The invention discloses new semi-bright lead-free chemical
tinning liquid and a using method thereof. A semi-bright silver
tin-
copper alloy chemical plating layer is obtained on
copper and
copper alloy matrix. In the
chemical plating liquid,
tin sulfate is used as a main salt,
thiourea is used as a main complexing agent,
citric acid is used as an auxiliary complexing agent,
sodium hypophosphite is used as a
reducing agent,
ethylene diamine tetraacetic acid is used as an
antioxidant,
sulfuric acid is used as a stabilizing agent,
gelatin is used as a leveling agent, and
benzaldehyde is used as an auxiliary brightening agent. The pH value of the plating liquid is 0.8 to 2.0, the temperature of the plating liquid is between 80 and 90 DEG C, the
carrying capacity of the plating liquid is 0.8 to 1.5dm2 / L, and the mechanical stirring speed is 50 to 100 rpm. The continuous self-catalytic deposition of
tin is implemented on the copper and
copper alloy matrix, plating
layers of different thicknesses can be obtained by controlling the
chemical plating time, and the deposition speed is high; crystalline grains are obviously refined, the
surface flatness of the plating layer is improved, and the plating surface area is large; the plating layer and the matrix are combined firmly; and after passivating treatment, the change resistance of the plating layer is high. The technology has broad application prospect in products such as
deep hole pieces,
blind hole pieces, small-sized electronic parts and components which are difficult to process, printed circuit boards (PCB) and the like.