LED applications have been extended to various fields, including LCD Backlight, mobile phone Backlight, digital light, art lighting, building lighting and stage lighting control, home lighting, etc. According to the DIGITIMES Reasearch survey, demand growth in 2010~2015 is as high as 30%. This has led to a significant increase in LED production capacity. With the complication of the LED application environment, LED downstream manufacturers are increasingly demanding upstream grain quality. For example, the voltage value of the LED Electrostatic Discharge (ESD) is gradually increased from the original 4kV requirement to 8kV. Tolerate the harsh environment of the outdoors. Therefore, the high-voltage LED anti-static test is the key module that is urgently needed to be developed in the current LED die spot measuring machine.
Static electricity in various modes in the environment, including human body static electricity or mechanical static electricity, can cause damage to the LED. When static electricity touches the two pins of the LED through induction or direct contact, the potential difference will directly act on both ends of the LED. When the voltage exceeds the tolerance of the LED, the electrostatic charge is between the two electrodes of the LED in a very short time. Discharge occurs, causing damage to the insulation of the LED, resulting in leakage or short circuit. Therefore, the Solid Electron Device Engineering Council (JEDEC22-A114E, JESD22-A115A) sets the test specifications for the human body electrostatic discharge mode (HBM) and the machine device discharge mode (Machinemodel, MM) to ensure the test specification. The quality of LED products . However, the purchase of foreign high-voltage generators with charge and discharge switching circuits, and the integration of Prober and automated mobile platforms, the main shortcomings are slow response time (0 to 4kV rise time 500ms), and the high-voltage insulation of the probe is not considered, so there is a slow classification of crystal grains. And test the wave type stability is insufficient and other serious problems, often break down LED or charge and discharge modules, as shown in Figure 1, or the machine is not high-voltage testability, is still damaged by high-voltage static electricity after shipment, directly affecting the quality of LED products. In addition, the measurement time of 20,000 to 40,000 wafers on the wafer often takes more than one hour, and it is necessary to shorten the inspection time to increase the production capacity. Therefore, this paper develops a high-speed multi-voltage switching high-voltage generating component design using a dynamic range control circuit and PID feedback control through a high-speed multi-voltage switching LED wafer electrostatic measurement module, with a high-voltage dynamic range (250V-8kV) and High-speed static test (80ms), as shown in Figure 2A and Figure 2B, to meet the needs of the domestic LED industry, to achieve the goal of reducing costs and self-made key modules.
Figure 1 LED is damaged by static electricity
Figure 2A High-speed large dynamic range electrostatic measurement module short-circuit electrostatic test current waveform
Figure 2B High-speed multi-voltage switching high-voltage generating component electrical test output voltage waveform
LED wafer electrostatic measurement module system architecture
In this paper, the high-speed and large dynamic range LED wafer electrostatic measurement module is developed as shown in Fig. 3. The full-test test is carried out for the anti-static voltage of the die, and the LED class is classified according to the LED anti-static voltage. The electrostatic spot test full inspection module comprises a test high speed multi-voltage switching high voltage generating component, a probe component, a charging and discharging component, and a software classification component. The test probe platform moves the two probes to contact the positive and negative electrodes of the LED to be tested, and the high-speed multi-voltage switching high-voltage generating component is set according to the software electronic control program to generate the human body electrostatic discharge mode or the machine device discharge mode test voltage level, charge and discharge. After the module stores the charge of the high voltage generator, the LED to be tested is subjected to an electrostatic withstand voltage test, and finally the software classification component displays the electrostatic test result. The technology is designed for high-speed large dynamic range LEDs in the current domestic LED wafer electrostatic measurement module with insufficient dynamic range (500V to 4000V) and foreign module voltage switching time is too slow (0V to 4kV rise time is about 500ms). The wafer electrostatic measurement module enables the output voltage to cover a wide dynamic range of the standard electrostatic classification of 250V to a maximum voltage of 8000V; and shortens the low voltage switching to a high voltage rise time to within 80ms to achieve high speed and large dynamic range LED crystal Grain line detection and classification purposes.
Figure 3 High-speed large dynamic range LED wafer electrostatic measurement module system diagram
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