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 the reason for the wide application of thermal silicone pad?

High thermal silicone gasket is a new product derived from the progress in the heat dissipation adhesive market. It is mainly based on silica gel, and various auxiliary materials such as metal oxides are added. A thermal conductive medium material synthesized by a special process , used to reduce the contact thermal resistance between the surface of the heat source and the contact surface of the heat sink. It is specially produced for the design scheme of using the gap to transfer heat, completes the heat transfer between the heat-generating part and the heat-dissipating part, and is an excellent thermal conductive filling material.

Things made of silicone are still very popular with the public. After all, they are relatively environmentally friendly, they are very convenient to use, and the price is particularly suitable. Therefore, thermal silicone pads are widely used in various industries; then, thermal silicone pads are widely used. What’s the reason? Today, CoolThermo will introduce the application principle of high thermal silicone gaskets to you.

Excellent thermal conductivity

You must know that the thermal pads is still relatively soft, and can be used as a filling pad in many electronic precision mechanical product cooling modules. It is precisely because of its softness that it is more convenient to use. In addition, because silica gel is an important raw material, silica gel has good thermal conductivity and strong elongation performance, so it will gradually expand after being applied to the gaps of some small parts, and the gaps will be filled continuously, and naturally it will not be lost. more heat, so that the heat can be well conducted.

Good insulating properties

Since it is used in electronic precision mechanical products, the performance requirements for the materials used are still relatively strict, and insulation is of course essential. Many electronic products need to use some thermal pads, only in this way can the mechanical fixation be done well, but at the same time, the insulating properties of the thermal pads must be considered, so that they will not appear during use. Leakage situation, otherwise it is really quite dangerous. At this time, silica gel, which has insulating properties itself, can show its talents. Because of its insulating properties, it can be processed into a thermally conductive silica gel sheet and can be directly applied to the connection between the heat source of the product and the heat sink.

Low price

Not all products that sound high-end are expensive. Some things just look novel. In fact, the price is still acceptable to the public. Silicone is a living example. The cost of thermal pads made from it is still very low. The extremely thin sheet is very material-saving, so the input cost is also greatly reduced, and its price will gradually decrease. Many people value this advantage and use it in product cooling solutions!

Environmental safety

Nowadays, the public use items still pay great attention to safety and environmental protection. Most of the thermal pad is made of silicone. In addition to adding some environmentally friendly glue, the thermal silicone pads does not need to add too many other ingredients. Therefore, it is still very environmentally friendly and safety

It is worth mentioning that the main purpose of choosing high thermal conductivity silicone gasket is to reduce the contact thermal resistance between the surface of the heat source and the contact surface of the heat sink. The high thermal silicone gasket can also fill the gap of the contact surface well and squeeze the air out of the contact surface. Air is a poor conductor of heat, which will seriously hinder the transfer of heat between the contact surfaces; with the addition of thermal pads, the temperature response can reach as small a temperature difference as possible, which can make the contact surfaces better and fully contact, truly Make face-to-face contact.

With the development of science and technology, thermally conductive silicone gaskets have been widely used in communication equipment, computers, switching power supplies, flat-panel TVs, mobile equipment, video equipment, network products, medical equipment, household appliances, PC servers, workstations, optical drives, COMBO, Base stations and other fields. In the future, more industry applications are waiting for thermal pads manufacturers to explore and discover.

What is a thermal pad with glass fiber?

Case analysis

Recently, a thermal conductive silicone pad cooling solution was provided to a customer who made a motor. Because the product is too thin, the thickness is only 0.5mm, and the thermal conductivity is high, which makes the product toughness and poor tensile strength. The thermally conductive silicone pad is applied to the motor, and it is in a continuous vibration environment, so there are certain requirements for the tensile resistance and wear resistance of the product. The sample showed multiple cracks and wear during the test, and the customer had concerns about the thermal pads.

In response to this situation, we explained to the customer that there is no problem with the thermal conductive gasket itself, and the problem is not difficult to solve, that is, adding glass fiber cloth to the original thermal silicone pads, adding a layer of glass fiber reinforcement to the thermal silicone pads. Yes; from the point of view of thermal conductivity, we recommend glass fiber with a thickness of 0.03mm, the tensile strength is not less than 100psi, and the tensile strength is enhanced while ensuring thermal conductivity to the greatest extent. But the thermal conductivity can not be reduced by adding glass fiber, it can be done for us, but the cost is slightly increased. We quickly produced samples and did a tensile strength test. The tensile strength was 112psi, which fully met the customer’s application requirements.

