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Laser Wire Stripping for Medical Device Manufacturing


By Pete Doyon, VP Product Management, Schleuniger, Inc. U


sing lasers to remove insulation or coatings from electrical wires, catheters and other medical devices is now the norm. There are many benefits to using a laser stripping process for medical device manufacturing. The most


tor, for example, the laser energy is readily absorbed by the insulation but re- flected by the underlying metal conductor. Since the conductor reflects the laser light, there is no risk of it getting damaged during the stripping process. With laser stripping, there are no limits to how small the wires are. No mat- ter what the wire size, there is absolutely no risk of damage to the conductor. Another benefit is that laser stripping machines can strip round, out-of-


important is the highly-repeatable quality that is enabled by the process. When using a CO2 laser to strip polymer insulation from a wire conduc-


round, flat ribbon, or any other wire or cable shape. Stripping geometries in- clude end stripping, window stripping, slitting, or complete area ablation. The process is also very user-friendly. There are no blades to change or consum- ables to replace, in contrast to mechanical stripping methods. The process is non-contact, so there are no maintenance or wear items that need to be re- placed frequently. Laser stripping machines are also versatile. There are many different


laser types on the market, each with its own wavelength. The best approach is to select a laser with a wavelength and power that is readily absorbed by the layer to be stripped, yet is reflected by the underlying layer. Laser strippers can be used in a semiautomatic process, where the oper-


ator presents the material to be stripped to the machine. This is typically used during end stripping and can be used for single ends or a batch at a time. The laser stripper can also be fully integrated with a downstream cut-and-strip machine to measure, cut and strip fully automatically. Laser wire stripping was developed by NASA in the 1970s as part of the


space shuttle program. The technology made it possible to use smaller size wires with thinner insulation, without risk of the damage that can be caused by me- chanical wire stripping methods. The technology was commercialized in the 1990s and was initially used for aerospace and defense applications. Its use grew significantly as the consumer electronics market grew. Lasers became the only stripping solution for the tiny data cables found in laptops, mobile phones and other consumer electronics devices. Another large industry that has adopt- ed laser wire stripping is high-end medical device manufacturing.


Medical Device Applications Catheters are often used to guide a medical probe or device to the re-


quired human tissue. In high demand are reduced wire sizes to improve ma- neuverability and increase functionality. Typical applications include RF ab- lation, where the catheter carries multiple conductors and a number of ther- mocouples, as well as the RF ablation signal. This fine wiring tends to be man- ufactured using either enamel (polyimide) coatings or biocompatible fluo- ropolymers. Smaller wires, such as those used in catheters, can be nicked when using


traditional mechanical stripping methods. However, because the conductor will reflect the laser, laser wire stripping ensures a nick-free strip, with even the smallest wires. For pacemakers, their flexible, spring-like electrodes pose special chal-


lenges to laser ablation. This is due to their fluoropolymer coatings and sensi- tivity to heat during processing. However, by selecting the proper laser and processing technique, these difficulties can be overcome. Medical power tools, such as the drills used for brain surgery, must have


the highest levels of quality and reliability. Also, traditional mechanical brushing and abrading of the enameled wire used in motor windings can in- troduce dangerous particulates into the end product. Laser stripping offers a clean alternative. The hypotube is a long metal tube with micro-engineered features along


its length. It is a critical component of minimally-invasive catheters, used in conjunction with balloons and stents to open up clogged arteries. The balloon portion of the catheter is attached to the head of the hypotube. In manufac- turing such devices, it is necessary to remove part of the extruded coating, typically PTFE, ETFE or nylon-based compounds. Laser removal is proving popular over more traditional blade-based methods, primarily due to the abil- ity to automate the process. Small-gauge single conductors are very common in medical devices,


whether found in a catheter-delivered device or in cochlear implants and hear- ing aids. With laser stripping, wires as small as 50 AWG can be stripped, without damaging the conductor. Finally, flat micro-coaxial ribbon cables are found in a great number of


medical device interconnects. A classic example is that of the ultrasound cable. High-density, high-frequency signals must be transmitted with the most flexible cabling possible. This dictates very small conductor sizes in high- density, micro-coax ribbons. Laser stripping guarantees quality results in


these tiny cables. Contact: Schleuniger, Inc., 87 Colin Drive, Manchester, NH 03103


% 603-668-8117 fax: 603-668-8119 E-mail: sales@schleuniger.com Web: www.schleuniger-na.com r


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