PCB Types and Layer Counts: What You Need to Consider
There are many options for printed circuit boards (PCBs), including various materials and different layer counts. These boards allow you to maximize certain product strategies.
If you produce high volumes, cost reduction is important for your Return on Investment (ROI). Your considerations may be different if your product appeals to people who need less space.
The Ignys Team has a lot of experience in electronic design services. Learn more about PCB types and their pros and cons.
Types of PCB and When to Use Them
These are some of the most common PCB types, along with tips for when to use them. Each product is different in its way. Keep that in mind when you’re having trouble deciding on a product, set up a discovery phone call with our engineering team.
We’ll start with the number of layers. Then we’ll look at rigid and flexible PCBs.
Pros and cons
Single-sided PCB design
These circuit boards are simple and have copper on one side.
The advantages of single-sided PCBs
- It is easy to design
- Their simple construction makes them very cost-effective when mass-produced.
- These are easier to test in the production stage.
Cons single-sided PCBs
- A limited number of components can be used.
- Complexity may not be appropriate for certain products and devices.
An example of when to use a single-sided PCB
Product cost reduction is important if you sell large volumes. Each penny or cent added to the unit cost can make a significant difference in your total volume. This affects profit margins for every product.
Single-sided PCBs are a great way to quickly design a simple and appealing product for a large market.
Copper is found on both sides of this board so that tracking can be done from both sides. Vias, which are small holes drilled with copper and used to connect the top and bottom of a board, can achieve this.
The advantages of double-sided PCBs
- The space and surface area is nearly double that of a single-layer board the same size.
- The design can be made more complex by using.
- Still very cost-effective to produce.
- A single layer board is more expensive than a one-layer board. A single layer board is better if you only use a small number of components on one side.
- Production and testing are more complicated than simple layer boards.
- The complexity is less than multi-layer boards.
- Due to the limited power and ground plane options and routing restrictions, EMC (electromagnetic compatible) can be more challenging for board layers.
An example of when to use a double-sided PCB
If you have a large market and need to make a device of medium complexity, space is not an issue. You can reduce costs, save space and add extra features. Double-sided PCBs are the most affordable. They have components on one side and can be used for complex interconnections. This reduces the cost of component populations.
Multi-layer board design
Multi-layer boards can have layer counts of up to three. Because of the manufacturing process, PCB layers count are usually an even number, with 4,6,8,10 and 12,14,16, respectively. Electronic engineers can design more complicated products with higher layer counts.
Multi-layer boards allow you to use a variety of radio-frequency design techniques, as well as robust power distribution and ground returns. Multi-layer printed circuit boards are required for modern, dense device packages like Ball Grid Arrays (BGA). This is to have access to all the signals.
The pros and cons of multi-layer board design
- Controlling impedance is possible. Manufacturers can make a PCB stack-up that meets the specifications of the engineer.
- It is possible to create a high-speed layout. This is because the impedance can’t be controlled as well.
- A multi-layer PCB with a well-designed design will have a lower EMI signature than a similar design on a 2-layer board. Any risk reduction can help to save money.
- A smaller printed circuit board can be used.
- Fun fact
Similar: Ignys PCB Layout Services
Cons for multi-layer board design
- Layers add up, and costs rise. Therefore, extra layers should only be used when necessary. Additions, manufacturing costs, and development challenges can all add up to a lot of money. This should be included in your product’s pricing strategy and ROI plan.
- Extra design complexity – Complex electronics design requires a lot of testing and can lead to many problems.
- Access to the signals for testing – Accessing all signals on the board can be required to debug prototype bring-up testing. The signals may not be accessible on early prototypes due to their high layer count.
Similar Topic: The importance and use of test points
An example of multi-layer boards
These are ideal for complex projects that require a high degree of engineering and many features. These can often be used to produce a product with a premium price bracket or high sales volume, which means that development costs can easily be recouped.
Rigid PCB Designs
This is the traditional PCB type that most people think of when they think about a PCB.
Usually, the conducting copper layers are sandwiched between FR4 cores. FR4 is a fibreglass resin material and is the most popular PCB substrate. However, there are many other materials. Rigid PCBs tend to be less expensive than flexible or flex-rigid boards. A rigid PCB is a good choice if space is not an issue, but the cost is.
FR1 materials, FR2 and FR3, may be used in super-low cost designs. These materials have different properties in terms of heat resistance, electrical strength and thermal properties. These can cause quality control issues and manufacturing problems. They should only be used in a few cases.
Higher cost materials are used to make very high-speed electronics at a lower price point. They have superior performance. FR4 can cause signal degradation at around 2-1GHz and is not suitable for use beyond 20Ghz. These boards can be made from ceramic or PTFE.
Applications that generate substantial heat, such as LED lighting, often use aluminium PCBs, such as heatsinking.
These are made with a flexible substrate (often polyimide) rather than a fibreglass substrate.
The advantages of flexible PCB designs
- Allows the computer to conform better in a complex product housing
- A curved space can be used in a product. It can also be used alongside rigid PCBs
- Less likely to be damaged if the device is dropped
- More resistant to high vibrations and high heat environments
- Less affected thermal cycling
- Flexible PCBs with multiple layers are available. You don’t need to rely solely on a basic design
- They are lighter than rigid PCBs.
The Cons of Flexible PCB Designs
- These are more costly and harder to make
- More design guidelines are needed when creating a flexible PCB
Example of when to use a flexible PPB
There are two uses for a flexible board design.
1) A small enclosure is key to your product’s appeal. Making less space available. Your electronic device should not be too heavy to appeal to your target audience.
2) The product must be able to withstand bending over its lifetime. Flexible circuitry can be used in a smartwatch or wearable device. It can be used to both prevent damage and make the device functional for its intended purpose.
Rigid-Flex PCB designs
These PCBs combine the best of both worlds. This comes with a price! This hybrid option lets you combine the best of both rigid and flexible PCBs.
The Pros of Rigid-Flex PCB Design
- Flexible PCBs can be used to connect multiple rigid boards. Multi-board designs can be made as one unit.
- Instead of using traditional connectors to connect rigid boards, you can use a rigid-flex board. Connectors can be easily damaged by vibration, which eliminates the risk of them coming apart.
- This is a great option for small spaces.
Cons Of Rigid-Flex PB design
- More manufacturing steps are needed for both rigid and flexible boards. This makes it the most expensive option.
- There are many options for material choices, both for the flexible and rigid portions of the board. You should work closely with your manufacturer, especially if you require controlled impedances.
Next, what to read
Design for Availability – Avoiding Chip Shortages and Design
What is more important: Investment or cost? – Product development investment
Engineering Blog Authorship
This blog was created with the help of Toby Lane, and the direct input of the Ignys engineering group.
One of our Ignys engineers, Toby Lane, joined us in summer 2021 after completing his master’s degree from Sheffield. Toby completed a year-long placement with product development and design consultancy. This was where he worked on projects that used rigid-flex PCBs. His expertise includes analogue circuit design and electronics engineering. This blog was created by Hannah Ingram, a marketing manager who has experience in the tech sector, including electronics design and telecommunications.