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Everwide Newsletter-No.99

Experiment § Molded transformer resin

The insulating material of the molded transformer is epoxy resin, and its hardener is divided into two categories; one is the polyamide system; the other is the acid anhydride system, the hardener system is selected according to the infusion conditions. Generally speaking, the polyamide system is suitable for a small infusion, and the amount of infusion is about 2 kg or less. The system is cured at room temperature without heating, but its electrical properties and mechanical strength are worse than the acid anhydride system.

Most injection-molded transformer resins use acid anhydride systems as hardeners. Its advantages are that after the resin is mixed with the hardener, it can be used for a long time, with low viscosity, and is easy to deform. After high-temperature curing, it has good toughness, breakdown voltage, partial discharge, and dielectric constant. It has good tracking resistance, good mechanical properties, high insulation and resistance to high humidity environments, and excellent resistance to thermal shock, effectively reducing the extrusion stress caused by temperature changes on the components. Its disadvantage is that it must be heated to harden.

The quality of injection-molded transformers depends on their vacuum equipment, filling equipment, personnel operations, resin characteristics, and other factors. Especially when the bubbles are not removed, it is easy to cause damage to the voltage, partial discharge, dielectric constant, and mechanical properties, resulting in defects in the finished product. It is an electrical product with stringent production process requirements.

─Author: Mr. Yun-xian, Liu, Assistant R&D Engineer Everwide Chemical


Activity § UV+moisture curing coating adhesive

Coating a layer of Conformal coating on the PCB board to prevent moisture from affecting the circuit board has a long history. Most of the products on the market are hot-baked Silicon resin. Because many small parts on the PCB cause light shadows and blind spots, the application of light-curing resins that require light to cure in this field always have its bottleneck. The FT282 newly developed by Everwide is an acrylic UV+ moisture-curing coating adhesive. It has a dual curing mechanism. The place where UV is not exposed will be naturally cured by moisture. This product is 100% reactive, there is no problem of solvent volatilization, and there is no problem of incomplete curing, which causes poor insulation and low electrical properties. The viscosity of this product is only 110 cps. It can be applied by impregnation or spraying. It has the characteristics of rapid curing, environmental protection, and low volatile organic matter content. The first experience of UV+moisture curing was met on the FT282 product. Even without UV light, FT282 can be hardened, which is a very intriguing new product. ─Author: Mr. Hui-xu, Li, R&D Engineer, Everwide Chemical


Knowledge § Is Silicone's waterproof result good?

It is generally recognized that Silicone has a good waterproof result. This simplification is a bit dangerous because there are many different definitions of "waterproof". The first impression is that Silicone is waterproof. Silicone has very low surface tension, so it is difficult for water to adhere to its surface, and it is easy to gather around water droplets on its surface and runoff. The formation of Silicone has strong water repellent properties (Water Repellent), which is a popular concern for the public. The Si-O bond can be formed between Silicone and glass, and it will not lose its adhesive force due to moisture. It is also one of the sources of the impression that Silicone is very waterproof. Soak Silicone in water to measure the water absorption (Water Absorption, weight change after soaking in water). The standard data is about 1%. Compared with many materials, there are advantages and disadvantages, but they are not outstanding. Since the Si-O bond of Silicone itself tends to be biased towards ionic bonds, it causes Silicone to have a relatively high water vapor transmission rate (Water Vapor Transmission Rate, the amount of water vapor molecules that diffuse through Silicone from one side to the other side). The water vapor transmission rate of Silicone is hundreds or even thousands of times that of some rubbers. From this data, the "waterproof" effect of Silicone in certain electronic fields is very unsatisfactory.


Living § Last speech

My instructor, Feng-Zhi, Zhang, taught "Applied Polymers" at the Institute of Applied Chemistry, Chiao-Tung University. I was invited to give a lecture every year. The content was a brief introduction to many applications of polymers. I gave about five or six courses before and after. Before each lecture, I always visited the teacher, chatted with him, and reported the current work situation. In the speech on June 13 this year, the teacher told me, "this is the last time." because the teacher will no longer offer classes next year when he retires. Our students knew that the teacher was about to retire very early, but we always felt there was still one or two years left. Knowing "it is this year" without being prepared made me stunned. It feels weird that a thing that is accustomed to in life is about to stop. My teacher and I went to the lecture hall first, and then the class started a few minutes later. The students walked into the classroom sparsely and sat forward from the last few rows as usual. I asked a classmate to take a picture with my teacher. For these students, this class is one of the hundreds of lessons. They may forget it after listening, or they may not have any impressions. After class was over, a group of people hopped out of the classroom and have summer vacation within a few days. For my teacher and me, this is the last class of "Applied Polymer." After class, my speech "career" came to an end. After class, I sat quietly on campus for half an hour and then went home. ─Author: Dr. Ming-xu, Li, Everwide Chemical


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