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FR-4|Advanced PCB

PCB sampling and mass production services from 1 to 42 layers. We use real A-grade plates, adhere to the factory's self-operated production model, and ensure the reliability and stability of quality. Brand new high-rise dedicated production line, the circuit soldering prevention adopts advanced production equipment in the industry such as LDI, VCP pulse plating, etc., uses famous brand plates, precise impedance detection instruments, and provides high-definition characters, high-quality inspection standards, high-end packaging and transportation services.

Multi-Layers(Partial Technology Capability)
Layer count 1~42L
Core thickness（Exclude copper） 50um
Min mechanical hole size 100um
Inner outter layer registration Mini pad Dia. DHS+6mil
Min. S/M dam 50um
Min. S/M opening size 4mil
Via Covering Epoxy Filled & Untented, Epoxy Filled & Capped,Copper paste Filled & Capped
Solder mask color Color.png
Solder mask ink thickness ≧10um
Depth-Controlled routing tolerance ±0.05mm
Minimum Legend Width 6mil(0.15mm)
Surface Finish

HASL/ImmersionTin/ImmersionSilver

/ImmersionGold/ENEPIG/OSP

 

For more information, please click 【here】.

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    product details
    FR-4 Substrate
    The "Cornerstone" Material in the PCB Field

    1. Introduction: Definition and Industry Status of FR-4

    In the manufacturing of printed circuit boards (PCBs), the substrate is one of the core elements determining the performance, reliability, and cost of the circuit board. FR-4 (Flame Retardant Type 4), as a glass fiber-reinforced epoxy resin substrate, has become the most widely used rigid PCB substrate due to its excellent mechanical properties, electrical properties, heat resistance, and flame retardancy, accounting for more than 80% of the global PCB substrate market. Whether in consumer electronics, automotive electronics, industrial control, or communication equipment, FR-4 is the "cornerstone" material for realizing circuit interconnection and component carrying.
    The naming of FR-4 originates from the standards of the National Electrical Manufacturers Association (NEMA), where "FR" stands for "Flame Retardant" and "4" is the classification number for this type of flame-retardant substrate. Its emergence solved the problems of flammability and poor heat resistance of early PCB substrates, providing key guarantees for the safe and stable operation of electronic equipment.

    2. Core Composition and Structure of FR-4

    FR-4 substrate is a composite material mainly composed of three parts: reinforcing material, resin matrix, and additives. Its structure can be divided into two forms: "core board" and "prepreg" (used for multi-layer board lamination):

    2.1 Core Composition Components

    • Reinforcing Material: Alkali-free glass fiber cloth (E-Glass Fiber Cloth) is used, which is the main source of FR-4's mechanical strength. The specifications of the glass fiber cloth (such as yarn fineness and weaving density) directly affect the thickness, rigidity, and bending resistance of the substrate. Common glass fiber cloth models include 106, 1080, 2116, 7628, etc. Among them, 7628 cloth is widely used in the core boards and prepregs of multi-layer PCBs due to its moderate thickness (about 0.18mm) and high strength.
    • Resin Matrix: Epoxy resin is the main component, which has excellent adhesion, electrical insulation, and chemical stability. When epoxy resin combines with reinforcing materials, it can form a dense structure to block moisture and impurities from entering.
    • Flame Retardant: To meet flame retardant requirements, flame retardants need to be added to the resin. The commonly used one is brominated flame retardant (such as tetrabromobisphenol A, TBBPA), which prevents flame spread by inhibiting free radicals in the combustion reaction. With the strictening of environmental regulations, halogen-free flame-retardant FR-4 (using phosphorus-based and nitrogen-based flame retardants) has also gradually become popular.
    • Other Additives: Including curing agents (such as dicyandiamide), accelerators, fillers (such as silica), etc. The curing agent causes the resin to undergo a cross-linking reaction to form a solid structure; the accelerator speeds up the curing process; the filler can reduce the resin shrinkage rate and improve heat resistance and dimensional stability.

    2.2 Structural Forms

    • Core Board: A fully cured FR-4 substrate with electrolytic copper foil (usually 12μm, 18μm, 35μm thick) coated on both sides. It is the base layer of single-layer PCBs and multi-layer PCBs. The thickness of the core board has a wide range, from 0.2mm to 3.2mm, which can be selected according to the design requirements of the PCB.
    • Prepreg: An incompletely cured FR-4 material, made by impregnating glass fiber cloth with epoxy resin and then drying it, in the form of a sheet. In multi-layer PCB manufacturing, prepreg is sandwiched between core boards, and heated and pressed under high temperature and pressure (usually 180-220℃, 20-40kg/cm²). The resin melts and flows, filling the gaps between layers, and at the same time cures to form an integral structure, realizing the bonding and insulation of each layer of core boards.

