If improperly used, the advantages of Quartz Monitor Crystals, even high-quality Quartz Monitor Crystals, cannot be fully utilized. How to properly and effectively use crystals becomes the focus to ensure coating quality. So in order to maximize the life of crystals, the following methods and tips are provided for your reference:
Always hold the edge of a crystal with tweezers; do not touch the center of a crystal because at the center of crystal where vibration is intense, any dust or oil may reduce the vibration performance of the crystal. Before use of a new crystal, soak it in alcohol (AR grade is enough) for about 1 minute; then hold it with plastic tweezers and wipe off alcohol with a dustless paper or clean silk cloth; moreover, clean the crystal holder with a dustless paper or silk cloth wetted with alcohol; before installation of a crystal, blow off any possible residual dust and paper debris on the crystal, the crystal holder and the contact spring of probe with a bulb blower; after installation of a crystal, blow the surface of crystal again with a bulb blower to remove loose dust. Remember never directly touch a crystal with fingers to avoid leaving oil.
Keep the crystals clean. Do not allow any powders of coating material to contact the front/rear center of a crystal. Any particulates between a crystal and a holder will affect the contact of electrons and produce stress points, thus changing the pattern of crystal vibration.
Thick film will be deposited on the surface of a crystal holder after multiple coatings; if it is not removed, the back sputtering caused by ion bombardment will affect the accuracy of testing on crystals. You may remove the film by sandblasting or polishing with sandpaper, then soak it in alcohol for about 5 minutes; if you can clean it by ultrasonic shaking, the result would be better; at last, place it in an oven to dry it for 15 minutes at 110℃; then it is ready to use.
Maintain sufficient cooling water to keep the temperature of crystal between 20-50 degrees. If the temperature error can be kept within 1-2 degrees, the result would be better.
Quartz Monitor Crystals are consumables in manufacturing process; it is necessary to replace the degraded crystals in manufacturing process; they should be replaced in following cases:
- ACT; typically based on the criteria as greater than 400;
- Life; separately considered in “increase” and “decrease” cases and depending on the product to be coated; whether the life expires; generally, when the service life elapses from about 99% to 90-92%, it is the time to replace the crystal.
- Rate; when DEV is greater than about 10%, the crystal should be replaced; if the evaporation rate is obviously abnormal, it should also be replaced;
- Surface quality; when the film on the surface of a crystal is lost or peeled, it should also be replaced;
- The sensitivity of a crystal decreases as the its mass increases; therefore, when the coating process is monitored by using a quartz crystal, the coating curve will move toward long wave as the life of crystal elapses.