Separation of molybdenum disc and monocrystalline silicon from failed silicon molybdenum components by chemical method
Molybdenum disc is the support of contact electrode and silicon rectifier of silicon controlled silicon element. With the rapid development of electronic industry, the output of silicon molybdenum components is also increasing. According to statistics, there are dozens of tons of silicon molybdenum components in China every year. Correspondingly, a considerable number of failed silicon molybdenum fabrications are replaced every year. At present, there are more and more invalid silicon molybdenum fabrications in the domestic market. If it can be recycled and reused, it will have a good economic value for the country and the unit. One surface of the failed silicon molybdenum components is fused with aluminum, silicon, copper and nickel coatings, which is difficult to separate. In the past, no better separation method has been found, which has affected the recovery and use of this part of molybdenum discs. The former electrolysis methods, nitrate melting method, alkali boiling method. All lost the value of recycling due to the destruction of the structure and properties of molybdenum discs in the treatment process, and the longer treatment process, higher product cost and lower quality, In order to recover and utilize this precious metal molybdenum disc, this paper studies it and finds an effective chemical recovery process. This process can well separate molybdenum element from monocrystalline silicon. After chemical treatment, the molybdenum disc can still have the original properties, After testing, analysis and trial, it is proved that the regenerated molybdenum disc has the physical and chemical properties of the original molybdenum disc, the product quality is very good, and has considerable economic and technical effect.
1、Regeneration method
Raw materials：In the process of use, silicon molybdenum fabrications become invalid due to the breakdown of monocrystalline silicon layer, loss of the ability to control current and no rectification effect. This is the raw material used in this process. The outermost layer is silicon layer, and aluminum alloy is used to connect the silicon layer and molybdenum layer to form a solder layer, which firmly adheres the silicon layer to the molybdenum disc. As a result of high temperature, the surface of molybdenum disc is infiltrated layer, which is the impurity layer to be removed.
2、Regeneration and separation method
In the process of separation and regeneration, both the impurity layer on one side and the molybdenum layer on the other side should be protected. In order to obtain molybdenum wafer products, according to the difference of chemical properties of silicon, molybdenum, aluminum and other elements, a new type of regeneration separation agent is selected. The separation agent can only react with silicon, aluminum, copper and other impurities in the impurity layer under strictly controlled conditions, but not with metal molybdenum. In this way, the impurity layer is effectively removed and the metal molybdenum layer is protected. In the process of separation and processing, molybdenum discs always keep the original physical and chemical properties, and then after certain machining, they become re-use products. We call this method chemical regeneration and separation.
