The Method And Electrochemical Analyze Of Nickel Electroless Plating On Diamond Particles

Due to its ultra-high hardness, high thermal conductivity, low density, andthe thermal expansion coefficient matching with the semiconductor matching withsemiconductor, diamond has become a focus of research and development materialsin cutting and polishing techniques. However, the diamond is poor with the substratein wettability, high surface energy and the weak adhesion have seriously affects onthe using of the diamond in the packaging industry. The researchers at home andabroad make every efforts to use a variety of method to induce surfacematerialization treatment on the diamond for a long time. Electroless platingtechnology has made an increasing important role in surface treatment industry. It iswidely used in the electronics, machinery, aerospace, and many other areas.Electroless plating otherwise also called no electrolytic plating or autocatalyticplating, and its essence is a redox reaction. This article mainly introduces themethods using chemical nickel plating to modify the diamond surface and theinfluence of different technological parameter on chemical nickel plating. Andelectrochemical methods were used to study the influences of these parameters onthe anodic polarization curve.Synthetic diamond crystals with particle sizes of10μm are applied in thepresent work. Before plating pretreatment was carried out on the diamond crystalspowder. Preprocessing steps are washing, coarsening, activate the sensitization (colloil Palladium activation method), dispergation. Activation of sensitization is the keyto pretreatment. The success of pretreatment is the key to the electroless platingnickel. Using orthogonal experiment results the best recipe, electroless nickel platingsolution was: NiSO4·6H2O concentration,25g/l, sodium hypophosphiteconcentration,30g/l, lactic acid concentration,15ml/l, sodium acetate concentration,15g/l, thiourea20mg/l, temperature of85degrees C, pH of5.5.Main conclusions obtained from this article through research are as follows:(1) The process for electroless copper plating can be divided into three stages: the initial reaction (incubation period of crack nucleation), the reactionmedium(nucleation period), the later stage reaction. The whole reaction process, thehigher the temperature, the faster the reaction rate,90degrees C when the weightratio is four times as large as70degrees C.(2) When stabilizer thiourea is20mg/l, it can effectively inhibit metaldeposition rate, reduce nickel plating nickel on the surface of the bubble.(3) Time, increased concentration of sodium phosphite and the rise. oftemperature and pH value, can shorten the reaction time, improve the diamondweight ratio.(4) The pH value and the concentration of sodium sodium hypophosphite havegreat effect on the diamond surface the morphology of nickel plating layer throughdifferent mechanism. Nickel plating layer appear obvious plating leakagephenomenon, when sodium monophosphate concentration is20g/l; When sodiummonophosphate concentration is30g/l, the best quality of nickel layer is achieved.Increasing the concentration of sodium hypophosphite continuously higher than35gl/l, thickness of nickel layer ascends, as a small amount of free nickel appears inthe solution. Free nickel residues appear while pH rises to6.5. Uniform and smoothlayer without plating skip or free nickel residues can be obtained at pH of5.5.(5) The impact of plating time on the coating thickness is also apparent., thecoating thickness is thinner and not full of diamond-coated with plating five minutes.longer than30minutes, the coating is thicker and the nickel foam grow on thediamond surface. So choose the best plating time is between15to25minutes.(6) The pre-treatment, stirring speed, loading and impurities have a certainimpact on electroless nickel on diamond.(7) In the measurement of anodic polarization curve of sodium hypophosphite.With the rise of either pH value or temperature, the oxidation peak potentials of theanodic polarization curve shifts negatively, and the peak current density increase.Thiourea have less impact on sodium hypophosphite polarization anodic curves,which helps stabilizing plating bath.