How to Get Started with Flex PCB Designs

Flex circuits are becoming more popular among PCB designers and are the new go-to for circuit designs. Flex PCB manufacturers can offer a PCB that relies on a flexible substrate, making it bendable and ideal for certain applications. The PCB board can be curved, folded, or placed in tight spaces because of its flexibility compared to rigid PCBs. This feature is ideal for wearable devices like wristbands and fitness bands.

If you are an engineer or a novice in PCB design, getting your first designs made can seem a bit overwhelming. This is especially true for those just now creating their first printed circuit boards (PCBs). However, it is not as complex as you might think. With the right resources and information, it can be pretty straightforward, even for complete beginners. Here, we have put together a guide on how to get started with flex printed circuit board designs.

Getting Started with Flex PCB Designs

Define Your Design Needs

The first step in the design process is to define your design needs. To do this, you need to determine what your product will be used for and who will use it.

For example, if you are designing a smartwatch, you need to know if it will have a touchscreen, how many buttons it will have, and if they should be touch-sensitive. If you are designing a sensor board for an industrial application, you need to know what kind of sensors you want to include on the board and their physical dimensions.

Once you know these requirements for your project, it is time to select the suitable materials for your application.

Choose the Right Flex PCB Materials

In addition to knowing the requirements for your project, it is also essential to know what materials are available for creating flex circuits: FR4 (glass epoxy laminate) material is the most common choice for building flex circuits because it offers excellent electrical performance and resistance to heat and chemicals. However, other options include polyimide films, Teflon-based materials, and even paper or plastic substrates (for low-cost prototypes).

A polyimide is an alternative that provides better performance at higher temperatures and frequencies but can be more expensive than FR4. Teflon-based materials provide excellent environmental protection at low temperatures but may require a protective layer at high temperatures to prevent corrosion damage caused by hot solder joints or soldering fluxes.

Get Started with the Right Tools

The next step is choosing the right tool for your project. There are many different options when it comes to software tools that can help you create your flex PCB design, including:

Design Software

These programs allow you to create the entire schematic for your circuit, including any components that need to be included. You can also use these tools to design your board layout, which consists of all the traces required to connect your components.

Routing Software

Once you have created and saved your schematic, this software will help you route each trace on your board so that they meet up properly. This also helps ensure no signal conflicts between adjacent traces or connections between traces on different layers of the board.

Prototype Services

When it comes time to build your prototype and test it out in the real world, you may want a company specializing in prototype services rather than doing it yourself at home or in-house. Some prototype services will even handle testing, debugging, and certification if needed before sending you your product.

Flex PCB Design Considerations

When designing flex PCB assemblies, consider the following factors that will affect how your design integrates into its enclosure.

Floorplanning

The dimensions of your PCB are limited by the size of the enclosure to which it will be mounted. You must plan for any space needed for mounting hardware, such as standoff screws and spacers. Also, check for clearance around connectors, switches, and controls so they can be easily accessed during operation and maintenance.

Layer Count

The number of layers required for your assembly depends on what functions you have on each layer. For example, if you have a small number of surface mount components on one layer and large through-hole components on another, you may want to consider using more than two layers in your design. The more layers you use, the smaller they can be made without affecting performance or causing manufacturing issues such as solder joint voids. However, remember that too many layers may increase cost due to extra panelization steps during manufacturing.

Layer Stack-Up

The order in which layers are stacked is critical to achieving good signal integrity. The stack-up should be designed such that signals travel along the shortest path possible between their source and destination. This helps reduce reflections that can cause signal degradation over longer distances.

Signal Routing

Signal routing is an essential factor when designing flex PCB assemblies. Each signal needs to be routed from one point to another without crossing other signals or traces on its way there. This means keeping traces as short as possible while avoiding sharp bends, which can cause signal reflections and crosstalk with nearby traces.

Connectors and Components

In addition to size limitations, you must consider the connectors and components used in your design. For example, if you have many high pin count connectors, you may need more space on the front panel or backplane to accommodate them all. Pay close attention to how much space each component takes up when planning your front panel or backplane layout.

Stiffness

Flexible circuits are more susceptible to damage during handling than rigid PCBs because they have less structural support. The flex circuit must be stiff enough to withstand everyday handling while still being flexible enough to bend when needed. When designing your flex circuit, make sure it has enough stiffness to prevent damage during servicing but also enough flexibility so it can bend easily in use.

The Takeaway

The process of creating a new PCB design from scratch can be pretty overwhelming at times. There are many things to keep in mind, such as the type of layer stackup, etching and plating specifications, adding text to your boards, etc.; for this reason, you must get organized before you even start designing. While this is certainly not the most comprehensive guide on flex PCB design in general, we hope it will serve as a good reference for you and help you get started with flex PCBs. If you want to learn about more comprehensive and in-depth design guidelines for flex PCBs, check out Hemeixin HDI PCB.