BAlSi-4 Strip for Electron Beam Brazing for semi-conduct Industry

In the semiconductor manufacturing industry, the chamber of PVD/CVD equipment needs to maintain a certain temperature in order to enhance the adhesion and quality of the deposition to the substrate, and on the other hand, it needs to maintain a high vacuum environment in order to ensure the quality of the deposition and avoid the collision between the gas molecules and the vaporised or sputtered atoms, so the brazing sealing of the chamber parts made of aluminium alloy, for example AA6061, is crucial. Considering that electron beam brazing has a concentrated and controllable energy and a small heat-affected area, electron beam brazing is one of the most important process methods for brazing aluminium alloys in the chambers of semiconductor coating equipment.

The sealing of the chamber of the final product depends on one hand on the adjustment and control of the parameters of the electron beam brazing process to ensure that the brazing material in the brazing interface fully flows and spreads and fills, and on the other hand also depends on the composition of the aluminium alloy brazing material itself, and the control of the gas content (especially hydrogen).

From the above basic needs, we can gain an insight into the basic needs of the electron beam brazing sealing process for brazing materials in vacuum coating chambers of semiconductor equipment:

1. Aluminium-based brazing materials: although the addition of elements such as copper may significantly reduce the melting point range of some systems of aluminium alloys, but because of the strong internal stresses that can lead to thermal cracking, so basically can only be considered as brazing materials of the BAlSi system. Among the AlSi brazing systems, BAlSi-4 has the lowest eutectic melting point. In other words, the eutectic alloying properties allow the brazing material to melt quickly and have the best flow and spreading ability after the temperature reaches the melting point; therefore, all conventional alloying/impurity elements, except for Si, should be consciously controlled in this brazing material;

2. A certain additional amount of Mg to BAlSi brazing materials is one of the unique features of traditional vacuum brazing materials, but is not the first choice for the requirements of this particular application. The additional Mg content in the brazing material will, on the one hand, extend the solid-liquid phase range of the brazing material (making the solidus temperature even lower than that of eutectic filler materials, which may seem to be a positive influencing factor, but it is actually not), but on the other hand, it will disturb the brazing material's properties resulting in high temperature cavitation of Mg vapour, which may cause formation of porosity or even air leakage in the brazing interface.

3. In addition to controlling the Mg content and other alloying impurity elements to ensure the melting point and the vaporization of the brazing melt, it is also necessary to consciously and rigorously control the hydrogen absorption of the melt during the brazing melting process, considering the source. For example, under same conditions, the filler metal molten in summer south China contains more hydrogen than that in winter north China, which might reflected in the brazing quality of the finished products. But this could be intentionally controlled in the foundry process.

Based on our experience in the metallurgical and brazing industry, and our understanding of brazing materials for specific applications, Shanghai Goodhope has specialised in ordering BAlSi-4 brazing consumables for electron beam brazing applications for domestic replacement.

Specific specifications  available from SHANGHAI GOODHOPE are:

2. BAlSi-4, H18, T0.52xW50, coils