Gold and silver are among the most popular finishes for plating electronic components such as connectors and contacts. Why? They are the most noble (aka stable) metals, though each comes with its own set of benefits and drawbacks. When considering the crucial role that contacts and connectors play within an electrical system – it’s important to specify the proper one. The material must perform as intended, and last a long time. This is especially true for mission critical applications such as aerospace, defense and medical. Finish selection for a particular component depends on several key factors. Besides use, these include: conductivity, corrosion resistance, durability, wear, contact resistance, solderability, appearance and of course, cost.
Let’s start with gold. The greatest advantage gold has is high resistance to corrosion, tarnishing and oxidation. Gold is less conductive than silver. Though it allows for reliable signal transmission, making it great for data applications. It is well suited for low voltage uses, and most notably, corrosive environments. Gold is soft, and can be easily alloyed. Very small amounts of nickel or cobalt, less than 1%, are typically added to make “hard gold”. The increased strength mitigates friction wear issues, which is important in applications where connections are frequently coupled and decoupled. Want to take a guess at gold’s biggest disadvantage? You got it – cost! Further, the price fluctuates day-to-day due to economic conditions and investor sentiment. However, for many applications – there is simply no substitute for gold. The cost is usually outweighed by its corrosion resistance, durability and additional long term benefits.
Let’s talk silver. It offers the highest electrical and thermal conductivity. It also boasts the lowest contact resistance, and lower material cost than gold. Silver’s conductivity properties make it ideal for high current contacts and intermodulation applications. Silver is also the finish of choice for parts that are soldered or brazed. Ready to take a guess at its biggest drawback? Hint: the answer is likely lurking in your dining room or kitchen. Silver develops an oxide layer and tarnishes over time, which negatively affects its electrical properties. This must be considered when weighing the relatively low cost of silver against gold.