Silver Plating of Copper or Copper Alloys – Silver Properties
Silver plating of copper or copper alloys is a highly functional finish for transferring heat and electricity utilized across a wide breath of industries. Silver has been applied since late 1800s onelectrical switchgear and other components that pass electrical current. In recent years silver plating of copper electronic components including connectors and terminals has grown rapidly within the electronic, automotive and electric vehicle (EV) markets. Silver plating has many unique properties that make it desirable for these applications. The primary reason is that silver has the highest electrical and thermal conductivity of any metal, which facilitates the efficient transmission of electricity and heat. In addition, silver is a relatively soft metal which allows the silver deposit to compress and form around a mating connecter filling small voids and micro-roughness. This increases the effective contact area resulting in less overall connector resistance.
Figure 1: Conductivity of Silver as Compared to Copper and Other Metals
Silver has excellent lubricity and resists galling in switching, sliding or rotary applications. However, high pressure wear surfaces such as blade-style stab connectors can be susceptible to silverwear. In applications such as this, a higher deposit thickness of silver is recommended as well as the use of a nickel or electroless nickel underplate. Thinner silver plating without a nickel underplate is best used on static joints or low duty cycle connectors that are mated and unmated relatively infrequently.
Silver Plating of Stainless Steel – Silver Properties
Silver plating on stainless steel and other high temperature alloys such as Inconel®, Nitronic® and Hastelloy® is a common silver plating service for nuts, fasteners, slip-rings, thrust-washers, bushings and other bearing surfaces that benefit from the lubricity of silver at high temperatures allowing parts to exhibit anti-galling and anti-seizing properties. Silver is a unique precious metal that exhibits many desirable properties for utilization across a broad range of engineered applications. Of all metals, silver has the highest thermal conductivity, electrical conductivity, and optical reflectivity in the visible portion of the electromagnetic spectrum; silver has outstanding temperature resistance with a melting point of 962° C (1763° F). Additionally, silver is a soft, ductile metal with good embeddability that performs well under high torque and loads. Silver also provides excellent solderability and brazing characteristics for joining applications of stainless steel and other high temperature alloys. The unique combination of lubricity, high temperature resistance and thermal conductivity make silver plating on stainless steel and other high temperature alloys an outstanding combination for high temperature fastening or bearing applications where heat transfer high temperature lubricity are the principle design considerations.
Silver plating is often used for cosmetic applications and is found on items such as silverware and jewelry. While silver provides value and an aesthetic appearance to these items, it is also used in multiple sub sectors of manufacturing – Power Transmission, Oil & Gas, Medical, Telecommunications, Aerospace, Electronics and many more. The reasons silver plating is used is vast: ductility, electrical and thermal conductivity, solderability, high temperature lubricity, as well as excellent optical reflectivity. Although there are many positive attributes to silver plating, silver tarnish is one is a common occurrence when the proper steps are not taken.
Wire bonding is a method in which connections are made between components and/or the leads of a lead frame with extremely fine wires. The wires are typically aluminum or gold, but also include copper and silver. There are three common types of bonding, thermocompression, thermosonic, and ultrasonic. Thermocompression uses force, time, and heat to join metals together, while thermosonic uses force, times, heat, and sonics, and ultrasonic bonding uses force, time, and sonics. In any of these instances the most important aspect of bonding is to form a good metallurgical bond with the wire and the metal substrate. Continue reading →
Silver plating offers a range of physical and electrical properties that make it extremely useful for industrial applications. Due to the current increases in the cost of other precious metals such as gold, palladium and rhodium, silver is a cost-effective alternative precious metal for various electrical, thermal and mechanical applications. For these reasons, silver has continued to grow as the finish of choice for various product designs and applications.
Silver has extremely high electrical and thermal conductivity – better than that of gold – which has solidified its use in high current power transmission and lower current power connector applications. Silver also is an excellent high temperature lubricant and can be utilized for various high temperature anti-galling applications within the bearing or fastener industries. Continue reading →