What Is a Rigid-Flex PCB Assembly?

There are several different kinds of PCB assembly. A rigid-flex assembly may be the most common out of all the types. A rigid-flex PCB assembly is a printed circuit board that combines rigid and flexible elements. A rigid-flex circuit board (or RFPCB) comprises both flexible and rigid components. The flexible layer is typically located on the bottom side of the components, which can help the PCB withstand impacts and damage. Rigid-flex PCBs are primarily used in applications where wires and cables interconnect a series of boards assembled inside a device or product.

Many people do not understand how everything comes together or the different processes and machinery used in each industry. In this guide, we will look at a rigid-flex PCB Assembly, which is one of the most common types of boards for electronics. We will see what it is, how it is made, and what makes it unique from other PCBs.

Rigid-Flex PCB Assembling and Materials

Rigid-flex PCB assembly is an advanced manufacturing technique that combines two different types of substrates into a single assembly. The process of manufacturing rigid-flex PCBs starts with making a glass epoxy substrate with holes for leads and vias to be soldered on top of the traces and pads below. Then the conductive layer is applied to the substrate using screen printing or lamination technology. This technique creates a rigid-flex circuit with two layers: one layer is flexible, and another is rigid. It can be used to make various electronic products, including consumer electronics and medical devices. In a rigid-flex PCB assembly, rigid substrate and flexible substrate give many advantages over conventional manufacturing methods like rigid-only PCBs or flex-only PCBs.

The rigid substrate can be glass epoxy, FR4, or Rogers RO3003. The conductive layer can be a copper foil, copper-clad laminate (CCL), nickel electroplating, or copper electroplating. Rigid-flex PCBs are used in an application where the flexibility of the FPCB is required, but its bend radius must be limited.

Standard Techniques of Assembling Rigid-Flex PCB

Injection Molding

Injection molding is one of the most popular methods of assembling rigid-flex PCBs. It involves injection molding a plastic housing that can be used to house all of the internal components of a product, including chips and sensors. Injection molding allows for easy assembly because it does not require any soldering or crimping; it simply requires pressing together all of the components before inserting them into their respective slots in the plastic housing.

Soldering 

Soldering involves attaching electronic components by melting solder onto them using a soldering iron or another device that heats up enough to melt solder wire. Soldering is typically used in conjunction with other methods such as crimping or gluing, but sometimes it is done without any other joining method. Soldering is often used when assembling rigid-flex PCBs because it allows manufacturers to attach components without using extra materials like glue or epoxy.

Critical Benefits of Rigid-Flex PCB Assembly

The main benefits of rigid-flex PCB assembly include:

High-Density Design

Rigid-flex boards have a much higher density than traditional rigid PCBs due to thin-film technology and other advances in manufacturing processes. This allows for better use of space within a given device footprint while still allowing for large numbers of layers and components on each layer.

Improved Mechanical Performance

Rigid-flex boards provide improved mechanical performance over traditional rigid boards because they do not need to be cut from sheet metal to assembling them into larger assemblies, such as when making multi-layer backplanes. This means that there is no risk of damaging tracks or traces during assembly because they are still attached to the underlying substrate after being cut out from the panel. Additionally, flex circuits can be run through automated pick-and-place machines without causing damage to components or tracks.

Increased Reliability

Since the rigid-flex substrate does not need to be cut, it can be exposed outside the device case without affecting its operation or reliability. This allows for more efficient cooling inside the device case without worrying about how much flexing will occur if holes in the PCB where fans or heat sinks dissipate heat.

Improved Electrical Performance

Since rigid-flex boards do not need to be cut from sheet metal, they can be designed with thinner layers than traditional rigid boards. This means that they can carry more current per square millimeter than conventional wooden boards, which allows them to perform better under high-temperature conditions where standard rigid PCBs might fail due to their thicker layers and lower thermal conductivity properties.

Increased Design Options

The rigid-flex PCB assembly allows you to design your product with greater flexibility. The circuit board can be bent into different shapes while maintaining electrical contact between its layers. You can also use other materials for each layer — FR-4 boards for the rigid layer and flexible substrates for the flexible coating — which means that your design options are virtually unlimited.

Important Considerations for Rigid-Flex PCB Assembly

• The materials used in rigid-flex PCB assembly must have similar thermal expansion coefficients to bond together without causing any damage to the device. The process of bonding dissimilar materials can be challenging, as it requires specific tools and equipment to ensure a high-quality final product.
• The inner layer must have holes for components with no mounting holes on their surface.
• All components must have a ground pad or copper foil as a heat sink.
• If there are no mounting holes on a component, it should be placed on both sides of the double-sided board.

Final Thoughts

To sum things up, a rigid-flex PCB assembly is still the preeminent method for the mass production of electronic devices. There is no telling when or if another type of board will replace these boards, given its long history. However, in the meantime, companies that use rigid-flex PCB assemblies to meet their manufacturing needs are sure to take advantage of the many benefits associated with this technology.Now that you are familiar with the various elements of a rigid-flex PCB check out Hemeixin’s design guidelines and additional consideration on rigid-flexible PCB assemblies to learn more about this innovative technology.