Study On Preparation Technology And Property Of Electroless Composite Alloy Plating Technology Of Gold Finger Test Piece

Gold finger test wafer is a component to evaluate whether the gold finger qualified. China is a biggest country of using gold finger test wafer, but the gold finger test wafers we are using now almost all come from import, the price is very highly. The home-manufacturing process of gold finger test wafer is significant. We studied the gold finger test wafer that been widely used on the market, learned that the basis material is pure copper, then plating Ni, Pd, Au on its surface in proper order.On this basis, we make out process plan about imitate gold finger test wafer and studied it, including pretreatment, acid electroless Ni-P coating, electroless Pd plating and cyanide-free electroless Au plating.Pretreatment process are ultrasonic cleaning with acetone, alkaline degreasing,pickling and induce activation 1 min with iron wire in plating bath.The optimized basic formula of electroless Ni-P plating by orthogonal test design method are Ni SO4·6H2O 30g/L, Na H2PO4·H2O 30g/L, CH3 COONa 30g/L, C3H6O312ml/L, Na3C6H5O7 10g/L, C3H7NO2 3 ~ 6ml/L, CN2H4 S 4 ~ 6mg/L, p H 4.7,temperature 82.5℃, rate of agitation 180r/min. Preparation Ni-P coating under this formula, the results show that the coating show smooth surface morphology, some cellular structure are distributed uniformly in the coating. Meanwhile the coating thickness is uniform and compact. The structure of the coating belongs to the mixture of crystalline and amorphous structure. After heat treatment, the structure of Ni-P coating has gradate from mixture structure of crystalline and amorphous to crystalline structure, and the diffuse of elements may be found between basic material and coating, the microhardness and the adhesion all get improved.The optimized basic formula of electroless Pd plating by orthogonal test design method are Pd Cl2 3g/L, HCl(38%) 6m L/L, NH3·H2O 168 m L/L, NH4 Cl 28g/L,Na H2PO4·H2O 12g/L, p H 9.7 ~ 9.9, temperature 55 ~ 60℃. Preparation Pd coating under this formula, the results show that the coating show smooth surface morphology,the coating thickness is uniform and compact, some cellular structure are distributed uniformly in the coating. The structure of the coating belongs to crystalline.The optimized basic formula of cyanide-free electroless Au plating by orthogonal test design method are Na3Au(SO3)22g/L, Na2SO3 36g/L, Na2S2O3 12g/L, CN2H4S1g/L, Na2B4O7·10H2O10g/L,(CH2CH2NH)n 2g/L, C2H8N2 2g/L, temperature 75℃~80℃, p H 6.5~ 7.0. Preparation Au coating under this formula, the results show that the coating show smooth surface morphology, the coating thickness is uniform and compact, some cellular structure are distributed uniformly in the coating. The structure of the coating belongs to crystalline. Extended tine, can improve the conductivity and corrosion resistance of composition coating.After heat treated, the structure of Ni-P coating in composite coating has gradate from mixture structure of crystalline and amorphous to crystalline structure, the conductivity and corrosion resistance of composite coating get improved. Then,compared the composite coating with original gold finger test wafer, the results show that the composite coating is similar to original gold finger test wafer in coating composition, components of organization, crystal structure and performance, satisfied the experiment requirements.