Advanced glass-to-metal feedthrough system for implantable medical devices (IMDs) in the patent “Glass-to-metal feedthrough seals having improved durability particularly under AC or DC bias.” This innovation presents a single or multi-pin arrangement featuring selected glass-to-metal seals for a feedthrough, equipped with a ceramic disk member connected to the sealing glass surface in potential contact with bodily fluids.

The intricately designed feedthrough, involving judicious selection of component materials such as ferrules, seal insulators, and pins, facilitates compression or matched seals for electrical feedthroughs. These seals aim to provide corrosion resistance and biocompatibility essential in IMDs. The configuration accommodates either a single pin within a single ferrule or at least two pins within a single ferrule. For the multi-pin arrangement, an insulator material, like alumina ceramic, zirconia ceramic, zirconia silicate ceramic, or mullite with higher melting points than the sealing glass, is distributed around the pin within the ferrule. Alternatively, materials such as feldspar porcelain or alumino-silicate glasses, with lower melting points than the sealing glass, are employed.

The invention serves the field of electrical feedthrough devices, specifically single and multiple pin electrical feedthrough assemblies. It facilitates electrical communication between various electrical components, such as medical electrical leads and diverse sensors, contained within the hermetically sealed IMD.

The application of this innovative feedthrough system extends to various implantable pulse generators, including neurostimulation devices, deep brain stimulators, and body implantable pulse generators (IPGs) designed for treating conditions like bradycardia and tachyarrhythmia. These advancements ensure the integrity of glass-to-metal seals, playing a crucial role in ensuring the reliability and hermetic sealing of critical implantable medical devices.

For a comprehensive understanding of this revolutionary glass-to-metal feedthrough technology and its implications for hermetic sealing in IMDs, the full patent documentation is available here.

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Image and article courtesy of patents.google.com

A glass-to-metal seal is a way to protect electrical components by sealing them within glass and metal. There are two types of glass-to-metal seals. Matched seals use varieties of glass and metal that have similar thermal expansion properties, while compression seals use materials that respond to heat differently. The glass-to-metal seal technique is often used in the aerospace and military sectors, where electronics need to perform under harsh environmental conditions.

The purpose of a glass-to-metal seal is to create an airtight, or hermetic, seal around the electronic components. This is accomplished by placing the electronics inside a glass component that is surrounded by a metal part. The glass is formed using sintering. Sintering is a process of creating a solid mass out of powdered or crushed elements by heating the material to just below its melting point and then applying pressure to shape the material. This results in a pure, uniform final product.

A matched glass-to-metal seal is made out of materials that are chosen for their similar thermal expansion coefficients. The thermal expansion coefficient of a material is a value that can be plugged into a formula to find out how much a material will expand for each degree of temperature increase. Using matched materials means that both the glass and the metal will expand and contract at the same rate with heat and cold. This ensures that the glass-to-metal seal will not break when used under the most extreme conditions.

Read more: What Is a Glass-To-Metal Seal?