Multi-substrate is a high-performance, high-speed system. For higher frequencies, the rise time of the signal is reduced, so that the signal reflection and the control of the line length become crucial. In a multi-substrate system, the requirements for controlled impedance performance of electronic components are very strict and the design must meet the above requirements. The factors that determine the impedance are the dielectric constant of the substrate and the prepreg, the spacing of the conductors on the same level, the thickness of the interlayer dielectric, and the thickness of the copper conductor. In high-speed applications, the lamination sequence of the conductors in the multi-substrate and the connection sequence of the signal network are also crucial. Dielectric constant: The dielectric constant of the substrate material is an important factor in determining the impedance, propagation delay, and capacitance. The dielectric constant of the substrate and the prepreg using epoxy glass can be controlled by changing the percentage of the resin content.
The dielectric constant of epoxy resin is 3.45, and the dielectric constant of glass is 6.2. By controlling the percentage of these materials, the dielectric constant of epoxy glass may reach 4.2 - 5.3. The thickness of the substrate is a good indication for determining and controlling the dielectric constant.
Prepregs with relatively low dielectric constants are suitable for use in RF and microwave circuits. In RF and microwave frequencies, lower dielectric constants cause lower signal delays. In the substrate, low loss factors can minimize electrical losses.
Prepreg ROR 4403 is a new type of material produced by ROGERS. This material is compatible with other substrates used in standard multi-substrate (FR-4 material) structures (for example, RO 4003 or RO 4350 for microwave plates).