Active implantable medical devices must operate reliably for years – in some cases, even decades. Throughout that entire time, the device enclosure must protect internal components from moisture and corrosion while maintaining its structural and mechanical integrity. This makes hermetic sealing of the enclosure an imperative for both long-term device performance and patient safety.
The joining process used for final assembly must create a continuous, leak-tight seal without damaging nearby electronics, batteries, feedthroughs, or other heat-sensitive components. And it must do so with the consistency, repeatability, and traceability required to satisfy stringent medical device manufacturing and regulatory requirements.
Several joining technologies are used in implantable device manufacturing, each offering advantages for specific applications. Here we’ll review the most significant of these joining technologies with an emphasis on laser seam welding. This is because laser welding has become the preferred approach for hermetic sealing applications since it offers the most advantageous combination of weld quality, reliability, repeatability, and compatibility with automation.
Key Challenges in Hermetic Sealing of Implants
The need to hermetically seal active implantable medical devices derives from where they operate. Inside the human body, a device is immersed in a warm, chemically and biologically active environment. It may also be subjected to shock and vibration while being expected to function reliably in any orientation.
Active implants can contain batteries, microelectronics, sensors, and communications components that are all particularly vulnerable to damage if even small amounts of moisture enter the enclosure. For some devices, microscopic leaks can eventually lead to corrosion or dendritic growth that compromises performance and ultimately results in device failure.
But the process of creating the necessary hermetic seals is complicated by several factors. In many cases, the enclosure materials themselves present significant issues.
A prime example of this is titanium and titanium alloys. These are increasingly used for implant housings because they combine biocompatibility, corrosion resistance, low weight, and high mechanical strength. A key issue is that titanium allows readily react with oxygen, nitrogen, and hydrogen at elevated temperatures. This makes precise heat control and effective shielding essential.
Joining titanium to dissimilar materials presents its own set of challenges. Intermetallic compounds can form at the weld interface, increasing brittleness and potentially reducing long-term reliability. Differences in thermal expansion coefficients between joined materials can also generate residual stress during heating and cooling that affects weld quality and package integrity.
Thermal issues are another challenge. Heat input must be carefully controlled because high temperatures can damage electronics, degrade batteries, alter material properties, or crack nearby ceramic feedthroughs. However, it’s still necessary to deliver sufficient energy to produce a continuous, leak-tight weld with consistent penetration.
Process consistency is equally critical. Medical devices are manufactured under stringent validation, quality, and traceability requirements. Manufacturers must demonstrate that a process produces hermetic welds, and that it can do so consistently over thousands of production cycles. Variations in penetration depth, porosity, alignment, or fit-up that might be acceptable in other manufacturing applications are unacceptable for implantable devices.
Finally, ongoing miniaturization continues to raise the bar in all these areas. As devices become smaller, weld seams are placed ever closer to sensitive components while tolerances become tighter. Yet the requirements for hermeticity, process repeatability, and long-term reliability remain unchanged.
Comparing Joining Technologies
Several joining technologies are currently used in the manufacture of active implantable medical devices. In many cases, different processes are employed within the same product. For example, ceramic feedthrough assemblies may be brazed before being laser welded into the titanium enclosure.
Laser seam welding has become the predominant manufacturing process for hermetic sealing of the final enclosure. Resistance welding continues to be used for some implant manufacturing operations, particularly where its simplicity and cost advantages outweigh the need for the highest levels of process control. Electron beam welding produces exceptionally high-quality welds but requires vacuum processing, increasing equipment complexity and production cost. Brazing and soldering continue to play an important role in feedthrough assemblies and other dissimilar-material joints.
The table summarizes the key characteristics of the most common joining methods.
| Technology | Hermeticity | Heat Input | Precision | Process Consistency | Key Limitation |
| Laser Seam Welding | Very High | Low | Very High | Excellent | Requires optical access |
| Resistance Seam Welding | High | Moderate | Moderate | Good | Electrode wear, geometry constraints |
| Electron Beam Welding | Very High | Low | High | Excellent | Vacuum environment required |
| Brazing/Soldering | Moderate - High | High | Moderate | Good | Larger thermal load |
Other joining technologies, including micro-TIG welding, ultrasonic welding, friction welding, and glass-to-metal sealing, are also used in medical device manufacturing. But these generally address more specialized joining requirements and are rarely utilized for final enclosure sealing.
Why Laser Seam Welding Has Become Preferred
The advantages of laser welding for hermetic sealing of active implantable medical devices derive from the process of laser welding itself.
The technique uses a highly focused beam of light to melt and fuse the materials being joined. Specifically, the laser beam is precisely positioned and moved along a programmed path, while its power is rapidly adjusted throughout the weld. Additionally, the individual pulse shape can be refined to allow finer control of the thermal input and improve weld aesthetics.
This approach offers an exceptional degree of control over both where and when energy is delivered. As a result, heat is concentrated at the weld seam rather than being distributed throughout the assembly. This ensures a dimensionally accurate weld, minimizes the heat-affected zone and reduces distortion. The result is a continuous weld that can achieve hermetic sealing while limiting thermal exposure of nearby electronics, batteries, and ceramic feedthroughs.
