Electroplating is among the most critical processes used in modern manufacturing today. And with the Internet of things, more and more devices connect to provide instant access to information and data. Also, this ‘Gold VS silver plated connectors’ article may help you to understand certain differences.
Gold VS silver plated
Any electrical device’s effectiveness and reliability depend highly upon the quality of the connections. And, specifically, the plating used on the connector or contacts. Also correct electrode position is vital to ensuring a device performs reliably. Whereas improper plating can negatively affect the electrical device’s performance, utility and durability.
Gold and silver are two standard electroplating processes that produce highly reliable and conductive connections. And when plating electrical components such as connectors and contacts. However, there are advantages and disadvantages between silver and gold plating services. For example, gold and silver are highly conductive and corrosion resistant. Also, Silver will form a sulphide compound (tarnish), and gold can be a costly option.
Benefits of Gold
Gold is a highly noble, and un-reactive metal that can enhance connectors’ performance in various electrical applications. Also, Gold’s resistance to oxidation or corrosion is exceptionally high compared with other metals. Therefore, in situations where the contacts of a connector are likely to be exposed to corrosive substances or conditions. Gold plating can serve as an effective barrier to oxidation and corrosion. As a result, gold-plated connectors are an excellent choice for more corrosive applications.
And applications include high-humidity environments or applications with frequent thermal cycling and corrosive salts or acids exposure. In the later application, a heavier gold deposit or even duplex gold deposit ensures sufficient gold. And to eliminate any porosity in the sediment, thereby forming an effective barrier to corrosion.
Electrical Conductivity
Besides copper and silver, gold is the third most conductive metal in the world. However, gold does not produce any oxides or other compounds. And it maintains its high conductivity even at elevated temperatures or when exposed to corrosive environments. Furthermore, gold’s high/consistent conductivity ensures stable current flow. Even at very low voltages, making gold an excellent choice for electronic applications.
Enhanced Durability
Electroplated gold can be alloyed with small amounts of nickel or cobalt to increase the hardness. From pure gold (< 90 Knoop) to as high as 200 Knoop. Hard gold can provide a durable coating for repeated connection cycles. Especially when plated to a sufficient thickness (> 50uin) over an electrolytic or electroless nickel base. In addition, hard gold is not prone to fretting or galling due to its natural lubricity.
Ductility
Because gold is such a malleable metal, it’s suitable for flexible connections and springs. In addition, gold’s flexibility makes plating more likely to hold up to multiple contact cycles. However, gold-plated electrical connectors or springs require a suitable under-plate material to guarantee the finish. Therefore, it is recommended that an engineered nickel, such as a sulfi-mate nickel, be used as an under-plate to gold when plating a flexible contact or spring.
Solderable Deposit
Gold plating is an excellent finish for forming reliable solder joints. And will consistently and evenly wet using a mild rosin flux without acid activation. Also, Gold can be plated on nearly any substrate. Including stainless steel terminals or connectors, to allow for subsequent joining through soldering. Generally, only a thin deposit of soft gold of 0.00001 inches per side is required to form a reliable solderable gold contact.
The gold plating diffuses into the solder joint through solid-state diffusion when soldering to a gold electrode-posit. Because of this phenomenon, care should be taken to not exceed 3% by weight gold in the solder joint. As this can cause embrittlement within the joint itself. And as a general rule, deposits of < 0.00005 inches per side will result in less than 3% by weight gold in the solder joint. And as a final point, gold is not magnetic. Also, is advantageous in scenarios where electromagnetic fields can create interference. For instance, gold plating may be suitable for connectors in medical equipment like Magnetic Resonance Imaging (MRI)
Industry Applications
Most electronic devices utilise gold-plated contacts or terminals. Because this precious metal has several fundamental properties. And makes it a valuable material. However, the electronics and interconnect industries are the primary users of gold. And because it performs an essential function in keeping electronic components working effectively over time. Gold is found in various electrical devices, including cell phones, desktops, and laptops. And there are about ten troy ounces (or 3/5 pounds) of gold. Approximately five troy ounces of gold are worth over $9,000 in 200 computers.
Because of its capacity to maintain electrical connectivity, gold is well-suited for use in a wide range of electronic applications. And can be applied to any part of a device that requires a reliable electrical connection. For example, external components such as electrical connectors most commonly feature gold plating. In addition, however, gold is used in the circuit boards of electronic devices. Any device’s reliability depends on the integrity of its circuit board connections. As such, electronics manufacturers apply gold plating to their circuit boards to improve conductivity and prevent corrosion. 99.9% pure gold plating or soft gold. And commonly used in pad connections or where wire bonding is required.
