Articles of the month written for Flash DM Experts (June 2023)
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Cisteo MEDICAL is equipped with a micro-welding machine based on resistance welding technology for the manufacture of medical devices.
Why choose this resistance welding technology? In order to weld smaller diameters (a few tens of micrometers in diameter) and achieve faster performance, but also to weld different materials, in this case gold to platinum-iridium, the alloy used for electrical contacts.
This gives the R&D team a complementary process to laser welding and brazing when it comes to identifying the most suitable welding technology, particularly for Class III medical devices and active implantable medical devices (AIMD).
The advantages of resistance welding for medical devices.
These machines are currently used to manufacture neurostimulators. For stimulation implants, particularly nerve implants, we're talking about a diameter of less than 1 mm. Thanks to this technology, Cisteo MEDICAL can weld wires of up to 50 microns in just a few milliseconds.
Cisteo MEDICAL welds on materials that are not necessarily the same, which is a real advantage. Resistance welding makes it possible to combine materials, and provides solutions adapted to the challenges of miniaturization.
For a medical device such as a biosensor, which adapts to the patient's morphology, spot welding is particularly suitable, as it enables flexible materials to be welded.
This technology offers controllability of the heating temperature and power and in particular allows the welding of pacemaker battery interconnections.
Resistance welding is ideal for medical device manufacturing because the low voltage causes little or no distortion of the materials being joined and produces no contamination .
Thanks to this technology and to make the device innovative, Cisteo MEDICAL designs interconnection options corresponding to the standards of medical devices. Interconnection technologies such as resistance welding make it possible to integrate miniature and compact systems .
Some applications using resistance welding :
How does Cisteo MEDICAL integrate micro resistance welding into its processes?
Implanted devices benefit from an extremely reliable manufacturing process. That's why Cisteo MEDICAL's R&D team pays particular attention to the design and prototyping phase, to guarantee the reliability of the manufacturing process, and thus patient health and cost control for the manufacturer or medtech start-up.
As early as the system development phase, the R&D team takes into account the manufacturing process and identifies the appropriate welding technique (laser welding, hot bar bonding, resistance welding, ultrasonic bonding).
From one project to the next, the technology must be adaptable to restrictions such as size, geometry and accessibility of the interconnect location.
At Cisteo MEDICAL, our manufacturing engineers can choose to use resistance welding to ensure an interconnect that not only conforms to the unique needs of the project, but also by extension guarantees a durable device that will best fit the patient.
Microsoldering, some technical explanations
As the name suggests, resistance welding uses resistance to current flowing through workpieces to generate welding heat. Like other types of spot welding—such as laser welding—resistance welding is often used in medical device manufacturing because it works well with thin materials.
The choice of welding method to use depends on the materials being welded, the location of the weld, and the desired mechanical strength. Resistance welding works by applying pressure and electricity simultaneously to the areas being joined. Electrodes press the two pieces of metal together, then initiate a low-voltage, high-current DC flow of electricity. The higher resistance felt where the two pieces meet raises the temperature, and the resulting heat causes the metals to bond.
Resistance welding can form a fusion bond where the material on either side of the interface melts, mixes, and solidifies to form a weld. Fusion bonding is quite common for welding resistive alloys such as stainless steels. While the presence of fusion may be considered the preferred type of bond, this is not often the case for medical devices where welding dissimilar metals/alloys is common. In the case of resistance welding, when welding dissimilar metals that have very different melting points, the lower melting point alloy may melt and form a braze on the higher melting point metal.
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