Chemical silver plating solution for surface treatment of printed circuit board (PCB)

Abstract

The invention discloses a chemical silver plating solution for the surface treatment of a printed circuit board (PCB). The chemical silver plating solution (1L) comprises following raw materials by weight: 10 to 100 grams of complexing agent, 0.1 to 3.0 grams of Cu<2+>, 0.5 to 15 grams of surfactant, 0.1 to 5.0 grams of copper antioxidant, 0.4 to 1.0 gram of silver ion, enough nitric acid, which can adjust the pH of the silver plating solution to 0.08-0.3, and the balance being distilled water. The chemical silver plating solution can form a silver layer on the copper circuits on a printed circuit board; the thickness of the silver layer is uniform and is in a range of 0.15 to 0.3 millimeter; after the surface treatment, other elements can still be welded on the PCB; the color is not changed after five times of reflow soldering; less than 10% of the thickness of copper layers of copper wires is corroded; and the processed PCB will not be corroded and the color will not change after thePCB is placed in neutral salt fog for 24 hours.

Description

technical field [0001] The invention relates to the production field of printed circuit boards, more specifically, the surface treatment process of printed circuit boards, and an electroless silver plating solution for soldering the copper circuits of the circuit boards. Background technique [0002] Nowadays, HASL is no longer suitable for the design of thinner PCB and denser lines, so there have been many researches on functionally optional products. The increase in the use of the nickel immersion gold process has eliminated tin spraying, but the nickel immersion gold process is difficult to operate and expensive in PCB production. Organic solder protection is easy to operate and low in cost in PCB production, but it is limited in assembly, such as assembly board electrical testing and flux matching. Electroless silver plating can make the circuit very flat, suitable for high-density circuit, fine-pitch SMT (surface mount), BGA (ball array package) and chip direct mountin...

AI Technical Summary

Problems solved by technology

The increase in the use of nickel immersion gold process has eliminated tin spraying, but the nickel immersion gold process is difficult to operate and expensive in PCB production

Organic solder protection is easy to operate and low in cost in PCB production, but it is limited in assembly, such as assembly board electrical testing and flux matching

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