Causes and Countermeasures of poor film material point

2019-08-15

Poor film point is a common problem of coated products. In Japan and Taiwan enterprises, film point is called "spot hole". As the name implies, the point of film material is evaporated to the surface of the substrate along with the vapor molecules of the film material, forming point-like protuberances on the surface of the substrate, sometimes individual points, in serious cases, the fine points of the sheet, even large particles can damage the surface of the substrate.


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The evaporation characteristics of various film materials are different, especially the melting point temperature and evaporation temperature are very different. Material whose melting point temperature is higher than evaporation temperature is sublimation material, which is evaporated directly from solid state; material whose melting point temperature is lower than evaporation temperature is non-sublimation material. Material whose melting point temperature is equal to evaporation temperature is evaporated from solid state to gaseous state and evaporated while melting. It's a semi-sublimated material. Among them, non-sublimation materials are most likely to produce film material points, because the liquid film material will boil when it is heated, and the bubbles in the film material will overflow in the boiling process, so the possibility of splashing film material points will increase. Sometimes there is a big splash when the material is premelting.


When the film material is wet, water vapor escapes during pre-melting or evaporation, spatter will also occur. The following table shows the sublimation characteristics of several commonly used membranes.


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Membrane material is impure and miscellaneous, that is, there are materials with inconsistent melting point temperature and evaporation temperature in the film material, which is also the cause of the film material point.


Improvement ideas: selecting good membrane materials, fully premelting and controlling the rate.

Improvement measures:

1.Selection of Film Materials with Less Impurities

2.Choosing suitable granular film material for easily splashing film material

3.Screen the film with screen before plating

4.Careful premelting, Mgf2 must penetrate the required film material for one evaporation, while Ta2O5 and TiO2 must be thoroughly penetrated.

5.When several kinds of film materials are plated with an electronic gun, the pollution of film materials caused by the doping of film materials and the falling of film slag from the baffle during crucible rotation is prevented. Once the crucible membrane material is found to be contaminated, it should be replaced immediately.

6.Make evaporation boats and crucibles as clean as possible. (Clean diligently).

7. Choose suitable evaporation rate and smooth rate curve. Especially for non-sublimation materials, the evaporation rate should not be high.

8. Dehumidify the membrane material and dry it in a wide room with a Petri dish.


ATS produces related coatings:


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