Quartz Crystal Production - Lapping / Grinding
Quartz wafers are further processed through a series of mechanical grinding operations known as a lap schedule. This set of process steps is similar to the creation of fine wood furniture where the surfaces of the quartz wafers are incrementally refined during each step. The lapping process has two goals. The first is to remove the damaged layer of the wafers surface caused by the coarse slicing operation. The second is to alter the wafer's thickness to reach the correct frequency required of the resonator. In this way, all stages of the lapping schedule move the wafer toward thinner, more refined product.
Interestingly, after the wafers have been processed through the slicing and lapping operations where they have received individual processing, they must then be reassembled into loaves to be batch ground on their edges by the rounding operation. The process of rounding shapes the resonator loaf into a precise diameter to not only accommodate the mounting of the crystal resonator into its enclosures, but establish the plate geometry for the support of the desired mode of frequency vibration while strongly suppressing the many possible unwanted modes. Rounding, though simple in appearance, is a critical operation in that an excessive grinding rate can cause "twinning" of the quartz crystal rendering it useless. This results in the loss of the entire accumulated value of the proceeding processes.
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