Aging refers to the continuos change in crystal oscillator frequency with time, all other parameters hold constant. The aging of an AT-cut crystal is mainly caused by two factors:

1) Impurities in the crystal material and on the crystal surface 2) Mechanical stresses between the crystal material and the deposited electrodes

The unique crystal manufacturing process at Quartz Pro minimizes these factors that cause aging.

Impurities

The Quartz Pro process cleans the crystals all the way down to atomic level. Thorough cleaning of both surfaces of the crystal is performed prior to electrode deposition by means of outgassing, UV-ozone cleaning (cracking), and atom bombardment.

Mechanical stresses

A prerequisite for minimized mechanical stress is that the electrodes are deposited slowly in a controlled manner. At Quartz Pro the electrodes are sputtered on with a magnetron sputter and the frequency is measured in parallel. The slow deposition rate in combination with high pressure is imperative in order to minimize mechanical stresses. The electrode thickness is between 50 and 150 nm and can be adjusted by a few layers of atoms, i.e. a few tenths of a nm. Conventional methods make use of evaporation to attach the electrodes and cannot be performed in the same slow controlled manner. After electrode deposition, annealing takes place. The annealing process in high temperature accelerates the compressive stress relaxation.

The result

The result is a crystal oscillator with very low aging. The graph below shows typical aging curves for Quartz Pro’s 10 MHz x-act. All individuals exhibit lower than 1 ppb aging per day.