Temperature test chambers: Interpretation of temperature and humidity industry standards 

IEC 60068-2-1 (low temperature) and IEC 60068-2-2 (high temperature) 

In the field of reliability verification of electronic products, temperature test chambers are the core equipment for simulating extreme environments, and their performance directly determines the validity of the test results.

IEC 60068-2-1 (low-temperature test) and IEC 60068-2-2 (high-temperature test), as the two basic standards of the International Electrotechnical Commission (IEC), provide a scientific framework for evaluating the temperature-resistance performance of electronic components, industrial equipment and consumer products. This paper combines the latest technical specifications with industry practice. This article combines the latest technical specifications and industry practice to analyze the key requirements of these two standards and discuss the technical support role of temperature test chambers in them. 

I. Low Temperature Test Standard (IEC 60068-2-1): From steady state to transient severe challenges 

IEC 60068-2-1 stipulates three major scenarios of low temperature test: constant low temperature storage, gradual temperature change operation and rapid temperature change impact. Temperature test chambers need to select the corresponding mode according to the test objectives: 

1. Constant low temperature test (-70℃ to +5℃): Verify the mechanical strength and sealing of materials at ultra-low temperatures, such as embrittlement of plastic shells and solidification of lubricants; 

2. Gradual temperature change test (temperature change rate ≤ 1 ℃ / min): simulate the process of equipment from room temperature environment gradually into the low-temperature working state; 

3. Rapid temperature change test (temperature change rate ≥ 3 ℃ / min): detection of solder joints, connectors under thermal stress fatigue life. 

Case practice: a car camera module to meet the -40 ℃ cold start requirements, temperature test chamber through the following process to complete the verification: Pre-cooling phase: the temperature inside the box from 25 ℃ to -40 ℃ within 30 minutes (accuracy ± 1 ℃);

Stabilization phase: maintain the low-temperature environment for 72 hours to monitor the torque decay of the lens focusing motor;

Recovery test: warming up to 25°C within 2 hours to assess fogging inside the lens glass. The test results show that the probability of fogging is reduced from 18% to 0.5% after using Viton seals instead of silicone. 

II. High Temperature Test Standard (IEC 60068-2-2): Thermal Aging and Functional Failure Tipping Points

IEC 60068-2-2 focuses on product durability in high temperature environments and its core parameters include: 

The key technical requirements of the temperature test chamber: 

Heating system: adopting nickel-chromium alloy resistance wire to ensure that the time to rise from room temperature to 200℃ is ≤45 minutes; 

Temperature uniformity control: temperature difference between any two points in the working area ≤ 2 ℃ (according to JJF 1101-2019 calibration specification); 

Thermal radiation shielding: multi-layer stainless steel insulation chamber design, reducing the interference of the box wall heat on the test sample. 

Typical failure modes: 

Component thermal degradation: after 500 hours of continuous operation at 125°C for a 5G base station power amplifier, the saturation current of GaN transistors decreased by 12%; 

Material deformation: ABS plastic housing warped by 0.3mm in an 85°C environment, resulting in poor key contact; 

Chemical property change: lithium battery electrolyte at 60 ℃ after 30 days of storage, the capacity decay rate of 8%. 

III. Evolution of temperature test chamber technology and standard adaptation 

In order to meet the upgrading requirements of IEC standards, the temperature test chamber realizes breakthroughs in the following fields: 

1. Multi-field coupling test capability 

The new equipment integrates shaker and humidity module to support “high temperature + vibration” or “low temperature + humidity” composite stress test. For example, an aerospace connector needs to be -55 ℃ ~ +125 ℃ alternating environment synchronized to withstand 10Grms vibration, the test chamber through the PID algorithm to achieve accurate synchronization of temperature change and vibration frequency. 

2.Intelligent monitoring system

The test chamber is equipped with Internet of Things based: 

Distributed temperature sensor: 15 temperature measurement points are arranged in 1m³ working area (in line with JJF 1564-2016 multi-point calibration requirements); 

AI fault prediction: train the model through historical data to warn the risk of heating tube aging or refrigerant leakage in advance. Energy efficiency and environmental protection upgrade

Adopting R-449A environmentally friendly refrigerant to replace R-404A reduces energy consumption by 15% in low-temperature working conditions; inverter compressor technology shortens the -70℃ cooling time to 25 minutes. 

IV. Common Problems and Solutions in the Implementation of Standards

Temperature overshoot phenomenon 

Problem: In the rapid temperature change test, the actual temperature in the box exceeds the set value ±5℃; 

Countermeasure: Optimize the PID parameters, increase the heat exchange area of the buffer zone, or use liquid nitrogen assisted refrigeration. 

Uniformity does not meet the standard 

Problem: the temperature difference between the upper and lower layers of the working area＞3℃; Countermeasures: improve the air duct design, use centrifugal fan instead of axial fan, and control the air speed at 0.8~1.2m/s. 

Lack of data traceability 

Problem: The temperature fluctuation curve is not recorded during the test; 

Countermeasure: Configure a number acquisition system that meets the requirements of ISO 17025, with a sampling interval of ≤1 minute and data storage of ≥10 years.