Copper Electroplating: How It Works and Its Common Applications

Posted on : By


Home / Blog / Article
Copper Electroplating: How It Works and Its Common Applications

Soft, highly malleable, conductive, corrosion-resistant, and best of all economical, copper is simply a perfect choice for a variety of applications. While copper is great, the material is not suitable for applications where you need strength along with what copper brings to the table. For such cases, copper electroplating can be an ideal solution. The outer layer will deliver the same properties that you might need for the application while the core can give you the strength or any other mechanical properties you might need.

So, how to get started with electroplating copper, and what are the intricate requirements of the process. This article will take a detailed look at copper plating and discuss the common applications of the process.

Copper Electroplating: A Brief Overview

Copper electroplating is a simple electrochemical process that results in a thin copper coating on any conductive surface with the help of an electrolyte bath. The electrolysis process is quite simple. The cathode and anode (positive and negative terminal) attract the opposite charges from the electrolyte and the anode as well.

typical-copper-electroplating

In the process, a pure copper wire acts as an anode while the product or part that needs electroplating acts as the cathode. The electrolyte solution completes the circuit and the electricity flow allows copper particles to go and deposit on the surface of the cathode.

This seemingly simple setup has tremendous benefits for multiple industries because it gives you the best of both worlds. You get the corrosion resistance, conductivity, and other benefits of copper without any compromise on the overall strength.

Major Copper Electroplating Techniques

Fundamentally speaking, copper layers need a simple electrolysis setup with the right combination of anode and cathode along with the electrolyte. However, different project requirements may need you to maintain control of the plating rate, or the surface to which it adheres. For that, you’ll need multiple additives and chemicals that can act as levelers, accelerators, or suppressors to ensure that you get the result you need.

Here are the 4 main techniques that industry experts use for copper plating.

Dual Damascene Plating

The dual damascene technique is reserved for applications where you need to prioritize certain features of the part for electroplating. Generally, it’s used for electroplating smaller components that are in nanometers and in semiconductors that need varying conductivity and resistances for certain important applications.  

dual damascene technique

In the dual damascene technique, the suppressors, accelerants, and levelers work together to ensure bottom-up plating. In the above illustration, the suppressants stay on the side walls to reduce the copper deposition rate while the levelers remain around the top to reduce the accumulation of copper ions on the top surface.

Through-Silicon Via Plating

The silicon via plating technique is similar to the aforementioned dual damascene method but is slower and reserved for larger features that are in micrometers instead of nanometers.

TSV plating

As the illustration shows, both the suppressors and levelers work together to reduce the deposition rate on the sides and the accelerators allow bottom-up filling. The process is time-consuming and takes about an hour to process. That’s why the concentration of accelerants on the bottom is low.     

Copper Pillar Plating

The copper pillar plating process is both time-consuming and complicated because of its requirements. In this case, you need to ensure the part’s coplanarity and deliver high plating rates without making any trade-off on the uniformity.

copper pillar plating process

An excellent plating process delivers you the exact thickness of the layer on the surface and you need to add a setup where the part continues to spin for that. The rotation and the incoming flow create a uniform current density and deliver your required results with consistency.     

The following table gives a quick overview of the 3 main aforementioned electroplating techniques.

ParameterDual Damascene PlatingThrough-silicon Via PlatingCopper Pillar Plating
Bottom-Up Fill TimeSecondsAround 1 hour10 minutes
Accelerator concentrationHighMedium or lowMedium or low
SuppressorsStrong polarizing agentModerate polarizing agentModerate polarizing agent
Levelers Top of the trenchThe sidewall of the viaIn the via

Redistribution Layer Plating

This process is exclusive to advanced integrated circuits with fan-in and fan-out wafers. The precision of RDL plating is up to 2 µm and offers excellent uniformity and reliability.

When it comes to RDL applications, you can opt for either the conventional way (2D) or the 3D method. 2D is simple as the processing requirements and intricacies of the circuit are easier to handle. However, the 3D RDL applications require precision and the best process control which is dependent on the following 4 conditions.

