With the increasingly mature domestic LED industry chain, product raw material performance continues to optimize, each LED packaging manufacturer's product performance differences gradually reduce, in order to compete for market share, the price war continued to stage, the product prices continue to refresh the record. The optimal combination of product materials and large-scale production of equipment have become an important way for the industry to make profits. At the same time, the improvement of the details of the product process will also be an important factor in the stability of the packaged product's performance. Stability determines success or failure, and details determine development.
Siu Chi energy-saving COB R & D center Dai Xiaodong visited some customers, most of the application technicians predicted that the application of COB precipitation process products will explode, because most of the world's leading COB manufacturers use this process, the appearance of high-end atmosphere, upper grade, product colloid Low temperature, the same light-emitting surface product power can be further increased, optical density is greater, the advantages are obvious, with most domestic COB manufacturers can mass produce precipitation products, the advantages of international COB manufacturers gradually reduced.
So does this process have a qualitative change in the product light pattern? Here, the author discusses the effect of phosphor deposition technology on the product light pattern.
The blue chip excitation phosphor is currently the most common white light production method. In an ideal state, evenly distributed phosphors are excited by uniform blue light, and the light output surface will lead to uniform white light, and the product light pattern is perfect, as shown in FIG. However, most of the current COB products are not so. Larger light-emitting surface chips and low power, the phosphor around the chip is fully excited, the color is white or bluish, phosphors that are relatively distant from the chip can not be fully excited, the color is Yellow, as shown in Fig. 2, leads to uneven light output, such as macula, blue heart, and so on.
Usually, we can solve the problem by modifying the light emitting surface or increasing the number of chips, optimizing the arrangement of the chips, and optimizing the structure of the glue surface. The finished product application end can be optimized by means of lens optics design, increased stencils, frosted processing, etc. However, by designing the secondary optical lens to optimize the product light pattern, too much light flux will be sacrificed, and at the same time, the high investment in design will be used to erode enterprise profits. The best design of the bead is the key to the cost-effectiveness of the whole lamp. We are not only concerned with the exterior design of the lamp. We focus more on the light quality of the product. We are faced with lamp selection under comprehensive consideration of power, heat, light type and price. Considering the effect of the precipitation lamp beads, how the specific light pattern effect depends on the combination of lenses (reflecting cups) or simulation tests.
The author has repeatedly carried out the lens light distribution and discovered that the uniformity of the light pattern of the phosphor deposition process product is poorer than that of the conventional process, the jagged edges of the light shape appear, and the blue light spots of the light type are obviously problems, which seems to disappoint us. It does not give us the perfect effect of light, of course, precipitation process product light can also be optimized, but will sacrifice brightness and increase costs.
Some lens makers frankly stated that the thinning of COB phosphors poses challenges for the design of lenses (reflecting cups), which require more complex optical processing of stray light. Because some lens imaging problems are obvious, according to the convex lens or Fresnel imaging principle, the product light pattern will restore the internal structure of the lamp beads, the deposition process product phosphors sink into the bottom of the substrate, the glue surface becomes clearer and more transparent, the chip arrangement is more obvious, When the imaging problem of the lens is obvious, the precipitation process will be more difficult to match light than the conventional non-precipitation process. Some of these products even appear blue spots.
The author always believes that the key to solving the problem is to clarify the source and nature of the problem. It is necessary to solve the problem from the source. The intermediate remedial measures can only serve as temporary measures and the versatility is not strong. The microscopic analysis of the phosphor distribution in the precipitation process and the conventional process will be described below:
The conventional non-precipitated products have uniform light output. As shown in Figure 1, there are phosphor distributions around and above the chip, and the light output is relatively uniform; the blue light spots appear on the precipitation process product, as shown in Figure 2. The conventional chip has five-side light, and there is phosphor coverage on top of the chip. However, the four sides of the chip are not surrounded by phosphor powder, other phosphors sink into the bottom of the substrate, the encapsulation glue has no phosphor powder, and the blue light on the side of the chip is directly derived from the glue surface to become a blue spot in the light type.
Faced with the impact of precipitation process products on light, how can it be improved?
The author summarizes several improvements:
1. Chip height selection
In order to increase the brightness of the chip, some chip manufacturers increase the light output surface by increasing the thickness of the chip, and increase the brightness. Therefore, it is not advisable to use chips that are too thick in precipitation process products.
2. Phosphor thickness control
Control the degree of phosphor deposition, keep the phosphor coating on the side of the chip, and the chip has no blue light overflow;
3. Chip density adjustment
High-density products have small chip spacing and high optical density. If the precipitation process is used, it is also a clever solution to the light-type problem. As shown in the figure below, the chip spacing of Figure 1 is small, there is no overflow of blue light on the chip side, and the product has a good light pattern. Figure 2 Obvious uneven spot appears. However, if the chip density is too high, the light on the side of the chip cannot be exported, resulting in a low light efficiency of the product, and the chip utilization rate is not high, ie, the cost is increased.
4. The choice of product process
High-density blue light shines on the phosphor. The phosphor is excited by the blue light in the form of light and heat. The light can easily derive the colloid, but the heat is difficult to disperse. The reason is that the thermal conductivity of the silica is poor, and the heat of the phosphor cannot be quickly exported. , resulting in high temperature colloidal, COB products aging cracking and other issues in fact with colloidal temperature is very large, so high wattage, high density products using precipitation process, the colloidal heat is small, the chip side has no obvious blue light overflow, the effect is perfect. However, the small wattage product colloidal temperature is low, the use of precipitation process is of little significance, the product light type also has no advantage, it is recommended that according to the product optical density, the size of the colloidal temperature process selection.
SHENZHEN CHONDEKUAI TECHNOLOGY CO.LTD , https://www.szfourinone.com