Thermal gel and its application

With the continuous upgrading of electronic equipment, the performance requirements for all aspects of equipment are getting higher and higher. However, high-performance devices generate more heat during operation, so how to control the temperature to ensure that electronic devices operate at high speed is crucial.

When traditional thermal gap materials cannot be fitted and installed, a highly reliable thermal management material for heating devices is being widely used in electronic equipment, which is thermal gel.

What is thermal gel?

Thermal gel is based on silicone resin as the base material, adding thermal conductive filler and bonding material according to a certain proportion of configuration, and processed by special technology paste gap filler material, according to 1:1 (mass ratio) mixed and cured into high-performance elastomer, with the shape of the structure, with the best structural applicability and structural surface coating characteristics. This material has some advantages of thermal shims and thermal grease at the same time, which better makes up for the weaknesses of the two, and is especially suitable for space-limited heat conduction needs.

Advantages of thermal gel:

1. Excellent thermal conductivity. Thermal gel is softer and has better surface affinity than thermal gaskets, and can be compressed to a very small thickness, as thin as 0.1mm, so that the heat transfer effect is significantly improved. At this time, the thermal resistance can be 0.08℃·in2/ W-0.3 ℃·in2/W to achieve part of the performance of silicone grease, which not only provides a high guarantee factor for electronic products, but also guarantees the stability of electronic products (especially products requiring high heat dissipation) during use, improving the service performance and life of the product;

2. It has excellent electrical performance, aging resistance, cold and thermal alternating performance (can work for a long time at -40~200℃), electrical insulation performance, shock resistance, vibration absorption and stability, which increases the safety factor of electronic products during use;

3. Meet a variety of applications. It has no sensitivity to thickness, has good adaptability in the equipment assembly process, and is compatible with the impact of dimensional tolerances on related devices or structural parts. It can provide good contact between the heating surface and the cooling surface under low pressure or no pressure;

4. Easy forming, thickness controllable; High thermal gel products do not need refrigeration, room temperature storage, easy to use;

5. The system is colorless and transparent (except for special purposes) and can be used with any color;

6. Continuous operation advantage. Thermal gel is easy to operate, can be manually sizing or mechanical sizing. The common continuous use method is mechanical dispensing, which can achieve fixed-point quantitative control, meet any working environment and working conditions, save labor and improve production efficiency.

How to choose thermal gel?

Thermal gel has a single, two component difference, the biggest difference between the two is that the single component thermal gel is similar to thermal silicone grease, and the two-component thermal gel is similar to thermal silicone sheet, under normal circumstances, the single component thermal gel will not cure, has been maintained wet state, high oil yield. (Note: At present, there are also special uses, and single components can also be cured). The two-component thermal gel will cure and solidify into an elastomer, which has certain cohesiveness and low oil yield. The two choose their suitable application according to their own characteristics.

Method of using thermal gel:

When using the manual heat transfer adhesive, it is necessary to unscrew the mouth cover, connect the threaded mixing head, and then stick the hose to the bayonet of the AB glue gun, and apply glue vigorously. The AB glue is extruded from the glue gun to the mixing head, and the uniform mixing is completed under the guidance of the thread, and finally the heat transfer glue is evenly mixed to the heating position according to the design of the heat dissipation structure. The thermal gel of the dispensing type can be operated directly according to the instructions of the dispensing machine.

Different thermal conductivity, different manufacturers of thermal gel curing time is not the same, and the curing temperature has an impact on its curing time, only strict reference to the corresponding instructions can be operated. In general, when A and B glue contact from the mixing head, the colloidal will first experience the viscosity increase, the surface gradually dries, the internal hardening, the hardness continues to increase the process, when the final hardness no longer changes, indicating that the thermal gel has been completely cured into an elastomer.

Application of thermal gel:

Thermal gel is widely used in LED chip, communication equipment, mobile phone CPU, memory module, IGBT and other power modules, power semiconductor field.

1. Typical applications include the heat transfer between the drive module components and the housing in automotive electronics, such as the engine control unit, ballast, fuel pump control and power steering modules, which mainly play a high guarantee of heat dissipation and improve the performance and life of the product.

2. LED bulb in the driving power. In the export of LED lights, in order to pass UL certification, manufacturers use two-component potting glue for potting. With the current quality of LED lamp beads, the lamps exported to the United States require 50,000 hours of warranty is no problem, the fault is the power supply, the use of potting glue after potting power can not be removed, can only be scrapped and replaced the whole lamp.

If the thermal gel is used to locally fill the power supply, the heat can be effectively exported, and the power supply can be easily replaced if there is a problem with the power supply, saving costs for the enterprise. However, if it is required for waterproof lamps, it is still necessary to use potting glue rather than gel. Because the thermal gel is not strongly adhesive after curing, it cannot be waterproof and moisture-proof.

3. LED daylight tube. For the design of the power supply at both ends, in order not to occupy a large amount of the size of the lamp, the space design of the two power supplies is relatively small, and the power of the 1.2-meter LED fluorescent lamp is usually designed to 18w to 20w, so that the heat flux of the driving power supply will be large. Thermal gel can be filled into the gap of the power supply, especially attached to the power device, to help heat dissipation and extend the life of the lamp. For some sealed module power supplies, thermal gel can be locally filled to achieve the effect of thermal heat dissipation.

4. Heat dissipation of the chip. Similar processors and heat sinks in the middle of the silicone grease layer is the same principle, its role is to let the heat emitted by the processor can be more quickly transferred to the heat sink, which is emitted into the air.

5. mobile phone processor heat dissipation. The thermal gel is used in the processor of Huawei mobile phone and is applied between the chip and the shield to reduce the contact thermal resistance between the chip and the shield and achieve efficient heat dissipation of the chip set. Because the thermal gel also has excellent wettability, it can ensure low Rc (contact resistance) to achieve thermal management, even in the most heated smartphone components such as integrated circuits (IC) and central processing units (CPU), it is not easy to form hot spots, and the heat dissipation effect is better than that only coated with thermal graphite. It is worth noting that the thermal gel can be easily stripped without residue for rework, which is a big advantage for consumer devices and is loved by smart device manufacturers.