The surface finish on a printed circuit board plays a significant role in its performance and functioning. There is a wide array of surface finishes for circuit boards. However, you need to know the one that suits your printed circuit board. The application requirements of your PCB will determine the type of surface finish to use. Examples of PCB surface finish options include Electroless Nickel Immersion Gold, Immersion silver, Immersion tin, HASL, and more.
Generally, gold is a good surface finish material for coating circuit boards. Flash gold is becoming more popular among PCB manufacturers because of the properties and benefits it offers. Let’s discuss more on flash gold PCB and its benefits.
What is Flash Gold PCB?
Flash gold is a thin gold plating used over electrolytic nickel. This gold is electrolytic and the panel is linked to a current and plating rectifier. The thickness of gold depends on the current density and time spent. If flash gold spends too much time in the bath, it will transform into a flash gold in the long run.
Flash gold is very easy to produce. This type of gold means rapid gold plating. The flash gold is a process of hard gold plating. Large current is used in this process and the solution which has more gold content produces a dense gold plating layer on the nickel layer. This helps in enhancing subsequent electroplating of gold-cobalt alloy. According to some expert, it is possible to make a “gold-plated” circuit board, while PCB manufacturing time is shorter and the cost is less, rather than selling such “flash gold” PCBs in the market.
Flash gold PCB is cheaper than hard gold PCB since “flash gold” doesn’t involve the subsequent electroplating gold process. However, the gold layer of flash gold is very thin. The thin layer of flash gold won’t make it cover all the nickel layer. As a result, this can lead to oxidation after the printed circuit board have been stored for a long time. This will have an effect on solderability in the long run.
For many years, PCB manufacturers have been plating flash gold on PCBs. Immersion is the method of applying flash gold on PCBs. A flash gold PCB is a circuit board in which flash gold is applied on the surface of the board.
Difference Between ENIG and Flash Gold PCB?
Flash gold PCB and ENIG PCB have gained popularity in the PCB space. PCB manufacturers are familiar with this surface finish. IC pins are becoming more dense due to the increasing demands of IC. HASL as a surface finish option finds it difficult to blow the fine pad. Therefore, this makes it a difficult option for SMT PCB assembly. Also, HASL PCB don’t have a long shelf life. While all these are problems that raise concerns among PCB manufacturers, Flash gold PCB offers solutions to these problems.
A flash gold PCB is much better due to the fact that the flatness of the pad is linked to the solder paste printing’ quality. Also, the pad flatness can affect the quality of subsequent reflow welding. The flash gold is widely integrated in small surface mounting and high density process.
In the prototyping stage, there are factors that affect the flash gold PCB process. These factors include component procurement. It usually takes more time to use these boards.
A flash gold PCB has a longer shelf life when compared to HASL PCB. Also, flash gold PCB design cost is similar to the lead tin alloy plate. One of the best surface finish which can help you achieve a thicker gold is the Electroless Nickel Immersion Gold (ENIG). The method of depositing the Electroless nickel gold makes it a perfect option.
The flash gold process involves dissolving nickel and gold in a chemical solution. In this case, the PCB is dipped in the electroplating cylinder and a current connects the board to produce nickel gold plating on the PCB surface.
Due to the properties of Electroless gold, it is widely integrated in the manufacturing of electronic products.
Flash Gold PCB Vs ENIG PCB in PCB Design
Flash gold PCB has a different crystal structure. Also, flash gold is known for its thinness. ENIG is thicker than flash gold plating. ENIG is golden yellow and appears to be brighter than flash gold.
Flash gold PCB forms a different crystal structure compared to ENIG. Also, it is much more difficult to weld flash gold than ENIG. EMIG doesn’t lead to poor welding since it is easier to weld. PCB manufacturers find it much easier to control the stress of ENIG than that of flash gold. Flash gold is harder than ENIG and as such can experience wear over time.
Furthermore, Flash gold PCB can produce oxidation over time. However, ENIG’s crystal structure is more compact than flash gold and as such doesn’t produce oxidation easily.
Flash gold PCB is more vulnerable to short circuit. This is because the wiring becomes denser and the line spacing and width would reach about 4 mil. On the other hand, ENIG PCB comprises nickel gold and as such won’t cause any short circuit.
There is a stronger bonding between the copper layer and solder mask layer of ENIG PCB. This is because EMIG PCB features only nickel gold. This is different for a flash gold PCB as the bond between the copper and solder mask tends to be weak.
Features to Consider When Choosing a Gold Plating Method for Your PCB
There are several features that determine the choice of your gold plating method. Below are four important aspects you need to put into consideration:
Solderability
Since flash gold PCB comprises some non-precious metal elements, it makes it solderability more difficult. Therefore, ENIG is a better option for sensitive joints like thermostatic bonding or wire bonding.
Appearance
Flash gold is a good choice for plating your PCB. This is because of its appearance. It is advisable to make use of flash gold plating in applications where beautiful gold contacts are required.
Corrosion resistance
When choosing a gold plating method for your PCB, you need to consider the ability of the gold plating to resist corrosion. ENIG plating is known to have a high corrosion resistance and as such it is a better option.
Contact resistance
Hard gold plating has higher contact resistance. Therefore, soft gold plating like ENIG is a much better option for high-temperature applications. This is because of the increased formation of compounds like oxides.
Wear resistance
When it comes to wear resistance, flash gold is a good option. This gold plating method is great for applications where repeated sliding wear is needed.
Benefits of Flash Gold in PCBs
Flash gold is usually applied on the surface of a printed circuit board. This thin layer of gold is usually applied using heat. Although flash gold PCB isn’t as durable as other types of PCB plating like ENIG, it offers some benefits. Here are some main benefits of flash gold PCB plating
Versatility: Flash gold is ideal for use in different types of PCB. It is ideal for single layer, multilayer, and double layer boards. Also, this type of is a cheaper option and as such, it is highly preferable.
Corrosion resistance
Generally, gold is a corrosion resistance material. Flash gold is a good gold plating option for PCBs because this gold doesn’t corrode or tarnish over time. Therefore, it is an efficient and durable gold plating method.
Aesthetic appearance
One of the benefits of flash gold PCB is its aesthetic appearance. Flash gold offers aesthetic appeal and as such it is widely used in circuit boards.
Cost-effective
Another advantage of using flash gold for PCB plating is its cost-effectiveness. Applying flash gold on the surface of your printed circuit board a great way to cut cost. Flash gold is a recommended gold plating method for PCBs. It is a way PCB manufacturers can achieve that solid gold feel without spending too much
Customization
Flash gold PCB plating allows customization. This means you can customize this gold based on certain features. You can customize the color and thickness of this gold to suit your own needs and design.
Conclusion
Flash gold PCB is very easy to produce. This type of gold plating methods is rapid. The flash gold is a process of hard gold plating. Large current is used in this process and the solution which has more gold content produces a dense gold plating layer on the nickel layer. This helps in enhancing subsequent electroplating of gold-cobalt alloy. According to some expert, it is possible to make a “gold-plated” circuit board, while PCB manufacturing time is shorter and the cost is less, rather than selling such “flash gold” PCBs in the market.
Integrating flash gold in circuit boards is a cost-effective plating method. Flash gold offers a lot of benefits. Also, it is a cost-effective gold plating option that features other benefits. Electroless gold has non-oxidation properties and has resistances to wear. Its high hardness also makes it an ideal option.
