The Six Ways to Improve GTMS Products' Air Tightness
Are you experiencing air tightness loss in the subsequent process after sealing or use?
One of the key components of GTMS is airtightness. Sometimes, the reduction of air tightness won't be necessary to happen right after the seal is completed but also occurs in the following process, like electroplating, paint curing, etc... Due to the particularity of the sealing process, there are many factors that need to be controlled. Reduction of product air tightness after subsequent process is normally caused by the glass sintering process.
The metal treatment before sintering
To eliminate high density bubbles at the interface between metal and glass, the metal parts should be annealed, decarburized in high temperature and wet hydrogen under atmosphere before sintering. This process can improve the strength of the material in the subsequent sealing and electroplating process, but also reduce chronic air leakage.
Protective gas sources for oxidation
To achieve a better sealing quality, oxidation before sintering is important. A certain thickness of low-valent oxides (FeO, Fe3O4) can be formed in an atmosphere furnace. In this process, a stable nitrogen source (nitrogen with a controlled amount of moisture) is required as a protective gas source. In here, controlling the dew point is controlling the thickness of the oxide layer. If the oxide layer is too thick (caused by gas source or dew point control), it will form a porous path (causing gas leakage) or even peel off the glass from the metal.
Oxidation level of metal surface
GTMS is an interaction between glass and metal oxides; the quality of glass sealing depends on the quantity of the oxide layer on the metal surface. The melted glass will penetrate the metal surface and the oxide layer should be firmly adhered to the metal substrate, while partially dissolved in the glass to form a transition layer for an airtight seal. Thus, the amount of the oxidation can be controlled precisely (sufficient but not excessive). In this process, the oxidation quality is not only affected by the atmosphere inside the furnace, but also the oxidation time and temperature.
And there are other reasons for poor sealing strength:
Material selection (glass, glass powder, inner/outer metal)
Uncontrolled heating/cooling (heat up too fast, poor across belt temperature uniformity)