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Laser Wire Stripping and the Science of Interconnects
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Stimulation electrodes are used to alter the physiology of organs to treat conditions such as heart arrhythmia through RF ablation electrodes. The development of new and
advanced interconnects in the med- ical device market continues apace. In the pursuit of the most compact and efficient fine wire connections, developers are starting to capitalize on the company's capabilities in pro- ducing precision windows in minia- ture ribbon cable assemblies. By combining the latest devel-
opments in precision optical beam delivery and real-time vision sys- tems, the company is able to produce very small windows in ribbon cables. For these types of applications, Laser Wire Solutions' Odyssey-4 laser wire stripper provides the precision neces- sary for reliable medical devices.
Micro-Coax Cables Micro-coax cables are made up of
a metallic conductor with a dielectric insulation, which in turn is covered by a braided shield and polymer jacket. Micro-coax cables are found in a wide variety of applications, from mobile phones and laptops to medical cabling, such as ultrasound cables. Single micro-coax cables down
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to 38 AWG can be stripped by sophis- ticated semi-automatic mechanical wire strippers. Rotating blades are set precisely to cut into the various depths of the cable and cut each layer sequentially. However, for smaller wires and ribbonized micro-coax cables, mechanical solutions are no longer possible. For these very small wires, a laser process is the solution. A critical step in the processing
of a micro-coax cable is the cutting of the shield. The standard laser method for cutting it is to solder dip the cable so that the shields become tinned. In the tinning process, the individual shield wires bond together to make a solid mass. A fiber laser then cuts into the soldered shield.
as not to damage the dielectric. The company is able to offer advice on suitable materials for a dielectric, as this has a direct impact on the possi- bility of applying solder-less scribing. This method can be useful even if there is sufficient shield for soldered scribing. A disadvantage of the sol- dered method is the number of steps and specialized tools needed to pull back the slug and snap the shield. Adopting a solder-less method allows a single automatic laser process to be
Laser-stripped USB cable
showing cross cut insulation and remaining slugs.
used. For these types of micro-coax applications, the company offers its Titan machine.
Bonded Enamel Wire One class of polymer insulation
that cannot be effectively stripped with the Mercury system is bonded enamel wire. The wire is dipped in an enamel
liquid which forms an
extremely thin, but tough, insulation layer. There are many formulations,
but polyimide is common. The CO2 laser may be able to remove some of the enamel insulation, but almost always leaves a residue a few microns thick, which then prevents
Laser-stripping can remove enamel insulation from very fine wires.
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The process makes a deep cut into the shield, but doesn't cut all the way through it. This creates a natural fracture line, so when the coax is bent at the stress point, the shield snaps cleanly. The shield is then pre- tinned for connecting an earth bar. For the latest generation of flex-
Materials for Harsh Environments
1.603.352.1415
polyonics.com
ible micro-coax cables, there may be insufficient shielding to form a solid mass when soldered. In this case, an alternative is required. Solder-less scribing directly cuts the shield wires with the laser. As the shield is cut all the way through and directly in con- tact with the dielectric, it is vital that the cutting process is controlled, so
effective soldering. Polyimide is used to coat fine
wire, because it functions well in high temperatures. This allows high densities of wires to be used in coils. Enamel insulation is also used where very thin coatings are needed to min- imize the overall wire diameter, which is needed frequently for med- ical applications. The company's Odyssey range
of laser wire strippers uses ultravio- let laser technology. The key feature of the system is that the ultraviolet wavelength is absorbed by enamel insulation, which is immediately
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