Nickel Plating GOLD Plate Does not Solder-Reason Analysis
Nickel plating gold plates are a demanding finishing procedure that requires precise material selection, correct surface preparation, and proper plating protocols. Gold plating has 3 main attributes: improves appearance, improves soldering and improves electrical integrity. If the gold plating does not solder, then something is missing in the finishing protocol.
The gold solderability layer, for any gold plating thickness, depends on two critical process steps: substrate/interface material selection and proper surface preparation. Poor surface preparation typically results in increased gold thickness build up in areas or cracks, ultimately leading to separation of the gold plating from the interface material due to oxidation and lack of adhesion.
A good substrate material is paramount to the success of solderability. Poor substrate selection, typically caused by inadequate surface large grain, can lead to poor solderability. Non-conductors, such as plastic, glass, and different ceramic boards, can increase insulation and reduce conductivity, creating conditions incompatible with soldering gold plated components.
From a physics perspective, the solder needs to melt faster than the interface material. If the melting point of the material is higher than the solder alloy, de-wetting/globing will occur. A poor interface layer or poor surface preparation can result in a non-uniform, thicker gold layer, which ultimately increases the melting point of the plate, making it impossible to melt the solder alloy and reflow the solder. Poor bonding can also be the result of poor solder composition or incompatible solder alloys. A poor flux can also inhibit solder reflow.
Nickel Plating is an efficient and cost-effective method for adding a hard and durable finish to metal surfaces, as well as to plastics and other materials. The gold plating process often involves washing and degreasing the component parts prior to the actual plating process. This is done to remove any oil, dirt or other impurities which can adversely affect the plating. The nickel plating solution consists of a combination of acids and salts, which are mixed and heated to facilitate specific surface treatments. The component parts are then placed into the nickel solution to receive the desired plating.
After plating, they are removed and rinsed with water to remove any residual plating solution. The gold plating is then applied, usually by immersion in a heated bath containing electroless gold plating solution. It is important to monitor the parameters of the bath, such as temperature and pH, to ensure optimal plating. It is also important to note that gold plating is not recommended for use in areas with high moisture or corrosive environments.
Finally, post-treatment of the gold plating is critical to ensure that the desired characteristics are achieved, such as solderability and electrical integrity. Following the specified plating protocol is essential to ensure successful post-treatment. This includes functional/performance testing of the gold plated assemblies and/or components to validate the quality of the plated surfaces.
In conclusion, if gold plated components do not solder correctly, the most likely culprits are poor interface material selection, inadequate surface preparation, flux incompatibility, and incompatible solder alloys. It is therefore important to properly evaluate these criteria to ensure the reliability and quality of the end product. With proper substrate preparation, plating protocols, and post-treatment protocols in place, nickel plating gold plates can provide a reliable and durable finish as well as improve solderability, electrical integrity, and aesthetics.