●Wafer rotation for uniformity

●Fluid profile for the optimum electron flow

●The tuning and precision of the electrical field

●The additives

Apart from that, the process is good for additional features that integrated circuits come up with for auxiliary connections and easier access to new input and output pads.  They provide excellent uniformity and enhanced purity. Moreover, the technique is also cost-effective, which makes it a perfect choice.  

The Benefits of Copper Electroplating

Here are 5 major benefits of using copper for the electrolysis process.

copper electroplating flexibility

Flexibility and Durability

One of the core properties of copper is its malleability. Copper material works perfectly on parts that require further post-processing. You can bend, twist, or perform various other mechanical processes on a copper-plated material and the surface layer won’t come off. This means that this process will not hinder your operations and will increase the lifespan of the part.

Excellent Corrosion Protection

Copper is chemically stable and resists corrosion in most circumstances. This quality makes it a perfect choice for electroplating as the layer of copper can protect the base material that might be more prone to corrosion. In the harshest conditions, even copper corrodes, but it’s a viable option for many regular applications.  

Great Conductivity

Copper is an excellent conductor of both heat and electricity. That is one of its defining properties and that’s why its applications are predominantly around the electronics industry. Even if the core metal is not a great conductor, the copper layer can give it that quality and fulfill the requirements of your application.

Excellent Anti-Bacterial Qualities

Another common application of copper applications is in a lab setting. The metal has the natural ability to resist interaction with bacteria or any other micro-organisms. This means that you won’t have to go through the elaborate process of disinfecting surfaces or containers with a copper lining.

Cost-Effectiveness

Despite all these excellent and sought-after qualities, copper remains among the cheapest conductive metals on the planet. Moreover, the process with a copper sulfate solution is also simple, which further increases the viability of this process.

Different Types of Copper Electroplating Baths

Electroplating depends on many factors including the right voltage, the right metal combinations, and the right electrolyte solution. Naturally, whatever electrolyte you use must contain copper ions. However, the way they are chemically bonded has a lot to do with the capabilities of the process. Generally, you have the option to choose between either alkaline, acidic, or sometimes an electroless plating bath.

Here are the main types of copper electroplating solutions that the industry uses today.

1 – Typical Alkaline Copper Baths

Generally, alkaline solutions are for applications where you prefer functionality over finesse. Copper electroplating with alkaline baths is very hard to control and may even come with some health hazards. There are 3 main types of alkaline baths that you can use.

copper bath

Alkaline Cyanide Solutions

Alkaline solutions of copper and cyanide are famous for providing an excellent electroplating coat with no functional downside. Generally, copper cyanide solutions allow the coating to adhere well and remain soft, which makes it easier to buff and maintain.

There are, however, a lot of drawbacks to using cyanide solutions as well. Some of the most important ones are:

Alkaline solutions of copper and cyanide are famous for providing an excellent electroplating coat with no functional downside. Generally, copper cyanide solutions allow the coating to adhere well and remain soft, which makes it easier to buff and maintain.

In most cases, metals that you use today for various applications are susceptible to damage if they are exposed to liquids, especially acids. Alkaline solutions are different. Moreover, the cyanide also plays an active role in protecting the base metal until the process is complete.

While using a cyanide solution gives you the quickest and most efficient electroplating results. However, the results won’t be aesthetic. Generally, this process is reserved for very active metals where you put a thin layer immediately to stop the interaction with the environment and then proceed with further coatings with a different approach. There are, however, a lot of drawbacks to using cyanide solutions as well. Some of the most important ones are:

●Difficult to control

●Extremely dangerous

●Requires special handling

●Not suitable for high current density

Alkaline, Non-Cyanide Solutions

Cyanide is hypertoxic! This means that using it comes with a plethora of risks for the workers and the environment alike. Moreover, a lot of government agencies throughout the world don’t allow the use of cyanide in any form because of its toxicity.

