In the metal evaporation industry, the material used to prepare the evaporation source must have the following properties I 21]:
(1) With appropriate resistivity and resistance temperature coefficient, the vessel resistivity during aluminum evaporation is between
1 ~ 151an · m and 0.5 ~ 48v-o · RN in other applications;
(2) Excellent heat resistance, for example, the temperature of aluminum evaporation is about 1450 "C;
(3) Excellent heat resistance and impact resistance. The evaporation container must withstand multiple cold and heat cycles during use. When powered on
Acute heat may occur in the initial stage of;
(4) Excellent corrosion resistance to molten metal;
(5) Having sufficiently high mechanical strength;
(6) It has good wettability with the plating metal melt at high temperature;
(7) High purity, especially for vacuum coating of electronic devices;
(8) Easy to machine;
(9) The vapor pressure of the evaporation vessel material is extremely low;
(10) Low manufacturing cost;
For most metals, the graphite evaporation boat can react with many other metals at high temperatures to form carbonization
The object causes flowering, blistering and complete destruction, which affects the service life of the evaporation boat. Later, researchers adopted
Various methods apply one or more layers of anti-corrosion Antioxidant coating [22-241] However, in the process of use, there are also problems such as the coating falling off, damage, and short service time. This is because there are residual stresses between the coating and the graphite matrix due to the mismatch of physical parameters during the preparation of the coating for graphite crucibles. When the finished product works in the cold and thermal cycle environment, the cracks expand and grow in the places where the stress is concentrated, and eventually the coating falls off. Because hexagonal BN has the same physical properties as graphite The crystal structure and properties are very similar, and the physical parameters of the two are relatively matched. Hexagonal BN is an excellent insulator. After it is coated on graphite matrix, the problem of large residual stress can be basically solved.