The reliability and longevity of electronic devices depend on effective hermetic sealing, which creates a barrier to moisture, gases, dust, and contaminants. Essential in military, aerospace, and consumer electronics, hermetic seals protect sensitive components in harsh environments. 

This guide covers the process, materials, techniques, and applications of hermetic sealing in modern electronics packaging.

What is Hermetic Sealing?

Hermetic sealing creates an airtight, moisture-proof, and gas-tight barrier around electronic devices to protect internal components from environmental factors. It is crucial for components exposed to extreme temperatures, pressure, or humidity, such as satellites and sensors, to prevent malfunction or failure.

Types of Hermetic Seals

There are several types of hermetic seals used in electronic packages, each offering distinct advantages depending on the application requirements. These include:

• Glass-to-Metal Seals: One of the most common types of hermetic sealing, glass-to-metal sealing uses a combination of metal and glass to create a strong, airtight barrier. This seal is used in components such as feed-throughs and connectors where the glass forms a bond with the metal, preventing leakage while allowing electrical conduction.

• Ceramic-to-Metal Seals: Ceramic-to-metal seals are perfect for applications that demand high-temperature resistance. The ceramic material is bonded with metal through a special sealing process, ensuring both a reliable barrier and robust mechanical strength, particularly in extreme environments.

• Polymer Seals: Used in less demanding applications, polymer seals are often employed for their ease of use and cost-effectiveness. These seals may not offer the same level of protection as glass or ceramic options, but they provide sufficient hermeticity for many consumer-grade electronic devices.

• Welded Seals: Welded seals are formed by directly fusing the materials at the package's boundary. This process ensures a strong and permanent bond, preventing leakage even under stress. These are often used for high-performance and high-reliability applications.

Hermetic Sealing Process

The process of hermetic sealing generally involves the following steps:

• Design and Material Selection: The first step in hermetic sealing is selecting appropriate materials for the package and seal. Materials must be chosen based on factors such as thermal expansion properties, corrosion resistance, and electrical conductivity. Glass, ceramics, metals, and polymers are common choices, each suitable for different applications.

• Cleaning and Preparation: To get rid of any debris, grease, or other impurities, surfaces that will be sealed must be cleansed completely. This guarantees an effective bond between the sealing materials, avoiding weak spots in the seal.

• Assembly: After preparing the components, the sealing process begins. For glass-to-metal seals, for example, the glass is carefully placed around the metal components, and heat is applied to create a strong bond. The assembly process must be closely controlled to prevent imperfections in the seal.

• Inspection and Testing: After the seal is made, the package undergoes rigorous testing to ensure its hermeticity. Various methods, such as pressure testing or helium leak detection, are used to detect any potential weaknesses in the seal.

• Final Packaging and Shipping: Once the hermetic seal has passed inspection, the device is packaged and shipped for use. For critical applications, such as space exploration, this final step involves additional testing to confirm that the package will perform as expected in real-world conditions.

Challenges in Hermetic Sealing

While hermetic sealing offers numerous benefits, it also presents some challenges, particularly when it comes to high-volume production.Some of the main challenges include:

• Material Compatibility: When exposed to temperature fluctuations, different materials expand and contract at different rates, which might cause the hermetic seal to fail. It's crucial to make sure the seal and the materials utilized in the package are compatible.

• Cost and Complexity: The sealing process can be expensive, especially when high-reliability seals are required. Additionally, the process can be complex, requiring specialized equipment and expertise. This makes hermetic sealing more suitable for high-value, mission-critical applications.

• Quality Control: Ensuring that each seal is made properly is essential for the integrity of the electronic device. Quality control is a key consideration, and advanced testing methods are often necessary to verify the success of the sealing process.

• Environmental Factors: During the sealing process, external environmental factors such as humidity, dust, and temperature can influence the effectiveness of the seal. Controlling these factors is crucial to ensure the success of the sealing process.

Applications of Hermetic Sealing in Electronics

Hermetic sealing finds applications across many industries, but it is especially critical in areas where reliability is paramount. Some of the primary sectors benefiting from hermetic sealing include:

• Aerospace: In aerospace applications, electronic components are exposed to extreme conditions, including high altitudes, low pressure, and temperature fluctuations. Hermetic sealing protects vital components like sensors, transistors, and microelectronics, ensuring they perform reliably during flights and space missions.

• Military and Defense: Military electronics, such as radar systems, communication equipment, and weaponry, must operate reliably in hostile environments. Hermetic seals aid in shielding these gadgets from impurities like moisture and dust that can impair their performance.

• Medical Devices: Medical devices, such as pacemakers and diagnostic equipment, require hermetic sealing to prevent contamination and ensure long-term reliability. These devices often come into direct contact with the human body, making hermetic sealing essential for maintaining their integrity and performance.

• Automotive: The development of advanced driver-assistance systems (ADAS) and electric automobiles has made hermetic sealing essential in automotive applications. It guarantees that moisture and other environmental dangers are kept away from sensors and other vital electronic parts.

• Consumer Electronics: While not as demanding as the military or aerospace sectors, consumer electronics such as smartphones, laptops, and wearables can also benefit from hermetic sealing. It helps ensure that sensitive components inside the device are shielded from the elements, contributing to longer device lifespans.

Future of Hermetic Sealing in Electronics

As technology evolves, the demand for advanced hermetic sealing grows, driven by miniaturization, higher power density, and the rise of wearable tech and IoT, requiring more efficient, innovative solutions.

Furthermore, the increasing use of 3D printing and additive manufacturing in electronics production is expected to change the landscape of hermetic sealing. With the ability to create intricate, customized seals, 3D printing could lead to more flexible and versatile sealing options in the future.

Conclusion

Hermetic sealing, which shields components from environmental degradation, is essential for the dependability and longevity of electronic equipment.Despite challenges like material compatibility and cost, its benefits are significant. With advancing technology, new materials and techniques offer promising solutions. Understanding hermetic sealing is essential for the success of both aerospace and consumer electronic projects.