When the electronic equipment is working, the components will generate a certain amount of heat, which causes the internal temperature of the equipment to rise rapidly.
If the heat is not released in time, the temperature of the equipment will continue to rise, and the components will fail due to overheating, which will lead to the reliability of electronic equipment decline or damage.
Heat dissipation mode can be simply divided into active heat dissipation, passive heat dissipation (conduction, convection and radiation).
The thermal design engineer will choose the appropriate heat dissipation method and heat conduction material according to the heat condition.
In the selection of heat conduction medium, we should not only consider its heat transfer capacity, but also take into account the production process, the use of convenience, maintainability and cost performance factors.
At present, the commonly used thermal interface materials are:
Heat conduction silicone sheet, heat conduction silicone grease, heat conduction insulating material, heat conduction pouring sealant, heat conduction gel, heat conduction adhesive, etc.
The following are simple descriptions of the characteristics of these kinds of thermal conductive materials and the indicators that need to be paid attention to when selecting them:
Thermal conductive silica gel sheet
A thermal conductive interface material with high softness, high compliance and high compression ratio, which can fill the gap between the heating components and the radiator (housing) to improve heat transfer
Efficiency, but also play a role in insulation, shock absorption, etc.
In the selection, thermal conductivity silica gel sheet with moderate parameters such as thickness, thermal conductivity, working temperature range and pressure resistance should be selected according to the actual situation.
At the same time, we also need to pay attention to the hardness, volume resistivity, dielectric constant, tensile strength and other parameters:
hardness
The lower the hardness, the greater the effective contact area of the thermal conductive silica gel sheet, the better the thermal conductivity effect, and the worse it is.
Tensile strength
High tensile strength, strong resistance to shock and vibration load.
Thermal conductive silicone
Commonly known as heat conduction paste and heat dissipation paste, it is a kind of silicone oil as base oil, metal oxide as filler, with a variety of functional additives, by the specific
Processed from the paste thermal interface material. It has high thermal conductivity, low thermal resistance, wide operating temperature range, low volatility, low oil separation,
Strong weather resistance and other excellent performance.
The following indicators are mainly concerned in the selection:
Oil detachment, thermal conductivity and thermal resistance, viscosity, temperature range, dielectric constant
Oil from
Refers to the amount of silicone oil precipitation after the product is kept at 200℃ for 24 hours. It is an index to evaluate the heat resistance and stability of the product. Good quality thermal conductive silicone grease,
The oil detachment is very low, approaching zero.
Coefficient of thermal conductivity and resistance
Generally speaking, the greater the thermal conductivity of the thermal conductivity grease, the same thickness of the thermal conductivity grease coating conditions, the smaller the thermal resistance, the better the thermal conductivity effect.
viscosity
A performance index used to characterize the fluidity and viscosity of thermal silicone grease, which is greatly affected by temperature. In general, the higher the coefficient of thermal conductivity, the larger the viscosity.
Operating temperature range
It can meet the operating temperature range of electronic components between -40 ℃ and 200℃.
Dielectric constant
The dielectric constant is used to measure the ability of an insulator to store electrical energy. It refers to the electrical capacity between two metal plates when the insulating material is the medium and the air between the same two plates
Is the ratio of capacitance in medium or vacuum.
In addition, you need to consider the volume resistivity factor (a measure of insulation), RoHS certification, and packaging (barreled, canned)
Or a syringe).
Thermal insulation gasket
Thermal insulation gasket has thermal conductivity, insulation, high voltage resistance and other characteristics, excellent mechanical stress resistance and good electrical isolation reliability.
In the selection of thermal insulation materials, the parameters that need to be paid attention to are:
Operating temperature, thickness, tensile strength, thermal resistance, breakdown voltage.
Thermal sealing adhesive
Silica gel heat conduction sealing glue is composed of two components (A, B), according to the weight of 1:1 mixing and curing, with dustproof, waterproof and shockproof,
Flame retardant, sealing, bonding, thermal conductivity and excellent joint filling effect.
Parameters and indicators to be paid attention to during selection are as follows:
Thermal characteristics
Thermal conductivity: the higher the thermal conductivity coefficient, the better the thermal conductivity and heat dissipation effect
Electrical properties
Among them, more attention is paid to the breakdown voltage and volume resistivity.
Physical properties of
Fluidity, density: strong popularity can be used to fill the gap of smaller pores, increase the volume of heat conduction and heat dissipation contact surface; The same thermal conductivity, the higher the density
Low, it can effectively improve heat dissipation performance and efficiency when applied to automotive power supply industry.
Thermal conductive gel
Single-component or two-component silica gel thermal conductivity products, mainly to meet the requirements of low stress and high compression modulus in use.
Shows a low contact thermal resistance and good electrical insulation characteristics, curing is equivalent to heat conduction gasket, high temperature resistance, good aging resistance, can be in
-40~200°C long-term operation. When selecting thermal conductivity gel, attention should be paid to its thermal conductivity coefficient, anti-cracking, thermal resistance and so on.
Thermal bonding adhesive
The utility model relates to a single component moisture curing heat conduction material which integrates bonding, heat conduction, insulation and sealing.
It has a fast table dry and curing speed, high and low temperature resistance, strong weather resistance, excellent electrical insulation performance, can work in -50℃ ~ 200 degrees environment for a long time.
When selecting, attention should be paid to the following parameters: thermal conductivity, bonding strength, density, etc.
The above is an important aspect to judge the quality and performance of thermal conductive materials.
Generally speaking, the higher the coefficient of thermal conductivity, the better the thermal conductivity effect, the higher the price.
