1. What is the aging of the crystal oscillator?
　　Aging refers to the change in the frequency of the crystal. It can change in both positive and negative directions. The aging process is caused by the change in the frequency of the oscillator used by the crystal.
　　Aging will be mainly affected by two factors, namely pollution and pressure. Experiments have shown that contamination of crystal wafers will bring about negative changes, while excessive pressure will usually bring about positive changes.
　　When the crystal chip is mounted on the chassis, it is likely to be squeezed or twisted due to the support structure, which will bring pressure to the crystal chip, which will release or relax over time, leading to a positive frequency shift. When assembling the crystal, the proper equipment method and proper chassis help to reduce and reduce unnecessary stress. The installed crystal can be heat treated to accelerate the movement and alleviation of this pressure.
　　Contamination of the wafer will occur in many processes of crystal production. Contamination of the wafer surface can cause negative frequency shifts due to excessive load. Contamination can be reduced by improving the cleanliness of the production process and cleaning the wafers in each production process.
　　Crystal can be "aged in advance" to reduce the aging effect to a certain extent. Because the aging of the crystal will show a logarithmic curve characteristic. Most crystal aging will occur within the first year. The frequency of the crystal changes more and more rapidly in the first year than in the second and subsequent years.