flexible PCB fabrication related to IoT devices
Flex circuits make up a significant percentage of IoT devices like fitness trackers and smart jewelry, as they provide the necessary durability to conform to their wearer’s body and monitor health metrics discreetly. However, flexible circuits aren’t limited to consumer products; they are increasingly used in industrial IoT applications where a device must endure harsh operating conditions like temperature extremes and moisture.
To create a flexible pcb fabrication, first the design must be created using CAD software, taking into account the placement of components and any specific requirements related to bending and flexing. Once the design has been finalized, it must be analyzed for fabrication feasibility by a PCB engineer. This step ensures the final product will have all the necessary features and functionality to meet your specifications.
Next, the circuit board material must be selected. Polyimide and polyester (PET) films are commonly used as they have excellent electrical insulation properties, high-temperature resistance and flexibility. Conductive materials like copper are then deposited on the PCB, creating the circuit pathways needed for operation. This process is called “buildup”. It involves a series of photoresist layers that are aligned with the desired mask pattern, then exposed to UV light to expose the resist and develop it before the copper is chemically etched.
How is flexible PCB fabrication related to IoT devices?
During the buildup process, vias (through holes) are made through the copper layer to allow electrical connections to be made. These vias must be carefully placed to allow for flexing and bending without damaging the circuit board, especially during reflow soldering. The resulting vias are then filled with solder paste to provide electrical continuity to the component contacts.
Once the conductive paths have been plated, a coating is applied to the bare circuit board to protect the metal from corrosion and provide a visual appearance. This coating is known as the coverlay, and it is essential for the long-term reliability of a flex circuit. It also provides a shield against electromagnetic interference (EMI).
After the coverlay is applied, a stiffener is placed on the flex PCB to strengthen it during the manufacturing and assembly processes. A flying probe test is then performed to ensure that the PCB meets its design requirements, including bending and soldering.
Finally, the flex PCB is cut to its final shape and inspected for any defects before being packaged and shipped for use. Innovations in flexible PCB fabrication like laser direct imaging (LDI) and roll-to-roll lamination have refined the process to reduce cost and increase production speed. They have also improved trace patterning accuracy and enabled the creation of conductive paths in highly bendable areas, critical for IoT devices with small and unconventional geometry. Despite these advancements, industry experts have not yet been able to accurately determine how far a flex circuit can be bent before damage occurs. This uncertainty makes it important for designers to consult experts who have experience with flex circuits to ensure they are creating a safe and reliable product.
