The Isola FR408HR is a high-performance laminate and prepreg material designed for advanced circuitry applications, particularly where high speed and high frequency are critical. The Dielectric Constant (DK) and Dissipation Factor (DF) values for FR408HR vary depending on the frequency, which is crucial for designing PCB stackups that need to maintain signal integrity across a range of frequencies. For instance, at 100 MHz, the DK values range from 3.30 to 3.82, and the DF values are as low as 0.0068, which increases slightly with frequency, reaching up to 0.011 at 10 GHz for different configurations of the material .

When building a PCB stackup using FR408HR, it's essential to consider these variations in DK and DF across different frequencies to optimize the PCB performance for your specific application. Here are some key considerations:

• Choose the appropriate resin content and thickness based on the desired electrical properties and mechanical stability.
• Account for the increase in DF with frequency, which can affect signal loss, especially in high-speed applications.
• Ensure compatibility with standard PCB manufacturing processes, as FR408HR is designed to be processed similarly to conventional FR-4 materials.

Overall, FR408HR's range of DK and DF values provides flexibility in designing PCBs that require precise control over electrical properties at various frequencies. This makes it an excellent choice for applications such as high-speed digital, RF and microwave, and high reliability aerospace and defense projects. When designing your stackup, always ensure that the specific material configuration (resin content and thickness) matches the electrical performance requirements of your application .