A Assembly Design And Implementation Of High Speed Deep Trench Transient Voltage Suppressor

Transient voltage suppressor(TVS)is an effective protective semiconductor device based on diode technology,which is widely used to protect the sensitive devices in the circuit from the impact of various forms of high voltage transient.With the coming of 5G high-speed mobile technology,the development of the “Internet of Things”,and the application of high-speed data connection for portable devices such as smartphones,tablets,market needs the ultra-low junction capacitance,ultra-thin package of high speed TVS to realize the circuit protection for Electro-Static Discharge(ESD).The high-speed deep trench TVS is designed to achieve ultra-low junction capacitance,which uses deep trench isolation and near-intrinsic doping technology to build an avalanche diode and two PIN diodes into the same chip.It is difficult to assemble it in an ultra-thin package as its small die size & bonding pad,deep trench inside the die and uneven aluminum top metal layer.The purpose of this thesis is to study and design its assembly processes based on DFN0603 package for this special TVS,especially on wafer sawing,die attaching and copper wire bonding processes,to eliminate quality risks in the Assembly and Test Operations.The main studies of this paper are:(1)Study and compare the characteristics of chip,material and fixture.(2)Analyze the potential defects,and find out the root cause by experiment.(3)Find the optimum combination scheme and verify the critical parameters through Design of Experiment.The key conclusions of this paper are:(1)the high adhesive UV tape can eliminate front-side and backside chipping as it can provide stronger adhesive strength on die during the wafer sawing process.(2)The multi-line interval sawing approach will release silicon stress around deep trenches significantly in sawing process,as it increases die's “Area Perimeter ratio”.Hence,it results in significant reduction in die chipping defect.(3)In the die attach process,proper setting of "Bond Z offset level" can reduce the worn out of small rubber tip to improve the stability in the production,as well as the good control of Bond Line Thickness(BLT)after epoxy die attach.(4)In the wire bonding process,by dividing ultrasonic energy to three segments and with optimum bonding force setting,it can reduce Non-Sticking on Pad or Cratering defects.The assembly of high speed deep trench TVS in ultra-thin package is successfully realized after conducting above studies and experiments.The product characteristics and reliability test results fulfilled the quality requirements,and can be released for mass production.