Helium leak testing hermetically sealed electronic devices presents unique challenges in production environments. Small sealed components often require very fine leak detection to ensure long-term seal integrity and product performance. In many cases, acceptable leak rate limits fall between 10⁻⁵ and 10⁻⁸ atm·cc/sec, which makes helium the preferred tracer gas over alternative methods.
Because of these tight requirements, manufacturers rely on controlled helium introduction techniques to support accurate and repeatable testing.
Why Helium Leak Testing Hermetically Sealed Parts Is Challenging
Small sealed devices contain very limited internal volume. As a result, engineers must introduce helium carefully before leak testing.
Manufacturers can add helium during assembly, or they can introduce helium after sealing using a process known as helium bombing.
When assembly-time helium fill is impractical, helium bombing provides a reliable alternative. In this method, a bombing chamber exposes sealed parts to high-purity helium under pressure. Helium then permeates into the device, enabling downstream leak testing.
Key Terminology for Helium Leak Testing Hermetically Sealed Devices
Understanding bombing terminology helps ensure consistent results:
- Bombing Time – Duration that parts remain exposed to high-purity helium
- Bombing Pressure – Helium pressure inside the bombing chamber, typically 30–60 psig
- Dwell Time – Maximum allowable time between bombing and leak testing
- Bombing Chamber – Pressure vessel used to inject helium into sealed parts
Helium Bombing Chamber Diagram
Helium Bombing Process for Small Sealed Parts
After helium introduction, operators typically test parts using a hard-vacuum helium leak test chamber. Technicians can test parts individually or in batches, depending on throughput requirements.
However, helium leak testing hermetically sealed devices requires careful process design. Because each device contains a finite amount of helium, excessive retesting can deplete tracer gas from leaking parts. In some cases, a part with a gross leak may lose most of its helium during vacuum pump-down. As a result, the device may falsely pass the test.
To prevent this issue, engineers often:
- Implement a gross leak pre-test
- Limit retest cycles
- Optimize pump-down profiles
- Use specialized test sequences to retain helium
Optimizing Helium Bombing Parameters
Helium bombing requires precise control of process variables. Larger internal volumes demand higher bombing pressures and longer exposure times. In contrast, very small devices may saturate quickly.
Because helium permeation varies by design, manufacturers should validate bombing parameters experimentally. Engineers often run qualification tests to confirm that bombing pressure and time introduce sufficient helium for detection.
In some facilities, standardized bombing tables provide starting parameters. However, validation remains critical for product-specific optimization.
Managing Dwell Time and Helium Contamination
After bombing, operators should remove surface-absorbed helium by spraying parts with clean air or nitrogen. This step reduces background helium during testing.
Additionally, dwell time matters. If parts wait too long between bombing and testing, helium can escape through defects. Therefore, production workflows should tightly control the time between bombing and leak testing.
To further reduce background interference, facilities typically perform helium bombing in a separate area from the leak test station.
Summary: Helium Leak Testing Hermetically Sealed Devices in Production
Helium leak testing hermetically sealed small devices remains one of the most reliable methods for verifying seal integrity. However, successful testing depends on proper helium introduction, careful control of bombing parameters, and protection against helium depletion.
When engineers design the process correctly—whether using helium bombing or assembly-time fill—they achieve consistent, repeatable leak detection results that support long-term product performance.
Helium Bombing Equipment and System Design
LACO Technologies engineers custom systems to support helium leak testing hermetically sealed devices, including dedicated helium bombing chambers and integrated leak detection equipment.
Learn more about our helium bombing systems and production leak testing solutions.
