What Is Hard Gold?
Hard gold is a type of electroplated gold that’s usually codeposited with nickel, cobalt or iron. It has high wear resistance, corrosion resistance and consistently low levels of electrical contact resistance.
It’s a popular choice for PCBs since it improves conductivity and resists oxidation, corrosion and abrasion. It’s also compatible with fabrication processes like SMT and wire bonding.
High Hardness
Hard gold is actually an electroplating alloy that’s made of both gold and other metals. This makes it hard and suitable for places requiring force friction, such as in the electronics industry where it is often used to plate the edge connector gold finger and touch surface on mobile phones. The hardness of the gold deposits allows them to withstand contact switching events and many life cycles (with the exact number of cycles dependent on the thickness of the deposit).
When non-noble elements are added to gold electroplating, the overall structure of the deposit changes, as does its color. This results in a more refined grain structure that offers better resistance to sliding wear. Typically, hard gold deposits have the smallest grain size of all the different types of gold plating available, with most deposits having a grain size between 20-30nm. This is significantly smaller than soft gold plating, which generally has a grain size of 1-2um.
However, the impurities in hard gold do make it less suitable for soldering and wire bonding. They also reduce the corrosion resistance of the gold deposit, especially at high temperatures. Hence, hard gold deposits are often plated over a barrier coat of nickel to protect it from these issues. hard gold In addition, they are primarily used on high-wear areas of PCBs that are exposed to repeated contact switching, such as the gold fingers.
High Purity
The high purity of hard gold allows it to maintain its aesthetic value for a long period of time, and it is less prone to abrasion than soft gold. It is also able to resist corrosion, especially when used in contact with acidic materials or gases such as sulfur and chlorine. This is a key factor in selecting the material for items that will be exposed to humid environments, and it can prevent electronic components from corroding and becoming permanently damaged or unusable.
A hard gold deposit is less prone to oxidation due to its higher melting point and lower vapor pressure than copper. This makes it an excellent choice for use in a variety of climatic conditions, including abrasive industrial environments. It can also be used in electrical applications, as it has better conductivity and corrosion resistance than copper or nickel.
In addition to the above benefits, hard gold has excellent wear and corrosion resistance, and its appearance is brighter than soft gold because of its refined grain structure. However, the presence of non-noble elements in hard gold deposits (such as cobalt) reduces its overall corrosion resistance and causes oxidation when subjected to soldering temperatures. In these cases, soft or ENIG gold may be preferred. In order to avoid this, a nickel underplate is added prior to hard or soft gold plating to create a diffusion barrier and prevent the formation of weakly bonded intermetallic layers between the base metal and the gold.
High Value
Hard gold plating is a surface finish that offers a more attractive and shiny look than soft gold. Because of its smaller and more precise grain structure, it can also resist sliding wear much better than soft gold can. This makes it ideal for applications like visible interconnect applications. However, it’s important to remember that other options like nickel can offer functional benefits such as better soldering and bonding than hard gold.
Since it is a pure gold coating, hard gold electroplating can be very expensive. However, Hard Gold PCB Supplier it’s still widely used due to its durability and visual appeal. This is especially true for PCB fabrication where hard gold plating can be used for high-wear areas like edge connector Gold Fingers and keypads.
Unlike soft gold, hard gold contains impurities that make it unsuitable for some electrical connections. For example, codeposited elements such as nickel and cobalt reduce gold’s corrosion resistance while accelerating the formation of oxides and other compounds. This can lead to a significant increase in contact resistance at higher temperatures.
In contrast, soft gold has fewer metal impurities, so it is more corrosion resistant and can tolerate high temperatures with no increase in contact resistance. For this reason, it is more suitable for applications such as soldering and wire bonding. In fact, ENIG (electroless nickel over gold) is more useful than hard gold in these situations.
Fashionable
Many people associate gold with high-end fashion and jewelry. It’s also an important material for electronics and PCBs. Hard gold, a surface finish that offers tough resistance to friction and other wear, is often used for the edge connectors or “gold fingers” of PCBs. It is also a popular choice for the keypads of mobile phones and tablets.
Hard gold plating has a finer and brighter appearance than soft gold plating. This is because hard gold deposits have a more refined grain structure, which also allows them to withstand higher temperatures. However, in some cases, harder gold can increase contact resistance if it’s not applied correctly. For example, if an application requires continuous sliding contact or high heat, soft gold plating (or ENIG) is better.
Gold plating methods are usually divided into three types: hard gold, soft gold and ENIG. These plating methods differ in the hardness of the gold, which can be determined by its purity. The higher the purity of gold, the softer it is. To increase the hardness of gold, other metals are added to form an alloy, such as cobalt and nickel. These are then electroplated onto copper to become the gold layer on a PCB. This method has several functional benefits such as superior solderability and bonding, but can sometimes affect the aesthetic of the item behind it.