The Benefits of Silver-Plated
Similar to gold, silver is a precious metal that provides a very conductive surface while forming an effective barrier to corrosion. Silver’s primary advantage is that it is about one-hundredth the cost of gold, which allows for a broader range of use and plating at higher thicknesses than gold. The primary disadvantage of silver is that silver is a semi-precious metal and forms sulphur compounds. Such as silver sulphide or tarnish which can affect the conductivity of the silver electrode deposit over time.
Thermal Conductivity
Because of its high conductivity and lower cost, silver is the ideal precious metal for certain applications. Where high power transfer of electricity is a design requirement. And examples include plating of current exchange bodies. Also, fuse cutouts, stabs, terminals, bus bars or other high-power connectors. And, in addition, because of the lower cost, plating larger copper or aluminium conductors with silver is not cost prohibitive. Providing a very reliable precious metal coating that resists oxidation and produces low contact resistance.
Protection
Like gold, silver is a precious metal that can form an effective barrier to corrosion. And because of the lower cost, silver can commonly be plated to thicknesses exceeding 0.001″ per side. Creating a very pore-free precious metal barrier to corrosion. In addition, silver is widely plated over an electrolytic or electroless nickel barrier. And when plated over copper or aluminium conductors, silver forms an effective barrier to prevent the substrate materials from forming compounds.
Superior Lubricity
Silver is a natural metallic lubricant which provides outstanding lubricity even at extreme temperatures. Also, Silver is an excellent choice for applications such as high-temperature threaded or sliding contacts. Silver is commonly used for plating stainless steel and other high-temperature alloys to prevent seizing. Silver provides outstanding sliding lubricity on high-contact pressure switches or contacts, including fuse pads, stab connectors, or high-pressure socket connectors. And in addition, using a lubricous nickel under-plate can further enhance the lubricity and wear properties on a connector or contact.
Industry Applications
Silver plating’s outstanding electrical and lubricating properties used in switching electrical power applications in industrial settings. Because of its relatively low cost and good conductivity, excellent lubricity and corrosion resistance, silver plating is suitable for a wide range of applications. There are more applications for silver electroplating than any other plated precious metal. And mainly due to silver’s low-cost relative to other precious metals such as gold, platinum, palladium or rhodium. The growing use of electrical power in applications such as electric vehicles and electronics makes the future demand for silver very high. And projected that need for silver plating would continue to grow exponentially over the upcoming years.
Under-plates
Before plating silver or gold, using an underplate of another metal is common. Under-plates can improve corrosion resistance, create a structural base for the subsequent precious metals deposit. And improve overall conductivity and help prevent diffusion of elements such as zinc from the substrate into the ultimate precious metals deposit. A few examples of metals used as under-plates before gold or silver plating include:
● Copper: Copper plating is an excellent under-plate metal for effectively sealing the base substrate to promote adhesion, conductivity and corrosion protection. It can coat a wide range of metals and promotes substrate cleaning as it plates due to its cyanide-based formulation. Also, being an excellent electrical and thermal conductor, copper can help promote the current carrying capacity of a conductor.
● Electrolytic Nickel: When gold or silver plating copper or copper alloys such as brass, substrate elements, including copper and zinc, can migrate into the gold or silver deposit. And over time can form an intermediate eutectic layer. This eutectic decreases the gold or silver layer’s adhesion, conductivity and solder ability. Also, an electrolytic nickel under-plate forms an effective diffusion barrier between the substrate and the gold or silver layers.
Nickel plating
Additionally, electrolytic nickel plating provides a firm, structural base for subsequent gold or silver plating. Promoting wear resistance and helps provide an increased barrier to corrosion. Furthermore, certain electrolytic nickels, such as sulfamate nickel, provide good elasticity and can be used for spring contacts or crimp applications. Finally, electrolytic nickel has a high melting point of over 2000°F, making it a good underplate selection for high-temperature applications.
● Electroless nickel: Electroless nickel plating provides many of the benefits of electrolytic nickel. And include diffusion barrier, structural base and improved corrosion resistance. However, electroless nickel has the added benefit of being extraordinarily uniform. And, as such, can be plated to high thicknesses without negatively impacting the dimensional tolerances.
