The human eye has a very high resolution for the color and brightness of light, especially for color differences and changes. The sensitivity of the human eye to different wavelengths of light is different. For example, for a wavelength of 585 nm light, when the color change is greater than 1 nm, the human eye can feel it; and for a red light with a wavelength of 650 nm, when the color changes at 3 nm, the human eye can perceive it.
In the early days, since LEDs were mainly used as indicators or display lamps, and generally appeared as a single device, the control of sorting and brightness of their wavelengths was not high. However, as the efficiency and brightness of LEDs continue to increase, the range of applications is becoming wider and wider. When LEDs are used as array display and display devices, due to the sensitivity of the human eye to color wavelength and brightness, the use of unselected LEDs will produce unevenness, which will affect people's visual effects. Unevenness in wavelength and brightness can give people an uncomfortable feeling. This is something that LED display manufacturers are not willing to see, and it is unacceptable to people.
LEDs are usually tested and sorted according to several key parameters such as dominant wavelength, luminous intensity, luminous intensity, color temperature, operating voltage, and reverse breakdown voltage. LED testing and sorting is a necessary process in the LED production process. At present, it is the capacity bottleneck of many LED chips and packaging manufacturers, and is also an important part of LED chip production and packaging costs.
1, LED sorting method
There are two ways to sort LEDs: one is chip-based test sorting, and the other is to test and sort the packaged LEDs.
(1) Test separation of chips
LED chip sorting is very difficult, mainly because LED chips are generally small in size, from 9mil to 14mil (0.22-0.35nm). Such a small chip requires a microprobe to complete the test, and the sorting process requires an accurate mechanical and image recognition system, which makes the cost of the device high and the test speed is limited. The current price of the LED chip test sorter is about 1 million yuan, and the test speed is about 10,000 per hour. If calculated according to 25 days per month, the capacity of each sorter is 5KK per month.
Currently, there are two methods for chip sorting:
One method is that the test sorting is done by the same machine, and its advantages are reliable, but the speed is very slow and the productivity is low;
Another method is that the test and sorting are performed by two machines. The test equipment records the position and parameters of each chip, and then transfers the data to the sorting device for quick sorting. The advantage of this is that it is fast. However, the disadvantage is that the reliability is relatively low and error-prone, because there is usually a process of substrate thinning and chip separation between the two steps of testing and sorting, and in this process, the epitaxial wafer may be fragmented and partially Incomplete fragmentation or partial fragmentation makes the actual chip distribution inconsistent with the data stored in the sorter, making sorting difficult.
An electrical appliance used to protect electrical equipment from high transient overvoltage hazards and to limit the duration of continuous flow.This term includes any external clearance necessary for the normal functioning of the appliance during operation and installation, whether or not it is a unit as a whole.
Surge Protector, also known as lightning arrester, is an electronic device that provides safety protection for all kinds of electronic equipment, instruments and communication lines.When the electric circuit or communication lines or for outside disturbance suddenly produce peak current in voltage, surge protector in a very short time conduction tap, to avoid surge damage to other devices in the circuits.[1]
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