Flexible PCB Material – Everything You Need to Know in 2024

Introduction:

Many customers are asking us what is flexible PCB material, so we write this article to discuss it. When you have any comments or questions, please send an email to us.

Which Material is Used in Flexible PCB?

Choosing the right flexible PCB material is critical to the proper functioning of the board. The material used determines the total cost, production time, and board functionality. It also affects the board’s load-carrying capacity, signal integrity, and overall weight.

Copper is the most widely used conductor material in flexible PCBs. It has good electrical properties and is easy to use. It is available in a variety of weights and thicknesses. It is a low-cost material that is commonly used in circuits. It is also susceptible to surface finishes prior to the board assembly.

In addition to copper, other conductor materials are used in flexible PCBs, including other alloys and conductive materials. These materials vary in cost and performance.

Another common material for flexible PCBs is a polyester resin. Polyester has excellent electrical and mechanical properties but is not suitable for use in hot environments. It is also difficult to obtain.

Flexible PCB substrate material

The flexible PCB substrate material

Another popular flexible PCB substrate material is liquid crystal polymer. LCP has the same properties as PI but is much more difficult to produce. At 1 GHz, LCP has a dielectric constant of 2.85. Because of its moisture resistance, LCP is a better choice for flexible PCBs than PI.

Metal stiffeners are often used to add stiffness. These are available in aluminum or stainless steel. They can also be used as heat sinks.

Substrate Materials Used for Flexible PCBs:

 

Substrate

Compared to rigid PCBs, flexible PCB substrates are both flexible and lightweight. Due to its thin thickness, flexibility, lightweight, and ability to bend millions of times without damaging conductors, it is suitable for high-density wiring applications.

Flexible PCBs can be made from a variety of substrate materials, including PI, PMMA, LCP, and TLCP. the most common flexible PCB substrate material is polyimide (PI). It is a thermosetting resin with excellent heat and tensile strength and chemical resistance.

Resin adhesives are commonly used to bond PI to the copper foil. The use of PI and copper bonding improves the reliability of flexible PCBs. Without the use of resin binders, PI and copper bonding improves the flexibility of PCBs.

To eliminate conductive ink penetration problems, the PCB design process should be simple and fast. In addition, the printed conductive layer must be low resistance and flexible.

Polyimide film is often used as a substrate material to make flexible circuit boards more flexible and easy to install. This film prevents damage to single-sided wires and other components. It has the sufficient tensile strength to support flexible PCBs. however, its tear strength is insufficient.

In addition, the thin-film substrate material acts as an insulator between circuits. It must be strong enough to withstand the bending process. This substrate material is lightweight and easy to install. It is also extremely heat-resistant and solderable.

Coverlay Films

Coverlay films protect a variety of electronic devices. Coverlay films can be used to protect integrated circuit package lead frames, flexible printed circuit boards (FPCs), and other electronic components. They can also provide EMI/RF shielding.

Epoxy and phenolic resins can be used to make coverlay films. Halogenated epoxy resins and aromatic epoxy resins can also be used to make them. Polyester resins can also be used to make them. Coverlay films have many properties, including high heat resistance, moisture resistance, weather ability, and flexibility. Coverlay films are easier to use than traditional adhesives.

Coverlay films are available in a variety of thicknesses. Polyimide films with thicknesses of 0.010 to 0.20 mm are one example. This film is very thin and ideal for small bending radii. It also has good bending properties. This coverlay is well suited for cell phones and other devices with small bend radii.

There are five basic components in the adhesive composition. Inorganic powder (e), metal carbonate (f), heat-resistant polyester (g), solvent-soluble polyimide (h), and non-conductive carbon black are examples of these materials (k). These components form a layer on one surface of a heat-resistant plastic film. The weight of each component should be between 5 and 70 parts.

The inorganic powder should be finely ground. Finely ground powder is advantageous in terms of press processability and heat resistance. However, the use of large amounts of finely ground powder should be avoided, as it reduces heat resistance and peels resistance.

Conductors

In contrast to insulators, conductors allow current and heat to flow freely through them. They are usually made of metals and are used for a wide range of purposes.

Metals such as gold, silver, and copper are considered to be excellent conductors. Because copper is hardened, it can be used in most mechanical and wiring systems. Silver is occasionally used as a conductor, but it is expensive to use on a regular basis.

Conductors are also capable of transferring electrical charges. The amount of charge that can be transferred is determined by the shape and size of the conductor. Shorter materials conduct electricity better than longer ones.

