In the reliability verification of microelectronic devices, temperature cycling (TC) and thermal shock (TS) are two crucial environmental stress tests. Both have simulated the performance of devices in extreme environments through temperature changes, but there are significant differences in their testing mechanisms, application scenarios, and failure modes.
1、 Differences in Testing Principles
1. Temperature cycle: cumulative effect of gradient stress
Temperature cycling simulates the slow thermal expansion and contraction process experienced by analog devices during long-term use through a gradual temperature change (usually 1-5 ℃/min). Its core purpose is to evaluate the thermal compatibility between materials (such as the difference in expansion coefficient between ceramic packaging and metal solder joints) and long-term fatigue life. For example, ceramic packaging shells may fail due to material delamination or solder joint creep under repeated temperature differences, and such failures require hundreds of cycles to be exposed.
2. Thermal shock: instantaneous failure of sudden stress changes
Thermal shock refers to the intense environmental switching experienced by analog devices in a very short period of time through extreme temperature changes (≥ 30 ℃/min), such as spacecraft suddenly entering low-temperature space from a high-temperature ground environment. It rapidly alternates between high and low temperature liquid or gas media, causing instantaneous stress concentration inside the material and directly exposing brittle fracture or interface separation defects in the packaging structure. For example, ceramic shells may fracture due to thermal stress during the alternation of liquid nitrogen (-196 ℃) and high-temperature oil bath (150 ℃), and such defects are difficult to reproduce in temperature cycling.
2、 Differences in Testing Methods
1. Characteristics of temperature cycling equipment
Single slot constant temperature box: temperature gradient is achieved through program control, supporting humidity superposition (such as 85% RH) to simulate humid and hot environments.
Key parameters: high/low temperature holding time (usually 15-60 minutes), cycle times (50-1000 times), temperature change rate (1-5 ℃/min).
2. Characteristics of thermal shock equipment
Dual bath liquid/gas bath system: The high-temperature bath (such as 150 ℃ silicone oil) and low-temperature bath (such as -65 ℃ liquid nitrogen) are independently set up, and the sample is quickly transferred by a robotic arm (conversion time ≤ 1 minute).
Key parameters: temperature change rate (≥ 30 ℃/min), maximum temperature difference (e.g. -65 ℃ to 150 ℃), cycle times (10-100 times).
3、 Comparison of Failure Modes
1. Typical failure of temperature cycling
Material fatigue: Cracks occur at the interface between ceramics and metals due to repeated expansion and contraction (such as in Al ₂ O3 packaging and copper lead frames).
Solder joint creep: Sn Ag Cu solder undergoes grain boundary slip under cyclic stress, leading to electrical connection failure.
Layering defect: Internal peeling of the package caused by CTE mismatch between epoxy resin and ceramic substrate.
2. Typical failures caused by thermal shock
Brittle fracture: The ceramic shell fractures directly due to internal stress concentration under sudden cooling and heating.
Interface delamination: Gold wire bonding points or flip chip bumps detach from the substrate due to instantaneous thermal stress.
Sealing failure: The leakage rate of airtight packaging (such as metal ceramic sealing) exceeds the standard under severe temperature differences.
4、 Choose different methods for different scenarios
1. Applicable fields of temperature cycling
In the field of consumer electronics, smartphones, wearable devices, etc. need to simulate temperature fluctuations during long-term use. In the field of automotive electronics, the engine control unit (ECU) needs to undergo 1000 cycles to verify its 10-year lifespan. In the field of industrial equipment, it is necessary to evaluate the material stability of communication base stations under -40 ℃ to 85 ℃ cycling.
2. Applicable fields of thermal shock
In the field of power modules, it is necessary to test the impact resistance of IGBT modules and other components under fast start stop conditions. In high reliability packaging scenarios, it is necessary to evaluate the crack resistance of ceramic shells in the soldering reflow process.
In summary, although temperature cycling and thermal shock belong to temperature stress testing, their application logic is completely different: temperature cycling focuses on long-term fatigue accumulation and is suitable for life prediction and material optimization; Thermal shock focuses on instantaneous ultimate stress, suitable for process defect screening and extreme environment verification.
By accurately selecting testing methods, the reliability of microelectronic devices can be significantly improved and the risk of on-site failure can be reduced. A scientific experimental matrix should be developed based on the actual working conditions of the product to provide data support for high reliability design.

This article is reprinted from the internet. If there is any infringement, please contact us to delete it. Thank you!