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Medical Catheter Wire Stripping

Medical Catheter Wire Stripping

What is Electrophysiology?

Electrophysiology is the study of the electrical properties of biological cells and tissues. It involves measurements of electric current on a wide variety of scales from single ion channel proteins to whole organs like the heart. In neuroscience, it includes measurements of the electrical activity of neurons, and particularly action potential activity. Stimulation electrodes are used to alter the physiology of organs to treat conditions, such as heart arrhythmia through RF ablation electrodes.

Wire Stripping Challenges

The latest advances in electrophysiology require packing ever more sensors and wires into ever smaller packages. Polyimide (also called enamel) type insulations offer the highest density of interconnects due to the thin, tough insulation. Wire gages of 42 AWG to 50 AWG are now commonplace, with applications for wires smaller than 50 AWG now appearing. These wires are tough to strip.

There are only two real options: mechanically scraping or hot caustic dipping. The former presents a challenge for small gages due to damage of the conductor and the latter is not preferred due to safety issues and residues. Even standard laser stripping with carbon dioxide lasers is not a solution as the long wavelength of the light means that a microscopic residue is left which cannot be soldered to.

The Solution

Our Odyssey UV laser technology offers a gentle, yet powerful method for the removal of polyimide type insulations. The short wavelength of the ultra-violet light coupled with nanosecond duration pulses enables the enamel to be instantly vaporized. By tuning the energy of the laser pulses it is possible to completely remove the enamel whilst leaving a clean metallic surface for soldering. The process is gentle enough to leave thin plating layers, such as gold, silver or tin without removing them. By controlling the laser pulse energy, it is also possible to laser cut fine wires with the same laser source – meaning a convenient and accurate method for controlling strip length.

Unlike older gas based excimer technology which is very expensive to purchase and run, the Odyssey systems utilize modern solid-state laser technology which has no dangerous consumable gases. Also utilizing “direct-write” technology means that strip patterns can be directly programmed via the user interface and there is no need for cumbersome masking and imaging of the laser beam.

Boston Scientific Mapping Catheter
Boston Scientific Mapping Catheter

Catheter bifilar thermocouple laser stripped
Catheter bifilar thermocouple laser stripped with Odyssey technology

Pre-cut wires, such as those protruding from the catheter handle, can be be stripped directly using our new compact Odyssey-4 machine, which launched in 2017. This system can also be automated to strip wires directly from a spool and then either be re-spooled or cut to length.

Precision stripping example using Odyssey system
Precision stripping example using Odyssey system

In order to precisely strip the wire, it is necessary to hold the wire precisely, measure its location relative to the laser beam and control the laser position with high accuracy. Our customizable Odyssey systems integrate high resolution vision systems, precision fixturing and flexible UV laser stripping and cutting technology. These automated systems are capable of self-calibration to maintain perfect alignment day-in, day-out.

A number of specialist wire manufacturers are able to create multi-filar ribbon cables which can be highly convenient in a device design if it is possible to strip windows in the ribbon cable for direct bonding to flex cables or PCBs. This is something that can only be achieved with advanced laser stripping technology. To make an ideal connection it is necessary to selectively strip one wire without impinging on adjacent wires. Furthermore, it is often convenient to laser cut the wires to further aid the soldering process.

Download the Medical Catheter Wire Stripping Application Note.

Contact us to find out how we can help you with your particular medical device application.

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