Thermal Shock vs Thermal Cycling Test: What’s the Difference?

Thermal shock testing and thermal cycling testing are two broad types of thermal testing.  If you want to know the difference between thermal shock and thermal cycling testing, then our guide is for you. It compares the differences between thermal shock and thermal cycle tests in detail so that you can better choose the test that is suitable for your product. This guide will teach you everything you need to know – let’s get started:

（Related Shoch Test Product: Shock Test System）

1. What is a thermal Shock Test

Thermal shock testing is an accelerated test that identifies failure modes due to rapid temperature changes. Such rapid temperature changes can be observed during the self-heating of power semiconductor devices, switching on optical devices, or during manual or wave soldering. Thermal shock testing determines whether an electronic product under test can withstand sudden temperature changes. Thermal shock testing is associated with high rates of temperature change and is the most rigorous of all temperature-related tests.

In thermal shock testing, the component or device under test is changed from one extreme temperature to another. The temperature stabilizes rapidly during this test. There are two types of thermal shock testing:

1. Air-to-air thermal shock testing – In air-to-air thermal shock testing, cyclic temperature stresses are often used, which reduces the time required to exacerbate the failure mechanism of the specimen.
2. Liquid-to-Liquid Thermal Shock Test – Transfers the device under test from one liquid at an extreme temperature to another liquid at the opposite extreme temperature. The liquid-to-liquid thermal shock test is more efficient in heat transfer and absorption than the air-to-air thermal shock test.

To transition the sample temperature from one extreme to the other, both types of thermal shock testing require hot and cold chambers.  Both air-to-air and liquid-to-liquid thermal shock test setups must be able to vary hot and cold chamber temperatures, the transition time from one chamber to the other, and the number of cycles of the thermal shock test procedure.

After the last cycle of the thermal shock test, the sample is thoroughly visually inspected for damage to the case, leads, and seals and is considered a failure if any damage is present. Conduct electrical tests on samples to detect electrical faults. Typical failure mechanisms accelerated by thermal shock testing include wire breakage, bond wire lift, flip chip bumping, chip cracking, and package cracking.

（Another Related Article: Shock vs Vibration: What’s the Difference?）

1) Examples of sources where thermal shock may occur include

• Transferring items between a temperature-controlled environment and extreme outdoor conditions
• Sudden changes when starting up a device stored outside in arctic climates
• Sudden large changes in internal power
• Ascent from hot ground environments to high altitudes

2) Purpose of thermal shock test

The engineering development stage can be used to discover product design and process defects. The product finalization or design identification and mass production stages can be used to verify the adaptability of the product to the temperature-affected environment, it can provide a basis for design finalization and mass production acceptance decisions.

When used as environmental pressure screening, the purpose is to eliminate early failures of your products.

3) Application of thermal shock

Temperature variations are common in electronic devices and components. In the absence of power, your device’s internal parts change temperature more slowly than its outer surfaces when it is not powered. Rapid temperature changes are expected under the following conditions:

• When the device is moved from a warm indoor environment to a cold outdoor environment, or vice versa
• When the device is exposed to rain or submerged in cold water to cool down suddenly
• Installed in external on-board equipment
• Under certain transport and storage conditions

When your device is powered on, there is a high-temperature gradient. Components are subject to stress due to temperature changes. For example, near a high-power resistor, radiation can cause the surface temperature of an adjacent component to rise, while the rest of the component will remain cool.

Manually cooled components experience rapid temperature changes when the cooling system is powered on. It can also cause rapid temperature changes in components during the manufacture of the device. The number and magnitude of temperature changes, as well as the time interval, are important.

4) Effect of thermal shock

Generally, thermal shock is more severe near the outer surface of the device, whereas farther away from the outer surface, it is less severe (Depending on the materials involved, of course), the slower the temperature change and the less pronounced the effect.

Shipping boxes, packaging, etc. also reduce the effects of thermal shock on enclosed equipment. Severe temperature changes may temporarily or permanently affect equipment operation. Below are some examples of issues that can arise when a device is subjected to thermal shock. Please consider the following typical questions to help determine if this experiment applies to your device

• Typical physical effects: broken glass containers and optical instruments; whether the moving parts are too tight or too loose; rupture of solid pellets or charges in explosives; different shrinkage or expansion rates of different materials, or different induced strain rates; deformation or cracking of parts; cracking of surface coatings; water leakage in the engine room; failure of insulation protection
• Typical chemical effects: separation of components; chemical agent protection failure
• Typical electrical effects: changes in electrical and electronic components; electrical or mechanical failures caused by rapid condensation or frost; excessive static electricity

This product is suitable for safety performance testing of electronic components, providing reliability testing, product screening testing, etc. Furthermore, through the equipment test, the product’s reliability and quality control can be improved. The high and low-temperature impact test chamber is an essential test equipment in the fields of aviation, automobiles, home appliances, scientific research, etc.

It is used to test and measure products such as electrical engineering, electronics, automotive electronics, materials, etc., and to test the parameters and performance changes after thermal shock in high and low-temperature environments. It is flexible and suitable for schools, factories, military industries, scientific research, etc.

Now that we’ve briefly looked at thermal shock, let’s look at a few things about thermal cycling.

（Another Related Article: What is Temperature Shock Test Chamber?）

2. What is a thermal Cycle Test

Thermal cycling tests, also known as temperature cycling tests, stress samples at extreme temperatures. Thermal cycling testing is performed to identify failure mechanisms due to material coefficient of thermal expansion (CTE) mismatches. Thermal cycling tests determine the ability of a device under test (or a portion thereof) to withstand extremely high and low temperatures. It also tests how well a sample can withstand cyclic exposure to extreme temperatures.

