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How to choose the most suitable crystal oscillator？

Coating technology is advancing rapidly，For coating engineers，It is not easy to choose the best crystal oscillator according to different coating processes。Here are some suggestions for your reference：

1）When plating low stress film materials，Choose gold-plated crystal oscillator

The most common coating is platingAl、Au、Ag、Cu，These film layers have almost no stress，Coating can be done at room temperature。The film layer is relatively soft，Easy to scratch，But it will not crack or have a negative effect on the substrate。Suggest using gold-plated crystal oscillators for the above-mentioned coating，empirical evidence，It can be plated on gold-plated crystal oscillators60000Ekin and50000The thickness of Eyin。

2）Use silver plating or silver aluminum alloy to coat high stress film layer

Ni、Cr、Mo、Zr、Ni-Cr、Ti、Stainless steel and other materials are prone to high stress，The film layer is prone to peeling off or cracking from the crystal substrate，Resulting in sudden jumps in speed or a series of sudden irregular positive and negative changes in speed。sometimes，These situations can be tolerated，But in some cases，Will have adverse effects on the power control of the evaporation source。

3）Coating dielectric optical film on silver aluminum alloy crystal oscillator

MgF2、SiO2、Al2O3、TiO2Due to its excellent optical transparency or refractive index properties, the film material，Widely used in optical coating，But these film materials are also the most difficult to monitor，Only when the substrate temperature is greater than200degree-hour，These film layers will have very good adhesion with the substrate，So when these film materials are coated on a water-cooled substrate crystal oscillator，During the condensation process of the film layer, significant stress is generated，Easy to make the crystal oscillator1000Within the scope, it will become ineffective。

At this moment，Choosing alloy crystal oscillators would be the best choice，Will greatly reduce frequency modulation opportunities。Laboratory display，Monitoring magnesium fluoride using alloy crystal oscillators，The effective lifespan is longer than that of gold-plated ones100%。If the temperature of the cooling water is adjusted from20Increase the degree to50linear measure，The lifespan of the crystal oscillator can be further doubled。

seven﹑Installation and Precautions and Techniques for Crystal Crystals

With the increasingly strict demand for coating specifications and indicators，Relying solely on light control is no longer sufficient to meet the requirements，Crystal oscillator control has become an essential auxiliary or control method for coating﹐How to correctly and effectively use crystal oscillators has become a key factor in ensuring coating quality。So in order to maximize the lifespan of the crystal oscillator，Here are some methods and techniques for your reference：

1.Always using a camera to grip the edge of the crystal oscillator，Do not touch the center of the crystal oscillator。
Because the active center of crystal oscillator vibration，Any gray layer，Oil stains can reduce the vibration ability of crystal oscillators。Before using the new crystal oscillator, it should be soaked in alcohol(Pure analysis is sufficient)Immersion in the middle1About minutes，Afterwards, use plastic tweezers to pick up the alcohol and wipe it clean with dust-free paper or a clean silk cloth，At the same time, use dust-free paper or silk cloth dipped in alcohol to wipe the crystal oscillator holder clean，Before assembling the crystal oscillator, use a balloon to blow the crystal oscillator、Possible residual dust on the contact spring of the crystal oscillator base and probe、Blow off paper scraps, etc﹐After installing the crystal oscillator, blow the surface of the crystal oscillator again with a balloon，Remove scattered dust。(Someone suggests blowing the surface of the crystal oscillator with low-pressure filtered nitrogen or oil-free air，Remove scattered dust﹐I think blowing balloons is enough﹐Convenient, economical, and fast。)Remember not to directly touch the crystal oscillator with your fingers to avoid leaving oil stains。

2.Keep the crystal oscillator clean。Do not let the powder of the coating material come into contact with the front and rear center positions of the crystal oscillator。Any particles or ash layer between crystals and fixtures will affect electronic contact，And it will also generate stress points，Thereby changing the mode of crystal vibration。

3.After multiple coatings, the surface of the crystal oscillator holder will deposit a thicker film，If it is not removed，The anti sputtering generated by ion bombardment can affect the testing accuracy of crystal oscillators。You can first use sandblasting or sandpaper to remove the film layer，Afterwards, soak it in alcohol5About minutes，If ultrasonic oscillation can be used for cleaning，The effect will be better，Finally, put it in110℃Bake in the oven15minute，Ready to use。

4.Maintain sufficient cooling water to keep the temperature of the crystal oscillator head at20-50linear measure。 If the temperature error can be kept within1-2Within the range of degrees，Better effect。

*impedance，To ensure measurement stability and longer coating life。Adhesion of impedance indicators and electrical contact of electrodes。 *frequency，Verification of initial frequency measurement within a small specification range，To ensure accurate thickness measurement。*Curvature is an electronic test conducted，To ensure resonance stability。Rapid decrease in curvature measurement results with poor stability。 *Visual integration，To ensure maximum crystal lifespan and stability，Check the consistency of electrodes for each crystal，Surface defects，And other defects，Electrode adhesion and contamination。

2、Frequency ensures that the starting frequency is within a small range，Helps ensure accurate thickness measurement for you。
3、Curvature testing，It is to ensure the stability of resonance，Poor curvature will reduce the crystal control chip（Crystal oscillator）Stability of measurement process。
4、Appearance inspection of electrode uniformity for each crystal、Surface defects、And other appearance defects have been inspected，Thus eliminating poor electrode adhesion and possible contamination。