1800nH Broadband Inductors Heavy Duty RF Choke Coil 10MHz - 20GHz

Product Overview

The HALT60008 is a broadband conical inductor optimized for high-current bias tee DC injection networks. It provides 1800 nH (1.8 µH) of nominal inductance covering 10 MHz to 20 GHz, wound with 0.08 mm fine copper wire and rated for 500 mA continuous DC bias current. Operating temperature range is -55°C to +125°C.

Technical Specifications

Bias Tee Circuit Design with 500 mA DC Handling

In a bias tee, the choke inductor must simultaneously conduct DC bias current to the active device and present high RF impedance across the signal bandwidth. The HALT60008 is specifically engineered for applications where both demands are substantial—500 mA of DC current combined with broadband RF isolation from 10 MHz to 20 GHz.

Circuit Topology

• RF Through-Path: 50-Ω microstrip or coplanar waveguide connecting Port 1 to Port 2. The narrow apex end of the inductor is soldered directly to this trace at the tee junction.
• DC Bias Injection: The wide base end connects to a DC feed pad. A broadband bypass capacitor network (100 pF parallel with 10 nF ceramic) shunts residual RF to the ground plane.
• DC Path Characteristics: At the rated 500 mA, the winding’s DC resistance of approximately 1.8 Ω produces a voltage drop of ~0.9 V. The air-core construction ensures inductance remains constant regardless of DC current level—there is no magnetic saturation effect.
• RF Isolation: The 1800 nH inductance generates >2.0 kΩ of impedance across the rated band, equating to >66 dB of RF-to-DC isolation referenced to 50 Ω.

Thermal Analysis for 500 mA Continuous Operation

Running 500 mA through an 80 µm conductor requires verified thermal design. The HALT60008 is engineered for this operating point through the following measures:

• Conductor Material: Oxygen-free high-conductivity copper (OFHC, 99.99% Cu) minimizes DC resistance. At 25°C ambient, typical DCR is approximately 1.8 Ω, yielding I²R dissipation of roughly 450 mW at rated current.
• Temperature Rise Control: The specified ΔT of ≤15°C prevents the positive temperature coefficient feedback loop where higher temperature increases copper resistivity (+0.39%/°C), which increases dissipation further.
• Cooling Mechanism: The exposed air-core construction radiates and convects naturally. A 0.5 mm air gap around the coil body supports rated operation. No potting compound traps heat internally.
• Insulation Margin: The polyimide enamel is rated for 200°C continuous operation. At the worst-case condition of +125°C ambient with 15°C self-heating (140°C junction), the insulation operates with 60°C of headroom.
• Zero Core Loss: Unlike ferrite chokes that dissipate additional energy through hysteresis and eddy currents, the air-core HALT60008 has no magnetic loss component. All dissipation is from predictable copper I²R loss alone.

Step-by-Step Assembly Procedure

Step 1 — Physical Alignment & Orientation

Position the small end (cone tip) of the inductor pointing downward, perpendicular (≈90°) to the RF transmission microstrip line. Angular deviation introduces asymmetric field coupling that degrades S11 return loss above 15 GHz.

Step 2 — Apex Lead Connection

Solder the apex flying lead directly to the 50-Ω microstrip trace. Trim the lead between solder fillet and first winding turn to ≤0.3 mm. At 20 GHz, even a 0.5 mm excess lead adds approximately 0.3 nH of series parasitic inductance, which measurably shifts the input match.

Step 3 — Base Lead to DC Bias Node

Solder the wide base lead to the DC bias input pad. Place 100 pF and 10 nF ceramic bypass capacitors within 1 mm of this pad to minimize the inductive loop between the choke and the RF ground reference.

Step 4 — Epoxy Stabilization

Apply a single micro-dot (~0.3 mm diameter) of non-conductive, low-outgassing epoxy (Epotek H70E or H65 recommended) to the side of the winding where it contacts the substrate. This step is mandatory: without epoxy fixing, the air-core coil can vibrate under acoustic or mechanical excitation, modulating turn spacing (microphonic effect) and introducing phase noise. Do not fully encapsulate the coil—excess dielectric adds unwanted shunt capacitance.

Step 5 — Soldering Thermal Profile

Controlled micro-soldering tip temperature: 280–320°C. Dwell time: ≤3 seconds per joint. The 0.08 mm wire tolerates slightly longer heating than ultra-fine 0.05 mm variants. Fully compatible with lead-free SAC305 solder and high-melting-point eutectic gold-tin (AuSn) or lead-tin (PbSn) solder alloys.

Environmental Reliability

• Temperature Cycling: No CTE mismatch. The copper winding is the sole structural material. There is no ferrite-to-copper or ceramic-to-copper interface to crack under thermal cycling between -55°C and +125°C.
• Vibration Resistance: With epoxy dot-fixing applied, the assembly passes MIL-STD-202 Method 204 (vibration) and Method 213 (mechanical shock). The air-core structure’s low mass keeps mechanical resonance above typical excitation spectra.
• Storage: 12-month rated shelf life when stored at 20–25°C and 40–60% RH in anti-static waffle packs. Gold/tin-plated leads resist oxidation during storage.

Application Scenarios by Market

Frequently Asked Questions

Q: Can the HALT60008 handle intermittent currents above 500 mA?
A: The 500 mA rating is for continuous DC operation at +125°C ambient. Intermittent higher currents are possible provided the time-averaged dissipation stays within the ΔT ≤ 15°C limit. For sustained operation above 500 mA, contact Hoan about custom wire-gauge conical coil options.

Q: Does Hoan provide 3D models for mechanical integration?
A: Yes. Full 3D STEP models and high-frequency S-parameter simulation data (.s2p) from 10 MHz to 20 GHz are available to support CAD integration and RF circuit design. A parameterized HFSS 3D EM model can also be provided for PCB co-simulation.

Q: What are the storage requirements to prevent lead tarnish?
A: The HALT60008 is shipped in standard anti-static waffle packs. Store at 20–25°C and 40–60% RH in a cleanroom environment. The gold/tin-plated leads resist oxidation, and the recommended shelf life is 1 year under these conditions.

Q: How does this model compare to the HALT60008A variant?
A: Both share identical core specifications (1800 nH, 0.08 mm wire, 10 MHz–20 GHz, 500 mA). The HALT60008 documentation provides application-specific guidance for bias tee circuit design, thermal analysis for 500 mA continuous DC operation, environmental reliability qualification, and a detailed five-step assembly SOP. The HALT60008A documentation covers the electromagnetic principles of conical geometry and general-purpose integration guidance. Select based on whether your primary workflow is bias tee design or general RF decoupling.

Q: What is the production lead time?
A: Stock units ship within 3 working days. Production orders typically ship within 15–25 working days depending on quantity. Contact Hoan for current lead times and volume pricing.