Thin Au Film Deposition by Laser-Induced Electroless Deposition: Mechanism, Interfacial Bonding, and Performance

Gold plating on stainless steel is extensively utilized in the electronics industry. Chemical gold plating, a prevalent method for plating preparation, offers advantages such as being a straightforward process. However, it often suffers from performance issues, particularly low adhesion strength, which hinders its widespread adoption. This study employs a laser-induced chemical deposition process to fabricate a localized thin gold coating on a 316L stainless-steel substrate using an ammonium sulfite gold-plating solution. The mechanisms of induced deposition and coating interface bonding are examined, and parameter optimization tests are conducted with surface morphology as the evaluation criterion. The research demonstrates that laser-directed removal of the oxide film on the stainless-steel surface, coupled with substrate remelting activation, facilitates an exchange reaction between Fe, Cr, Ni, and other elements in the activated area and Au(SO₃)₂^3–. This process successfully deposits a continuous and dense gold film. A transition layer, approximately 1 μm thick, forms between the gold film and the substrate due to remelting, resulting in an amorphous Au–316L alloy. This transition layer enhances the adhesion of the gold film to the substrate, achieving a bonding strength of 15.2 MPa, which is comparable to the 15.9 MPa bonding strength of laser-induced electrochemical deposition (LECD) coatings. In contrast, the bonding strength of electrochemical deposition (ECD) coatings is less than 0.5 MPa.