Common Problems Of Vacuum Coating Products

- Jan 23, 2019-

Common problems of vacuum coating products


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Common problem, part of the coating products are caused by the coating process, the part is a former project legacy of bad, the final quality of the coating is the optical parts processing (especially in the case of comprehensive reflection, polishing, cleaning) to appear bad coating must be comprehensive consideration, can we truly find the causes of bad, in order to make the effective countermeasures to improve.


I. Film Dirty(also known as white pressure gram)


As the name suggests, the membrane is dirty. In general, the visceral membrane occurs in or outside the membrane. Dirty can include: dirt spot, white mist, oil spot, fingerprint, saliva spot, etc. (dust spots and white fog)


As the name suggests, the membrane is dirty. In general, the visceral membrane occurs in or outside the membrane. Dirty can include: dirt spot, white mist, oil spot, fingerprint, saliva spot, etc. (dust spots and white fog)


Improvement measures:


1) The lenses that are sent to be washed, washed or polished should not have excessive bad adhesion;

 2) The cleaning rate or the wiping rate of the lenses should be enhanced;

3) For the better arrangement of the mirrors with the upper and rear umbrellas, the pollution shall be prevented;

4) Develop good habits of operators to prevent and control lens contamination (fingerprints, drool spots and others);

5) Accelerate the replacement cycle of vacuum chamber guard plate;

6) Gas pipe is clean to prevent pollution during gas filling;

7) Initial exhaust anti-eddy (turbulence), initial inflation anti-overshoot;

8) Avoid oil pollution, water vapor (edge grinding, ultrasonic cleaning) during lens placement and handling.


In addition: working environment into a clean workshop

Also: coating machine operation panel and the host separated, reduce the host produced harmful substances pollution lenses.


Among them: 1, gray spot dirty

 phenomenon: lens film surface or internal some points (not film material points) some can be erased, some can not be erased. And there's a little bit of delamination.



1. The vacuum chamber is dirty. At the beginning of vacuuming, the air eddy current will bring the dirty ash of the vacuum chamber bottom plate and guard plate to the lens to form the ash spot layer. (inside of the film, cannot be erased, there will be point fall off from the film)


2, mirror ring or disc dirty, floating point dust, under the action of ion beam attached to the lens to form a layer of ash. (inside of the film, cannot be erased, there will be point fall off from the film)


3. There are dust spots on the umbrella of the lens, and there is no inspection and selection on the umbrella. (inside of the film, cannot be erased, there will be point fall off from the film)


4. Environmental pollution after plating is the main cause of the coating dust spots, especially when the lens is hot, it is easier to absorb dust, and it is difficult to erase. (outside of the film)


5. The air inlet of the vacuum chamber is dirty, the air is too much at the beginning, the air filter is dirty, and the lens temperature is too high during the air filling, which is also the reason for the poor dust spots outside the lens membrane. (outside of the film)


6. Dust pollution caused by operators (inside and outside of the film)


7. Excessive dust in the working environment.


Improvement ideas: eliminate dust source


 Improvement countermeasures:


1. The working environment shall be transformed into a clean workshop, which shall be implemented in strict accordance with the clean workshop standards.

2, as far as possible to do a good job in environmental hygiene. Make the most of a clean bench.

3. Clean the vacuum chamber periodically and keep it clean.


Among them: 2. White mist outside the membrane

Phenomenon: after coating film is finished, the surface has a few light white mist, with acetone or mixed fluid wipe, can have brush more serious phenomenon more. With cerium oxide powder to wipe, can erase or reduce, (also known as: wipe pressure grams) analysis: the causes of the white fog outside the film is more complex, the possible causes are:

(1) Film structure: the cylindrical structure of the outer membrane is loose, the outer membrane is too rough;

(2) , evaporation Angle is too large, rough membrane structure.

(3), temperature difference: lens cover when the internal and external temperature difference is too large

(4), moisture; After the lens out of the cover put the environment moisture

(5), the vacuum chamber Polycold thawing water vapor overweight

(6), evaporation in oxygen is not complete, the film structure is not uniform,

(7), the stress between the film and the film


Improvement ideas: there are many causes of white mist outside the membrane, but some of the characteristics, as far as possible. The main idea is to make the membrane more compact and smooth, which is not easy to adsorb, and to improve the environment to reduce the adsorbed objects.


improvement measures:


(1) Improve the film system, add silica to the outer layer, make the film surface smooth, not easy to adsorb. Improve the environment (dry and clean) when the lens is put out.

 (2) Reduce the lens temperature (extend the cooling time in the vacuum chamber) to reduce the temperature difference and stress.

(3) Improve oxygenation (increase), improve membrane structure.

(4) Decrease evaporation rate and improve columnar structure

(5) Ion-assisted coating improves the film structure

(6) Add polycold's small filling valve to defrost (its function is to remove moisture in time)

(7) Improve evaporation Angle from evaporation source and fixture.

(8) Improve substrate surface roughness.

(9) Note the vacuum degree of polycold as it thaws.


Among them: 3. White mist inside the film

White mist is formed in the film, which cannot be removed by wiping method.


Possible causes:

(1) substrate dirty, engineering residues before attachment

(2), lens surface corrosion pollution

(3), between the film material and film material, film material and substrate mismatch.

(4) oxides are not oxygenated enough.

(5), the first layer of zirconia film materials, may have a white halo phenomenon on some substrates

(6), before the substrates into the cover (after cleaning) by moisture pollution

(7), cleaning or wiping bad, cleaning traces, cleaning traces

(8), dirty vacuum room, water vapor

(9), environmental humidity


Improvement ideas: the substrate itself may be the main problem, coating is to make up, coating itself z* large may be the problem of film matching.


improvement measures:


1)Improving film structure, the first layer does not use zirconia.

2) to minimize the opening time of the vacuum chamber; to prepare the cleaning and coating of the vacuum chamber within the shortest time;

 3) after the vacuum chamber is changed and cleaned, it’s better shall be able to vacuum cover and bake; the vacuum chamber parts shall be dry and clean.

4) improve the environment

5) Properly protect the lens on the umbrella before entering the cover from contamination.

6) Improve the cleaning and wiping effect.

7) Improve membrane matching (consider using Al2O3 for the first layer)

8) Improve membrane oxygenation and evaporation rate (reduce)

9) Expedite pre-engineering process. The protection of finished smooth surface is strengthened before engineering.

10) Polished finish, must be immediately clean, no polishing powder or other impurities adhere to dry knot.