The led lighting industry chiefs discussed the superiority and inferiority of cob packagingbest, t5, t8, led, tubes, lights, lamps, fluorescent, bulbs, lighting, packaging, reviews: Some time ago, the experts say about the COB APP watched two controversial text, presumably now it has been forgotten, but not busy when he was two, is quite good. Of course, not a problem for the two authors argue was right or wrong to judge, just to reiterate some basic common sense. My Chinese is not very good, but please forgive me. From COB advantages and disadvantages of both share with you.Some time ago, the experts say about the COB APP watched two controversial text, presumably now it has been forgotten, but not busy when he was two, is quite good. Of course, not a problem for the two authors argue was right or wrong to judge, just to reiterate some basic common sense. My Chinese is not very good, but please forgive me. From COB advantages and disadvantages of both share with you. 1, COB advantages: good heat dissipation, low cost As we all know, there are three cooling methods: 1 conduction; convection 2; 3 radiation… But for LED packaging, a key consideration is the first (ie conductive). The laws of physics are relevant: = Heat transfer coefficient of thermal dissipation area x x temperature differential / thermal path length As can be seen from the formula, the thermal conductivity, and the temperature difference between the cooling area the better, the smaller the better heat conduction path length, i.e., the more heat transfer, better is the dissipation. The larger the thermal conductivity, thermal resistance is smaller. For the multi-layered thermally conductive material overlap, to repeatedly applying the above formula. In comparing two structures having the same functions (for example, compare the COB and SMD), factors can be considered individually. In particular, note that, when comparing an argument, other factors must be the same. Comparison of cooling capacity, we should be compared to the same heat source, such as material and area of ??SMD 10W and 10W COB, the fins have the same, which is “apples to apples comparison”, can distinguish good and bad. If not, it is the “apples and oranges comparison,” are not comparable. ? Next, the COB and non COB comparison. (1) COB: As we all know, LED heat is mainly generated P- epitaxial layer 1 Figures 1 and 2 are two basic structure COB: Figure 1 is a flip-chip COB, FIG. 2 is a dress COB. I do not know what kind of country is more. Some flip COB comparison difficult, the cooling effect is better. On a heat sink has a plurality of chips, phosphor coverage on the chip. Tell a story. I was first in the 2004 meeting, it was reported COB. The COB was etched on a silicon wafer is a recess in the chip groove. However, the process is more difficult, there is no promotion. According to this concept, we designed a QFN structure similar to the semiconductor industry, and no groove COB structure. By 2006, the first time I saw COB product was just launched, the main purpose is to reduce costs (including increase productivity) and high-power devices to solve (1W had just started production of chips) of heat. COB compared with the then K-2, significantly lower cost and good heat dissipation. COB compared with the then SMD, the advantages of the heat is not too large, but still a big cost advantage. (2) with a non-COB package structure: more base package (extra thickness), poor heat dissipation, high cost 2 As described above, before the two authors point of contention from the motivation to develop new products (such as the development COB) to consider. As an engineer for nearly 20 years, I think the motivation for the development of COB had basically two things: (1) reduce the time of packaging material costs, improve production efficiency, reduce production costs; (2) to improve thermal performance. An additional benefit is the elimination of part of the ghost. The debate now is that the new products did not meet the original purpose? Apparently achieved. The question is, why some products a lot of people see that it is not good, but companies also continue to produce, the market also continue to accept? There are two reasons: (1) From a market perspective, there is no short-term or a new product to replace it, or a new product price is too high; (2) From the perspective of the manufacturer, or a new product is too costly or too difficult to process, or the investment is too large to put into production, we had to give up. That is why large international companies have been working to develop better quality, light-efficient COB, in order to maintain their advantage and China’s market share. Twenty years ago, when I started out as an engineer, I just want to consider the technical. But the boss will consider the cost, whether at home or abroad, mostly the truth.