Study On The Properties And Mechanism Of Copper Microvia Filling Additive

With the development of the information society,electronic products continue to develop in the direction of intelligence and lightness.As a carrier of electronic products,PCB has enormous influence on the performance of electronic products.The microvia is used as a channel connecting the electronic components in the PCB.The quality of the filling determines the electrical performance of the electronic product.Acid sulfate copper plating is commonly used for microvia filling?The quality of the copper plating is closely related to the additives.Microvia filling additives are mainly divided into accelerators,levelers and inhibitors.At present,the research of microvia filling additives is mainly focused on the development and compounding of additives.The mechanism of action of single additives and composite additives in microvia filling is rarely studied.In this paper,MPS?3-mercapto-1-propanesulfonate sodium?as accelerator,IML?imidazole quaternary ammonium salt?as leveler,EPE4500?polyethylene oxide and propylene oxide copolymer?as inhibitors,respectively.The mechanism of the single additives MPS,IML and EPE4500 in blind hole filling was studied.Afterwards,the mechanism of action of combination additives in microvia filling was studied through the combination of the three additives.The main research contents are as follows:?1?In the single system of MPS,the compounds of-S^--Cu⁺and-SO₃^--Cu⁺formed by MPS and Cu⁺in single MPS system can inhibit the deposition of Cu at the bottom of microvia,and the inhibition effect will be saturated when MPS concentration is 6ppm.The compound of MPS-Cu⁺-Cl^-formed by MPS,Cl^-and Cu⁺in MPS-Cl^-compound system can accelerate the deposition of Cu⁺at the bottom of microvia,and the acceleration effect will be saturated when MPS and Cl^-concentration are 6ppm and 60ppm respectively.Furtherly,MPS will make cathode current density shift positively and equilibrium potential shift negatively in the base solution without Cl^-,which indicates MPS plays a role in inhibiting the deposition of copper ions.In contrast,MPS will make cathode current density shift negatively and equilibrium potential shift positively in the base solution with Cl^-,which indicates MPS plays a role in accelerating the deposition of copper ions.Finally,the single molecular layer theoretical adsorption model of the compounds of-S^--Cu⁺,-SO₃^--Cu⁺and MPS-Cu⁺-Cl^-can be raised,which can contribute to the establishment and explaination of interaction mechanism of MPS and Cl^-.?2?In the single system of IML,N⁺in IML will be adsorbed on the surface of the cathode with a higher current density,and the inhibition effect will be saturated when IML concentration is 30ppm.After adding IML to the based solution,the cathode current density will shift positively and the equilibrium potential will shift negatively,which indicates IML plays a role in inhibiting the deposition of copper ions.In the IML-Cl^-,IML can form-N⁺-Cl^-compounds.When IML concentration is 30ppm and chloride ion concentration is 60ppm,the inhibition is maximal.Comparing the two systems,according to the results of microvia filling and electrochemical detection,it can be found that the inhibitory effect of IML in the presence of chloride ions is enhanced.This is due to the fact that the-N⁺-Cl^-compounds formed by IML is adsorbed in the form"chemical bond"on the surface of the cathode;A mechanism model for the action of additive IML in microvia filing is proposed.?3?In the single system of EPE4500,oxygen in the EPE4500 and Cu⁺forms-O^--Cu⁺compounds,which is adsorbed on the cathode surface to inhibit copper ion deposition.The results of microvia filling and electrochemical detection show that the inhibition effect is maximized when the concentration of EPE4500 is 30 ppm.In the EPE4500-Cl^-system,a single EPE4500 molecule forms multiple-O^--Cu⁺-Cl^-compounds.The stability of this complex is stronger than that of O^--Cu⁺compounds,and the microvia filling results and electrochemical detection.The results showed that when the concentration of EPE4500 was30ppm and the concentration of chloride ions was 100ppm,the inhibitory effect reached the maximum.?4?In composition of additives,when the concentration of MPS is 3-6ppm,and the concentration of IML and EPE4500 is in the range of 30-50ppm,microvia filling is facilitated,MPS and IML mainly active in microvia mouth and upper surface for microvia filling process,the EPE4500 acts mainly on the upper surface of the microvia.The results of microvia filling and electrochemical detection show that the increase of IML concentration in the composition of additives can inhibit the activity of part of MPS,IML can make MPS inactive.there is synergy between EPE4500 and IML.The research results of this paper will promote the development and application of electroplating additives.This will greatly promote microvia filling process,printed circuit board and electronic industry.