Study On Synthesis And Properties Of A New Brightener For Electroplating Copper Pillars On HDI Printed Circuit Board

In this thesis,the leveling technology of electroplated copper pillars on printed circuit boards was taken as the research object,and eight novel leveling agents containing sulfur heterocycles and three novel leveling agents containing glycidyl ether were designed and synthesized.Their synthesis conditions,structures and electrochemical properties were studied,and their leveling mechanism and action mechanism in the process of electroplating copper pillars were discussed by electrochemistry,quantum chemical calculation and molecular dynamics simulation.The main research contents and innovations are as follows:(1)Eight kinds of sulfur-containing heterocyclic leveling agents were synthesized,among which AT14 and HT14 had good solubility in 120 g/L sulfuric acid solution.The optimum synthesis conditions of AT14 are as follows:2-aminothiazole and 1,4-butanediol diglycidyl ether are added in the molar ratio of 1:0.5,and 1 equivalent sulfuric acid is added to react at 95℃for 6 hours.Fourier transform infrared spectroscopy(FT-IR)showed that the reaction was complete under these conditions.Gel permeation chromatography showed that the number average molecular weights of AT14 and HT14 were 2395 and 2647 respectively,and the molecular weight distributions were 2.15 and 1.86 respectively.The comparative experimental study in the Haring cell shows that the arch rate of HT14(8 mg/L)is only 15.8%in the copper pillar plating bath with the composition of120 g/L sulfuric acid,120 g/L copper sulfate,60 mg/L chloride ion,400 mg/L PEG-20000 and 8 mg/L SPS at 40℃and 10 ASD.However,the arch rate of AT14(40 mg/L)electroplated copper pillar is 30.5%.SEM shows that the coatings of the two leveling agents are uniform,fine and well crystallized.EDS test shows that both leveling agents are deposited during copper electroplating.The corrosion test in 1 mol/L hydrochloric acid solution shows that the corrosion resistance of HT14 coating is better than that of AT14.(2)Three kinds of glycidyl ether leveling agents EM12,EM14 and EM16 were synthesized,and they have good solubility in 120 g/L sulfuric acid solution.Fourier transform infrared spectroscopy(FTIR)showed that the polymerization was completed when heated at 95℃for 6 hours.Gel permeation chromatography showed that their number average molecular weights were 1929,1984 and 1026,and their molecular weight distributions were 1.53,1.64 and 1.72,respectively.The comparison experiment in the Haring cell shows that the arch rate of EM12(40mg/L),EM14(40 mg/L),EM16(40 mg/L)and EM16(40 mg/L)are 4.6%,15.5%and24.5%,respectively.All the properties of the coating are strongly related to the carbon chain length of glycidyl ether:with the increase of carbon chain,the nodules on the surface of the coating gradually become serious,the water contact angle of the coating gradually increases,and the corrosion resistance in 1 mol/L hydrochloric acid solution gradually decreases.(3)The corrosion inhibition efficiency of levelers AT14,HT14,EM12,EM14,EM16 and PAS-A-5 in 120 g/L sulfuric acid solution was studied by weight loss method.The fitting results show that their adsorption behaviors are in accordance with Langmuir adsorption isotherm,and their adsorption free energy is between-34.25 and-36.99 kJ/mol,so they belong to mixed adsorption mainly by chemical adsorption.The potential-time curve of copper pillar plating solution shows that the relative difference of potential drop caused by leveling agents at high and low rotating speeds is EM12>EM14>HT14>PAS-A-5>EM16>AT14,which is consistent with the arch rate of copper pillar plating.The quantum calculation results show that the LUMO orbitals of EM12,EM14and EM16 are distributed on the imidazole ring with low energy,which indicates that they are mainly adsorbed on the negatively charged copper cathode surface by N~+ions on the imidazole ring.HOMO orbit of HT14 is located on the tetrahydrothiazole ring,and its energy is high,which indicates that sulfur atoms on the tetrahydrothiazole ring are strongly adsorbed on the copper surface.The results of molecular dynamics simulation show that all the five synthetic leveling agents are laid on the Cu(111)crystal plane by parallel adsorption,thus completing the leveling in the process of electroplating copper pillars.