Despite its drawbacks, you can’t deny the advantages of cyanide-based copper solutions. Their most important capability is to protect the base metal and give it basic protection for further processing. It is impossible to replicate with acidic solutions.

In such cases, the best option is to opt for a non-cyanide solution that fares much better in safety because of the absence of cyanide.

Non cyanide solutions come with a plethora of advantages because of their high current efficiency. The solution gives a better appearance, stability, and strong leveling power. Apart from that, non-cyanide alkaline solutions have a lower cost, and treating its overall waste is comparatively easier.

There is, however, a drawback as well. Non-cyanide solutions are not as effective and efficient as the cyanide ones but the apparent convenience to handle and the less hazardous nature of non-cyanide solutions is an excellent trade-off.

Pyrophosphate Copper (Mildly Alkaline)

This solution is most important in the applications where you need ductility and throwing power. Pyrophosphate copper is mildly alkaline and is free from any toxic materials. Moreover, it is also less corrosive. Generally, acidic solutions come with the ability to damage the base material. strong alkaline solutions have their own problems and are quite hard to control. However, this mildly alkaline method allows you to maximize the benefits of non-corrosiveness without compromising on the current density and overall control.

The most important application of electroplating copper through this solution is printed-circuit-boards. It’s also used in other applications like general plating and electroforming. The process is also suitable for materials like plastics, which generally don’t conduct electricity and are hence unsuitable for electroplating.

However, pyrophosphate is a pollutant and the law of many regions dictates the need for processing before discarding it. Thereby increasing the costs and other resources for the process.   

2 – Typical Acid Copper Baths

Acid solutions are simpler, more effective, and more precise alternatives to their alkaline counterparts. They are a better choice from every perspective as they are more cost-effective, more versatile, and extremely easy to control. Moreover, acid baths can even tolerate high current densities, resulting in a thicker copper layer that is a basic requirement for many applications where durability is important.

Two kinds of copper surface electroplating solutions are common in the industry. you’ll have to opt for the combination of copper ions with either sulfate or fluoborate ions.

copper sulfate bath

Copper Sulfate Baths

A saturated solution of copper sulfate is a common electrolyte that the industry uses for the electroplating process. Any electrolysis process requires an electrolyte to complete the circuit and using a saturated copper sulfate bath serves two purposes. In addition to facilitating the transfer of electrons (electrical flow), the sulfate solution also acts as a source of copper for electroplating.

This means that you don’t have to use a copper anode as the solution itself can provide the copper you need. Using copper sulfate baths is most suited for applications where you need direct application of copper without frequently changing the anode.

Another important characteristic to note is the overall cost-effectiveness of the solution. Copper sulfate is a common chemical and is very easy to procure. Thereby making it a suitable option for small setups. The byproducts of the entire process are also harmless. You’ll get a deposit of sulfur at the bottom of the tank after the process which is easy to extract and handle.  

There is, however, a limitation to using copper sulfate baths as well. Firstly, the sulfate solution needs to be completely saturated for the best results. Similarly, as the process proceeds, the copper solution loses its conductivity due to the loss of copper ions. To counter that, it’s common to add sulfuric acid in the solution that maintains the conductivity and acts as a charge carrier for the process.

Copper Fluoborate Baths

Copper fluoborate baths are another alternative that is not that common in the industry. The fundamental principles of electrolysis remain the same in this case as the copper in the solution eliminates the need of replacing anodes. The solution acts as the source of copper and works in the same way as copper sulfate.

There are, however, many major differences that set copper fluoborate baths apart. First, fluoborate solutions are extremely soluble, which means that their saturation point comes much later and the same volume of solution can hold a greater number of copper ions. This is excellent quality for high-speed processes or applications where you need to coat large parts. The greater ion concentration saves time and keeps the process compact. Furthermore, the greater ion concentration also increases the conductivity of the solution and provides a better current density.