The thermal silicone pads with glass fiber is because the thinner the thermal silicone pads, the worse the tensile resistance and the lower the voltage resistance performance. In addition, the thermal silicone pad is too thin, and it will be very poor during use due to its poor tensile resistance. It is prone to tearing. Therefore, generally thinner thermal silicone pads will use glass fibers to enhance the tensile strength and voltage resistance of the product.

So the question is, what is a thermal silicone pads with glass fiber? What are the functional characteristics of the thermal pad with glass fiber? Let’s find out together!

The thermal pads with glass fiber is based on glass fiber cloth and silica gel, and contains a compound of silicone resin, boron nitride and glass fiber. After the use of glass fiber, the product has good toughness and strength, and enhances the high shear strength, puncture and tear resistance products. And it does not affect the multi-style thermal properties of the thermally conductive material itself, and is widely suitable for the application of any electronic and electrical equipment. The most widely used thermal conductive material industry is glass fiber cloth.

Advantages of thermal silicone pad with glass fiber

Increase the toughness of the thermal silicone pad

Ordinary thermal silicone pads do not have any reinforcing materials added. They are all ceramic alumina powders. Ordinary thermal silicone pads are soft in texture. If you do not pay attention during operation, they will be easily damaged. After the fiberglass reinforcement, there will be no damage.

Easy construction and strong operability

The glass fiber reinforcement material can supplement the disadvantages of easy deformation after the thermal conductive powder is filled. With this layer of glass fiber base material, the material will not be deformed basically, and the production line staff will be faster and more convenient when installing, and it can be operated. Strong sex.

Better control of length and width tolerances

Engineering can use this to control the assembly size very accurately, that is, the length and width tolerances can be well controlled within the required range, so that there will be no deformation of the thermal silicone pads during use, and the size will increase, resulting in thermal pads The film does not fit into the original design structure.

Wear-resistant and tear-resistant

The glass fiber reinforced material increases the wear resistance of the silicone thermal pads. For example, some design structures have screws or structural parts on the surface that require a pulling action. At this time, if ordinary silicone thermal pads are used, it is easy to cause damage during the pulling Damaged, and adding a layer of glass fiber substrate silicone sheet can solve this problem very well.

There are advantages and disadvantages. Although the silicone thermal pads with glass fiber has certain advantages in application, it also has disadvantages that cannot be ignored!

Disadvantages of thermal pad with glass fiber

increase thermal resistance

Compared with the ordinary thermal pads made of the same powder, the thermal conductivity of the thermal pads with glass fiber base material will be lower, and the thermal resistance of the thermal pads with glass fiber base material itself will increase, resulting in a year-on-year thermal conductivity effect. lower.

Unable to fully absorb uneven gaps

If it is a thermal pad with a glass fiber base material, the effect of bonding with the side in contact with the radiator or heat source will not be as ideal as that of an ordinary thermal pad, and only the tighter the bonding, the better the thermal conductivity. Well, the uneven gap cannot be fully absorbed, and the heat conduction effect will be poor.

Complex production and processing technology

The production process of the thermal pads with glass fiber base material is relatively complicated, and the operation is more difficult, because a layer of glass fiber cloth needs to be added. It is tight and seamless, and will not be peeled off during long-term use. During processing, the glass fiber cloth will also increase certain working hours, difficulty and loss.

Relatively high cost

The cost of the thermal pads with glass fiber substrate is higher than that of the ordinary thermal pads, mainly because the glass fiber cloth itself requires additional cost and the production process and processing are complicated. For customers, the increased cost itself is a disadvantage, but in general, the pros outweigh the cons.

Sometimes we always receive some special requirements from customers in the process of supplying products. While ensuring thermal conductivity, we also require adding reinforcing materials, whether it is glass fiber, single-sided adhesive, double-sided adhesive, aluminum foil. , copper foil, single-sided PI film, graphene, etc., are all to provide customers with a more convenient product experience, better product quality and ultimately meet customer application requirements, this is not also a professional thermal conductive material manufacturer. Does it really need to be done?

If Thermal Pad Adhesive?

