What are Flexible Printed Circuits?

What are Flexible Printed Circuits?

Flexible Printed Circuits (FPCs) are a type of electronic circuit that is built on a flexible substrate, allowing for greater flexibility and compactness compared to traditional rigid PCBs. FPCs are widely used in various applications such as wearable devices, medical equipment, and consumer electronics.

The key features of FPCs include:

FPCs can be bent and flexed without breaking or damaging the circuit, making them ideal for applications where space is limited or where the circuit needs to be moved or flexed.

FPCs can be designed to fit into tight spaces, making them ideal for portable devices and other applications where space is at a premium.

FPCs are typically lighter than traditional PCBs, making them ideal for applications where weight is a concern.

FPCs are designed to be highly reliable, with low failure rates and long service lives.

FPCs are manufactured using a variety of techniques, including photolithography, etching, and plating, among others.

Overall, FPCs offer a range of benefits over traditional PCBs, including greater flexibility, compactness, and reliability.

Flexible Printed Circuit Finishing And Assembly

Flexible printed circuits (FPCs) are a type of electronic circuit that is built on a flexible substrate, allowing for greater flexibility and compactness compared to traditional rigid PCBs. FPCs are widely used in various applications such as wearable devices, medical equipment, and consumer electronics. The finishing and assembly of FPCs require specialized processes to ensure the reliability and functionality of the final product.

Here are some of the key steps involved in the finishing and assembly of FPCs:

• Material selection

The choice of materials for the substrate, conductive layers, and protective layers is crucial for the performance and durability of the FPC. Common materials used include polyimide (PI), polyester (PET), and other advanced polymers.

• Photolithography

This process involves creating the desired circuit patterns using photomasks and photoresists. It is a precise method that ensures accurate trace widths and spacings.

• Etching

After the photolithography process, unwanted copper or other conductive materials are removed through etching, leaving behind the desired circuit pattern.

• Lamination

Multiple layers of material may be laminated together to create a multi-layer FPC. This process requires precise alignment and bonding techniques.

• Drilling and Via formation

Holes and vias are created to allow for interconnection between different layers of the FPC. These can be formed using mechanical drilling, laser drilling, or other methods.

• Plating

Conductive pathways are plated onto the FPC to connect different parts of the circuit. Electroless plating is a common method used for this purpose.

• Inspection and Testing

Various inspection and testing methods are used to ensure the quality and functionality of the FPC. These may include visual inspection, electrical testing, and mechanical testing.

• Component Assembly

Surface-mount technology (SMT) or other assembly methods are used to attach components such as integrated circuits (ICs), resistors, capacitors, and connectors to the FPC.

• Connectorization

Connectors are added to provide interfaces for connecting the FPC to other electronic components or systems.

• Encapsulation

To protect the FPC from environmental factors and mechanical stress, it may be encapsulated with materials such as silicone, urethane, or epoxy.

• Final Testing and Validation

The completed FPC is subjected to final testing and validation to ensure it meets all specified requirements and performs reliably under expected operating conditions.

The finishing and assembly of FPCs require specialized equipment and expertise to ensure high-quality results. Manufacturers typically follow strict quality control procedures and adhere to industry standards such as IPCI (Interconnect and Packaging Electronics Institute) guidelines to maintain consistency and reliability across production runs.

Flexible Printed Circuit Board Design Advantages

Flexible circuit boards can be bent, folded, and configured into almost any shape or thickness imaginable, giving designers tremendous options when creating electronic packages. Compared to traditional designs using hardboard circuits, size, and space constraints are far less of an issue. Because the entire interconnection system can be built as one integrated component, assembly, and handling costs can be significantly reduced.

Flexible Printed Circuits The tremendous flexibility of this design choice allows electronic packages to become smaller, lighter, and more powerful.

Printed Flexible Circuits Fabrication

Surface preparation is often required to ensure that the flexible printed circuit surface is ready for subsequent bonding, such as SMT assembly, wire bonding, or pressure connector insertion. Nickel or gold, tin, silver, and solder are good metals for this purpose. Organic coatings can also be used to protect the copper until the bonding process dissolves the material away.

Flexible printed circuits have countless assembly options. In addition to electronic components and connectors, various electrical or mechanical devices can be connected to flex circuits. The circuit can also be easily bonded to curved surfaces or formed into any 3-dimensional shape. With the right construction, flexible circuits can handle dynamic bending, making them an ideal interconnect solution for electronic packages that connect moving or rotating parts.

The finishing and assembly of flexible printed circuits is an important part of the manufacturing process. Here are some common steps and techniques:
**Post-etching treatment**: After etching is completed, cleaning, film removal, and etching residue removal may be required.
**Drilling**: Drill holes on the flexible printed circuit to connect other components or conduct different layers according to the design requirements.
**Surface treatment**: such as gold plating, tin plating, etc. to improve conductivity and solderability.
**Place components**: Use an automatic placement machine to mount components (such as chips, resistors, capacitors, etc.) onto flexible printed circuits.
**Soldering**: Use appropriate soldering methods (such as reflow soldering, and wave soldering) to connect the components to the circuit.
**TESTING**: Conduct electrical testing to ensure continuity and performance of the circuit meet requirements.
**Fold and Bend**: If necessary, fold or bend the flexible printed circuit into the desired shape.
**Encapsulation and Protection**: Overlays, glue, or other encapsulation materials may be used to protect circuits.
9. **Quality Inspection**: Conduct final quality inspection, including appearance inspection, solder joint inspection, etc.

The specific implementation of these steps may vary depending on product requirements and manufacturing processes. The finishing and assembly processes require a high degree of precision and careful operation to ensure the reliability and performance of flexible printed circuits. In addition, automated equipment and strict quality control measures are often necessary in large-scale production. The true potential of flexible printed circuits may only be limited by the imagination of the designer! If you have more detailed questions about a specific finishing or assembly technique, contact a Shanyo design engineer today to learn more about the amazing possibilities that flexible circuit boards can offer.

Conclusion

Once past the prototyping stage, our customers often move to on-demand manufacturing, producing injection molded parts at Shanyo. Using a steel mold, part quantities are virtually unlimited. On-demand injection molding with us allows you to meet inventory needs with no minimum order quantities and offers supply chain flexibility through bridge tooling, just-in-time production, or dual-sourcing strategies.