Welding Implantable Medical Devices

Welding and Sealing Medical Devices

An implantable medical device is a biocompatible component placed in the human body to aid or augment various biological functions. An implantable device can vary from contact lenses to artificial joints to heart pumps to monitoring systems, and the market keeps expanding as the human lifespan continues to rise, chronic disease rates increase and organ donors become more scarce.

The interior of the human body is a hostile environment to foreign objects, and medical implantables require specific materials and manufacturing techniques to ensure proper function and safety in a patient. At EB Industries, we have decades of experience working with the metals most often used in implantable devices, as well as mastery of the laser welding and hermetic sealing processes required to produce long-lasting devices with the highest level of patient safety, while meeting ISO 13485, the standard to which medical devices must adhere.

Representative Parts and Applications

EB Industries has particular experience welding and hermetic sealing medical implants that have powered electronic components. One of these devices is an assembly for Abbott Labs, the HeartMate 3, the most advanced left ventricular assist device (LVAD) on the market and the preferred option for patients who require bridge care while awaiting a heart transplant, or as permanent treatment for patients too infirm for a transplant. The HeartMate 3 ensures consistent blood flow, reducing stress on the heart and providing short or long-term cardiovascular support. EB Industries has performed various assembly, welding, and later testing operations for thousands of these assemblies over several years.

A similar application we weld for a different customer is the V-LAP, a miniature, wireless and battery-free microcomputer that measures the left atrial pressure in the heart where high pressure readings are an indicator of congestive heart failure. This device greatly reduces hospitalization rates as the patient is constantly monitored. Doctors can also access data from the device remotely, without requiring an in-person visit, and can prescribe medication or other treatments as needed.

We also assemble and weld devices for pain management, such as spinal cord stimulators, which allow a patient to alleviate pain by selectively controlling electrical impulses sent to implanted electrodes strategically placed in neural pathways, via a simple remote control. A similar implantable neurostimulation device we weld is used to treat spinal cord injuries and patients with ALS. This device uses electrodes and a small, battery-powered external pulse generator to cause the diaphragm to contract to aid with breathing.

Difficult Application Requirements

Critical to the success of a medical device is the immune system’s acceptance of the material from which it is constructed. Hence, material choices are extremely limited, based on biocompatibility testing. The most common metal used is titanium. Titanium is lightweight, resistant to corrosion from bodily fluids, and has a unique ability to bind with bone and living tissue, making it well-suited for use in medical applications. Unlike many other low mass metals, titanium is exceptionally strong and durable, typically lasting over twenty years inside the human body. Titanium also is non-ferromagnetic, meaning it won’t cause issues with MRI scanners, which rely on electromagnetism. Stainless Steel is sometimes used as well for bone screws and other implanted devices, but there is evidence that titanium has lower failure rates and fewer complications than stainless steel in similar applications. We have decades of experience working with both metals, as well as a host of others, ranging from common to exotic.

In most circumstances, implants need to be as small as possible to minimize the trauma of implantation and stress on the patient, this provides the implant with the greatest chance of integration into nearby bone and tissue. We have welded parts as large as hip replacement acetabular cup and femoral heads and stems. Contrast that to one of the smallest implantable medical devices we are currently laser welding that has a component that is .0004” thick, roughly ten times thinner than a human hair.

Overcoming the Specific Challenges of Welding Implantable Medical Devices

Medical implants, because of their size and functionality, often present complex weld profiles. This can make them more difficult to weld compared to simple linear or rotary weldments. With the help of CNC controlled motion, and 4 and 5 axis welders, even complex profiles can be precisely welded and repeatedly so. EB Industries also has in-house tool design and fabrication capabilities, which allows us to develop fixturing tailored to part complexity, increasing accuracy and repeatability by virtually eliminating part-to-part variations in weld location, focal plane, etc.

Cover gasses are essential for laser weld purity. A critical challenge when laser welding medical device assemblies is maintaining proper gas coverage. Argon is a common cover gas used when laser welding titanium components to prevent the molten weld pool from reacting with oxygen and nitrogen, which can cause oxidation and associated weld defects, such as cracking and blowouts. To maintain coverage, we use modified coaxial and cross jet gas nozzles that create a constant, laminar flow across the weld area.
We have the option to weld devices in an inert environment glovebox. Our gloveboxes have gas analyzers to make sure that nitrogen and oxygen are only present in low parts per million if inside the box at all. Gas analyzers also ensure that the proper mixture of gases, such as a blend of argon and helium, is present in the glovebox to provide the best welding results.

We also can hermetically seal medical implantables in gloveboxes, which are equipped with vacuum ovens that can vacuum bake parts before welding to eliminate moisture. Excess moisture above 5000 ppm (the maximum limit permitted in MIL-STD 883) in these parts can greatly reduce the performance and life expectancy of the internal components. Vacuum baking ensures that the internal environment of the device is clean and dry, and laser welding ensures that the seal is impermeable and rugged. Further, our gloveboxes are inside of a cleanroom-certified environment equipped with HEPA filters and a laminar flow work bench. This additionally protects sensitive devices from contaminants and foreign object debris (FOD).

Medical implantables with internal electronics are very electrostatic discharge (ESD) sensitive due to the intricate circuitry contained within them. As mentioned previously, a common feature of these devices is the combination of electrodes and a battery pack to generate a signal to the electrodes. A build-up of static electricity greatly increases the chances of short-circuiting inside the device. We mitigate this by practicing all ESD safety precautions during processing: our operators wear ESD wrist straps, full electrostatic dissipative flooring and benches, all the machines used in production being appropriately grounded, a humidity controlled room to prevent charge buildup, etc. Our technicians are well-trained in ESD precautions and aren’t authorized to begin working in that department until a supervisor has confirmed their training has been completed.

Medical devices are also extremely sensitive to heat for similar reasons. Excessive heat can destroy the internals of these devices. They can also damage the parts due to their typically small size and fragile nature, as heat can build up very quickly and cause warping, etc. By using a small laser beam spot size, we can achieve a higher power density and thus input less heat for the same depth of weld than if we were to use a larger size.

Often, companies welding titanium are unaware of a particular problem presented by the material. Titanium has a tendency to emit unusually bright sparks when welded, which make it difficult to see the weld joint in the sighting optics of the laser. EB Industries has a proprietary process to combat this, which allows us to accurately see the weld joint and ensure precise weld placement and efficacy.

Why Partner with EB Industries

It’s imperative to collaborate with a supplier who has the expertise and experience with welding medical devices as mistakes are critical and potentially fatal. EB Industries is certified to ISO 13485:2016, which shows our commitment to adhering to stringent industry standards in terms of processing and corresponding paperwork. Our equipment, operator training, and entire welding process is built around conforming to ISO 13485.

Another key feature that adds value to our process is that we have in-house testing abilities to assess parts before shipping them back to you. It’s our standard procedure to visually inspect 100% of our welds. We can also perform leak testing per MIL-STD-202 and MIL-STD-883. We can also pressure bomb assemblies up to 4 ATM to evaluate parts that weren’t welded with Helium as a tracer gas.

At EB Industries, you’re working with experienced engineers and highly trained technicians to turn your prototype implantable medical device into a successful product. We can help you from the beginning, with designing your weld joint and helping with material selection to setting up processes in production which consistently produce top quality medical device products. Please contact our engineering team to discuss your application. Whether you’re in development or production, we’d be happy to provide ideas, information, guidance and support.

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