In many electronic and electrical components that require heat dissipation, in order to meet the requirements of the process, traditional fans are not used to dissipate heat, but thinner thermal pads are selected, but the thermally conductive silicone is not directly placed between the components. When the sheet is placed, it is often subjected to adhesive treatment on the basis of the thermal pads according to the requirements of the process.

Analysis of the working principle of thermal pad adhesive

The thermal pad is mainly filled in the gap between the radiator and the heat source to remove the air in the gap, so that the heat sink and the heat source can be in close contact, but not all planes are placed horizontally, and some heat sources may be caused by It is designed to be placed vertically or on an inclined plane, so there may be a possibility of slipping during use or transportation. At the same time, the plane of the heat source may be smooth and flat. Although the thermal pads are self-adhesive, the adhesiveness is low. It is also easy to be displaced by external force.

Adhesive of the thermal pad is mainly to enable the thermal pads to be firmly fixed on the plane and not easily fall off under the condition of external force, while the backing of the thermal pads needs to be coated with adhesive on its surface, but this will increase its cost, thermal resistance, so the thermal conductivity of the thermal pad will decrease, but it must be back-adhesive in order to be fixed on the surface.

In addition, there is another reason that no matter what type of components, whether it is used for a long time or affected by the environment, there will be vibration. The thermal pad will loosen and slip, causing thermal damage to the components.

Does thermal pad adhesive affect heat dissipation?

As we know from the front, after the back glue treatment is carried out in the thermal pad, it can be firmly adhered to the component. Although the gap between the thermal pad and the component connection is greatly reduced, due to the existence of the back glue, the It is impossible to make the thermal pad work normally to dissipate heat, that is to say, the adhesive backing changes the heat dissipation coefficient of the thermal pad.

According to the previous introduction to the thermal pad, we know that the higher the heat dissipation coefficient, the better the heat dissipation effect. Therefore, after using the adhesive, the actual heat dissipation efficiency will be reduced to some extent, but this It is much better than the failure to dissipate heat due to the accidental sliding of the thermal pad. Although the problem of back glue cannot be solved at present, it will not affect the use in practice.

Introduction to the advantages and disadvantages of thermal pad adhesive

Advantages: It can stick to the surface of the heat source on one side. When the radiator or the shell slides relatively during the assembly process, the thermal pads will not move and cause positional deviation, which plays a fixed role. The thermal pads adhesive is mainly because the product has no fixing device or is inconvenient to fix. The adhesive can be used to fix the radiator and stick the IC and the heat sink, and there is no need to design another fixing structure.

In addition, the adhesive can be used to fix the radiator, and there is no need to design another fixing structure, such as no locking screws, which reduces customer costs.

Disadvantages: The thermal conductivity of the thermal pads adhesive will be worse, and the thermal conductivity will be much lower. The thermal conductivity of double-sided adhesive will be worse than that of single-sided adhesive, but whether it is single-sided or double-sided adhesive, the thermal conductivity will be The impact is much lower and the thermal conductivity is worse, but the cost will increase!

How to choose thermal pads adhesive

Basically, in all equipment that needs to use thermal pads, it is inevitable to use back glue. From the previous introduction, you can also know why the thermal pads needs to be back glued, but in actual selection, not all All kinds of back glue can be used, and different equipment and different use environments have very high requirements on the back glue. For example, in notebook computers, the back glue selected is good and sticky, and cannot be used for a long time or Drying in a hot environment will greatly reduce the heat dissipation performance of the thermal pads, that is, a barrier will be formed between the thermal pads and the chip.

In general, although the thermal conductivity of the thermal pads has decreased after the adhesive is applied, its practicability has been improved, and it can better cooperate with the product to dissipate heat. Therefore, whether to add adhesive or not depends on the actual situation. choose!

How Thick Should A Thermal Pad Be?

In the use of modern electronic products, the problem of heat generation has become extremely serious. In order to ensure operating efficiency, it is necessary to actively strive to solve the problem of heat dissipation. For example, in PCs, in order to solve the problem of CPU heating, thermal grease is usually applied between the heat sink and the CPU. Today, with the development of science, electronic products are running faster and faster, and heat dissipation is still the work of various manufacturers. A major problem to be solved is the thermal pad that is widely used today. It is called a new generation of new thermal conductivity technology. As soon as it is listed, it shows the possibility of replacing thermal grease. The choice of it is mainly determined by the thickness!

