National Standard for Tungsten Heater——Life Time Test Requirements

Oxidation of tungsten heater refers to tungsten wire react with oxygen in the air, it could lead to breakage, thus shortening its life. Tungsten has a high melting point, high resistance, high strength, low vapor pressure, which is suitable for the heating element. The film material (aluminum, chromium, indium, etc.) will evaporate under vacuum plating machines, high vacuum, the heating element, so that the film becomes shiny and beautiful.

Generally speaking, the life time of the tungsten heater is more than 300 times, but if done incorrectly, wolfram heater will change color into yellow, and then the central section of the wolfram heater will produce irregular cracks which cannot be used in the normal evaporation process of aluminum. A good control of wolfram heater life time can greatly reduce the cost of producing, it also can ensure the quality of the subsequent deposition to some extent.

According to the National Standard SJT 11063-1996, life time test requirements of wolfram heater are divided into three kinds on the basis of different test equipment.

I: Test equipment: No. 379 493 vacuum equipment of ULVAC JAPAN LTD:

1. The Degree of Vacuum: 1.33 × 10-2Pa.
2. Current: 60 ~ 100A.
3. Voltage: preheat 3.5 ~ 5.0V, evaporation 5.5 ~ 8.0V.
4. Evaporation Time: preheat 18 ~ 21s, evaporate 16 ~ 25s.
5. The Inserted amount of Aluminum: 100 ~ 120mg.
6. Aluminum Wire Purity: 99.99%.

II: Test equipment: DMW-1350 type rotary vacuum coating machine:

1. The Degree of Vacuum: 1.33 × 10-2Pa.
2. Current: 90A.
3. Voltage: 8.0V.
4. Evaporation Time: 1 ~ 1.5min.
5. The Inserted amount of Aluminum:  0.4 ~ 0.7g.
6. Aluminum Wire Purity: 99.45% ~ 99.99%.

III: Test equipment: DM-670F-type vacuum coating machine:

1. The Degree of Vacuum: ≥6.65 × 10-2Pa.
2. Evaporation Time: 0.6 ~ 0.9kA.
3. Evaporated voltage: 120 ~ 170V.
4. Evaporation Time: 1min.
5. The Inserted amount of Aluminum: 0.3 ~ 0.4g.
6. Aluminum Wire Purity: 99.99%.

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