Research On Electroless Copper Based On Dual Complexant And Self-assembly Technology

Electroless plating refers to the autocatalytic or chemical reduction of aqueous metal ions and subsequent plating onto substrate,also known as auto-catalytic plating.Electroless copper is one of important basic process in manufacturing industry,nowadays,electroless copper process is dominated by a single complexant system,and the space for dynamic regulation is very limited,with problems such as low plating rate,rough surface and large grain size,thereby the idea of electroless copper with EDTA/THPED dual ligand system was proposed,and the electrochemical behavior of this system and its effect on the coating structure were studied via selecting ligands and adjusting ratio of ligand,so as to optimize electroless copper process to obtain controllable deposition rate,smooth surface and uniform grain size.In addition,kinetics and texture influence of of additives in dual ligand system was fewly systematically studied,so deposition characteristics of additives were investigated in this thesis.Based on these research results,copper matrix composites was prepared.In order to solve the problem of corrosion of new electroless Cu coating,we assembled organic monolayers using organic phosphonic acid and octadecylthiol.The specific results are showed as following.(1)The electrode process and structure evolution of electroless copper plating with EDTA/THPED dual ligand system had been systematically analyzed.Fall-off value of mixed potential(?Emix)was presented as one of thermodynamics parameters,and whole electrode process was divided into three reaction regions,these were induction region,transition region and stable region according to variation trend of ?Emix.Complexant,Cu2+,OH-and formaldehyde were found to have a great influence on deposition behavior,increasing of four components concertration led to growth of ?Emix,the corresponding reaction current density also largen,so deposition reaction was accelerated.The addition of THPED made crystal deposition to appear mode of upward growth,and made preferred orientation on(220)lattice plane,while formaldehyde made(111)preferred orientation,no any preferred orientation for OH-and Cu2+ happened.When temperature of bath rose,the rate increased about 34%from 35? to 55? and the grain size grew.(2)The kinetic relation of chemical copper plating solution in dual complexant system was summarized as follows:The impact of the main components on the kinetics of electroless deposition listed as follows:[Cu2+]>[OH-]>[HCHO]>[ligand].The deposition reaction was controlled by diffusion process of copper ion.The main components and parameters of electroless copper using dual complesant were optimized.(3)Additives played important role in electroless copper solution,behavor of stabilizer,accelerator and surfactant on deposition process was studied.Stabilizers,including 2,2'-pyridine,K3Fe(CN)6 and K4Fe(CN)6),made ?Emix fall off 0.0213V to 0.1093V due to its concertration.Stabilizers made deposition rate slow down,and had the effect of preferring orientation on(220)lattice plane and refining grain,which was related to the directional adsorption of the stabilizer,i.e.preferential adsorption on the(111)and(200)crystal planes.The stability effect of the stabilizers was related to its concentration,and in turn:K3Fe(CN)6>K4Fe(CN)6>2,2'-pyridine.PEG6000,as surfactant,was similar to stabilizer in electrode process and structure pattern,which was related to block the adsorption of reaction charged ions because stabilizers and surfactant adsorbed on copper surface.Sodium 3,3'-dithiodipropane sulfonate(SPS),as accelerator,made ?Emix increasing from 0.0675V to 0.0919V,at this time,cathodic reduction was the control step,SPS promoted rate of cathodic reduction reaction,so SPS improved the rate of copper deposition.XRD showed that the addition of SPS favored the formation of preferred orientation on(200)lattice plane.(4)Copper matrix lubrication composites of flake graphite and MoS2 were prepared via EDTA/THPED dual complexant electroless copper system.Accompanying increase of copper content in the Cu-flake graphite materials,electrical conductivity improved accordingly,and resistivity fell down from 0.35??·m of 50%Cu to 0.072?Q·m of 80%Cu,but the wear rate and friction coefficient increased about 40%.Doping Cu-MoS2 into Cu-graphite made resistivity up slightly and wear down,and copper layer of doped material presented tight three-dimensional continuous structure.The copper-synthetic diamond superhard composite material is also prepared by this system,its coverage is better than the single EDTA or THPED complexant system.(5)Monolayers of organic phosphonic and alkyl mercaptan were assembled on new electroless Cu surface by pulsed constant-voltage enhancement(PCVE),and its electrochemical&spectral properties and wettability were tested.Results showed that the corrosion current of organic phosphonic acid and alkyl thiol SAMs prepared by PCVE decreased 90.2%and 99.99%respectively,and EIS up to 21 and 31,000 times respectively,the self-assembled film inhibited the anodic process of the corrosion reaction,which made control step from oxygen diffusion changed to interfacial charge transfer..FT-IR spectroscopy confirmed that the organic phosphonic acid and alkyl mercaptan molecular were successfully assembled on Cu surface.Contact angle test indirectly verified two substances had been assembled onto electrode surface,and wettability changed from hydrophilic to hydrophobic,contact angle increased up 400 and 540 respectively.This indicated that PCVE made SAMs film denser and better corrosion resistance relative to immersing sample.