Strictly speaking, the thickness of the thermal pads has an inseparable relationship with its thermal conductivity. Why do say that? Let’s start with the thermal conduction path and principle of the thermal pad. First of all, we must be clear that when the thermal pad is pasted on a heating component, its working principle is to transfer heat from one end to the other end. The closer the distance between the heating body and the heat sink, the more sufficient the heat it transfers The more, the lower the thermal resistance and the better the thermal conductivity. So, what effect does the thickness of the thermal pads have on the heat dissipation of electronic products? Let’s take a look together!

Thickness will directly affect thermal resistance coefficient

Thermal resistance coefficient refers to the resistance it encounters in the process of heat transfer. Literally speaking, the smaller the resistance, the stronger the thermal conductivity. The thermal resistance coefficient of the thermal grease used in the early PC is very low, so it is very popular with various manufacturers. It may dry out. The thickness of the thermal pads determines the thermal resistance coefficient, but it should be noted here that the thinner the thermal pad, the better the thermal conductivity. For the choice of thickness, it mainly depends on the specific heat dissipation object.

Different thickness, different price

The thermal pads has shrinkage, so to a certain extent, it also plays a shock-proof role for electronic products. It can not only resist shocks but also conduct excess heat. The thickness of the thermal pad is also different at different price points. When choosing a thermal pad for electronic products, the thickness should be determined according to the actual situation. Too thick and thin will cause corresponding waste. Usually, the range of thickness selection is very wide, between 0.2mm-10mm, and different thicknesses determine heat transfer. The length of the path also determines the size and price of the thermal resistance coefficient.

Thickness will determine the overall structural design

In today’s era, the design of electronic circuits is becoming more and more complex, and the integration of circuits is getting higher and higher, but because of this, there will be many chips of different sizes on a circuit board, their sizes and voltages are different, and the heat dissipation is also Not the same, not to mention the problem of uneven distribution of the overall bulk of the circuit board. If the thermal pads wants to serve such a complex circuit well, the choice of the thickness of the silicone sheet on each chip should be treated specifically, rather than using a uniform thickness to solve all problems. The thickness of the thermal pads has an impact on the heat dissipation of electronic products in its market-oriented price, and will also affect the overall structural design of the product. It has to be said that in modern electronic products, the thermal pad is an important part of it.

How Are Thermal Pad Tested?

Whether it is the staff of the thermal pads manufacturer or the customer, everyone knows the thermal pads, and the specifications of the thermal pads can also be known a little, but how are the specifications and parameters of the thermal pads tested? I believe that few people can fully answer it, so CoolThermo feels that it is necessary to introduce the knowledge points of the physical property test standard of this thermal silicone gasket to everyone here, friends, come and watch!

Why use thermal silicone gaskets? The main reason is to improve the heat dissipation efficiency of heating products and reduce the impact of high temperature rise.

  1. Reduced lifespan: Long-term use of heating products without paying attention to heat dissipation will cause the temperature of the internal components of the product to continue to rise, thereby reducing the product lifespan. The lifespan of a temperature rise of 50 degrees Celsius is only half of that of a temperature rise of 25 degrees Celsius;
  2. Reduced reliability: for every 2 degrees Celsius increase, the reliability of product usage decreases by 10%;
  3. The processing speed is reduced and the signal is delayed;
  4. Increased idle power dissipation.

Therefore, when the user chooses whether the thermal silicone gasket is qualified, the following very important specifications should not be ignored by the customer: thermal conductivity, thermal resistance, thickness, hardness, tensile strength, tear strength, impact Breakthrough voltage, dielectric constant, volume resistivity and other physical properties; below, CoolThermo Technology will explain in detail what instrument, what standard, what method and how to test these specifications.

Test method for thermal conductivity of thermal pad

Thermal conductivity: It refers to the heat transferred through 1 square meter area in 1 second with a 1mm thick thermal pad, the temperature difference between the two sides is 1°C, in 1 second, expressed by λ, the unit is W/ mk, thermal conductivity, like mass, is the property of the material itself and is not affected by external factors.
Apparent thermal conductivity: This value is different from thermal conductivity because apparent thermal conductivity also includes the contact thermal resistance at the time of measurement.

Test method for thermal conductivity of thermal pads (1)

Test equipment: thermal conductivity tester
Test reference standard: ASTM D5470
Testing in a vacuum state can effectively remove the influence of air on the test. The standard thickness and pressure of the test sample are issues that need to be paid attention to.

