FOX轻型石英晶体，美国福克斯公司凭借着精湛工艺打磨出高质量的石英晶振，并因此一举成名，成为当下最受欢迎的元器件制造商之一，随着行业的快速发展，福克斯公司不断优化与迭代自身的产品，因而在市场上获得更多的机会，为了更好满足用户的需求，对于产品极致的追求，使得FOX公司不断突破自我，走向新的创新之路，也成就更加伟大的福克斯。

石英晶体的“老化”导致频率随时间变化，可能必须采取这种影响由客户在设计电路时考虑取决于需要实现。石英老化的主要原因有两个晶体，一个是由于传质，另一个是因为强调.

质量转移

设备封装内的任何不希望的污染都可能将物质转移到晶体中或从晶体中转移出来，导致将改变频率的石英坯的质量设备的。例如，用于安装石英坯件会产生“排气” 会在惰性气体中产生氧化物质密封的水晶包装里的空气生产过程必须得到很好的控制。理想情况下制造方法尽可能干净，以消除任何效果并给出良好的老化结果。

强调
这可能发生在晶体的各个组件中从石英坯料的加工环氧树脂安装粘合剂，晶体安装结构以及器件中使用的金属电极材料的类型。加热和冷却也会由于不同膨胀系数。系统中的应力通常随着系统放松而随时间变化，这可能导致频率的变化。
实践中的老龄化
当观察晶体的示例老化测试结果时，可以看出，频率的变化通常是在第一年最伟大，并随着时间的推移而衰退。它必须然而，请注意，例如，如果指定了设备每年最大±5ppm；这并不意味着衰老5年后为±5ppm×5年，即±25ppm。在实践中，示例的±5ppm老化装置可能仅为±1ppm至运行第一年±2ppm，然后减少随后几年。对于10年内最大±10ppm的石英晶体谐振器老化，通常使用通用“指南”尽管在现实中它通常比这个要少得多。是的甚至无法预测设备的确切老化在同一时间由同一批石英将表现出略微不同的老化特性。
生产过程必须从零件到部分，来自石英坯料的制造，电极尺寸及其位置，用于安装石英及其固化热剖面，都有轻微影响在频率上。设备可能老化为负或正取决于内部原因一个批次往往遵循类似的结果。一般来说在90%以上的制造零件中，老化效应是负面的。

This can occur within various components of the crystal from the processing of the quartz blank, the curing of the epoxy mounting adhesive, the crystal mounting structure and the type of metal electrode material used in the device. Heating and cooling also causes stress due to different expansion coefficients. Stress in the system usually changes over time as the system relaxes and this can cause a change in frequency.

Ageing in practice

 When looking at example ageing test results of crystals, it can be seen that the change in frequency is generally greatest in the 1st year and decays away with time. It must be noted however that for example if a device is specified at ±5ppm max per year; it does not follow that the ageing after 5 yrs will be ±5ppm x 5yrs, i.e. ±25ppm. In practice, the example ±5ppm ageing device may be only ±1ppm to ±2ppm in the 1st year of operation and then reduces over subsequent years. It is common to use a general ‘guiderule’ for crystal ageing of ±10ppm max over 10 years although in reality it is usually much less than this. It is impossible to predict the exact ageing of a device as even parts made at the same time and from the same batch of quartz will exhibit slightly different ageing characteristics. The production process must be consistent from part to part, from the manufacture of the quartz blank, the electrode size and its placement, to the epoxy used to mount the quartz and its curing thermal profile, all have a slight affect on frequency. Devices can age negatively or positively depending upon the internal causes although parts from one batch tend to follow similar results. Generally the ageing effect is negative in over 90% of parts manufactured

Accelerated ageing 

It is common industry practice to use an accelerated ageing process to predict long term frequency movement by soaking devices at elevated temperatures and measuring frequency movement at relevant intervals. It is normal to test crystals using a passive test (i.e. non-powered). The general rule used is that soaking a crystal at +85°C for 30 days is equivalent to 1 year of ageing at normal room temperature. If this test is extended for enough time then the recorded data can be plotted graphically to enable via extrapolation, the prediction of future long term ageing.

Frequency adjustment 

Note that the ageing of quartz effectively changes the frequency tolerance of the crystal and does not directly influence the stability of the quartz over temperature to any great degree as this parameter is dictated by the ‘cutangle’ of the quartz used. If using quartz oscillators that have a voltage-control function such as VCXOs, TCXOs or OCXOs, the output frequency can be adjusted back to its nominally specified value.

The engineer designing a circuit using either a crystal or oscillator will generally know what overall stability figure their equipment must meet over a particular time period. As the tolerance and/or stability of a device decreases then the more important ageing becomes. For example using a TCXO at ±1ppm stability over temperature will require ageing to be kept to relatively small values. However, if the total frequency movement allowance of a design is for example ±200ppm and a device with a rating of ±100ppm is used then a small amount of ageing can effectively be ignored.