In a thermal cycling test, the transition from hot to cold temperature (and vice versa) is influenced by the chamber’s ability to transition between extreme temperatures and the sample’s thermal mass.  The sample is kept at a stable extreme temperature, and only after this stable period, known as the soak time, does the next transition occur.

Thermal cycling tests vary in soak time and number of cycles, exacerbating various failure modes in the component or device under test. Thermal cycling testing is commonly used to detect cracked solder joints, damaged leads or terminals, seal failures, PCB delamination, or BGA interconnect defects.

1) Examples of sources where thermal cycling can occur are

• Turn electronic equipment on and off in a controlled environment
• The daily outdoor temperature changes slowly from day to night

Soaking times vary widely between items at hot and cold temperatures. Soak times are primarily dependent on the thermal mass of the larger components within each of your products. Soaking times usually range from 15 minutes to 2 hours. Soak time also depends on whether your device was powered on during the test.

Thermal shock failures can be different than thermal cycling failures. Failures caused by thermal shock may be more of an overstress type. The failure of solder joints caused by thermal shock is often caused by tensile overstress and tensile fatigue.  Shear creep fatigue and stress relaxation are the most common causes of thermal cycling failure in solder joint components.

Thermal shock testing is usually performed in a double chamber. One compartment is for high temperatures and the other for low temperatures. Products are placed in a compartment and shuttled between hot and cold chambers within seconds, exposing test items to thermal shock. For large samples, a single chamber that can undergo rapid temperature changes is available. DES has two types of chambers.

Thermal cycling tests are performed in a single chamber, which can be a temperature-only chamber or a temperature-humidity chamber. With or without controlled humidity, most temperature and humidity chambers can perform thermal cycling. DES uses two types of single chambers for thermal cycling testing.

（Another Related Article: How to Select a Temperature Humidity Test Chamber?）

2) Purpose of thermal cycling test

Testing the resistance and adaptability of test samples when suddenly exposed to drastic temperature changes.  The experiment generally uses a rapid temperature change box or a thermal cycle box.

3) Principle of thermal cycle

A drastic temperature change is accompanied by a drastic change in heat, which leads to a drastic change in thermal deformation, which leads to a drastic change in stress. When the stress exceeds the ultimate stress, cracks or even fractures will occur. The rapid temperature test is to investigate the creep failure of components, and its strength is not as severe as the thermal shock test, so it can be used as a stress screen.

The difference between the thermal shock test and the thermal cycle test is mainly due to the different stress loading mechanisms. Thermal shock tests mainly examine failures caused by creep and fatigue damage, while thermal cycle tests mainly examine failures caused by shear fatigue.

Thermal shock testing allows the use of two-tank test rigs; thermal cycling tests are performed using single-tank test rigs. The temperature change rate in the second tank should be greater than 50°C/min. Thus, thermal cycling tests are fundamentally different from thermal shock tests in that the temperature transitions are performed at a constant rate.

Generally, a change rate exceeding 5°C/min can be considered as a rapid temperature change test. The purpose of thermal shock is to exchange high and low temperatures within a specified period. The general AIR-AIR test method requires the temperature zone switching time to be within 20S. In five minutes, the outlet temperature of the test chamber can be stabilized, and in fifteen minutes, the sample temperature can be stabilized.

（Another Related Article: Temperature and Humidity Test 101: An Ultimate Guide）

It can accurately simulate complex natural environments such as low temperature, high temperature, high temperature and high humidity, low temperature, and low humidity for your products. It is suitable for reliability testing of products in industries such as plastics, electronics, food, clothing, vehicles, metals, chemicals, and building materials.

Secondly, the thermal cycle test chamber can provide you with a high-temperature and high-humidity environment to compare the material changes of rubber and plastics and the degree of strong corrosion reduction before and after the test; it can also simulate the container environment for you to detect the fading and shrinkage of rubber and plastics under high temperature and high humidity.

This machine is specially designed for testing the heat resistance, cold resistance, and humidity resistance of various materials. Thermal shock is mainly used in furnace heat tests and heating tests in battery safety performance tests, but compared with the thermal cycle test chamber, the thermal shock test chamber has no humidity.

3. What is the difference between thermal shock and thermal cycle testing?

After research, both types of testing expose products to cycles between hot and cold temperatures. Both tests create stresses caused by thermal expansion and contraction. Components expand and contract differently in many cases. This produces cumulative fatigue damage during each cycle, which can lead to fatigue failure.

A thermal shock occurs when a device experiences rapid temperature changes exceeding 15°C per minute.  Cycling tests use a transition rate of less than 15°C/minute, typically between 1 and 10°C/minute in our experience. Time-to-failure data analysis of electronic systems, components, or products requires the collection of lifetime data.

Luckily, we can simplify the reliability testing of electronic systems or components by performing accelerated life testing. In accelerated life testing, life characteristics and failure modes are collected by forcing an electronic system, component, or device to fail faster than under normal operating conditions. Accelerated life testing is very important to ensure the reliability of the equipment under test.

（Another Related Article: Environmental Test 101: A Full Guide）

Thermal shock testing and thermal cycling testing are two types of accelerated life testing used to identify failure mechanisms caused by temperature. When comparing thermal shock testing to thermal cycling testing, there are many differences such as temperature profile, transfer time, dwell (soak) time, and application. Let’s take a look at thermal shock testing and thermal cycling testing to see how they compare and contrast.