However, there are some limitations as well. Copper fluoborate solutions are extremely expensive when compared to their sulfate alternative. That’s why their use is not that widespread. Moreover, the solution also doesn’t offer the same throwing power and is much harder to treat. Fluoborate ions are extremely corrosive and hazardous, so handling them further increases the overall costs.

3 – Electroless Copper Plating Bath

Electroless baths are slightly different. Unlike the above examples, these baths are purely chemical and don’t need any electricity to pass through for application. This is a perfect choice for applications where you need a uniform layer or when you are dealing with complex geometries. Furthermore, electroless baths can also deal with non-conductive surfaces that don’t complete the circuit in a traditional electrolysis setting.

The 4 Main Industrial Applications of Copper Electroplating

Copper electroplating has numerous applications across different industrial sectors because of its chemical, mechanical, and electrical properties. Here are the 4 main industrial areas where copper plays an integral role.

1 – Electrical Wiring

The majority of the copper processed today is used for electrical wiring globally. In fact, it accounts for around 60% of copper usage globally. The excellent conductivity along with the natural malleability of copper give electrical wires the flexibility and transmission capabilities that they need for optimal operations.

Copper-electrical-wires.jpg

copper wiring in motor

2 – Electronics

Just like wiring, electronic components like circuit boards and relays also use copper because it’s a viable material choice that delivers the best conduction at the most competitive price.

Apart from electrical conductivity, copper’s capability of heat conduction is quite high as well. Modern electronic components are compact and require special considerations to prevent overheating. Copper plating enhances the thermal conductivity of the material and can act as a heat sink or heat dissipation to keep the electronics under operating temperatures.

copper electronic component

3 – Automotive

The automobile market has always used copper for its wiring, internal components, and other electronic features. However, the demand for copper in the automobile sector is bound to increase because of the current market trends.

Ask anyone in the automobile sector about the current industry trends. You’ll find one answer, electric vehicles.

Copper is increasingly becoming more and more relevant in the automobile sector as the motors are replacing internal combustion engines. Furthermore, the solenoids, internal winding, and multiple other components inside any electric motor and its auxiliary components need a copper layer to ensure durability and perfect performance.

4 – Renewable Energy

Copper stands as the second most effective metal that conducts electricity. The first one is silver, but it’s really expensive and not viable for large-scale applications. For renewable energy, copper electroplating plays an integral role because you need minimal transmission losses and inefficiencies.

Consider solar panels to understand it better. Even the most modern solar panels are around 23% percent efficient. Moreover, add in the transmission losses due to internal resistance and that number can go down. Copper offers the least conductivity and is the most ideal choice as it doesn’t affect the overall costs of your project.

Get Aesthetic Metal Parts With RapidDirect’s Finishing Services

Outsourcing manufacturing services and other related processes (like electroplating) are perfect solutions for small and medium businesses. This allows you to get the required results without the initial capital investment and gain access to a team with diverse experience in the field.

RapidDirect offers a wide range of metal manufacturing capabilities (CNC machining, sheet metal fabrication, die casting, and more) and surface finishes to ensure that your parts satisfy performance and cosmetic requirements.

Our focus and uncompromising attitude toward quality ensure consistent and accurate results in the shortest lead time. Furthermore, we at RapidDirect set ourselves apart with our competitive prices and world-class services that are only a click away.

Upload your files and get started with RapidDirect today!

Conclusion

Copper electroplating is an ideal process because of its versatility and effectiveness. It allows you to make use of all the advantages of copper while ensuring excellent mechanical properties. Additionally, the layer of copper also acts as a protective coating that can save the base metal from environmental elements and corrosion.

The actual electroplating process varies according to your applications and requirements. However, the fundamentals remain the same. The basic process is electrolysis and how you do it and other additional factors like the solution you use or the technique controls the results and suitability of the applications. Therefore, you should be careful while selecting the process. RapidDirect is your best bet!

So, what are you waiting for? Upload your project requirements, specify the technical details, and get started with RapidDirect’s ideal copper electroplating and other manufacturing services.

Try RapidDirect now,
for free

All information and uploads are secure and confidential.