Perfect and Great FR4 PCB board Manufacturing with high quality made in Shenzhen China
FR4 is a commonly used printed circuit board (PCB) substrate material, mainly composed of fiberglass cloth and epoxy resin. Fiberglass cloth provides excellent mechanical strength, allowing PCBs to withstand certain external forces without easily deforming or damaging; Epoxy resin plays a role in bonding glass fibers and has good electrical insulation performance and chemical stability.
PCB or Printed Circuit Board is the traditional name for the bare board of which we produce with the layout data and which will be used to mount the components on.
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. Components are generally soldered onto the PCB to both electrically connect and mechanically fasten them to it.
1ă What is FR4 PCB? ââDefinition and core positioning
FR4 PCB refers to a printed circuit board (PCB) with FR4 substrate as the core, where "FR" stands for "Flame Retainer" and "4" represents the fourth generation flame retardant substrate standard. It is currently the most widely used and mature universal PCB in the world. It is processed by etching, drilling, solder mask, screen printing and other processes using FR4 copper-clad laminates (fiberglass cloth+epoxy resin+copper foil), and has three core functions: electrical insulation, mechanical support, and signal transmission. It is the "skeleton and nerve" of the vast majority of electronic devices. â
Compared with special-purpose PCBs such as aluminum substrates, Rogers high-frequency boards, and ceramic substrates, the core advantages of FR4 PCBs are strong versatility, controllable cost, mature technology, and coverage of low, medium, and high difficulty products. They occupy more than 70% of the global PCB market share and can be regarded as the "cornerstone of the electronics industry". â
2ă Core Structure and Materials of FR4 PCB
1. Core substrate: FR4 copper-clad laminate (determines basic performance)
The core of FR4 substrate is a composite structure of "fiberglass cloth+epoxy resin", which can be divided into ordinary type, high Tg type, halogen-free type, etc. according to performance. Key parameters include:
Tg value (glass transition temperature): ordinary FR4 Tg â 130~140 â, high Tg FR4 Tg â„ 170 â (high temperature resistance, aging resistance, suitable for welding intensive/high temperature conditions); â
Flame retardant rating: UL94 V-0 (mandatory standard, self extinguishing in case of fire, non spreading); â
Dielectric constant (Δ r): 4.2~4.8 (1MHz), meeting the requirements of conventional signal transmission; â
Thermal conductivity: 0.3~0.5 W/(m · K) (with average heat dissipation, suitable for low to medium power consumption scenarios). â
2. Copper foil layer (signal transmission carrier)
Materials: electrolytic copper foil (conventional choice, low cost), rolled copper foil (good flexibility, suitable for flexible FR4 or high-frequency scenarios); â
Thickness: Conventional 1oz (35 ÎŒ m), 2oz (70 ÎŒ m). For high current scenarios, 3-10oz thick copper can be used, and ultra-thin copper foil (0.5oz) can be used for high-density circuits. â
3. Solder mask (protection and insulation)
Material: Epoxy resin solder mask ink (mainly green, supporting customized colors such as black, white, blue, etc.); â
Function: To prevent copper foil oxidation, avoid solder joint short circuits, protect circuits from mechanical damage, and some solder mask inks support chemical cleaning resistance and high hardness requirements. â
4. Silk screen layer (identification and maintenance)
Content: Component numbers (R1, C2), polarity markings, manufacturer logo, version number; â
Function: It is convenient for production assembly, post maintenance and traceability. The ink needs to have the characteristics of friction resistance and not easy to fall off. â
3ă Core Performance and Advantages of FR4 PCB
1. Highly versatile and adaptable to a wide range of scenarios
Balanced electrical performance: low dielectric loss (suitable for conventional signals below 1GHz), high insulation strength (withstand voltage â„ 2kV), and current carrying capacity to meet the needs of the vast majority of electronic devices; â
Stable mechanical performance: resistant to bending and impact, precise dimensional tolerance control (within ± 0.1mm), suitable for automated assembly; â
Good process compatibility: Supports mainstream processes such as SMT surface mount, DIP plug-in, BGA/QFN precision soldering, through-hole electroplating, impedance control, etc., and can achieve multi-layer board processing from single-layer, double-layer to tens of layers. â
2. Cost and supply chain advantages
Popularization of raw materials: FR4 copper-clad laminates have sufficient production capacity and numerous global suppliers (such as Shengyi, Jiantao, Rogers, etc.), with procurement costs much lower than special substrates; â
Mature processing: More than 90% of PCB factories in the industry have FR4 processing capabilities, high mass production efficiency, stable yield (conventional multi-layer board yield â„ 98%), and can adapt to both small and large orders. â
3. Environmental Protection and Compliance
Conventional FR4 meets RoHS standards (lead-free, cadmium free), while halogen-free FR4 (without brominated flame retardants) can meet stricter environmental requirements such as EU REACH and US FDA, and is suitable for special fields such as healthcare and automotive. â