This highly localized heat input also makes laser welding particularly well suited to titanium and titanium-alloy housings. By delivering energy to a very small area, the laser achieves adequate penetration without affecting the microstructure of the surrounding material.
Laser welding also lends itself to a high degree of process control. Parameters such as laser power, pulse shape, spot size, focus position, and travel speed can be optimized for specific materials and joint designs, then continuously monitored during production.
This helps manufacturers maintain the validated process window required to consistently achieve the specified weld penetration and hermeticity. Integration with automated motion systems, machine vision, and manufacturing execution systems (MES) further supports the traceability and repeatability demanded by modern medical device manufacturing.
Laser welding of implantable medical devices historically used Nd:YAG lasers and these are still widely found in established manufacturing processes. But nearly all new applications use fiber lasers which offer substantially better reliability, uptime, consistency, and cost-of-ownership characteristics.
However, Nd:YAG will persist in legacy applications for one simple reason. In medical device manufacturing, even a seemingly minor process change can require extensive testing, documentation, validation, and regulatory review prior to implementation. So, Nd:YAG lasers tend to remain in use in processes for which they have already been validated.
Current Uses of Laser Seam Welding
The advantages of laser seam welding have driven its adoption in several different areas of medical device manufacturing. Some of the most prominent examples include:
- Pacemakers
Producing reliable hermetic seals in compact titanium housings containing batteries and pulse-generation electronics. - Implantable cardioverter defibrillators (ICDs)
Creating robust enclosure welds capable of protecting high-energy batteries and electronics over long service lives. - Neurostimulators
Benefitting from precise heat control to protect sensitive electronics and feedthrough assemblies located near the enclosure seam. - Cochlear implants
Forming reliable seals in highly miniaturized packages containing communication and signal-processing electronics. - Implantable drug delivery systems
Creating welds that provide long-term enclosure integrity is essential for protecting electronic control systems and power sources. - Implantable sensors and monitoring devices
Offering a precise, repeatable welding processes compatible with small package size and stringent reliability requirements. - Ventricular assist devices
Delivering clean, repeatable welds on titanium and other biocompatible alloys to support long‑term implant reliability and prevent contamination in blood‑contacting pathways. - Emerging implantable microsystems
These products, which range from neural interfaces, and MEMS-based implants through miniaturized stimulators, require the combination of precise weld placement, minimal heat input, and high repeatability that only laser joining can deliver.
Achieving Consistent, Reliable Hermetic Seals
Producing a reliable hermetic seal depends on developing a robust, repeatable manufacturing process capable of dependably operating within a validated process window.
One of the primary process objectives is maintaining consistent weld penetration. For implantable devices, the goal is not maximum penetration or weld strength. Rather, the intent is to create a continuous, leak-tight seam that protects the enclosure without exposing nearby electronics, batteries, or ceramic feedthroughs to unnecessary thermal loading.
To achieve this, fiber laser-based seam welding is typically performed in conduction mode. In this regime of operation, energy input can be carefully controlled to minimize the heat-affected zone while producing the relatively limited penetration required for hermetic sealing.
Maintaining the required consistency involves more than just selecting appropriate welding parameters. Laser power, focus position, travel speed, and part positioning must all simultaneously remain within a tightly controlled process window throughout production.
Many manufacturers integrate laser welding systems with automated motion control, vision systems, and manufacturing execution systems (MES). This enables critical process parameters to be monitored and maintained for complete traceability for every production lot.
Verification is equally important. Since even microscopic leaks can compromise long-term device reliability, manufacturers routinely verify hermeticity using helium leak testing. They also document key process parameters to demonstrate that each enclosure was produced within the validated process window. This combination of product verification and process traceability supports both validation and regulatory compliance.
Finally, weld appearance is also a consideration. A smooth, uniform weld reinforces perceptions of manufacturing quality among both regulators and clinicians. In fact, it’s not uncommon for physicians to reject devices based on appearance alone.
Getting Started with Laser Seam Welding
Hermetic sealing is one of the most demanding manufacturing processes encountered in the production of active implantable medical devices. Success depends on more than selecting an appropriate laser source. It requires a robust, validated welding process capable of consistently producing the penetration depth, hermeticity, and repeatability demanded by long-term implant applications.
Every device presents unique challenges. Housing materials, wall thickness, feedthrough design, package geometry, and nearby heat-sensitive components all influence the optimum welding strategy. As a result, process development and optimization are often as important as the welding equipment itself.
IPG Photonics combines industry-leading fiber laser technology with extensive applications expertise to help manufacturers develop and validate laser welding processes for implantable medical devices. Whether you’re designing a new product or transitioning an existing process, our applications engineers can help optimize weld parameters, establish a robust process window, and support qualification for production.
Talk to our applications specialists to learn how IPG Photonics can help you develop a reliable laser seam welding process for your implantable medical device application.
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