Conductors

Conductors

When a conductor contains more electrons, it conducts more electricity. The number of electrons in a conductor determines whether it is polar or nonpolar. Polar conductors carry a positive charge, while non-polar conductors carry a negative charge. Conductors can also be manufactured by combining polar and nonpolar metals. These mixtures are often used in electrical applications because they provide the best of both worlds.

The surface area of the conductor can be a positive circular insulator, a hyperbolic conductor, or a positive circular insulator with an additional metal coating. These conductors have a high conductivity value, which represents their ability to transmit electrical power.

Conductors are metals used to conduct electricity, heat, and sound. They can also be made of liquids or gases. Aluminum, copper, nickel, and gold are used in various industries. They are also used in automobile radiators to keep heat away from the engine.

Adhesives

Traditionally, adhesives are used to bond copper foils to PI (or other) films because, unlike typical FR-4 rigid boards, annealed copper has fewer “teeth” and heat and pressure alone are not sufficient to create a reliable bond. Manufacturers such as these offer pre-laminated single- and double-sided copper-clad films for flex circuit etching, with typical thicknesses of 12 and 1 mil. adhesives are designed for flexibility.

Adhesive-free” laminates are becoming more common due to new processes involving copper plating or deposition directly on PI films. These films can be used when finer pitches and smaller vias are required, such as in HDI circuits.

Silicones, hot-melt adhesives, and epoxies are also used when adding protective beads to a flex-to-rigid connection or interface (i.e., where the flexible part of the layer stack leaves the rigid part). These provide mechanical reinforcement for the pivot points of the flex-to-rigid connection that would otherwise fatigue, crack or tear from repeated use.

Adhesives

Adhesives

What Are the Rigid-Flex PCB Materials?

In electronics and other fields, rigid-flex printed circuit boards are used. These circuits have excellent heat dissipation capabilities. In addition, they can be bent at various angles and formed into various shapes. They can also withstand high levels of vibration and shock.

Flexible circuit PCB materials are typically a few microns thick. However, the thickness of the alignments may vary depending on the PCB design. The number of layers can also vary. Manufacturing costs can be reduced by using flexible circuits.

In addition, flexible circuits can be etched reliably. Polyimide (PI) and polyester are common flexible PCB materials. They are very durable, chemically and solvent resistant, and have high tensile strength.

For rigid-flexible circuit assemblies, copper foil is a common conductor. Copper foil is available in a variety of thicknesses and weights. It can also be ordered rolled or annealed. Copper foil can also be subjected to various surface treatments. Roughening and surface treatments are examples of these finishes.

In addition, a variety of materials are used for flexible to rigid interfaces. Epoxy resins, silicone resins, and hot melt adhesives are examples of these. These materials are used to strengthen the fulcrum of the rigid-flexible bond.

Rigid-flexible printed circuit boards are used in the automotive, military, and telecommunications industries. These boards are used in a variety of products such as in-car computers, electronic control modules, and handheld units.

Rigid-Flex PCB Materials

Rigid-Flex PCB Materials

Popular Stackups For Rigid Flex Circuit Construction

Choosing the right stackup of layers for a rigid-flexible circuit structure is critical to ensure that your design meets product requirements. Properly designed layer stacks reduce radiation and circuit interference, while also preventing crosstalk between layers.

In a typical multilayer stack, a dielectric core separates the layers. These stacks typically alternate between power and grounding layers. These stacks also help to reduce EMI by suppressing inter-layer crosstalk.

Other layer stacks can also be used to create rigid flexible circuit structures. For example, binder-style stacks use flexible layer pairs to create space. This type of structure can also be folded without putting stress on the outer layer of the flex tape.

A double-sided flexible PCB is the most common type of rigid-flex structure. The board consists of two layers of copper traces. An insulating middle layer then connects these two layers. This layer insulates the copper conductors and protects the alignment.

Rigid-flex PCBs are also available with one, two, or four layers. the number of layers in a rigid-flex PCB may vary depending on the target application. This type of board also saves space and weight.

Designing rigid-flex PCBs can be difficult. The material used, the number of layers, and the number of rigid-flex sections are all important considerations. For thermal issues, there are other design considerations.

Choose the Best Flexible PCB Manufacturer for Your Products

PCBMay has more than 12 years of experience in flexible PCB, so you just send your Gerber files to us, and we will provide satisfying goods for you.

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