The insulating layer needs to have good heat resistance and be able to remain stable in the high-temperature environment generated when the PCB is in operation.
Chemical Resistance: The insulation layer should be able to resist common chemicals such as solvents, acids and alkalis to prevent damage to the circuit by environmental factors.
Coefficient of Thermal Expansion (CTE): The coefficient of thermal expansion of the insulating layer should match the other materials in the PCB to minimize deformation caused by thermal stress.
Flame Retardant Properties: The insulating layer material should have certain flame retardant properties to slow down the spread of flame and improve the safety of the circuit board.
Dielectric Properties: The dielectric constant (Dk) and dissipation factor (Df) of the insulating layer affect signal transmission speed and loss, especially in high frequency applications.
Environmental Adaptability: The insulating layer should be able to adapt to a variety of environmental conditions such as humidity, temperature variations, and UV exposure.

Role:
Prevents Electrical Short Circuits: Insulation isolates different conductive layers to prevent accidental short circuits between circuits and ensure circuit reliability.
Provide Mechanical Protection: The insulation layer protects the wires from physical damage and increases the durability of the PCB.
Resists Environmental Effects: The insulation layer prevents moisture, dust and other contaminants from attacking the circuit, increasing the durability of the PCB.
Increases Circuit Reliability: Good insulation helps reduce the failure rate of circuits and extends product life.
Supports High-density Wiring: In High Density Interconnect (HDI) technology, the thinning of the insulation helps to achieve finer wiring and higher component density.
Assists in Thermal Management: Insulation is involved to some extent in the thermal management of PCBs, helping to dissipate heat generated by electronic components.
Provides Aesthetic Appearance: Insulation is usually covered with colors, such as green, blue, etc., which not only provide protection but also provide an aesthetic appearance.
Facilitates Production and Maintenance: Insulation can be printed with markings, numbers, or other information to aid in proper component installation and testing during manufacturing and repair.
The insulation layer plays a vital role in PCB design and manufacturing, which not only relates to the electrical performance of the circuit, but also directly affects the reliability and durability of the product. Choosing the right insulation material and designing a proper insulation structure are crucial to ensure the performance and quality of the PCB.