermal conductivity . The functions are: 

1) Change the contact form between the battery and the heat dissipation pipe from line contact to surface contact; 

2) Yes It is beneficial to improve the temperature uniformity between the single cells; 

3) It is beneficial to increase the overall heat capacity of the battery pack, thereby reducing the overall average temperature.

Through the above thermal management system, the temperature difference of the individual cells in the roadster battery pack controlled within ±2°C. A report in June 2013 showed that after driving 100,000 miles, the capacity of the roadster battery pack can still maintained at 80%~85% of the initial capacity, and the capacity degradation is only obviously related to the mileage, but is related to the ambient temperature. The relationship between vehicle age is not obvious. The achievement of the above results depends on the strong support of the battery thermal management system.

thermal sheet

Heat dissipation principle of Tesla battery thermal management system

HEAT DISSIPATION PRINCIPLE OF TESLA BATTERY THERMAL MANAGEMENT SYSTEM

Cohetion technology’s thermal solutions ensure that your car battery performance is more stable, make your battery pack life cycle longer, and let your battery pack perform its best.

Heat dissipation principle: When the battery is working, a lot of heat generated. The heat is transferred to the water-cooled tube by the thermal sheet, and then the water-cooled tube transferred to the coolant. The liquid in the water-cooled tube flows in the battery pack to remove the heat.

Heat dissipation principle of battery thermal management system of a well-known domestic automobile manufacturer

The principle of Thermal dissipation: the use of a fan to actively dissipate heat, and the fan supplies the wind, and the wind blows toward the battery flow channel to heat the inside of the battery pack.

Heat dissipation principle: Because the temperature difference inside the battery pack is not controlled within 5°C, a thermal silicone sheet is attached to the upper and lower parts of the battery pack, and the silicone sheet guides the temperature to the outer aluminum shell. The temperature difference of the entire battery module controlled within 5°C. It meets the requirements of the battery pack design, which makes the battery pack longer life and more stable performance during driving.

thermal gel

Heat dissipation principle: The battery pack adopts passive heat dissipation. A thermal pad pasted between the battery pack and the aluminum heat sink. The silicone sheet transfers the temperature to the aluminum plate, and the aluminum plate exchanges heat with the air.

Heat dissipation principle: The battery pack adopts passive heat dissipation. A cooling pad pasted between the battery pack and the aluminum radiator. The silicone sheet transfers the temperature to the aluminum radiator, and the aluminum radiator exchanges heat with the air.

OBC Car Charger Thermal Solution

Thermally Conductive Interface Materials Designed for Cooling Electronic Components

With the development of the new energy vehicle industry, new forces of new energy vehicle manufacturing continue to emerge, and automotive intelligence also develops rapidly, and technology companies have deployed automotive electronics.

As people have higher and higher requirements for driving comfort, safety, entertainment, economy and other performance, the number of electronic components in the car is also increasing, and the automotive electronic system is also complicated, which is bound to its safety and reliability. put forward higher requirements.

High temperature is an acceleration factor for the aging of electronic components. Poor heat dissipation design will seriously affect the reliability, safety, and durability of electronic components. Cars will also produce bad noise and vibration during driving, causing auto manufacturers to maintain product warranty maintenance. , vehicle quality satisfaction and other issues.

Cohetion series thermal conduction products have mature thermal management material solutions in new energy vehicle battery pack, motor controller (MCU), body electronic control (ECU), vehicle charger, chassis control, vehicle entertainment and other systems, which can provide heat dissipation /Heat soaking/thermal conduction/thermal insulation and other series of product supporting solutions to help customers achieve the safety and reliability of automotive electronic products.

OBC Car Charger Thermal Solution

The on-board OBC is one of the important parts of the electric vehicle power system. Due to the high-power charging and discharging, huge heat is generated inside it. If it cannot be dissipated in time, the life and performance of the internal components will be greatly reduced. The electronic devices in the vehicle OBC are all encapsulated in the housing, and the heat source (electronic device/chip/MOSFET, etc.) needs to be in close contact with the inner wall of the housing to dissipate heat efficiently.

thermal conductive gel

OBC rated voltage: 220V; output power: 18kw; cooling method: air cooling

The heat dissipation scheme can use Cohetion thermal conductive gel LCF300 with a thermal conductivity of 3.0W/m·k, which can effectively fix small electronic components and prevent damage caused by bumps; fill between irregular heat sources (transformers, capacitors, etc.) and the radiator so that the heat can be well conducted to the radiator; fill the gap between the PCB board and the shell to protect the stability of the internal structure.

thermal conductive gel

At the same time, Cohetion thermal conductive gasket LCP200 can be used. The gasket is made of glass fiber cloth as a reinforcing material and processed by a special process. It is a very soft thermal conductive silicone gasket with excellent compressibility. The components are in close contact, with anti-puncture and anti-leakage functions.

thermal pad

How to use:

  1. Fix small electronic components to prevent damage caused by bumps, and conduct heat from components to the shell for heat dissipation
  2. Fill the gap between the irregular heat source (transformer, capacitor, etc.) and the radiator, so that the heat can be well conducted on the radiator
  3. Fill the gap between the PCB board and the shell to protect the stability of the internal structure.

Thermal solution for chassis control system

Thermally Conductive Interface Materials Designed for Cooling Electronic Components

With the development of the new energy vehicle industry, new forces of new energy vehicle manufacturing continue to emerge, and automotive intelligence also develops rapidly, and technology companies have deployed automotive electronics.

