| Alumina ceramic substrate is known as one of the most promising materials due to its excellent properties such as high hardness,high thermal conductivity,high-temperature resistance and good insulation.It can not only be used as the carrier of electronic components,but also be used in military weapons because of its special molecular structure.However,the alumina ceramic substrate is difficult to modify its surface because of its complex structure,especially in the pretreatment process of the substrate,a large number of strong acids,strong alkalis or other corrosive chemicals need to be used for treatment.It will not only cause serious environmental pollution but also increase industrial costs.To solve this problem,a non-destructive and environmentally friendly pretreatment activation method was proposed,and the optimization of the method was carried out.This paper took the alumina ceramic substrate as the research object,used the activation method of non-destructive substrate to prepare a layer of nickel on the surface of alumina ceramic,and used the single factor method to determine the optimal range of various influencing factors.Then,the paper used the orthogonal experiment to determine the optimal pre-treatment operation process and the optimal pre-treatment process parameters to prepare the coating.The hardness,binding force,plating speed,resistance,corrosion resistance and other related properties of the coating were compared with those of the traditional nickel plating,and the result of optimal process steps for pre-treatment showed that the alumina ceramic substrate was placed in the oven at 450℃for 4 minutes and then took out,and the activation solution prepared by the ratio of nickel sulfate to sodium hypophosphite ion concentration of 1:5 was sprayed rapidly until the substrate recovered to room temperature,and in this case,the substrate surface can be covered with an activation layer with strong adhesion and relatively uniform distribution.The average plating rate of the nickel coating prepared by the optimal activation process is 10.93,10.85 and 8.76μm/h respectively after30,60,90 minutes of plating,and coating resistivity is 291.8×10-6,165.2×10-6,107.2×10-6Ω·cm respectively;The binding force and hardness of the sample coating after 90 min of plating are 32.83 N and 632 HV100g respectively.The properties are similar to those of the nickel coating prepared by the traditional process,indicating that this activation method can replace the traditional activation method.Therefore,it is an environmentally friendly and effective new activation method.In the process of electroless nickel plating on alumina ceramic substrate,this paper introduced the influence factors of magnetic field,probed into the influence of the change of magnetic field strength,direction of uniform magnetic field and non-uniform magnetic field on the related properties of the coating,and compared the differences of the related properties between the nickel layer prepared under magnetic field and under non-magnetic field.The results showed that:（1）Both uniform and non-uniform magnetic fields have certain effects on the surface morphology and other properties of electroless nickel coating,and different magnetic field directions will also have different effects on the properties of the coating.（2）Applying a uniform magnetic field during the electroless plating process,when the magnetic field direction is downward,the binding force and corrosion resistance of the coating are better than those prepared when the magnetic field direction is upward and are better than those prepared under no magnetic field.（3）Applying a non-uniform magnetic field during the electroless plating process,the magnetic field has the most obvious effect on the binding force and hardness of the coating.When the magnetic field direction is upward,with the increase of the magnetic field strength,the binding force and hardness of the coating show a downward trend,and both are less than the binding force and hardness of the coating under no magnetic field;When the direction of the magnetic field is downward,with the increase of the magnetic field strength,the binding force of the coating increases gradually,and the hardness of the coating decreases firstly and then increases,and is smaller than the hardness of the coating prepared under no magnetic field.However,the corrosion resistance of the coating prepared in the non-uniform magnetic field state and the coating prepared in the non-magnetic field state have significantly improved. |
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