Electroless nickel also has improved lubricity and hardness over traditional electrolytic nickel, and high phosphorous electroless nickel is one of the few non-magnetic nickels. However, electroless nickel has a significantly suppressed melting point of 1500°F, so it should not be used in highly high-temperature applications. Finally, electroless nickel does not have as high of ductility as electrolytic nickels such as sulfamate nickel. And, as such, is not recommended for crimp applications.
What Are the Differences?
Gold and silver are the two most frequently used precious metals for connectors and contacts in various sectors. Each has advantages but disadvantages and differences between these two popular finishes. Here are a few significant differences between gold and silver electroplating. Gold VS silver plated
Gold Plating Disadvantage
Increasing gold prices can significantly affect the manufacture of gold-plated components. And especially for applications which use heavy gold deposits. Even though no other material can match the properties of gold, silver has many similar properties at a significantly reduced price. Therefore, silver can be plated more heavily and at a lower cost with a deposit that yields many similar properties. However, the formation of sulfide compounds or silver tarnish is one of the limiting factors for silver in applications susceptible to increases in contact resistance.
Silver Plating Disadvantage
Silver does not form oxides or compounds with oxygen under normal conditions. And Silver plating does form various sulphur compounds, such as silver sulfide. Although silver sulfide compounds are relatively conductive, they increase the contact resistance of the silver plating over that of pure silver alone. As a result, silver tarnish is effectively wiped from the surface within the sliding contact zone in many switching applications. However, in static applications, silver sulfide or tarnish can increase the contact resistance enough to change the signal path for very low-voltage applications.
There are various anti-tarnish inhibits such as Enthone’s Evabrite products or Technic’s Tarniban products. However, these anti-tarnish compounds add an organic or metallic film on the surface. Altering the properties of the silver electrode-posit away from that of pure silver. Gold VS silver plated
In contrast to silver, gold does not form sulfide compounds or tarnish under any normal condition. And makes gold a more viable option for lower voltage signal transmission applications. In addition, critical applications such as life-safety sensors or applications for autonomous vehicles require extremely reliable real-time signal transmission. That only gold plating can provide.
Conductivity
Silver is more conductive electrodeposit than gold. However, gold’s ability to not form resistive compounds makes it ideal for milli-amp data applications. And a good choice for low-voltage applications and corrosive conditions. On the other hand, silver’s superior heat and electrical conductivity make it the preferred material for high voltage and high current power transmission applications.
Connectors
While gold possesses several qualities that make it suitable for electronic components, several vital attributes must be considered when specifying gold plating for a connector or contact application. Here are a few key factors to consider when selecting gold plating services for a new application:
Plating Thickness
When specifying gold plating, it is vital to call out sufficient gold thickness to ensure proper function without calling for excess gold. Generally, available gold begins at approximately 0.25 microns or 0.00001 inches. And increases to as high as 2.5 microns or 0.0001 inches per side. The use of duplex gold or two layers of soft followed by hard gold can provide a more effective barrier deposit of gold per mil thickness than with a single layer. Gold VS silver plated
Specify an Underplate
As noted above, gold plating is commonly proceeded by an underplate of copper, copper, and nickel. The underplate selection and thickness are just as important as the final gold thickness to ensure a deposit that provides sufficient durability, corrosion resistance, flexibility and solderability. Copper plating helps promote adhesion and offers improved corrosion resistance and conductivity. And in contrast, a nickel under-plate provides an excellent diffusion barrier to prevent solid-state diffusion of copper or alloying elements such as zinc from forming a eutectic between the gold and the substrate.
Gold Electroplating
As-plated 99.9% minimum-plated gold is a soft deposit with a maximum hardness of 90 Knoop 25. This deposit is best suited for static, low-pressure contacts (50-gram load or less). Or applications that will be wire bonded or soldered. By alloying a small amount of nickel or cobalt with the gold, the hardness can be increased to as high as 200 Knoop 25, providing much-improved wear properties. These hard-gold deposits are recommended for higher contact pressure applications (more significant than 50-gram loads) or applications with sliding wear, such as female/male contact pins.
The Bottom-line
Selecting the appropriate plating for connectors and contacts is crucial to manufacturing a reliable product. And the type of electrode used can impact the product’s quality, performance, longevity, and cost. Gold and silver are both high-quality precious metal deposits, but they have different unique benefits and drawbacks that should be considered before specifying a specific finish. Gold VS silver plated
Author: Advance plating technologies, Milwaukee, USA
Dated: 01/02/2022
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