FR1 and FR4 refer to different types of substrate materials used in printed circuit boards (PCBs). Here are the key differences between FR1 and FR4 PCBs:

1. Composition:

• FR1 (Flame Retardant 1): FR1 is typically composed of paper reinforced with phenolic resin. The paper provides the substrate, and phenolic resin acts as a binding material. It is a relatively inexpensive material.

• FR4 (Flame Retardant 4): FR4 is a higher-grade substrate material composed of woven glass fabric impregnated with epoxy resin. The glass fabric provides better strength and durability compared to paper-based substrates.

2. Mechanical Properties:

• FR1: FR1 boards are generally less mechanically robust than FR4 boards. They have lower tensile strength and are more prone to warping.

• FR4: FR4 boards offer better mechanical strength and stability. The woven glass fabric reinforcement enhances their rigidity, making them suitable for more demanding applications.

3. Electrical Properties:

• FR1: FR1 has relatively lower electrical insulation properties compared to FR4. It may not be as suitable for high-frequency or high-speed applications.

• FR4: FR4 provides excellent electrical insulation properties, making it suitable for a wide range of applications, including high-frequency and high-speed circuits.

4. Thermal Properties:

• FR1: FR1 has lower thermal resistance compared to FR4. It may not dissipate heat as effectively, which can be a consideration in certain applications.

• FR4: FR4 has better thermal performance, making it more suitable for applications where heat dissipation is critical.

5. Applications:

• FR1: FR1 is often used in applications where cost is a significant consideration, and mechanical and electrical performance requirements are not as stringent. It may be suitable for simpler, less demanding circuits.

• FR4: FR4 is widely used in a variety of applications, including complex electronic circuits, high-frequency designs, and applications where mechanical strength and stability are crucial.

When choosing between FR1 and FR4, it's important to consider the specific requirements of the application, including cost constraints, mechanical strength, electrical performance, and thermal considerations. The choice of substrate material can significantly impact the overall performance and reliability of the printed circuit board.