Antenna PCB Manufacturing Process: Step-by-Step Guide for High-Frequency RF Boards
Complete guide to antenna PCB fabrication process, covering material selection, impedance control, laser drilling, and RF testing for 5G/mmWave applications.
When it comes to PCB, we are all very familiar with the circuit boards or circuit boards that we often touch. So what is PCBA? Simply put PCBA is PCB after SMT mounting, DIP plug-in and other electronic components assembly, after testing, to form a finished product with certain functions. Xinchenger Electronics take you to understand from PCB to PCBA production process.
Process:
Verify Gerber files using CAM software (e.g., Genesis 2000)
Critical checks: Trace width/spacing (≥4mil), impedance tolerance (50Ω±10%), layer alignment (≤25μm)
Key Parameters:
Dk (Dielectric Constant): 3.38±0.05 for Rogers RO4003C
Loss Tangent (Df): <0.0027 @10GHz
High-Frequency Materials:
Laminates: Rogers RO3003 (mmWave), Taconic RF-35 (cost-sensitive)
Copper Foil: Reverse-treated copper (RTF), 1oz (35μm) standard
Standards: IPC-6018B Class 3 for RF/microwave PCBs
Steps:
Dry film lamination (15-25μm thickness)
LDI (Laser Direct Imaging) with 20μm resolution
Acid etching (copper loss <3μm)
QC: AOI (Automated Optical Inspection) with ≥99.7% defect detection
Critical Steps:
Surface Treatment: Brown oxide (0.2-0.5μm roughness)
Pressing Parameters: 180°C at 250psi for 90min (PTFE requires ramp-up)
Technology: UV laser (355nm wavelength)
Hole size: 50-100μm, positional accuracy ±10μm
Aspect ratio: ≤1:0.8 for blind vias
Process:
Gas mix: O₂/CF₄ at 10⁻² Torr vacuum
Duration: 3-5 minutes to increase surface energy (>50dyn/cm)
Methods:
Differential pairs: ±5% width/spacing tolerance
TDR (Time Domain Reflectometry) testing @20GSa/s
Laser Direct Structuring:
Nd:YAG laser (1064nm) activates additive, followed by electroless copper plating (8-12μm)
Min. line width: 75μm
Equipment: Vector Network Analyzer (VNA)
Metrics:
S11 ≤ -10dB @ operating frequency
Phase consistency: ±5° @28GHz
Standards Compliance:
Thermal cycling (-55°C to +125°C, 1000 cycles)
THB test (85°C/85%RH, 168 hours) per IPC-TM-650
Expert guide to antenna PCB fabrication nuances covering material handling, laser drilling tolerances, impedance control, and RF testing protocols.
Key Factors:
Dk Consistency: Variation ≤±0.05 across panels (e.g., Rogers RO4835™ Dk=3.48±0.05 @10GHz)
Moisture Absorption: PTFE materials require 24hr baking @125°C before lamination
CTE Matching: Z-axis CTE <70ppm/°C to prevent via cracking
Low-Skin-Effect Solutions:
Reverse-treated foil (RTF) with 0.3-0.5μm nodularity for improved adhesion
Electrodeposited copper avoidance above 18GHz due to surface roughness >2μm RMS
LDI Requirements:
5μm positional accuracy for mmWave antenna arrays
<1% CD variation on 3mil traces
Antenna-Specific Adjustments:
10% over-etch compensation for 0.2mm pitch patch antennas
Isotropic etchants (e.g., cupric chloride) preferred for uniform undercut <15%
Vacuum Lamination Protocol:
Ramp rate: 2-3°C/min for PTFE materials
Hold time: 120min @180°C under 350psi
Critical Parameters:
Prepreg resin content 50±5% for consistent dielectric thickness
Flow stop dams required within 2mm of antenna radiating edges
Acceptance Criteria:
Entrance diameter tolerance: ±5μm (for 75μm vias)
