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What is the advantage of AlN over BN in other applications?
2014-11-20
 Comparison between AlN & BN
n  Discussion with client in Italy, in June, 2013
n  Author: GM. Thomson in Thrutek.
 

 

 

1. Boron nitride: commercial name “h-BN”. In past, most of thermal conductive plastic makers introduced h-BN as thermal conductive filler due to h-BN had been mass production for several applications and it has much more suppliers and production quantity and was well-known than aluminum nitride.

 

 

2. The advantages of h-BN: 

 

h-BN is soft and lower density.

 

 

3. The disadvantages of h-BN:

 

a. Similar hexagonal crystal structure as graphite, its powder is flake shape.

 

b. Flake form makes worse flow ability as mixing with resin, this make it very difficult to be compounded with high filling rate to enhance thermal conductivity. And worse flow ability is not good for injection molding.

 

c. Meanwhile, its hexagonal structure makes its thermal conductivity and expansion become anisotropic. h-BN has very low thermal conductivity on Z direction about only 20-30W/K.m, but very high thermal conductivity about 600W/k.m on XY plane. And it could be defined average thermal conductivity by hot disk method as about 130W/k..m((XY*Z)^1/2), So it is lower average thermal conductivity than AlN theoretically. Some suppliers emphasize the anisotropic characteristics is the advantage of h-BN, but most applications Z direction is more important.

 

d. Due to its soft property, it makes weaker mechanical strength on filling engineering plastics than using AlN powder. Currently, we are also promoting AlN powder to one very big Taiwanese company for similar application, they developed new products by using h-BN before, but they intend to give up h-BN due to the strength cannot reach their requirement.

 

 

4. The price issue:

 

a. The price of h-BN should be higher than AlN. So we had developed some customers in Japan that they are trying to replace h-BN by AlN.
 

b. The price of h-BN is varied by particle size, crystallinity and purity. Small particle size is worse crystallinity and much lower price. Worse crystallinity also responses worse thermal conductivity. Maybe your customers are using small particle size of h-BN.

c. Even small size of h-BN supplied from China should be still higher than 40USD/kg. But small particle size might make much lower flow ability and much lower thermal conductivity on filling plastic application due to much larger specific surface area and its natural flake shape. So few customers are using it for thermal conductive plastics, and it could be replaceable by Alumina.

 

 

5. The main disadvantage of AlN powder on engineering plastics

 

a. The hardness is higher than h-BN(please noted c-BN is much higher hardness than AlN. Its higher hardness could be easier to wear off the screws of injection molding machine, but this influence could be reduced as it is compounded in relative lower viscosity than by using h-BN due to AlN is not flake shape. And we think the advantages of AlN still more than h-BN on filling plastic applications. Our customers had proved AlN could make higher thermal conductivity and near isotropic, better mechanical strength, better adhesion (when applied on insert moding ),  lower thermal expansion, and lower cost than h-BN.  

 

 

6. A brief comparison table as below: 

 

 

AlN(Thrutek)

h-BN

Thermalconductivity(W/K.m)

 

 

 

average

300~320

~130

direction isotropic anisotropic

 

Thermal expansion

 

small and isotropic

high and anisotropic

 

Shape

 

irregular

flake

 

Hardness

harder

softer

 

color

 

gray

white

 

Flow ability

 

good

worse

 

Filling possibility(rate)

 

high

low

 

Cost

middle

high(bigger size)

 

Strength on application

better

worse

Adhesion* on application

 

good

worse

 

* The adhesive strength of mixing with adhesive resin or on insert molding.

 

 

7. The application of AlN powder on engineering plastic is still quite new. Thrutek is very interesting to this application and making many efforts on it in near years, because we think this application will be very potential in coming future.

Add:R600A, No.12, Nan-Ke 2nd Rd. Southern Taiwan Science Park,Tainan City, Taiwan, 74147.