Solution to LED street light decay problem

　　The key issue of LED street light decay lies in temperature, but LED street lights usually fail in this link. Since the luminous power of LED street lights is greater than that of household lamps, manufacturers have spent a lot of effort on the design of heat dissipation substrate fins and heat dissipation modules. After assembly, the heat dissipation module of the lamp needs to be painted to prevent weather erosion. Unexpectedly, the external protective paint seals back the heat of the heat dissipation module, resulting in poor heat dissipation and LED epitaxial light decay.

　　The heat energy of LED epitaxial luminescence belongs to concentrated heat energy in a small range. When it is used in high-power street lamps, the power input is also large, and the interface temperature of LED is quite high. When the street lamp is working for a long time, if the heat dissipation module cannot effectively dissipate heat, it will affect the service life and luminous performance of LED. For example, the serious light decay of LED street lamps is caused by these factors. LED street lamps are used outdoors and there are interference factors of environmental climate, so most manufacturers protect the outer shell of LED street lamp radiator with anodizing treatment or spray paint to avoid corrosion by acid and alkali substances. The life of anodizing is not long, and it will still oxidize and discolor after a while. If it needs to be dismantled and reworked, it will not only be time-consuming and labor-intensive, but also increase maintenance costs; paint protection has a lower cost and good protection effect, but generally paint has no heat dissipation function, and the paint body itself will form a barrier effect, which is equivalent to increasing the thermal impedance of the LED street lamp radiator. Not only does it not help, but it also blocks the heat energy in the radiator, reducing the luminous power of the LED, and finally leading to serious light decay.

　　The above serious problems have always existed in the LED lighting industry, and are almost the main reason why public engineering LED street lights cannot pass the acceptance of purchasing units.

　　Solutions to LED street light failure:

　　To solve these existing problems, it is recommended that street lamp manufacturers start with basic materials and solve the heat source problem of high-power LEDs from the inside out . For example, when bonding the light-emitting component to the aluminum substrate, thermal conductive adhesive plays a key role. Some manufacturers think that the thermal conductivity of the thermal conductive adhesive film or thermal conductive adhesive pad should be good, and the thicker the film, the better, but they don’t think about the thermal resistance problem. No matter how good the thermal conductivity is, it is useless when it encounters the thermal resistance of the film thickness. What’s more, the thermal conductive adhesive film or soft thermal conductive pad cannot really fit tightly with the substrate, and there are actually many pores on the bonding surface. These pores look like empty air pockets under an electron microscope, which is another form of thermal resistance. With so many thermal resistances that interfere with heat conduction, the efficiency of heat dissipation and heat conduction is invisibly reduced.

　　You need to use the right thermal conductive adhesive, and the recommended soft ceramic thermal conductive adhesive is different from the traditional thermal conductive adhesive film. The soft ceramic thermal conductive adhesive used in screen printing is soft and semi-liquid. When the screen printer scraper is applied to the aluminum substrate, the thermal conductive particles will penetrate into the pores on the surface of the substrate and fill them up. This will form a completely flat plane without pores, which will fit perfectly when bonded to the LED epitaxial substrate. In this way, the thermal resistance is reduced to a minimum, and the heat can be quickly conducted away, which naturally reduces the ambient temperature of the LED grains, prolongs the life of the epitaxial wafer, and greatly delays the occurrence of light decay. In addition, because the soft ceramic thermal conductive paint used in screen printing is ductile, it will change with the thermal expansion and contraction of the aluminum substrate during high-temperature baking or reflow, and the stress is very small, which will not cause the aluminum substrate to bend or warp, let alone explode.

　　For the external protection of LED lamps , it is recommended to use soft ceramic heat dissipation paint for LED lamps. This spray-type soft ceramic heat dissipation paint can be directly sprayed on the outside of LED lamps. It is easy to construct and operate, can adapt to heat dissipation structures of various shapes, and can also be adjusted to different colors to meet the needs of landscape design. The soft ceramic particles in the spray-type heat dissipation paint are nano-processed. The fine particles are not only easy to operate with a spray gun, but also make the heat-conducting particles on the same coating area more and denser, so that the area of ​​temperature volatilization and diffusion is also larger, allowing the heat energy of the LED lamp to be quickly conducted out. Soft ceramic heat dissipation paint is a thermosetting material that complies with RoHS environmental safety regulations. The construction procedure is simple and does not require any special equipment. After baking, it is thermosetting and can withstand the high temperature of LED for a long time without quality changes. LED street lights, landscape lights, or LED advertising billboards used outdoors will also face acid and alkali damage from wind and rain, acid rain, bird droppings, air dust, black smoke emissions, etc. Therefore, this spray-type soft ceramic heat dissipation paint must have acid and alkali resistance. The current acid and alkali resistance range is PH3~11, which can effectively protect the appearance of LED outdoor lamps from corrosion.

　　The cost structure of LED lamps has been continuously improved with the development of packaging technology, substrate design, and heat dissipation module structure, and the quality has been continuously improved. The cost has also been reduced with the development of technology and market demand. However, there are not many manufacturers investing in material improvement, which is mainly related to the development process and habits of Taiwan's industry and commerce. Taiwanese manufacturers are good at process and design, and pay less attention to the research and development of basic materials. Therefore, when it comes to solving technical problems or reducing costs, they tend to think in terms of purchasing or production management. However, American and Japanese manufacturers will think from the perspective of applied materials at the first point in time, and reduce costs, improve quality and increase profits from the perspective of innovation.