How to prevent moisture penetration of powered surgical tools

03 February, 2022

Electrical and magnetic circuit failure

Electronics should also be protected in a moisture resistant material. Potting involves placing the components inside a housing with a liquid compound such as silicone or epoxy resin poured over, filled and sealed, with a vacuum applied to remove trapped air. The assembly is cured and the liquid hardens, protecting the components inside.

Alternatively, transfer moulding involves loading the components into a heated mould cavity. Like the potting process, an encapsulating material is then introduced, and the heated mould ensures that the flow remains liquid to ensure a complete fill before thermoset curing. Both techniques provide high moisture resistance as well as protection against temperature, vibration and impact, as well as offering strain relief for exposed wires.

An alternative means of protection is conformal coating. Often comprised of parylene, conformal coating is applied as a vaporized gas and creates a very thin moisture-resistance coating, virtually free of voids. Conformal coating though isn’t as durable as potted or transfer moulded assemblies and doesn’t provide the same protection to vibration or impact.

Regarding the magnetic circuit, exposure of the motor winding to moisture can also cause failure. To resist the effects, magnet wire with heavy build insulation should be used and the formed coils moulded or potted to the PCB. To avoid permanent magnet corrosion or demagnetisation, the appropriate choice of magnet and coating types must also be selected.

Motors tailored for surgical tools

To maximise the reliability of the device against moisture, the tool and the motor should be designed in collaboration. Portescap creates custom designed autoclavable motors for surgical device OEMs according to specific application requirements. Able to endure thousands of sterilisation cycles and used in surgical theatres worldwide, Portescap’s motors not only increase reliability and reduce cost, but also serve to improve patient outcomes.

www.portescap.com

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