Electrical Overstress Failure Mechanisms And Characteristics Of The Interactive Devices Under Electrostatic Discharging

With the electronic devices multi-functional and intelligent development,the information transmission becomes more frequently,and the data size increases.The Ethernet devices,which is the representative of the interative equipments that information interacts between machine and machine,and the touch display devices,which is the representative of the interative equipments that information interacts between machine and user,become the mainstream of the electrical interative devices,playing an important role in human social life.The high demands of portablility and integration promote the size shrinks of the electrical circuits.Electronic devices become more sensitive to electrostatic discharge(ESD).The electrical overstress(EOS)caused by ESD has become an important reason for electrical devices failure.Many scholars are devoted to the study of the EOS failure.However,due to the complex working environment and the low repeatability of ESD events,the characterization of ESD is still under researching.Many EOS failure analyses usually has an idealized source setting,which does not conform the actual situation.This is a great defect of the failure analysis,and not conducive to the ESD protection design.This dissertation focused on the Etherent devices and touch display devices,obtained the EOS source characterization during ESD.By combining the actual EOS characteristics with the failure theories,the EOS failure analysis methods were discussed and verified.The main contents and conclusions are as below:(1)Regarding the carriers as particles with mass,the ESD process forces the carrier's motion in microstructure.According to the energy band theory,the carrier motion characteristics have been analyzed.The EOS failure is caused by carries motion,and the current is an important parameter of representation the carrier movement.Therefore,the study of current characteristics is the main part of the EOS failure analysis.(2)Different EOS failure types were studied based on the microstructure physical properties.Thermally induced failure usually happens in the semiconductor structures,as the carrier motion during ESD can cause the avalanche breakdown orcurrent side effect,which will generate Joule heat and increase the structure temperature.Field induced failure usually happens in the insulator structures,as the carries are accelerated by the electric field of the ESD and can obtain enough energy to pass through the insulator barrier.The tunnel channel caused by large amount of carrier tunneling leads to the destruction of the insulation property.(3)The Ethernet modeling method was come up based on the Ethernet system physical characterization.ESD current waveforms were obtained according to simulation.The ESD current is influenced by cable length,cable discharge voltage,magnetic saturation and the impedance of the IC pin.Ethernet transceiver IC pin is the EOS failure structure during ESD,as it could be damaged by thermal heating.The failure situation can be analyzed combining the simulated current and the thermal failure numerical model.The result shows that for the Ethernet system studied in this paper,assume that the cable charge voltage is 1 kV,the cable discharging will lead to the IC pin thermal failure if the cable length is longer than40 meter.(4)The ESD current measurement methods were come up based on the touch display physical structure,and the displacement current full wave model was built.The ESD current waveforms were obtained according to the measurement and simulation.Current is influenced by display physical characteristics,discharge voltage,polarity,the approaching speed and the discharge humidity environment.Touch panel is the EOS failure structure during ESD,as the insulation glass between ITO layers could happen to have tunneling channel by the carrier motion in the electric field.The calculation result shows the touch panel ITO trace could fuse because of the mA level tunneling current.The Ethernet and display ESD cases study proved the EOS failure analysis method could be used in different electrical systems,also shows that with the physical structure and the discharge current,the EOS failure could be effectively analyzed.