FAKRA Connector Substrate Material for High-Frequency Loss

Overview of Technical Issues:

The substrate material in the FAKRA connector produces a harmful effect by absorbing high-frequency electromagnetic energy through dielectric losses, causing excessive signal attenuation and insertion loss that degrades transmission performance; the goal is to optimize substrate material selection to minimize high-frequency losses while maintaining mechanical support and insulation functions across the required frequency spectrum.

Solution directions generated for this problem

Problem Direction 1 :

ImproveSubstrate dielectric loss tangent
VS
ConstraintMaterial mechanical strength

Inspiration 1 : Cross-domain reference

Application Principle: #1 Segmentation
Cross-domain applicability Assess applicability
Animal leather fiber bundles, yarns, core-spun yarns and products with nanoscale branching
Innovative Solution Refine solution

Functionally-zoned hybrid substrate with selective low-loss inserts for FAKRA connectors

Divide substrate into load-bearing and signal zones with tailored materials
How to solve :
  • Partition substrate into outer mounting ring (standard FR-4, εr 3.8, tan δ 0.020, tensile strength ≥350 MPa) for mechanical loads and inner signal channel (PTFE composite, εr 2.3, tan δ 0.004, 0.8 mm width) for RF transmission, bonded via low-loss epoxy (tan δ <0.008)
  • Machine FR-4 ring with precision CNC (tolerance ±0.05 mm) to create central cavity, insert pre-molded PTFE segment, cure bond at 150°C for 2 hours under 0.3 MPa pressure, ensuring interface gap <20 μm
  • Validate via pull-off testing (bond strength ≥15 MPa), network analyzer sweep 1–6 GHz (insertion loss <0.75 dB), and flexural load test (≥80 N without delamination)
Expected Effect : Insertion loss 0.7 dB at 6 GHz; tensile strength retained at 340 MPa; cost +40% vs full-PTFE
Risk Control :
  • interface delamination under thermal cycling
  • impedance mismatch at material boundary
  • PTFE insert positioning accuracy

Problem Direction 2 :

ImproveSubstrate dielectric loss tangent
VS
ConstraintImpedance matching stability

Inspiration 1 : Cross-domain reference

Application Principle: #35 Parameter changes
Cross-domain applicability Assess applicability
Glass Plate and Its Manufacturing Method
Innovative Solution Refine solution

Graded dielectric constant substrate with thermal gradient processing

Graded εr substrate maintains impedance while cutting loss
How to solve :
  • Formulate PTFE composite with variable ceramic filler concentration: 25% alumina near conductor zones (εr 3.5, tan δ 0.006), tapering to 5% in bulk regions (εr 2.3, tan δ 0.004) via controlled dispersion molding
  • Apply thermal gradient annealing at 320–340°C with 15°C/cm spatial gradient for 2 hours, then cool at controlled 50°C/min rate to lock in graded microstructure per patent CN113677637B methodology
  • Machine substrate with impedance-verified test coupons every 50 units: TDR measurement confirms 50Ω ±2Ω across all interfaces, VNA sweep verifies tan δ ≤0.005 at 6 GHz
Expected Effect : Insertion loss ≤0.75 dB, impedance deviation <4%, tan δ 0.004–0.006
Risk Control :
  • filler gradient uniformity deviation ±3%
  • thermal profile control precision ±5°C
  • interface εr transition sharpness variation

Problem Direction 3 :

ImproveSubstrate dielectric loss tangent
VS
ConstraintManufacturing cost and complexity

Inspiration 1 : Cross-domain reference

Application Principle: #27 Cheap short-living objects
Cross-domain applicability Assess applicability
Phosphorescent materials
Innovative Solution Refine solution

Selective PTFE thin-film coating on signal-critical substrate zones

Apply cost-effective substrate with targeted low-loss surface treatment
How to solve :
  • Retain standard FR-4 substrate (tan δ 0.02, cost baseline) as bulk material for mechanical support and ease of processing
  • Deposit 15–30 μm PTFE thin film (tan δ <0.005) via spray coating or dip coating only on signal trace regions where RF field intensity exceeds 70% of peak value, covering <25% of total substrate area
  • Control film thickness to ±3 μm using laser profilometry inspection (sampling 5 points/cm²), cure at 280–320°C for 15–20 min, verify adhesion strength ≥8 N/cm via peel test before conductor lamination
Expected Effect : Insertion loss reduced to 0.85–1.0 dB; material cost increase <40% vs full PTFE replacement; standard molding equipment compatible
Risk Control :
  • film thickness uniformity deviation
  • adhesion failure at substrate-film interface
  • PTFE coating process temperature control
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