Effect of Gas Selection on the Appearance of GTMS Products

In here, four different atmospheres were chosen with progressively increasing oxidizing power. (See figure below) After sealing under these four atmospheres, the appearance of the sealing area of the base shows in Figure. In the case of 1%H2-N2 atmosphere, the leakage of the sealing part is high; this may causes by the oxide film reduced in this atmosphere, and the molten glass cannot sufficiently wet the metal surface to make the seal (page 7 - 9).

Appearance after sealing under different atmospheres:

(a) 1%H2-N2
(b) 1.5%H2-1%H2O-N2
(c) N2
(d) 1%H2O-N2 atmosphere

When the sealing is in a pure N2, a circle of regularly distributed glass is often seen in the sealing area of ??the base, as glass splash phenomenon, as shown in Figure (c). Pure N2 is generally considered an inert atmosphere. In fact, even high-purity N2 contains trace amounts of water and oxygen, a slightly oxidizing atmosphere instead of an insert gas atmosphere. In this atmosphere, the phenomenon of glass splashing during sealing is unavoidable. When sealing in an oxidizing 1% H2O-N2 atmosphere, the glass splash phenomenon is more serious, and it can even be seen that the glass has overflowed outside the sealing area of the chassis, as shown in Figure (d). Only when it is sealed in a weak reducing atmosphere of 1.5%H2-1%H2O-N2, there is no glass splash on the surface of the chassis, with a good bonding, as shown in Figure (b). These results show that as the oxidizing property of the sealing atmosphere increases gradually, the glass spatter becomes more and more serious until the glass overflows.

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