1. Material Selection and Validation

• Critical Points:
  ✅ Use specialized high-frequency laminates (e.g., Rogers 4350B, Taconic) to ensure stable dielectric constant (Dk) and low loss tangent (Df).
  ✅ Verify material certificates (COC) to avoid batch-to-batch variations that could affect electrical performance.
  ⚠️ Note: Do not mix with standard FR-4 materials, as this may degrade signal integrity.

2. Pattern Transfer and Line Width Control

• Critical Points:
  ✅ Implement Laser Direct Imaging (LDI) technology to achieve precision in fine-line circuitry (minimum line width/spacing down to 0.1mm/0.1mm).
  ✅ Strictly control impedance matching, with validation through TDR testing (±5% tolerance).
  ⚠️ Note: Maintain stable temperature and humidity to prevent pattern distortion or misalignment.

3. Drilling and Hole Metallization

• Critical Points:
  ✅ For high-frequency boards, laser-drilled blind and buried vias are preferred. Control via wall roughness to ≤20μm to minimize signal loss.
  ✅ Apply high-aspect-ratio plating for uniform copper thickness in vias.
  ⚠️ Note: Prevent resin residue by enhancing desmearing and plasma cleaning processes.

4. Lamination and Dimensional Stability

• Critical Points:
  ✅ Use low-temperature, low-pressure lamination to protect the dielectric properties of high-frequency materials.
  ✅ Perform post-lamination baking to relieve internal stress and control dimensional shrinkage to <0.02%.
  ⚠️ Note: For hybrid structures (e.g., FR-4 combined with high-frequency materials), match the coefficient of thermal expansion (CTE).

5. Surface Finish and Protection

• Critical Points:
  ✅ Prefer ENIG (Electroless Nickel Immersion Gold) or immersion silver for high-frequency signal areas to reduce surface resistance.
  ✅ Apply hard gold plating (thickness ≥30μ”) on gold finger areas to ensure wear resistance during insertion/removal.
  ⚠️ Note: Avoid over-polishing to prevent damage to high-frequency traces.

6. Electrical Testing and Reliability Validation

• Critical Points:
  ✅ Perform 100% continuity testing using flying probe, supplemented by S-parameter testing via Vector Network Analyzer (VNA).
  ✅ Conduct thermal cycling (-55℃ to 150℃) and damp heat tests to validate long-term reliability.
  ⚠️ Note: Calibrate test fixtures to avoid introducing parasitic effects.

7. Documentation and Traceability

• Critical Points:
  ✅ Record key process parameters (e.g., lamination temperature, plating current density) for full-process traceability.
  ✅ Provide material certifications, impedance test reports, and reliability test data packages.
  ⚠️ Note: Comply with industry standards such as ISO 9001 and IPC-6012DA to enhance customer trust.