Medical Tool and Device Welding
A range of alloys are used in the manufacture of medical tools and devices. All must be joined with smooth welds that can be sterilised.
Lasers are a non-contact process and offer many advantages:
- Low heat input: The weld energy is delivered only where it is needed and with exceptional control
- Clean welds: Not only aesthetically pleasing, clean welds help with effective sterilisation and enable components to fit into other assemblies
- Strong welds: Lasers provide high strength with a minimum number of welds
- Hermetic welds: Unlike soldering or brazing, lasers create flawless hermetic welds, essential to many medical components.
Most medical tools are manufacturered from 304L stainless steel. It is easy to weld, has no cracking issues and does not corrode like higher carbon content stainless alloys. Other alloys such as higher hardness stainless steels (440C or 430) and some titanium alloys (e.g.: Ti 6-4) are sometimes used. All are weldable when the right procedures and alloy combinations are used.
In some cases the tools are very small, requiring an almost microscopic weld. OEM components must be joined to a hardened stainless steel for tissue biopsies or as dental tools. In other cases there are electronic components encapsulated in the tool that must be hermetically sealed in the device without damaging components.
Implanted medical devices that incorporate electronics and sensors require process control and end-product quality that are second-to-none. Not only must these devices function flawlessly, they must have an aesthetic quality that helps with sterilisation and does not irritate tissue.
Hermetic seals are needed very close to heat sensitive components and, since the value of components is high, the yield from the welding process must also be high. Laser welding has very low heat input and can be placed very close to polymer seals, glass-to-metal seals, soldered components, and electronic circuits. It can also be used to weld leads and feed-throughs on packages.
For implantable medical applications the alloy of choice is titanium which is very easy to weld due to its low thermal conductivity. It’s reactivity with oxygen and nitrogen is the only process drawback. Weld shielding with argon is critical for bright silver welds.
Pacemakers are electronic devices that are encased in a titanium package that holds the circuitry and battery. Drug pumps are more complex, comprising a mechanical pump and reservoir system along with control electronics and batteries. Laser welding of the different mechanical sub-assemblies mean that dozens of Laser welds can be part of these systems.
Implanted capsules that incorporate therapeutic radioactive elements for cancer treatments must be small, hermetically sealed, hard-wearing and easily assembled to order in a short time. They are generally less than 150µm wall thickness, less than 1mm in diameter and only a few millimeters long.
Radioactive isotopes used for cancer therapy have a rather short half-life and must be produced to order and shipped immediately for implanting into the patient. The capsules or seeds containing radioactive elements are implanted into the body inside or near the cancer itself to produce a very localised radiation treatment.
Other radioactive isotopes are used in heart procedures where the radioactivity helps reduce scarring around stents that begins to close the vessel some time after the stent is inserted. In this case the radioactive material is Laser sealed into a capsule and the capsule attached or Laser welded to a lead for insertion into the body. It takes several minutes to locally radiate the artery around the stent.
Our Lasers can be used in the manufacture of the patented radioactive implant for the Brachytherapeutic treatment of prostate cancer. The treatment involves the implantation of tiny radioactive pellets into the prostate gland. Also known as internal radiation therapy, Brachytherapy is growing in popularity.
Each pellet – smaller than a grain of rice – is engineered for optimal performance. Components fit precisely within the titanium capsule to minimise movement. Ceramic bead placement at the extreme ends of the capsule, coupled with the central Laser rotary weld, reduces the impact of seed rotation and its resulting ‚hot spots‘. As well as balancing the capsule, the central rotary weld also makes it 100% leak-proof.
redPOWER CW Lasers are the best choice for medical package assembly and sealing. The results are high quality and are not subject to the unpredictable tool wear that plagues conventional technologies. Their high peak powers and low heat input can handle different alloys and create a very tolerant process while maintaining deep penetrations. Fiber optic beam delivery is most common for these parts because of the consistent focus spot size and top-hat energy distribution which helps with fillet and butt joints to fill any gaps and get good weld nugget size for maximum yield.
With very low heat input, our Lasers produce smooth hermetic seals that can be placed close to polymer seals, glass-to-metal seals, soldered components and electronic circuits.
Fiber optic beam delivery is most common for these parts because the consistent focus spot size and top-hat energy distribution help with fillet and butt joints to fill any gaps. They achieve good weld nugget size for maximum yield in large welds but also consistently small focus spots for very fine welds (40-60µm).
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