Ultrasonic-assisted Preparation Of Gold-tin Alloys And Study On The Stability Of The Cyanide-free Electroplating Solution

At present,electronic products are developing in the direction of miniaturization,intelligence,and environmental protection,and this development trend will also put forward higher requirements on the performance of microelectronic packaging materials.The gold-tin alloys have excellent properties such as high thermal conductivity,strong corrosion resistance,good electrical conductivity,high yield strength,and good wettability,making it an indispensable packaging material in the field of microelectronic packaging today.Therefore,the successful preparation of gold-tin alloys is of great significance in the field.However,the production cost of gold-tin alloys in the consumer market is high,and produced gold-tin alloys have problems such as high brittleness and difficulty in processing,which make it impossible to achieve large-scale production.With the application of electroplating technology,the preparation of gold-tin alloys has ushered in a new turning point.The expense can be greatly reduced by using a simple electroplating process to prepare gold-tin alloys.However,the technical problems face with the electroplating solution of the process are unsteady and process-control parameters.Building on the above problems.This thesis uses ultrasonic-assisted pulsed electrodeposition to prepare gold-tin alloys.Based on this experimental method,the main research contents and obtained results are as follows:（1）Based on Materials Studio software,the electronic structure of gold-tin alloys intermetallic compounds（MICs）is calculated by first-principles generalized gradient approximation exchange correlation functional（GGA-PBE）and is compared and analyzed about the stability of gold-tin alloys intermetallic compounds（MICs）.The calculation results show Au Sn is the most stable phase,followed by Au Sn₂and Au Sn₄ phase,and Au₅Sn is the less stable phase.The results provide a theoretical basis for the subsequent exploration of process parameters in the preparation of gold-tin alloys by ultrasonic-assisted pulsed electrodeposition.（2）The stability of different mixed electroplating solutions（gold electroplating solution,tin electroplating solution,mixed cyanide-free gold-tin alloy electroplating solution）was tested by electrochemical tests including agents,stabilizers,antioxidants,etc.To investigate their effect on the stability of the electroplating solution.The best cyanide-free electroplating solution for preparing gold-tin alloys is compared and discussed.Their concentration values of the electroplating solution are in order KAu Cl₄(0.0265 mo L·L^-1),Na₂SO₃(0.3180 mo L·L^-1),C₁₀H₁₆N₂O₈(0.0051 mo L·L^-1),C₆H₁₇O₇N₃(0.4110 mo L·L^-1),Sn Cl₂·2H₂O(0.0220mo L·L^-1),K₄P₂O₇·3H₂O(0.1211 mo L·L^-1),C₆H₁₇O₇N₃(0.4110 mo L·L^-1)and C₆H₈O₆(0.0852 mo L·L^-1).（3）By studying the preparation of gold-tin alloys under different current densities,different on-off ratios,and different electrodeposition time,and comparing and analyzing the percentage of Sn in the coating,the optimal process parameters were obtained.Among them,the optimal current density is J=2.0 m A/cm²,the on-off ratio is T_on:T_off=2:8 and the electrodeposition time is 40 min.Under the conditions of assistance,it is more conducive to the precipitation of gold-tin alloy in the cathode,and the coating is good.（4）By studying the preparation of gold-tin alloys by stirring heating and ultrasonic-assisted pulse electrodeposition under different electrodeposition time,it is compared and analyzed that the preparation of gold-tin alloys by ultrasonic-assisted pulsed electrodeposition was was was the method that can improve the synergistic effect of ultrasonic waves.The diffusivity of ions in the plating solution can slow down the uneven surface of the coating,pores,cracks,and other defects caused by the adhesion of bubbles in the cathode area,and it is also beneficial to maintaining the temperature of the plating solution at about 40℃.