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The indicators of FR-4 substrate include: glass transition temperature (Tg), thermal decomposition temperature (Td) of the substrate, loss factor (Df), dielectric constant (Dk), relative leakage tracking index (CTI), coefficient of thermal expansion (CTE), water absorption rate, adhesion characteristics of the material, etc.
Tg value refers to the temperature point at which a material transitions from a relatively rigid "glass" state to a deformable state. As long as the thermal decomposition temperature (Td) is not reached, this thermodynamic change is reversible, and when cooled below the Tg value, the material can return to a rigid state. When the thermal decomposition temperature is exceeded, FR-4 will undergo decomposition failure.
The industry usually divides FR-4 board into three levels based on Tg value: high, medium, and low
Low Tg FR-4: Tg value around 135 ℃;
Medium Tg FR-4: Tg value is around 150 ℃;
High Tg FR-4: Tg value is around 170 ℃.
If there are multiple pressing cycles, multiple layers of PCB, high soldering temperature (≥ 230 ℃), high working temperature (over 100 ℃), and high soldering thermal stress (such as wave soldering) during PCB processing, high Tg boards should be selected.
The dielectric constant and dielectric loss angle are two fundamental properties of a medium, which vary with frequency. The larger the loss factor (Df), the greater the attenuation. The dielectric constant (Dk) has a greater impact on impedance.
FR-4 can be divided into:
Ordinary loss board: Df ≥ 0.02
Medium loss board: 0.01 ≤ Df<0.02
Low loss board: 0.005 ≤ Df<0.01
Ultra low loss board: Df ＜ 0.005
The Comparative Tracking Index is used to measure the electrical breakdown performance of insulation materials. Leakage marks occur on the surface of insulating materials. Due to the presence of dielectric losses, the dielectric heats up, causing decomposition and carbonization of the dielectric, ultimately extending to the electrode and causing a short circuit.
The CTI value of the material is positively correlated with its insulation performance. A high CTI value means a lower required creepage distance, and the distance between two conductors will be closer.
The indicators of FR-4 substrate include: glass transition temperature (Tg), thermal decomposition temperature (Td) of the substrate, loss factor (Df), dielectric constant (Dk), relative leakage tracking index (CTI), coefficient of thermal expansion (CTE), water absorption rate, adhesion characteristics of the material, etc.
Tg value refers to the temperature point at which a material transitions from a relatively rigid "glass" state to a deformable state. As long as the thermal decomposition temperature (Td) is not reached, this thermodynamic change is reversible, and when cooled below the Tg value, the material can return to a rigid state. When the thermal decomposition temperature is exceeded, FR-4 will undergo decomposition failure.
The industry usually divides FR-4 board into three levels based on Tg value: high, medium, and low
Low Tg FR-4: Tg value around 135 ℃;
Medium Tg FR-4: Tg value is around 150 ℃;
High Tg FR-4: Tg value is around 170 ℃.
If there are multiple pressing cycles, multiple layers of PCB, high soldering temperature (≥ 230 ℃), high working temperature (over 100 ℃), and high soldering thermal stress (such as wave soldering) during PCB processing, high Tg boards should be selected.
The dielectric constant and dielectric loss angle are two fundamental properties of a medium, which vary with frequency. The larger the loss factor (Df), the greater the attenuation. The dielectric constant (Dk) has a greater impact on impedance.
FR-4 can be divided into:
Ordinary loss board: Df ≥ 0.02
Medium loss board: 0.01 ≤ Df<0.02
Low loss board: 0.005 ≤ Df<0.01
Ultra low loss board: Df ＜ 0.005
The Comparative Tracking Index is used to measure the electrical breakdown performance of insulation materials. Leakage marks occur on the surface of insulating materials. Due to the presence of dielectric losses, the dielectric heats up, causing decomposition and carbonization of the dielectric, ultimately extending to the electrode and causing a short circuit.
The CTI value of the material is positively correlated with its insulation performance. A high CTI value means a lower required creepage distance, and the distance between two conductors will be closer.
