Flexible circuit boards are made from a variety of materials. Polyimide or copper foil can be used. The former is more durable than copper foil but has limited flexibility. The copper foil has the advantage of lowering costs and encouraging reuse. Polyimide material is a great choice for a flexible circuit board manufacturer because it allows for great flexibility and high thermal resistance. Copper foil, on the other hand, is more prone to bending.
Polyimide
Polyimide is a synthetic polymer that is the base for many PCBs. This material is made from various chemical compounds that contain imide structures. These compounds are often used in PCB fabrication because of their outstanding thermal stability and high resistance to fluctuation in temperature. In addition, polyimide is highly durable, retaining its shape even under extreme temperatures. Therefore, it is used for flexible circuit boards, including superior electrical and thermal conductivity.
The flexibility of polyimide is also valuable for many applications, including medical electronics and imaging technology. Medical electronics must be lightweight and free from signal interference, and polyimide PCBs are the only solution that can meet those requirements. Military and aerospace electronics are also sensitive to hostile environments, and polyimide PCBs are essential for these environments. These materials are resistant to chemical conduction and corrosion, enabling uninterrupted operation and increased safety for operators.
A typical two-layer flex consists of a rigid core and a flexible layer sandwiched between the two. The flexible layer is made of polyimide and is lighter than FR4. As a result, the flex material has good mechanical properties, which allows for a smaller mechanical footprint. Unlike FR4, polyimide flex material is also very suited for high temperatures and is resistant to oils, gases, acids, and other chemicals.
Low-flow polyimides are similar to standard PCBs but contain extra filler materials to reduce the resin shrinkage. Resin shrinkage is a major threat to PCBs, as it makes them frail and prone to cracks. Polyimide PCBs can handle these challenges with the extra fillers and remain flexible for longer. But they have their downsides as well.
Because of these benefits, polyimide PCBs are commonly used in applications requiring high-quality, affordable, and versatile circuit boards. In addition, polyimide PCBs are stronger and more durable than FR4 boards and are suitable for applications where durability and mobility are important. Polyimide is also better for absorbing heat than FR4 PCBs, making them the better choice for a wide range of applications.
Copper foil
The materials used to make flexible circuit boards are generally copper foil and insulating material. Copper foil can be a standalone material or laminated with a thin stiffener. Copper foil is also used in circuit boards as a conductive layer to reduce impedance and facilitate the welding of the components. The copper foil has many properties that make it useful for circuit boards. It must be 99.8% pure, free of wrinkles, blisters, and scratches, and its thickness must be less than 5 microns.
The basic PCB is made of a sheet of insulating material with a layer of copper foil. This copper is then divided by a chemical process into separate conducting lines known as pads or vias. These lines and vias are insulated from the air and serve as the physical connection between components. Some PCBs have surface-mounted components, and some are made with through-hole components.
Copper foil is a popular material for PCBs because of its low surface oxygen. It is a very versatile material that can be bonded to various substrates and is useful for anti-static and electromagnetic shielding. Copper foil is conductive, and it can be placed on the surface of a PCB to provide good continuity. Further, copper foil is available in many forms: single and double copper foil.
Electrolytic copper foil is less expensive than electrolytic copper foil. Copper foil can be rolled to achieve the desired thickness. Copper foil that is 12 micrometers thick has better adhesive strength and bending resistance. Copper foil with a higher temperature is not as flexible. It is also prone to corrosion and may rust when used in electronics. Further, electrolytic copper foil can be an abrasion-resistant alternative for FPCs.
