The human eye color and brightness of the light of the resolution is very high, especially for the color difference and changes are very sensitive. With the efficiency and brightness LED constantly improved, and its application is more and more widely. When LED as array display and display devices, as the human eye for color and brightness of wavelength sensitivity, no separation of have LED evenly phenomenon and affect people's visual effect.
The wavelength and the inhomogeneity of brightness will give people produce uncomfortable feeling. According to the main wavelength, usually LED light
intensity, light with brightness, color temperature, working voltage, reverse breakdown voltage several key parameters for testing and separation. LED test and the sorting is LED production process of a necessary process. At present, it is many LED chips and packaging manufacturers the production capacity of the bottleneck, is also LED chip production and packaging costs important component.
1, LED the sorting method
LED, there are two ways of sorting: one is the basic test chips for separation, and the second is to packaging good test LED satisfactions.
(1) the test chip satisfactions
LED chips sorting difficult, the main reason is the LED chips generally very small size, from 9 mil to 14 mil (0.22-0.35 nm). In such a small chip need microprobe can carry out tests, sorting process requires precise machinery and image recognition system, which makes equipment cost becomes very tall, and test speed is limited. Now the LED chips sorting machine test about the price is 1 million yuan RMB, Taiwan, the test speed per hour in about 10000 dogs. If the calculated monthly 25 days, every station sorting machine capacity of 5 KK every month.
At present, the test chip sorting have two kinds of methods: a kind of method is tested by the same machine complete separation, its advantages is reliable, but slowly, productivity is low; Another method is to test and sorting by two machines completed, test equipment to record each chip position and parameters, then put these data transfer to the sorting equipment, the rapid separation, do this advantage is rapidly, but its weakness is relatively low reliability, easy to make a mistake, because in the test and separation between two steps usually a substrate thinning and chip the process of separation, and in the process, the extension of may disintegrate, local incomplete or local fractured incomplete, makes the actual chip distribution and storage in sorting machine data with discrepancies, cause difficulties sorting.
From go up at all solve bottle-neck separation test chip is key to improving the extension of uniformity. If an extension of the distribution within 2 nm wavelength in, the change of the brightness in within 15%, can will the film of all chip in return for a (Bin), as long as through the test of the unqualified chip can be removed, will greatly increase the production capacity of the chip and reduce the cost of the chip. In the uniformity is not very good, also can be used to test and the 'unqualified products more' chip areas use inkjet blot out ways of dealing with drop, which quickly to want 'qualified' chip, but so do cost is too high, will put a lot of accord with other room requirements as not certification chip waste treatment, and finally a chip cost accounting may be market can't accept level.
(2) LED the separation test
After the encapsulation leds luminous intensity, according to the wavelength, the light and the Angle of test working voltage and sorting. The result is LED into a lot of the documents (Bin) and category, and then test sorting automatically according to the chance to set the standard test LED in different Bin packing box. Because people LED to demand more and more, the early sorting machine is 32 Bin, then increase to 64 Bin, there are now over 72 Bin commercial sorting machine. Even so, points of Bin LED technology index still can't satisfy the production and the demand of the market.
Sorting machine is LED test in a particular workbench electricity flowing down the (such as 20 mA), LED to test, general will do a reverse voltage value of the test. The sorting machine now LED test about the price 40 ~ 500000 RMB/set, the test speed per hour in about 18000 dogs. If the 25 days a month, 20 hours every day the working time of the calculation, every station sorting machine capacity of 9 KK every month.
Large screen or other high-end application customers, LED to the quality requirements of the higher. Especially in wavelength and brightness on demand consistency is very strict. If FengZhuangChang LED in chip purchasing did not put forward strict requirements, the FengZhuangChang in a lot of these shipped will find, encapsulation good only a small amount of LED products can meet a customer requirements, and most of the rest of the will become in the warehouse inventory. This situation forced LED FengZhuangChang in purchasing LED chip strict requirement put forward, especially the wavelength, the brightness and table of voltage index; For example, the past to request is + 2 nm wavelength, and is now required for the + 1 nm, or, in some applications, has proposed + 0.5 nm requirements. So with the chip factory produce the huge pressure, in the chip sales to strict separation before.
From the above about LED and LED chip points can be seen in the analysis, comparative economic way is to test LED satisfactions. But because of the LED various different kinds of different form, not the shape of the now, different size, different light Angle, different customer requirements, different application requirements, the use right have to completely through test points LED based on product separation is difficult to operate. And now the application of LED mainly distributed in the few wavelengths segment and the brightness of the section area, a FengZhuangChang hard to prepare all 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 the needed wavelength and brightness LED extension is to reduce the cost of the key point, this problem is not solved, LED the production capacity of the cost and still won't get completely solved. But in the extension of the homogeneous degree of get control before, more effective method is to solve rapidly low-cost chip sorting problem.
2, sorting equipment
At present, LED chips sorting equipment testing mainly by the us and Japan manufacturers to provide, and LED the sorting equipment testing by the Taiwan region, most manufacturers provide Hong Kong, mainland China can't provide similar equipment manufacturers. LED chips sorting machine mainly includes two hardware (machine hand, micro probes and photoelectric tester) and a set of system software, the three parts by different manufacturers with respectively to integrated; And LED the test points, including the selection machine LED mechanical transmission, storage and parameter test two parts.
3, LED points selection technology development trend
(1) in the extension of the homogeneous degree of get control before, r&d rapid low cost chip separating process and equipment.
(2) with the W level power LED technology development, the traditional LED products inspection standard parameters and test method can not meet the needs of the lighting applications, it is necessary to develop new test standards and methods, including more and lighting related optical content.
(3) in the LED systems in life test, developing LED system's long-term performance and life quickly determine evaluation technology.
(4) LED lighting is in large current drive to work, it is to put forward higher requirement of the reliability. Traditional way of screening not appropriate LED lighting use high power LED, must develop new screening test method, eliminate early failure is tasted, guarantee the reliability of the product.
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