4ă Main classifications of FR4 PCB
1. Divided by layers (the most commonly used classification method)
Single Sided: With copper foil wiring on only one side, it has a simple structure and the lowest cost, making it suitable for simple circuits such as remote controls, toys, and power adapters; â
Double Sided: Both sides have lines, and the upper and lower layers are connected through vias, making it the mainstream choice for consumer electronics (such as mobile phone chargers, routers, and small home appliance control boards); â
Multi Layer board: 3 or more layers, including inner layer circuits, optimized for high-density and complex circuits (such as mobile phone motherboards, computer graphics cards, industrial controllers) through blind holes and buried holes, suitable for 20-40 layers in high-end scenarios. â
2. Divided by performance level
Ordinary FR4: Tg=130~140 â, suitable for low to medium power consumption and conventional temperature environments (such as consumer electronics and general industrial control); â
High Tg FR4: Tg â„ 170 â, high temperature resistant, anti-aging, suitable for high-temperature welding (such as automotive electronics, power modules), long-term operation equipment; â
Zero halogen FR4: flame retardant without bromine, high environmental protection level, suitable for medical, maternal and child electronics, and EU export products; â
High frequency FR4: Optimize dielectric constant stability (Δ r=3.8~4.2), reduce signal attenuation, suitable for network devices such as routers and switches. â
Rigid FR4 PCB (mainstream): high hardness, strong mechanical support, adopted by the vast majority of electronic devices; â
Flexible FR4 PCB (with FR4 as the base material for flexible copper-clad laminates): It combines the electrical performance and flexibility of rigid FR4, making it suitable for folding and bending scenarios such as mobile phone cables and wearable devices; â
Rigid flexible combination FR4 PCB: Integrating rigid and flexible areas, suitable for complex installation spaces such as drones and medical equipment. â
5ă Typical application scenarios of FR4 PCB
FR4 PCB covers almost all fields of the electronics industry and is the "ubiquitous cornerstone of electronics":
Consumer electronics: mobile phones, computers, tablets, routers, televisions, headphones, power banks, small appliances (air conditioners, refrigerators, washing machine control boards); â
Industrial electronics: PLC controllers, frequency converters, sensors, industrial power supplies, instruments and meters; â
Automotive electronics: in car navigation, central control screen, headlight control board, OBD equipment (for conventional temperature scenarios, high Tg FR4 or special automotive substrates are commonly used in high-temperature core areas); â
Medical electronics: blood pressure monitor, blood glucose meter, thermometer, ordinary monitor (non implantable, low to medium power consumption scenario, requiring halogen-free/high reliability FR4); â
Communication equipment: base station antenna, optical module, switch, router core board (high-frequency FR4 or mixed high-frequency substrate); â
Other: toys, security equipment (cameras, alarms), IoT modules, LED driver boards (low to medium power). â
6ă Limitations of FR4 PCB (applicable boundaries)
Weak heat dissipation capability: The thermal conductivity is only 0.3~0.5 W/(m · K), which is not suitable for high-power and high heat generating scenarios (such as LED headlights, charging pile power boards, which require the use of aluminum or copper substrates); â
High frequency performance is limited: the dielectric constant varies greatly with frequency, and the signal attenuation is significant. It is not suitable for high-frequency signals above 5GHz or high-speed serial buses (such as PCIe 4.0/5.0), and high-frequency substrates such as Rogers and PTFE need to be selected; â
Poor adaptation to extreme environments: In high temperature (>150 â), high humidity, and strong corrosive environments, performance is prone to degradation, and ceramic substrates and polyimide substrates need to be selected. â
7ă Key Points for FR4 PCB Selection (Practical Guide)
Simple circuit (up to 100 components): single-layer/double-layer board; â
Complex circuits (multi chip, high-density): 4-8 layer boards; â
High end devices (mobile phones, servers): multi-layer boards with more than 10 layers. â
Select Tg value according to temperature scenario:
Conventional environment (-20~85 â): ordinary FR4 (Tg=130~140 â); â
High temperature environment (>85 â), high temperature soldering (such as lead-free reflow soldering peak at 260 â): high Tg FR4 (Tg â„ 170 â). â
Select copper foil thickness based on current:
Conventional signal: 1oz copper foil; â
High current (>5A): 2-5 oz thick copper; â
Ultra high current (>10A): 5-10oz thick copper+widened circuit. â
Select type according to environmental requirements:
Ordinary export: RoHS compliant FR4; â
EU/Medical: Halogen free FR4. â
Select substrate according to signal frequency:
Conventional signal (regular FR4; â
High frequency signal (1-5GHz): High frequency FR4; â
5GHz: Select high-frequency dedicated substrate (non FR4). â
Leading China PCB manufacturer, Hitech Circuits specializes in various PCBs â prototypes, FR4, Double-sided, Aluminum, RF, Ceramic, High-Fre