The fabrication and manufacture of electronic devices incorporates printed circuit boards (PCBs) that exist in three states: rigid, rigid-flex, and flex. Therefore, you must choose the best and the most efficient type for your setup. However, flex PCBs are the most applicable in dynamic electronics. Additionally, flat flex PCBs are easier to fabricate and saves time. So why will you choose them over the other types?
A Brief Overview
Flat flex PCBs are cable-like small outline printed circuit boards with a lightweight and low profile that we can fold to any shape. Additionally, they are applicable in high-density connections. However, current flat flex PCBs have repeated dynamic flexing and stress.
How to Design A Flat Flex PCB
Designing a flat flex PCB can be pretty challenging. However, following the steps below will provide a solid solution.
- Before kicking off the designing process, it is pivotal to understand the electrical parameters applicable to the PCB. For instance, you must consider such factors as voltages, current maximums, impedance characteristics, capacitance limitations, etc.
- Next, a design schematic will aid in the design work. Here, you present an overview of the flat flex PCB you intend to design. In this case, you will clearly define the shape of your flat flex PCB. Additionally, the PCB’s bendability will differ depending on the function of your PCB. That is, whether the PCB is dynamic or static. For a dynamic flat flex board, bending may be more often and more intense than a static one.
- You use a schematic design tool to create the flat flex PCB layout you intend to fabricate. Here, you can use such software platforms as Allegro, KiCad, Altium, or Mentor PADS. These platforms will show you what your flat flex PCB will look like and where the components should be.
- Again, based on the compatibility of your components, please place them in such a way that such disturbances as electrical noise will not arise. First, you will design holes for each element, linking them with air wire connectors. Now replace the air wires with actual wire connectors.
- Then, you now add identifiers, notations, reference designators, or markings to each component.
- Finally, generate the layout files/design using the program. The files contain the formatting information of the PCB design, and developing them means the PCB is ready for manufacture.
Material composition in flat flex PCBs
Flat flex PCB circuits have the following materials:
- Cover layer and insulator– Manufacturers use polyimide insulators and dielectrics. It, therefore, insulates the copper conduct on the flat flex circuit.
- Conductor– Electronic engineers prefer using copper foil as the central conductor due to its high-level electric conductivity. However, using so much of it may not be necessary; a sizeable amount will also conduct. In addition, a low temperature or fully annealed conductor also functions excellently. Consequently, adding them to your flat flex PCB facilitates better flexing characteristics.
- Finish type– The surface finish of a flat flex PCB provides a solderable surface and prevents copper oxidation. For instance, Nickel Immersion Gold (ENIG) is a perfect finish. Moreover, it is present on over 80% of the PCBs. Additionally, ENIG provides a thin solderable gold layer with a nickel layer between it and copper to eliminate copper traces.
Also, manufacturers incorporate Electroless Nickel Electroless Palladium Immersion Gold (ENEPIG), the three-layer metallic finish. In this case, electroless nickel avoid contact between copper and the other metals. In addition, Palladium prevents nickel corrosion, establishes a wire-bonding layer, and prevents copper oxidation. Moreover, the gold layer provides a barrier against oxidation and exposes a solderable layer on the flat flex PCB.
Cost Determiners In Flat Flex PCB Circuits
Every engineer works towards providing a high-performance, cost-effective PCB. However, some factors may force price hikes in the flat flex PCBs.
- Circuit shape and size – You cannot fit many large flat flex circuits on a single manufacturing panel. Consequently, the price with smaller flat flex PCB circuits will be higher due to the many components present.
- Layer count – For multilayer circuits, each layer requires additional materials and time. Also, stacking the layers may be challenging. Therefore, the more layers, the higher the price.
- Circuit class – The IPC class of the flat flex PCB determines its price. For example, a class 3 flex circuit will require more serialization and validation coupons than class 2. Therefore, a class 3 flat flex PCB circuit will have a higher price than a class 2.
- Dimensional tolerances – Rigid PCBs require more tolerance than flex PCB circuits. Since you must verify each dimension, a rigid PCB circuit will be more expensive than a flex PCB.
- Final finishes – The more the final finishes layers, the higher the cost. Therefore, reducing the finish layers facilitates lower flat flex PCB prices.
- Smaller components – Additional layers with smaller parts mean you will add more of them. Therefore, add additional layers with larger components/features to reduce the PCB price.
- Buried and blind vias – A vertical interconnect access (VIA) is a through-hole that routes a vertical trace from one board to another. Vias are more expensive than through holes.
Advantages Of Flat Flex PCBs
Flat flex PCBs offer several benefits that make them more suitable for PCB designs that require space and weight minimization. The following are some of these benefits:
- Constantly reliable – Customizing a routed path within a PCB is very easy with a flat flex circuit. Consequently, it becomes more reliable.
- High-temperature tolerance – Flat flex circuits endure high-temperature conditions, making them suitable for fields such as military, aerospace, medical, and downhole oil derricks.
- High vibration – Due to their flexible nature, flat flex PCBs are easily foldable. Therefore, you can change their shape without losing their strength or breaking them. Hence, they can endure high mechanical vibrations.
- Improved signal reception – High-speed digital systems require flat flex PCBs due to their high-speed transmission. They cater to the degraded square wave pulse signal, increasing the number of the rapid rise and hence high speeds.
- Space efficient – Flat flex PCB circuits have an internal connection that replaces wires and cables. They, therefore, reduce the net package weights and save the net space it occupies.
- Extended duty cycles – The circuits carry enormous power and signals without disruption. Therefore, they can tolerate large cycles and are more durable.
The above information gives enough details about flat flex PCBs. Moreover, it outlines the designing procedure, putting across their material composition. Furthermore, the information gives tips on how to create cost-effective but highly reliable PCBs. In addition, the information has explained the advantages of flat flex PCBs, which are why you should pick them for your study. All electronic devices incorporate either of the three types of PCBs, with flat flex taking the lead in reliability, efficiency, and flexibility.