    3. Key Performance Indicators and Characteristics of FR-4

    Performance Category
    Key Indicators
    Performance Characteristics
    Typical Application Requirements
    Mechanical Properties
    Bending Strength, Tensile Strength, Impact Strength
    High rigidity, strong bending and impact resistance, can provide stable support for components
    Withstand component soldering pressure and mechanical processing force during PCB assembly
    Electrical Properties
    Dielectric Constant (Dk), Dielectric Loss (Df), Volume Resistivity
    Stable dielectric constant (usually 4.2-4.8@1GHz), low dielectric loss, excellent insulation performance
    Reduce signal attenuation and interference during high-frequency signal transmission, ensuring circuit signal integrity
    Heat Resistance
    Glass Transition Temperature (Tg), Thermal Decomposition Temperature (Td), Thermal Shock Resistance
    The Tg of ordinary FR-4 is about 130-150℃, and high-Tg FR-4 can reach above 170℃, which can withstand high soldering temperature
    Adapt to SMT soldering process (such as reflow soldering temperature usually 240-260℃) and equipment operating temperature rise
    Flame Retardancy
    UL94 Flame Retardant Rating
    Meet UL94 V-0 flame retardant standard, self-extinguish within 10 seconds after leaving the fire source, no dripping
    Meet electronic equipment safety specifications, reduce fire risks
    Dimensional Stability
    Coefficient of Thermal Expansion (CTE)
    The CTE in X/Y direction is small (about 13-18ppm/℃), slightly higher in Z direction, and high dimensional accuracy
    Avoid interlayer cracking or circuit offset caused by thermal expansion difference after multi-layer PCB lamination
    The performance indicators of FR-4 directly determine the application scenario of the PCB. The core indicators include mechanical properties, electrical properties, heat resistance, flame retardancy, and dimensional stability:
    Special Value of High-Tg FR-4: In high-temperature environment applications such as automotive electronics and industrial control, the Tg of ordinary FR-4 may not meet the requirements. High-Tg FR-4 improves the glass transition temperature to above 170℃ by optimizing the resin formula, which has better heat resistance and thermal aging resistance, and can maintain stable performance in harsh temperature environments.

    4. Manufacturing Process of FR-4

    The manufacturing process of FR-4 substrate is complex and requires precise control of multiple processes. The core steps include:
    1. Glass Fiber Cloth Preparation: Melt the alkali-free glass raw material and draw it into glass fiber yarn, then weave it into glass fiber cloth through a weaving machine, and finally perform surface treatment (such as coating coupling agent) to enhance the bonding force with the resin.
    2. Resin Adhesive Preparation: Mix epoxy resin, flame retardant, curing agent, accelerator, etc. in proportion, stir evenly to form a resin adhesive, and control the viscosity and solid content of the adhesive.
    3. Impregnation and Drying (Prepreg Manufacturing): Continuously pass the glass fiber cloth through the resin adhesive tank, fully impregnate it with resin, then enter the drying oven (temperature about 120-150℃) for drying, so that the resin is partially cured (Stage B) to form prepreg.
    4. Core Board Pressing: Laminate the prepreg with copper foil (usually one layer of copper foil on each side), put it into a laminator, and cure it under high temperature and pressure (Stage C). During the curing process, the resin is completely cross-linked to form a solid state, and tightly combined with the copper foil and glass fiber cloth to make a copper-clad core board.
    5. Cooling and Cutting: After the pressed core board is cooled, cut it into rectangular plates according to the specification requirements.
    6. Quality Inspection: Inspect the thickness of the core board, copper foil thickness, appearance, and performance indicators (such as Tg, dielectric constant, flame retardancy) to ensure compliance with industry standards.

    5. Application Fields of FR-4

    With balanced performance and cost advantages, FR-4 is widely used in various electronic devices and is the "universal choice" for PCB substrates:

    5.1 Consumer Electronics

    It is the largest application market for FR-4. In smartphones, tablets, laptops, TVs and other devices, FR-4 substrates are used to manufacture motherboards, power boards, interface boards, etc. For example, smartphone motherboards use high-density FR-4 substrates to achieve the integration of fine-pitch circuits and multiple components; TV power boards use the flame retardancy and heat resistance of FR-4 to ensure the safe operation of power modules.

    5.2 Automotive Electronics

    With the development of automotive intelligence and electrification, the application of FR-4 in automotive electronics is becoming increasingly widespread. It is used in in-vehicle infotainment systems, instrument panels, engine control units (ECUs), autonomous driving sensor modules, etc. Automotive electronics have higher requirements on the heat resistance and reliability of FR-4, and high-Tg, halogen-free flame-retardant FR-4 substrates are usually selected to adapt to high-temperature environments such as engine compartments and the vibration conditions of the entire vehicle.

    5.3 Industrial Control and Communication

    In industrial control equipment such as industrial computers, PLCs (Programmable Logic Controllers), and frequency converters, FR-4 substrates need to withstand complex industrial environments (such as high temperature, humidity changes, electromagnetic interference), so high-stability FR-4 is mostly used; in communication equipment (such as routers, switches, base stations), the dielectric performance of FR-4 directly affects the signal transmission quality. High-frequency communication PCBs often use FR-4 with low dielectric constant or modified FR-4 substrates.

    5.4 Medical Equipment and Instruments

    In medical equipment (such as monitors, ultrasound equipment, diagnostic instruments), FR-4 needs to meet biocompatibility and reliability requirements, and halogen-free, low-emission environmentally friendly FR-4 is selected in some scenarios; in precision instruments, the dimensional stability and high-precision characteristics of FR-4 can ensure the measurement accuracy and long-term stability of the instrument.

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