According to the application characteristics of new optoelectronic devices (fiber laser, MEMS wafer packaging), the sealing glass not only to meet the traditional requirements of expansion matching, wetting, sealing strength and sintering process, but also to meet the electrical properties, acid resistance, etc., and in the organic phase of the metal phase multi-phase coordination, laser sealing process and so on, put forward a higher demand.
Glass to metal sealing, through the element diffusion and metal substrate formed a close wetting layer, mostly used in copper, aluminum alloy and other parts of the sealing. In the case of glass-to-metal sealing, a bonding layer is formed by elemental diffusion with the metal substrate, and the substrate is tightly connected together. During the sealing process, metal ions diffuse into the glass, inducing glass crystallization, which can increase the strength of the seal. These diffused ions alter the glass network, leading to stress-driven crystallization and dendrite formation in the glass, which tightly bonds the glass to the metal. Iron ion diffusion into glass solder in Figure 1 below.
Before glass-metal sealing, it is necessary to preheat the metal, so that the metal surface to form an oxide layer, a certain thickness of the oxide film is extremely important for the entire sealing process.
First of all, the oxide film serves as a transition layer between glass and metal or alloy sealing, and it is dissolved in both glass and metal or alloy. Sealing, closely attached to the metal or alloy surface of the oxide in the glass and metal or alloy. Sealing, tightly attached to the metal or alloy surface of the oxide and the glass back to the structure of the gradual change in the formation of a transition layer structure. In this structure and the glass sealing oxide lattice nodes on the metal particles in the more close to the glass when the glass is also more by the glass in the Si ions replaced, thus strengthening the sealing effect;
Secondly, the oxide film can eliminate the air bubbles staying in the interface of glass and metal or alloy, and the air bubbles, if not eliminated, will greatly reduce the vacuum airtightness and pressure strength of the sealing parts, thus reducing the quality of the sealing parts. Of course, the thickness of the oxide film on the sealing of the air permeability, strength, etc. has a vital role. When the oxide film is too thin, it will cause direct sealing between glass and metal base surface, and reduce the strength of sealing. When the oxide layer is too thick, resulting in the metal surface residual thicker oxide film, sealing easy to occur air leakage phenomenon, affecting the airtightness.
If you have any glass-to-metal sealing parts needs, please feel free to contact InSealing.