What are the common material used for printed circuit board (PCB)?

One of the common materials in printed circuit board (PCB) manufacturing is Copper-clad laminates (CCLs) which are manufactured by impregnating resin with reinforcing materials like wood pulp paper or fiberglass cloth, then laminating copper foil on one or both sides and pressing it through a hot-pressing process. The CCLs serve three critical functions: conductivity, insulation, and structural support, making them an indispensable component in electronic devices.

Copper-clad laminates (CCLs) are classified into rigid and flexible types by mechanical property and by reinforcement material into glass fiber cloth-based, paper-based, and composite-based variants. Glass fiber cloth-based CCLs, reinforced with glass fiber fabric, feature exceptional mechanical strength and electrical performance, making them the most widely used type. Paper-based CCLs, utilizing paper as reinforcement, offer lower costs but relatively inferior mechanical and electrical properties, typically employed in low-end electronic devices. Composite-based CCLs integrate multiple reinforcement materials like glass fiber and paper to achieve a balance between cost and performance.

More than 60% of the copper-clad laminates currently use FR-4 sheet as the reinforcement material. Typically, FR-4 sheet uses alkali-free glass fiber cloth to enhance mechanical strength. The cloth is impregnated with epoxy resin, exhibiting excellent adhesion, electrical insulation, and chemical stability.

The resin system mainly consists of low-bromine epoxy resin, high-bromine epoxy resin, isocyanate-modified epoxy resin, and phenolic epoxy resin. By adjusting the ratio of these resins, different glass transition temperatures (Tg values) can be achieved.

To achieve flame retardant performance, it will add brominated flame retardants like tributyl bromophenol A (TBBPA) or halogen-free flame retardants like phosphorus-based and nitrogen-based compounds.

The copper used include electrolytic copper foil or rolled copper foil, which serves as the core material of the conductive metal layer on the surface of copper-clad laminates.

RDS Composite provides high quality FR4 CCLs in thicknesses of 12μm, 18μm, or 35μm, with a core board thickness ranging from 0.2mm to 3.2mm.

What are the features of FR4 CCL?

Mechanical properties: High rigidity, excellent bending and impact resistance, with good bending and tensile strength, capable of withstanding the soldering pressure and machining stress during PCB assembly.

Electrical performance: The dielectric constant remains stable at 4.2-4.8 (1GHz), with low dielectric loss and high insulation resistance, effectively reducing signal attenuation and interference during high-frequency transmission.

Thermal resistance: Standard FR-4 has a glass transition temperature (Tg) of 130-150°C, while high-Tg FR-4 exceeds 170°C, enabling it to withstand high welding temperatures and demonstrating excellent thermal shock resistance.

Flame retardancy: Meets UL94 V-0 standard, self-extinguishes within 10 seconds after being removed from a fire source, and does not drip, ensuring the safety of electronic devices.

Dimension stability: The thermal expansion coefficient is relatively low in X/Y directions (approximately 13-18ppm/℃) but slightly higher in the Z direction, effectively preventing inter layer cracking or circuit misalignment caused by thermal expansion differences during multi layer PCB lamination.

FR-4 copper-clad laminate, with its cost-effectiveness, stable insulation, high mechanical strength, and excellent flame retardancy, is the most widely used rigid PCB substrate today. It is applied in core sectors including consumer electronics, automotive electronics, industrial control, and communication equipment.