Comparison of Common Thermal Conductive Fillers
Thermal conductive materials are divided into thermal conductive plastics and thermal conductive insulating plastics. The main components of thermal conductive plastics include matrix materials and fillers. The matrix materials include PPS, PA6 / PA66, LCP, TPE, PC, PP, PPA, peek, etc; The thermal conductive fillers include AlN, BN, SiC, MgO, Al2O3, ZnO, etc.
Next, we compare several common thermal conductive fillers one by one:
Advantages: very high thermal conductivity.
Disadvantages: expensive. Aluminum nitride will react with water after absorbing moisture and hydrolyze AlN + 3h20 = Al (OH) 3 + NH3. The Al (OH) 3 produced by hydrolysis will interrupt the heat conduction path and affect the phonon transmission. Therefore, the thermal conductivity of products is low. Even if silane coupling agent is used for surface treatment, 100% of the filler surface can not be covered. Using AlN alone can achieve high thermal conductivity, but the viscosity of the system is very high, which seriously limits the application field of products.
Advantages: high thermal conductivity and stable properties.
Disadvantages: the price is very high. Although boron nitride alone can achieve high thermal conductivity, similar to aluminum nitride, the viscosity of the system increases greatly after a large amount of filling, which seriously limits the application field of products.
Advantages: high thermal conductivity.
Disadvantages: the carbon and graphite produced in the synthesis process are difficult to remove, resulting in low purity and high conductivity of the product, which is not suitable for electronic glue. Because of its high density, it is easy to precipitate and layer in silicone adhesive, which affects the application of the product. It is more suitable for epoxy adhesive.
Advantages: low price.
Disadvantages: easy to absorb moisture in the air, strong viscosity, can not be filled in a large number; Poor acid resistance and easy to be corroded by acid in general limit its application in acid environment.
α- Alumina Powder (acicular)
Advantages: low price.
Disadvantages: low addition. In liquid silica gel, the maximum addition of ordinary acicular alumina is about 300 phr, so the thermal conductivity of the product is limited.
α- Alumina Powder (spherical)
Advantages: large amount of filling, in liquid silica gel, spherical alumina can be added to 600 ~ 800 phr, the product has high thermal conductivity.
Disadvantages: more expensive, but lower than boron nitride and aluminum nitride.
Advantages: good particle size and uniformity, suitable for the production of thermal conductive silicone grease.
Disadvantages: low thermal conductivity, not suitable for the production of high thermal conductivity products; It is light in weight and strong in viscosity, so it is not suitable for potting.
Quartz Powder (crystalline)
Advantages: high density, suitable for potting; Low price, suitable for mass filling, reduce cost.
Disadvantages: low thermal conductivity, not suitable for the production of high thermal conductivity products. The density is high, which may cause stratification.
In a word, different fillers have their own characteristics. When selecting fillers, we should make full use of the advantages of each filler, use several fillers to mix and play a synergistic role, which can not only achieve high thermal conductivity, but also effectively reduce the cost, and ensure the miscibility of fillers and silicone matrix.