Test method for thermal conductivity of thermal pads (2)

Test instrument: HOT DISK thermal conductivity tester
Test reference standard: TPS

Thermal resistance test method of thermal pad

Test instrument: material thermal resistance tester
Test reference standard: ASTM D5470
This standard simulates the test of structural components applying pressure on thermally conductive materials. The change of temperature conduction is monitored by the probes (six probes) attached to the bottom of the thermal conductive material, and then the thermal resistance is obtained by calculating with the computer.

How to measure the thickness of thermal pad

Measuring instruments: thickness gauge, caliper
Test reference standard: ASTM D374
Due to the softness of the product itself, the human operation factor plays a key role in the thickness test process, and the inspection workers who are skilled in caliper operation should perform the inspection as much as possible, whichever is in contact with the product. Excessive force will cause the product to compress, so here is a reminder for thermal design work. Personnel: When designing, the selection of thermally conductive materials should be at least 20% to 30% larger than the size of the gap of the structural parts.

How to measure the hardness of thermal pad

Testing instrument: Shore hardness tester
Test reference standard: ASTM D2240
There are currently three types of Shore hardness testers: shore00, shoreA, and shoreC. Different companies have different standards. Due to the softness of the thermal pad, it is recommended to use C-type hardness. Note that the thickness of the specimen is required to be at least 6mm.

Measuring method of tensile strength of thermal pad

Test equipment: universal material testing machine
Test reference standard: ASTM D412
The tensile strength test is similar to tearing, and it is also tested by a universal material testing machine. The difference is that the shape of the sample has special requirements. The computer will instruct the testing machine to pull the material until it breaks, so as to calculate the tensile strength.

Method for measuring tear strength of thermal pad

Test equipment: universal material testing machine
Test reference standard: ASTM D412
The thermal pads must be formed into a standard sample as required (usually die-cutting is used). The universal material testing machine is connected to the computer through a data cable. According to the change of stroke and force, the computer will calculate the tear strength of the product and present it in the form of a numerical value .

Measurement method of breakdown voltage of thermal pad

Test instrument: Withstand voltage tester
Test reference standard: ASTM D149

Test method for dielectric constant of thermal pad

Dielectric constant: also known as permittivity, the medium will generate induced charges and weaken the electric field in the external electric field. The ratio of the permittivity in a medium to the permittivity in vacuum in the same original electric field is the relative permittivity, also known as the relative permittivity. Relative permittivity, if a material with a high dielectric constant is placed in an electric field, the strength of the field will drop significantly in the dielectric.
The dielectric constant is an important data to characterize the electrical properties of dielectrics or insulating materials. It is often expressed by ε. The dielectric constant of vacuum is 1.0, the dielectric constant of thermally conductive products is 2~10, and the dielectric constant of superconductors is infinite.
Test instrument: WY2851Q meter
Test reference standard: ASTM D150
Introduction to the test method: It is composed of two micro-measuring capacitors. The plate capacitor is used to hold the sample. The cylindrical capacitor is equipped with a Q meter as an indicator. The change of the Q value of the sample is converted from the change of the scale reading value of the cylindrical capacitor, and the dielectric constant is converted from the change of the scale value of the plate capacitor.

Test method for volume resistivity of thermal pad

Test instrument: high resistance meter
Test reference standard: ASTM D257
Keep a standard volume of thermal pads under the specified voltage for the required time, measure the generated current, and inversely calculate the resistance of the material itself through the generated current. The higher the volume resistivity, the more effective the material is as an electrically insulating component.

The above is the sharing of CoolThermo’s introduction to the testing standards and methods of thermal pads. I believe that after reading the small partners, the thermal conductivity, thermal resistance, thickness, hardness, tensile strength, tear strength, breakdown voltage, dielectric Have a clear understanding of the test methods and standards for physical properties such as constants and volume resistivity!

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.

What Is Thermal Silicone?

Thermal silicone, also known as thermally conductive adhesive, thermally conductive silicone rubber, etc., is made of organic silicone as the main body, added with fillers, thermal conductive materials and other polymer materials, and has good thermal conductivity and electrical insulation properties.

Ordinary thermal conductive silica gel is added with aluminum oxide, etc., and high thermal conductive silica gel is added with thermal conductive substances such as boron nitride. Manufacturers of thermally conductive silicone adhesives or potting materials can generally make different thermal conductivity, curing speed, viscosity, color, hardness, etc. according to their needs.

