Fine leak helium testing are integral to assess the integrity of your hermetically sealed device. But what happens if your device fails? How do you pinpoint the cause of the failure and fix it? There are various factors that can contribute to these failures such as leaks in the hermetic seal on the implant itself or issues with equipment and testing fixtures. In miniature devices in particular, these failures can be more difficult to identify and solve. Therefore, this article identifies what these common problems look like and methods of troubleshooting fine leak testing failures.

1. Inadequate Seal Integrity

What this looks like:

• Intermittent or consistent leaks detected during testing.
• Failure at low pressures or after thermal cycling.
• Leaks only appear under specific orientations or stress conditions.
• High failure rate from specific batches or processes.

Troubleshooting Methods:

1. Visual Inspection:
   • Use magnification or microscopy to inspect seals for cracks, voids, or misalignment.
   • Look for discoloration, foreign material, or irregularities at the joint.
2. Test Alternate Units:
   • Compare suspected leaky units with known-good parts from the same batch.
   • If all show leaks, it points to a systemic issue in the sealing process.
3. Use a Higher-Sensitivity Test:
   • Switch to helium leak detection or microbubble immersion if not already used.
   • Try pressure ramp testing or thermal cycling to expose intermittent failures.
4. Check Process Logs:
   • Review sealing parameters (temp, pressure, time) and compare against acceptable ranges.
   • Identify any deviations, machine alarms, or maintenance flags.
5. Cross-Section & Analyze:
   • Section failed units and analyze under SEM or metallography for porosity or bonding defects.
6. Run Root Cause Analysis:
   • Use a structured method like 5 Whys or Fishbone Diagram to link failures to material, method, or environment.

How to Fix It:

• Improve process control: Tighten control over sealing parameters (temperature, time, pressure).
• Clean interfaces: Ensure all parts are cleaned with appropriate solvents or plasma prior to sealing.
• Choose compatible materials: Select materials with matched thermal and mechanical properties.
• Implement pre/post-process inspection: Use dye penetrant, X-ray, or visual inspection to catch seal defects early.
• Design for robustness: Avoid sharp transitions or stress risers near seals.

2. Troubleshooting Fine Leak Testing Failures: Testing Equipment Issues

What this looks like:

• Sudden increase in detected leak rate across multiple good parts.
• Inconsistent results between tests or shifts.
• Apparent “leak” that disappears when tested on another machine.
• Baseline drift or noisy signals in helium leak detectors or pressure sensors.

Troubleshooting Methods:

1. Run a Known-Good Part:
   • Test a reference leak-free part to determine if the system is falsely indicating leaks.
2. Isolate the System:
   • Block off the fixture or test chamber and monitor for pressure drops or helium spikes.
   • If a leak is still present, it’s likely internal to the test system.
3. Check Calibration:
   • Use a calibrated leak standard or test gauge to verify instrument accuracy.
4. Inspect for Damage or Wear:
   • Examine sensors, seals, fittings, and lines for damage, wear, or contamination.
   • Pay close attention to O-rings, pump oil condition, and vacuum system connections.
5. Purge and Re-zero the System:
   • Purge residual tracer gas and re-zero the baseline before retesting.
6. Review Maintenance History:
   • Check logs for skipped maintenance, overdue sensor replacements, or recurring issues.
7. Swap Components (if possible):
   • Temporarily replace suspect sensors, valves, or modules with known-good spares.

How to Fix It:

• Routine calibration and maintenance: Establish a regular schedule with traceable standards.
• Leak check the test setup: Use a known-good leak or block to verify equipment function.
• Replace aging parts: Swap out sensors, seals, or valves on a regular preventative schedule.
• Use a reference part: Run a known leak-tight part daily to check system performance.
• Monitor environment: Avoid helium use near test stations and ensure good ventilation.

3. Troubleshooting Fine Leak Testing Failures: Fixture Problems

What this looks like:

• Leaks only during testing that don’t replicate in actual use.
• Leaks that move or vary with how the part is mounted.
• High failure rate only when a certain fixture or operator is used.
• Good parts showing leaks due to excessive force during clamping.

Troubleshooting Methods:

1. Perform a Dry Run Without Pressure:
   • Load the part without applying pressure or vacuum and check for misalignment, movement, or stress.
2. Use a Leak-Free Dummy Part:
   • Place a solid test block (non-leaking) in the fixture to see if leaks are still detected — points to fixturing or system leak.
3. Inspect the Fixture Seals:
   • Check O-rings, gaskets, and sealing surfaces for nicks, flattening, wear, or contamination.
4. Vary the Clamp Force:
   • Test with different clamping pressures. If leaks change or disappear, the part may be deforming under stress.
5. Swap Fixtures or Operators:
   • Use a different fixture or have another technician run the same test to isolate human or fixture-related variability.
6. Monitor for Repeatability:
   • Run the same part multiple times. Inconsistent results may indicate positioning, sealing, or fixture wear issues.
7. Thermal or Stress Mapping (if applicable):
   • Use strain gauges or thermal cameras to detect stress hotspots that may be opening microleaks during fixturing.

How to Fix It:

• Design ergonomic, self-aligning fixtures: Ensure consistent contact with minimal operator influence.
• Use torque-limited clamping tools: Prevent over-tightening that damages parts.
• Train operators thoroughly: Standardize procedures and reinforce best practices.
• Inspect and maintain fixturing: Replace worn components regularly; validate fixture integrity with leak-tight dummy parts.
• Add sensors or feedback: Detect improper fixturing or out-of-tolerance setups in real time.

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