The core of adjusting the sintering process to ensure complete sintering is precise control of temperature, holding time, heating rate, and protective atmosphere. Optimizing these parameters can effectively promote the recrystallization of magnesium oxide grains, forming a dense insulating structure.
1. Temperature and Holding Time Control
Sintering Temperature: Must be stable at 800–1000℃, 900±50℃ recommended;
Holding Time: Not less than 1 hour, to ensure sufficient recrystallization, it is recommended to extend to 1.5 hours;
Judgment Criteria: Too low a temperature (<800℃) or insufficient time will prevent grain growth, resulting in a loose powdery state.
Practice shows that holding at 900℃ for 1.5 hours can increase the density of magnesium oxide by 12%, significantly enhancing its insulation stability.
2. Heating and Cooling Rate Management
Heating Rate: Controlled at ≤5℃/min to avoid stress cracks between the shell and filler layers caused by thermal shock;
Cooling Method: Natural cooling with the furnace to <200℃; water cooling or air cooling is strictly prohibited;
Equipment Requirements: Use an intelligent sintering furnace with PID control to achieve segmented temperature control and curve recording.
Rapid heating or cooling can lead to structural defects. Even if electrical tests pass in the short term, the long-term operational risk is extremely high.
3. Protective Atmosphere Optimization
Recommended Atmosphere: High-purity nitrogen (≥99.99%) or vacuum environment;
Oxygen Content Control: <100ppm to prevent oxidation of metal leads or carbonization of magnesium oxide at high temperatures;
Gas Flow Rate: Continuously introduce inert gas to ensure no moisture or impurities remain in the furnace.
An inert atmosphere improves grain bonding quality and reduces micropore formation, which is a key guarantee for high-end applications.
4. Process Validation and Data Traceability
|
Validation Item |
Method |
Acceptance Criteria |
|
Complete Thermal Control Curve |
Automatic recording by intelligent furnace |
Temperature, time, and rate are fully traceable |
|
Metallographic Analysis |
Sampling and observation of grain state |
Grains are significantly grown and densely arranged |
|
Hot State Test |
Insulation test after 30 minutes of operation with power off |
≥200 MΩ (500V DC) |
It is recommended to retain process parameter records and test reports for each batch to facilitate quality traceability and continuous improvement.