As a silicone rubber matrix with excellent insulation and shock absorption properties, its thermal conductivity is only about 0.2W/m.K, but by adding high-performance thermal conductive fillers to the matrix, including metal fillers (such as Al, Cu, MgO, AIN , BN) and non-metallic materials (such as SiC, graphite, conductive carbon black, etc.), the thermal conductivity can be improved several times or even dozens of times. The thermal conductivity of thermal silicone materials is ultimately determined by the silicone rubber matrix, filler properties, filler ratio, filler distribution, and processing technology.

Thermal silicone includes room temperature vulcanized and high-temperature vulcanized silicones. Such silicones generally include thermal silicone adhesives, thermal potting compounds, and thermal conductive gaskets that have been vulcanized into a certain shape.

Generally, the thermal conductivity of high-temperature vulcanized thermal conductive silicone is slightly worse than that of room-temperature vulcanized thermal silicone. , heat dissipation, insulation and sealing, etc., thermal silicone can provide the high elasticity and heat resistance required by the system, and can quickly transfer the heat of the system.

The thermal conductivity of different thermal silicones varies greatly. The cost price difference is also huge (but if insulation is not required, the production cost can be greatly reduced and a high thermal conductivity can be achieved).

Thermal silicone is a high-end thermal compound. The non-conductive properties of the product can avoid risks such as short circuits; it has the effect of cooling and bonding electronic devices. It can be cured to a higher hardness elastomer in a short time. After curing, it is closely attached to its contact surface to reduce thermal resistance, thereby facilitating the heat conduction between the heat source and its surrounding heat sinks, motherboards, metal shells and outer shells. Thermal conductive silica gel has the advantages of high thermal conductivity, good insulation performance and easy use. It has good adhesion to metals including copper, aluminum, stainless steel, etc., and the curing form is dealcoholized, which does not corrode metal and non-metal surfaces.

Thermally conductive silica gel can be widely applied to various electronic products, the contact surface between the heating element (power tube, thyristor, electric heating stack, etc.) It plays the role of heat transfer medium and moisture-proof, dust-proof, anti-corrosion, shock-proof and other properties. It is suitable for surface coating or overall potting of various microwave devices such as microwave communication, microwave transmission equipment, microwave special power supply, and regulated power supply.

It is widely used to replace thermal grease and thermal pads for filling bonding and heat dissipation between CPU and radiator, thyristor intelligent control module and radiator, transistor and thermistor connection, high-power electrical module and radiator. After using this glue, the traditional connection method of card and screw can be removed, and the result is more reliable filling and heat dissipation, simpler process, and more economical cost.

Such as: integrated circuits that can be widely used in personal portable computers, microprocessors, memory modules, cache memories, sealed integrated chips, DC/AC converters, IGBTs and other power modules, semiconductors, relays, rectifiers and transformers, etc. package. Fixing of electronic and electrical components and flame retardant, thermal conductivity, insulation, shock-proof, moisture-proof sealing. Heat dissipation of high-power LED products. It is especially suitable for bonding and sealing with high requirements on thermal conductivity.

Correct use of thermal silicone

  1. Clean the surface: Clean the surface of the sticky or coated object to remove rust, dust and oil.
  2. Gluing: Unscrew the cap of the hose, first pierce the seal with the tip of the cap, squeeze the glue onto the cleaned surface to make it evenly distributed, and close and fix the glued surface.
  3. Curing: When the coated parts are placed in the air, the phenomenon of skin formation will occur slowly, and any operation should be completed before the surface skin formation. The curing process is a curing process from the surface to the inside. Within 24 hours (room temperature and 55% relative humidity), the glue will be cured to a depth of 2 to 4 mm. If the part is deep, especially in the part that is not easy to touch the air, The time to complete curing will be extended, and if the temperature is lower, the curing time will also be extended.
  4. Do not move, use or pack the operated parts until they have reached sufficient strength.
  5. Storage: Unused glue should be tightened immediately and sealed.

Precautions

After the operation is completed, the unused glue should be tightened immediately and the cap should be tightly sealed. When using it again, if there is a little crust on the seal, it can be removed without affecting normal use. During the storage process of the glue, there may be a small amount of curing phenomenon at the mouth of the nozzle. After removing it, it can be used normally without affecting the performance of the product.
This product will release a small amount of by-products during the curing process, which is slightly irritating to the skin and eyes. It is recommended to use it in a well-ventilated place. In case of accidental contact with the skin, wipe it clean, and then rinse with water; in case of accidental contact with eyes, immediately rinse with water and go to the hospital for examination.

