Preparation And Application Of Ag Nanocube Structured High-temperature Solder

Insulated gate bipolar transistor（IGBT）has the characteristics of high output power,high input impedance,fast switching speed and low saturation voltage,and is widely used in the power electronics industry.The chip package in the IGBT module is to realize the interconnection between the power semiconductor chip and the substrate through the connecting material.The connection layer between the chip and the substrate needs to provide necessary heat dissipation,heat conduction and mechanical support,which puts forward higher demands on the chip packaging interconnect technology.Due to the advantages of low-temperature solderability,high electrical and thermal conductivity,wide operating temperature range and good environmental protection,nano-Ag solder can be used as a reliable solder for high-temperature power chip packaging.With the advantages of Ag nanocubes with sharp and large curvature edges,good self-assembly property,the high-temperature solder is prepared by prepared by Ag nanocubes particles and organic solvent.The purpose is to apply a new type of chip interconnection material for high-temperature packaging in the electronic industry.This experiment focuses on the preparation of Ag nanocubes particles,and studies the effects of processes on its structure.With the aid of this nano-Ag,the optimized welding process was explored including of pretreatment method.Therefore,the soldering performance with Ag nanocubes was clarified.Firstly,the polyol reduction method is adopted.Ethylene glycol（EG）is selected as the solvent and reducing agent.Sodium hydrosulfide（Na HS）provides hydrogen sulfide anion.Hydrochloric acid（HCl）is being the etching agent of nano-Ag particles,polyvinyl pyrrolidone（PVP）is the protective agent,and Ag trifluoroacetate（CF₃COOAg）provides Ag source.The effects of component concentration,reaction time and temperature on the preparation of Ag nanocubes were studied.Ag nanocubes particles with particle size of60 nm-100 nm was obtained with high yield,good dispersion and excellent crystallinity.Next,the orthogonal experimental method was used to optimized the process conditions of electroless Ag plating on welding substrate.Through the analysis of surface morphology and bonding force,the electroless Ag layer has excellent crystallinity,dense and uniform surface,and the thickness of electroless Ag layer is about 4.5μm.Finally,nano-Ag high-temperature solder was prepared by using nano-Ag particles and ethylene glycol according to the weight ratio of 8:2.The effects of Ag solder composition,welding temperature,welding time and heating rate on the surface morphology and shear strength of the joint were explored.The shear strength is 21.45MPa under the optimum welding condition.In addition,the pretreatment’s effects on the surface morphology and shear strength of the joint were also studied.Based on the synthesized Ag nanocubes particles and ethylene glycol,Ag nanocubes high-temperature solder was formulated and soldered under optimized conditions.The results show that the Ag nanocubes nano-Ag high-temperature solder has lower joint porosity and higher shear strength than nano-Ag high-temperature solder,the shear strength increased to 25.44 MPa.