Analysis of Densification and Shrinkage of Ceramic Layer
Vacuum electronic devices are complex systems that rely on the precise assembly of multiple components, including ceramic and metal parts. These devices often require high-accuracy manufacturing, with dimensional tolerances typically in the micron range. The integrity of the vacuum device's shell is crucial, as it is usually formed by welding ceramic and metallic elements together. The flatness of the ceramic component plays a critical role in ensuring proper welding quality and maintaining a hermetic seal. Due to the strict requirements for air tightness, the manufacturing process must carefully control the flatness of the ceramic parts throughout the production cycle.
Several factors influence the flatness of ceramic components. One key factor is the shrinkage rate of the green ceramic tapes during the sintering process. If the shrinkage rates between layers are mismatched, it can lead to significant warping or deformation. Another important factor is the precision of the sintering system used for the ceramic tubes, as improper temperature control can affect the final shape and flatness. Additionally, the distribution of metallization patterns across large ceramic areas also impacts the overall stability and flatness of the component.
The designed ceramic ring consists of five layers of ceramic tapes laminated together and bonded during the sintering process. When the shrinkage rates of these layers differ significantly, the resulting warping becomes more severe. However, if the shrinkage remains within an acceptable range, the degree of warping can be significantly reduced. This highlights the importance of controlling the material properties and processing conditions to achieve optimal flatness.
In a freely shrinking ceramic layer, there is no internal stress, and the shrinkage occurs uniformly due to densification. However, in a two-layer co-fired composite, each layer experiences constrained deformation because the contraction of one layer affects the other. If the shrinkage rates are not well-matched, internal stresses develop. Under such conditions, the laminated structure can only relieve stress through bending or cracking, which may compromise the structural integrity and performance of the device.
To ensure high-quality vacuum electronic devices, manufacturers must pay close attention to the design and processing of ceramic components. By optimizing the sintering process, matching shrinkage rates, and managing metallization patterns, it is possible to achieve the required flatness and improve the overall reliability of the final product.
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