The above is an introduction to the definition, characteristics, functions and usage of thermal silicone. Only with a sufficient understanding of thermal silicone can we more accurately select the thermal silicone solution and achieve better performance in practical applications. Now, there are many manufacturers of thermal silicone on the market, and they are widely used. They are mainly used in the optoelectronic industry, computer industry, network industry, home appliance industry, semiconductor lighting industry, etc. At present, 5G and new energy are another development trend, and thermal silicone is It is an indispensable thermal conductive material in electronic heat dissipation materials. It can be seen that the development trend of thermal conductive silica gel is even more immeasurable, and the future is bright.

How To Apply Thermal Grease?

Thermal grease, also known as thermal conductive grease, thermal paste, or thermal compound, etc., is used to create a thermally conductive layer between the processor and the heat sink. Thermal grease is the link between the cpu and the radiator for heat transfer. It also acts as a heat transfer medium, increases the contact area, buffers vibration and pressure, and fills the pits between the radiator and the cpu. Since thermal grease conducts heat better than air, applying thermal grease between the processor and the heat sink can enhance heat transfer from the processor to the heat sink.

After the influence of the thickness of silicone grease on heat dissipation, the CPU temperature fluctuates between 61-62°C when applying an appropriate amount of silicone grease, and the CPU temperature fluctuates between 63-64°C when a large amount of silicone grease is applied. It can be found that the thickness of the silicone grease layer has an obvious effect on heat dissipation. From this test, there is a 2°C gap between the two.

Therefore, the correct application of thermal grease has a multiplier effect on the heat dissipation of the cpu. Too much or too thick thermal grease is equivalent to adding a heat-conducting medium, which affects the heat transfer of the cpu to the radiator (the heat of the thermal grease the resistance is larger than the thermal resistance of metal), and excess heat dissipation silicone grease will even flow into the CPU socket. Although the current silicone grease is generally insulating and will not cause a short circuit, it flows to the metal contacts of the CPU and the socket. It is easy to cause a short circuit between the cpu pins. In the light of the computer can not be started, in severe cases, it will cause damage to the cpu or other peripheral hardware; too little or uneven application of thermal grease will cause no gap between the cpu and the radiator. The medium of buffering and heat conduction reduces the contact area between the CPU and the heat sink in disguised form, resulting in a decrease in heat dissipation efficiency.

Process plan for applying thermal grease

  1. First clean the surface of the CPU core and the bottom of the heat sink with a high-purity solvent (such as high-purity isoamyl alcohol or acetone) and a lint-free cloth (such as a camera lens cloth), taking care not to let your fingers touch the surface of the core and heat sink.
  2. Determine the area on the heat sink that is in contact with the CPU, and apply an appropriate amount of thermal grease on the CPU. At this time, you can ignore its uniformity, coverage and thickness.
  3. Prepare a moderately soft and hard plastic scraper (or cardboard), spread the thermal grease, and use the scraper to scrape in one direction at an angle of about 45 degrees, so that the thermal grease is evenly formed on the entire surface of the CPU. thin layer.
  4. Apply a small amount of thermal grease to the bottom of the radiator. Similarly, using the method we just applied to the CPU, apply the thermal grease to an area as large as the CPU shell. The purpose of this step is to make the particles in the thermal grease fully Fill the uneven grooves on the bottom of the radiator to make sure that there are no foreign objects on the surface of the radiator base and the CPU core, then install the radiator on the cpu, and fasten the fasteners.

Matters needing attention after applying thermal grease

  1. The heat-dissipating silicone grease will never be cured after being applied. It should be noted that if the heat-dissipating silicone grease is cured, this heat-dissipating silicone grease is unqualified and cannot be used in industrial manufacturing in large quantities. When buying, you need to pay attention. In order to avoid this situation, users can buy products with word-of-mouth guarantee, which can reduce the chance of this situation. For example, Nuofeng Electronics nfion, which focuses on the R&D and customized production of heat-dissipating silicone grease, can provide different customized solutions.
  2. Apply evenly: For the bottom surface of an ordinary radiator, the thickness of thermal grease applied is about the thickness of a piece of paper. After the thermal grease is applied, place the heat sink on the CPU. At this time, it can only be pressed lightly, and the heat sink cannot be rotated or translated. Otherwise, the thickness of the thermal grease between the heat sink and the CPU may be uneven.
  3. It is necessary to observe whether there are air bubbles after applying the heat-dissipating silicone grease. If there are air bubbles, they can be punctured with a toothpick. Otherwise, these air bubbles will cause uneven application. In addition, there will be air in the air bubbles, which will also increase the thermal resistance and affect heat dissipation. Effect.
  4. The remaining heat dissipation silicone grease needs to be sealed and can be placed in a cool place, so that it can be used up within 12 months. After more than 12 months, the thermal conductivity will decrease and cannot be used again.

