Gold Plating PCB
Gold plating pcb is used in several applications and has superior properties compared to silver and copper. It’s a durable surface finish that’s also easy to apply.
Nickel is plated on the copper pads of the finger connectors before hard gold is applied. The gold is usually enhanced with cobalt for boosted surface resistance. The connector edges are beveled for easier insertion into the corresponding slots.
Advantages of Gold Plating
Gold plating is a valuable finishing option for PCBs. It provides excellent protection against damage caused by heat, and it prevents fretting degradation from friction and rubbing. It is also impervious to corrosion from copper and silver, so it protects other metals on the circuit board.
In addition, the thermal conductivity of gold is second only to silver and copper. This makes it a great choice for flexible contacts and springs. Its ductility allows it to stretch when exposed to stress, which expands the contact area and improves connectivity. Its ductility and flexibility also make it easy to bend and shape, which is ideal for tight spaces.
The durability of gold on PCBs depends on the underplate used. Most of the time, a nickel underplate is necessary before hard gold plating to ensure the coating has proper adhesion. Popular underplates include bright electrolytic nickel, high purity sulfamate nickel and electroless nickel. These underplates prevent oxidation of the nickel layer and help improve solderability.
Another advantage of hard gold plating is that it can withstand the stresses of high-pressure sliding insertion and removal applications. This makes it a good choice for connections that must be able to withstand repeated insertions and removals.
Although hard gold is more expensive than other finishes, it’s worth the investment for its performance and longevity. In addition, hard gold is compatible with fabrication processes like SMT and wire bonding. Moreover, it can be reworked and reclaimed.
Underlayers
Gold is a precious metal that provides many benefits to PCBs and other electronic devices. It is ductile and durable, making it an ideal plating choice for sensitive interconnections such as the gold fingers on a printed circuit board. The gold finger is responsible for sending signals gold plating pcb from peripherals to the motherboard card and back to the device, so it must be able to endure recurrent contact cycles. Gold is also an excellent thermal conductor and does not develop insulating oxides or compounds, which makes it useful in extreme applications such as deep-hole drilling or outer space operations.
In bonding applications, a proper selection of an underplate is critical to ensure good adhesion between the gold and substrate. An unbrightened sulfamate nickel or bright medium phosphorous electroless nickel deposit is typically chosen as an underplate because it is functionally superior for bonding and soldering, especially when compared to an unbrightened hard gold plating deposit.
However, pure gold is not durable enough for recurrent sliding insertion/removal applications, so it’s often combined with harder materials such as cobalt or nickel to create an alloy called “hard” gold. This material has increased longevity and resists abrasion better than pure gold. The use of hard gold is commonly seen in avionics, military, aerospace and medical applications where the PCBs are subject to extreme wear and tear.
Solderability
While gold is hard and resistant to friction, it also has poor solderability, making it less suitable for use as a contact surface on PCBs. However, it can be used in areas subject to force and friction such as edge connectors or “gold fingers.”
Typically, nickel is plated prior to gold plating on the underlying copper pads. This is essential to promote corrosion resistance. If not done, tarnish films or copper oxide can begin to form on the gold, which will compromise its performance. Using nickel is also vital in preventing the copper from diffusing into the gold, which can lead to the formation of poorly bonded intermetallic layers.
Immersion gold is much easier to solder than pure gold because it is softer and requires less heat to melt solder. As a result, it is the preferred choice for PCBs that are going to be soldered. It can reduce the likelihood of receiving complaints from customers about the quality of the welding, and it can save time for whoever will be soldering the circuit boards. While the cost of immersion gold is Gold Plating PCB Supplier more than that of gold plating, it may be worth the extra expense for many producers. A good way to test the solderability of gold coatings is by using the Sequential Electrochemical Reduction Analysis (SERA) technique.
Environmental Resistance
Gold is an extremely durable metal that can withstand harsh environments. It is also a good electrical and thermal conductor and has high mechanical strength. It is also non-reactive, making it ideal for use with contacts and terminals that are subjected to constant wear and tear.
Gold plated PCBs are also highly resistant to corrosion. This is due to the fact that the metal can withstand a high level of moisture and humidity, and it also has excellent oxidation resistance. However, a single layer of gold is not enough to provide adequate corrosion resistance on its own. To increase its corrosion resistance, the metal should be alloyed with other materials such as nickel and cobalt. This will provide the additional strength needed to withstand constant contact with other components.
To maximize the corrosion resistance of gold plated PCBs, they should be plated over a copper subplate. This will reduce the pore density of the metal and help to prevent contaminants from entering the pores in the plating. Using this method will also increase the durability of the gold plating and reduce contact resistance.
In addition, it is recommended that the copper underplate be plated with flash gold before the hard gold plating process. This will ensure that the copper is not exposed during the soldering process. It is also important that plated holes and SMD pads are not placed too close to the gold fingers on the circuit board. A minimum of 1.0 millimeters should exist between these areas and the gold fingers.