What is medical grade micro coaxial cable for ultrasound probe and how does it differ from standard coax? - Micro Coaxial Cable factory-(FRS)

Overview and definition

Medical grade micro coaxial cable for ultrasound probes is a highly miniaturized, high‑density interconnect that carries high‑frequency ultrasound signals between the probe’s piezoelectric array and the imaging system. It is built as a bundle of dozens to hundreds of individually shielded micro‑coaxes, each preserving a controlled characteristic impedance to minimize signal loss and crosstalk in a very small cross‑section. Typical configurations range from about 130 to 266 micro coaxes, with common conductor sizes of 42–44 AWGand even down to 46 AWGfor ultra‑fine endoscopic probes. These cables are engineered for the demanding mechanical and electrical environment of handheld and cart‑based ultrasound, often with stringent biocompatibilityand flexibilityrequirements and, in many designs, silver‑plated copper alloyconductors for lower resistance and stable transmission. The industry also offers integrated subassemblies and connectors purpose‑built for imaging systems, reflecting the maturity and specialization of this segment

Why it matters in ultrasound imaging

In an ultrasound probe, each element in the array must be driven and its echo received with high fidelity. The micro coax bundle acts as a parallel set of ultra‑low‑loss transmission lines: preserving impedance, reducing attenuation, and maintaining consistent phase and amplitude across channels is essential for image clarity, resolution, and signal‑to‑noise ratio. Because these cables are repeatedly flexed and twisted during exams, materials and construction must balance flex life, EMI shielding, and mechanical robustnesswhile keeping the probe ergonomic. For high‑frequency imaging, where cable attenuation and phase distortion become more pronounced, the choice of micro‑coax parameters (such as AWG, dielectric, and shielding) is tightly coupled to the probe’s operating band and image quality targets

How it differs from standard coax

Compared with general‑purpose coax used in RF, test, or broadcast, medical probe micro coax is optimized for miniature size, ultra‑high channel count, and dynamic flexing in close proximity to the patient. Typical differences include: much smaller AWG(e.g., 42–46 AWGvs. 30–24 AWG), a much higher core countin a single bundle (tens to hundreds), construction that often keeps individual micro coaxes from being stranded in the bundle to preserve impedance and reduce microphonics, tight impedance controlfor high‑frequency integrity, enhanced shieldingfor EMI immunity in clinical environments, and medical‑gradematerial and process controls (e.g., biocompatible jacketing, stringent lot‑to‑lot consistency). Standard coax, by contrast, is typically larger in diameter, lower in core count, and not optimized for millions of small‑radius flex cycles or the ergonomic constraints of handheld probes

Core design parameters and how to choose

• •Conductor size and material: 42–44 AWG(and even 46 AWGfor endoscopic miniaturization) are common; silver‑plated copper alloyis widely used to lower resistance and improve high‑frequency performance.
• •Capacitance per unit length: Typical micro coax in probes is around 50–60 pF/m, with some designs reaching ~110 pF/mdepending on dielectric and geometry; lower capacitance generally favors higher bandwidth and lower loss at high frequency.
• •Shielding and crosstalk: Individual micro coaxes are shielded, and the overall bundle often adds braid/foil layers to suppress EMI; dense packing and precise lay length help control crosstalkand maintain channel‑to‑channel isolation.
• •Mechanical design: The micro coaxes in a probe bundle are often not stranded(structure‑dependent) to maintain impedance and reduce mechanical microphonics; overall flexibility and fatigue life are achieved through stranding of the bundle, choice of dielectric, and jacketing compounds.
• •Geometry and fit: Overall ODis tightly constrained by probe handle and ergonomics; common finished ODs in production include about 6.6–9.6 mmdepending on core count and configuration.
• •Matching to frequency: Higher‑frequency probes require lower‑loss, lower‑capacitance designs with excellent high‑frequency impedance control to limit attenuation and phase distortion; mismatches can degrade image quality.These parameters are chosen together—there is no single “best” cable; the right answer comes from trading off frequency band, image quality targets, flexibility, and reliability for the specific probe form factor125.

Real‑world configurations and examples

Below are representative constructions to illustrate the variety and trade‑offs in probe micro coax design. These examples are from production catalogs and are not exhaustive; they show how core count, AWG, capacitance, and OD interrelate in practice.

These illustrate typical capacitance targets (~50–60 pF/m, with some ~110 pF/mdesigns), a range of AWG 38–44, and finished ODs from ~6.6 to ~9.6 mmdepending on core count and application. Compatibility lists from manufacturers often include GEand Mindrayconfigurations, reflecting common industry platforms

Connector and system integration trends

As ultrasound systems evolve, so does the interconnect. High‑density, low‑profile connectors such as ZIFand board‑to‑wire interposers (e.g., TC‑ZIFwith up to 260 pinsand 20,000 mating cycles, MP456Pimaging I/O) enable smaller, more reliable probe heads and faster time‑to‑market. New digital ultrasoundarchitectures move some of the signal conditioning into the probe or system, allowing hybrid high‑bandwidth links and advanced thermal management; this can relax some constraints on the cable while emphasizing overall system signal integrity and ergonomics. Leading suppliers also offer fine‑wire and fine‑pitch terminationexpertise and complete probe assemblies, reflecting the industry’s shift toward integrated, application‑engineered solutions

Engineering insights and best practices

• •Start with the probe’s center frequency and bandwidth: higher frequencies demand lower‑loss, lower‑capacitance micro coax with tight impedance control to limit phase and amplitude errors.
• •Model the channel bundle: account for mutual capacitanceand crosstalkacross the bundle; dense packing and consistent lay length help maintain channel isolation.
• •Choose the right AWGand conductor: finer 42–44 AWG(or 46 AWGfor miniaturization) reduces resistance and supports high‑frequency performance; silver‑plated copper alloyis a common choice for conductivity and flexibility.
• •Design for flex and fatigue: keep individual micro coaxes from being stranded to preserve impedance; rely on bundle stranding, optimized dielectric, and medical‑grade jacketing for long flex life in handheld use.
• •Control EMI: use individual shields plus overall braid/foil, and consider the probe’s operating environment (strong imaging fields, nearby electronics) when specifying shielding coverage and materials.
• •Plan for system integration early: match the cable’s electrical and mechanical profile to connector pitch, board layout, and overall ergonomics; leverage suppliers with fine‑wire terminationand probe assemblyexperience to de‑risk integration and time‑to‑market