Microstrip line materials — common dielectric choice In a typical microstrip line used for RF printed-circuit designs, which dielectric material is most commonly used?

Introduction / Context:
Microstrip lines are fabricated on dielectric substrates with a metal trace on top and a ground plane beneath. The dielectric choice impacts loss tangent, dielectric constant, manufacturability, and cost. In commercial and consumer RF PCBs, the most common dielectrics are plastics or plastic-based laminates (e.g., FR-4 epoxy glass, PTFE-based composites).

Given Data / Assumptions:

• Focus on common, mass-produced RF PCB technology.
• Option set is generic rather than brand-specific.

Concept / Approach:
Silicon is a semiconductor wafer used in ICs, not a typical PCB dielectric. Rubber is lossy and mechanically unsuitable. Bakelite is an old thermoset historically used but uncommon in modern RF PCB microstrip. By contrast, plastics—especially epoxy-glass (FR-4) and PTFE-based materials—dominate. High-performance RF uses PTFE or low-loss plastics; cost-sensitive designs use FR-4. Therefore, among the provided choices, “plastic” is the correct generalized answer.

Step-by-Step Solution:

Verification / Alternative check:
Fabrication standards and vendor catalogs list FR-4 and PTFE composites (both plastic-derived) as ubiquitous microstrip substrates across frequencies from HF to microwave.

Why Other Options Are Wrong:

• Silicon: used for ICs and MMICs, not for ordinary microstrip PCBs.
• Rubber: high loss, poor dimensional stability.
• Bakelite: obsolete for precision RF, inferior electrical properties compared to modern plastics.

Common Pitfalls:
Confusing MMIC-on-silicon with PCB microstrip; assuming any insulator is suitable regardless of loss tangent and mechanical constraints.

Final Answer:
plastic