When designing a flex PCB, one of the most important decisions is choosing the right plating technique. Two common options are PCB pattern plating and pad plating.
PCB pattern plating involves selectively plating copper onto specific areas of the board, while pad plating involves plating copper onto circular or rectangular pads that are used for mounting components.
In this article, we’ll explore the pros and cons of each technique, and help you make an informed decision on which one is best for your flex PCB design needs.
Plating Process in a Flex PCB
The plating process is a critical step in the manufacturing of flex PCBs. It involves depositing a layer of metal onto the board’s surface to create conductive pathways for electrical signals to travel.
The plating process used in flex PCB manufacturing can vary depending on the specific application requirements and design constraints.
Two common plating techniques used in flex PCBs are pattern plating and pad plating. Pattern plating selectively plates copper onto specific areas of the board, while pad plating involves plating copper onto circular or rectangular pads used for mounting components.
Regardless of the plating technique used, precise control of the plating parameters is crucial to ensure the consistent and reliable electrical performance of the final product.
Pattern Plating and Pad Plating Process
Why Do You Need Plating in your Flex PCB?
Without plating, the board would not be able to transfer electrical signals between its components, making it essentially useless.
Plating creates a layer of metal on the surface of the board that serves as the conductive pathway for these signals.
Additionally, the plating can provide other benefits such as improved mechanical strength and resistance to corrosion.
Choosing the right plating technique is therefore an important consideration in the design and manufacturing of flex PCBs, as it can impact the overall performance and reliability of the board.
Plating in your Flex PCB
4 Types of Plating in Flex PCB
Plating in flex PCBs plays an important role in depositing metal to your PCBs to make it conductive. These are the common types of plating in Flex PCBs:
Panel Plating
Panel plating is a common plating technique used in flex PCBs where a thin layer of metal is deposited over the entire surface of the panel. This provides a uniform layer of conductivity, making it a cost-effective option for simple designs with large, continuous copper areas. Panel plating is also useful for creating a shield against electromagnetic interference.
Pattern Plating
Pattern plating is a selective plating technique that involves depositing a layer of metal onto specific areas of the board. The non-copper areas are first coated with a resist, which is then selectively removed to expose the copper areas where plating is required. This technique is ideal for creating high-density interconnects and fine circuit traces that require precise control of copper thickness.
Bussed Plating
Bussed plating involves plating a series of parallel lines that run the length of the board. This technique is commonly used to create power or ground planes, as it provides a low-resistance pathway for the flow of current. Bussed plating can also be used to create differential pairs for improved signal integrity.
Pads Plating
Pads plating is a technique where circular or rectangular pads are plated with copper to create the mounting points for components. This technique is simple and cost-effective, making it a popular choice for low-cost flex PCBs. Pads plating can also be used to create vias for vertical connections between layers of the board.
Definition of PCB Pattern Plating
In this process, a patterned copper layer is deposited onto the surface of the board, creating the circuit pathways that connect the components.
The patterned layer is achieved by selectively removing unwanted copper through a photolithographic process and then depositing copper in the desired areas.
Pattern plating involves selectively depositing copper onto a patterned substrate, where the pattern corresponds to the desired copper trace on the PCB.
This method is typically used when there are a large number of traces or when the traces are closely spaced together.
Advantage
The advantages of pattern plating include the ability to create complex trace patterns with high accuracy and the ability to deposit copper onto a large area quickly and cost-effectively.
Disadvantage
The disadvantage of pattern plating is that it can be difficult to achieve a uniform copper thickness across the trace pattern, particularly if the pattern is complex.
When it is needed?
Pattern plating is commonly used in applications that require high-density circuitry, such as in advanced consumer electronics, aerospace, and medical devices. It is also used in applications where reliability is critical, such as in automotive electronics, industrial controls, and military equipment.
Pattern Plate Stack-Up
This is the image that shows the stack-up of pattern plating PCB.
Pattern Plating
Definition of PCB Pad Plating
A process used in the production of printed circuit boards (PCBs) that involves selectively plating copper onto the exposed copper pads of the board.
The copper pads are the small metal squares or circles that are used to connect the electronic components to the circuit board.
Advantage
The primary advantage of pad plating is that it can increase the reliability of the PCB by improving the conductivity of the copper pads.
This can result in the better overall performance of the electronic device and reduce the likelihood of pad lifting or pad cracking during assembly.
Disadvantage
The disadvantage of pad plating is that it can be time-consuming and expensive for PCBs with many pads or for PCBs with pads that are closely spaced together.
When it is needed?
