One of my first neighborhood jobs growing up was washing cars. With my dad’s trusted shammy, I would go around the block cleaning exteriors and vacuuming interiors to save a few bucks for video games. Part of my toolkit was wax – I didn’t understand its true purpose, but I could see the difference between a waxed car and an unwaxed car a mile away. Later, I would learn that much more than just leaving a car looking good, wax offered a protective layer to the elements.
Much like an exterior coat on a washed car, PCB surface finishes protect against environmental contaminants that can detract from the long-term reliability of the solder joint. There’s an added benefit, however: surface finishes improve the baseline solderability, creating a superior joint from the get-go. As such, the process is vital to ensuring a successful assembly during manufacturing and a long service life.