Technology improvement of epoxy resin castable for dry type transformer in China
As a chemical enterprise focusing on the R & D, production and sales of EMC (< 0 > epoxy castables), Julong chemical integrates its own technology and theoretical advantages of cooperative universities, focusing on the field of epoxy castables with fillers. After years of hard work, Julong chemical has gained the leading position in this field and won the recognition of customers and the market. Julong chemical is willing to share technical achievements with its peers to promote the upgrading of China's EMC technology and help EMC products enter the international high-end market.
In EMC (epoxy resin castable), the content of filler is as high as 50% - 90%, so the selection of filler and its performance have a very important impact on the performance of EMC, and play a decisive role in the comprehensive performance of EMC.
Julong chemical uses imported inorganic filler silica. It has the following effects: it can reduce shrinkage, enhance toughness, enhance wear resistance, reduce water absorption, improve thermal deformation temperature, improve thermal conductivity, reduce thermal expansion coefficient, reduce cost, etc. But there are also shortcomings, such as increasing viscosity, improving dielectric constant, and so on. How to use its strengths and overcome its weaknesses, not only maximize the excellent characteristics of silica powder, but also minimize its negative effects, which is the core problem of EMC filler technology. Julong chemical successfully overcame this problem by studying the shape, type, particle size distribution, stacking density and other aspects of fillers, as well as innovative filling technology.
First, the filling amount is appropriate.
In EMC, the main role of fillers is to improve the thermal conductivity, reduce the coefficient of thermal expansion and molding shrinkage, can also play a strengthening role, improve reliability, reduce costs, so many chemical enterprises try to improve the filling amount of fillers. However, increasing the filling amount will bring at least three negative effects.
First, increase the viscosity of EMC, reduce the formability, impact on the gold wire of IC, affect the reliability.
Secondly, increasing the melt viscosity of EMC results in the decrease of fluidity, which makes it difficult to effectively reduce the thermal expansion coefficient of EMC. Third, increase the precipitation of EMC. Therefore, the filling amount should be selected appropriately. It is precisely because of the selection of appropriate filling amount and the unique leading formula that the EMC products produced by Julong chemical have the following characteristics. First of all, it has high formability. With Julong EMC's < 0 >, it can be molded at one time, without grinding, repairing and sizing, and with smooth appearance and bright color. Secondly, the linear thermal expansion coefficient is as low as 44e-06 (1 / ℃). Thirdly, it has low precipitation. On the one hand, after 6 months of storage, the precipitation is still lower than the industry standard of 10%; on the other hand, there is little precipitation left on the wall of pouring equipment. In the market, this feature is very popular, because it greatly saves costs for customers.
Secondly, the composite inorganic filler has a reasonable ratio.
The proportion and particle size distribution of composite inorganic fillers have great influence on the spillability of EMC. Julong chemical researchers are constantly studying the optimal ratio and particle size distribution of composite inorganic fillers to reduce overflow. Through unremitting efforts, Julong chemical has developed an EMC filler system with reasonable proportion and particle size distribution, which can greatly reduce the generation of EMC flash and effectively reduce the overflow of EMC.
Thirdly, high thermal conductivity fillers such as crystalline silica are used.
Generally speaking, with the increase of filler content, the thermal conductivity of EMC will be continuously improved, and the thermal conductivity of crystalline silica is higher than that of molten silica. Julong chemical uses crystalline silica and other high thermal conductivity fillers, which are prepared by high filling technology, effectively improving the thermal conductivity of EMC. The produced EMC products can fully meet the high thermal conductivity requirements of high-power electrical products, which is not only conducive to the heat dissipation and heat exchange of transformer products, but also can cope with the severe situation of short-term load. The filler with high thermal conductivity also makes the EMC heat resistance of Julong chemical reach class F (test standard: iec85).
People in the industry know that packing technology is the core technology of EMC technology. In foreign countries, silicon dioxide filler was used earlier to manufacture EMC, and the development is relatively fast, which has occupied the main high-end market. In the face of new development opportunities and challenges, Julong chemical is willing to work with its domestic counterparts to continue to strengthen the research and improvement of filler technology, and make unremitting efforts to make our EMC products share the high value-added high-end market.
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