- Types of PCBs in the modern world
- Understanding rigid-flex PCBs
- Advantages of rigid-flexible PCBs
- Rigid-Flex PCB manufacturing process
- Demand for rigid-flexible PCB designers
- Rigid-flexible PCBs should pay attention to the problem.
- Rigid-flexible PCB manufacturing applications
- Summary
Modern electronics have benefited from advances in materials and computerization, which have allowed PCBs to evolve into hybrid rigid-flex and multilayer boards. Rigid-flex PCBs are the latest advancement in printed circuit board technology. Flexible layers are combined into a rigid frame to balance the complexity and reliability of rigid board circuits. Rigid-Flex PCBs are smaller, thinner, and more flexible and can be used in irregularly shaped or compact devices.
Today, PCBs are used in a variety of industries. They have moved beyond the stigma associated with chemical PCBs and are called private circuit boards. This is largely due to the phasing out of chemical PCBs over the past 40 years. As printed circuit boards continue to evolve, it can be assumed that they will become smaller and more complex in the coming years.
Types of PCBs in the modern world
Printed circuit board (PCB) manufacturing technology, design parameters, and application requirements are divided into the medical, automotive, defense, and space exploration industries.
More complex designs based on consumer needs and expectations have produced a wide range of printed circuit boards. Single-sided, double-sided, multilayer, rigid, flexible, and rigid-flexible PCBs are used in different industries today. Putting the others aside, let us focus on the most commonly used PCBs – rigid-flexible circuit boards.
Understanding rigid-flex PCBs
RFPCBs combine flexible technology and rigid boards in one application. Depending on the application design, which can be rigid or flexible, PCB usually consists of multiple layers connected to one or more rigid boards from the outside and inside. The flexible substrate is typically molded into a curve during fabrication and mounting to maintain consistent flexing.
Advantages of rigid-flexible PCBs
When rigid-flexible boards are used for interconnects, large and inconvenient connectors no longer need to be used, thus significantly reducing the RF PCB.
Because rigid-flex PCB designs are made in three dimensions, they are somewhat difficult to design as the board twists and folds to form whatever shape the product requires. However, rigid-flexible materials allow for compact construction of the board. Their lightweight nature makes them an excellent choice for various applications in aircraft, medical technology, and consumer electronics. Other benefits include
– 360-degree bendability.
– Lightweight.
– Reduced space requirements through 3D functionality.
– Vibration resistance.
– Fewer solder joints ensure higher connection reliability.
– Simplifies the PCB assembly process.
Rigid-Flex PCB manufacturing process
Since its inception, the RFPCB manufacturing process has become more refined. In recent years, the development of revolutionary rigid-flexible PCB manufacturing technology has led to the use of FR4 (glass fiber epoxy) as a rigid external circuit board with a solder resist layer placed on top of the rigid layer to hold the circuit in place.
In addition, flexible substrates are made from double-layer polyimide (PI) sheets coated with copper for added strength. Finally, an acrylic film attaches the flexible design pattern to the substrate. To develop rigid-flexible circuits, PCB manufacturers follow the following steps.
– Basic Preparation
– Build the circuit
– Etching copper foil
– Precision drilling
– Hole plating
– Covering with board
Demand for rigid-flexible PCB designers
Due to the miniaturization trend, there is a high demand for PCB designers who are proficient in rigid-flex design. Before you start, it is critical to understand that building a rigid-flex PCB differs from the capabilities required to develop a standard PCB.
Rigid-flex PCB designs should typically be mounted in an enclosure and must consider the design’s mechanical characteristics. However, because the flexible part of the PCB sometimes bends to a certain extent, you need to consider the mechanical stresses applied to the material. Bending lines, also known as bending areas, must be handled to avoid premature failure.
If possible, avoid using over holes and pads in the bend area, as mechanical stresses may cause pad damage. Alignment routing parallel to the bend line is also essential to maintain structural stability. In addition to the current alignment, you can add false alignments to the bend area to make it more robust.
Rigid-flexible PCBs should pay attention to the problem.
1, rigid-flexible PCB design usually changes from rigid to flexible and then rigid. Rigid areas generally have more layers than flexible areas, and the material is transferred from FR-4 to polyimide on the transition area. When an intersection occurs, the overlap of rigid and flexible materials requires that the holes be kept away from the transition region to maintain integrity. In addition, many rigid-flex designs incorporate reinforcing materials such as stainless steel or aluminum to provide additional support for connectors and components.
2, flexible PCB circuits have bent wires that can interfere with wiring. Due to possible material stress, it is impossible to place components or vias near the bend line. Even if components are placed correctly, flex circuits can cause repeated mechanical stresses on surface mount pads and vias. These stresses can be relieved in this case by using through-hole plating and supporting the pad with additional overlays
3, in the design of rigid-flexible PCBs, you need to consider the electromechanical factors affecting flexible PCB circuits and rigid PCB boards. You pay attention to the ratio of bending radius to thickness. For flexible PCB circuits, narrowing or increasing the thickness of the bending area will increase the likelihood of failure. This situation is recommended to keep the bending radius at least ten times the thickness of the flexible PCB circuit material.
4, avoid making the flexible PCB circuit along its external bending or internal compression; the bending angle will increase to more than 90 °, increasing the tension of the flexible PCB circuit at a certain point and the pressure at another point.
5, the key issue of rigid-flex reliability is the thickness and type of conductor in the flex region. The use of heavy copper, gold, or nickel plating will reduce flex flexibility and allow mechanical stress and fracture to occur; thickness and mechanical stress can be reduced by reducing the amount of plating on the conductor and using only pads.
Rigid-flexible PCB manufacturing applications
Rigid-Flex PCBs offer various applications, from smart devices to cell phones and digital cameras. Rigid-flex PCB manufacturing has been increasingly used in medical devices such as pacemakers to reduce their space and weight. The use of rigid-flex PCBs offers the same advantages for intelligent control systems.
In consumer products, rigid-flex PCBs not only maximize space usage and minimize weight but also greatly improve reliability, eliminating the need for soldered joints and fragile and delicate wiring prone to connection problems. These are just a few examples, but rigid-flexible PCBs can benefit virtually any advanced electrical application, including test equipment, tools, and automobiles.
Summary
Rigid-flex combination PCB boards help us meet complex geometric or EMI requirements by allowing us to use flexible PCB circuits or rugged rigid PCB boards whenever possible to minimize manufacturing and assembly costs.