Taper angle: 80-85° for optimal plating uniformity
Post-Drilling Cleaning:
Plasma desmear: 5min O₂/N₂ plasma at 500W
Permanganate treatment for PTFE (0.5-1.0% concentration)
Finish Tpye | Insertion Loss @28GHz | Cost Factor |
ENEPIG | 0.15dB/cm | 3x |
| Immersion Ag | 0.22dB/cm | 1.5x |
OSP | 0.30dB/cm | 1x |
Gold Wire Requirements:
ENEPIG thickness: Ni≥3μm, Pd≥0.05μm, Au≥0.03μm
Surface roughness Ra<0.2μm for 25μm diameter wires
TDR Testing Protocol:
Sample rate: 1 board per panel
Acceptance: ±7% tolerance for 28GHz applications
Critical Measurements:
Dielectric thickness variation: ≤±3% within antenna zone
Copper profile: 30-35° sidewall angle
Far-Field Requirements:
Minimum distance: D=2L²/λ (L=largest antenna dimension)
Absorber performance: ≥20dB reflectivity @operating frequency
Array Antenna Criteria:
Amplitude balance: ±0.5dB between elements
Phase coherence: ±3° @beam steering angles
Conditioning Sequence:
5 cycles of -55°C/+125°C (dwell 30min)
THB testing: 85°C/85%RH for 168hrs
Vibration Testing:
10-500Hz sweep, 15G acceleration per MIL-STD-883
Antenna PCBs require rigorous testing to ensure optimal RF performance, signal integrity, and reliability. This guide covers critical inspection methods, automated testing protocols, and industry standards compliance for high-frequency PCB manufacturing.
CTE Matching: Z-axis CTE <70ppm/°C to prevent via cracking
Key Checks:
Surface Defects: Scratches, delamination, or discoloration (per IPC-A-600 Class 3)
Solder Mask Alignment: ≤25μm misalignment tolerance
Copper Plating Uniformity: ≥80% coverage in via holes
Verify Gerber files vs. physical PCB (CAM350 comparison)
Confirm impedance control parameters (TDR simulation vs. actual)
Parameters:
Test Voltage: 50-250V DC
Resistance Threshold: ≤10Ω for continuity, ≥100MΩ for isolation
Speed: 5,000+ test points/hour (high-volume production)
Critical for RF Antennas:
Tolerance: ±7% for ≤6GHz, ±5% for mmWave (28GHz+)
Sampling Rate: 1 board per panel (100% testing for prototypes)
Key Metrics:
Return Loss (S11): ≤-10dB at operating frequency
Insertion Loss (S21): ≤0.3dB/cm @28GHz
Phase Consistency: ±5° between antenna elements
Setup Requirements:
Far-Field Distance: 𝐷=2𝐿2𝜆D=λ2L2 (L = antenna size)
Absorber Performance: ≥20dB reflectivity reduction
Measured Data:
Gain: ±0.5dB variation from design
Beamwidth: ±2° tolerance
Conditions:
Temperature Range: -55°C to +125°C
Cycles: 500-1,000 (per IPC-6018B)
Failure Criteria: Cracks in vias or solder joints
Standards: 85°C/85%RH for 168 hours
Post-Test Checks:
Insulation resistance ≥100MΩ
No dendritic growth (electromigration)
Minimum Resolution: 10μm (for microvia inspection)
Common Detections:
Open Circuits: Trace width <50% of design
Short Circuits: Conductive debris ≥25μm
Laser Profilometry: Measures solder paste thickness (±5μm accuracy)
Co-Planarity Check: ≤30μm component lead deviation
Sample Preparation:
Epoxy mounting → Precision polishing (0.05μm finish)
Critical Measurements:
Plating Thickness: ≥25μm in vias (IPC-6012 Class 3)
Interlayer Registration: ≤20μm misalignment
Standard | Requirement | Test Method |
IPC-6018B | RF/Microwave PCB performance | TDR, VNA |
MIL-PRF-31032 | Military-grade reliability | Thermal shock, vibration |
IEC 61189-3 | Material property verification | Dk/Df measurement |
