Hard and Soft Gold PCBs

With geopolitical uncertainty at decade-lows, investors are flocking to hard assets. This includes gold, which has seen its prices climb after a long slump.

Hard gold, also known as deep gold or hard electrolytic gold, is an elemental gold finish that has been thickened with hardeners and plated over a barrier coat of nickel in an electrolytic process. It’s often used in high-wear areas such as edge connector Gold Fingers and keypads, but is rarely applied to solder-able areas.

Durability

Gold is known for its durability, and this has led to it being used in aerospace components, from fighter jets to commercial planes. Its high reliability and durable nature make it ideal for applications that require frequent insertion and extraction, as well as the ability to withstand strong contact forces. Its resistance to corrosion is also important, especially in humid or highly corrosive environments.

The durability of hard gold is attributed to its lack of oxide, which has insulation properties and inhibits compound formation. This makes it resistant to acid attack and oxidation, which can weaken copper contacts over time. The durability of hard gold plated contacts also depends on the thickness of the coating, with thicker deposits being capable of powering through more use cycles.

Another benefit of hard gold is its resistance to corrosion in aqueous solutions, including salt water and chlorine gas. This is a key factor in its success as an electrical conductor, especially in high-temperature applications where copper may degrade or lose its conductive ability.

The durability of hard gold also makes it an excellent option for PCBs, as it can withstand a great deal of actuation force. However, it is important to avoid excessive cleaning, as this can hard gold cause the plating to wear down over time.

Corrosion Resistance

Corrosion resistance refers to the ability of a metal or a PCB to withstand oxidation and other forms of degradation. It’s important to choose a PCB manufacturer that has a proven track record of providing quality products with good oxidation and corrosion resistance. These manufacturers also have the ability to handle complex fabrication processes like SMT and wire bonding.

Hard gold has a higher oxidation resistance than copper or nickel, making it more resistant to corrosive environments. This makes it ideal for a wide range of applications, including medical equipment. It is also an excellent choice for high-speed electronics because it offers superior conductivity. Hard gold is an affordable alternative to traditional copper or metal printed circuit boards and provides the same high level of durability.

When selecting a hard gold plating manufacturer, it’s important to consider the experience and expertise of their staff. Ideally, the company should provide technical support for all PCB assembly and usage needs. This includes advice on component selection, surface finish, solder mask stack-up builds and more. It should also adhere to international standards and RoHS compliances.

Choosing a PCB manufacturer with hard gold plating is crucial for your project’s success. A reputable manufacturer will help you find the right solution for your specific needs, based on your application and environmental conditions. They’ll also work collaboratively with you to ensure that your product is delivered on time.

Solderability

Due to the presence of non-noble metals like nickel, cobalt and iron in hard gold plating, this finish can be problematic for soldering. These metals are easily oxidized at high soldering temperatures and make the bonding process difficult. This makes hard gold plating unsuitable for sensitive applications such as ultrasonic wire bonding and thermostatic bonding. In these cases, soft gold plating or ENIG should be used instead.

However, hard electrolytic gold has a dazzling appearance and is commonly applied to the fingers on edge connectors and keypads on PCBs. In order to achieve this, the gold is plated over a barrier layer of nickel. This nickel obstructs the pores of the gold deposit and reduces the possibility of pinhole corrosion.

Additionally, hard gold is preferable for projects that require regular sliding wear or on/off switching events. This is because thicker gold deposits can withstand many cycles of actuation. This Hard Gold PCB Supplier durability and longevity also make hard gold a great choice for aerospace components that must be exposed to harsh environments.

Unlike copper, hard gold does not oxidize in acidic conditions. This is important for PCBs that are exposed to corrosive chemicals or gases. The gold coating protects the copper or nickel underneath from these harsh environments and enables a solid contact point. This is especially useful for electronic devices that are frequently used in a humid environment.

Cost

A hard gold PCB will cost more than a traditional one, but it is often worth the investment. It is the ideal choice for high-speed applications and those with a requirement for high durability and contact resistance. It also works well in corrosive environments and resists abrasion. It is important to consider the end-use of the product before selecting a hard or soft gold plating option.

For instance, a PCB with soft gold will be susceptible to scratches and may need to be reworked more frequently. On the other hand, a PCB with hard gold will last longer and be more durable.

PCB hard gold plating starts with copper etching to leave only the required areas bare. Then a nickel underlayer is electroplated with a minimum of 50 micro-inch thickness. This underlayer acts as a diffusion barrier, which prevents corrosion, creep and pore corrosion. It also improves soldering and bonding.

The non-noble elements in hard gold help it retain a fine grain structure and increase its durability. These metals inhibit crystal growth, which makes it difficult for the grains to move during sliding wear. This is what gives hard gold its excellent durability and low coefficient of friction.

PCB hard gold surface finish is generally applied to edge connector fingers and keypads. Its reworkability and long lifespan make it a good choice for large-volume productions. Its long lifespan also makes it more economical than other types of PCBs.