What is the Density and Thickness of a Quartz Crystal?
The density of quartz is: 2.648 g/cm³
The most common diameter of a quartz crystal is 14 mm, which is seen with Inficon, Balzers, Satis, Maxtek, Sycon, and Intellimetrics type crystals. However 12.5 mm is the second most common size and this is seen with Ulvac type crystals.
The average thickness of a crystal is: 0.01076″ at the center. Quartz crystals aren’t flat in shape rather they are contoured or convex. The typical shape of a crystal is described as Plano-Convex. Meaning the crystal is flat on one side and curved on the other side. This can be seen in the illustration below.
The reasoning for this shape deals with the natural property of resonance. Since a quartz crystal has natural frequency resonance, the best method of harnessing this energy is to concentrate the energy at the center of the crystal. This is done by contouring the crystal so vibration occurs at the center-most point of the crystal wafer. By concentrating the resonance to the center of the crystal, mass-frequency changes are detected more reliably.
Contrary to a commonly held belief, the orientation of the plano or convex side with relation to the crystal face does not matter. In other words, there is no appreciable difference whether the plano or convex side is used to measure the deposition process.