Research And Application Of THs Electroplating Leveler For Printed Circuit Board

Printed Circuit Board(PCB)is an essential part of various electronic information products.Its major role is to support and interconnect circuit components.Moreover,the growing consumer demand for electronic products in terms of intelligence,thinness,miniaturization,and multifunctionality has driven printed circuit boards to continue to develop in the direction of high precision,high density,and high reliability.Through-holes(THs)electroplated copper is one of the"bridges"connecting layers of multi-layer circuit boards,and has important guiding significance for the next generation of advanced printed circuit boards.However,when direct-current power supply is used for THs plating,the uneven distribution of current density and poor mass transfer of the plating solution in THs will cause the failure of TH plating technology,and an effective way to change this phenomenon is to add appropriate additives to plating solution.In the domestic market,the immature technology of THs electroplated copper and the shortage of organic additives have made finding a new and effective additive formula a very practical and valuable task.In this paper,a new low-molecular-weight nitrogen-containing compound called 2,2’-dithiodipyridine(DTDP)was selected as a leveler.Additionally,the effect and mechanism of this compound in the process of copper electroplating have been investigated by means of some testing methods,such as dynamic simulation(MD simulation),quantum chemical calculation,X-ray photoelectron spectroscopy(XPS),electroplating,electrochemical measurement,atomic force microscope(AFM),scanning electron microscope(SEM),etc..The major study contents and results of the thesis are as follows:1.In this paper,quantum chemical calculations and MD simulations are utilized to theoretically calculate and simulate the adsorption of DTDP molecules on the copper surface.The results manifest that DTDP molecules not only have plentiful active sites such as N,S,and pyridine rings,but also can be adsorbed on the copper surface in parallel and have strong bonding ability with the copper surface,which implies that DTDP molecules can form an adsorption film on the copper surface during the electroplating process,thereby reducing the contact between copper ions and the cathode surface and hindering the deposition of copper ions on the cathode surface.Secondly,XPS element detection and AFM test results show that the N-Cu structure may be formed on the copper surface after being soaked with DTDP molecules,and the DTDP molecules are more likely to diffuse to the convex position of the copper surface and have a large amount of adsorption,which results in a greater supression of copper deposition,and vice versa.This makes the copper deposition speed at the convex position of the copper surface lower than that of the concave portion,resulting in a flat copper surface.Based on the above results,DTDP molecules can theoretically be used as a potential leveler.2.The electrochemical measurement data of the plating solution formulations containing different concentrations of DTDP molecules explained that DTDP molecules can form an adsorption film on the copper surface,thereby increasing cathodic polarization,and enhancing the inhibitory effect of inhibitors on copper deposition.The results of SEM tests and roughness simulations illuminate that within the appropriate range,an increase in the concentration of DTDP molecules can reduce the average roughness of the coating surface and make the coating surface flat.All the experimental results provide cogent date support for the conjecture that DTDP molecule can act as a leveler.3.The predicted leveler and the designed plating additive system were applied to hole-filling electroplated copper experiments of THs with low depth-diameter ratio,thereby verifying the conjecture of DTDP molecule as a leveler,and finding the parameter combination of additives with the best hole-filling performance.The results of single factor and orthogonal optimization experiments illustrate that small changes in the concentration of additives have a significant effect on the plating performance.Only when the concentration of the four additives of Cl~-,SPS,PEG-10000 and DTDP are 60mg/L,8 mg/L,250 mg/L and 13 mg/L respectively,the performance of hole-filling is the best,and its average hole-filling rate is as high as 91.7%.Using the throwing power as an index,orthogonal experiments were performed to optimize the plating additives for THs with different high depth-diameter ratios.The results expound that when the depth-diameter ratio is approximately 10:1 and 8:1,the optimal parameter combination of the additive comprise 5 mg/L SPS,250 mg/L PEG,60 mg/L Cl~-,2 mg/L DTDP,and the corresponding throwing powers are as high as 112.9%and 110.0%respectively;when the depth-diameter ratio is 6.7:1,the composition of its optimal parameter combination is 3mg/L SPS,200mg/L PEG,60mg/L Cl~-and 2mg/L DTDP,and its throwing power can reach up to 103.4%.