Thermal Shock Testing As per standard IEC 60068

What is Thermal Shock?

Thermal shock occurs when a material experiences a sudden and drastic change in temperature. This phenomenon can lead to mechanical stress, causing cracking, warping, or even complete failure of the material. Thermal shock testing evaluates how well materials can resist such stress when subjected to rapid heating or cooling cycles.

IEC 60068 Standard Overview:

IEC 60068 is a widely used standard that defines various environmental tests, including those for thermal shock. The goal of these tests is to simulate real-world conditions that materials or products might encounter, ensuring their reliability and safety. Part of the standard is dedicated to thermal shock testing, where components are exposed to alternating extreme hot and cold temperatures.

Thermal Shock Testing Procedure:

According to IEC 60068, the basic procedure for thermal shock testing involves the following steps:

1. Preparation of the Specimen: The sample or product to be tested is prepared according to the specified dimensions and requirements of the standard. The material should be representative of the final product or its critical components.

2. Exposure to Extreme Temperatures:

   • The sample is subjected to a high-temperature environment for a specified duration. The exact temperature and exposure time depend on the material and the intended operating conditions.
   • Immediately after the hot phase, the specimen is transferred to a cold environment (or vice versa), ensuring no time for temperature equalization. This quick transition is critical to replicate real-world thermal shock conditions.

3. Cycles of Exposure: The number of cycles, which represents the alternation between the hot and cold environments, is determined by the test requirements. Typically, several cycles are applied to simulate prolonged exposure over the product’s lifetime.

4. Monitoring and Evaluation: During and after testing, the material is inspected for any signs of damage, such as cracking, delamination, or warping. Functional tests may also be performed to ensure the material maintains its performance despite the thermal stress.

Key Considerations in IEC 60068 Thermal Shock Testing:

• Temperature Range: The standard specifies temperature ranges that vary depending on the material or product being tested. The extremes may range from as low as -55°C to as high as 200°C, depending on the specific test requirements.

• Transition Time: A critical aspect of the thermal shock test is the rapid transition between temperature extremes. According to IEC 60068, this transition must occur within a few seconds to ensure the material experiences true thermal shock.

• Dwell Time: Dwell time refers to how long the sample remains at each extreme temperature before transitioning. This is important as insufficient dwell time may not induce enough thermal stress, while excessive dwell time could cause thermal equilibrium, reducing the shock effect.

• Cooling and Heating Methods: The standard allows for various cooling and heating methods, including air cooling, liquid baths, and forced convection ovens. The choice of method depends on the material’s properties and the desired testing conditions.

Applications of Thermal Shock Testing:

• Electronics: Circuit boards and electronic components are often tested for thermal shock to ensure they can withstand rapid temperature changes without failure.
• Aerospace: Aerospace materials are subjected to extreme temperature variations, especially during ascent and descent through the atmosphere, making thermal shock resistance crucial for these components.
• Automotive: Automotive parts, particularly those in the engine compartment, experience rapid temperature fluctuations, requiring rigorous thermal shock testing to ensure reliability.
• Construction Materials: Structural materials used in harsh environments must be tested to ensure they can withstand rapid heating and cooling cycles without losing their integrity.