Flexible Circuit Board
The design of a flex circuit is much different from rigid-board designs, and the fabrication process involves many steps. When choosing a flex PCB manufacturer, it is important to strike a balance between quality and price. The best flex circuit board producers will adhere to ISO, UL and IPC rules. In addition, they should offer a variety of services, including testing and electrical conformance.
Unlike rigid-boards, a flex-circuit design can be rolled or folded to accommodate the shape of a product. This flexibility gives designers a great deal of freedom when designing electronic products. The resulting product is typically lighter, smaller and more functional than a comparable product made with rigid-boards. The circuits on a flex-circuit are also more durable, making them an ideal choice for high-speed digital, RF and microwave applications.
A flex-circuit can be manufactured with either an additive or subtractive process. Subtractive processes use copper to create the desired circuit layout, whereas additive processes are based on film and photo-imageable solder masks. flex circuit board manufacturers made with additive processes are more expensive, but they can be created faster and have better current-carrying capability and environmental resistance.
A Beginner’s Guide to Flexible Circuit Board Manufacturers
For a flex circuit, the design process starts with the creation of a CAD image. This image is then converted into a Gerber file, which is used to create the manufacturing data for the flex circuit. The Gerber files are then analyzed for errors and defects. The faulty areas of the circuit must be discarded before the final etch and laminate steps can be completed.
Drill-to-copper distance is a critical factor in the design of any flex circuit, especially during production. Ensure that this distance is at least 8 mil to reduce stress on the copper. Additionally, a flex-circuit should be designed to have pad and via plating with a thickness of at least 1 mil. This provides more mechanical support to the pads and vias. It is recommended that through-holes be designed with a diameter of at least 1 mil, to prevent them from cracking during the etch process.
In a flex circuit, the conductors must be staggered to avoid stacked copper traces. This will prevent the traces from breaking during bending. Also, the traces should be shaped to a smooth radius in the area where they are expected to bend. This will increase the bending radius and improve tear resistance.
To improve the electrical performance of a flex-circuit, it can be shielded from electromagnetic interference (EMI) and radio frequency interference (RFI). Shielding techniques are achieved with plated or silver inks or specialized films. The shielding should meet reference plane and EMI criteria to obtain regulated impedance values. Solid copper shield layers provide the best shielding, but this decreases flexability. Cross-hatched copper or silver inks can be used to achieve a similar effect with less flexibility.
A flex circuit can also have a graphic overlay, which is an acrylic or polyester cover that allows the user to interact with the circuit. This can include LEDs, LCDs and switches. The overlay is bonded to the circuit using an adhesive, or it can be etched directly into the copper layer. In some cases, the overlay may be connected to the flex-circuit by using a hot bar solder connection.