Radio Frequency Interconnect Loss Driven by Substrate Dielectric Degradation Mechanisms
Substrate moisture absorption increases dielectric loss tangent, raising RF interconnect insertion loss and reducing long-term wireless link margins.
Stripline
Meaning
Shielded transmission structures embed a signal conductor between two continuous ground planes within a dielectric medium. Stripline circuits provide excellent electromagnetic containment because the fields are completely trapped between the conductive planes. This configuration is used for high-density routing in multilayer boards where isolation between layers is a requirement.
The signal travels through a homogeneous environment, which eliminates the dispersion found in surface-level traces.
Coupling Control
Vertical separation between the signal layer and the ground planes determines the characteristic impedance and the degree of broadside coupling. Stripline designs are less sensitive to external interference compared to open microstrip lines. The presence of the second ground plane reduces the susceptibility to noise from adjacent board layers.
Layer Stackup
Integration into a multi-layer board requires precise control over the lamination process to maintain uniform dielectric thickness. Total thickness of the stripline environment influences the overall height of the circuit board assembly. Designers balance the need for narrow traces with the constraints of the manufacturing process and the target impedance.
Performance Tradeoff
Higher manufacturing complexity and the need for more conductive layers increase the cost of these designs. While stripline offers superior shielding, it often requires smaller trace widths to achieve 50 ohms, which can increase resistive losses. Verification of the finished impedance is done using time domain reflectometry on dedicated test coupons.
These measurements confirm that the fabrication tolerances stay within the limits required for high-speed signal integrity across the entire production lot.