& nbsp; & nbsp; Power sealing requires adhesive



  & nbsp; & nbsp; It's simple to say, it could be that the customer requested glue filling, or it could be that they saw someone else filling glue and also looking for glue filling. To be sure, there are several main purposes and requirements for potting adhesive:< br />


  & nbsp; & nbsp; 1. Waterproof, the sealing glue tightly wraps the entire electrical part of the power adapter, completely isolating it from the outside world; Water, moisture, acid, alkali, and salt cannot come into contact with circuit components, which can improve waterproof, moisture-proof, and corrosion-resistant capabilities. So the glue you choose should have good fluidity. If the fluidity is not good, how can it penetrate deeply and seal completely; Furthermore, it is necessary to have adhesive strength, otherwise it will not be useful if the components are separated due to long-term cold and hot alternation after sealing, and the lifespan and performance of the power adapter will also be affected.
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  & nbsp; & nbsp; 2. Thermal conductivity, power adapters are power products that convert, control, and output energy externally. The adapter needs to generate heat when it works, such as switch tubes, transformers, electrolytic capacitors, inductors, etc., which are not heat generating devices and are all heat sensitive devices. What should we do? We must quickly and efficiently dissipate the heat it generates. So the adhesive definitely requires good thermal conductivity, and it can be said that the higher the expected thermal conductivity of the adhesive, the better. The electrolytic capacitor in the power supply has a lifespan reduced by about half for every ten degrees Celsius increase in temperature, but you cannot add heat sinks to it; As the temperature of transformers and inductors increases, many parameters change, making the entire design more difficult. It's also difficult to add a heat sink for them. The waterproof power supply needs to be sealed as a whole, and the thermal conductivity of air is very low, mainly relying on convection and radiation. But convection is impossible, the components are all trapped in the box. So filling with adhesive with good thermal conductivity can be equivalent to placing each component outside to dissipate heat, not only improving its lifespan but also simplifying the design.
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  & nbsp; & nbsp; 3. Insulation strength, this is easy to handle. Basically, all adhesives are non-conductive, but it should be noted that incomplete curing reactions of AB adhesives like epoxy may result in some localized conductivity. It's hard to say if sand is mixed in to save money. Has your sand been dehydrated or processed, and are there any other elements that interfere with its solidification; Whether the AB agent ratio is reasonable, whether the mixture is sufficient and uniform, and whether all other conditions are met< br />


  & nbsp; & nbsp; 4. According to environmental requirements, adapters are generally certified. It depends on whether the products provided are consistent with the certification, and there is still a significant price difference between environmentally friendly and non environmentally friendly materials.
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  & nbsp; & nbsp; 5. The flame retardant requirements generally depend on the flame retardant testing in UL. Generally, it is required to be above 94-V0< br />


  & nbsp; & nbsp; 6. There are many other parameters, you need to try them yourself. Mainly, your supplier needs to be constant, their supply needs to be stable, and the process needs to be stable. Otherwise, the dispersion is too large< br />




  & nbsp; & nbsp; Several adhesives suitable for power supply sealing



  & nbsp; & nbsp; 1. Epoxy resin: I think it is not suitable to encapsulate adapters, mainly due to high shrinkage stress and poor thermal conductivity. May strain components, solder pads, or alter magnetic circuit air gaps. Moreover, if the curing is not complete, there may be local conductivity. Poor thermal conductivity is like covering a component with a blanket and baking it inside. Practice has proven that the defect rate is high after encapsulation, and the larger the power supply, the more it will fail< br />


  & nbsp; & nbsp; 2. Organic silicone gel is widely used. Good thermal conductivity, waterproofness, etc., and it is a flexible sealing adhesive that will not strain the components. It's just that it's very expensive, so it's important to ensure that the products supplied are consistent with the testing and certification.
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  & nbsp; & nbsp; 3. I am not familiar with polyurethane and dare not speak rashly about it. But it is said that the toxicity needs to be verified< br />


  & nbsp; & nbsp; 4. Hot melt black adhesive belongs to the category of petrochemical substrates. Solid state at room temperature, direct sealing after heating to 130-160 degrees liquefied, belongs to single component flexible adhesive