Boron nitride crucible is usually composed of PBN. PBN ceramics are good at heat resistance, thermal stability, thermal conductivity, high temperature dielectric strength,which are ideal heat dissipation materials and high temperature insulation materials.
Because of its excellent chemical stability, PBN can resist the erosion of most of molten metals. With the features of high temperature insulation, high thermal conductivity and low thermal expansion, it is most suitably to be used under the tough environmental conditions such as the semiconductor manufacturing’s condition. PBN crucible is often used for melting metals and semiconductors. Its operating temperature under vacuum can reach 1800 ℃, and the maximum operating temperature under atmosphere protection can reach 2100 ℃. Generally, it is protected by nitrogen or argon (atmosphere protection is to prevent the crucible’s oxidation).
1. Production process:
(1) The boron-containing gas compound and nitrogen-containing gas are subjected to chemical vapor deposition reaction on the heated mold core under vacuum conditions to obtain the pre-coating;
(2) After the pre-coating is obtained, stop the chemical vapor deposition reaction and keep the temperature unchanged;
(3) After the constant temperature is kept, the chemical vapor deposition reaction continues so as to obtain the pyrolytic boron nitride crucible with pre-coating;
(4) Remove the pre-coating to obtain the pyrolytic boron nitride crucible.
2. Main features:
(1) It has excellent chemical and thermal stability. It has no chemical reactions with most of molten metals and semiconductors at high temperature;
(2) Pyrolytic boron nitride crucible has high density with no pores;
(3) It can be used repeatedly and easy to clean;
(4) It has obvious anisotropy in mechanical, thermal and electrical properties, as well as good microwave and infrared transmittance;
(5) Good insulation performance under high temperature is good.
3. Application:
Because the PBN crucible production has no the traditional hot-press sintering process nor any sintering agent involved, it has a high purity (99.99% or more). The operating temperature under vacuum is up to 1800 ℃, and the maximum operating temperature under atmosphere protection is up to 2100 ℃(generally protected by nitrogen or argon gas). In addition, due to the slow deposition rate, PBN crucibles are quite expensive and the most of its products are in small sizes.
