What is thermal conductive silica gel sheet
Thermal conductive silica gel sheet is a kind of thermal conductive medium material synthesized by special process with silica gel as the base material, adding various auxiliary materials such as metal oxide, etc. in the industry, it is also called thermal conductive silica gel pad, thermal conductive silica film, soft thermal conductive pad, thermal conductive silica gel pad, etc. it is specially designed and produced to use the gap to transfer heat, which can fill the gap, complete the heating part and heat dissipation part It can meet the design requirements of miniaturization and ultrathin of the equipment. It is a kind of excellent heat conduction filling material with high technology and usability, wide range of thickness and application.
Heat conductive silica gel sheet
The production process of thermal conductive silica gel sheet mainly includes: raw material preparation → plastic refining, mixing → molding and vulcanization → trimming and cutting → inspection, etc. The following is a brief introduction to the production process of thermal conductive silicon film:
1. Raw material preparation
The thermal conductivity of ordinary organic silica gel is only about 0.2w/m · K. However, the thermal conductivity of silica gel can be improved by mixing thermal conductive fillers. Commonly used thermal conductive fillers include metal oxides (such as Al2O3, MgO, BeO, etc.), metal nitrides (such as sin, AlN, BN, etc.). The thermal conductivity of fillers is not only related to the material itself, but also closely related to the particle size distribution, morphology, interface contact, and the degree of internal binding of molecules. Generally speaking, the heat conduction effect of fibrous or foil sheet heat conduction filler is better.
2. Molding and mixing
Plasticizing and mixing is a process of silica gel processing, which means to use mechanical or chemical methods to reduce the molecular weight and viscosity of raw rubber to improve its plasticity and obtain appropriate fluidity, so as to meet the needs of further processing of mixing and molding. The raw materials for making thermal conductive silicon film are generally damaged by mechanical high-speed stirring. After color mixing, the opalescent silica gel is used to change the flakes of various colors.
3. Molding vulcanization
If you want to make a soft, elastic and pull-resistant thermal conductive silicon film, you need to use organic silica gel that has been re vulcanized. Curing is also called curing. After the first stage of heating and forming, the crosslinking density of the liquid silica gel is not enough. The tensile strength, resilience, hardness, swelling degree, density and thermal stability of the silicone film can be greatly improved by further vulcanization. If the second vulcanization is not carried out, the thermal conductive silica gel sheet may be affected to some extent in performance, and no better product can be obtained. The parameters of the product after the first vulcanization are different from those of the second vulcanization, which is related to the actual operation process and steps.
4. Trim cut
The heat-conducting silicon film after high-temperature treatment needs to be placed for a period of time, so that it can be cut in different sizes and specifications after natural cooling, instead of other rapid cooling methods. Otherwise, it will directly affect the product performance of thermal conductive silica gel pad.
5. Finished product inspection
The main items to be tested include: thermal conductivity, temperature resistance range, volume resistivity, voltage resistance, flame retardancy, tensile strength, hardness, thickness, etc.
Advantages of thermal conductive silicon film
1. Soft material, good compression performance, good thermal insulation performance, large adjustable thickness range, suitable for filling cavity, natural viscosity on both sides, strong operability and maintainability;
2. The main purpose of selecting thermal conductive silicon film is to reduce the contact thermal resistance between the heat source surface and the contact surface of the radiator, and the thermal conductive silicon film can fill the gap between the contact surfaces well;
3. Because air is a bad conductor of heat, it will seriously hinder the heat transfer between the contact surfaces, and the air can be extruded out of the contact surface by adding a heat conducting silica gel sheet between the heat source and the radiator;
4. With the supplement of the thermal conductive silicon film, the contact surface between the heat source and the radiator can be fully contacted better, and the face-to-face contact can be achieved truly;
5. The thermal conductivity of the thermal conductive silicon film is adjustable and its thermal stability is better;
6. The process difference of heat conduction silica gel sheet in structure is closed, which reduces the process difference requirements of radiator and heat dissipation structure;
7. The thermal conductive silica gel sheet has the insulating property (this feature needs to be added with appropriate materials in the production);
8. The heat conducting silica gel sheet has the effect of shock absorption and sound absorption;
9. The thermal conductive silica gel sheet has the convenience of installation, test and reuse.
Disadvantages of thermal conductive silicon film
Compared with thermal conductive silicone grease, thermal conductive silicone film has the following disadvantages:
1. Although the thermal conductivity is higher than that of silicone grease, the thermal resistance is also higher than that of silicone grease;
2. The process of thermal conductive silicon film with thickness less than 0.5mm is complex and its thermal resistance is relatively high;
3. The range of temperature resistance of thermal conductive silicone grease is larger, they are thermal conductive silicone grease - 60 ℃ ~ 300 ℃, thermal conductive silicone wafer - 50 ℃ ~ 220 ℃;
4. Price: thermal conductive silicone grease has been widely used at a low price. Thermal conductive silicone chips are mostly used in notebook computers and other thin, small and precise electronic products, with a slightly higher price.
