LED sorted two methods and development trend - (AddTime ： 2013-01-17)

The human eye to light color and brightness of the resolution is very high, especially for color difference and change is very sensitive. For different color the wavelengths of light the sensitivity of the human eye is different. For example, the wavelength is 585 nm light, when the color change is greater than 1 nm, the human eye can feel; For the wavelength of 650 nm red, when the color changes in 3 nm, the human eye can perceive.

In the early days, because LED mainly used as instructions or display lamp, and general with single device appear, so for the wavelength of sorting and brightness control request is not high. But with the efficiency of the led brightness and constantly improved, and its application is more and more widely. When LED as array display and display device, due to the human eye for color wavelength and the sensitivity of the brightness, with no separation of LED variable can produce uneven phenomenon, affecting people's visual effect. The wavelength and brightness uniformity will give the person produces uncomfortable feeling. This is the LED display manufacturers do not want to see, is also the people cannot accept. According to the dominant wavelength, usually LED luminous intensity, light brightly lit, color temperature, working voltage, the reverse breakdown voltage and so on several key parameters testing and sorting. LED test and sorting is LED the production process of a necessary process. At present, it is a lot of 200W led floodlights and packaging manufacturer's capacity bottleneck, but also 200W led Flood light production and packaging cost is an important part of.

1, LED the sorting method
LED the sorting there are two ways: one is based on chip test sorting, 2 it is to packaging good LED testing sorting.

(1) chip test sorting
200W led Flood light separation very difficult, the main reason is the 200W led Flood light size is very small, usually from 9 to 14 mil mil (0.22-0.35 nm). In such a small chip need microprobe was able to finish testing, separation processes need accurate mechanical and image recognition system, which makes the equipment cost becomes very tall, and test speed limits. Now the 200W led Flood light test separator price about 1 million yuan RMB/table, the test speed at 10000 per hour about only. If, in accordance with the monthly 25 day, each a sorting machine capacity for monthly 5 kk. At present, the chip test separation have two kinds of methods: a kind of method is test sorting by the same machine finish, it has the advantage of reliable, but slowly, productivity is low; Another method is to test and sorting by two machine completed, test equipment to record each chip position and parameters, and then the data transfer to the sorting equipment, rapid separation, do this advantage is fast, but its weakness is that low reliability, easy to make a mistake, because in the test and the separation between two steps usually a substrate by thinning and chip separation process, and in this process, the epitaxial wafer may shatter, local incomplete cataclastic or local incomplete, making the actual chip distribution and storage in the sorting machine data discrepancy, cause separation difficult. Fundamentally solve the chip test sorting bottleneck problem is the key to improve the epitaxial wafer uniformity. If a piece of epitaxial wafer wavelength distribution within 2 nm, brightness changes in within + 15%, can put the film on all chip into first gear (Bin), as long as through the test the unqualified chip removal can, will greatly increase the productivity and reduce the chip chip cost. In the uniformity is not very good, also can use the test and the "unqualified products more" chip area with ink jet on the way, so as to get rid of quickly get want "eligible" chip, but do so cost is too high, will take a lot of conform to the other room requirements of the chip are not certification as a waste treatment, and finally the chip cost accounting may be market can't accept level.

(2) LED test sorting
After packaging the LED can be in accordance with the wavelength, luminous intensity, light Angle and the working voltage of test sorting. The result is the LED into a lot of files (Bin) and category, and then test sorting opportunity automatically according to a set of test standard the LED packaging in different Bin box. Because people for LED requirements more and more high, the early separator is 32 bin, then increase to 64 bin bin and there are now over 72 commercial separator. Even so, points Bin LED technical indicators are still unable to satisfy the production and the demand of the market. LED test separator is in a particular table electric shed (such as twenty ma), LED to test, general will also do a reverse voltage value of the test. Now LED test separator price about forty to 500000 RMB/table, the test speed at 18000 per hour about only. If, in accordance with the monthly 25 days, every twenty hours of working time calculation, each a sorting machine capacity for monthly and kk. Large screen or other high-end application customers, to the quality of the LED the demand is higher. Especially in the wavelength and intensity consistency requirements is very strict. If FengZhuangChang LED in chip purchasing did not put forward strict requirements, the FengZhuangChang over a very large number of package will be found, packaging good LED in only a few number of products can satisfy a customer requirements, most of the rest will be in the warehouse inventory. This situation LED FengZhuangChang force in purchasing 200W led Flood light puts forward strict requirements, especially wavelength, intensity and table voltage indicator; For instance, in the past to wavelength requirement is + 2 nm, and is now required for the + 1 nm, even in some applications, has put forward the requirements of + 0.5 nm. So with the chip factory will produce the enormous pressure, in the chip sales must be carried out before the strict separation. From the above about LED and 200W led Flood light points selection analysis can see, more economic way is to test LED sorting. But because there are so many types of LED, there is a different form, not the shape, different size, different light Angle, different customer requirements, different application requirements, the use right to complete through the LED test points selected product separation is difficult to operate. But at present, the LED application are mainly distributed in several wavelength section and brightness section area, a FengZhuangChang difficult to prepare all the customer needs of the various forms and types of LED. So the key to the problem and return to the extension of MOCVD process, how to grow a required wavelength and brightness LED epitaxial wafer is to reduce the cost of key point, this problem is solved, the productivity and cost LED will still not fully resolved. But in the homogeneous degree of the epitaxial wafer under control before, more effective method is to solve fast low-cost chip separation problem.

2, sorting equipment
At present, the 200W led Flood light test sorting equipment mainly consists of the United States and Japan, and LED manufacturers to provide the test sorting equipment mostly by the Taiwan area, Hong Kong manufacturers to provide, China can't provide similar equipment manufacturers. 200W led Flood light separator mainly includes two major hardware part (machine hand, micro probe and photoelectric tester) and a set of system software, and the three parts are made of different manufacturers to provide integrated up again; And LED test points selection machine, including LED mechanical transmission, storage, and photoelectric test two parts.

3, LED points selection technology development trend
(1) in the homogeneous degree of the epitaxial wafer under control before, r&d rapid low cost chip separation technology and equipment.
(2) with the W level power LED the development of technology, the traditional LED products parameter testing standards and test methods can not meet the needs of the lighting applications, it is necessary to develop a new test standard and method, including more and lighting related optical content.
(3) in the LED system life testing, research and development LED system's long-term performance and life of the rapid determination of evaluation technique.
(4) the 200W led Flood light is a large current drive to work, it is the reliability of the put forward higher requirements. The traditional LED screening mode suitable high-power 200W led Flood light , must develop new screening test method, eliminate early failure products, ensure the reliability of the products.