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Based on the two LED chip and package sorting method
From:LED Universal Online    Date:2010/12/30    Click:2441
The human eye for color and brightness of light is very high resolution, especially for the difference and change the color is very sensitive. For different wavelengths of light the human eye color sensitivity is different. For example, for 585nm wavelength light, when the color change is greater than 1nm, the human eye can feel; and for the red wavelength of 650nm, when the color changes in the 3nm, when the human eye can perceive.

Early on, the LED is used to indicate or show the main lamp, and generally single device, so it was selected for sub-wavelength and brightness control requirements are not high. But with the efficiency and brightness of LED continues to improve, their increasingly wide range of applications. When the LED display and the display device as the array, due to the wavelength the human eye for color and brightness sensitivity, with no change sorting through the LED will produce uneven phenomenon, thereby affecting people's visual effects. Wavelength and the uneven brightness will produce uncomfortable people. This is the LED display manufacturers are not willing to see, is people can not accept.


LED generally in accordance with the dominant wavelength, luminous intensity, luminous flux, color temperature, voltage, reverse breakdown voltage, and several other key parameters for testing and sorting. Testing and sorting LED LED production process is a necessary process. Currently, it is a lot of LED chips and packaging manufacturers capacity bottlenecks, but also the cost of LED chip production and an important part of packaging.


1, LED sorting method


LED sorting in two ways: First, the test chip based separation, the second is for testing packaged LED sorting.


(1) chip sorting test


LED chip sorting is very difficult, mainly because LED chip size is generally small, from 9mil to 14mil (0.22-0.35nm). Needs of such a small chip to complete the test micro-probe, sorting process requires accurate mechanical and image recognition system, which makes the equipment cost becomes high, and the test speed is limited. Now the LED chip test separator price of about 100 million yuan \ sets, the test speed of about 10,000 per hour. If calculated in accordance with 25 days each month, each month sorting machine's capacity 5KK.


Currently, the test chip separation in two ways:


One approach is to test the sorting done by the same machine, it has the advantage of reliable, but is very slow, low capacity;


Another method is to test and sorting done by the two machines, test equipment to record the location and parameters of each chip, and then sorting the data passed to the device for quick sorting, this advantage is rapid, But the disadvantage is relatively low reliability, error-prone, as in the test and the Separation between the two steps are usually well separated from the substrate and chip thinning process, and in the process, the wafer may be broken, the local incomplete or partially incomplete fragmentation, making the actual distribution and stored in the chip sorting machines in the data does not match, resulting in separation difficulties.


A fundamental solution to the bottleneck of chip testing sorting key is to improve the wafer uniformity. If a wafer within a 2nm wavelength distribution, changes in brightness within +15%, you can all the chips on this film into one file (Bin), as long as the test to fail to remove the chip can be will greatly increase capacity and reduce the chip cost of the chip. Not very good in the uniform case can also be used to test and the "substandard products more" of the chip area coated with ink-jet means disposed to quickly get the desired "qualified" chip, but this The cost is too high, many will meet the requirements of other rooms as the failed card chips are waste disposal, the final accounting of the cost of the chip market may not be an acceptable level.


(2) LED sorting test


The LED can be packaged according to wavelength, luminous intensity, luminous work of voltage angle and separation test. As a result, the LED into a lot of files (Bin) and categories, and then sorting the opportunity to automatically test set testing standards based on the LED Bin-packing in a different box. As people become increasingly demanding for the LED, the early sorting machine is 32Bin, later increased to 64Bin, now has 72Bin commercial sorting machines. Even so, the sub-Bin of LED technology indicators are still unable to meet production and market demand.


LED test separator is in a particular job Taipower shed (eg 20mA), of the LED test, the general also do a reverse voltage of the test. LED current price of the test separator at about 40 to 50 million yuan / sets, the test speed of about 18,000 per hour. If under 25 days per month, working 20 hours a day, the calculation of time, each sorting machine of the capacity of the monthly 9KK.


Application of large screens, or other high-end customers, high quality requirements of the LED. Especially in the wavelength and brightness consistency requirements are strict. If the LED chip packaging plant in the procurement without making stringent requirements, these packaging factory in a large number of packages will find packaged LED, only a small number of products to meet a customer's requirements, most of the rest will become into the warehouse inventory. This situation forced the LED chip, LED packaging factory in the procurement of the stringent requirements put forward, in particular, wavelength, brightness and voltage indicator table; for example, in the past on the wavelength requirements are +2 nm, and is now required to +1 nm, even in a some applications, the requirements have been proposed +0.5 nm. This chip factory to produce the enormous pressure, the chip must be strictly pre-market sorting.


From the above points on the LED and the LED chip can be seen in the analysis of selected, more economical approach is to test the LED sorting. However, due to the wide range of LED, there are different forms, not present in the shape of different sizes, different light angles and different customer requirements, different application requirements, it was entirely right to use the LED test points selected by the sub-product selection becomes difficult to operate. And the current LED applications are mainly distributed in several wavelengths and brightness range of paragraphs, a packaging factory to customer needs is difficult to prepare all the various forms and types of LED. Therefore, the key back MOCVD epitaxial process, how growth of the required wavelength and intensity of the LED epitaxial wafers is to reduce the cost of key points, this problem is not resolved, LED production capacity and cost will not be fully resolved. However, the uniformity of the wafer under control before, more effective method is a rapid low-cost chip sorting problem.


2, sorting equipment


Currently, LED chip test separation equipment manufacturers primarily provided by the United States and Japan, while the LED test separation equipment mostly by Taiwan, Hong Kong manufacturers offer, China has failed to provide similar equipment manufacturers. LED chip sorting machine includes two hardware components (machine hand, micro-probe and optical test instrument) and a set of system software, which is three parts provided by different manufacturers to re-integrate; and LED test points include selecting machine LED mechanical transmission, storage and optical testing of two parts.


3, LED technology trends selected points


(1) the uniformity of the wafer under control before the development of rapid low-cost chip separation process and equipment.


(2) With the W-class power LED technology, the traditional parameters of LED product testing standards and test methods can not meet the needs of lighting applications, to be the development of new testing standards and methods, include more content and lighting-related optical .


(3) in the LED system life test, the development of LED systems Determination of the long-term performance and life assessment techniques.


(4) LED lighting is in working under high current drive, which raised its higher reliability requirements. Screening of the traditional way of inappropriate LED lighting power LED, must develop new screening test methods, excluding early failure products, ensure product reliability.

 
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