Tin-Lead Plating and Solder Plating

Tin-Lead Plating is often engineered specifically for rack and barrel plating. It is whisker resistant and the process involved for this type of plating is extremely versatile. It results to a bright and consistent deposit and comes with a wide current range of density.

 

Tin Plating Has a Shelf Life

 

Basically, Tin-Lead Plating is a process of tin plating a lead component, thus, making soldering even easier. A lot of people are aware of this, but what they are not aware of is that tin plating actually has a shelf life. Soon enough, its ability to be easily soldered will degrade over time. Furthermore, the speed as well as the severity of degradation will depend both on the storage conditions as well as on the plating itself. The manufacturer of the component as well as the user will share the responsibility for the shelf life of the tin plating. The manufacturer should also use plating where the thickness is less prone to rapid degradation. Ideally, this would mean avoiding the high temperatures. Furthermore, the user must also understand the shelf life sufficiency of the Tin-Lead Plating so that the components will be used before the soldering failure will take place.

 

Basics of Soldering

 

Soldering would require bringing together the liquid tin lead solder as well as the components that are being soldered. The tin or the Tin-Lead Plating will provide a surface that can be soldered for a longer time. At the typical soldering temperatures of 250 up to 260°C,   the plating will melt and alloy with a molten solder, which, as a result, wets the substrate. Wetting is the process where the water wets the wood. This is essential even with the Solder Plating process. A surface that cannot be wet, like the glass which cannot be possibly wet by water, and thus, it cannot be soldered. Oxides are also not possible to be wet.

 

Process of Soldering

 

When it is exposed to temperatures that are below the melting point of the Solder Plating, the solder will slowly dissolve the tin plating. The Bond integrity will pretty much depend on how well the solder as well as the substrate and under plating will bond. The interaction of the molten solder towards the copper substrate and the nickel under plating will create a copper tin and nickel tin intermetallic.

 

The Solder Plating bonds will depend on the solder's Tin being soluble or in capable of forming a metallic bond towards the material that is being soldered. Solderabilty will demand that the plate surface will be clean and will remain clean and can be wet by the solder as well as the flux.

 

Loss of Solderability

 

The most common of solderability failure is that 5% of the solder surface will not be soldered. Loss of solderability in Tin as well as Tin Alloy plating often comes from these three conditions: high level of co-deposited carbon, excessive thickness of the metallic layer and the excessive amounts of oxides as well as other surface contaminants on the Tin-Lead Plating.