Crystals in the process of use and storage, the frequency of the crystals with the passage of time is always changing, this is the crystal vibration aging, aging in the direction of no unified rule, most of the drift in the direction of negative. So for those who use crystals of instruments, equipment should be calibrated periodically. The problem is aging measurement, we can't just for one year. So the current widely used the way of equivalent aging: improve the storage temperature, shorten the placement time. The test shows that under the condition of 85 ℃, place the crystals for 30 days, its frequency relative changes quite or more crystals in normal room temperature placed a year of aging. Therefore gb regulation, condition of aging evaluation is: 85 ℃, and 30 days.
Aging is the concentrated reflection of the whole technology level factory. The reason is very complex. It is generally believed that crystal vibration aging of the main causes for attachments to fall off the surface, the stress caused by grinding process microtek piece, shelves and scaffold for the formation of the coating process and the chip and the electrode membrane and the chip, the stress changes between crystals surface adsorption of gases and changes caused by gas leakage on the surface of the electrode, etc. To reduce the aging, from the following several aspects:
One, to ensure the smoothness of the chip, including its edge finish.
Second, deep etching process, should be adopted to ensure damage layer is removed.
Third, be to ensure the cleanliness of the chip, chip to clean again carefully, on the resonance and the shell is to clean.
Four, appropriate thinning the thickness of the membrane electrode, guarantee the coating of tolerance, try to reduce the amount of fine-tuning.
Five, fine-tuning, ensure that the coating and vacuum degree, best for ion bombardment cleaning before coating. Coating process, the temperature of the chip, sputtering speed all have an impact on the quality of the electrode.
After six before and after coating, shelves dispensing, slightly thickened should be performed after high temperature baking, to eliminate the influence of stress. Best baking aging in a vacuum filling nitrogen in the oven.
Seven, the volatiles of conductive adhesive also can affect crystal vibration aging, dispensing at least again after cleaning.
Eight, to prevent the oxidation of the electrode, crystals and shell should be high purity nitrogen filling inside.
Nine, to ensure that the crystals of high and low leakage rate
Ten, customer use state, especially the driving power may also affect the size of the crystals of aging, motivating power, is aging. In the process of machining, should try to reduce the exposure time electrode in the air, to prevent the chip to pollution.
