IEC 60068-2-14: Complete Guide to Temperature Change Testing

IEC 60068-2-14 defines the procedures for subjecting components and devices to rapid temperature changes, commonly known as thermal cycling tests. This test, identified as Test N in the IEC 60068 series, is essential for verifying the resistance of solder joints, seals, coatings, and electronic assemblies to thermal fatigue.

In this guide, we analyze the three methods required by the standard, the test conditions, the application sectors, and the FDM climatic chambers suitable for performing these tests with maximum reliability.

What is IEC 60068-2-14 and what is it used for?

Thermal cycling tests simulate the thermal stresses a component experiences during its operational life: switching on and off, day-night temperature variations, and transitions between environments with different temperatures. The goal is to identify latent defects before the product reaches the field.

Failure mechanisms this test highlights include:

• Cracks in solder joints: caused by different thermal expansion between component and PCB (CTE mismatch)
• Delamination: separation between layers of composite materials or between a chip and a substrate
• Bonding wire breakage: The thin wires that connect the die to the lead frame
• Degradation of seals and O-rings: loss of elasticity after repeated cycles
• Fractures in brittle materials: ceramics, glass, substrates

The three methods of IEC 60068-2-14

Na Method — Rapid Transfer Between Two Zones

The sample is physically transferred between two zones (or two chambers) maintained at different temperatures. The transfer time must not exceed 3 minutes; for large samples, the standard permits longer times, proportionate to the sample's thermal stabilization time.

Applications: BGA/QFP solder joint qualification, JEDEC testing (JESD22-A104), AEC-Q100 automotive qualification. This is the most stringent method because the thermal gradient on the sample is maximum.

Typical setup: two-zone chamber with automatic moving basket, or two separate chambers with a transfer system. Typical range: -55°C to +125°C or -40°C to +150°C.

Nb Method — Variation with controlled gradient

The sample remains in the same chamber and the temperature is varied with a gradient from 1 to 15 K/min. Unlike the Na method, here the thermal stress is more gradual and controllable.

Where to use: Qualification of complete assemblies, power modules, and electronic control units (ECUs). This is the most common method in laboratories because it requires only one programmable chamber.

Typical setup: FDM environmental chamber with a range of -70°C to +180°C and programmable ramps up to 15 K/min. The complete thermal profile is programmed: low temperature, ramp-up, high temperature, dwell time, ramp-down, and repeated for the required number of cycles.

Nc Method — Immersion in a fluid bath

The sample is alternately immersed in baths of hot and cold fluids (typically inert fluids such as Fluorinert). This method produces the most extreme thermal gradient because heat transfer through liquids is much more efficient than through air.

Where to use: Qualification testing for military and space components requiring extreme conditions. Less common in commercial electronics.

Typical test conditions by industry

FDM chambers for IEC 60068-2-14 tests

FDM Environment Makers offers several configurations to perform thermal cycling testing according to IEC 60068-2-14:

• C-PRO series environmental chambers: range -70°C to +180°C with programmable ramps. Ideal for the Nb method with customizable multi-step profiles.
• C-BCXPRO Series Climatic Chambers: Add humidity control for combined temperature-humidity tests. Fast ramps up to 15 K/min.
• T-PRO series Thermostatic Chambers: for cold-only or dry heat-only tests with extended range.

All FDM chambers are equipped with a programmable controller with automatic cyclic profiles, continuous data recording and the possibility of inserting pass-throughs for power and signal cables, essential for monitoring the sample during cycles.

Frequently Asked Questions about IEC 60068-2-14

What is the difference between thermal cycling and thermal shock?

Thermal shock (Na method) involves a rapid transition (within 3 minutes) between extreme temperatures. Thermal cycling (Nb method) uses controlled ramps (1-15 K/min). The shock is more severe but less representative of real-world conditions.

How many cycles does it take to qualify a component?

It depends on the industry: 200 cycles for photovoltaics (IEC 61215), 500-1000 for semiconductors (JEDEC), up to 2000 for automotive (AEC-Q100). IEC 60068-2-14 does not prescribe a fixed number: the number of cycles is defined by the product specification.

What is the recommended dwell time?

The dwell time at the extreme temperature depends on the thermal mass of the sample. The standard requires the sample to reach thermal equilibrium before starting the next ramp. In practice, this ranges from 10 minutes for small components to 30+ minutes for complex assemblies.

Reference Standards

• IEC 60068-2-14 — Environmental testing – Part 2-14: Tests – Test N: Change of temperature. Reference standard for temperature change tests (rapid gradient Na test, controlled gradient Nb test).
• IEC 60068-2-1 — Test A: Cold. Low temperature limit condition referred to in the Na/Nb profiles (typically -40 C to -65 C).
• IEC 60068-2-2 — Test B: Dry heat. High-temperature boundary condition coupled to Test N (typically +85 C to +155 C).
• IEC 60068-3-5 — Confirmation of the performance of temperature chambers. Requirements for the qualification of the usable volume of thermal chambers (9-point mapping, sensor uncertainty).
• MIL-STD-810H Method 503.7 — Temperature Shock. U.S. military method for two- or three-zone thermal shock with transfer times < 10 s.
• JESD22-A104F — Temperature Cycling. JEDEC standard for semiconductor thermal cycling (Condition B: -55/+125 C, Condition G: -40/+125 C).
• ISO 16750-4 — Road vehicles – Environmental conditions and testing for electrical and electronic equipment – ​​Part 4: Climatic loads. It implements the IEC 60068-2-14 profiles for automotive components.

Authoritative Sources

• IEC – International Electrotechnical Commission. International standards body that publishes the IEC 60068 series for climatic and environmental testing.
• JEDEC Solid State Technology Association. Publishes the JESD22 standards for semiconductor reliability testing, including temperature cycling.
• ACCREDIA – Italian Accreditation Body. Accredits laboratories that perform tests according to IEC 60068-2-14 in compliance with ISO/IEC 17025.
• ILAC – International Laboratory Accreditation Cooperation. Ensures the mutual international recognition of test reports issued by accredited laboratories.