Environmental and Mechanical Reliability Testing — Can Sealed Products Really “Take It”?

1. Thermal Cycling and Thermal Shock Testing

The previous article verified whether the package is “sealed”; this one verifies whether it can “take the punishment”. Sealed products experience temperature variations in real-world use, especially in aerospace, automotive electronics and similar fields. Temperature changes generate thermal stress at the sealing interface, and long-term repetition may lead to cracking. Take Xuri’s TO5 and TO8 sensor headers for automotive electronics and the BOX-80*48-2PIN high-power laser housing as examples — only after passing thermal cycling and thermal shock testing were they approved for volume supply.

Thermal cycling test: the product alternates between -65°C and +150°C, dwelling at each extreme temperature for at least 15 min, for tens to hundreds of cycles. The sealing interface is then checked for cracks or leaks.

Thermal shock test: the temperature change is even more drastic — the product is transferred instantly from a -65°C liquid nitrogen environment to a +150°C high-temperature environment, with a transition time <10 s. This is the harshest thermal stress test.

2. Mechanical Testing: Vibration, Shock and Constant Acceleration

If temperature tests challenge thermal stress, mechanical tests challenge mechanical stress — together they cover the two major failure triggers in service. Sealed products must also withstand mechanical stress, and three types of tests simulate different working environments:

Vibration testing — simulates transportation and operational vibration, at frequencies of 20~2000 Hz and acceleration up to 20 g, lasting from several hours to tens of hours.

Mechanical shock — simulates drop or explosive impact, with acceleration up to 1500 g for 0.5 ms. The sealing interface and pins must not fracture.

Constant acceleration — simulates missile launch scenarios, with acceleration up to 30000 g sustained for 1 min. It tests the overall strength of the sealing structure.

All three test types verify the same conclusion: the sealing structure will not fail in real working environments.

[Next Article Preview] Next article: typical defects of glass-to-metal sealing and how to prevent and control them.

[Glossary]

1. Thermal Cycling: a reliability test that cycles between high and low temperatures, checking the sealing interface’s resistance to thermal fatigue

2. Thermal Shock: a reliability test with extremely rapid temperature transitions (transition time <10 s), testing resistance to thermal stress

3. Constant Acceleration: a sustained high-G acceleration test that simulates extreme conditions such as missile launch

4. g (G-force): the unit of gravitational acceleration, 1 g ≈ 9.8 m/s², used to quantify acceleration levels in mechanical testing