Extended SRF Conical Inductors 3D Laser Skin Loss Microwave Inductor

Custom Conical Inductor Extended SRF Millimeter Wave Limit 3D Laser Surface Modification Skin Loss Blind Mate Assembly

HACC-CUSTOM-MW: Extended-SRF mmWave Conical Inductor with 3D Laser Surface Modification & Blind-Mate Assembly

Extended-SRF Millimeter-Wave Limit Customization

Standard conical inductors achieve SRF of 20–40 GHz — adequate for microwave but insufficient for V-band (50–75 GHz) and E-band (60–90 GHz) millimeter-wave applications where parasitic capacitance at the apex becomes the dominant limiting factor. The HACC-CUSTOM-MW extends SRF beyond 50 GHz through three concurrent design optimizations: an ultra-fine apex diameter below 0.15 mm minimizes the physical capacitance plate area at the high-impedance node; laser-tapered wire ends eliminate stub capacitance that would otherwise create a parasitic resonance below the rated SRF; and single-turn apex winding reduces inter-turn capacitance by minimizing the number of adjacent conductors at the high-frequency end. Apex parasitic capacitance is verified below 0.005 pF by EM simulation and VNA measurement. The result is flat, resonance-free impedance from 10 MHz to 50 GHz (rated) with reference performance extending to 67 GHz — enabling bias-tee and choke applications in E-band backhaul, automotive radar at 77 GHz, and millimeter-wave instrumentation.

3D Laser Surface Modification for Reduced Skin Loss

At millimeter-wave frequencies, RF current flows in a thin skin depth — approximately 0.3 µm in copper at 50 GHz and 0.2 µm at 77 GHz. Standard drawn copper wire has a surface roughness (Ra 0.05–0.2 µm) that, while appearing smooth at optical scales, creates a tortuous current path at skin-depth scales — increasing the effective AC resistance by 10–40% compared to an ideal smooth conductor. The HACC-CUSTOM-MW applies 3D laser surface texturing to the wire before winding: periodic micro-grooves 1–5 µm deep are inscribed onto the wire surface in customer-selectable patterns — axial grooves for broadband reduction, circumferential rings for narrowband optimization at a specific frequency, or cross-hatch for maximum reduction across the full band. The surface roughness Ra is controlled from 0.5–2.0 µm per the target frequency band, with laser power and scan speed optimized for each wire diameter. This engineered texture reduces the effective AC resistance by 15–25% at 28–60 GHz compared to smooth drawn wire of the same diameter — translating directly to reduced insertion loss in the bias-tee or choke application.

Co-planar Blind-Mate Assembly & Micro-Height Specification

Millimeter-wave module assembly demands precise Z-axis control: a vertical offset between the inductor apex and the RF trace plane creates an impedance discontinuity that degrades return loss at V-band. The HACC-CUSTOM-MW is designed for blind-mate co-planar assembly: the mounted height is specified from 0.5–1.0 mm, with the apex Z-height aligned to the RF trace plane within ±25 µm — verified by optical CMM post-assembly. A custom micro-pickup tool with a 0.15 mm anti-static vacuum tip achieves placement accuracy of ±10 µm. The base is epoxy dot-fixed to the substrate, and the apex sits flush with the co-planar RF line — no vertical stub, no impedance step, and no compensation network required.

Key Specifications

Applications

• E-Band (60–90 GHz) Backhaul Bias-Tees — SRF >50 GHz, skin loss reduced 15–25%, blind-mate co-planar for mmWave module integration
• Automotive Radar (77 GHz) — Laser-textured wire for minimum insertion loss at 77 GHz, <0.15 mm apex for extended SRF margin
• V-Band Instrumentation — 67 GHz reference performance, .s2p file per device, Z-height ±25 µm for precision test fixtures
• 5G mmWave Small Cell Front-Ends — Blind-mate assembly <1.0 mm height, co-planar apex for phased array bias injection

Contact us with your target SRF, frequency band, and assembly height requirements. Extended-SRF millimeter-wave conical inductors with 3D laser surface modification ship in 5–7 business days.