The function of the film substrate is to provide the conductor carrier and the insulating medium between the lines and can be bent and curled at the same time. FPC soft board substrates commonly used PI polyimide film and PET polyester film. Flexible copper clad laminates and rigid copper clad laminates also have halogen-free environmental protection requirements, and green materials are an inevitable trend. The mechanical and electrical properties of polyester (PET) resin are acceptable, but the biggest disadvantage is poor heat resistance and is not suitable for direct welding assembly. The adhesive combines the copper foil with the base film. Commonly used are PI resin, PET resin, modified epoxy resin, and acrylic resin.
2. Flexible copper-clad laminates (FCCL)
Flexible copper-clad laminates (FCCL) usually have a three-layer structure, namely polyimide, adhesive and copper foil. Since the adhesive will affect the performance of the flexible board, especially the electrical performance and dimensional stability, a two-layer structure flexible copper clad laminate without an adhesive has been developed. At present, there are many methods of depositing electroplated metal layers on polyimide films, and the two-layer structure copper clad laminates tend to be used for flexible boards with high-performance requirements.
3. Liquid crystal polymer (LCP) copper clad laminates
Liquid crystal polymer (LCP) copper clad laminates are continuously hot-pressed from a thermoplastic liquid crystal polymer film covered with copper foil to obtain single-sided or double-sided copper-clad laminates. The water absorption rate is only 0.04%, and the dielectric constant is 2.85 at 1GHz. It is suitable for high frequency boards. Requirements. The polymer is in a liquid crystal state and will melt when heated as a “TLCP hot-melt liquid crystal polymer”. The advantages of TLCP can be injection-molded, can be extruded into a film to become the substrate of PCB and FPC, and can be processed twice for recycling. The low hygroscopicity, high frequency suitability, and thermal dimensional stability of TLCP film make TLCP film enter the application on FPC-COF multilayer substrates.
4. Halogen-free (bromine) substrates
Halogen-free (bromine) substrates have been developed and applied in both rigid and flexible boards. For flexible substrates, including FCCL, cover films, adhesive sheets and solder resist, as well as reinforced boards, they must be flame-retardant and halogen-free.
5. Conductive material
The conductive material of the FPC soft board is mainly copper-copper foil, and some alloys such as aluminum, nickel, gold, and silver are also used. In addition to conducting electricity, the conductor layer must be resistant to bending. According to different production methods, there are two types of copper foil: electrolytic copper foil and rolled copper foil. The difference between RA and ED copper foil is that the crystal shape is different. RA copper foil is arranged in a columnar shape, with uniform and flat structure, easy to roughen or etch treatment; ED copper foil is a stack of fish-scale sheets, and the rolled copper foil is smooth and tough Good, but roughening or etching becomes difficult.
6. Conductive inks
In the manufacture of FPC flexible boards, conductive inks are used to print conductive inks on insulating films to form wires or shielding layers. Most of these conductive inks are silver paste conductive pastes. The conductive layer formed by printing is required to have low resistance, strong bonding, flexibility, and printing operations. Easy to cure. The use of conductive ink to make graphics is also environmentally friendly and low-cost technology.
Below are some flex PCBs with Dupont PI material:
1. Title: Key Factors in PCB Design
2. PCB design is a crucial part of electronic products. A good PCB design can not only ensure stable and reliable circuit performance, but also improve the overall quality and reliability of the product. Below, we will introduce some key factors in PCB design.
3 Circuit layout: A good circuit layout can minimize signal interference and crosstalk, and improve the stability and reliability of the circuit. When conducting circuit layout, it is necessary to pay attention to analyzing the signal transmission path and avoid signal crossing and interference as much as possible.
4 Line width and spacing: Appropriate line width and spacing can not only reduce the impedance of the circuit board, but also improve the reliability of the circuit. When designing a PCB, it is necessary to choose the appropriate line width and spacing based on the frequency and power of the signal.
5 Grounding design: A good grounding design can effectively reduce the return path of signals, reduce signal loops, and reduce signal interference. When designing a PCB, it is necessary to plan the grounding circuit reasonably, shorten the grounding circuit as much as possible, and reduce the grounding resistance.
6 Power supply design: A stable power supply can ensure the normal operation of the circuit. Therefore, when designing a PCB, it is necessary to fully consider the layout and connection method of the power supply, minimize the common mode voltage of the power supply circuit as much as possible, and improve the anti-interference ability of the circuit.
7 Temperature control: Good temperature control can extend the service life of electronic products. When designing a PCB, it is necessary to layout the heat sink and ventilation holes reasonably to ensure the heat dissipation effect of the circuit board and avoid overheating and damage to circuit components.
8 Bus layout: When designing a PCB, a reasonable bus layout can reduce signal transmission paths, signal interference, and latency. Therefore, it is necessary to fully consider the signal transmission path, plan the bus layout reasonably, and improve the performance stability of the circuit.
9 Conclusion: The above are some key factors in PCB design. Through reasonable circuit layout, line width and spacing, grounding design, power supply design, temperature control, and bus layout, the reliability and performance stability of electronic products can be improved.