Thermal grease is a thermally conductive material with good heat dissipation performance. Thermal grease can be used in various electrical appliances or electronics. There is no change in performance before and after use, and it is always in the state of grease. Thermal grease can only be smeared in the middle of the heating element of the electrical appliance and the heat dissipation facility. Only by mastering the correct operation method when smearing can achieve the purpose of heat dissipation.

What Is a Thermal Pad? What Is Thermal Pad Made Of?

Thermal pads are high-performance gap-filled thermally conductive materials, which are mainly used for the transfer interface between electronic devices and heat sinks or product casings; traditionally used heat-dissipating and thermally conductive materials are mostly metals, such as Ag, Cu, Al, and metal oxides, such as Al2O3, MgO, BeO and other non-metallic materials, such as graphite, carbon black, etc.; but with the development of industry and science and technology, people have put forward new requirements for thermal conductive materials, hoping that the materials have excellent comprehensive properties.

In the field of electrical and electronics, due to the rapid development of integration technology and assembly technology, the volume of electronic components and logic circuits has been reduced by thousands of times, and insulating materials with higher thermal conductivity are required to solve the problem of heat dissipation. In recent decades, the application field of polymer materials has been continuously expanded. The use of synthetic polymer materials to replace metal materials used in traditional industries has become one of the directions of the world’s scientific research efforts, and thermal conductive gaskets have emerged as the times require.

What material is the thermal pad made of?

The thermal pad is based on silica gel, adding certain metal oxides and various thermal auxiliary materials, and then synthesizing the thermal pad through a special process. The thermal pad is a polymer composite thermal conductive material that uses silicone resin as the adhesive base material and is filled with thermal conductive powder to achieve thermal conductivity.

Thermal conductive gasket making base material

  1. Insulating and thermally conductive material powder: magnesium oxide, aluminum oxide, boron nitride, beryllium oxide, aluminum nitride, quartz and other silicone plasticizers
  2. Flame retardant: magnesium hydroxide, aluminum hydroxide
  3. Inorganic colorants (used to fill products with specific colors)
  4. Cross-linking agent (make the product slightly sticky)
  5. Catalyst (process molding requirements)
    Note: The thermal pad plays the role of heat conduction, forms a good thermal conduction path between the heating element and the heat sink and can fill the gap.

Thermal gasket filler composition

  1. Metal powder filler: copper powder, aluminum powder, iron powder, tin powder, nickel powder, etc.;
  2. Metal oxides: aluminum oxide, bismuth oxide, beryllium oxide, magnesium oxide, zinc oxide;
  3. Metal nitrides: aluminum nitride, boron nitride, silicon nitride;
  4. Inorganic non-metals: graphite, silicon carbide, carbon fiber, carbon nanotubes, graphene, beryllium carbide, etc.

Process principle

The thermal conductivity of thermal gaskets depends on the interaction of the polymer with the thermally conductive filler. Different types of fillers have different thermal conductivity mechanisms.
The heat conduction mechanism of metal fillers, the heat conduction of metal fillers is mainly carried out by the movement of electrons, and the corresponding heat is transferred in the process of electron movement;
The thermal conduction mechanism of non-metallic fillers, the thermal conduction of non-metallic fillers mainly depends on phonon heat conduction, and its thermal energy diffusion rate mainly depends on the vibration of adjacent atoms. Including metal oxides, carbides and nitrides.

With the advent of the 5G era, electronic products are developing towards functional integration. There are more and more components on the circuit board, and the power of electronic products is getting higher and higher. The thermal conductivity of thermal pads is increasingly required. The commercial application of thermal pads also has broader development prospects. This requires relevant thermal pad manufacturers to continuously develop thermal pad materials with better performance.

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