Application field of thermal conductive silicon film
◆ LED industry use
Thermal conductive silicon film is used between aluminum substrate and heat sink
Thermal conductive silicon film is used between aluminum substrate and shell
◆ power supply industry
Heat conduction between MOS tube, transformer (or capacitor / PFC inductor) and heat sink or shell
Communication industry
Heat conduction between the main board IC and the heat sink or shell
● heat conduction and heat dissipation between set top box DC-DC IC and shell
◆ application of automotive electronics industry
Applications in the automotive electronics industry (such as xenon lamp ballast, audio, vehicle series products, etc.) can be used to heat conductive silica gel sheet
◆ application of PDP / LED TV
Heat conduction between power amplifier IC, image decoder IC and radiator (shell)
◆ home appliance industry
Microwave oven / air conditioner (between fan motor power IC and shell) / electromagnetic oven (between thermistor and radiator)
Selection of thermal conductive silicon film
Selection of thermal conductivity
The selection of thermal conductivity depends on the power consumption of heat source and the heat dissipation capacity of radiator or heat dissipation structure. Generally, the chip temperature specification parameter is relatively low, or it is relatively sensitive to temperature, or the heat flow density is relatively large (generally more than 0.6w/cm3, heat dissipation treatment is required, and generally when the surface is less than 0.04w/cm2, only natural convection treatment is required). These chips or heat sources need to undergo heat dissipation treatment, and try to select the heat conduction silica gel with high thermal conductivity.
Generally, the chip junction temperature is not allowed to be higher than 85 ℃ in the consumer electronics industry. It is also recommended that the surface of the control chip be lower than 75 ℃ during high temperature test. The components of the whole board are basically commercial grade components, so the internal temperature of the system is not more than 50 ℃ at room temperature. It is recommended that the temperature of the first surface, or the surface that can be contacted by the end customer, be lower than 45 ℃ at normal temperature. The silica gel sheet with high thermal conductivity can meet the design requirements and retain some design margins.
Note: heat flux: it is defined as the heat per unit time (1 second) passing through the section per unit area (1 square meter). The junction temperature is usually higher than the shell temperature and device surface temperature. The junction temperature can be used to measure the heat dissipation time and thermal resistance from the semiconductor wafer to the packaging device shell.
◆ factors affecting thermal conductivity of silica gel
1. Types and properties of polymer matrix materials
The higher the thermal conductivity of the matrix material, the better the dispersion of the filler in the matrix and the better the bonding degree between the matrix and the filler, the better the thermal conductivity of the thermal conductive composite material.
2. Type of filler
The higher the thermal conductivity of the filler, the better the thermal conductivity of the thermal conductive composite.
3. Shape of filler
Generally speaking, the order of formation of heat conduction path is whisker & gt; fibrous & gt; flake & gt; granular. The easier the filler forms heat conduction path, the better the heat conduction performance.
4. Content of filler
The distribution of fillers in polymer determines the thermal conductivity of composites. When the filler content is small, the heat conduction effect is not obvious; when the filler is too much, the mechanical properties of the composite will be greatly affected. When the content of fillers increases to a certain value, the interaction between fillers forms a heat conduction network chain similar to a mesh or a chain in the system. When the direction of the heat conduction network chain is the same as the direction of heat flow, the heat conduction performance is the best. Therefore, there is a critical value for the amount of heat conducting filler.
5. Bonding characteristics of interface between filler and matrix material
The higher the degree of combination between the filler and the matrix, the better the thermal conductivity. The thermal conductivity of the filler can be increased by 10% - 20% by selecting the appropriate coupling agent for surface treatment.
Installation method of thermal conductive silicon film
1. Keep the end surface of the thermal conductive silicone film clean, prevent the fouling on the thermal conductive silicone film, and the self-adhesive and sealing thermal conductivity of the contaminated thermal conductive silicone film will become poor.
2. When removing the heat-conducting silica gel sheet, the heat-conducting silica film with large area should be grabbed from the center, and the smaller area is not required. Because the large heat-conducting silica gel sheet is not evenly stressed, it will cause deformation, affect subsequent operation, and even damage the silica film.
3. Take the sheet with left hand and tear off one of the release protective films with right hand. It is not allowed to remove both protective films at the same time, reduce the number and area of direct contact with the thermal conductive silicon film, and keep the self-adhesive and thermal conductivity of the thermal conductive silicon film from being damaged.
4. Tear off one side of the protective film and face the radiator. First align the thermal silicon film with the radiator. Slowly put down the heat-conducting silica gel sheet. Be careful to avoid bubbles.
5. If there are bubbles in the operation, pull up one end of the silicon film and repeat the above steps, or with the aid of a tool, wipe off the bubbles gently. The force should not be too large, so as to avoid damage to the heat-conducting silicon film.
6. Tear off the other side of the protective film, put it into the radiator, and tear off the last side of the protective film with a small force to avoid scratching or pulling up the thermal conductive silica gel sheet.
7. After fastening or using the strong adhesive heat-conducting silicone sheet, apply certain pressure to the radiator and store it for a period of time to ensure that the heat-conducting silicone sheet is fixed properly.
To sum up, the heat dissipation effect of the thermal conductive silicone film is very good. During the installation of the thermal conductive silicone film, it is recommended that you should be careful not to be impatient, which will cause bubbles and damage to the thermal conductive silicone film, otherwise, money and time will be wasted.
Source: collated from the Internet
In the 5g era, the functions of intelligent devices are becoming more and more complex, the integration of chips and modules and the density of parts are increasing rapidly, which leads to the continuous improvement of power consumption and heating density of devices. Therefore, the new heat conduction and cooling materials have become an important research topic "cime 2020" The exhibition will focus on the latest products and technologies of the heat conduction and heat dissipation materials industry, establish a brand image for enterprises, promote trade cooperation and market development, lead the industry trend, strengthen the interaction of production, research and development and sales, deeply understand the future development trend of the heat conduction and heat dissipation materials market at home and abroad, and tap the future of the heat conduction and heat dissipation materials market with a development perspective New demands, innovation of exhibition connotation, all-round and multi-level organization of professional visitors provide the best platform for technical exchange, product display and trade negotiation for exhibitors and participants. 2020 Shenzhen International Thermal and cooling materials exhibition will be held in Shenzhen from August 27 to 29, 2020