As people have higher and higher requirements for driving comfort, safety, entertainment, economy and other performance, the number of electronic components in the car is also increasing, and the automotive electronic system is also complicated, which is bound to its safety and reliability. put forward higher requirements.

High temperature is an acceleration factor for the aging of electronic components. Poor heat dissipation design will seriously affect the reliability, safety, and durability of electronic components. Cars will also produce bad noise and vibration during driving, causing auto manufacturers to maintain product warranty maintenance. , vehicle quality satisfaction and other issues.

Cohetion series thermal conduction products have mature thermal management material solutions in new energy vehicle battery pack, motor controller (MCU), body electronic control (ECU), vehicle charger, chassis control, vehicle entertainment and other systems, which can provide heat dissipation /Heat soaking/thermal conduction/thermal insulation and other series of product supporting solutions to help customers achieve the safety and reliability of automotive electronic products.

Thermal solution for chassis control system

With the rapid development of large-scale integrated circuit and microcomputer technology, in order to ensure the safety, power and handling stability of the vehicle, the vehicle chassis operating system has been given more important tasks. Take the new energy vehicle as an example, its chassis system needs to adapt to the diversity of vehicle energy sources, highly integrated system modules, and at the same time does not limit the design of the interior space and exterior shape of the vehicle, all of which put forward higher requirements for the thermal management of the chassis system. .

thermal pad

Rated voltage of chassis control system: 5V~12V; heat dissipation method: aluminum shell heat dissipation

The heat dissipation scheme can use the cohetion thermal pad LC300 series. LC300 has high resilience and good electrical insulation properties. It is a cost-effective thermal conductive gap filling material, which fully meets the filling and sealing between electronic components and aluminum die-casting shells. Thermal function.

thermal pad

How to use:

  1. Filling heat conduction between the transformer on the power board and the aluminum die-casting shell;
  2. Filling heat conduction between the diode and the copper heat sink on the power board.

Thermal solution for ECU body electronic control system

Thermally Conductive Interface Materials Designed for Cooling Electronic Components

With the development of the new energy vehicle industry, new forces of new energy vehicle manufacturing continue to emerge, and automotive intelligence also develops rapidly, and technology companies have deployed automotive electronics.

As people have higher and higher requirements for driving comfort, safety, entertainment, economy and other performance, the number of electronic components in the car is also increasing, and the automotive electronic system is also complicated, which is bound to its safety and reliability. put forward higher requirements.

High temperature is an acceleration factor for the aging of electronic components. Poor heat dissipation design will seriously affect the reliability, safety, and durability of electronic components. Cars will also produce bad noise and vibration during driving, causing auto manufacturers to maintain product warranty maintenance. , vehicle quality satisfaction and other issues.

Cohetion series thermal conductivity products have mature thermal management material solutions in new energy vehicle battery pack, motor controller (MCU), body electronic control (ECU), vehicle charger, chassis control, vehicle entertainment and other systems, which can provide heat dissipation /Heat soaking/thermal conduction/thermal insulation and other series of product supporting solutions to help customers achieve the safety and reliability of automotive electronic products.

Thermal solution for ECU body electronic control system

The ECU electronic control unit, also known as the car computer, is a special microcomputer controller for the car. ECU generally has fault self-diagnosis, protection function and adaptive program. With the increase in the degree of automobile intelligence, the functions of ECUs have become more and more complex, and the problem of heat dissipation has gradually become one of the bottlenecks in improving the performance of automobile ECUs. The ECU electronic control unit generally needs to be sealed, and it works in a high temperature environment for a long time, which puts forward higher requirements for the heat dissipation of the ECU circuit board.

ECU

ECU rated voltage: 5V~12V; heat dissipation method: aluminum shell heat dissipation

The heat dissipation solution can use Cohetion thermal conductive silicone gasket LC120 series. LC120 is a thermal conductive gasket developed for low compression force, low thermal resistance and high flexibility. It has double-sided self-adhesion and can be Stable work, meet the flame retardant grade requirements of UL94V0.

thermal pad

How to use:
1: Filling heat conduction between the transformer on the power board and the aluminum die-casting shell;

2: Filling heat conduction between the diode and the copper heat sink on the power board.

Does Thermal Pads Really Work

Many people will ask, does thermal pads really work, today CoolThermo will discuss with you, how does thermal pads work, does it really work?

Before discussing this issue, you have to think about why I use thermal pads. Yes, in order to improve the heat dissipation effect of the radiator and make the heat dissipate from the inside to the outside air faster, then the use of thermal pads can really achieve effect? The answer is yes. So why? Below I will list some data to give you a better understanding of this issue. We have an important criterion when choosing thermal pads, that is thermal conductivity. What is thermal conductivity? In short, thermal conductivity is an indicator of heat transfer efficiency. The unit is W/MK. Indicates that the thermal conductivity is better, and vice versa, the thermal conductivity of the commonly used high thermal conductivity gaskets on the market is 3W/MK, but many companies will choose higher ones, such as 6W/MK, 8W/MK, but correspondingly, The price will also be higher, so what do thermal pads do? Its function is to fill the gap between the heating component and the heat sink, so it is also called thermal gap filler. Its function is to replace the air between the heat sink and the heating component (air is a bad conductor of heat, only 0.023W /MK, very low), so that the heat is transferred to the radiator faster through it, so as to achieve the effect of cooling. Through my simple analysis, I believe you have found the answer. If you have any questions, you can leave me a message at any time, or send me an email, and I will reply as soon as possible.

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.

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