Generally, pad plating is suitable for PCBs with a small number of pads or where the pads are widely spaced apart.
Pad Plate Stack-Up
This is the image that shows the stack-up of pad plating PCB.
Pad Plating
Why is Pad Plating the Preferred Method for Flex PCB?
Pad plating is often the preferred method for manufacturing flexible printed circuit boards (PCBs) because it offers several advantages over other plating methods, particularly for PCBs with a small number of pads or widely spaced pads.
One key advantage of pad plating is the ability to precisely control the thickness of the copper plating on each pad. This level of control is critical for ensuring that the pads have the correct electrical properties and are able to withstand the stresses of flexing and bending.
Another advantage of pad plating is that it can provide uniform copper coverage across each pad, which is important for ensuring that the PCB has a consistent and reliable electrical performance.
Pad plating is also a relatively simple and cost-effective process compared to other plating methods such as pattern plating. This is because it does not require complex patterning processes, which can be time-consuming and expensive for PCBs with many pads or closely spaced pads.
In addition, pad plating can be used to selectively plate only the areas of the PCB that require copper, which can help to reduce waste and improve the overall efficiency of the manufacturing process.
Overall, pad plating is the preferred method for manufacturing flexible PCBs because it offers precise control over the thickness and coverage of copper on each pad, is a simple and cost-effective process, and can help to reduce waste and improve manufacturing efficiency.
Things to Consider During Pad Plating Process
During the pad plating process for flexible printed circuit boards (PCBs), there are several key factors that must be considered to ensure that the resulting PCB is of high quality and meets the required specifications.
Via Size
The size of the via is an important consideration during pad plating as it can affect the ability to properly plate the via with copper. In general, smaller vias can be more difficult to plate and may require special plating techniques to ensure proper coverage.
Via Size
PTH Pads
Plated through-hole (PTH) pads are used to connect the copper traces on different layers of the PCB. During pad plating, it is important to ensure that the PTH pads are properly plated with copper to ensure good electrical conductivity between the layers.
PTH Pads
Hole Size
The size of the hole in the pad is another important consideration during pad plating. The size of the hole can affect the ability to properly plate the pad with copper and can also affect the mechanical strength of the pad.
Hole Size
Copper Type
The type of copper used for pad plating can also affect the quality of the resulting PCB. It is important to select a high-quality copper material that is suitable for use in flexible PCBs and that will provide good electrical conductivity and mechanical strength.
Copper Type
Grain Direction
The direction of the copper grain can also affect the quality of the resulting PCB. It is important to ensure that the copper plating is applied in the correct direction to ensure good mechanical strength and resistance to cracking and fatigue.
Grain Direction
IPC Standards of Flex PCBs
IPC is an organization that develops and publishes industry standards for the electronics manufacturing industry. There are several IPC standards related to flexible printed circuit boards (PCBs), including IPC-6013 and IPC-2223.
IPC-6013
This standard defines the requirements for the design and manufacture of flexible printed circuit boards. It includes specifications for materials, constructions, testing, and inspection of flexible PCBs.
IPC-6013 covers both single and double-sided flexible PCBs, as well as multi-layer flexible PCBs. This standard is widely used in the electronics industry and is an important reference for manufacturers of flexible PCBs.
IPC–2223
This standard provides guidelines for the design of flexible printed circuit boards. It covers topics such as material selection, mechanical design, electrical design, and environmental considerations.
IPC-2223 also includes guidelines for the testing and inspection of flexible PCBs. This standard is intended to help designers and manufacturers of flexible PCBs produce high-quality, reliable products that meet the needs of their customers.
Final Words
In conclusion, pad plating and pattern plating are two commonly used plating methods in the manufacturing of flexible printed circuit boards (PCBs).
Pad plating involves plating the entire surface of the PCB and then selectively removing the unwanted copper, leaving only the desired copper pads. Pattern plating involves applying a resist material to the surface of the PCB and then selectively plating the desired copper areas.
The main advantage of pad plating is that it allows for greater control over the thickness and uniformity of the copper plating, resulting in higher-quality and more reliable PCBs. It is also a more cost-effective method for manufacturing small to medium-sized production runs.
On the other hand, pattern plating is often used for larger production runs and can be a more efficient method for creating complex PCB designs with a high degree of precision. However, it can be more expensive than pad plating and may require additional processing steps to ensure the quality of the plating.
Ultimately, the choice between pad plating and pattern plating will depend on the specific requirements of the PCB design and the manufacturing process.
Manufacturers must carefully consider factors such as cost, production volume, and the desired quality and reliability of the final product when selecting a plating method for their flexible PCBs.
